Children with spinal muscular atrophy have reduced vertebral body height, depth and pedicle size in comparison to age-matched healthy controls

The majority of children with spinal muscular atrophy (SMA) develop spinal deformity, which may require surgical intervention. In addition to poor bone stock, vertebral body shape may hinder the placement of spinal implants resulting in complications and poor outcome. The aim of this study was to analyze whether vertebral body morphology of SMA children and adolescents is altered in comparison to healthy age-matched controls. In this prospective cohort study, 17 SMA children (8.7 ±1.0 years) and 13 SMA adolescents (13.6 ±1.4 years), all with some degree of neuromuscular scoliosis were analyzed by standardized radiographic measurements to evaluate vertebral body height and depth. Results were compared to age-matched healthy controls (n=10; 9.1 ±1.6 years and n=20; 13.1 ±0.5 years). Computed tomography scans of 27 SMA adolescents (13.5 ±1.2 years) and 25 healthy age-matched controls (13.8 ±2.0 years) were analyzed to define pedicle diameters. All SMA children and adolescents had decreased vertebral height and depth in comparison to age-matched healthy controls. In adolescents, reduced depth was more pronounced than height in the thoracic spine. Pedicle size was significantly reduced in the lower thoracic and lumbar area. Reduced vertebral body height and depth as well as pedicle size in SMA children and adolescents may influence surgical treatment of spinal deformity. Surgeons should be aware of anatomical differences for choosing implant devices accordingly.