Abstract
Computer navigation has been introduced as an intraoperative guidance option as an alternative for traditional fluoroscopy because this two-dimensional (2D) imaging has limitation in orthopedic oncology surgery because of the difficulty in identifying the full geometric extent of the lesion as well as intraosseous involvement [1]. Computed tomography (CT)-based computer navigation aims to help the surgeon by increasing the spatial accuracy when performing surgery in and around the pelvis by augmenting a surgeon’s visibility. The demanding three-dimensional (3D) configuration of the sacrum and pelvic anatomy, tumor size, structural alterations due to tumor, neoadjuvant therapy, rarity (leading to a lack of experience on part of the surgeon), and the morbidity associated with sacral and pelvic resection has in the past resulted with positive surgical margins in the majority of cases, with local recurrence approaching rates of 70–80% [2–9]. This has made limb salvage, improved function, and decreased morbidity hard to attain without sacrificing surgical margins until the advent and use of computer navigation for surgical resection. Computer navigation has increased the precision and accuracy of resection allowing for preservation of sacral and pelvic structures with the intention of not compromising oncologic outcomes in terms of margins and recurrence. It has improved the visualization of the surgical field through a virtual 3D reconstruction of the surgical field allowing for precise osteotomy resection levels [4]. Only computer navigation that is based on advanced imaging can be used for tumor resections in the sacrum and pelvis. Several studies looking at computer navigation have reported advantages to using this modality in pelvic and sacral tumors [2, 10, 11]. Knowing where a resection tool ends when a surgeon is unable to protect the tumor on the other side is of great benefit. Unfortunately, all too often in tumor resection we do not have direct line of sight and the benefit of navigation is that a virtual line of sight is obtained. This chapter intends to explain computer navigation in sacral oncology surgery with respect to its developmental history and clinical use.
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References
Cho HS, et al. Joint-preserving limb salvage surgery under navigation guidance. J Surg Oncol. 2009;100(3):227–32. BACKGROUND: Recently, the navigation system has been introduced to orthopedic oncology. It can apply MRI and/or CT images to intraoperative visualization. We performed navigation-assisted limb salvage surgeries on patients with a malignant bone tumor of the metaphysis of the long bone or the iliac bone while preserving the adjacent joint. METHODS: When preoperative chemotherapy was estimated to be effective by imaging studies and the residual remaining epiphysis was expected to be more than 1 cm long after tumor resection with 1-2 cm of surgical margin, joint-preserving surgery was performed under navigation guidance. We carried out CT and MRI data fusion to use MR images as an intraoperative guide. A deep frozen strut allograft was placed in the defect for the restoration of anatomical continuity. RESULTS: Resection margin measured on pathological examination was in accordance with that of the preoperative plan. The functional scores of all patients were satisfactory. There was no evidence of recurrence on the regional radiographs and CT on the chest until the last follow-up. CONCLUSION: Navigation-assisted surgery can be indicated for limb salvage and it can help to preserve the adjacent joint in selected cases.
Cho HS, et al. Computer-assisted sacral tumor resection. A case report. J Bone Joint Surg Am. 2008;90(7):1561–6.
Court C, et al. Surgical excision of bone sarcomas involving the sacroiliac joint. Clin Orthop Relat Res. 2006;451:189–94. Adequate (wide or marginal and uncontaminated) margins and reconstruction are difficult to achieve when performing an internal hemipelvectomy for bone sarcomas involving the sacroiliac joint. We evaluated whether adequate surgical margins could be achieved and if functional outcomes could be predicted based on the type of resection and reconstruction. Forty patients had resections of the sacroiliac joint. Vertical sacral osteotomies were through the sacral wing (n = 2), ipsilateral sacral foramina (n = 27), sacral midline (n = 9), or contralateral foramina (n = 2). Iliac resections were Type I, Type I-II with partial or total acetabular re-section, or Type I-II-III. Surgical margins were adequate in 28 of 38 patients (74%), two (7%) of whom experienced local recurrence, compared with seven of 10 (70%) patients with inadequate margins. Reconstruction consisted of restoring continuity between the spine and pelvis. Resection of the entire acetabulum and removal of the lumbosacral trunk were the two main determinants of function, as assessed using the Musculoskeletal Tumor Society score. There were no life-threatening or function-threatening complications. Internal hemipelvectomy with a limb salvage procedure can be achieved with adequate surgical margins in selected patients. Functional outcomes can be predicted based on the type of resection and reconstruction, which helps the surgeon plan the procedure and inform the patient.
Fehlberg S, et al. Computer-assisted pelvic tumor resection: fields of application, limits, and perspectives. Recent Results Cancer Res. 2009;179:169–82. The treatment of malignant tumors involving the pelvic area is a challenging problem in musculoskeletal oncology due to the complex pelvic anatomy and the often large tumor size at presentation. The use of navigation systems has effectively increased surgical precision aiming at optimal preservation of pelvic structures without compromising oncologic outcome by means of improved visibility of the surgical field, and enabling intraoperative display and 3D reproduction of preoperatively determined pelvic osteotomy and resection levels. In the following sections, current developments in computer-assisted pelvic surgery are reviewed and possible fields of application, as well as limitations of navigation systems, are discussed.
Fuchs B, et al. Osteosarcoma of the pelvis: outcome analysis of surgical treatment. Clin Orthop Relat Res. 2009;467(2):510–8. Risk factors to explain the poor survival of patients with osteosarcoma of the pelvis are poorly understood. Therefore, we attempted to identify factors affecting survival and development of local recurrence and metastasis. We retrospectively reviewed 43 patients who had high-grade pelvic tumors and were treated surgically. Twenty lesions were chondroblastic, 10 fibroblastic, 11 osteoblastic, and one each was giant cell-rich and small cell osteosarcomas. At a median of 3.5 years (range, 0.3-21 years) postoperatively, 13 patients were alive with no evidence of disease. The overall and disease-free 5-year survival rates were 38% and 29%, respectively, at 5 years. Anatomic location, tumor size, and margin predicted survival. Fifteen patients (35%) had local recurrence. The 5-year cumulative incidence of recurrence with death as a competing risk factor was 34%. Location in the ilium and size of the tumor predicted local recurrence. Twenty-one (49%) of 43 patients had metastases develop. The cumulative incidence of metastasis with death as a competing risk factor was 48% at 5 years. Six patients who presented with metastasis had a worse survival than patients who had no evidence of metastasis at presentation (2-year survival, 33% versus 76%). If distant metastasis is diagnosed subsequent to primary treatment, aggressive therapy may be justified. LEVEL OF EVIDENCE: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.
Kawai A, et al. Osteosarcoma of the pelvis. Oncologic results of 40 patients. Clin Orthop Relat Res. 1998;(348):196–207. The cases of 40 patients with osteosarcoma of the pelvis treated between 1977 and 1994 were reviewed. The location of the tumor was ilium in 30 patients, ischium in four, pubis in one, and sacrum in five. Most (58%) of the tumors were of the chondroblastic subtype. Thirty patients had surgical excision of the tumors: 10 with hemipelvectomies and 20 with limb sparing procedures. A wide margin was achieved in 16 of 30 (53%) patients, including 12 of 14 who had no sacral tumor involvement. Positive margins occurred at the sacrum in 11 patients, lumbar vertebra in one, perirectal space in one, and contralateral pubic body in one. Macroscopic tumor emboli within the regional large vessels were found in seven patients. The incidence of local recurrence was 32%: 13% in wide excisions, 38% in marginal excisions, and 80% in intralesional excisions. The 1- and 5-year overall patient survivals were 73% and 34%, respectively. Patients who had a surgical excision of the primary tumor had a significantly better survival than did those treated without surgery (5-year survival; 41% and 10%, respectively). Tumor size, surgical excision of the primary tumor, surgical margin, and type of surgical procedure were the prognostic factors for patients with Stage IIB tumors.
Pring ME, et al. Chondrosarcoma of the pelvis. A review of sixty-four cases. J Bone Joint Surg Am. 2001;83-A(11):1630–42. BACKGROUND: Treatment of pelvic chondrosarcoma is a difficult problem for the musculoskeletal oncologist. Poor rates of survival and high rates of local recurrence after surgical treatment have been reported in previous studies. The present study was designed to review the long-term oncologic and functional outcomes of surgical management in a large series of patients with pelvic chondrosarcoma who were treated at a single institution. METHODS: The cases of sixty-four patients with localized pelvic chondrosarcoma that had been surgically treated between 1975 and 1996 were reviewed retrospectively. The study was limited to patients who had received no previous treatment for chondrosarcoma. There were forty-one male and twenty-three female patients who had a mean age of forty-seven years (range, fifteen to eighty-eight years). The patients were followed for a minimum of three years or until death. The median duration of follow-up of the living patients was 140 months (range, thirty-nine to 295 months). RESULTS: Thirty-three of the sixty-four patients were first seen with grade-1 chondrosarcoma; twenty-three, with grade-2; one, with grade-3; and seven, with grade-4 (dedifferentiated chondrosarcoma). Thirteen patients had a hemipelvectomy to achieve local tumor control, whereas fifty-one patients underwent a limb-salvage procedure. Twelve patients (19%) had local recurrence, and eleven (17%) had distant metastases. At the time of the final follow-up, forty-four patients (69%) were alive without evidence of disease, thirteen (20%) had died of the disease, six (9%) had died of unrelated causes, and one (2%) was alive with disease. Less than a wide surgical margin correlated with local recurrence (p = 0.014). High-grade tumors correlated with poor overall survival (p < 0.001). All patients who had a limb-salvage procedure were able to walk at the time of the final follow-up, and they had a mean functional score of 77%, according to the system of the Musculoskeletal Tumor Society. CONCLUSIONS: Aggressive surgical resection of pelvic chondrosarcoma results in long-term survival of the majority of patients. There is a high correlation between tumor grade and overall or disease-free survival.
Sucato DJ, et al. Ewing’s sarcoma of the pelvis. Long-term survival and functional outcome. Clin Orthop Relat Res. 2000;(373):193–201. Fifty patients with Ewing,s sarcoma of the pelvis were treated using a multidisciplinary approach; followup of surviving patients averaged 137 months (range, 40-276 months). The addition of surgical resection to the multidisciplinary treatment for all patients was associated with improved survival compared with survival of patients treated with chemotherapy and radiation therapy alone; the addition of surgery to the treatment regimen of 37 patients without metastases also was associated with improved survival. There were no significant differences between the surgical and nonsurgical groups in terms of tumor size, stage of disease, patient age, duration of symptoms before diagnosis, or anatomic site. Surgery was used more often in recently treated patients, but the year of diagnosis and treatment did not significantly affect overall survival, secondary to large confidence intervals. The Short Form-36 and the Musculoskeletal Tumor Society functional evaluation instruments showed a superior level of function in the nonsurgical group, but this difference was not statistically significant. There have been many advances in the treatment of patients with Ewing’s sarcoma during the past 3 decades, resulting in improved survival for patients with Ewing’s sarcoma of the pelvis. The addition of surgery significantly improved survival and did not show a significant difference in functional outcome.
Wirbel RJ, et al. Surgical treatment of pelvic sarcomas: oncologic and functional outcome. Clin Orthop Relat Res. 2001;(390):190–205. The experiences in treating 93 consecutive patients (56 males, 37 females; mean age, 38.5 years; range, 4-69 years), including 76 patients with primary malignant bone tumors and 17 patients with soft tissue sarcomas involving the innominate bone, are reported. Oncologic and functional results were investigated in relation to the tumor stage, to the achieved surgical margin, and to the surgical procedure (hemipelvectomy, internal hemipelvectomy and endoprosthetic replacement, and continuity resection). The mean followup was 48 months (range, 8-222 months). The 5-year survival was 86% in patients with low-grade malignant bone tumors, 42% in patients with high-grade malignant bone tumors, and 25% in patients with high-grade soft tissue sarcomas. Survival was influenced by the grade of malignancy, the tumor stage, and the achieved surgical margins. Forty-six patients who survived were examined an average of 36 months after primary surgery. Excellent and good functional results were seen in 82% of patients who underwent continuity resection and in 55.5% of patients who underwent partial or total internal hemipelvectomy. All patients who survived hemipelvectomy had poor functional results. Surgical treatment of pelvic sarcomas is an extensive procedure with a considerable incidence of complications. It requires the knowledge of different techniques of resection and reconstruction of bone, joints, soft tissue, and intrapelvic organs.
