Decrease of tibial tuberosity trochlear groove distance following mechanically aligned total knee arthroplasty

Anterior knee pain (AKP) is common following total knee arthroplasty. The tibial tuberosity trochlear groove distance (TTTG) influences patellofemoral joint loading in the native knee. Increased TTTG may lead to maltracking of the patella and anterior knee pain. The purpose of this study was to investigate potential changes in TTTG following total knee arthroplasty (TKA).

TTTG was measured on preoperative CT data on a consecutive series of patients scheduled to receive TKA with patient-specific instrumentation, and compared to a computer simulation of the postoperative TTTG. Preoperative TTTG was measured with a 3D planning software in 250 knees. The postoperative result was simulated and TTTG measured within the software. Three different groups were analysed: neutral (180° ± 3) (n = 50), valgus (> 190°) (n = 100), and varus (< 170°) (n = 100).

Median preoperative to simulated postoperative TTTG decreased from 15.0 [interquartile range (IQR) 6.0] mm to 6.5 (IQR 5.0) mm for all axes combined. A significant postoperative reduction of TTTG was found in each group (p < 0.001). The mean change in TTTG did not differ significantly between the groups [- 8.8 (IQR 5.5) mm neutral, - 8.3 (IQR 7.0) mm valgus, - 7.5 (IQR 5.8) mm varus, p = 0.223].

This computer-based study suggests that mechanically aligned TKA significantly decreases TTTG distance in neutral, valgus and varus knees, assuming that the postoperative result coincides with the preoperative planning. Further study is warranted to evaluate the clinical relevance of this finding.