Paper 46: Factors associated with failure to recover the preoperative tegner activity scale after high tibial osteotomy for medial knee osteoarthritis

Objectives: With rising lifetime expectancy, the number of middle-aged patients who participated in sports activity has been increasing. When knee osteoarthritis (OA) develops, pain and joint effusion restrict sports participation and diminish patients' quality of life (QOL). High tibial osteotomy (HTO) for medial knee OA corrects lower leg alignment, thereby reducing pain and facilitating return to sports (RTS). While several studies have reported high rates of RTS after HTO, some patients failed to recover the pre-symptomatic level of sports activity, and the contributing factors remain unclear. The objective of this study is to identify factors associated with returning to the pre-symptomatic sports level after HTO for medial knee OA.
Methods: This retrospective study design using patient data was approved by the institutional review board of the hospital and after obtaining patients' informed consent. A total of 367 patients who underwent unilateral HTO for a medial OA with a varus knee from 2017 to 2022 were enrolled in this study. HTO was performed using the medial opening-wedge HTO (OW-HTO) or inverted V-shaped HTO (IV-HTO) according to the degree of valgus correction angle or the OA grade of patellofemoral (PF) joint (Figure 1). Of those, 107 patients (57 men and 50 women, 58.4+-10.3 years) participated in sport activity before surgery. These patients were classified by the change of Tegner activity scale (TAS) before and after HTO surgery. 73 patients who recovered the pre-symptomatic TAS after HTO were assigned to Group S, and 34 patients who didn't return to that level were Group I. To identify the factors associated with failure to return to the pre-symptomatic sport level, we compared patient background and preoperative and postoperative clinical outcomes and radiographic parameters between Groups S and I using the paired Student t test and the χ2 test. Variables that were significant in univariate analyses were subsequently entered into a multivariable logistic regression model. Surgical technique and indication related factors included a priori as an adjustment covariate in the multivariable model, irrespective of its univariate significance, because the cohort included two HTO surgical procedures with different indications. Statistical significance was set at p<0.05.
Results: Both groups improved Lysholm score (Group S: 64.0 to 94.2 points, Group I: 60.6 to 84.5 points) and functional knee score (Japan Orthopaedic Association Score, Group S: 70.8 to 92.8 points, Group I: 67.6 to 86.3 points) after HTO surgery (p<0.01). Both groups demonstrated significant changes in the Hip-Knee-Ankle (HKA) angle after HTO (Group S: -6.4 to 3.9°, Group I: -6.1 to 4.8°, p<0.01, respectively). Regarding RTS, while there was no significant difference between pre-symptomatic and postoperative TAS in Group S (4.6 to 4.6), Group I had a lower postoperative TAS than the pre-symptomatic score (5.5 to 4.0 points, p<0.01). The time to RTS was significantly longer in Group I than in Group S (Group S: 7.8 months, Group I: 11.0 months, p<0.01). Patient background and radiographic parameters were compared between two groups to screen factors associated with failure to return to the pre-symptomatic sports level after HTO. Concerning the patient background, the patients in Group I were younger than those in Group S (Group S: 60.3 years, Group I: 54.4 years, p<0.01). The pre-symptomatic TAS in Group I was higher than that in Group S (Group S: 4.6 points, Group I: 5.5 points, p<0.01). There were no significant differences in surgical procedure distribution and preoperative PF-OA grade between the two groups (Table 1). Regarding the radiographic parameters, postoperative medial proximal tibial angle (MPTA) was significantly greater in Group I than in Group S (p<0.01). There were no significant differences in preoperative and postoperative HKA angles, posterior tibial slope, patellar height or leg length (Table 2). Multivariate analysis identified younger age (odds ratio (OR) 0.95 per year, 95% CI 0.91-1.00, p=0.04), greater pre-symptomatic TAS (OR 2.04 per point, 95% CI 1.31-3.35 , p<0.01) and greater postoperative MPTA (OR 1.88 per 1°, 95% CI 1.31-2.88, p<0.01) as independent factors for failure to recover the pre-symptomatic TAS (Table 3). Prespecified interactions between surgical procedure and key predictors (surgical procedure ×age, ×postoperative MPTA, ×preoperative TAS) were not significant (all p>0.05).
Conclusions: Our study demonstrated that 'younger age', 'higher pre-symptomatic TAS' and 'greater postoperative MPTA' were associated with failure to recover the pre-symptomatic sport level after HTO for medial knee OA. These findings might indicate that joint-line obliquity after HTO should be carefully considered in younger patients with medial knee OA who wish to return to high-impact sports.