Growth of the Thoracic Spine in Congenital Scoliosis After Expansion Thoracoplasty

· (a - Orphan Products Division of Food and Drug Administration, c - Synthes Spine Company)

Department of Orthopedics, University of Texas Health Science Center at San Antonio
San Antonio, Texas, USA

PURPOSE:
Children with congenital thoracic scoliosis associated with fused ribs with unilateral unsegmented bars adjacent to convex hemivertebra will invariably have curve progression without treatment. The growth inhibition effect on height of the thoracic spine by surgery in such patients is said to be neglectable because it is assumed that the concave side of such curves does not grow, but we are unaware of any conclusive studies regarding this assumption.

METHODS:
We measured the concave/convex and the front/back/posterior arch length of the thoracic spine in 21 children (13 male, 18 female) with congenital scoliosis and fused ribs treated by expansion thoracoplasty. Eleven unilateral unsegmented bars were also measured in ten patients. Three children had spinal fusion prior to titanium rib implantation. Measurements were obtained using a three-dimensional software program (VITREA®2, Virtual Images Inc., Minn. USA) by assessing baseline computed tomography (CT) scans and the latest follow up scans. The technique was validated through measurement of a small adult female cadaver thorax.

RESULTS:
The average age at the baseline CT scan was 3.3 years, the average followup time 4.2 years (1.8 - 6.2 years). Each patient had an average of 7.6 expansion surgeries performed. All patients on the average showed significant growth of both the concave side of the thoracic spine (7.9mm growth/year, 7.1% growth/year) and the convex side (8.3mm growth/year, 6.4% growth/year). There was no significant difference between the growth rate of either side. Unilateral unsegmented bars showed a similar percentage growth rate. In the three children with prior spine fusions the growth rate was much less. Younger children showed more growth than older patients.

CONCLUSION:
In children with congenital scoliosis, who have been treated by expansion thoracoplasty, both the concave and convex sides of the thoracic spine grow, allowing the thoracic spine to grow in length. Our results also suggest that younger children with prior spinal fusion have less growth of the thoracic spine than patients without spinal fusions.

SIGNIFICANCE:
Continuing growth of the thoracic spine in such patients will likely result in a longer thorax, providing additional volume for growth of the underlying lungs with probable clinical benefit.