Reduced Vertebral Body Height, Depth May Influence Surgical Intervention of SMA, Says Study

The study included children and adolescents, and it found decreased vertebral height and depth among both groups of patients compared with healthy controls.

Young patients with spinal muscular atrophy (SMA) have reduced growth and shape of their vertebral bodies found a new study, with the researchers highlighting the findings as an important consideration for patients who receive surgery for spinal deformity.

These results appeared online recently in World Neurosurgery.

The study included children and adolescents, finding that among both groups of patients were decreased vertebral height and depth compared with healthy controls. According to the researchers, their findings have implications for decisions on implant devices, as many patients with SMA develop spinal deformity and subsequently need surgery.

“The combination of small pedicle size and reduced vertebral body depth will influence the selection of spinal implants (eg, pedicle screws). Performing dorsal spinal fusion in SMA adolescents, the surgeon has to be prepared to use smaller screws than usual in both diameter (eg, 4.5 mm) and length (eg, 25 to 35 mm) especially in the lower thoracic and lumbar area,” wrote the researchers. “Therefore, the described findings on SMA spinal morphology need to be taken into account when planning the respective surgical intervention in this patient group and will hopefully improve the selected implant precision in the near future.”

The researchers noted that further research is needed before their data can be included routinely in surgical planning procedures. They added that research will also be needed to compare the spinal morphology of other neuromuscular diseases.

In the current study, 17 children younger than 11 years were included; all were nonambulatory and had not had previous spinal surgery. Compared with 10 healthy controls, the children with SMA had a height of their anterior edge of the vertebrae that was significantly lower from T2 onward (13.7 vs 17.6 mm), and their anterior vertebral body height was 3.9 mm lower.

“Analyzing different regions of the spine, SMA children had less depth growth in the lower thoracic and lumbar region in comparison to healthy children during growth,” wrote the researchers, noting depths of 15.7 mm among the patients with SMA and depths of 26 mm among the controls. “This led to atypical vertebral body shapes of the lower thoracic and lumbar spine on radiographs. Inability to walk has been identified as a risk factor for reduced depth growth of the lumbar discs and vertebral bodies before 15, which corresponds with our data as all SMA children were nonambulatory.”

Consistent findings were observed among the group of adolescents aged 13 to 15 years. Compared with 20 healthy controls, the 13 patients with SMA had lower height of vertebral bodies, with vertebrae that were 5.6 mm shorter than those of the controls. The depths of vertebral bodies were also shorter among the patients compared with controls (average 17.7 vs 30 mm).

Significant differences in pedicles were also observed in patients with SMA, based on CT scans of 27 patients with SMA and 25 controls. According to the researchers, significant differences were predominantly in the lower thoracic and lumbar spine.

Reference

Hell A, Grages A, Braunschweig L, et al. Children with spinal muscular atrophy have reduced vertebral body height, depth and pedicle size in comparison to age-matched healthy controls. World Neurosurg. Published online June 16, 2022. doi:10.1016/j.wneu.2022.06.054