Influence of idiopathic scoliosis on three-dimensional thoracic growth.

STUDY DESIGN: Prospective clinical study of three-dimensional thoracic growth in children with idiopathic scoliosis and a reference group.

OBJECTIVE: To measure thoracic dimensions and volume in relation to growth and to verify the influence of scoliosis.

SUMMARY OF BACKGROUND DATA: Scoliosis represents a three-dimensional spinal deformity leading to thoracic deformity. Vertical expandable prosthetic titanium rib distraction primarily treats this deformity, but little is known about thoracic growth in scoliosis.

METHODS: One hundred and thirty children with scoliosis (20 boys, 110 girls; 4-16 years; curves 15 degrees -45 degrees ; rib hump 5-25 mm) were compared with 126 children without spinal deformity (61 boys, 65 girls). The ORTEN system was used for optical trunk surface data acquisition. Thoracic volume, perimeter, anterior-posterior and transversal diameters, T1-T12 and sternal lengths were calculated and related to age, weight, standing and sitting height.

RESULTS: There was no significant difference in thoracic volume between the 2 groups (P > 0.05). The correlation between thoracic volume (3-16 dm) and growth parameters was greater (R > 0.70) than with age. At 4 years, thoracic volume represents 33%, and at 10 years, it represents 55% of its volume at 16 years. It triples between 4 and 16 years and doubles during puberty. These relationships were constant in all groups. During growth, the transversal diameter corresponds to 30%, the anterior-posterior diameter represents 20% and the thoracic perimeter 100% of sitting height.

CONCLUSION: The thoracic deformity in scoliosis is measurable with ORTEN, but scoliosis <or=45 degrees with a rib hump <or=25 mm does not significantly influence thoracic volume. Thoracic parameters should be related to sitting height rather than age. Established relationships give a reliable indication of thoracic proportions, which are useful for understanding global spinal and thoracic deformity and for optimizing braces or surgical strategies. Further investigations are required for curves >45 degrees , leading to major thoracic asymmetry.