CT/X-Ray-Guided Augmentation Techniques in Lumbar Spine
Augmentation techniques (AT) include different percutaneous mini-invasive procedures such as vertebroplasty (VP) and assisted technique (AT) (kyphoplasty or kyphoplasty-like technique) for the treatment of symptomatic vertebral compression fractures (VCFs) due to osteoporosis diseases, primary or secondary vertebral tumors, and vertebral trauma. The major target of all those techniques is pain relief, thanks to the simple cement injection (polymethylmethacrylate, PMMA) in the collapsed or abnormal soma stabilizing the movements of the trabecular and spongious microfractures (responsible for the pain), making more compact and resistant the vertebral body, improving life quality. While VP consists in the simple cement injection, AT combines this analgesic and vertebral consolidation effect with the restoration of the physiological height of the collapsed vertebral body, reducing the kyphotic deformity and improving vertebral statics and trying to restore the physiologic curvature and biomechanics. Reduction of the kyphotic deformity is the major target of all AT, thanks to the capacity of the system to restore the vertebral height. The aim of this chapter is to explain indication/contraindication treatment, limits, and benefits of the different devices developed by the industry for obtaining vertebral augmentation effect.
KeywordsVertebroplasty Assisted technique-vertebroplasty Kyphoplasty Kyphoplasty-like technique Vertebral compression fracture Spinal metastasis Hemangioma Osteoporosis vertebral fracture Polymethylmethacrylate
Augmentation techniques (AT) include different percutaneous mini-invasive procedures such as vertebroplasty (VP) and assisted technique (AT) (kyphoplasty or kyphoplasty-like technique) for the treatment of symptomatic vertebral compression fractures (VCFs) due to osteoporosis diseases, primary or secondary vertebral tumors, and vertebral trauma .
The major target of all those techniques is pain relief, thanks to the simple cement injection (polymethylmethacrylate, PMMA) in the collapsed or abnormal soma stabilizing the movements of the trabecular and spongious microfractures (responsible for the pain), making more compact and resistant the vertebral body, improving life quality .
While VP consists in the simple cement injection, AT combines this analgesic and vertebral consolidation effect with the restoration of the physiological height of the collapsed vertebral body, reducing the kyphotic deformity and improving vertebral statics and trying to restore the physiologic curvature and biomechanics.
Reduction of the kyphotic deformity is the major target of all AT, thanks to the capacity of the system to restore the vertebral height . Right now, many different devices have been developed by the industry obtaining a vertebral augmentation effect.
In 1998, balloon kyphoplasty technique was the first one to be developed consisting in delivering cement—PMMA—into a fractured vertebral body under fluoroscopic guidance after creation of a cavity within the vertebral body by a dedicated expandable balloon [3, 4].
Vertebral body stenting is another augmentation device where two metallic stents are placed in the vertebral body by bipeduncular approach creating a cavity where the cement can be injected in low-pressure condition .
Metallic system placed into the vertebral body obtaining vertebral height restoration.
Even a recent meta-analysis has shown no statistical difference in terms of pain relief between VP and AT.
5.2 Patient Selection Criteria
Patient selection criteria are based on clinical pain evaluation associated to imaging correlation based mostly on MR abnormality .
Pain onset is an important parameter to consider because it can help in deciding whether the patient should be treated or not .
Patient affected by symptomatic VCF with intense, non-radicular, back pain on midline line, refractory to conventional medical treatment since 6–8 weeks (bracing, analgesic and bed rest) and strongly exacerbated by digital palpation of the spinous process of the affected vertebra, represent the first line of indication to treat by augmentation technique.
Pain syndrome can be evaluated by different methods such as the Visual Analog Scale (VAS), the Oswestry Disability Index (ODI), SF-36, and Roland-Morris Disability Questionnaire .
At clinical evaluation, it corresponds to an imaging pattern: VCF with more/less kyphosis deformation and hyperintensity signal alteration on T2-STIR MR sequence, corresponding to bone marrow edema and unhealed fracture .
In case of known MR contraindication, bone nuclear medicine scan is requested showing an unspecific vertebral body intense uptake requiring a MDCT correlation to confirm the diagnosis of porotic VCF.
MDCT with MPR is useful to differential benign porotic fracture versus neoplastic one, searching for the intravertebral vacuum sign or soft tissue abnormality.
In case of uncertain pattern on MDCT or MR morphology or signal intensity, a bone biopsy is mandatory to understand the nature of the lesion prior to perform AT.
Painless VCF, diffuse non-focal pain without MR evidence of altered trabecular bone signal, systemic or local infections, uncorrectable coagulation disorders, and allergy to PMMA are the exclusion criteria for AT .
Patient with porotic fracture on MR imaging with hyperintensity on T2-STIR sequence but without back pain is not indicated to the treatment. Patient with spine pain syndrome, VCF, and visibility on MR of hyperintensity on T2-STIR sequence is the one with the best and correct indication to perform VP .
