Spine growth modulation with titanium implant: comparisons to observation and bracing in early adolescent idiopathic scoliosis.

Abstract

Outcomes of a pilot study of spine growth modulation (GM) were compared to those of untreated and braced patients from a concurrent bracing effectiveness trial (BrAIST). The purpose of this study was to determine probabilities of progression (PP) to fusion indications (≥45°) in a cohort of subjects who underwent GM surgery, and to compare GM outcomes to those of matched BrAIST subjects. Secondary analyses were conducted comparing two prospective longitudinal studies. In one, a vertebral GM system was implanted in 6 highly skeletally immature AIS patients. The control group provided by BrAIST was comprised of a subset of untreated or braced subjects that fit the eligibility criteria of the GM study. GM outcomes were compared to predictions from two prognostic logistic regression models derived from BrAIST to estimate risk of curve progression to ≥45°. If the GM patients were untreated, PPs ranged from 68-98%. If braced for 18 hours/day, progression was expected in two of six, one with a PP of 71%. This latter patient not only did not progress, his curve decreased >20°. In the matched cohort, two were untreated and quickly progressed, whereas two were braced and did not progress. Therefore, the bracing models and matched cohort confirmed the initial assumption that all GM patients were at high risk if untreated. They also supported the probable benefit of the GM system, as 3 of 6 benefited from GM relative to predictions for untreated patients, and one of 6 benefited compared to predictions for highly compliant braced patients.