Objectives: To investigate the association between matrilin-1 gene polymorphism and bracing effectiveness in adolescent idiopathic scoliosis girls.
Methods: In a prospective study, AIS girls treated with standard bracing from January 2005 to December 2008 were included and followed up. All subjects of the study met the following criteria: female; skeletally immature (Risser sign grade 0 - 3); before menarche or < 1.5 years after menarche; Cobb angle 20 degrees - 40 degrees ; scoliosis caused by congenital, neuromuscular and other cause were excluded; no evidence of bone diseases, metabolic diseases or other condition known to affect bone metabolism; no history of bracing before onset; follow-up with an interval of 3 months, and total follow-up time > 2 years. Subjects met one of the following conditions was excluded: the final follow-up time < 2 years; bad compliance (ratio of the actual daily wearing time to proposed wearing time) of bracing (< 75%); change of bracing without doctor's order. Cobb angle of major curve was recorded before the bracing initiation and at the final follow-up. A progression of 6 degrees or more was considered to be a failure of bracing. The rs1149048 polymorphism in promoter of matrilin-1 gene was chosen for genotyping by PCR-RFLP method. Differences in age at initial visit, Risser sign, Cobb angle and genotype distribution were compared between brace failure and brace success groups.
Results: Seventy seven patients with AIS were included, with a mean age at (13.0 +/- 1.5) years and a mean Cobb angle at (30.3 +/- 11.9) degrees . After an average duration of 2.6 years follow-up, mean Cobb angle was 30.3 degrees +/- 11.9 degrees . There were 19 cases (24.7%) in bracing failure and 58 cases (75.3%) in bracing success. The initial Cobb angle was larger in bracing failure group compared with bracing success group (P > 0.05). Patients with double major curve were found to have the lowest bracing failure rate (19.4%), but there was no significant difference compared with other curve patterns. Bracing failure rate was marked higher in individual with genotype GG (66.7%) than that with genotype AA or AG.
Conclusions: Progression of most mild or moderate AIS can be managed by early standardized bracing treatment. It is shown that large initial Cobb angle and genotype GG of matrilin-1 gene are indicative of less bracing effectiveness.