Use of intra-operative internal distraction for the application of magnetically controlled growth rods (MCGR): a technique for maximizing correction in the rigid immature spine during index surgery

Objective: Operative treatment of early onset scoliosis (EOS) with Magnetically Controlled Growing Rod (MCGR) in moderate-to-severe curves poses a challenge due to the limited amount of force and length available with the implant. The purpose of this study was to assess the use of the intra-operative internal spine distraction using Harrington Outrigger, before definitive implantation of MCGR, with regard to initial correction, maintenance of correction, truncal balance, and complication rates.

Patients and methods: 16 EOS patients treated with the application of MCGR using the intra-operative internal distractor technique were included in the study. More than 50% of cases were congenital scoliosis with multiple vertebral anomalies. All patients were followed up for a minimum of 2 years. Radiological measurement of change in Cobb angle, thoracic kyphosis, lumbar lordosis, T1-S1 length, T1-T12l length, and sagittal balance were done at pre-op, immediate post-op, after 1 year, and 2 years. All the complications were noted and documented.

Results: The mean age of the operated patients was 8 ± 1.7 years, range (4-10 years). Mean pre-operative Cobb angle was 70.4 degrees. The mean correction of major Cobb angle was 34.6°. The percentage correction achieved in post-operative Cobb angle was about 51%. Mean change in post-operative thoracic kyphosis was 18.5° (40%). The average gain in immediate post-operative spinal length (T1-S1) and thoracic height (T1-T12) was 46.7 mm (18.3%) and 41 mm (23%), respectively.

Conclusion: Large and rigid curves in EOS can achieve a significant correction of Cobb angle and coronal imbalance during the index operation, by the use of intra-operative internal distraction at the time of MCGR insertion.

Level and type of study: Retrospective clinical study, level 4.