The use of stems with constrained condylar knee (CCK) prosthesis components has been advocated both for primary and revision total knee arthroplasty (TKA). CCK “nonmodular” implants without diaphyseal stems reduce the invasion of the medullary canal, thereby reducing operative time and costs; render a subsequent revision procedure easier, and avoid possible stem pain. The present study is the first report on mid-term results of stemless CCK for primary TKA.
This cross-sectional study reviewed the outcome for 248 knees (180 patients) in which primary TKA was performed using the Exactech nonmodular CCK between 1997 and 2001. The patients had an average age of 68 years and the preoperative diagnosis was osteoarthritis in 94%. Preoperative deformity was severe (82% Ahlback grade 4–5). Valgus deformity was present in 59% and averaged 15° (7–33°). Varus deformity, present in 41% of the patients, averaged 13° (5–22°). Fifty-seven percent of the patients had multiple joint involvement (category C).
Clinical and radiological follow-up at an average of 47 months (range, 24–72 months) was obtained for 192 TKAs (148 patients). Of the total group, there were 15 deaths and 17 patients were lost to follow-up. The Knee Society score improved from 36 to 89 and the functional score from 42 to 76 postoperatively. Varus-valgus laxity improved from 11° (range: 0–30°) to 2° (range:0–6°). Nonprogressive radiolucent lines were present in 16%. Failure rate, defined as revision, was 3% (two infections, two aseptic loosenings, one broken post, and one supra-condylar femoral fracture). In six knees (3%) patello-femoral complications developed: five patellar clunks and one dislocation.
Use of a stemless “nonmodular” CCK for primary severely damaged knees demonstrated reliable mid-term results with a low complication rate.