In Situ Microwave Ablation With Intralesional Resection and Subsequent Mechanical Reinforcement for Juxtaarticular Osteosarcoma Achieves Satisfactory Functional Outcomes: A Three-Year Kinematic Analysis

Background: Joint-preserving surgery of a patient's native knee joint for juxtaarticular osteosarcoma may enhance function but poses resection and reconstruction challenges. Methods: We included 15 patients with nonmetastatic distal femoral osteosarcoma who underwent in situ microwave ablation with intralesional resection and subsequent mechanical reinforcement. Knee function was assessed at 1 and 3 years postoperatively using Musculoskeletal Tumor Society scores, six degrees of freedom kinematic analysis. The 1-year and 3-year construct and overall survival rates were recorded. A control group of 20 healthy individuals was used for comparison. Result: At the 3-year follow-up, two patients had died. The final Musculoskeletal Tumor Society score was 29.0 ± 1.2 (range, 26 to 30). No major complication was recorded. At 1 year, notable gait differences were observed compared with healthy control subjects, including reduced knee flexion at 12%, 52%, 62%, 75%, and 85% of the gait cycle; increased adduction at 12%, 52%, 62%, and 75%; and increased external rotation at 52%, 62%, 75%, and 85%. The range of motion (ROM) in flexion/extension, internal/external rotation, proximal/distal translation, and medial/lateral translation ( P < 0.05) were significantly reduced. At 3 years, most kinematic differences had diminished and ROM differences had largely resolved, with only an increase in internal/external and abduction-adduction ROM. Conclusion: The surgical procedure of in situ microwave ablation with intralesional resection and subsequent mechanical reinforcement shows restricted mobility at 1 year postoperatively, but knee kinematic performance is nearly indistinguishable from that of healthy individuals at the 3-year follow-up. With adequate resection and adjuvant treatment insured, mechanical reinforcement reconstruction effectively preserves knee function.