[Effect of posterior condylar offset on knee flexion after high-flex posterior-stabilized total knee arthroplasty]

To determine the effect of the posterior condylar offset (PCO) on intra- and post-operative knee flexion after total knee arthroplasty (TKA) using a high-flex posterior-stabilized (PS) fixed-bearing prosthesis and to discuss it's importance in femoral prosthesis design.

The clinical and radiographic materials of 100 consecutive patients (100 knees) were prospectively studied, including 50 men and 50 women, who had undergone primary NexGen LPS-Flex TKAs for end-stage osteoarthritis. All operations were performed by a single surgeon using the same operative technique between March 2005 and October 2006. Pearson's regression analysis was used to assess the relationship between the difference in the pre- and post-operative PCO on true lateral radiographs and the change in knee range of flexion (ROF) under non-weight-bearing conditions.

The decrease of the corrected PCO was (3.4 ± 3.3) mm compared with the preoperative value, the restoration of PCO was better in male than female [female (-5.4 ± 3.1) mm vs. male (-1.5 ± 2.0) mm, P < 0.05]. The difference in the corrected PCO after PS TKA demonstrated significantly correlated with the change in 2 years postoperative ROF in male and female, respectively (P < 0.05). While no statistically correlation was observed in the overall group (P > 0.05). Intraoperatively, the difference in the corrected PCO was significantly correlated with the change in ROF in male, female, and the overall group, respectively (P < 0.05).

Restoration of PCO plays an important role in the optimization of knee flexion after high-flex PS TKA. Femoral components based on Caucasian anatomic characteristics could not match the native anatomy of distal femurs of Chinese population especially female Chinese. Rotated resection of distal femur with anterior referencing technique usually leads to a decreased PCO and therefore reduces maximal obtainable flexion. Sexual dimorphism in humans and anatomic variations in various ethnic groups should be seriously considered in total knee prosthesis design.