Range of flexion after primary TKA: the effect of soft tissue release and implant design.

Range of motion following total knee arthroplasty (TKA) is a crucial measure of clinical outcome. The purpose of this randomized, controlled study was to determine which factors are predictive of postoperative range of flexion. Fifty-six patients received either a standard or a high-flexion design NexGen Legacy Posterior-Stabilized TKA (Zimmer, Warsaw, Indiana). The relationship between preoperative flexion, intraoperative flexion, and range of flexion 1 year postoperatively was determined. The influence of soft tissue release and the type of femoral component was also investigated. A significant correlation existed between preoperative flexion, intraoperative flexion, and maximum flexion 1 year postoperatively. Patients who had a preoperative range of flexion less than the mean range of flexion for the overall group gained flexion, whereas patients with a preoperative range of flexion greater than the mean range of flexion lost flexion. The degree of soft tissue release performed and the type of implant used had no influence on maximum flexion at 1 year. The principal predictive factor of postoperative range of flexion, regardless of the degree of soft tissue release or implant design, is the preoperative and intraoperative range of flexion.