Rebound After Guided Growth for Idiopathic Genu Valgum: Long-Term Radiographic Follow-Up to Skeletal Maturity and Associated Factors

Background/Objectives: Temporary hemiepiphysiodesis corrects idiopathic genu valgum during growth, but alignment may drift after implant removal. Radiographic alignment to skeletal maturity was evaluated, and factors associated with post-removal rebound were explored. Methods: This single-center longitudinal observational cohort study included 17 patients (31 limbs) treated with tension-band plates. Standing long-leg radiographs were assessed before implantation (t0), at plate removal (t1), and at final follow-up after skeletal maturity (t2). Rebound was defined as a lateral mechanical-axis deviation (MAD) shift of at least 5 mm from t1 to t2. Paired comparisons and exploratory linear regression models were used to assess longitudinal changes and potential predictors of rebound. Results: Mean age was 13.53 ± 1.27 years at t0, 14.67 ± 1.45 years at t1, and 19.64 ± 1.08 years at t2. MAD changed from −15.06 ± 7.32 mm at t0 to 3.65 ± 7.29 mm at t1 and −1.03 ± 7.48 mm at t2. The mean lateral shift after plate removal was 4.68 ± 6.55 mm (p < 0.001). A total of 15 of 31 limbs (48.4%) met the rebound definition. At t2, 29 limbs (93.5%) remained within Stevens zones ±1. Greater residual growth (univariate b = 0.621, p = 0.003) and isolated distal femoral plating (univariate b = 5.534 mm, p = 0.017) were associated with greater lateral drift and remained significant in the multivariable model. Conclusions: Post-removal rebound was frequent but generally modest, with the observed alignment drift predominantly reflecting distal femoral change. Nevertheless, most limbs remained within the central, clinically acceptable Stevens zones at skeletal maturity. These findings support continued radiographic surveillance, particularly following isolated distal femoral correction and in patients with substantial residual growth.