Stephen M Howell1,2,3, Stelios Papadopoulos4,5,6,7, Kyle Kuznik4,5,6,7, Lillian R Ghaly4,5,6,7, Maury L Hull4,5,6. 1. Biomedical Engineering Graduate Group, University of California, Davis, Davis, CA, 95616, USA. sebhowell@mac.com. 2. Department of Mechanical Engineering, University of California, Davis, Davis, CA, 95616, USA. sebhowell@mac.com. 3. , 8120 Timberlake Way Ste 112, Sacramento, CA, 95823, USA. sebhowell@mac.com. 4. Biomedical Engineering Graduate Group, University of California, Davis, Davis, CA, 95616, USA. 5. Department of Mechanical Engineering, University of California, Davis, Davis, CA, 95616, USA. 6. Department of Biomedical Engineering, University of California, Davis, Davis, CA, 95616, USA. 7. , 8120 Timberlake Way Ste 112, Sacramento, CA, 95823, USA.
Abstract
PURPOSE: We report the six year implant survivorship, tibial component alignment and knee and limb function measured by the Oxford Knee Score and Western Ontario and McMaster Universities Osteoarthritis Index ((WOMAC) score after kinematically aligned total knee arthroplasty (TKA) and tested the hypothesis that varus alignment of the tibial component, knee, or limb does not adversely affect implant survival and function. METHODS: We prospectively followed 214 consecutive patients (219 knees) treated with a kinematically aligned TKA in 2007. Kaplan-Meier survival analysis and revision rate per 100 component years determined implant failure. The Oxford Knee Score (0 worst, 48 best) and WOMAC score (0 worst, 100 best) were used to measure function. We categorised tibial component alignment as in-range (≤ 0°) or varus (>0°), knee alignment as in-range (between -2.5° and -7.4°), varus (>-2.5°), or valgus (<-7.4°), and limb alignment as in-range (0° ± 3°), varus (>3°) or valgus (<-3°). RESULTS: At a mean of 6.3 years (range, 5.8-7.2), implant survivorship was 97.5 % and revision-rate per 100 component years 0.40. Three implants had been revised (deep infection one, loose tibial component one and patella instability [1); two loose patella components were pending revision and considered failures. The average Oxford Knee Score was 43 and WOMAC 91. Function of tibial components (80 %), knees (31 %) and limbs (7 %) that were aligned in varus was similar to patients aligned in-range. CONCLUSIONS: At a mean of 6.3 years after kinematically aligned TKA, varus alignment of the tibial component, knee and limb did not adversely affect implant survival or function, which supports the consideration of kinematic alignment as an alternative to mechanical alignment for performing primary TKA. Level of evidence, III; therapeutic study.
PURPOSE: We report the six year implant survivorship, tibial component alignment and knee and limb function measured by the Oxford Knee Score and Western Ontario and McMaster Universities Osteoarthritis Index ((WOMAC) score after kinematically aligned total knee arthroplasty (TKA) and tested the hypothesis that varus alignment of the tibial component, knee, or limb does not adversely affect implant survival and function. METHODS: We prospectively followed 214 consecutive patients (219 knees) treated with a kinematically aligned TKA in 2007. Kaplan-Meier survival analysis and revision rate per 100 component years determined implant failure. The Oxford Knee Score (0 worst, 48 best) and WOMAC score (0 worst, 100 best) were used to measure function. We categorised tibial component alignment as in-range (≤ 0°) or varus (>0°), knee alignment as in-range (between -2.5° and -7.4°), varus (>-2.5°), or valgus (<-7.4°), and limb alignment as in-range (0° ± 3°), varus (>3°) or valgus (<-3°). RESULTS: At a mean of 6.3 years (range, 5.8-7.2), implant survivorship was 97.5 % and revision-rate per 100 component years 0.40. Three implants had been revised (deep infection one, loose tibial component one and patella instability [1); two loose patella components were pending revision and considered failures. The average Oxford Knee Score was 43 and WOMAC 91. Function of tibial components (80 %), knees (31 %) and limbs (7 %) that were aligned in varus was similar to patients aligned in-range. CONCLUSIONS: At a mean of 6.3 years after kinematically aligned TKA, varus alignment of the tibial component, knee and limb did not adversely affect implant survival or function, which supports the consideration of kinematic alignment as an alternative to mechanical alignment for performing primary TKA. Level of evidence, III; therapeutic study.
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