High-flexion TKA in patients with a minimum of 120 degrees of pre-operative knee flexion: outcomes at six years of follow-up.

We prospectively evaluated outcomes of high-flexion total knee arthroplasty in 165 patients who had advanced arthritis with a minimum 120-degree pre-operative knee flexion, with a mean follow-up of 77 months. Patients were divided into two groups according to their ability to perform full-range (heel-to-buttock) pre-operative knee flexion (group A) and the inability to do so (group B). The overall clinical rating was "excellent" in 96% of patients and "good" in 4% of patients. Mean maximum knee flexion decreased from 137.9° to 134.8°, with no statistical difference between pre- and post-operative knee flexion. However, patients in group A had significantly decreased knee flexion (146.2° vs. 135.0°, p < 0.001), whereas patients in group B exhibited no change in knee flexion (133.7° vs. 134.7°, p = 0.14). We found that 14.7%, 36.5% and 43.0% of the studied patients could engage in kneeling, Thai polite style sitting and cross-legged sitting, respectively, with no significant differences between groups A and B. The survival rates for any reoperation and prosthesis-related problem (such as early loosening) at six years were 98.3% and 100%, respectively. At six-year follow-up in patients with well preserved pre-operative knee flexion, the high-flexion knee prosthesis provided a favourable outcome without improving knee flexion.