Krettek C, et al. Computer aided tumor resection in the pelvis. Injury. 2004;35 Suppl 1:S-A79-83. Surgical treatment of malignant tumors within the pelvis is a complex problem due to the anatomy and biomechanics. There are standardized preoperative diagnostic tools like computed tomography (CT) or magnetic resonance imaging (MRI) that provide multidimensional information. However, this information cannot be transferred intraoperatively. Computer aided orthopedic surgery (CAOS) may be a solution for precise intraoperative accuracy for these indications. We report on two patients with tumors within the pelvis. In one patient, an infiltrating recurrent chordoma within the sacrum was resected with CAOS. The other patient presented with a periacetabular chondrosarcoma. Resection was done with navigation so precise that a custom-made hemipelvis prosthesis with a special coating fit. In both patients, a complete resection was achieved with tumor-free resection margins. Navigation may be helpful in tumor surgery within the pelvis.
Wong KC, et al. Image fusion for computer-assisted bone tumor surgery. Clin Orthop Relat Res. 2008;466(10):2533–41. The fusion of computed tomography and magnetic resonance images is a software-dependent processing technique that enables one to integrate and analyze preoperative images for planning complex musculoskeletal tumor resections. By integrating various imaging modalities into one imaging data set we may facilitate preoperative image analysis and planning of navigation computer-assisted bone tumor resection and reconstruction. We performed image fusion for computer-assisted tumor surgery in 13 consecutive patients, seven males and six females, with a mean age of 35.8 years (range, 6-80 years). Visual verification of fused images was accurate in all patients. The mean time for image fusion was 30.6 minutes (range, 8-80 minutes). After intraoperative registration, all tumor resections were performed as planned preoperatively under navigation image guidance. Resections achieved after navigation resection planning were validated by postoperative CT or resected specimens in seven patients. Histologic examination of all resected specimens showed tumor-free margins in patients with bone sarcoma. The fusion of computed tomography and magnetic resonance imaging has the potential to enhance computer-assisted bone tumor surgery. The fusion image, when combined with surgical navigation, helps surgeons reproduce a preoperative plan reliably and may offer substantial clinical benefits.
Schlondorff G. Computer-assisted surgery: historical remarks. Comput Aided Surg. 1998;3(4):150–2.
Stiehl JB, Heck DA. Computer-assisted surgery: basic concepts. Instr Course Lect. 2008;57:689–97. Computer-assisted surgery has been advocated as a significant enabling technology that will enhance the surgical technique of various orthopaedic procedures. The computer becomes a sophisticated measuring tool, determining the three-dimensional spatial orientation of fiducial points, which may be established by a variety of referencing methods. These fiducial points or arrays may define a bone, an instrument, or a prosthesis. Current referencing methods include using segmented computer tomograms; fluoroscopic images; ultrasound images; and imageless, direct anatomic point-picking methods. Tracking technologies use optical cameras and electromagnetic coils. Optical systems have high reliability with errors of less than 0.5 mm. Electromagnetic trackers have a similar capability, but are less reliable because of the distortion of the electromagnetic signal that may result from the complex operating room environment. Accuracy with current CT-referenced systems approximates 1 degrees or 1 mm. Other methods such as fluoroscopy or ultrasound are less precise because of difficulty related to the ability to consistently define a specific anatomic structure. Descriptive measures of outcome include standard deviation and quantification of error. Process capability indices or Six Sigma are suitable methods for comparing outcomes with computer-assisted surgery and can be generalized from various approaches.
Amiot LP, et al. Computer-assisted pedicle screw fixation. A feasibility study. Spine (Phila Pa 1976). 1995;20(10):1208–12. STUDY DESIGN: We evaluated a computer-assisted surgical tool for inserting pedicle screws. OBJECTIVES: This study reviewed the feasibility, usefulness, and accuracy of the proposed tool. SUMMARY OF BACKGROUND DATA: Reviews documented neurovascular damage caused by screw misplacement. Currently, screw hole position is assessed by radiologic means and curette palpation. METHODS: Three sheep vertebrae and one artificial object were reconstructed three-dimensionally from computed tomography scan slices. At surgery, the surgeon’s movements were displayed relative to the three-dimensional vertebrae on a computer screen. The tool was used to detect pedicles and to verify the position of drilled holes. In our laboratory, we calculated the system’s accuracy by taking measurements on the artificial object. RESULTS: All pedicles were identified with the computer. Five of the six drilled hole positions were correctly represented. An accuracy of 4.5 mm +/- 1.1 mm RMS (root of the mean squared) and 1.6 degrees +/- 1.2 degrees were calculated. CONCLUSIONS: Results suggested the proposed system could be useful for pedicle detection and assessing the intravertebral location of a drilled hole. The proposed system could be used for many different orthopedic procedures where structures are hidden from the surgeon’s view.
Dessenne V, et al. Computer-assisted knee anterior cruciate ligament reconstruction: first clinical tests. J Image Guid Surg. 1995;1(1):59–64. Anterior cruciate ligament reconstruction is a delicate task. The procedure of choice is the patellar tendon bone autograft, but an anisometric position of this tendon often leads to failure. We allows positioning of the central part of the ligament graft at the least anisometric sites. The system uses a workstation and a three-dimensional optical localizer to create images that represent knee kinematics. The surgeon uses these images to guide the surgery. This technique has been validated on eight cadavers and 12 patients.
Amiot LP, et al. Comparative results between conventional and computer-assisted pedicle screw installation in the thoracic, lumbar, and sacral spine. Spine (Phila Pa 1976). 2000;25(5):606–14. STUDY DESIGN: A comparative study on the position of pedicle screws in patients treated surgically with and without computer assistance. OBJECTIVES: To evaluate the accuracy of computer-assisted pedicle screw installation, and to evaluate its clinical benefit as compared with conventional pedicle screw installation techniques. SUMMARY OF BACKGROUND DATA: In vitro and clinical studies have documented a significant rate of misplaced screws in the thoracolumbar area. Neurologic complications are recognized problems caused by screw misplacement. METHODS: Patients treated surgically with computer assistance were compared with a historical control group of patients treated surgically with conventional techniques in the same hospital and by the same surgical team. All screw positions were measured with a postoperative magnetic resonance tomography, and cortical effractions were categorized in 2-mm increments. Patients’ charts also were reviewed to assess individual neurologic outcomes. RESULTS: The control cohort was composed of 100 patients, with 544 screws from T5 to S1. The computer-assisted cohort was composed of 50 patients, with 294 screws from T2 to S1. In the control cohort, 461 of 544 screws (85%) were found completely within their pedicles as compared with 278 of 294 screws (95%) correctly placed in the computer-assisted group (P < 0.0001). All 16 screws incorrectly placed with computer assistance were found 0.1 mm to 2 mm from the pedicle cortex. In the control cohort, 68 screws were found 0.1 mm to 2 mm, 10 screws 2.1 mm to 4 mm, and 5 screws more than 4 mm from the pedicle cortex. Seven patients in the control cohort were surgically retreated because of postoperative neurologic deficits, whereas no patients in the computer-assisted group were surgically retreated. CONCLUSIONS: Computer assistance can decrease the incidence of incorrectly positioned pedicle screws.
Castro WH, et al. Accuracy of pedicle screw placement in lumbar vertebrae. Spine (Phila Pa 1976). 1996;21(11):1320–4. STUDY DESIGN: The location of pedicle screws (n = 42) in four human specimens of the lumbar spine and in 30 patients (n = 131 screws) after lumbar spinal fusion was assessed using computed tomography. OBJECTIVES: To determine the accuracy of pedicle screw placement in lumbar vertebrae and the reproducibility and repeatability of the computed tomography examination. SUMMARY OF BACKGROUND DATA: Failures in the placement of transpedicular screws for lumbar fusion are reported. The evaluation of such screws using computed tomography examination has not been investigated. METHODS: After surgery, the specimens were dissected in transversal slices to observe macroscopically the location of the pedicle screw and to correlate these observations with the computed tomography images. All patients were examined by one observer. To determine the reproducibility and repeatability of the computed tomography examination, two observers studied computed tomography images of 12 patients (n = 58 screws) twice within 3 months. RESULTS: In the specimens, 10 screws were observed to penetrate the medial wall of the pedicle. This correlated fully with the images. In the patients’ group, 40% of all screws penetrated the cortex of the vertebra. Of all screws, 29% penetrated the medial wall of the pedicle. From the computed tomography images, it appeared that a deviation of more than 6 mm medially was a high risk for nerve root damage. Three months after his first examination, Observer 1 documented a different position in three of 58 screws (kappa = 0.90). Observer 2 found a different position in eight screws (kappa = 0.65). The comparison between the reviews of the two observers showed a different opinion for the first evaluation, four disagreements (2-4 mm) and 17 disagreements (0-2 mm; kappa = 0.34), and for the second evaluation, four disagreements (2-4 mm) and 12 disagreements (0-2 mm; kappa = 0.43). CONCLUSIONS: Correct placement of transpedicular screws for spinal fusion seems to be more difficult than it looks. The computed tomography scanning is useful for differential diagnosis of postoperative radicular syndromes after lumbar transpedicular fixation.
Hufner T, et al. Computer-assisted fracture reduction of pelvic ring fractures: an in vitro study. Clin Orthop Relat Res. 2002;(399):231–9. A newly developed software module for computer-assisted surgery based on a commercially available navigation system allows simultaneous, independent registration of two fragments and real-time navigation of both fragments while reduction occurs. To evaluate the accuracy three fracture models were used: geometric foam blocks, a pelvic ring injury with disruption of the symphysis and the sacroiliac joint, and a pelvic ring fracture with symphysis disruption and a transforaminal sacral fracture. One examiner did visual and navigated reduction and in all experiments the end point was defined as anatomic reduction. Residual displacement was measured with a magnetic motion tracking device. The results revealed a significantly increased residual displacement with navigated reduction compared with visual control. The differences were low, averaging 1 mm for residual translation and 0.7 degrees for the residual rotation, respectively. Residual displacement was small in both set-ups and may not be clinically relevant. Additional development of the software prototype with integration of surface registration may lead to improved handling and facilitated multifragment tracking. Use in the clinical setting should be possible within a short time.
Langlotz F, et al. The first twelve cases of computer assisted periacetabular osteotomy. Comput Aided Surg. 1997;2(6):317–26. Image guided freehand navigation of surgical instruments has been applied to the Bernese periacetabular osteotomy, a complex surgical technique for the treatment of dysplastic hips. This navigation system has been introduced into the operating room and has so far been used for 12 patients. Image data from computed tomography (CT) scans are presented in various ways to support the preoperative plan and to provide optimized control of surgical action. Special attention has been paid to the implementation of a sophisticated surgeon-machine interface. This paper describes the features of this novel surgical navigation system and its introduction into the clinical environment.
Hufner T, et al. New indications for computer-assisted surgery: tumor resection in the pelvis. Clin Orthop Relat Res. 2004;(426):219–25. The resection of recurrent malignant pelvic tumors was supported by a commercially available navigation system in three patients. Preoperatively three-dimensional images from the pelvis were obtained by computed tomography or magnetic resonance imaging to identify the tumor extension. During surgery navigated tools oriented the surgeon to excise the tumor with adequate virtual margins. Navigation was helpful for tumor identification in one patient with a recurrent presacral mesenchymal chondrosarcoma. In the other two patients the tumor resection in the bone was done with three-dimensional observation of the osteotomies in the sacrum. In all three patients the histopathologic analysis confirmed that the neoplasms were excised accurately within their margins. We think that computer-assisted surgery is a potential method to increase the accuracy of tumor resections.
Cheong D, Letson GD. Computer-assisted navigation and musculoskeletal sarcoma surgery. Cancer Control. 2011;18(3):171–6. BACKGROUND: Despite advances in medical, surgical, and radiation oncology, deep-seated bone sarcomas that require large osseous resections continue to present resection and reconstructive challenges to musculoskeletal surgeons. METHODS: We describe our experience with computer navigation techniques combined with complex pelvic resections and limb-preserving surgeries. RESULTS: Computer-assisted navigation has shown promise in aiding in optimal preoperative planning and in providing more accurate and precise feedback during surgery. CONCLUSIONS: Computer-assisted navigation offers precise instrumentation, technology-oriented imaging systems, and powerful information processing, all of which can assist in decision making, preoperative planning, and surgical accuracy.
