Matched Comparison of Magnetically Controlled Growing Rods with Traditional Growing Rods in Severe Early-Onset Scoliosis of ≥90°

Abstract

Background: Severe early-onset scoliosis (EOS) is managed surgically but represents a challenge due to limited implant fixation points, large curve size, and fragile patients with comorbidities. Magnetically controlled growing rods (MCGRs) have the advantage of avoiding surgical intervention for routine lengthening, but their ability to address severe EOS has not been studied, to our knowledge.Methods: A retrospective review of a prospectively collected international database identified 44 children with severe ( ‡90°) EOS treated with MCGRs who met our study criteria. Etiology, age, and sex-matched patients treated with traditional growing rods (TGRs) were identified from the same database. Patients were evaluated at a 2-year follow-up. No patients with vertically expandable prosthetic titanium ribs (VEPTRs) were included. The health-related quality of life was evaluated with the 24-Item Early Onset Scoliosis Questionnaire (EOSQ-24).Results: The mean preoperative major coronal curve was 104°in the MCGR group and 104°in the TGR group. At the 2-year follow-up, the mean major coronal curves were 52°and 66°(p = 0.001), respectively. The mean T1-T12 heights were 155 mm and 152 mm preoperatively and 202 mm and 192 mm at the 2-year follow-up (p = 0.088). According to Kaplan-Meier analysis, the 2-year unplanned-revision-free survival was 91% in the MCGR group and 71% in the TGR group (p < 0.005). The 2-year score in the EOSQ-24 pulmonary function domain was better in the MCGR group. There were no other significant differences in the EOSQ-24 scores between the groups.Conclusions: MCGRs for severe EOS provided significantly better major curve correction with significantly fewer unplanned revisions than TGRs at a 2-year follow-up.

Lengthening Behavior of Magnetically Controlled Growing Rods in Early-Onset Scoliosis

“…Lebon et al performed an MCGR survival analysis and found that, at 27.9 months, 50% of the patients required a revision, which is consistent with the findings in our study 6 . Notably better survival rates were found by Saarinen et al, who compared TGRs and MCGRs in patients with EOS curves of ≥90° 19 . Those authors found that the 2-year survival free from unplanned revision was 91% for MCGR versus 71% for TGR.…”

The evolving stall rate of magnetically controlled growing rods beyond 2 years follow-up

“…However, with the introduction of any new technology, there are also new mechanisms of failure, and the failure of implant distraction, termed implant stalling, is exclusive to MCGR. MCGR stalling has been recognized as the most common surgeon-reported reason for implant removal [9,10], with failure of distraction occurring in upwards of 40% of treated children [2][3][4]. However, this has been shown to vary from as low as approximately 10% of children at 2-years post-implantation [2] to as high as 48% at more than 3 years post-implantation [4].…”

“…MCGR stalling has been recognized as the most common surgeon-reported reason for implant removal [9,10], with failure of distraction occurring in upwards of 40% of treated children [2][3][4]. However, this has been shown to vary from as low as approximately 10% of children at 2-years post-implantation [2] to as high as 48% at more than 3 years post-implantation [4]. In the current study, we found a time dependent association between MCGR stalling and follow-up post-implantation, ranging from 50% at 2 years post-implantation to > 80% at 4 years.…”

“…The magnetically − controlled growing rod (MCGR) system was introduced in the United States in 2014 as a revolutionary treatment approach that obviated the need for surgical lengthening of the growing rod, using instead an external remote controller to drive the lengthening of the spinal rod through the magnetic actuator [1]. Early reports assessing outcomes 2 years following implantation demonstrated high rates of success in managing these complex deformities with substantially lower complication rates compared to traditional growing rods (TGR) [1,2]. However, more recent series using small sample sizes have assessed outcomes beyond 2 year's follow-up, showing that upwards of 52% of MCGR's fail to lengthen [3][4][5].…”

What’s New in Pediatric Orthopaedics

“…A case-matched comparison of patients with severe early-onset scoliosis ( ‡90°) treated with magnetically controlled growing rods compared with traditional growing rods showed that the 2-year unplanned revision-free survival was 91% in the magnetically controlled growing rod group compared with 71% in the traditional growing rod group 15 . Mathew et al found that serum titanium, cobalt, and chromium levels were elevated in children with spinal implants, particularly with growing spine devices, although the clinical importance of this remains uncertain 16 .…”