Change of Chondral Lesions and Predictive Factors After Medial Open-Wedge High Tibial Osteotomy With a Locked Plate System

Background: Although cartilage regeneration after medial open-wedge high tibial osteotomy (HTO) has been described, there is a paucity of reports regarding which factors influence cartilage regeneration. Purpose: To document whether cartilage regeneration occurs in the previously degenerated medial compartment of arthritic knees after medial open-wedge HTO without concomitant cartilage procedures and to assess which predictive factors influence regeneration after HTO. Study Design: Case series; Level of evidence, 4 Methods: From February 2008 to January 2014, 104 consecutive knees were enrolled retrospectively that received medial open-wedge HTO with a medial locked plate system without any additional cartilage regeneration procedures and were followed by second-look arthroscopy for plate removal 2 years after surgery. The mean SD age at the time of index HTO was 56.3 5.4 years. Cartilage status was graded at the time of initial HTO and second-look arthroscopy according to the International Cartilage Repair Society grading system, and regenerated articular cartilage was classified by the macroscopic staging system of Koshino et al at the time of second-look arthroscopy. Variables evaluated for possible association with regeneration of articular cartilage included age, sex, body mass index (BMI), American Knee Society score, mechanical tibiofemoral angle, medial proximal tibial angle, amount of correction angle, and degree of arthritis. Results: Per the International Cartilage Repair Society grading system, the lesions in the medial femoral condyle and the medial tibial plateau were improved in 54 knees (51.9%) and 36 knees (34.6%), respectively, at the time of second-look arthroscopy. According to the macroscopic grading system, partial and total regeneration of articular cartilage in the medial femoral condyle and the medial tibial plateau was observed in 75 knees (72%) and 57 knees (55%), respectively. Based on univariable logistic regression tests, regeneration of articular cartilage was associated with a smaller mean preoperative varus mechanical tibiofemoral angle (odds ratio [OR], 0.7; P = .023) and lower BMI (OR, 0.8; P = .026) for the medial femoral condyle and younger age (OR, 0.9; P = .048) and a larger mean correction angle (OR, 1.1; P = .023) for the medial tibial plateau. The mean preoperative knee and function scores were significantly improved at the last follow-up, but no correlation was found between the clinical outcomes and cartilage regeneration. Multiple logistic regression analysis for regeneration of articular cartilage showed lower BMI (OR, 0.7; P = .015) to be a significant predictor for the medial femoral condyle. Conclusion: Regeneration of degenerated articular cartilage in the medial compartment can be expected while correcting a varus deformity in arthritic knees after medial open-wedge HTO with a locked plate system without any additional cartilage regeneration procedures. Moreover, we suggest that medial open-wedge HTO in the medial arthritic knee with varus malalignment should be highly successful in terms of cartilage regeneration, especially for lower BMI patients.