Serum metal ion release by growing rod constructs: a systematic review and meta-analysis protocol

Abstract Introduction Severe early-onset scoliosis (EOS) is typically managed with the implantation of growing rods (GRs). However, there are increasing concerns regarding systemic metal ion release by GRs. Systemic toxicity due to metal ion release from orthopaedic implants has previously been seen in the setting of metal-on-metal total hip arthroplasty. Titanium release from GRs may be of particular concern given pre-clinical evidence linking TiO2 to possible neurotoxicity and teratogenicity. Materials and Methods A systematic review and meta-analysis will be conducted in accordance with PRISMA 2020 guidelines. PubMed, Embase and Cochrane Library will be searched from inception until 2025. Original articles reporting measures of blood metal ions will be included. Articles will be screened and extracted by two independent reviewers. Risk of bias will be assessed using the Newcastle–Ottowa Scale and the Joanna Briggs Institute checklist for case series. Meta-analysis will be performed in RStudio using a random effects model. Effect measures will be pooled mean and standardized mean difference with 95% CIs. Heterogeneity will be assessed using Cochran’s Q and I2 and sensitivity analysis will be conducted. Subgroup analyses will be performed for each type of GR. Ethical approval is not required. Discussion Our findings will provide insight into the effect of GRs on blood metal ion levels. In the light of emerging pre-clinical evidence of the potential toxicities associated with serum metal ions, this may influence clinical decision-making. By comprehensively synthesizing the existing literature on this topic, we will identify important directions for future research.