Lower Bone Mineral Density is Associated with Severity of Deformity in Adolescent Idiopathic Scoliosis.

Study design: Retrospective study.

Objective: To investigate the association between preoperative bone mineral density (BMD) and both physical and radiographic parameters in adolescent idiopathic scoliosis (AIS) patients undergoing correction and fusion surgery.

Summary of background: AIS is a multifactorial condition with a suspected polygenic basis. Osteopenia has been proposed as a contributing factor to curve progression, but the relationship between scoliosis severity and BMD remains unclear.

Methods: We retrospectively reviewed 348 AIS patients who had reached Risser sign grade 4 or 5 and underwent surgery. Preoperative total proximal femur BMD was measured and used to categorize patients into two groups: normal BMD (N group; Z-score > -1, n=242) and low BMD (L group; Z-score ≤ -1, n=106). Preoperative radiographic parameters were compared between the two groups. Correlation analysis was performed to assess the relationship between the Z-score of BMD, BMI, and Cobb angle. Multiple regression analysis was conducted to identify independent risk factors for Cobb angle.

Results: BMI was significantly lower in the L group (17.9±1.9 kg/m2) compared to the N group (19.6±2.3 kg/m2). The Cobb angle was significantly larger in the L group (59.3±11.8°) compared to the N group (51.4±9.1°). A significant positive correlation was observed between the Z-score of BMD and BMI (r=0.36, P<0.01), while a significant negative correlation was found between the Z-score of BMD and Cobb angle (r=-0.37, P<0.01). Multiple regression analysis revealed that the Z-score of BMD was an independent factor associated with Cobb angle.

Conclusion: AIS patient with lower BMD exhibited significantly larger Cobb angles, indicating the potential role of low BMD in curve progression. These findings suggest that addressing bone health in AIS patients could offer new strategies for mitigating curve severely.