An increased medial proximal tibial angle of greater than 95 degrees after opening wedge high tibial osteotomy is not associated with deterioration of minimum 10-year clinical outcomes

Purpose The purpose of this study was to assess whether an excessively increased medial proximal tibial angle (MPTA) resulted in the deterioration of long-term clinical outcomes after opening wedge high tibial osteotomy (OWHTO) for patients with knee osteoarthritis (OA). Methods A total of 69 OA knees that underwent OWHTO, with follow-up for a minimum of 10 years, were retrospectively reviewed. The knee and function scores of the Knee Society Score were assessed separately, and cases with a score decline greater than or equal to the minimal clinically important difference from postoperative 1 to 10 years were defined as showing clinical deterioration. Cartilage status was assessed with arthroscopy at the time of osteotomy (first-look) and plate removal (second-look) according to the International Cartilage Repair Society grading system. The outcomes were compared between knees with MPTA ≤ 95° ( n = 27) and MPTA > 95° ( n = 42). Results The mean knee and function scores at postoperative 10 years in MPTA ≤ 95° knees (86.8 ± 9.6 and 90.4 ± 13.1) were not significantly different from those in MPTA > 95° knees (85.8 ± 11.5 and 86.9 ± 14.2). The rate of clinical deterioration in knee and function scores was not significantly different between MPTA ≤ 95° knees (26% and 26%) and MPTA > 95° knees (21% and 36%). No significant differences were found between the MPTA ≤ 95° and MPTA > 95° groups in the cartilage status of all compartments at both first-look and second-look (postoperative 21 months) arthroscopies. Conclusions Increased MPTA > 95° after OWHTO is not associated with deterioration of minimum 10-year clinical outcomes.