RESULTS AT 9.5 YEARS FOLLOW UP OF 122 TOTAL KNEE PROSTHESIS BASED ON A LIGAMENT TENSOR AND DEPENDENT CUTS

Abstract

Results and longevity of total knee arthroplasty depend on the correction of axis of the lower limb and the stability of the prosthesis. Faithful to the principle of dependent cuts, our goal was to obtain two equal correlated, rectangular extension and flexion gaps using a ligament balancing tensor called CORES^® (Stryker^®).

Material and Methods: We retrospectively studied the results of a continuous series of 122 total knee arthroplasties (Jade^®, Stryker^®) implanted by only one operator, between December 1994 and 1997. The mean follow-up is 9,5 years. Tibial plateaus were slip and fixed, with or without conservation of the posterior cruciate ligament. Mean patient age at implantation was 71,2 years. 94% had osteoarthritis and 6% rheumatoid disease. The mean preoperative IKS score was 23,4 and the IKS function score was 42,6. 16% of knees were aligned normally, according to the IKS criteria, 24% presented valgus > 4°, and 60% presented varus > 3°. Patella was centred (AA’ distance < 3mm) in 65% of cases and not tilted (alpha angle< 5°) in 41% of cases. There were 22% antero-medial and 78% antero-lateral with ATT eversion approaches. All tibial and femoral components were cemented. Resurfacing patella was not the rule (5%). Clinical outcome was assessed with the IKS score and radiological outcome with the IKS criteria.

Results: There were no early complications. At follow up, the mean IKS knee score was 90 points with mean motion 109°. Mean IKS function was 85 points. 82% of the knees were aligned (HKA angle between 177° and 183°), 7% in varus, and 11% in valgus. Patella position was centered in 80% of cases, and tilted in 8%. No patellar dislocation was observed. Radiolucent lines were observed in 20% of the tibial components, without aseptic loosening. 3% of the femoral component presented radiolucent line, and one was symptomatic. Four TKA were removed at ten and eleven years, corresponding to three deep haematogenous infections and one aseptic loosening (a young man with haemophilic arthritis). Arthroplasty survival rate was 95% at 9,5 years (Kaplan-Meier method), considering all reasons for removal, and 99,4% for removal for aseptic loosening with 95% confidence interval.

Discussion: Since a well-balanced distribution of medial and lateral contact forces avoids overload of one compartment and thus premature wear, knee imbalance assessment is a key point in TKA. This method allows ongoing intraoperative assessment of the angular and rotational correction, bone defect, as well as bone resection levels.

Conclusion: To our knowledge, our study report the first results at 9,5 years of a TKA based on dependent femoral cuts using a ligament tensor. This confirms the durability and longevity of this model of prosthesis, and the accuracy of the method.