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(3)) and growth parameters was greater ( R-2 > 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 <= 45 degrees with a rib hump <= 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.