Degree of Preoperative Subchondral Bone Marrow Lesion Is Associated With Postoperative Outcome After Medial Opening Wedge High Tibial Osteotomy

Background: In osteoarthritis of the knee, subchondral bone marrow lesion (BML) is known to be significantly associated with the severity of pain. However, little is known about the influence of preoperative BML on postoperative outcomes after medial opening wedge high tibial osteotomy (MOWHTO). Purpose: To compare patient-reported outcomes for those who underwent MOWHTO according to the severity of BML based on magnetic resonance imaging. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 136 patients who underwent MOWHTO between June 2011 and May 2016 with clinical and radiologic assessments before and after surgery were retrospectively enrolled. Patients were divided into 2 groups according to the presence or absence of BMLs. They were then subdivided into 4 or 3 groups based on the sum of BML scores of the medial femoral condyle and tibial plateau according to MRI (magnetic resonance imaging) Osteoarthritis Knee Score or Filardo classification, respectively. Associations between the severity of BML and postoperative 1- and 2-year Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) subscores were evaluated through linear regression analysis. At postoperative 2 years, the rate of patients having a WOMAC score improvement of 15 points based on minimum clinically important difference and patient satisfaction were compared between groups. Results: BMLs were present in 96 (70.6%) of 136 cases. There were no significant differences in demographics or radiographic variables between groups according to the presence/absence or severity of BMLs (all P >.05). There was a significant association between preoperative or 1-year postoperative WOMAC pain/function score and the extent or intensity of BMLs (all P <.05). After adjusting for age, body mass index, osteoarthritis grade, and hip-knee-ankle angle, the significance persisted in the association between the extent or intensity of BMLs and WOMAC pain/function score at 1 year after surgery (all P <.05). However, a significant association was not found at postoperative 2 years (all P >.05). All groups showed similar rates of WOMAC score showing 15 points of improvement and satisfaction after MOWHTO (all P >.05). At 2 years after surgery, 82.5% of patients with BMLs were satisfied with their operation, as compared with 84.4% of those without BMLs (P =.801). Conclusion: Although worse clinical outcomes were associated with severe BML during the recovery period, MOWHTO provided a high degree of clinical improvement on patient-reported outcomes regardless of the severity of BML at 2 years postoperatively.