Jeys L, et al. Can computer navigation-assisted surgery reduce the risk of an intralesional margin and reduce the rate of local recurrence in patients with a tumour of the pelvis or sacrum? Bone Joint J. 2013;95-B(10):1417–24. We hypothesised that the use of computer navigation-assisted surgery for pelvic and sacral tumours would reduce the risk of an intralesional margin. We reviewed 31 patients (18 men and 13 women) with a mean age of 52.9 years (13.5 to 77.2) in whom computer navigation-assisted surgery had been carried out for a bone tumour of the pelvis or sacrum. There were 23 primary malignant bone tumours, four metastatic tumours and four locally advanced primary tumours of the rectum. The registration error when using computer navigation was < 1 mm in each case. There were no complications related to the navigation, which allowed the preservation of sacral nerve roots (n = 13), resection of otherwise inoperable disease (n = 4) and the avoidance of hindquarter amputation (n = 3). The intralesional resection rate for primary tumours of the pelvis and sacrum was 8.7% (n = 2): clear bone resection margins were achieved in all cases. At a mean follow-up of 13.1 months (3 to 34) three patients (13%) had developed a local recurrence. The mean time alive from diagnosis was 16.8 months (4 to 48). Computer navigation-assisted surgery is safe and has reduced our intralesional resection rate for primary tumours of the pelvis and sacrum. We recommend this technique as being worthy of further consideration for this group of patients.
Reijnders K, et al. Image guided surgery: new technology for surgery of soft tissue and bone sarcomas. Eur J Surg Oncol. 2007;33(3):390–8. AIM: Providing the surgical oncologist with a new means of performing safe and radical sarcoma surgery with the help of image guidance technology. METHOD: Two patients with pelvic sarcomas were operated upon with the help of an intra-operative navigation system. The technology of image guided surgery is described in one patient with a retroperitoneal sarcoma invading the bony pelvis and another patient with a chondrosarcoma of the iliac crest. RESULTS: We show that this new procedure enables optimal radical surgical resection with minimal treatment related morbidity or loss of function. CONCLUSION: Image guided surgery is a new technical tool in sarcoma surgery.
So TY, et al. Computer-assisted navigation in bone tumor surgery: seamless workflow model and evolution of technique. Clin Orthop Relat Res. 2010;468(11):2985–91. BACKGROUND: Computer-assisted navigation was recently introduced to aid the resection of musculoskeletal tumors. However, it has not always been possible to directly navigate the osteotomy with real-time manipulation of available surgical tools. Registration techniques vary, although most existing systems use some form of surface matching. QUESTIONS/PURPOSES: We developed and evaluated a workflow model of computer-assisted bone tumor surgery and evaluated (1) the applicability of currently available software to different bones; (2) the accuracy of the navigated excision; and (3) the accuracy of a new registration technique of fluoro-CT matching. METHODS: Our workflow involved detailed preoperative planning with CT-MRI image fusion, three-dimensional mapping of the tumor, and planning of the resection plane. Using the workflow model, we reviewed 15 navigation procedures in 12 patients, including four with joint-saving resections and three with custom implant reconstructions. Intraoperatively, registration was performed with either paired points and surface matching (Group 1, n = 10) or a new technique of fluoro-CT image matching (Group 2, n = 5). All osteotomies were performed under direct computer navigation. Postoperatively, each case was evaluated for histologic margin and gross measurement of the achieved surgical margin. RESULTS: The margins were free from tumor in all resected specimens. In the Group 1 procedures, the correlation between preoperative planned margins and actual achieved margins was 0.631, whereas in Group 2 procedures (fluoro-CT matching), the correlation was 0.985. CONCLUSIONS: Our findings suggest computer-assisted navigation is accurate and useful for bone tumor surgery. The new registration technique using fluoro-CT matching may allow more accurate resection of margins.
Wong KC, et al. Precision tumour resection and reconstruction using image-guided computer navigation. J Bone Joint Surg Br. 2007;89(7):943–7. The use of a navigation system in musculoskeletal tumour surgery enables the integration of pre-operative CT and MRI images to generate a precise three-dimensional anatomical model of the site and the extent of the tumour. We carried out six consecutive resections of musculoskeletal tumour in five patients using an existing commercial computer navigation system. There were three women and two men with a mean age of 41 years (24 to 47). Reconstruction was performed using a tumour prosthesis in three lesions and a vascularised fibular graft in one. No reconstruction was needed in two cases. The mean follow-up was 6.9 months (3.5 to 10). The mean duration of surgery was 28 minutes (13 to 50). Examination of the resected specimens showed clear margins in all the tumour lesions and a resection that was exactly as planned.
Wong KC, et al. Computer assisted pelvic tumor resection and reconstruction with a custom-made prosthesis using an innovative adaptation and its validation. Comput Aided Surg. 2007;12(4):225–32. Computer aided musculoskeletal tumor surgery is a novel concept. Ideally, computer navigation enables the integration of preoperative information concerning tumor extent and regional anatomy to facilitate execution of a surgical resection. Accurate resection helps oncological clearance and facilitates precise fitting of a custom prosthesis. We adapted a commercially available computer navigation platform for spine, and used it to plan and execute pelvic bone resection and custom pelvic prosthetic reconstruction in a patient with a metastatic tumor affecting the acetabulum. The surgery was simulated and validated using a plaster bone model based on the patient’s preoperative CT data, before performing the procedure on the patient.
Wu K, et al. Intraoperative navigation for minimally invasive resection of periarticular and pelvic tumors. Orthopedics. 2011;34(5):372. The surgical approach to benign, metastatic, and some low-grade malignant tumors is often difficult due to their typically precarious locations. This article presents a series of cases where intraoperative stealth navigation was used to treat periarticular tumors. The use of paired point imaging with image fusion has made approaching tumors through an accurate and minimally invasive technique a viable option for the treatment of a subset of musculoskeletal tumors.
Young PS, et al. The evolving role of computer-assisted navigation in musculoskeletal oncology. Bone Joint J. 2015;97-B(2):258–64. We report our experience of using a computer navigation system to aid resection of malignant musculoskeletal tumours of the pelvis and limbs and, where appropriate, their subsequent reconstruction. We also highlight circumstances in which navigation should be used with caution. We resected a musculoskeletal tumour from 18 patients (15 male, three female, mean age of 30 years (13 to 75) using commercially available computer navigation software (Orthomap 3D) and assessed its impact on the accuracy of our surgery. Of nine pelvic tumours, three had a biological reconstruction with extracorporeal irradiation, four underwent endoprosthetic replacement (EPR) and two required no bony reconstruction. There were eight tumours of the bones of the limbs. Four diaphyseal tumours underwent biological reconstruction. Two patients with a sarcoma of the proximal femur and two with a sarcoma of the proximal humerus underwent extra-articular resection and, where appropriate, EPR. One soft-tissue sarcoma of the adductor compartment which involved the femur was resected and reconstructed using an EPR. Computer navigation was used to aid reconstruction in eight patients. Histological examination of the resected specimens revealed tumour-free margins in all patients. Post-operative radiographs and CT showed that the resection and reconstruction had been carried out as planned in all patients where navigation was used. In two patients, computer navigation had to be abandoned and the operation was completed under CT and radiological control. The use of computer navigation in musculoskeletal oncology allows accurate identification of the local anatomy and can define the extent of the tumour and proposed resection margins. Furthermore, it helps in reconstruction of limb length, rotation and overall alignment after resection of an appendicular tumour.
Ozaki T, et al. Osteosarcoma of the pelvis: experience of the Cooperative Osteosarcoma Study Group. J Clin Oncol. 2003;21(2):334–41. PURPOSE: To define patients and tumor characteristics as well as therapy results, patients with pelvic osteosarcoma who were registered in the Cooperative Osteosarcoma Study Group (COSS) were analyzed. PATIENTS AND METHODS: Sixty-seven patients with a high-grade pelvic osteosarcoma were eligible for this analysis. Fifteen patients had primary metastases. All patients received chemotherapy according to COSS protocols. Thirty-eight patients underwent limb-sparing surgery, 12 patients underwent hemipelvectomy, and 17 patients did not undergo definitive surgery. Eleven patients received irradiation to the primary tumor site: four postoperatively and seven as the only form of local therapy. RESULTS: Local failure occurred in 47 of all 67 patients (70%) and in 31 of 50 patients (62%) who underwent definitive surgery. Five-year overall survival (OS) and progression-free survival rates were 27% and 19%, respectively. Large tumor size (P =.0137), primary metastases (P =.0001), and no or intralesional surgery (P <.0001) were poor prognostic factors. In 30 patients with no or intralesional surgery, 11 patients with radiotherapy had better OS than 19 patients without radiotherapy (P =.0033). Among the variables, primary metastasis, large tumor, no or intralesional surgery, no radiotherapy, existence of primary metastasis (relative risk [RR] = 3.456; P =.0009), surgical margin (intralesional or no surgical excision; RR = 5.619; P <.0001), and no radiotherapy (RR = 4.196; P =.0059) were independent poor prognostic factors. CONCLUSION: An operative approach with wide or marginal margins improves local control and OS. If the surgical margin is intralesional or excision is impossible, additional radiotherapy has a positive influence on prognosis.
Cartiaux O, et al. Surgical inaccuracy of tumor resection and reconstruction within the pelvis: an experimental study. Acta Orthop. 2008;79(5):695–702. BACKGROUND AND PURPOSE: Osseous pelvic tumors can be resected and reconstructed using massive bone allografts. Geometric accuracy of the conventional surgical procedure has not yet been documented. The aim of this experimental study was mainly to assess accuracy of tumoral resection with a 10-mm surgical margin, and also to evaluate the geometry of the host-graft reconstruction. METHODS: An experimental model on plastic pelvises was designed to simulate tumor resection and reconstruction. 4 experienced surgeons were asked to resect 3 different tumors and to reconstruct pelvises. 24 resections and host-graft junctions were available for evaluation. Resection margins were measured. Several methods were created to evaluate geometric properties of the host-graft junction. RESULTS: The probability of a surgeon obtaining a 10-mm surgical margin with a 5-mm tolerance above or below, was 52% (95% CI: 37-67). Maximal gap, gap volume, and mean gap between host and graft was 3.3 (SD 1.9) mm, 2.7 (SD 2.1) cm3 and 3.2 (SD 2.1) mm, respectively. Correlation between these 3 reconstruction measures and the degree of contact at the host-graft junction was poor. INTERPRETATION: 4 experienced surgeons did not manage to consistently respect a fixed surgical margin under ideal working conditions. The complex 3-dimensional architecture of the pelvis would mainly explain this inaccuracy. Solutions to this might be to increase the surgical margin or to use computer- and robotic-assisted technologies in pelvic tumor resection. Furthermore, our attempt to evaluate geometry of the pelvic reconstruction using simple parameters was not satisfactory. We believe that there is a need to define new standards of evaluation.
Docquier PL, et al. Computer-assisted resection and reconstruction of pelvic tumor sarcoma. Sarcoma. 2010;2010:125162. Pelvic sarcoma is associated with a relatively poor prognosis, due to the difficulty in obtaining an adequate surgical margin given the complex pelvic anatomy. Magnetic resonance imaging and computerized tomography allow valuable surgical resection planning, but intraoperative localization remains hazardous. Surgical navigation systems could be of great benefit in surgical oncology, especially in difficult tumor location; however, no commercial surgical oncology software is currently available. A customized navigation software was developed and used to perform a synovial sarcoma resection and allograft reconstruction. The software permitted preoperative planning with defined target planes and intraoperative navigation with a free-hand saw blade. The allograft was cut according to the same planes. Histological examination revealed tumor-free resection margins. Allograft fitting to the pelvis of the patient was excellent and allowed stable osteosynthesis. We believe this to be the first case of combined computer-assisted tumor resection and reconstruction with an allograft.
Kojima T, et al. The usefulness and limits of magnetic resonance imaging in the differential diagnosis of pelvic tumors. Oncol Rep. 2001;8(4):867–9. Three cases of benign pelvic tumors are presented (2 leiomyomas and 1 fibroma). All three tumors were suspected of being malignant neoplasms because they were visualized as heterogeneous high signal intensity on T2-weighted images, and thus they were difficult to diagnose preoperatively. One of the leiomyomas was located in the retroperitoneum and had been misdiagnosed as an ovarian tumor. All three tumors exhibited secondary myxoid changes, these changes may have been responsible for the high signal intensity on the T2-weighted MR images. Since benign tumors sometimes mimic malignant tumors on MR images, exploratory laparotomy is essential to make a definitive diagnosis.
Berlemann U, et al. [Computer-assisted orthopedic surgery. From pedicle screw insertion to further applications]. Orthopade. 1997;26(5):463–9. Computer assisted orthopaedic surgery is a new but rapidly evolving field. Based on previous research and development in the area of stereotactic neuronavigation a few groups have adapted these technologies for the image interactive insertion of pedicle screws. The present paper summarizes past and current work in the field of computer assisted orthopaedic surgery and describes the state of the art of research and future innovations, particularly in in vivo applications.
