Kinematically aligned total knee arthroplasty (KA TKA) strives to restore the native distal and posterior joint lines of the femur. Because the joint lines of a virtually planned femoral component on the native femur can serve as surrogates of those of the native femur, the present study determined position and orientation deviations of the femoral joint lines following calipered KA TKA from virtually planned joint lines and whether these alignment deviations affect clinical outcomes. Our hypotheses were that the alignment deviations for most knees would be less than 2 mm and/or 2° and that larger alignment deviations would not be associated with lower clinical outcome scores.
A review of lower extremity CT scanograms and CT scans of the knee identified 36 patients treated with calipered KA TKA in one limb and no other skeletal deformities in either limb. 3D models of the operated femur with the implanted femoral component and the native femur were created. The articular surfaces of a 3D model of the implanted femoral component in the TKA knee were shape-matched to the condyles of the native femur to create a virtual plan. The shape-matched femoral component served as a reference from which to determine alignment deviations of the femoral component implanted in the ipsilateral femur. The Forgotten Joint Score (FJS) and Oxford Knee Score (OKS) were obtained at an average of 20 months.
For proximal–distal and anterior–posterior positions and varus–valgus and internal–external orientations of the femoral component, the root mean square deviations from the planned joint lines ranged from 1.4 to 1.5 (mm or degrees). The mean differences ranged from − 0.1 to 0.2 (mm or degrees) indicating an absence of systematic alignment deviations. The proportion of knees with joint lines within ± 2 mm and ± 2° of the joint lines of virtually planned knees ranged from 83 to 92%. For the FJS and OKS, the median values were 79 (out of 100) and 45 (out of 48), respectively, and there were no significant correlations between deviations in the positions and orientations and either the FJS or the OKS.
Alignment deviations were bounded by 2 mm and 2° for most knees, which previous biomechanical studies have shown reduce the risks of stiffness, loss of extension, loss of flexion, and tibial compartment forces higher than those of the native knee. Moreover, because median FJS and OKS were relatively high, and because larger alignment deviations did not correlate with lower outcome scores, deviations did not affect clinical outcomes. These results validate calipered KA TKA as a surgical technique which closely restores the distal and posterior femoral joint lines to those planned and achieves concomitant high patient-reported outcome scores. Thus, surgeons can use the calipered KA TKA technique with confidence that the surgical alignment goal will be satisfied with sufficient accuracy that high patient-reported outcomes are achieved.
Level of evidence
This is a preview of subscription content, log in to check access.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
Tax calculation will be finalised during checkout.
Altman DG (1991) Practical statistics for medical research. Chapman & Hall/CRC, London
Anderl W, Pauzenberger L, Kolblinger R, Kiesselbach G, Brandl G, Laky B, Kriegleder B, Heuberer P, Schwameis E (2016) Patient-specific instrumentation improved mechanical alignment, while early clinical outcome was comparable to conventional instrumentation in TKA. Knee Surg Sports Traumatol Arthrosc 24(1):102–111
Bartlett JW, Frost C (2008) Reliability, repeatability and reproducibility: analysis of measurement errors in continuous variables. Ultrasound Obstet Gynecol 31(4):466–475
Catani F, Biasca N, Ensini A, Leardini A, Bianchi L, Digennaro V, Giannini S (2008) Alignment deviation between bone resection and final implant positioning in computer-navigated total knee arthroplasty. J Bone Joint Surg Am 90(4):765–771
Clement ND, MacDonald D, Simpson AH (2014) The minimal clinically important difference in the Oxford knee score and Short Form 12 score after total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 22(8):1933–1939
Dimitriou D, Tsai TY, Yue B, Rubash HE, Kwon YM, Li G (2016) Side-to-side variation in normal femoral morphology: 3D CT analysis of 122 femurs. Orthop Traumatol Surg Res 102(1):91–97
Eckhoff DG, Jacofsky DJ, Springer BD, Dunbar M, Cherian JJ, Elmallah RK, Mont MA, Greene KA (2016) Bilateral symmetrical comparison of femoral and tibial anatomic features. J Arthroplasty 31(5):1083–1090
Hess S, Moser LB, Amsler F, Behrend H, Hirschmann MT (2019) Highly variable coronal tibial and femoral alignment in osteoarthritic knees: a systematic review. Knee Surg Sports Traumatol Arthrosc 27(5):1368–1377
Hirschmann MT, Moser LB, Amsler F, Behrend H, Leclerq V, Hess S (2019) Functional knee phenotypes: a novel classification for phenotyping the coronal lower limb alignment based on the native alignment in young non-osteoarthritic patients. Knee Surg Sports Traumatol Arthrosc 27(5):1394–1402
Howell SM, Hull ML (2012) Kinematic alignment in total knee arthroplasty. In: Norman Scott W (ed) Insall and Scott surgery of the knee. Elsevier, Philadelphia, pp 1255–1268
Howell SM, Kuznik K, Hull ML, Siston RA (2008) Results of an initial experience with custom-fit positioning total knee arthroplasty in a series of 48 patients. Orthopedics 31(9):857–863
Howell SM, Papadopoulos S, Kuznik KT, Hull ML (2013) Accurate alignment and high function after kinematically aligned TKA performed with generic instruments. Knee Surg Sports Traumatol Arthrosc 21(10):2271–2280
