Early postoperative serum metal profiles and subsequent revision-related surgery after instrumented fusion for adolescent idiopathic scoliosis.

BACKGROUND

Circulating titanium (Ti), cobalt (Co), and chromium (Cr) can increase after spinal instrumentation for adolescent idiopathic scoliosis (AIS), but their relation to later revision surgery is uncertain.

METHODS

This was a single-centre retrospective prognostic model-development study with a six month landmark. The cohort comprised 154 patients with AIS who underwent posterior instrumented fusion and had serum Ti, Co, and Cr measured at one and six months. Only revision-related procedures performed after six months were counted as outcomes. Log₂-transformed metal concentrations were examined in prespecified logistic models. Performance was assessed by AUC, Brier score, calibration, decision curve analysis, and risk-stratum event rates. Internal validation used 1000 bootstrap resamples to estimate optimism-corrected AUCs and Brier scores.

RESULTS

Sixty patients underwent later revision-related surgery and 94 did not. Ti and Co were higher in the revision group, with the largest difference for Ti at one month. The primary one month Ti/Co/Cr model had an apparent AUC of 0.926 and an optimism-corrected AUC of 0.918. The corresponding Brier scores were 0.099 and 0.108. Revision rates across predicted-risk were 3.8%, 23.5%, and 90.2%. In a sensitivity analysis restricted to implant loosening, the optimism-corrected AUC was 0.876.

CONCLUSIONS

Early postoperative serum metal profiles were associated with later revision-related surgery after AIS fusion. The one month Ti/Co/Cr model provided the most favourable balance between early availability, parsimony, and discrimination. Its clinical utility requires external validation and comparison with conventional clinical and imaging predictors.