Delp SL, et al. Computer assisted knee replacement. Clin Orthop Relat Res. 1998;(354):49–56. Accurate alignment of knee implants is essential for the success of total knee replacement. Although mechanical alignment guides have been designed to improve alignment accuracy, there are several fundamental limitations of this technology that will inhibit additional improvements. Various computer assisted techniques have been developed to examine the potential to install knee implants more accurately and consistently than can be done with mechanical guides. For example, computer integrated instrumentation incorporates highly accurate measurement devices to locate joint centers, track surgical tools, and align prosthetic components. Image guided knee replacement provides a three-dimensional preoperative plan that guides the placement of the cutting blocks and prosthetic components. Robot assisted knee replacement allows one to machine bones accurately without the use of standard cutting blocks. The rationale for the development of computer assisted knee replacement systems is presented, the operation of several different systems is described, the advantages and disadvantages of different approaches are discussed, and areas for future research are suggested.
Jaramaz B, et al. Computer assisted measurement of cup placement in total hip replacement. Clin Orthop Relat Res. 1998;(354):70–81. The introduction of image guided systems in total hip replacement surgery provides the ability to plan precisely the alignment of the acetabular cup before surgery, and to perform the surgery according to the preoperative plan. Preoperative planners (interactive computer programs for surgical planning) based on three-dimensional medical images allow planning of optimal placement of implant components based on simulated implant performance. Exact measurement of the cup position during surgery allows precise placement of the cup and accurate measurement of the final position of the cup relative to the pelvis. This measurement is used to evaluate the radiographic techniques for postoperative measurement of cup alignment. Malposition of the acetabular component increases the occurrence of impingement, reduces the safe range of motion, and increases the risk of dislocation and wear. Dislocation of the implant after total hip replacement remains a significant clinical problem. Not fully understanding the interaction between pelvic orientation and final acetabular cup alignment may be one of the main contributing factors in the continued significant incidence of dislocations after total hip replacement. In this study an attempt was made to link the preoperative planning, intraoperative placement, and postoperative measurement of cup placement in total hip replacement using computer assisted techniques.
Gautier E, et al. Accuracy of computer-guided screw fixation of the sacroiliac joint. Clin Orthop Relat Res. 2001;(393):310–7. Computer-assisted image guidance allows precise preoperative planning and intraoperative localization of surgical instruments. The technique recently was validated for the insertion of pedicle screws. In the laboratory, the precision of a surface-matching algorithm was evaluated for registration and accuracy and safety of screw placement into the vertebral bodies of S1 and S2 for fixation of the sacroiliac joint. Using six plastic pelves, 24 screw holes were made through the sacroiliac joint into the vertebral body of S1, and 12 holes were made through the sacroiliac joint into S2. The accuracy of the hole position was evaluated using a postoperative computed tomography examination. The safety factor was assessed by analysis of the remaining bone stock around the holes calculating a theoretical cylindrical volume being outside bone with increasing bore hole diameters. The registration was accurate with a mean error less than 1.4 mm in the posterior parts of the pelvis. The drilling followed precisely the preoperatively planned trajectories; perforation of the cortex of the sacrum was not observed. The safety factor of the S1 vertebral body is higher than that of S2 allowing larger diameter screw insertion into S1. This technique provides a safe and precise guide for transcutaneous or open insertion of iliosacral screws in cases of iliosacral dislocation or sacral fracture.
Hufner T, et al. Computer-assisted fracture reduction: novel method for analysis of accuracy. Comput Aided Surg. 2001;6(3):153–9. Anatomic reduction of displaced fractures is limited by the chosen surgical approach and intraoperative visualization. Preoperative Computed Tomography (CT) enhances the analysis of the fracture pattern and provides accurate spatial relationships. Computer Assisted Surgery (CAS) was introduced to increase the accuracy of specific surgical procedures. CAS systems can be used for implant placement or osteotomies in intact bone or reduced situations prior to obtaining the CT data, as differentiation into different datasets related to specific fragments is not yet possible. We present a model that allows “virtual” controlled reduction, providing computer assistance during the fracture reduction. Prior to clinical application, the accuracy of the process of virtual reduction must be proven in an experimental setting. An in vitro fracture model with two body fragments and a motion tracking system for three-dimensional (3D) control (accuracy 0.1 mm and 0.1 degrees ) was used. Two methods were employed: direct visualization and reduction by the examiner, and “virtual” reduction, performed solely with the use of a computer image, in which the examiner lacks any direct visualization of the fragments. The results of this very simplified “fracture” model indicate that the overall difference between direct and virtual controlled reduction was very small. A significant difference of 0.3 mm (0-1.8 mm) was seen for the residual displacement represented by the Euclidean distance (p < 0.01), whereas the difference in the residual angulation was not significant (p > 0.05). The methods tested revealed that virtual controlled reduction is nearly as accurate as direct visualization. Reduction control utilizing a motion tracker system reveals accurate 3D information in this simplified reduction setup, and is now used as a standard setup for analyzing realistic fracture models.
Zura RD, Kahler DM. A transverse acetabular nonunion treated with computer-assisted percutaneous internal fixation. A case report. J Bone Joint Surg Am. 2000;82(2):219–24.
Ritacco LE, et al. Accuracy of 3-D planning and navigation in bone tumor resection. Orthopedics. 2013;36(7):e942–50. Surgical precision in oncologic surgery is essential to achieve adequate margins in bone tumor resections. Three-dimensional preoperative planning and bone tumor resection by navigation have been introduced to orthopedic oncology in recent years. However, the accuracy of preoperative planning and navigation is unclear. The purpose of this study was to evaluate the accuracy of preoperative planning and the navigation system. A total of 28 patients were evaluated between May 2010 and February 2011. Tumor locations were the femur (n=17), pelvis (n=6), sacrum (n=2), tibia (n=2), and humerus (n=1). All resections were planned in a virtual scenario using computed tomography and magnetic resonance imaging fusion. A total of 61 planes or osteotomies were performed to resect the tumors. Postoperatively, computed tomography scans were obtained for all surgical specimens, and the specimens were 3-dimensionally reconstructed from the scans. Differences were determined by finding the distances between the osteotomies virtually programmed and those performed. The global mean of the quantitative comparisons between the osteotomies programmed and those obtained through the resected specimen was 2.52+/-2.32 mm for all patients. Differences between osteotomies virtually programmed and those achieved by navigation intraoperatively were minimal.
Ritacco LE, et al. Bone tumor resection: analysis about 3D preoperative planning and navigation method using a virtual specimen. Stud Health Technol Inform. 2013;192:1162. The use of three-dimensional preoperative planning and bone tumor resection guided by navigation has increased in the last ten years. However, no study to date, as far as we know, has directly provided evidence of accuracy of this method. The objective of this study was to describe a method capable of determining the accuracy of osteotomies performed for tumor resection planned and guided by navigation. We hypothesize that matching the 3D reconstructed surgical specimen is an acceptable method to determine the accuracy of virtual planning and navigation. A total of seven patients and 14 osteotomies were evaluated. After surgery, all surgical specimens were 3D reconstructed from CT images. The mean of quantitative comparisons between osteotomies planned and osteotomies obtained through the resected specimen was in a global mean of 1.56 millimeters (SD: 2.91) for all the cases. Based on our observations, a three-dimensional model obtained from the tumor surgical specimen is a useful tool to determine accuracy of 3D planning and surgical navigation.
Jones BC, et al. Synovial sarcoma: MR imaging findings in 34 patients. AJR Am J Roentgenol. 1993;161(4):827–30. OBJECTIVE: MR imaging is considered the procedure of choice for detecting and staging soft-tissue tumors. Its ability to show differences between benign and malignant soft-tissue tumors and its usefulness in suggesting a specific histologic diagnosis remain controversial. We studied the MR features of synovial sarcoma in 34 patients to determine if these tumors have specific MR findings that can be used to suggest the diagnosis. MATERIALS AND METHODS: MR imaging studies of 34 patients with synovial sarcoma were collected from two institutions and studied to determine the following characteristics of the tumor: size, shape, location, signal intensity and homogeneity, margin definition, presence of hemorrhage, and relationships to adjacent structures. These findings were then correlated with pathologic findings. RESULTS: The tumors tended to be deep, large (85% were > or = 5 cm in diameter), and located in the extremities with epicenters close to joints (63% within 7 cm of a joint). The lesions were usually inhomogeneous on T2-weighted images (82%) and clearly delineated from surrounding tissues (91%). Forty-four percent had high signal consistent with hemorrhage on both T1- and T2-weighted images. Fluid-fluid levels, best visualized on T2-weighted images, were present in 18% of patients. Thirty-five percent of the lesions had areas that were hyper-, iso-, and hypointense relative to fat on T2-weighted images, constituting a triple signal intensity. The tumors frequently involved adjacent bone, with 71% invading, eroding, or touching bone. No association of pathologic subtypes with specific imaging findings was noted. CONCLUSION: Our results show a spectrum of MR imaging findings in synovial sarcoma. Nevertheless, the results suggest that synovial sarcoma should be considered when MR images show a relatively well-defined but inhomogeneous hemorrhagic lesion near a joint and in contact with bone. Fluid-fluid levels and areas hyper-, hypo-, and isointense relative to fat (triple signal) on T2-weighted sequences support the diagnosis.
Takao M, et al. Application of a CT-3D fluoroscopy matching navigation system to the pelvic and femoral regions. Comput Aided Surg. 2012;17(2):69–76. OBJECTIVE: The aim of this study was to find the proper location of the fluoroscopic imaging center in order to apply a CT-based 3D fluoroscopy matching navigation system in the pelvic and femoral regions. MATERIALS AND METHODS: To simulate surgeries around the hip joint, a dry human pelvis and femur were used. A total of 16 fiducial markers, each consisting of a metal ball 1.5 mm in diameter, were fixed to the pelvis and femur. For the pelvis, the pubic symphysis, the acetabular fossa, and a site on the ilium 3 cm above the acetabular roof were selected as fluoroscopic imaging centers. For the proximal femur, the base of the femoral neck, the femoral shaft at the level of the lesser trochanter, and the inferior border of the great trochanter were selected as fluoroscopic imaging centers. RESULTS: Target registration error (TRE) differed significantly among the selected fluoroscopic imaging centers. The best mean TRE for the pelvis was 0.8 mm (range: 0.2 to 1.6 mm) with the imaging center on the ilium (3 cm above the acetabular roof). The best mean TRE for the proximal femur was 1.1 mm (range: 0.2 to 2.0 mm) with the imaging center on the femoral shaft at the lesser trochanter level. CONCLUSION: Fluoroscopic imaging center location had a significant effect on the accuracy of the CT-based 3D fluoroscopy matching navigation system in the pelvic and femoral regions. The proper fluoroscopic imaging centers for CT-3D fluoroscopic matching were, for the pelvis, a site on the ilium 3 cm above the acetabular roof, and for the proximal femur, the femoral shaft at the level of the lesser trochanter.
Lionberger R. The attraction of electromagnetic computer-assisted navigation in orthopaedic surgery. In: Stiehl JB, Konermann W, Hacker R, editors. Navigation and MIS in orthopaedic surgery. Heidelberg: Springer; 2006. p. 44–53.
Frantz DD, et al. Accuracy assessment protocols for electromagnetic tracking systems. Phys Med Biol. 2003;48(14):2241–51. Electromagnetic tracking systems have found increasing use in medical applications during the last few years. As with most non-trivial spatial measurement systems, the complex determination of positions and orientations from their underlying raw sensor measurements results in complicated, non-uniform error distributions over the specified measurement volume. This makes it difficult to unambiguously determine accuracy and performance assessments that allow users to judge the suitability of these systems for their particular needs. Various assessment protocols generally emphasize different measurement aspects that typically arise in clinical use. This can easily lead to inconclusive or even contradictory conclusions. We examine some of the major issues involved and discuss three useful calibration protocols. The measurement accuracy of a system can be described in terms of its ‘trueness’ and its ‘precision’. Often, the two are strongly coupled and cannot be easily determined independently. We present a method that allows the two to be disentangled, so that the resultant trueness properly represents the systematic, non-reducible part of the measurement error, and the resultant precision (or repeatability) represents only the statistical, reducible part. Although the discussion is given largely within the context of electromagnetic tracking systems, many of the results are applicable to measurement systems in general.
