Serial Changes in the Joint Space Width and Joint Line Convergence Angle After Closed-Wedge High Tibial Osteotomy

Background: There have been little data concerning serial changes in the joint space width (JSW) and joint line convergence angle over the course of follow-up periods after closed-wedge high tibial osteotomy (CWHTO). Purpose: To evaluate serial changes in the JSW and joint line convergence angle after CWHTO. Study Design: Case series; Level of evidence, 4. Methods: A total of 100 computer-assisted CWHTOs with a minimum follow-up period of 3 years (mean, 4.4 years) were analyzed. Clinically, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score was evaluated. Radiographically, the mechanical axis was measured preoperatively and postoperatively. The minimal JSW was measured as the shortest distance between the femur and the tibia. The convergence angle was measured as the angle between the tangent to the subchondral plates of the femoral condyle and the tibial plateau. Serial changes in these measurements were analyzed preoperatively; at 3 months, 6 months, 1 year, and 2 years postoperatively; and at the final follow-up. The intraclass correlation coefficients for all measurements were greater than 0.8. Results: The mean WOMAC score improved from 41.4 preoperatively to 14.9 at the final follow-up. The preoperative and postoperative mean mechanical axis was 8.1 degrees varus and 1.6 degrees valgus, respectively. The mean minimal JSW was 2.5, 2.9, 2.9, 3.1, 3.2, and 3.1 mm preoperatively and at 3 months, 6 months, 1 year, 2 years, and the final follow-up, respectively (P < . 001). The mean convergence angle was 4.4 degrees, 3.9 degrees, 4.0 degrees, 4.1 degrees, 4.2 degrees, and 4.3 degrees, respectively, during the same time periods (P = .068). Conclusion: Cartilage healing, as indicated by the JSW, and clinical improvement were maintained over the minimum 3-year follow-up after CWHTO. Cartilage pressure, as indicated by the convergence angle, remained unchanged after CWHTO.