4:03 The growth of the thoracic spine in congenital scoliosis after expansion thoracoplasty

Purpose of study: 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 effects on the thoracic spine by surgery is said to be neglectable, because it is assumed that the concave side of such curves and the unilateral unsegmented bars do not grow, but we are unaware of any conclusive studies regarding this assumption. Methods used: We measured the change in length of the thoracic spine on the concave, convex, anterior and posterior vertebral edges and the anterior surface of the posterior arch in 21 children (13 male, 8 female) with congenital scoliosis treated through expansion thoracoplasty by titanium rib prosthesis. Eleven unilateral unsegmented bars were also measured in 10 patients. Three of these children had undergone posterior spinal fusion before titanium rib implantation. Measurements were obtained using a three-dimensional software program (Vitrea 2, Vital Images, Inc, Minneapolis, MN), assessing baseline computed tomography (CT) scans and the latest follow-up scans. The technique was validated through measurement of a small female adult cadaver thorax. of findings: The average age at the baseline CT scan was 3.3 years, the average follow-up time 4.2 years (range, 1.8 to 6.2 years). An average of 7.6 prosthesis expansion surgeries (range, 1 to 16) were performed within the follow-up time. All patients on average showed significant growth (p<.0001) of the concave side of the thoracic spine (7.9 mm increase in length per year, 7.1% increase per year) and the convex side (8.3 mm increase in length per year, 6.4% increase per year) with no significant difference (p=.38) between sides. Unilateral unsegmented bars showed an average of 7.3% increase in length (p<.0001). Younger children showed more growth than older ones. In the three children with prior spinal fusion, the increase in length of the concave side of the thoracic spine was only 2.2 mm/year (2%/year) and the convex side 2.2 mm/year (3%/year), but both increases were significant (p<.0001). There was no correlation between the numbers of expansion surgeries and spinal growth. Relationship between findings and existing knowledge: Our findings suggest that thoracic unilateral unsegmented bars, thought incapable of growth in past literature, can grow when expansion thoracoplasty is performed. 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. Overall significance of findings: In children with congenital scoliosis treated through expansion thoracoplasty by titanium rib prosthesis, both concave and convex sides of the thoracic spine and unilateral unsegmented bars grow, allowing the thoracic spine to grow in length. Our results also suggest that younger children with prior spine fusion have less growth of the thoracic spine than children without spine fusions. Disclosures: Device or drug: Vertical Expandable Prosthetic Titanium Rib (VEPTR). Status: investigational. Conflict of interest: Robert Campbell, Jr., grant research from National Organization of Rare Disorders, FDA; Robert Campbell, Jr., Royalties, Synthes Spine Co.