Higher Baseline Serum Myokine of FSTL1 May Serve as a Potential Predictive Biomarker for Successful Brace Treatment in Girls With Adolescent Idiopathic Scoliosis

Study Design. A retrospective case-control study Objective. This study aimed to investigate whether myokine, which is related to exercise and muscle mass, could serve as a biomarker for predicting bracing outcomes. Summary of Background Data. Several risk factors have been documented to be associated with bracing failure in patients with Adolescent Idiopathic Scoliosis (AIS). However, serum biomarkers have not been extensively explored. Methods. Skeletally immature females with AIS, without previous histories of bracing or surgery, were included. Peripheral blood was collected at the time of bracing prescription. Baseline serum concentrations of eight myokines (apelin, fractalkine, BDNF, EPO, osteonectin, FABP3, FSTL1, and musclin) were measured by multiplex assays. Patients were followed up until weaned from bracing and then designated as a Failure (defined as Cobb angle progression >5°) or Success. A logistic regression analysis was performed that accounted for serum myokines and skeletal maturity. Results. We included 117 subjects, with 27 in the Failure group. Subjects in the Failure group had lower initial Risser sign, and lower baseline serum levels of myokines including FSTL1 (2217.3 ± 617.0 vs. 1369.3 ± 704.9 , P =0.002), apelin (116.5(12.0,335.9) vs 83.5(10.5, 221.1) , P =0.016), fractalkine (979.6 ± 457.8 vs. 743.8 ± 456.1 , P =0.020), and musclin (211.3(16.3,370.3) vs 67.8(15.5,325.6) , P =0.049) . Following adjusted analysis, serum FSTL1 (OR=10.460; [2.213-49.453]) was determined to be predictive of bracing effectiveness. Conclusion. Patients who failed AIS bracing had significantly lower mean baseline levels of FSTL1 than those who achieved Success. FSTL1 may serve as a biomarker that can inform outcome following bracing.