Abstract
Introduction
Overstuffing the patellofemoral joint during total knee arthroplasty (TKA) is considered a potential cause of limited knee flexion and patellar maltracking. We investigated the effect of patellar thickness on intraoperative knee flexion and patellar tracking in navigated TKA.
Methods
Twenty osteoarthritic knees (20 patients) were investigated in this study. Knees with valgus deformity were excluded. The same posterior stabilized prosthesis was employed in all the 20 cases. Preoperative patellar thickness was measured using a caliper, and patellar resection was performed to restore the native thickness by placing a standard 10-mm-thick trial patella. After placement of all trial components, maximal flexion against gravity was measured using a navigation system. The trial patella was also assessed for tracking, with and without suturing of the medial capsule (the “three-stitch” test and no-thumb test, respectively). Subsequently, 2-mm and 4-mm augmentations were applied to the standard trial patella, and the aforementioned measurements and assessments were repeated.
Results
The average preoperative patellar thickness was 22.7 mm. Knee flexion with the standard trial patella was 125.3° ± 8.1°. Increasing the patellar thickness by 2 mm significantly (p < 0.0001) reduced the knee flexion by an average of 4.2°. Similarly, a 4-mm augmentation significantly (p < 0.0001) decreased the knee flexion by an average of 8.9°. Increased patellar thickness had no visible effect on patellar tracking in any of the knees.
Conclusion
Patellofemoral overstuffing should be avoided to achieve optimal knee flexion in TKA. However, our findings indicate that patellar tracking is not influenced by patellar thickness.
