Magnetically controlled rod fracture is related to rod diameter but lower than TGR.

Abstract

Purpose: To quantify the risk of rod fracture after growth-friendly early-onset scoliosis (EOS) surgery, compare the risk of fracture between magnetically controlled growing rods (MCGR) and traditional growing rods (TGR), and compare the risk of fracture based on rod diameter.

Methods: EOS patients undergoing TGR or MCGR instrumentation were identified from a large, multi-national registry (Pediatric Spine Study Group). Subgroup analyses (chi-squared and Mann-Whitney U tests) were performed between rods with diameters ≤ 5 mm and > 5 mm and between MCGR and TGR. To account for difference in follow-up, a log-rank survival analysis was performed between subgroups over a 5-year period.

Results: A total of 1588 patients, representing 3176 rods, met the inclusion criteria. There was no difference in pre-operative Cobb angle or maximum kyphosis between MCGR and TGR groups. At index surgery, MCGR patients were slightly older, taller, and heavier, although BMI was similar. The overall 2-year risk of rod fracture was 3.05%. TGR 2-year fracture risk was higher than MCGR (4.96% vs. 1.82%, p < 0.001). Similarly, among MCGRs, rods with a diameter ≤ 5 mm fractured at a higher rate than those > 5 mm. The 5-year survival analysis corroborated our 2-year findings.

Conclusion: Although relatively rare, the risk of rod fracture in EOS patients may be higher than previously reported. The overall risk of rod fracture is higher with TGR compared to MCGR, and while smaller rod diameter led to increased risk of fracture in MCGR constructs, the rod diameter was not associated with fracture risk in TGR.

Level of evidence: IV.