Growth modulation increases clinical success in vertebral body tethering.

purposeThe relationship between skeletal maturity and postoperative growth modulation (GM) in patients treated with Vertebral Body Tethering (VBT) is poorly understood. We aimed to: (1) identify preoperative skeletal maturity factors associated with GM, and (2) assess the relationship between GM and postoperative success in patients treated with VBT.

methodsWe retrospectively reviewed radiographic data from 55 patients with a minimum follow-up of 2 years (2.6 ± 0.5). Changes in standing height and skeletal maturity (Sanders Stage [SS], Triradiate Cartilage [TRC], and Risser Stage [RS]) were assessed at all timepoints. Patients that exhibited GM were defined by ≥ 6° of deformity correction from first erect to any postoperative timepoint. Successful outcomes were defined by a Cobb Angle of ≤ 30° at latest follow-up.

resultsWe observed GM in 42% (23 of 55) of patients. GM was influenced by SS (p = 0.017) and TRC (p = 0.013), but not RS (p = 0.104). We observed a successful outcome in 91% of patients that exhibited GM compared to 44% of those that did not (p < 0.001; OR 12.9). No difference was identified in preoperative deformity magnitude or amount of initial correction achieved between patients that did and did not exhibit GM. Patients who exhibited GM had a higher revision rate (30.4%) than when compared to those who did not (3.0%, p = 0.005, OR 9.7).

conclusionPostoperative success after VBT is directly related to GM. Patients who modulate their deformity are 12.9 times more likely to exhibit a successful outcome and can be identified preoperatively based on SS or TRC.