Long-term outcomes of primary constrained condylar knee arthroplasty

AbstractBackgroundAlthough constrained condylar knee (CCK) inserts are widely used for total knee arthroplasty (TKA), their long-term outcomes remain unclear. We sought to evaluate patients with at least 10 years’ follow-up after CCK TKA to identify potential adverse events (osteolysis, loosening, constraint-mechanism failure), assess functional outcomes with special emphasis on range of motion, and determine prosthesis survival.HypothesisIncreasing constraint by implantation of a CCK insert does not increase the long-term frequencies of osteolysis or mechanical loosening.Material and methodsWe studied 43 knees after Legacy® CCK TKA. The indication was severe deformity (n=20), pre-operative laxity (n=6), or failure to achieve intra-operative balancing (n=17). There were 41 patients with a mean age of 66 years (21–88). A history of one or more surgical procedures was noted for 27 (63%) knees. Outcome measures were the Hospital for Special Surgery (HSS) knee score, Knee Society Score (KSS), and change in the hip-knee-ankle (HKA) angle. Prosthesis survival was assessed using revision surgery for any reason or for reasons other than infection as the censoring criterion.ResultsComplications other than venous thrombosis occurred in 16% of patients, including 3 who required revision surgery (septic loosening, n=2; and major instability in a patient with ipsilateral hip arthrodesis). No cases of osteolysis or aseptic loosening were recorded. Mean follow-up was 12.7 years (range, 10–14). At last follow-up, the HSS score had improved from 53 (26–83) pre-operatively to 80 (55–93), the KSS knee component from 42 (16–77) to 90 (77–99), and the KSS function component from 31 (0–80) to 61 (10–90) (P