Abstract
Background
Kinematically aligned TKA restores function by aligning the femoral and tibial components to the normal or prearthritic joint lines of the knee. However, aligning the components to the joint lines of the normal knee also aligns the tibial component in varus, creating concern that varus alignment might result in poor function and early catastrophic failure.
Questions/Purposes
We therefore determined whether function and the incidence of catastrophic failure were different when the tibial component, knee, and limb alignment were in a specified normal range, varus outlier, or valgus outlier.
Methods
We prospectively followed all 198 patients (214 knees) who underwent TKAs between February and October 2008. We treated each knee in this cohort of patients with a kinematically aligned, cruciate-retaining prosthesis implanted using patient-specific guides. From a long-leg scanogram, we measured and categorized alignment of the tibial component as in range (≤ 0°) or a varus outlier (> 0°), alignment of the knee as in range (between −2.5° to −7.4° valgus) or a varus (> −2.5°) or valgus (< −7.4°) outlier, and alignment of the limb as in range (0° ± 3°) or a varus (> 3°) or valgus (< −3°) outlier. We assessed function using the Oxford Knee Score and WOMAC™ score, and reported catastrophic failure as the incidence of revision attributable to loosening, wear, and instability of the femoral or tibial components. The minimum followup was 31 months (mean, 38 months; range, 31–43 months).
Results
The mean Oxford Knee Score of 43 and WOMAC™ score of 92 were similar between the three alignment categories. The incidence of catastrophic failure in each alignment category was zero.
Conclusions
Kinematically aligned TKA restores function without catastrophic failure regardless of the alignment category. Because 75% of patients had their tibial component categorized as a varus outlier and also had high function and a zero incidence of catastrophic failure, the concern that kinematic alignment compromises function and places the components at a high risk for catastrophic failure is unfounded and should be of interest to surgeons committed to cutting the tibia perpendicular to the mechanical axis of the tibia.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
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Acknowledgments
We thank the imaging department and technicians at Methodist Hospital for performing the CT scanograms.
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One of the authors certifies that he (KTK) is an employee of Stryker Orthopedics (Mahwah, NJ, USA). One author (SMH) is a consultant for Stryker Orthopedics (Mahwah, NJ, USA). All other authors certify that he or she, or a member of his or her immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.
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Each author certifies that his or her institution has approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.
This work was performed at Methodist Hospital, Sacramento, CA, USA, and at the Department of Mechanical Engineering, University of California at Davis, Davis, CA, USA.
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Howell, S.M., Howell, S.J., Kuznik, K.T. et al. Does A Kinematically Aligned Total Knee Arthroplasty Restore Function Without Failure Regardless of Alignment Category?. Clin Orthop Relat Res 471, 1000–1007 (2013). https://doi.org/10.1007/s11999-012-2613-z
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DOI: https://doi.org/10.1007/s11999-012-2613-z