Posterior Osteophyte Resection from the Medial Femoral Condyle Increases Medial Gap of Extension and Mid-Flexion in Total Knee Arthroplasty

Background: The present study aimed to determine the effect of posterior osteophyte resection from the medial femoral condyle on the medial gap increase in varus osteoarthritis during posterior-stabilized total knee arthroplasty (TKA). Methods: One hundred and eight cases of primary posterior-stabilized TKA for varus knee osteoarthritis were reviewed retrospectively. In a preoperative lateral view of the knee radiograph, 39 cases had the largest size osteophyte of the posterior femoral condyle > 5 mm (large osteophyte group) and 69 cases had 0 to 5 mm (small osteophyte group). After femoral component trial insertion, the posterior osteophyte of the medial femoral condyle was removed using a curved osteotome. Medial and lateral joint gaps at 0°, 45°, and 90° of flexion were measured intraoperatively before and after the posterior osteophyte resection from the medial femoral condyle. Results: The large osteophyte group showed a significantly larger increase in medial gap change at 0° and 45° of flexion than the small osteophyte group (medial gap increase at 0°: 0.2 ± 0.4 mm in the small osteophyte group and 2.9 ± 1.4 mm in the large osteophyte group, p < 0.001; medial gap increase at 45°: 0.3 ± 0.5 mm in the small osteophyte group and 1.7 ± 0.8 mm in the large osteophyte group, p < 0.001). At 0° and 45° of flexion, medial gap values after osteophyte resection were significantly larger than before osteophyte resection in both groups (p < 0.001). In linear regression analysis, posterior osteophyte size was also significantly associated with medial gap change at 0° and 45° of flexion (p < 0.001). Conclusions: Resection of large posterior osteophytes > 5 mm from the medial femoral condyle can be expected to result in a larger increase in the medial gap than resection of osteophytes ≤ 5 mm. Surgeons need to pay close attention to these intraoperative changes in the medial gap after posterior osteophyte resection to achieve appropriate mediolateral balance during TKA.