For traumatic VCF at thoracolumbar level, AT is primarily indicated to achieve height augmentation and kyphosis reduction, and the treatment must be performed as soon as possible to avoid bone sclerotic response, especially in a young patient 2 weeks after trauma. According to Magerl classification—where VCFs are divided into three main categories according to trauma force, namely, (a) compression injury, (b) distraction injury, and (c) rotation injury—a main nonsurgical mini-invasive treatment is indicated for type A1 .
The management and indication to mini-invasive treatment at lumbar level in patients affected by neoplastic VCFs require a complete team and multidisciplinary approach between interventional neuroradiologist, radiotherapist, oncologist, neurosurgeons, and pain therapist.
The concept of oncologic instability is different compared to the traumatic one.
The aim of the treatment is antalgic effect and vertebral stabilization preventing also vertebral instability in case of bone disruption.
Malignant primary tumors or metastases, in fact, can disrupt the normal biomechanics of the spine via bone destruction or deformity resulting in a decrease in its load-bearing capacity. The load-bearing capacity is determined by a number of factors, including tumor size as well as cross-sectional area of the intact body and its bone mineral density. Krishaney  divided the vertebral body in 27 similar cubes. When the destruction of all the cubes within 1/3 of the axial soma occurs, it creates an instability due to a deficit of the anterior and middle column. In case of sagittal destruction only, the spinal stability is maintained and not altered. The location of the tumor (and hence bone destruction) within the vertebral body may also play a role in the patient’s risk of fracture and instability. There is a distinct discrepancy between the thoracic and thoracolumbar or lumbar spine and spinal oncological instability. In fact, according to Taneichi, the most important risk factor of fracture of thoracic spine instability is the disruption of costovertebral joint and, only after, the vertebral body. The costovertebral joint and all thoracic muscular structure increase the stiffness and the resistance of the thoracic spine, maintaining the spinal biomechanics. In fact, at the thoracic level, it has been demonstrated that it is necessary to have about 50–60% vertebral disruption to have pathologic vertebral fracture and instability versus 35–40% at thoracolumbar and lumbar levels .
Spinal oncological instability classification  is based on patient symptoms and imaging criteria of the spine, and it is possible to predict the spine stability of neoplastic lesions deciding the indication of mini-invasive treatment. The classification system includes global spinal location of the tumor, type and presence of pain, bone lesion quality, spinal alignment, extent of vertebral body collapse, and posterolateral spinal element involvement.
By the combinations of all these elements, a score —The Spinal Instability Neoplastic Score—comes out that can guide clinicians in identifying when patients with neoplastic disease of the spine may benefit from surgical treatment. A score between 0 and 6 results in spinal stability, between 7 and 12 results in possible instability, and between 13 and 18 results in oncological instability.
Stability treatment, especially for the spinal metastasis
All the procedures can be performed under local anesthesia or neuroleptanalgesia using fluoro-CT or fluoroscopy guidance in patient mostly in prone position.
To avoid cement leakage during injection, it is important to use high-quality fluoroscopy to achieve a complete anatomical control of the spine.
Bipeduncular approach is mandatory to perform assisted techniques and to reduce vertebral kyphosis deformation.
The technique to reach the peduncle is simple and easy to perform: in PA view, the first step is to archive the spinous process on the midline, and the second step is to see both vertebral endplates completely superimposed.
It is also possible to give a little obliquity to the projection to reach better the center of the vertebral body, especially in case you want to perform a simple VP with mono-lateral approach.
Once the correct imaging approach is obtained, a local anesthesia can be performed few centimeters laterally to the peduncle. Once it has been done, the needle is positioned in the vertebral body through a trans-peduncular approach reaching its posterior wall.
In AP view, the medial margin of the peduncle is an absolute anatomical landmark to check before to pass over the posterior wall of the vertebral body in LL view.
A metallic drill can also be used to model the trabecular bone such as other osteotomy cannula to lead the insertion of the balloon tamp or metallic implant without problems.
The cement must be injected through a slow injection system such as a bone filler or through 1 mL syringe to inject a quite high-viscosity cement, with less disk and venous leakage  and under continuous fluoroscopy control.
When the vertebral body is filled by cement with homogenous distribution, the procedure is concluded.
The safety and the efficacy of those techniques are well established by several studies and trials [14, 15, 16, 17, 18], analyzing the outcome of technique about pain’s reduction and kyphosis correction and complications, such as cement leakage, disk leakage, pulmonary embolism, and new vertebral fractures at adjacent or distant vertebral body.
