Abstract
With observed success and increased popularity of growth modulation techniques, there has been a trend towards use in progressively younger patients. Younger age at growth modulation increases the likelihood of complete deformity correction and need for implant removal prior to skeletal maturity introducing the risk of rebound deformity. The purpose of this study was to quantify magnitude and identify risk factors for rebound deformity after growth modulation.
We performed a retrospective review of all patients undergoing growth modulation with a tension band plate for coronal plane deformity about the knee with subsequent implant removal. Exclusion criteria included completion epiphysiodesis or osteotomy at implant removal, ongoing growth modulation, and less than one year radiographic follow-up without rebound deformity. Mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), hip-knee-ankle angle (HKA), and mechanical axis station were measured prior to growth modulation, prior to implant removal, and at final follow-up.
Sixty-seven limbs in 45 patients met the inclusion criteria. Mean age at growth modulation was 9.8 years (range 3.4–15.4 years) and mean age at implant removal was 11.4 years (range 5.3–16.4 years). Mean change in HKA after implant removal was 6.9O (range 0O–23 O). Fifty-two percent of patients had greater than 5O rebound and 30% had greater than 10O rebound in HKA after implant removal. Females less than ten years and males less than 12 years at time of growth modulation had greater mean change in HKA after implant removal compared to older patients (8.4O vs 4.7O, p=0.012). Patients with initial deformity greater than 20O degrees had an increased frequency of rebound greater than 10O compared to patients with less severe initial deformity (78% vs 22%, p=0.002).
Rebound deformity after growth modulation is common. Growth modulation at a young age and large initial deformity increases risk of rebound. However, rebound does not occur in all at risk patients, therefore, we caution against routine overcorrection. Patients and their families should be informed about the risk of rebound deformity after growth modulation and the potential for multiple surgical interventions prior to skeletal maturity.
