Longitudinal Radiographic Outcomes and Revision Burden After Magnetically Controlled Growing Rod Treatment for Early-Onset Scoliosis

Abstract

Background: To evaluate longitudinal radiographic outcomes, exploratory radiographic response, and planned versus unplanned revision burden after magnetically controlled growing rod treatment in patients with early-onset scoliosis. Methods: We retrospectively reviewed 55 patients with early-onset scoliosis treated with magnetically controlled growing rods at a single center. Complete year-3 radiographic measurements were available for 40 patients; therefore, year-3 estimates were conditional on imaging availability. Cobb angle, T1–S1 length, and apical vertebral translation (AVT) were assessed preoperatively and at postoperative years 1, 2, and 3. Longitudinal changes were evaluated using generalized estimating equations. Exploratory radiographic responder endpoints included ≥20° Cobb correction, ≥30% Cobb correction, and a ≥30 mm preoperative-to-year-3 T1–S1 length difference. Freedom from unplanned revision and composite endpoints were also evaluated. The radiographic thresholds were pragmatic and were not validated measures of clinically important improvement. Results: The cohort included 33 female and 22 male patients, with a mean age at surgery of 8.10 ± 1.86 years. Neuromuscular and congenital scoliosis accounted for 41.8% and 40.0% of cases, respectively, and dual-rod constructs were used in 83.6%. At year 3, mean Cobb angle was 40.15° ± 19.03°, mean radiographic T1–S1 length was 383.02 ± 54.42 mm, and mean AVT was 32.80 ± 23.56 mm among 40 patients with complete measurements. GEE models showed significant reductions in Cobb angle and AVT and increases in T1–S1 length at each postoperative year (all p < 0.001). At year 3, ≥20° Cobb correction, ≥30% Cobb correction, and ≥30 mm preoperative-to-year-3 T1–S1 length difference were achieved in 50.0%, 55.0%, and 67.5% of patients, respectively; 35.0% achieved both radiographic thresholds and 25.0% achieved both thresholds with no recorded unplanned revision. Patient-level fields recorded any complication in 20.0%, unplanned revision in 16.4%, internal revision classification in 43.6%, and definitive fusion in 16.4%; these fields were not treated as mutually exclusive. Conclusions: MCGR treatment was associated with longitudinal radiographic improvement among patients with available measurements. The preoperative-to-year-3 T1–S1 difference includes the effect of index surgery and should not be interpreted as biological spinal growth alone. These findings suggest that MCGR success should be assessed not only by curve correction, but also by measured spinal-length gain and revision burden.