Description
【Introduction】It is known that open wedge high tibial osteotomy (OWHTO) reduces load distribution of the medial compartment by moving the load axis outward, and cartilage status improvement in the medial compartment can be expected in some cases. However, its factors had not been thoroughly investigated. The purposes of this study were to evaluate factors affecting cartilage status improvement in the medial compartment after OWHTO by comparing cartilage status arthroscopically at the time of OWHTO and second-look, and to investigate factors affecting cartilage status improvement. The hypothesis of this study was that several preoperative and postoperative factors would affect cartilage status improvement in the medial compartment.
【Materials and methods】In the current study, 132 patients (51 males and 81 females) who underwent OWHTO between 2017 and 2021 with minimum 2-year follow-up were included. Medial meniscus was treated according to its status, repaired if possible, partially resected if degenerated or impossible to repair, and centralization was performed for extruded meniscus. Cartilage in both medial femoral condyle (MFC) and medial tibial plateau (MTP) were divided into 9 subregions (anterior-middle-posterior and internal-central-external) and evaluated arthroscopically according to ICRS classification during initial surgery and second-look at the time of plate removal. To investigate factors affecting cartilage status improvement, multiple regression analyses were conducted for subregions where cartilage status improvement was observed, with the amount of change in ICRS classification as the dependent variable, and age, gender, BMI, collection angle, medial meniscus procedures, pre- and post-operative radiographic parameters (%MA, MPTA, LDFA, JLCA), and preoperative ICRS grade as the independent variables.
【Results】At the time of initial surgery, ICRS classification of grade 3 or higher was more common at the central to internal subregions in the MFC and at the central subregions in the MTP. At the second-look surgery, following subregions of the MFC did not show significant cartilage status improvement; posterior-internal, posterior-external and anterior-external, while other subregions of the MFC and all subregions of MTP showed significant improvement. Worse preoperative ICRS grade was detected as a factor in all MFC and MTP subregions where cartilage improvement was observed. Furthermore, smaller preoperative MPTA was also detected in middle-central regions of MFC.
【Discussion】The preoperative cartilage status affected cartilage repair in the medial compartment and the preoperative varus deformity of tibia affected cartilage repair at loading area of femur. The current study suggested that OWHTO affected the positive effect for cartilage status at loading area by reducing load distribution of the medial compartment.