Khadem R, et al. Comparative tracking error analysis of five different optical tracking systems. Comput Aided Surg. 2000;5(2):98–107. OBJECTIVE: Effective utilization of an optical tracking system for image-based surgical guidance requires optimal placement of the dynamic reference frame (DRF) with respect to the tracking camera. Unlike other studies that measure the overall accuracy of a particular navigation system, this study investigates the precision of one component of the navigation system: the optical tracking system (OTS). The precision of OTS measurements is quantified as jitter. By measuring jitter, one can better understand how system inaccuracies depend on the position of the DRF with respect to the camera. MATERIALS AND METHODS: Both FlashPointtrade mark (Image Guided Technologies, Inc., Boulder, Colorado) and Polaristrade mark (Northern Digital Inc., Ontario, Canada) optical tracking systems were tested in five different camera and DRF configurations. A linear testing apparatus with a software interface was designed to facilitate data collection. Jitter measurements were collected over a single quadrant within the camera viewing volume, as symmetry was assumed about the horizontal and vertical axes. RESULTS: Excluding the highest 5% of jitter, the FlashPoint cameras had an RMS jitter range of 0.028 +/- 0.012 mm for the 300 mm model, 0.051 +/- 0.038 mm for the 580 mm model, and 0.059 +/- 0.047 mm for the 1 m model. The Polaris camera had an RMS jitter range of 0.058 +/- 0.037 mm with an active DRF and 0.115 +/- 0.075 mm with a passive DRF. CONCLUSION: Both FlashPoint and Polaris have jitter less than 0.11 mm, although the error distributions differ significantly. Total jitter for all systems is dominated by the component measured in the axis directed away from the camera.
Milne AD, et al. Accuracy of an electromagnetic tracking device: a study of the optimal range and metal interference. J Biomech. 1996;29(6):791–3. The positional and rotational accuracy of a direct-current magnetic tracking device commonly used in biomechanical investigations was evaluated. The effect of different metals was also studied to determine the possibility of interference induced by experimental test fixtures or orthopaedic implants within the working field. Positional and rotational data were evaluated for accuracy and resolution by comparing the device output to known motions as derived from a calibrated grid board or materials testing machine. The effect of different metals was evaluated by placing cylindrical metal samples at set locations throughout the working field and comparing the device readings before and after introducing each metal sample. Positional testing revealed an optimal operational range with the transmitter and receiver separation between 22.5 and 64.0 cm. Within this range the mean positional error was found to be 1.8 percent of the step size, and resolution was determined to be 0.25 mm. The mean rotational error over a 1-20 degree range was found to be 1.6% of the rotational increment with a rotational resolution of 0.1 degrees. Of the metal alloys tested only mild steel produced significant interference, which was maximum when the sample was placed adjacent to the receiver. At this location the mild steel induced a positional difference of 5.26 cm and an angular difference of 9.75 degrees. The device was found to be insensitive to commonly used orthopaedic alloys. In this study, the electromagnetic tracking device was found to have positional and rotational errors of less than 2 percent, when utilized within its optimal operating range. This accuracy combined with its insensitivity to orthopaedic alloys should make it suitable for a variety of musculoskeletal research investigations.
Stiehl JB, et al. Accuracy of acetabular component positioning with a fluoroscopically referenced CAOS system. Comput Aided Surg. 2005;10(5–6):321–7. OBJECTIVE: This study evaluated the accuracy, repeatability, and reproducibility of a fluoroscopic referenced system used for guiding acetabular component positioning. METHODS: Calibration of the Medtronic StealthStation Treon Plus system was performed using a Weber gage block to assess linearity. Metrologic validation of repeatability and reproducibility was done using a cadaveric pelvis with an uncemented cup placed in the target position of 45 degrees inclination and 17.5 degrees anteversion. A baseline assessment was done with a National Institute of Standards and Technology (NIST) traceable coordinate measuring machine (CMM). RESULTS: Weber gage block analysis revealed a mean bias of 0.69 mm. For the cadaveric pelvis, the anterior pelvic plane was determined using the bilateral anterior superior iliac spines with the symphysis pubis as the inferior landmark. The mean CMM measurement was inclination of 46.023 degrees (SD=1.075; range: 43.318-46.844 degrees) and anteversion of 15.787 degrees (SD=0.411; range: 15.068-16.384 degrees). One surgeon performed a repeatability assessment (n=8), finding mean inclination of 42.8 degrees (SD=1.5; range: 39.5-44.5 degrees) and anteversion of 17.5 degrees (SD=3.0; range: 14.5-22.5 degrees). Three surgeons performed a reproducibility assessment (n=24), finding mean overall inclination of 48.5 degrees (SD=0.9; range: 46-50 degrees) and anteversion of 17.8 degrees (SD=2.5; range: 13.5-23.5 degrees). All measurements were within a predefined acceptability range of+/-5 degrees. DISCUSSION: The accuracy and reproducibility of the fluoroscopic referencing method was found to be suitable for determination of cup position in the surgical setting. Anteversion measurements were more variable for the fluoroscopic method and this may be related to the difficulty for the surgeon in predictably picking the anatomical points from the fluoroscopic image.
Lembeck B, et al. Pelvic tilt makes acetabular cup navigation inaccurate. Acta Orthop. 2005;76(4):517–23. BACKGROUND: Modern navigation techniques allow precise positioning of the acetabular cup relative to the anterior pelvic plane. Variations in pelvic tilt will affect the resulting spatial orientation of the cup. METHODS: We measured pelvic tilt in 30 volunteers with an inclinometer combined with an ultrasonographic position measurement system. A mathematical algorithm was developed to calculate the resulting cup position measured on standard radiographs, depending on pelvic tilt. RESULTS: Average pelvic tilt at rest was -4 degrees in the lying position and -8 degrees in the standing position, and ranged from -27 degrees to +3 degrees. Pelvic reclination of 1 degree will lead to functional anteversion of the cup of approximately 0.7 degree. INTERPRETATION: Pelvic tilt makes navigation systems referring to the anterior plane inaccurate.
Thaler M, et al. Accuracy of an image-guided navigation system for pelvic surgery based on a multimodality registration object: a cadaver study. Am J Orthop (Belle Mead NJ). 2010;39(8):382–5. Accurate registration of external landmarks is often required for computer-aided surgery. In the study reported here, we investigated the influence of a new externally fixated multimodality registration object (MRO) on the accuracy of an image-guided navigation system in a human cadaver pelvis. With the MRO placed on the ipsilateral anterior superior iliac spine (ASIS), 14 of 17 target points showed a mean deviation (1.1 mm) that was significantly lower than that registered with the MRO on the contralateral ASIS (2.5 mm). In addition, the distance of target points from the MRO and the deviation of target points were highly correlated. This MRO provides a feasible means for achieving improved registration in computer-aided surgery of the pelvis.
Van Hellemondt G, et al. Computer-assisted pelvic surgery: an in vitro study of two registration protocols. Clin Orthop Relat Res. 2002;(405):287–93. An in vitro study was done to test the accuracy and functionality of computer-assisted surgery in pelvic orthopaedic surgery. The study was done on two fresh hips from one cadaver. In each hip, 10 titanium marker screws were inserted through standard pelvic osteotomy incisions. After a computed tomography scan was obtained the data were introduced into the navigation system. For the accuracy measurements the location of the center of the spherical heads of the marker screws was determined relative to a reference base attached to the pelvis using a special pointer that corresponded to the spherical head of the screws. A randomized trial was done with two surgeons to test the accuracy of two different anatomy-based registration protocols. The deviation between the virtual position of the marker screws in the pelvis, calculated by the computer after each anatomy based registration, and the real position were compared for each registration. Accuracy is not only related to the distance of the computed tomography slices and the necessary computed tomography field of view but also depends on the location of the point on the pelvis.
Sternheim A, et al. Navigated pelvic osteotomy and tumor resection: a study assessing the accuracy and reproducibility of resection planes in Sawbones and cadavers. J Bone Joint Surg Am. 2015;97(1):40–6. BACKGROUND: This Sawbones and cadaver study was performed to assess the accuracy and reproducibility of pelvic bone cuts made with use of a novel navigation system with a navigated osteotome and oscillating saw. METHODS: Using a novel navigation system and a three-dimensional planning tool, we navigated pelvic bone cuts that were representative of typical cuts made in pelvic tumor resections. The system includes a prototype mobile C-arm for intraoperative cone-beam computed tomography, real-time optical tracking (Polaris), and three-dimensional visualization software. Three-dimensional virtual radiographs were utilized in addition to triplanar (axial, sagittal, and coronal) navigation. In part one of the study, we navigated twenty-four sacral bone cuts in Sawbones models and validated our results in sixteen similar cuts in cadavers. In part two, we developed three Sawbones models of pelvic tumors based on actual patient scenarios and compared three navigated resections with three non-navigated resections for each tumor model. Part three assessed the accuracy of the system with multiple users. RESULTS: There were ninety navigated cuts in Sawbones that were compared with fifty-four non-navigated cuts. In the navigated Sawbones cuts, the mean entry and exit cuts were 1.4 +/- 1 mm and 1.9 +/- 1.2 mm from the planned cuts, respectively. In comparison, the entry and exit cuts in Sawbones that were not navigated were 2.8 +/- 4.9 mm and 3.5 +/- 4.6 mm away from the planned osteotomy site. The navigated cuts were significantly more accurate (p </= 0.01). In the cadaver study, navigated entry and exit cuts were 1.5 +/- 0.9 mm and 2.1 +/- 1.5 mm from the planned cuts. The variation among three different users was 1 mm on both the entry and exit cuts. CONCLUSIONS: Navigation to guide pelvic bone cuts is accurate and feasible. Three-dimensional radiographs should be used for improved accuracy. Navigated cuts were significantly more accurate than non-navigated cuts were. A margin of 5 mm between the target tumor volume and the planned cut plane would result in a negative margin resection in more than 95% of the cuts. CLINICAL RELEVANCE: The accuracy of pelvic bone tumor resections and pelvic osteotomies can be improved with navigation to within 5 mm of the planned cut.
Cho HS, et al. Direct application of MR images to computer-assisted bone tumor surgery. J Orthop Sci. 2011;16(2):190–5. BACKGROUND: We describe a method for the direct application of MR images to navigation-assisted bone tumor surgery as an alternative to CT-MRI fusion. METHOD: Six patients with an orthopedic malignancy were employed for this method during navigation-assisted tumor resection. Tumor types included osteosarcoma (4), high-grade chondrosarcoma (1), and adamantinoma (1). Mean patient age was 25.3 years (range 18-52 years). Mean duration of follow-up was 25.8 months (range 18-32 months). Resorbable pin placement and rapid 3-dimensional spoiled gradient echo sequences made the direct application of MR images to computer-assisted bone tumor surgery without CT-MR image fusion possible. A paired-point registration technique was employed for patient-image registration in all patients. RESULTS: It took 20 min on average to set up the navigation (range 15-25 min). The mean registration error was 0.98 mm (range 0.4-1.7 mm). On histologic examination, distances from tumors to resection margins were in accord with preoperative plans. No patient had a local recurrence or distant metastasis at the last follow-up. CONCLUSION: Direct patient-to-MRI registration is a very useful method for bone tumor surgery, permitting the application of MR images to intraoperative visualization without any additional costs or exposure of the patient to radiation from the preoperative CT scan.
Pappas IP, et al. New method to assess the registration of CT-MR images of the head. Injury. 2004;35 Suppl 1:S-A105-112. Due to their complementary information content, both x-ray computed tomography (CT) and magnetic resonance (MR) imaging are employed in certain clinical cases to improve the understanding of pathology involved. o spatially relate the two datasets, image registration and image fusion are employed. However, registration errors, either global or local, are common and are nonuniform within the image volume. In this paper, we propose a new algorithm that assesses the quality of the registration locally within the CT-MR volume and provides visual, color-coded feedback to the user about the location and extent of good and bad correspondence between the two images. The proposed registration assessment algorithm is based on a correspondence analysis of bone structures in the CT and MR images. For that purpose, a custom segmentation algorithm for bone in MR images has been developed that is based on a stochastic threshold computation method. This segmentation method for MR images and the CT-MR registration assessment algorithm were validated on simulated MR datasets and real CT-MR image pairs of the head. Some partial-volume effects occur at the borders of the bone structures and at the bone interfaces with air, which cannot be separated from bone in the MR image. The presented assessment method of CT-MR image registration offers the user a new tool to evaluate the overall and local quality of the registration. With this information, the user does not have to blindly trust the fused CT-MR datasets but can easily identify areas of inaccurate correspondence. The application of the algorithm is so far limited to T1-weighted MR and CT images of the head area.
