Breaking the "law of diminishing returns" with novel, staged, unilateral magnetically controlled growing rods to guided growth surgery for severe, progressive infantile scoliosis.

Purpose: Infantile scoliosis presents a significant challenge due to high risk of pulmonary complications and morbidity. While dual growing rod constructs are often utilized, they are not always feasible in a young patient with a severe curve. In this study, we present a series of eight patients treated with a unilateral magnetically controlled growing rod (uMCGR) construct later converted to guided growth surgery (GGS).

Methods: A multicenter database was queried for patients with progressive infantile scoliosis treated with uMCGR before later conversion to GGS. A minimum of 2 year follow-up was required for inclusion. Curve magnitude, trunk growth, revisions, and complications were tracked at all time points.

Results: Eight patients were included in the study. Mean age at index surgery was 4.1 years, while conversion to GGS occurred at average 7.9 years and final follow-up was at 10.5 years of age. At index procedure, major curve averaged 77.1°, which improved to 45.4°. Major curve increased to 48.4° prior to conversion, then improved to 30.9°. Major curve averaged 36.8° at final follow-up, for a maintained curve correction of 52.3%. T1-12 height and T1-S1 height averaged 15.4 and 21.5 cm at index procedure and increased to 20.6 and 32.7 cm at final follow-up. Nine revisions were performed in 6 patients, and no patient showed evidence of premature fusion.

Conclusions: Treatment of severe progression infantile scoliosis with this staged protocol provided excellent curve correction with continued trunk growth through treatment, without evidence of the "Law of Diminishing Returns".