How does magnetically controlled growing rods insertion affect sagittal alignment in ambulatory early onset scoliosis patients?

Purpose The importance of sagittal alignment restoration in early onset scoliosis (EOS) management has rarely been investigated to date. The aim was to report the influence of magnetically controlled growing rods (MCGR) insertion on the sagittal alignment of EOS patients. Methods All consecutive ambulatory patients operated with MCGR rods between 2011 and 2018 were retrospectively included in four institutions. Standing biplanar radiographs were performed preoperatively, in the early postoperative period and at latest follow-up. Global and local sagittal parameters, spinal global shape and harmony were investigated. Results A total of 37 ambulatory EOS patients were included (mean age at surgery 8.5 (± 2) years). 70% had a balanced construct postoperatively. Both MaxTK (− 17°, p = 0.02) and MaxLL (− 15°, p = 0.001) were significantly reduced, particularly at the instrumented levels. The number of vertebrae included in the lumbar lordosis significantly increased (+ 2 levels, p = 0.02), as well as the thoraco-lumbar inflexion point (+ 2 levels, p < 0.001) and the kyphosis apex (+ 1 level, p < 0.001). Overall mechanical failure rate was 40.5%, and radiological PJK was observed in 43% of the patients, with 11 remaining asymptomatic. Patients with initial hyperkyphosis (> 50°) developed more complications (62% vs. 28%, p = 0.04). Conclusion MCGR insertion flattened the spine in EOS, at both instrumented and non-instrumented levels. Overall spinal harmony was modified, with a cranial shift of the thoraco-lumbar inflexion point and the thoracic kyphosis apex, associated with a lengthening of the lumbar lordosis. The rate of complication remained high, some explanations being found in the radiological changes reported such as the preoperative location of the TK apex. Level of evidence IV.