Low bone mineral density in non-ambulatory adolescents relates to lower correction of neuromuscular scoliosis after posterior spinal fusion.

Purpose

Non-ambulatory adolescents with neuromuscular scoliosis (NMS) often require surgical intervention. The purpose of this study was to examine whether low bone mineral density (BMD) affects the results of posterior spinal fusion.

Methods

Volumetric BMD (vBMD) was measured in preoperative computed tomography (CT) scans of scoliotic patients with Duchenne Muscular Dystrophy (DMD), Spinal Muscular Atrophy (SMA), Cerebral Palsy (CP) and Rett syndrome (RTT). CT scans of healthy age-matched adolescents were used to define reference vBMD values and to calculate Z-scores. Scoliosis angles were measured in preoperative and postoperative radiograms to evaluate neuromuscular spinal deformity correction.

Results

Initial scoliosis angles of 169 patients with NMS were 83 ± 31°. PSF improved deformities to 33 ± 21° with an overall correction of 60.8 ± 16.4%. All patients (n=169) had significantly lower vBMD values in comparison to age-matched healthy controls (n=87). Patients with DMD (n=55) had lowest vBMD for age values, followed by patients with SMA (n=34), CP (n=52) and RTT (n=28). Significantly lower Z-scores (- 2.5±1.5 versus - 1.7±1.3) were found in adolescents with poor scoliosis correction in comparison to those with good results. A higher initial scoliosis angle had a negative effect on the deformity correction (R2=0.089).

Conclusion

All adolescents with NMS had significantly lower vBMD in comparison to age-matched controls. Lower vBMD values were associated with poor spinal deformity correction of 60% and less.