Magnetically controlled growing rods increase 3D true spine length in idiopathic early onset scoliosis patients: results from a multicenter study.

Purpose: To determine, at 2 year follow-up, 3D spine growth for idiopathic early onset scoliosis (iEOS) patients treated with magnetically controlled growing rods (MCGR).

Methods: From an international EOS registry, patients with iEOS treated with MCGR were identified. Scoliosis, kyphosis, traditional coronal height, and 3D true spine length (3D-TSL) were measured pre-index surgery, post-index, and at 2 year follow-up.

Results: 135 participants, mean age 8.1 years (2.7-15.6) were included. Scoliosis improved from 71° pre-index to 41° post-index (p < 0.001) and remained constant at 2 years (43°, p = 0.58). Kyphosis improved from 49° to 36° (p < 0.001); then increased by 2 years to 42° (p = 0.002). Traditional T1-S1 height, which reflects both spine growth and changes in deformity, increased from pre-index to post-index (274 mm vs. 310 mm; p < 0.001), and again at 2 years (332 mm, p < 0.001). As 3D-TSL reflects growth of the spine, independent of changes in deformity, as expected it did not change perioperatively (335 mm vs. 339 mm, p = 0.83), but significantly changed by 2 years (367 mm; p < 0.001). Participants < 5 years at surgery increased 22 mm (8.2%), 5-10 years increased 26 mm (7.8%), and > 10 increased 41 mm (11.0%). For instrumented levels, mean vertebral growth was 1.3 mm/level for < 5 years, 1.4 mm/level for 5-10 years, and 2.2 mm/level for > 10 years.

Conclusions: As kyphosis increased over time, these out of the coronal plane changes justify the use of 3D-TSL for this cohort of patients. For idiopathic EOS patients treated with MCGR, 3D spine length increased by 28 mm during the 2 year post-operative period.