Overstuffing of the lateral distal condyle is associated with worse intraoperative patellar tracking and postoperative lateral patellar tilt during robotic-assisted cruciate-retaining total knee arthroplasty.

Little is known about whether the coronal alignment of the lower limb and its alteration during total knee arthroplasty (TKA) affect the kinematics of the patellofemoral joint. Therefore, this study aimed to investigate the relationship between alterations in coronal alignment, femoral overstuffing, and patellar tracking using data recorded by a robotic system. Data from 241 robot-assisted cruciate-retaining TKAs were retrospectively analyzed. The native lateral distal femur angle and medial proximal tibia angle (nLDFA, nMPTA), final LDFA and MPTA (fLDFA and fMPTA), femoral external rotation relative to the transepicondylar axis, final-to-native differences of MPTA and LDFA (ΔMPTA, ΔLDFA), and the thickness of pure bone resections of medial and lateral sides of the distal condyles (MDC, LDC), posterior condyles (MPC, LPC), and tibia (MTIB, LTIB) were recorded using the MAKO system. Preoperative and postoperative patellar tilt angle (PTA) and lateral patellar angle (LPA) were measured on patellar axial radiographs, and their differences (ΔPTA and ΔLPA) were calculated. The parameters were compared between patients who underwent lateral retinaculum release (LRR group) and those who did not (NLRR group). Multivariate logistic regression analysis and multivariate linear regression analysis were performed to investigate the association of intraoperative measurements with intraoperative and postoperative patellar tracking. The LRR group had significantly decreased nLDFA, fLDFA and LDC levels, along with increased ΔLDFA and MDC values. A more valgus nLDFA, a larger ΔLDFA, and a decreased LDC thickness increased the odds ratio of requiring LRR. And a higher ΔLDFA was associated with increased postoperative lateral patellar tilt, indicated by positive ΔPTA and negative ΔLPA. Overstuffing of the lateral distal condyle, caused by a decreased nLDFA, an increased ΔLDFA, or a decreased LDC, was associated with higher odds for the need of intraoperative LRR and postoperative change of lateral patellar tilt during cruciate-retaining TKA.