Amiot LP, Poulin F. Computed tomography-based navigation for hip, knee, and spine surgery. Clin Orthop Relat Res. 2004;(421):77–86. A review of CT-based orthopaedic navigation is presented with a specific emphasis on arthroplasty for the hip and the knee. Fundamental issues about the laboratory and clinical validation of the applications are addressed. The ability to compute the position and orientation of an acetabular implant using a postoperative CT scan was investigated. Angle deviations relative to known positions were computed with an error of less than 1 degree. Then, the system accuracy for three-dimensional reconstruction and registration of two cadaveric pelvis specimens was measured with more than 350 registrations. We observed a maximal inclination error of 5 degrees in 99% of cases and a maximal anteversion error of 5 degrees in 97% of cases. The accuracy of the three-dimensional reconstruction and registration for knee arthroplasty also was measured and computed with an angular accuracy of 0.5 degrees in the AP plane and accuracy of 3 degrees in the lateral plane. A clinical study then was done in 109 cases where 96% of implants were installed with a hip-knee-ankle angle of 180 +/- 3 degrees. Computed tomography-based navigation for orthopaedic surgery provides greater accuracy and reproducibility than conventional surgery. As noted by learning curves, software improvements are needed to bring it into daily clinical routine.
Docquier PL, et al. Registration accuracy in computer-assisted pelvic surgery. Comput Aided Surg. 2009;14(1–3):37–44. INTRODUCTION: An in vitro study was performed to assess the global registration accuracy of a computer-assisted system in pelvic orthopaedic surgery. The system was applied to a putative tumor resection in a pelvic sawbone. METHODS: Twenty landmarks were created on the surface of the pelvis, and a virtual model of the sawbone was constructed based on surface extraction from computed tomography. The coordinates of the landmarks were defined in the CT-scan coordinate system, and registration of the sawbone with the virtual model was achieved using a surface-based matching algorithm. The landmarks were considered as control points, and deviations between their physical locations and their locations in the virtual model were calculated, thereby quantifying the global accuracy error. RESULTS: The location of the initialization points was unimportant. The dynamic reference base gave the best results when placed far from the working area. Accuracy was improved when the sampling area was increased, but was decreased by its excessive expansion. CONCLUSIONS: It is recommended that the DRB be located on the contralateral side of the pelvis. Extending the approach posteriorly and including the entire working area in the sampling surface area, if possible, will also help increase accuracy in computer-assisted pelvic surgery.
Mayr E, et al. The effect of fixation and location on the stability of the markers in navigated total hip arthroplasty: a cadaver study. J Bone Joint Surg Br. 2006;88(2):168–72. In navigated total hip arthroplasty, the pelvis and the femur are tracked by means of rigid bodies fixed directly to the bones. Exact tracking throughout the procedure requires that the connection between the marker and bone remains stable in terms of translation and rotation. We carried out a cadaver study to compare the intra-operative stability of markers consisting of an anchoring screw with a rotational stabiliser and of pairs of pins and wires of different diameters connected with clamps. These devices were tested at different locations in the femur. Three human cadavers were placed supine on an operating table, with a reference marker positioned in the area of the greater trochanter. K-wires (3.2 mm), Steinman pins (3 and 4 mm), Apex pins (3 and 4 mm), and a standard screw were used as fixation devices. They were positioned medially in the proximal third of the femur, ventrally in the middle third and laterally in the distal portion. In six different positions of the leg, the spatial positions were recorded with a navigation system. Compared with the standard single screw, with the exception of the 3 mm Apex pins, the two-pin systems were associated with less movement of the marker and could be inserted less invasively. With the knee flexed to 90 degrees and the dislocated hip rotated externally until the lower leg was parallel to the table (figure-four position), all the anchoring devices showed substantial deflection of 1.5 degrees to 2.5 degrees. The most secure area for anchoring markers was the lateral aspect of the femur.
Wiles AD, Thompson D, Frantz DD. Accuracy assessment and interpretation for optical tracking systems. Med Imaging. 2004;5367:1–12.
Oszwald M, et al. Accuracy of navigated surgery of the pelvis after surface matching with an a-mode ultrasound probe. J Orthop Res. 2008;26(6):860–4. Computer-aided surgery (CAS) allows for real-time intraoperative feedback resulting in increased accuracy, while reducing intraoperative radiation. CAS is especially useful for the treatment of certain pelvic ring fractures, which necessitate the precise placement of screws. Flouroscopy-based CAS modules have been developed for many orthopedic applications. The integration of the isocentric flouroscope even enables navigation using intraoperatively acquired three-dimensional (3D) data, though the scan volume and imaging quality are limited. Complicated and comprehensive pathologies in regions like the pelvis can necessitate a CT-based navigation system because of its larger field of view. To be accurate, the patient’s anatomy must be registered and matched with the virtual object (CT data). The actual precision within the region of interest depends on the area of the bone where surface matching is performed. Conventional surface matching with a solid pointer requires extensive soft tissue dissection. This contradicts the primary purpose of CAS as a minimally invasive alternative to conventional surgical techniques. We therefore integrated an a-mode ultrasound pointer into the process of surface matching for pelvic surgery and compared it to the conventional method. Accuracy measurements were made in two pelvic models: a foam model submerged in water and one with attached porcine muscle tissue. Three different tissue depths were selected based on CT scans of 30 human pelves. The ultrasound pointer allowed for registration of virtually any point on the pelvis. This method of surface matching could be successfully integrated into CAS of the pelvis.
Arand M, et al. [Sources of error and risks in CT based navigation]. Orthopade. 2002;31(4):378–84. Based on the experience of 4 cervical, 102 thoracic/lumbar pedicle screw and 14 transiliosacral screw implantations all problems and complications were collected. Problems noted within the data collection in the preoperative CT were an incomplete acquisition of the surgical target (n = 3), an exceeding of the processable scan slices (n = 1) and a non focused field of view. Transmission of the CT datas often were documented as incomplete (n = 16). Segmentation of the CT dataset turned out to be the significant problem with incorrect differentiation of the bone-soft tissue transition (n = 2), where as the choice of the matching points and the trajectories did not provoke any mistakes in the planning modus. The intraoperative matching of both corresponding datasets was insufficient (n = 7), while the assignment of the CT dataset to the correct vertebral was not a major problem (n = 1). Navigation was not possible (n = 2) due to an instability of the spinal process. All fiducial based matching procedures (pelvis) were carried out without any problems. During intraoperative navigation potential complications resulted from deformation of instruments (n = 1) and interaction of instruments and the data reference base (n = 2). Further, the CT-based navigation of fractured vertebrae or unstable iliosacral joints is not safe, because dislocations between acquisition of the dataset and operation will lead to misguidance.
Sakai Y, et al. Simultaneous registration with ct-fluoro matching for spinal navigation surgery. A case report. Nagoya J Med Sci. 2006;68(1–2):45–52. Computer-assisted surgery, which provides simultaneous, multiplanar images of bone structures, has become widely used. However, registration maneuvering remains time consuming. The objective of this paper is to document the usefulness of CT-fluoro matching for spinal navigation. A spinal navigation system (VECTORVISION compact; Brain LAB, Germany) and a digital imaging system (OEC9800; CATHEX, Tokyo, Japan) were used for CT-fluoro matching in cases of L4/5 and L5/S1 posterior lumbar interbody fusion. A reference array was attached to the L4 spinous process. Preoperative CT images and intraoperative fluoro-shots including L4, L5, and S1 were superimposed on the navigation monitor. Following insertion of L4 screws, a reference array remained to be attached to the L4 spinous process, after which a level definition and pre-registration of L5 and S1 vertebrae were performed and the screwing procedure of L5 and S1 was completed without additional fluro-shots. Registration of three vertebrae was completed without paired-point or surface-matching procedures. The calculation time for the registration in a single vertebra was 30 sec. All pedicle screws were seen to be successfully inserted on postoperative CT images. We performed the navigation surgery by matching the preoperative CT images to the intraoperative fluoro-shots without manual registration. This technique may prove useful in the future for anterior spinal surgery and percutaneous screwing without the need for total exposure of the bone surface.
Stockle U, et al. Image guidance in pelvic and acetabular surgery—expectations, success and limitations. Injury. 2007;38(4):450–62. During the last decade navigation techniques in pelvic and acetabular surgery have been described. Nowadays, available techniques include CT-based navigation, 2D C-arm navigation and 3D C-arm navigation. The main indication is the navigated percutaneous SI screw fixation, but acetabular screw fixations are also reported. In this article, based upon a literature review and our own clinical experiences, the indications for and limitations of navigated techniques in pelvic and acetabular surgery are described.
Bachler R, et al. Restricted surface matching—numerical optimization and technical evaluation. Comput Aided Surg. 2001;6(3):143–52. Accurate and reliable registration is one of the most important issues in computer-aided surgery, as small errors may have a large influence on the overall accuracy of the system. The restricted surface-matching algorithm (RSM), initially developed for periacetabular osteotomy surgery (PAO), has been improved to become numerically more stable and reliable. To assess the accuracy and sensitivity of registration, a framework is presented that evaluates two aspects of registration: the sensitivity and raw performance of the registration algorithm are tested in a stand-alone environment, and the integration into a CAS system is analyzed by evaluating the accuracy of the complete system. For the latter tests, spherical-headed titanium screws used as fiducial landmarks provide a reference transformation for the registration. This framework was used to analyze the performance of RSM for PAO surgery. The sensitivity analysis showed the algorithm to be insensitive to noise up to a magnitude of 3 mm. Both the sensitivity analysis and simulated surgical environment tests showed that an accuracy can be attained of better than 2 mm in the region of interest, and better than 4 mm far away from the region of interest. This is sufficient for safely assisting PAO surgeries.
Wong KC, Kumta SM. Computer-assisted tumor surgery in malignant bone tumors. Clin Orthop Relat Res. 2013;471(3):750–61. BACKGROUND: Small recent case series using CT-based navigation suggest such approaches may aid in surgical planning and improve accuracy of intended resections, but the accuracy and clinical use have not been confirmed. QUESTIONS/PURPOSES: We therefore evaluated (1) the accuracy; (2) recurrences; and (3) function in patients treated by computer-assisted tumor surgery (CATS). METHODS: From 2006 to 2009, we performed CATS in 20 patients with 21 malignant tumors. The mean age was 31 years (range, 6-80 years). CT and MR images for 18 cases were fused using the navigation software. Reconstructed two-dimensional/three-dimensional images were used to plan the bone resection. The achieved bone resection was compared with the planned one by assessing margins, dimensions at the level of bone resection, or fitting of CAD custom prostheses. Function was assessed with the Musculoskeletal Tumor Society (MSTS) score. The minimum followup was 31 months (mean, 39 months; range, 5-69 months). RESULTS: Histological examination of all resected specimens showed a clear tumor margin. The achieved bone resection matched the planned with a difference of </= 2 mm. The achieved positions of custom prostheses were comparable to the planned positions when merging postoperative with preoperative CT images in five cases. Three of the four patients with local recurrence had tumors at the sacral region. The mean MSTS score was 28 (range, 23-30). CONCLUSION: CATS with image fusion allows accurate execution of the intended bone resection. It may be beneficial to resection and reconstruction in pelvic, sacral tumors and more difficult joint-preserving intercalated tumor surgery. Comparative clinical studies with long-term followup are necessary to confirm its efficacy. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
Wong KC, Kumta SM. Joint-preserving tumor resection and reconstruction using image-guided computer navigation. Clin Orthop Relat Res. 2013;471(3):762–73. BACKGROUND: Joint-preserving surgery is performed in select patients with bone sarcomas of extremities and allows patients to retain the native joint with better joint function. However, recurrences may relate to achieving adequate margins and there is frequently little room for error in tumors close to the joint surface. Further, the tumor margin on preoperative CT and/or MR images is difficult to transpose to the actual extent of tumor in the bone in the operating room. QUESTIONS/PURPOSES: We therefore determined whether joint-preserving tumor surgery could be performed accurately under image-guided computer navigation and determined local recurrences, function, and complications. METHODS: We retrospectively studied eight patients with bone sarcoma of extremities treated surgically by navigation with fused CT-MR images. We assessed the accuracy of resection in six patients by comparing the cross sections at the resection plane with complementary prosthesis templates. Mean age was 17 years (range, 6-46 years). Minimum followup was 25 months (mean, 41 months; range, 25-60 months). RESULTS: The achieved resection was accurate, with a difference of 2 mm or less in any dimension compared to that planned in patients with custom prostheses. We noted no local recurrence at latest followup. The mean Musculoskeletal Tumor Society score was 29 (range, 28-30). There were no complications related to navigation planning and procedures. There was no failure of fixation at the remaining epiphysis. CONCLUSIONS: In selected patients, the computer-assisted approach facilitates precise planning and execution of joint-preserving tumor resection and reconstruction. Further followup assessment in a larger study population is required in these patients. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
Salehi SA, Ondra SL. Use of internal fiducial markers in frameless stereotactic navigational systems during spinal surgery: technical note. Neurosurgery. 2000;47(6):1460–2. OBJECTIVE: The use of frameless stereotaxy has expanded the spine surgeon’s ability to perform surgical procedures with instrumentation in areas of narrow anatomic tolerance. In many circumstances, however, it is difficult to register the frameless stereotactic probe using known anatomic landmarks. This occurs typically because landmarks are indistinct, and congenital or surgical defects limit the availability of anatomic fiducials. We propose an accurate and efficient method for registering the frameless stereotactic probe for spinal surgery when a staged procedure is planned. METHODS: During the first stage of a planned two-stage procedure, a minimum of four cranial fiducial screws are implanted in the posterior element of each vertebra in which stereotactic registration is desired. Stage 1 is completed, and all suture closure is performed. A computed tomographic scan formatted for the frameless stereotactic unit is obtained postoperatively. In the second stage of surgery, registration is performed using cranial screws as internal fiducial markers. RESULTS: Registration is performed easily and quickly using cranial screws as internal fiducial markers. No more than four registration points are necessary to calibrate the system to accuracy within 1.5 mm. CONCLUSION: Implantation of fiducial markers during Stage 1 of a complex staged spinal surgery renders the frameless stereotactic navigational system registration extremely fast and accurate. We advocate the technique to enhance the use of frameless navigational systems for reliable and quick registration of the spine.
