Background: Previous studies have reported patellofemoral cartilage degeneration and analyzed the factors affecting degeneration after open-wedge high tibial osteotomy (OWHTO). However, no studies have evaluated patellofemoral cartilage degeneration or examined the factors affecting degeneration after closed-wedge high tibial osteotomy (CWHTO). Purpose: To investigate and compare patellofemoral cartilage degeneration after CWHTO and OWHTO via arthroscopic evaluation and to analyze the factors affecting the degeneration. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 54 CWHTOs and 50 OWHTOs were performed with first-look arthroscopy between 2013 and 2017 at one institution. Hardware removal and second-look arthroscopy were performed, on average, 30.2 months after CWHTO and 26.8 months after OWHTO ( P = .178). Patient characteristics did not differ significantly between the groups. Radiographically, the mechanical axis, posterior tibial slope, and modified Blackburne-Peel ratio were evaluated. Arthroscopically, the percentage of patient with patellofemoral cartilage degeneration was evaluated according to the International Cartilage Repair Society grading system. Logistic regression analysis was used to identify the factors affecting patellofemoral cartilage degeneration in terms of demographics and the change of mechanical axis (correction angle), tibial posterior slope angle, and modified Blackburne-Peel ratio. The Anterior Knee Pain Scale was used for clinical comparison between the patellofemoral degenerative and nondegenerative groups. Results: No significant differences were observed in pre- and postoperative radiographic results between the CWHTO and OWHTO groups, except that the postoperative modified Blackburne-Peel ratio was significantly smaller among the OWHTOs. The percentage of patients with patellofemoral cartilage degeneration were 29.6% in the CWHTO group and 44% in the OWHTO group ( P = .156) at second-look arthroscopy. The correction angle was the only significant factor affecting cartilage degeneration in the CWHTO group (odds ratio, 2.324; P = .013; cutoff value, 9.6°) and the OWHTO group (odds ratio, 1.440; P = .041; cutoff value, 10.1°). The postoperative Anterior Knee Pain Scale score was significantly lower in the patellofemoral degenerative group as compared with the nondegenerative group among the OWHTO group (81.6 vs 76.4; P = .039); among the CWHTO group, there was a lower tendency in the degenerative group, but this was without significance (81.1 vs 79.6; P = .367). Conclusion: Patellofemoral cartilage degeneration progressed after CWHTO and OWHTO with large alignment correction. High tibial osteotomy should be selected with careful consideration of the osteoarthritic status of the patellofemoral joint and required correction angle, regardless of applying a closed- or open-wedge technique.
The factors affecting the timing of bone union after closing-wedge high tibial osteotomy
