Long-term Outcomes after Medial Open Wedge High Tibial Osteotomy - A Retrospective Study of 69 Patients.

High tibial osteotomy (HTO) is a widespread option to avoid or delay total knee arthroplasty (TKA). The present study aimed to assess the long-term survival rate and postoperative subjective knee function after isolated medial open wedge HTO in patients with symptomatic medial compartment knee osteoarthritis (OA) and varus malalignment.Sixty-nine patients (48.8 ± 6.7, 35-66 years; preoperative mechanical tibiofemoral angle [mTFA] -5.3 ± 3.4; -14.9-0.0° varus) treated with medial open wedge HTO using a TomoFix plate were included in this retrospective study, with a follow-up of at least 10 years (11.8 ± 1.0 years). The survival rate after HTO was calculated after 5 and 10 years. Subjective knee function was assessed using Hospital for Special Surgery (HSS), Oxford knee, Lequesne, and Lysholm scores.Thirty-three patients underwent conversion to TKA, on average, 7.0 ± 3.4 (1.3-13.7) years after HTO. Five- and ten-year survival rates were 84.1 and 60.9%, respectively. Patients without conversion to TKA showed a Lysholm score of 64.5 (35-92), Lequesne score of 7 (1-13), HSS score of 71 (56-86), and Oxford knee score of 38.5 (25-44) at the last follow-up (more than 10 years). Significantly higher scores were registered at the last follow-up compared to the preoperative state regarding the Lysholm score (preoperative: 43.5 [12-95]; follow-up: 64.5 [35-92]; p < 0.001). The HSS score (preoperative: 69.5 [43-93]; follow-up: 71 [56-86]; p = 0.6941) showed no statistically significant change during the 10-year follow-up period. The Lequesne score was significantly lower than the preoperative score (preoperative: 11.5 [0.5-22]; follow-up: 7 [1-13]; p < 0.001), indicating a lower handicap.The majority of patients with a valgus medial compartmental knee OA treated with HTO with fixation using the TomoFix plate can expect no conversion to TKA for more than 10 years. Furthermore, patients without conversion to TKA after 10 years still had a significantly higher subjective knee function than preoperatively. Further research is needed to identify risk factors for conversion to TKA. This helps to guide surgeons in selecting patients who will benefit most from HTO.