Hulen CA, et al. Oncologic and functional outcome following sacrectomy for sacral chordoma. J Bone Joint Surg Am. 2006;88(7):1532–9. BACKGROUND: Sacral chordoma is a rare, low to intermediate-grade tumor that poses substantial challenges in terms of timely diagnosis and adequate treatment. Few studies have examined the oncologic and functional outcomes of patients treated for sacral chordoma. METHODS: The clinical records of sixteen patients who had undergone sacrectomy for chordoma between 1985 and 2001 were evaluated retrospectively. All patients underwent resection by means of a sequential combined anterior and posterior approach. Patients were followed clinically at six-month intervals following recovery from the index surgical procedure. The disease onset, treatment, hospital stay, recurrence rates, survival, adjuvant therapy, functional outcome measures, and complications were evaluated. RESULTS: The average age at the time of diagnosis was sixty-one years. The mean tumor size was 15.2 cm in diameter, and all patients had a resection involving S1 or S2. The mean duration of follow-up was sixty-six months, and the tumor recurred in twelve of the sixteen patients. The mean time to metastasis was fifty months. Four patients were clinically disease-free at a mean follow-up of 94.5 months, while five patients died as a result of progressive local or metastatic disease at a mean follow-up of 31.4 months. Only one patient had normal bowel and bladder control postoperatively, and only three were able to walk without assistive devices. Eight patients had wound complications, and one patient had a deep-vein thrombosis. With the numbers available, neither negative margins at the time of initial tumor resection nor adjuvant radiation therapy had a significant impact on survival or local recurrence. More cephalad levels of resection were associated with significantly worse bowel (p = 0.01) and bladder (p = 0.01) control. Complications were frequent and were more common with a larger tumor size at the time of presentation (p = 0.034). CONCLUSIONS: The treatment of sacral chordoma is an arduous clinical undertaking that requires a multidisciplinary approach and attention to detail from the outset. Despite aggressive well-planned surgical management and adherence to strict surveillance protocols, frequent recurrence and the late onset of metastatic disease are to be expected in a substantial proportion of patients, especially those with a very large chordoma or one at a more cephalad level. Adequate surgical treatment results in substantial functional impairment and numerous complications; however, it does offer the possibility of long-term disease-free survival. We advocate an attempt at complete resection, when there is still a possibility of cure, and aggressive treatment of local recurrences. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.
Kendoff D, et al. Navigated Iso-C3D-based percutaneous osteoid osteoma resection: a preliminary clinical report. Comput Aided Surg. 2005;10(3):157–63. Minimally invasive osteoid osteoma resection under computer tomography (CT) guidance has yielded good results and has become a viable alternative to open surgical procedures. Limited visualization of the actual drill position under CT guidance can frequently result in inadequate and malpositioned drilling, especially at lesions located in less accessible anatomic regions. With the conventional CT-guided drilling technique, sterility and general operative management poorly correlate with standard operating room conditions, and are at risk of intra- and postoperative complications. The new Iso-C(3D) imaging device provides intraoperative multiplanar reconstructions. Adequate image quality and implementation in navigation systems were described for numerous indications. On the basis of multiplanar reconstructions, minimally invasive navigated techniques under three-dimensional surgical tool control become possible, which is not the case under fluoroscopic or CT-based navigation. We report on our first three cases of navigated Iso-C(3D) osteoid osteoma resection. A minimally invasive resection of the nidus was possible under permanent multiplanar image control. No complications were encountered and all patients reported successful outcomes. Minimally invasive-based navigation offered an effective and reproducible surgical approach. Dependence on CT imaging for proper positioning and complications associated with use away from the operating room environment can be avoided.
Cartiaux O, et al. Computer-assisted planning and navigation improves cutting accuracy during simulated bone tumor surgery of the pelvis. Comput Aided Surg. 2013;18(1–2):19–26. BACKGROUND: Resection of bone tumors within the pelvis requires good cutting accuracy to achieve satisfactory safe margins. Manually controlled bone cutting can result in serious errors, especially due to the complex three-dimensional geometry, limited visibility, and restricted working space of the pelvic bone. This experimental study investigated cutting accuracy during navigated and non-navigated simulated bone tumor cutting in the pelvis. METHODS: A periacetabular tumor resection was simulated using a pelvic bone model. Twenty-three operators (10 senior and 13 junior surgeons) were asked to perform the tumor cutting, initially according to a freehand procedure and later with the aid of a navigation system. Before cutting, each operator used preoperative planning software to define four target planes around the tumor with a 10-mm desired safe margin. After cutting, the location and flatness of the cut planes were measured, as well as the achieved surgical margins and the time required for each cutting procedure. RESULTS: The location of the cut planes with respect to the target planes was significantly improved by using the navigated cutting procedure, averaging 2.8 mm as compared to 11.2 mm for the freehand cutting procedure (p < 0.001). There was no intralesional tumor cutting when using the navigation system. The maximum difference between the achieved margins and the 10-mm desired safe margin was 6.5 mm with the navigated cutting process (compared to 13 mm with the freehand cutting process). CONCLUSIONS: Cutting accuracy during simulated bone cuts of the pelvis can be significantly improved by using a freehand process assisted by a navigation system. When fully validated with complementary in vivo studies, the planning and navigation-guided technologies that have been developed for the present study may improve bone cutting accuracy during pelvic tumor resection by providing clinically acceptable margins.
Cartiaux O, et al. Computer-assisted and robot-assisted technologies to improve bone-cutting accuracy when integrated with a freehand process using an oscillating saw. J Bone Joint Surg Am. 2010;92(11):2076–82. BACKGROUND: In orthopaedic surgery, many interventions involve freehand bone cutting with an oscillating saw. Such freehand procedures can produce large cutting errors due to the complex hand-controlled positioning of the surgical tool. This study was performed to investigate the potential improvements in cutting accuracy when computer-assisted and robot-assisted technologies are applied to a freehand bone-cutting process when no jigs are available. METHODS: We designed an experiment based on a geometrical model of the cutting process with use of a simulated bone of rectangular geometry. The target planes were defined by three variables: a cut height (t) and two orientation angles (beta and gamma). A series of 156 cuts were performed by six operators employing three technologically different procedures: freehand, navigated freehand, and robot-assisted cutting. After cutting, we measured the error in the height t, the absolute error in the angles beta and gamma, the flatness, and the location of the cut plane with respect to the target plane. RESULTS: The location of the cut plane averaged 2.8 mm after use of the navigated freehand process compared with 5.2 mm after use of the freehand process (p < 0.0001). Further improvements were obtained with use of the robot-assisted process, which provided an average location of 1.7 mm (p < 0.0001). CONCLUSIONS: Significant improvements in cutting accuracy can be achieved when a navigation system or an industrial robot is integrated into a freehand bone-cutting process when no jigs are available. The procedure for navigated hand-controlled positioning of the oscillating saw appears to be easy to learn and use.
Arand M, et al. Computer-guidance in percutaneous screw stabilization of the iliosacral joint. Clin Orthop Relat Res. 2004;(422):201–7. Nine patients with instability and one patient with degeneration of the iliosacral joint were treated surgically. The posterior pelvic ring was stabilized with the assistance of an optoelectronic navigation system. Registration was ensured by using fiducial screws in the iliac crest or by collecting landmarks on the external fixator. Computed tomography scans taken postoperatively provided additional information regarding implant localization in all patients. Accurate placement of 21 of 22 implanted iliosacral screws was observed. Two of the 21 screws touched the wall of the second sacral foramen without perforating the canal. One screw perforated the anterior wall of the sacrum because the navigated guide wire was bent during implantation. The initial results indicate that computer-aided frameless navigation in surgery of the iliosacral joint can facilitate surgical performance during screw stabilization in selected patients. Two important issues must be considered in the clinical application of this technique: first, any relative migration of the iliac and sacral bone structures between computed tomography scans taken preoperatively and intraoperative navigation may result in an intolerable inaccuracy of computer guidance. Second, bending of the guide wire of the tracked power drive, which cannot be accommodated by the navigation system, will lead to misguidance; therefore, only navigated drill sleeves should be used.
Kawai A, et al. Prognostic factors for patients with sarcomas of the pelvic bones. Cancer. 1998;82(5):851–9. BACKGROUND: Treatment of malignant tumors of the pelvis represents one of the most difficult problems in musculoskeletal oncology. However, factors that influence the local and systemic control of the disease remain ill-defined. METHODS: One hundred and two patients with localized pelvic sarcomas who underwent a surgical excision of the tumors were analyzed. The tumor diagnosis was chondrosarcoma in 49 patients, osteosarcoma in 26 patients, Ewing’s sarcoma in 20 patients, and other tumors in 7 patients. The tumor was located in the ilium in 65 patients, the pubis in 21 patients, the ischium in 8 patients, and the sacrum in 8 patients. Eighty-three patients underwent a limb-sparing surgery and 19 patients underwent hemipelvectomy. Prognostic factors for local recurrence, metastasis, and survival were analyzed. RESULTS: At last follow-up, 47 patients were disease free, 7 were alive with disease, and 48 had died. The 5-year survival rate was 55% (chondrosarcoma: 65%, osteosarcoma: 47%, and Ewing’s sarcoma: 52%). Inadequate surgical margin emerged as the only independent adverse prognostic factor for local recurrence. For distant metastasis, surgical stage remained as an independent prognostic factor. Patients who underwent a hemipelvectomy and those who had an inadequate surgical margin had significantly poorer survivals. CONCLUSIONS: Pelvic sarcomas remain diseases with a poor prognosis. Independent prognostic factors are few; an adequate surgical margin is critical to prevent local recurrence, and the surgical stage is related to the risk of distant metastasis. Surgical margins and hemipelvectomy were predictors of survival, but the patients who underwent hemipelvectomy also tended to have the largest, most advanced tumors. Hemipelvectomy should be considered when there is sacral involvement.
Cartiaux O, et al. Improved accuracy with 3D planning and patient-specific instruments during simulated pelvic bone tumor surgery. Ann Biomed Eng. 2014;42(1):205–13. In orthopaedic surgery, resection of pelvic bone tumors can be inaccurate due to complex geometry, limited visibility and restricted working space of the pelvis. The present study investigated accuracy of patient-specific instrumentation (PSI) for bone-cutting during simulated tumor surgery within the pelvis. A synthetic pelvic bone model was imaged using a CT-scanner. The set of images was reconstructed in 3D and resection of a simulated periacetabular tumor was defined with four target planes (ischium, pubis, anterior ilium, and posterior ilium) with a 10-mm desired safe margin. Patient-specific instruments for bone-cutting were designed and manufactured using rapid-prototyping technology. Twenty-four surgeons (10 senior and 14 junior) were asked to perform tumor resection. After cutting, ISO1101 location and flatness parameters, achieved surgical margins and the time were measured. With PSI, the location accuracy of the cut planes with respect to the target planes averaged 1 and 1.2 mm in the anterior and posterior ilium, 2 mm in the pubis and 3.7 mm in the ischium (p < 0.0001). Results in terms of the location of the cut planes and the achieved surgical margins did not reveal any significant difference between senior and junior surgeons (p = 0.2214 and 0.8449, respectively). The maximum differences between the achieved margins and the 10-mm desired safe margin were found in the pubis (3.1 and 5.1 mm for senior and junior surgeons respectively). Of the 24 simulated resection, there was no intralesional tumor cutting. This study demonstrates that using PSI technology during simulated bone cuts of the pelvis can provide good cutting accuracy. Compared to a previous report on computer assistance for pelvic bone cutting, PSI technology clearly demonstrates an equivalent value-added for bone cutting accuracy than navigation technology. When in vivo validated, PSI technology may improve pelvic bone tumor surgery by providing clinically acceptable margins.
