Growth of the thoracic spine in congenital scoliosis after expansion thoracoplasty.

BACKGROUND: Children with congenital thoracic scoliosis associated with fused ribs with a unilateral unsegmented bar adjacent to convex hemivertebrae will invariably have curve progression without treatment. Surgery has been thought to have a negligible growth-inhibition effect on the thoracic spine in such patients because it has been assumed that the concave side of the curve and the unilateral unsegmented bar do not grow, but we are unaware of any conclusive studies regarding this assumption.
METHODS: The changes in the length of the concave and convex sides, anterior and posterior vertebral edges, posterior arch, and unilateral unsegmented bars of the thoracic spine were measured in the twenty-one children with congenital scoliosis and fused ribs after expansion thoracoplasty had been carried out with use of a vertical, expandable titanium prosthetic rib. Three of these children had undergone posterior spinal fusion previously. Measurements were made with use of a three-dimensional software program that analyzed baseline and follow-up computed tomography scans. The technique was validated through measurement of the thorax of a small female adult cadaver.
RESULTS: The patients without spine fusion had an average age of 3.3 years at the time of the baseline computed tomography scan, and the average duration of follow-up was 4.2 years. On the average, these patients showed significant growth (p < 0.0001) of the concave side of the thoracic spine (an increase in length of 7.9 mm/yr, or 7.1%/yr) and the convex side (8.3 mm/yr, or 6.4%/yr) compared with the baseline lengths. There was no significant difference in the increases in length (p = 0.38) between the concave and convex sides. Eleven patients with an unsegmented bar had an average 7.3% increase in the length of the bar (p < 0.0001). In the three children with prior spinal fusion, the increase in length averaged only 4.6 mm/yr (3%/yr) on the concave side of the thoracic spine and 3.7 mm/yr (2.2%/yr) on the convex side; both increases were significant (p < 0.0001).
CONCLUSIONS: Longitudinal growth of the thoracic spine in a normal child has been estimated to be 0.6 cm/yr between the ages of five and nine years. After expansion thoracoplasty, growth of the thoracic spine was approximately 8 mm/yr in our series of children with congenital scoliosis and fused ribs. After expansion thoracoplasty, both the concave and the convex side of the thoracic spine and unilateral unsegmented bars appeared to grow in these patients. When a thorax is already foreshortened by congenital scoliosis, control of spine deformity with expansion thoracoplasty allows growth of the thoracic spine, and it is likely that the longer thorax provides additional volume for growth of the underlying lungs with probable clinical benefit. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.