P162 - Flexion contracture is the risk of patellofemoral osteoarthritis after open wedge high tibial osteotomy

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To evaluate the progression of patellofemoral OA with second-look arthroscopy and determine the pre- and post-operative patellar related factors for the progression of patellofemoral OA. Subsequently, progression of patellofemoral OA after OWHTO was elucidated in comparison with non-progression group focusing on the ROM.

Methods and Materials

58 knees (from 26 menand 32 women), which were performed OWHTO and second-look arthroscopy, were retrospectively enrolled in this study. The average time from initial to second-look was 20.1 ± 5.6 months.Pre- and post-operative knee alignment was compared by measuring the percentage of mechanical axis (%MA), the medial proximal tibial angle (MPTA), and posterior tibial slope. Patellar position was evaluated using the Caton-Deschamps index, tibial tuberosity-trochlear groove (TT-TG) distance, and patellar tilt. Clinical outcomes were evaluated with Lysholm and Kujala scores. These parameters were evaluated at pre- and post-operative, which were performed at final follow-up 42.7 ± 11.5 (range, 26 - 62) months.


The demographic data was compared between progression of patellofemoral OA (group P: n=23) and no progression (group N: n=35), and no significant difference between groups regarding age, gender, BMI and the K/L grade.Correction angle was 9.0 and 8.7 which was no significant difference between group P and N. Pre- and post-operative %MA, posterior tibial slope were not significant different, indicating that the preoperative malalignment and postoperative correction was no difference. Patellar tilt, patellar height and TT-TG distance were no significant difference between groups. Interestingly, pre- and post-operative extension in group P was significantly lower than that of group N, indicating that group P was included more flexion contracture (p<0.01). Postoperative clinical outcomes in group P were lower than in group N as well (p <0.05).


Flexion contracture of the knee was associated cartilage deterioration at patellofemoral joint, which might be affected clinical outcome after OWHTO.