The Fracture Reduction Evaluation (FREE)  multicenter randomized controlled trial compared the efficacy and safety of balloon kyphoplasty (149 patients for BKP-group) to nonsurgical management (151 patients for NSM group) over 24 months in patients with painful vertebral compression fractures (VCF). Compared with NSM, the BKP group had greater improvements in SF-36 physical component summary (PCS) scores at 1 month (5.35 points; 95% CI, 3.41–7.30; P < 0.0001) and when averaged across the 24 months (overall treatment effect 2.71 points; 95% CI, 1.34–4.09; P = 0.0001). The BKP group also had greater functionality by assessing timed up and go (overall treatment effect—2.49 s; 95% CI, −0.82 to −4.15; P = 0.0036). At 24 months, the change in index fracture kyphotic angulation was statistically significantly improved in the kyphoplasty group (average 3.13° of correction for kyphoplasty compared with 0.82° in the control, P = 0.003). Number of baseline prevalent fractures (P = 0.0003) and treatment assignment (P = 0.004) are the most predictive variables for PCS improvement; however, in patients who underwent BKP, there may also be a link with kyphotic angulation. In BKP, the highest quart for kyphotic angulation correction had higher PCS improvement (13.4 points) than the quart having lowest correction of angulation (7.40 points, P = 0.0146 for difference). The most common adverse events temporally related to surgery (i.e., within 30 days) were back pain (20 BKP, 11 NSM), new VCF (11 BKP, 7 NSM), nausea/vomiting (12 BKP, 4 NSM), and urinary tract infection (10 BKP, 3 NSM).
The Cancer Patient Fracture Evaluation (CAFE) study , a multicenter randomized controlled trial, compared balloon kyphoplasty (70 patients) versus nonsurgical fracture management (64 patients) for treatment of painful VCFs in patients with spine metastasis and one to three painful VCFs. The primary endpoint was back-specific functional status measured by the Roland-Morris Disability Questionnaire (RDQ) score at 1 month. The mean RDQ score in the kyphoplasty group changed from 17.6 at baseline to 9.1 at 1 month (mean change −8.3 points, 95% CI −6.4 to −10.2; P < 0.0001). The mean score in the control group changed from 18.2 to 18.0 (mean change 0.1 points; 95% CI −0.8 to 1.0; P = 0.83). At 1 month, the kyphoplasty treatment effect for RDQ was −8.4 points (95% CI −7.6 to −9.2; P < 0.0001). The most common adverse events within the first month were back pain (4 of 70 in the BK group and 5 of 64 in the control group) and symptomatic vertebral fracture (2 and 3, respectively). This trial showed that BK is an effective and safe treatment that rapidly reduces pain and improves function.
Eight nonrandomized trials of 422 patients and 1 randomized trial of 100 patients compared VP and KP . In all eight studies, VP and KP reduced pain and improved QOL to a similar extent. Only one nonrandomized study suggested that KP is superior at relieving pain and improving QOL, with differences maintained over 1-year follow-up. KP was more effective at reducing the kyphotic wedge and increasing vertebral height. The largest meta-analysis available concluded that BKP decreased pain to a greater degree than VP (5.07 vs. 4.55 points on the VAS) and resulted in significantly better improvement in quality of life than both VP and NSM . This meta-analysis includes all the level I data available on vertebral augmentation, and given this large amount of high-quality data, it is our contention that there is more than adequate information upon which to base treatment decisions. Both procedures are safe, with no reported complications .
The risk of cement leakage is certainly lower with AT, thanks to low-pressure condition of cement injection versus VP, while the incidence of new vertebral fractured to adjacent or distant metamer is the same, mostly related to the porotic disease itself [7, 22].
Many studies suggested that AT produces a greater improvement in daily activity, physical function, and pain relief when compared to optimal medical management for osteoporotic VCFs by 6 months after intervention, while there is poor-quality evidence that AT results in greater pain relief for tumor-associated VCFs .
No significant difference is demonstrated between VP and KP in short- and long-term pain and disability, complications, and anatomic outcomes .
KP and VP are both safe and effective surgical procedures in treating osteoporotic VCF. KP has a similar long-term pain relief, function outcome, and new adjacent VCFs in comparison to VP. KP is superior to VP for the injected cement volume, the short-term pain relief, the improvement of short- and long-term kyphotic angle, and lower cement leakage rate. However, KP has a longer operation time and higher material cost than VP .
For traumatic patient, treated by AT, generally pain relief is achieved in the 90–95% of patients affected by A1 and A3 Magerl vertebral fractures, treated within 3 months from the trauma, depending on the type of fracture, and an increase in vertebral body height sufficient to allow early mobilization of the patient and restoration of the physiological distribution of postural forces avoiding bed rest and orthosis devices .
Vertebral augmentation is a well-established therapy for the treatment of spine pain due to porotic, neoplastic, and traumatic fractures.
Clinical history and a correct diagnostic approach with MR, CT, and nuclear medicine bone scan are mandatory in patient selection to obtain the best clinical results at 1-, 3-, and 12-month follow-up.
The rate of complications is very low and is related to the condition of the metamer to be treated, to operator experience, and fluoroscopy quality, and it is useful to remind that those complications are very often completely asymptomatic.
New materials with high-viscosity cement are now available to reduce this complications even with low cost.
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