Higher BMI and severity of preoperative Kellgren-Lawrence grade could be a risk factor for progression of patellofemoral osteoarthritis in the mid-term after opening wedge high tibial osteotomy for osteoarthritis and osteonecrosis.
Backgrounds: Medial opening wedge high tibial osteotomy (OWHTO) is a lower limb realignment surgery for symptomatic knee osteoarthritis (OA) or osteonecrosis of medial tibiofemoral compartment. This surgical procedure was an effective treatment that preserves the original joint, however it was reported that OWHTO promoted patellofemoral OA (PF-OA) recently. The purpose of this study was to investigate the mid-term clinical results of OWHTO and the influence of OWHTO on PF joint.
Materials And Methods
Subjects were 47 knees of 39 patients who had OWHTO in our institution from 2010 to 2015. Inclusion criteria was defined follow-up periods was more than 3 years. Age, body mass index (BMI), follow-up periods, range of motion (ROM) of the knee, and functional score (Japanese Orthopaedic Association (JOA) score) were obtained from medial record. Kellgren-Lawrence (KL) grade, femorotibial angle (FTA) and Insall-Sarvati ratio (ISR) were measured in radiographs, and we evaluated whether or not there was progression of arthritic change in medial, lateral and PF compartments at the time of the final follow-up compared with the preoperative radiographs. The difference between pre and post operation was analyzed by analysis of variance with Tukey test as a post-hoc analysis and logistic regression analysis was used for consideration of relevant factors to progression of PF-OA.
Forty knees of 33 patients (average age; 52 ± 8 years, BMI; 26.7 ± 3.9 kg/m2) were included in this study and average follow-up periods were 66±24 months. One case required conversion to total knee arthroplasty at 82 months after OWHTO. Knee extension ROM was -3.5 ± 6.1 degrees and flexion ROM was 139.3 ± 7.8 degrees at the final follow-up. JOA score significantly improved from 71.4 ± 13.1 points at the pre-op to 85.6 ± 13.6 points at the final follow-up (p < 0.001). In the radiographic evaluation, FTA significantly changed from 180.6 ± 2.5 degrees at the pre-op to 174.9 ± 2.6 degrees at the final follow-up (p < 0.001) and there was no significant difference in ISR. The progression of OA in medial, lateral and PF compartments were observed in 28 knees (70%), 21 knees (53%), and 28 knees (70%) respectively at the final follow-up. High BMI, severity of the pre-op KL-grade, and long duration after operation were related factors for progression of PF-OA.
Although OWHTO significantly improved knee functional score, the progression of PF-OA was shown in 70% cases and it was higher than progression of lateral compartment OA. The survival rate of OWHTO was 98% in this series, however, this study indicated that higher BMI and severity of pre-op KL-grade could be a risk factor for progression of PF-OA. In recent years, various osteotomy procedure for knee OA has been reported, however, it might be necessary to pay attention to the selection of surgical procedures in case with such risk factors from the point of view of progression of PF-OA.