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.