Vertebral bone quality in patients with adolescent idiopathic scoliosis

In adolescent idiopathic scoliosis (AIS), the choice of upper and lowest instrumented vertebrae and related complications remain debated. Bone quality is a relevant factor in this context. The vertebral bone quality (VBQ) score has recently been proposed as a radiation-free magnetic resonance imaging (MRI)-based measure of bone quality. However, the role of the VBQ score in AIS and its relationship with the severity of scoliosis characteristics has not yet been explored. We hypothesize that the VBQ score is associated with key features of AIS, including curve type, Cobb angle, lumbar modifier, and thoracic kyphosis.

This retrospective study included AIS patients who underwent posterior spinal fusion between 2011 and 2025 at a university hospital. The lumbar VBQ score was determined using preoperative MRI, and the Lenke classification was assessed based on preoperative radiographs. To ensure comparability, curve types were categorized based on the flexibility of the lumbar curvature into non-structural (Lenke types 1 and 2) and structural (Lenke types 3 to 6) groups. The association between VBQ and curve type, Cobb angle, lumbar modifier, and thoracic kyphosis-while considering MRI field strength, age, sex, and body mass index (BMI)-was analyzed using multiple linear regression analyses.

This single-center study included 60 patients (male: 15%, female: 85%) with a median age of 15 years (interquartile range (IQR): 14-16 years) and a median BMI of 18.9 kg/m2 (IQR: 17.5-22.4 kg/m2), diagnosed with AIS presenting with non-structural (55%) and structural (45%) lumbar curves. A significant association was found with lumbar curve flexibility (r2 = 0.298, p = 0.035), indicating that structural lumbar curves correlated with lower bone quality. Additionally, female patients showed significantly better bone quality (r2 = -0.446, p = 0.005). No significant correlation was observed between the VBQ score and Cobb angle (r2 = -0.003, p = 0.370), thoracic kyphosis (r2 = 0.001, p = 0.734), lumbar modifier (r2 = -0.116, p = 0.123), MRI field strength (r2 = -0.181, p = 0.098), age (r2 = 0.018, p = 0.558), or BMI (r2 = -0.014, p = 0.275).

Our study demonstrated a significant correlation between the VBQ score and both lumbar curve flexibility and sex. Opportunistic assessment of the VBQ score may therefore be particularly useful in male patients with a structural lumbar curve to identify individuals who may benefit from further evaluation of bone quality.