Joint Gap in Mid-Flexion Is Not a Predictor of Postoperative Flexion Angle After Total Knee Arthroplasty

Postoperative knee flexion angle is one of the most important outcomes of total knee arthroplasty (TKA). Intraoperative ligament balancing may affect the postoperative range of motion of the knee. However, the relationship between intraoperative ligament balancing and postoperative flexion angle was still controversial. The purpose of this study was to determine whether intraoperative joint gap affects postoperative knee flexion angle or not.

Prospective multicenter study of 246 knees with varus osteoarthritis undergoing a posterior-stabilized, mobile-bearing TKA was performed. The joint gap before implantation and after implantation was measured. The joint gap after implantation was measured using a specially designed tensor device with the same shape of a total knee prosthesis at 0°, 30°, 60°, 90°, 120°, and 145° of flexion with the reduction of the patellofemoral joint. Stepwise multiple regression analysis was conducted to determine the predictors of the flexion angle of the knee after the operation.

Predictors were identified in the following 3 categories: (1) preoperative flexion angle, (2) intraoperative flexion angle, and (3) joint gap looseness at 120° of flexion (joint gap after implantation at 120° of flexion - joint gap after implantation at 0° of flexion) (R = 0.472, P < .01).

Flexion angle after TKA was not affected by the flexion joint gap looseness before implantation and the joint gap looseness after implantation from 30° to 90° of flexion. Surgeons should notice that joint gap looseness in mid-flexion range did not increase the postoperative knee flexion angle.