Howell SM, Shelton TJ, Hull ML (2018) Implant survival and function ten years after kinematically aligned total knee arthroplasty. J Arthroplasty 33(12):3678–3684
Indrayan A (2013) Methods of clinical epidemiology. In: SARDaGMW (ed) Springer series on epidemiology and public health. Springer, Berlin. https://doi.org/10.1007/978-3-642-37131-8_2
Kassam AM, Dieppe P, Toms AD (2012) An analysis of time and money spent on investigating painful total knee replacements. Br J Med Prac 5(3):a526
Kayani B, Konan S, Huq SS, Tahmassebi J, Haddad FS (2019) Robotic-arm assisted total knee arthroplasty has a learning curve of seven cases for integration into the surgical workflow but no learning curve effect for accuracy of implant positioning. Knee Surg Sports Traumatol Arthrosc 27(4):1132–1141
Koo S, Gold G, Andriacchi T (2005) Considerations in measuring cartilage thickness using MRI: factors influencing reproducibility and accuracy. Osteoarthr Cartil 13(9):782–789
Kornaat PR, Koo S, Andriacchi TP, Bloem JL, Gold GE (2006) Comparison of quantitative cartilage measurements acquired on two 3.0T MRI systems from different manufacturers. J Magn Reson Imaging 23(5):770–773
Li G, Park SE, DeFrate LE, Schutzer ME, Ji L, Gill TJ, Rubash HE (2005) The cartilage thickness distribution in the tibiofemoral joint and its correlation with cartilage-to-cartilage contact. Clin Biomech 20(7):736–744
Lustig S, Scholes CJ, Oussedik SI, Kinzel V, Coolican MR, Parker DA (2013) Unsatisfactory accuracy as determined by computer navigation of VISIONAIRE patient-specific instrumentation for total knee arthroplasty. J Arthroplasty 28(3):469–473
Matziolis G, Krocker D, Weiss U, Tohtz S, Perka C (2007) A prospective, randomized study of computer-assisted and conventional total knee arthroplasty. Three-dimensional evaluation of implant alignment and rotation. J Bone Joint Surg Am 89(2):236–243
Moser LB, Hess S, Amsler F, Behrend H, Hirschmann MT (2019) Native non-osteoarthritic knees have a highly variable coronal alignment: a systematic review. Knee Surg Sports Traumatol Arthrosc 27(5):1359–1367
Nam D, Lin KM, Howell SM, Hull ML (2014) Femoral bone and cartilage wear is predictable at 0 degrees and 90 degrees in the osteoarthritic knee treated with total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 22(12):2975–2981
Nedopil AJ, Howell SM, Hull ML (2016) Does malrotation of the tibial and femoral components compromise function in kinematically aligned total knee arthroplasty? Orthop Clin North Am 47(1):41–50
Nedopil AJ, Singh AK, Howell SM, Hull ML (2018) Does calipered kinematically aligned TKA restore native left to right symmetry of the lower limb and improve function? J Arthroplasty 33(2):398–406
Paschos NK, Howell SM, Johnson JM, Mahfouz MR (2017) Can kinematic tibial templates assist the surgeon locating the flexion and extension plane of the knee? Knee 24(5):1006–1015
Riley J, Roth JD, Howell SM, Hull ML (2018) Increases in tibial force imbalance but not changes in tibiofemoral laxities are caused by varus–valgus malalignment of the femoral component in kinematically aligned TKA. Knee Surg Sports Traumatol Arthrosc 26(11):3238–3248
Riley J, Roth JD, Howell SM, Hull ML (2018) Internal–external malalignment of the femoral component in kinematically aligned total knee arthroplasty increases tibial force imbalance but does not change laxities of the tibiofemoral joint. Knee Surg Sports Traumatol Arthrosc 26(6):1618–1628
Riviere C, Iranpour F, Harris S, Auvinet E, Aframian A, Chabrand P, Cobb J (2017) The kinematic alignment technique for TKA reliably aligns the femoral component with the cylindrical axis. Orthop Traumatol Surg Res 103(7):1069–1073
Roth JD, Howell SM, Hull ML (2015) Native knee laxities at 0, 45, and 90 degrees of flexion and their relationship to the goal of the gap-balancing alignment method of total knee arthroplasty. J Bone Joint Surg 97-A(20):1678–1684
Shelton TJ, Howell SM, Hull ML (2018) A total knee arthroplasty is stiffer when the intraoperative tibial force is greater than the native knee. J Knee Surg 32(10):1008–1014
Shelton TJ, Howell SM, Hull ML (2019) Is there a force target that predicts early patient-reported outcomes after kinematically aligned TKA? Clin Orthop Relat Res 477(5):1200–1207
Wakelin EA, Tran L, Twiggs JG, Theodore W, Roe JP, Solomon MI, Fritsch BA, Miles BP (2018) Accurate determination of post-operative 3D component positioning in total knee arthroplasty: the AURORA protocol. J Orthop Surg Res 13(1):275
Williams DP, Blakey CM, Hadfield SG, Murray DW, Price AJ, Field RE (2013) Long-term trends in the Oxford knee score following total knee replacement. Bone Joint J 95-B(1):45–51
No funding was received for this study.
Conflict of interest
SMH is a paid consultant for THINK Surgical and Medacta, Inc. MLH receives research support from Zimmer-Biomet and Medacta, Inc.
An institutional review board approved this retrospective study (IRB 1362165-1) and the study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Nedopil, A.J., Howell, S.M. & Hull, M.L. Deviations in femoral joint lines using calipered kinematically aligned TKA from virtually planned joint lines are small and do not affect clinical outcomes. Knee Surg Sports Traumatol Arthrosc 28, 3118–3127 (2020). https://doi.org/10.1007/s00167-019-05776-w
- Total knee replacement
- Total knee arthroplasty
- Prosthetic knee
- Oxford Knee Score
- Forgotten Joint Score
- Femoral component alignment