Haider H, et al. Minimally invasive total knee arthroplasty surgery through navigated freehand bone cutting: winner of the 2005 “HAP” PAUL AWARD. J Arthroplast. 2007;22(4):535–42. Navigated freehand bone cutting (NFC) is introduced as a concept to eliminate alignment jigs and facilitate smaller arthroplasty incisions. We compare experimental cuts with this technique to conventional jigs. Using an in-house-built computer-aided orthopedic surgery system directly navigating a bone saw, users with different levels of surgical skills were timed performing full sets of distal femoral total knee arthroplasty cuts with jigs and with NFC. The cut surfaces were digitized to measure roughness and 3-dimensional translational/rotational errors. Navigated freehand cutting was 15% faster and produced 200% rougher surfaces than jigs, although its worst peaks/valleys were less than 1.2 mm. Implant fit/looseness, assessed by special navigated tools, was similar; but alignment was 400% better with NFC. Even at its infancy, NFC appears not to prohibitively compromise time and quality of cutting. Without requiring jigs, it has potential for radically less invasive total knee arthroplasty surgery.
Paul L, et al. Inaccuracy in selection of massive bone allograft using template comparison method. Cell Tissue Bank. 2008;9(2):83–90. The use of massive bone allografts is increasing year by year and selection method remains unchanged. Superposition of patient’s radiograph over allograft image and comparison of distances is the gold standard. Experiment was led to test selection procedure of a major european tissue bank. Four observers were asked to select an allograft for 10 fictive recipients. Nine allografts were provided. To simulate a perfect allograft, recipient himself was inserted in the pool of allografts (trap graft). The 10 potential bone transplants were classified in four categories (from adequate to unacceptable). In addition, observers were asked to choose the three best grafts for a given recipient. Quadratic kappa measuring agreement on classification between two observers ranged between 0.74 (substantial) and 0.47 (moderate). Trap graft was quoted by observers as adequate four times (10%) and was cited eight times (20%) among the three best matching allografts. None of the observers discovered that recipient was among allograft panel. This study demonstrates that current selection method is inaccurate for hemipelvic allograft selection. New methods should be developed and tested to assist tissue banks in bone allograft selection.
Schmerber S, Chassat F. Accuracy evaluation of a CAS system: laboratory protocol and results with 6D localizers, and clinical experiences in otorhinolaryngology. Comput Aided Surg. 2001;6(1):1–13. OBJECTIVES: The objective of the study reported in this article was to evaluate (1) localizer inaccuracies, one of the major sources of errors in Computer-Assisted Surgery (CAS) systems, and (2) the final errors obtained using surface-based registration in ear, nose, and throat (ENT) surgery. These objectives were met through (1) a technical evaluation of the accuracy and usability of several optical localizers under laboratory test conditions, and (2) a clinical measure of the global errors obtained when using a CAS system including one of the standard localizer systems (Flashpoint 5000) in Functional Endoscopic Sinus Surgery (FESS). PATIENTS AND METHODS: The technical evaluation of localizers consisted of series of geometric tests on four commercial systems. Clinical evaluation included the development of a laboratory CAS system using a markerless, skin surface registration method. This was based on a standard optical digitizing system (Flashpoint 5000), which eliminates the need for the second CT scan, which is normally performed specifically to process the position of the fiducial markers. Global accuracy was then evaluated on 20 patients by subjective and visual comparison when placing a calibrated pointer on anatomical landmarks. RESULTS: The results of the technical study indicate that the four commercial systems tested have levels of inaccuracy deemed acceptable for most CAS applications, including ENT surgery. The clinical study obtained a registration and calibration accuracy of less than 1.5 mm in 89.2% (SD = 0.20 mm) of the cases studied. Our markerless skin surface points registration method is reliable, and allows patient head movements during the procedure. The accuracy tests performed show that this type of system can be used for ENT surgery with satisfaction. CONCLUSION: CAS systems enable the surgeon to have a more thorough understanding of the complicated anatomy of paranasal sinuses, and may be especially helpful in revision surgery when normal anatomic landmarks are lacking. Further studies are necessary in FESS to improve the CAS systems that are currently available, and to determine whether these systems can minimize the overall risk of complications.
Grimer RJ, et al. Hindquarter amputation: is it still needed and what are the outcomes? Bone Joint J. 2013;95-B(1):127–31. A total of 157 hindquarter amputations were carried out in our institution during the last 30 years. We have investigated the reasons why this procedure is still required and the outcome. This operation was used as treatment for 13% of all pelvic bone sarcomas. It was curative in 140 and palliative in 17, usually to relieve pain. There were 90 primary procedures (57%) with the remaining 67 following the failure of previous operations to control the disease locally. The indication for amputation in primary disease was for large tumours for which limb-salvage surgery was no longer feasible. The peri-operative mortality was 1.3% (n = 2) and major complications of wound healing or infection arose in 71 (45%) patients. The survival at five years after hindquarter amputation with the intent to cure was 45%, and at ten years 38%. Local recurrence occurred in 23 patients (15%). Phantom pain was a significant problem, and only 20% used their prosthesis regularly. Functional scores were a mean of 57%. With careful patient selection the oncological results and functional outcomes of hindquarter amputation justify its continued use.
Delloye C, et al. Pelvic reconstruction with a structural pelvic allograft after resection of a malignant bone tumor. J Bone Joint Surg Am. 2007;89(3):579–87. BACKGROUND: Reconstruction of the pelvic arch after resection of a malignant pelvic tumor remains a major surgical challenge because of the high rate of associated complications. The purpose of this investigation was to assess the functional outcome and complication rate following treatment with a bone allograft to reconstruct the pelvis. METHODS: Twenty-four consecutive patients underwent excision of a malignant pelvic bone tumor and reconstruction with a pelvic bone allograft. The living patients were followed for a minimum of twenty-four months. There were nineteen primary malignant bone tumors, sixteen of which were high-grade sarcomas, and there were five isolated metastases. Patients were examined clinically and radiographically and were assessed functionally with the Musculoskeletal Tumor Society score. RESULTS: The mean age of the patients at the time of the index surgery was thirty-four years, and the mean duration of follow-up was forty-one months. Eighteen of the twenty-four resections involved the periacetabular area and were followed by reconstruction either with a hip prosthesis (thirteen) or with an osteochondral allograft alone (five). The six other resections involved the iliac bone. All patients received a massive bone allograft that had been sterilely procured without secondary irradiation. At the time of our last evaluation, eight patients were alive and free of disease. Seven patients had a local recurrence. Neurological deficits were present in six patients, and three had a deep infection. Nonunion of three of the sixteen allografts that could be evaluated was observed. Neither graft fracture nor lysis was observed. Eleven patients underwent surgical revision, with nine of these revisions related to the reconstruction. The average Musculoskeletal Tumor Society score at the time of the latest follow-up was 73% of the maximal possible score. The average score was 82% for the eleven patients with an age of less than twenty years at the time of the index procedure and 65% for the thirteen older patients. Ten patients walked without any assistive device, and five of them had normal function with no or only a slight limp. CONCLUSIONS: Pelvic reconstruction after a limb-sparing resection is associated with a high risk of surgical complications and usually should be reserved for patients with a primary bone sarcoma. A pelvic allograft can restore the anatomy and provide good functional results, especially in young patients. Nonunion was the most common allograft-related complication.
Carter TJ, et al. Application of soft tissue modelling to image-guided surgery. Med Eng Phys. 2005;27(10):893–909. The deformation of soft tissue compromises the accuracy of image-guided surgery based on preoperative images, and restricts its applicability to surgery on or near bony structures. One way to overcome these limitations is to combine biomechanical models with sparse intraoperative data, in order to realistically warp the preoperative image to match the surgical situation. We detail the process of biomechanical modelling in the context of image-guided surgery. We focus in particular on the finite element method, which is shown to be a promising approach, and review the constitutive relationships which have been suggested for representing tissue during surgery. Appropriate intraoperative measurements are required to constrain the deformation, and we discuss the potential of the modalities which have been applied to this task. This technology is on the verge of transition into clinical practice, where it promises to increase the guidance accuracy and facilitate less invasive interventions. We describe here how soft tissue modelling techniques have been applied to image-guided surgery applications.
Sugano N. Computer-assisted orthopaedic surgery and robotic surgery in total hip arthroplasty. Clin Orthop Surg. 2013;5(1):1–9. Various systems of computer-assisted orthopaedic surgery (CAOS) in total hip arthroplasty (THA) were reviewed. The first clinically applied system was an active robotic system (ROBODOC), which performed femoral implant cavity preparation as programmed preoperatively. Several reports on cementless THA with ROBODOC showed better stem alignment and less variance in limb-length inequality on radiographic evaluation, less incidence of pulmonary embolic events on transesophageal cardioechogram, and less stress shielding on the dual energy X-ray absorptiometry analysis than conventional manual methods. On the other hand, some studies raise issues with active systems, including a steep learning curve, muscle and nerve damage, and technical complications, such as a procedure stop due to a bone motion during cutting, requiring re-registration and registration failure. Semi-active robotic systems, such as Acrobot and Rio, were developed for ease of surgeon acceptance. The drill bit at the tip of the robotic arm is moved by a surgeon’s hand, but it does not move outside of a milling path boundary, which is defined according to three-dimensional (3D) image-based preoperative planning. However, there are still few reports on THA with these semi-active systems. Thanks to the advancements in 3D sensor technology, navigation systems were developed. Navigation is a passive system, which does not perform any actions on patients. It only provides information and guidance to the surgeon who still uses conventional tools to perform the surgery. There are three types of navigation: computed tomography (CT)-based navigation, imageless navigation, and fluoro-navigation. CT-based navigation is the most accurate, but the preoperative planning on CT images takes time that increases cost and radiation exposure. Imageless navigation does not use CT images, but its accuracy depends on the technique of landmark pointing, and it does not take into account the individual uniqueness of the anatomy. Fluoroscopic navigation is good for trauma and spine surgeries, but its benefits are limited in the hip and knee reconstruction surgeries. Several studies have shown that the cup alignment with navigation is more precise than that of the conventional mechanical instruments, and that it is useful for optimizing limb length, range of motion, and stability. Recently, patient specific templates, based on CT images, have attracted attention and some early reports on cup placement, and resurfacing showed improved accuracy of the procedures. These various CAOS systems have pros and cons. Nonetheless, CAOS is a useful tool to help surgeons perform accurately what surgeons want to do in order to better achieve their clinical objectives. Thus, it is important that the surgeon fully understands what he or she should be trying to achieve in THA for each patient.
Khan F, et al. Haptic robot-assisted surgery improves accuracy of wide resection of bone tumors: a pilot study. Clin Orthop Relat Res. 2013;471(3):851–9. BACKGROUND: Accurate reproduction of the preoperative plan at the time of surgery is critical for wide resection of primary bone tumors. Robotic technology can potentially help the surgeon reproduce a given preoperative plan, but yielding control of cutting instruments to a robot introduces potentially serious complications. We developed a novel passive (“haptics”) robot-assisted resection technique for primary bone sarcomas that takes advantage of robotic accuracy while still leaving control of the cutting instrument in the hands of the surgeon. QUESTIONS/PURPOSES: We asked whether this technique would enable a preoperative resection plan to be reproduced more accurately than a standard manual technique. METHODS: A joint-sparing hemimetaphyseal resection was precisely outlined on the three-dimensionally reconstructed image of a representative Sawbones femur. The indicated resection was performed on 12 Sawbones specimens using the standard manual technique on six specimens and the haptic robotic technique on six specimens. Postresection images were quantitatively analyzed to determine the accuracy of the resections compared to the preoperative plan, which included measuring the maximum linear deviation of the cuts from the preoperative plan and the angular deviation of the resection planes from the target planes. RESULTS: Compared with the manual technique, the robotic technique resulted in a mean improvement of 7.8 mm of maximum linear deviation from the preoperative plan and 7.9 degrees improvement in pitch and 4.6 degrees improvement in roll for the angular deviation from the target planes. CONCLUSIONS: The haptic robot-assisted technique improved the accuracy of simulated wide resections of bone tumors compared with manual techniques. CLINICAL RELEVANCE: Haptic robot-assisted technology has the potential to enhance primary bone tumor resection. Further bench and clinical studies, including comparisons with recently introduced computer navigation technology, are warranted.
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Joyce, D.M. (2017). Computer Navigation in the Sacrum. In: Ruggieri, P., Angelini, A., Vanel, D., Picci, P. (eds) Tumors of the Sacrum. Springer, Cham. https://doi.org/10.1007/978-3-319-51202-0_22
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