2015 ISAKOS Biennial Congress ePoster #1412

Does Varus Alignment Adversely Affect Six Year Implant Survival and Function After Kinematically Aligned Total Knee Arthroplasty?

Stephen M. Howell, MD, Sacramento, CA UNITED STATES
Stelios Papadopoulos, BS, Sacramento, CA UNITED STATES
Kyle Kuznik, BS, Alameda, CA UNITED STATES
Lillian Ghaly, BS, Sacramento, CA UNITED STATES
Maury L. Hull, PhD, Davis, CA UNITED STATES
University California at Davis, Davis, CA, USA

FDA Status Cleared

Summary: At six year follow-up, kinematically aligned TKA has a comparable revision rate and higher function than mechanically aligned TKA, and the varus alignment of the tibial component and/or knee does not adversely affect knee function.

Abstract:

Background

Kinematically aligned total knee arthroplasty (TKA) restores the natural patient-specific angle and level of the joint line, which often requires varus alignment of the tibial component to the mechanical axis of the tibia. Because post-operative varus alignment is associated with poor function and increased failure after mechanically aligned TKA, it is important to determine whether kinematically aligned TKA negatively affects six year implant survival and function.

PURPOSE/QUESTION: We tested the hypotheses that the six-year revision-rate and function (Oxford knee score) after kinematically aligned total knee arthroplasty (TKA) are not different from reported results of mechanically aligned TKA, and that the function of patients with a varus or valgus alignment of the tibial component, knee, or limb is not different from in-range.

Methods

We prospectively followed 214 consecutive patients (219 knees) treated with cemented kinematically aligned TKA. Implant failure was revision or pending revision of any component for any reason. Function was assessed with the Oxford knee score (48 best) and WOMACTM score (100 best). We categorized tibial component alignment as in-range (= 00) or varus (>00); knee alignment as in-range (between -2.50 and -7.40), varus (>-2.50), or valgus (<-7.40); and limb alignment as in-range (00 ± 30), varus (>30), or valgus (<-30).

Results

At a mean of 6.3 years (range, 5.8-7.2 years), the implant survivorship was 97.5% and the revision-rate per 100 component years was 0.40. Three implants had been revised (deep infection [N=1], loose tibial component [N=1], and patella instability [N=1]) and 2 loose patella components were pending revision and considered failures. The average Oxford knee score was 43 and WOMACTM score was 91. The function of the 80% of tibial components, 31% of knees, and 7% of limbs aligned in varus was similar to patients aligned in-range.

Conclusions

At six-year follow-up, kinematically aligned TKA has a comparable revision rate and higher function than mechanically aligned TKA, and the varus alignment of the tibial component and/or knee does not adversely affect knee function.

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