Internal mechanism failure of magnetic controlled growing rods (MCGRs) for early-onset scoliosis: a systematic review of implant retrieval analysis studies.

purposeMagnetic controlled growing rods (MCGRs) are used to treat early-onset scoliosis when nonsurgical options fail, controlling curve progression and allowing for continued spinal growth. Recent reports of unplanned reoperations and mechanical failure of MCGRs have led to further research. This is a systematic review on the retrieval analysis of explanted MCGR rods. Understanding the failure mechanisms will shed light on the survivorship and complications associated with the implant.

methodsA Medline and EMBASE database search was performed, looking at all variations in the terms "magnetic controlled growing rods" and the terms "retrieval/explant/metallosis" All published retrieval analysis studies of MCGR were included, and all clinical outcome studies, biomechanical testing studies, review articles, and case reports were excluded. Data were collected regarding the source, year, and aim of the study; number of patients and rods analysed; duration of implantation; and main findings and conclusions.

resultsNine studies (454 rods) reported metallosis due to O-ring damage (67%), internal mechanism failure of locking pins (45%) and rod fracture (7%) in all MCGR generations. Actuator locking pin fractures reported in 174 rods (38.3%) continue to persist despite newer implant iterations. The pin fracture rates decreased from 52% in MAGEC 1.3 to 15% in MAGEC X.

conclusionsMCGR failure is multifactorial, and metallosis is of significant concern because of the unknown long-term effects in patients. Early recognition and revision of existing rods in situ is essential, along with continued efforts to reduce mechanical failure in future iterations of MAGEC. LEVELS OF EVIDENCE: MCGR failure is multifactorial, and metallosis is of significant concern because of the unknown long-term effects in patients. Early recognition and revision of existing rods in situ is essential, along with continued efforts to reduce mechanical failure in future iterations of MAGEC. This systematic review provides Level III evidence on failure mechanisms in MCGR, as the results were obtained from Level III studies. The levels of evidence for all relevant references can be found in the reference section. LEVEL II: [1-4]. LEVEL III: [5-34]. LEVEL IV: [35-44]. LEVEL V: [45-50].