US researchers performed postoperative imaging analyses in children with spinal muscular atrophy (SMA) type 2 and found a 40% prevalence of sagittal deformities occurring above and below posterior instrumentation, according to a study published in Children.
SMA causes progressive muscle weakness and atrophy, eventually leading to early mortality. It is divided into 3 types based on disease onset; type 2 usually presents between 6 and 18 months of age. In the Department of Orthopedic Surgery in the University of Nebraska Medical Center in Omaha, physicians identified 2 key spinal deformities associated with SMA type 2 following posterior instrumentation surgery:
- “Tucked chin deformity,” in which the patient’s jaw appears retracted
- “Tipped trunk deformity,” where the patient’s unsupported trunk leans forward, resulting in the abdomen resting on the thighs while sitting.
Researchers sought to determine the prevalence of these deformities in SMA patients who have undergone posterior instrumentation. Thirty-two patients with SMA type 2 who had received growing rods (n=12) or had spinal fusion performed (n=20) between 1993 and 2015 were recruited for this study.
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A radiology examination was performed on the selected participants, and the results found that 13 patients (40%) had an obvious “tucked chin deformity,” “tipped trunk deformity,” or both. There was no statistically significant difference between patients who received growing rods or those who underwent spinal fusion surgery.
What could explain the remaining deformities after spinal surgery? The researchers of this study theorized, “From our data, it appears, that children with SMA type 2 are sensitive to hypokyphosis (or excessive overall relative lordosis, subtracting the lumbar lordosis from the thoracic kyphosis) following spinal instrumentation.”
In view of the possibility of lordotic imbalances occurring through continued anterior growth and giving rise to sagittal deformities postoperatively, the authors of the study recommend “caution in the complete correction or overcorrection of thoracic kyphosis during spinal instrumentation.” Further follow-up studies are needed to identify ways to avoid or correct these deformities in the long term.
Halanski MA, Hanna R, Bernatz J, et al. Sagittal plane deformities in children with SMA2 following posterior spinal instrumentation. Children (Basel). 2021;8(8):703. doi:10.3390/children8080703