Clinical evaluation of the anterior chest wall deformity in thoracic adolescent idiopathic scoliosis.

STUDY
DESIGN: A retrospective radiographical study of pre- and postoperative anterior chest wall shape in thoracic adolescent idiopathic scoliosis.
OBJECTIVE: To assess the anterior chest wall deformity and define its relationship with other deformed components in adolescent idiopathic scoliosis. The surgical influence on the deformed chest wall contour was also evaluated to improve the clinical recognition of the risk factors associated with aggravated chest wall shape postoperatively. SUMMARY OF BACKGROUND DATA: Anterior chest wall deformity is one of the major cosmetic concerns that may be attributable to rotational coupling in adolescent idiopathic scoliosis. Patients could be quite different in their anterior chest wall appearance with similar spinal angulation. The surgical improvement of this deformed chest wall shape is also quite elusive and the reverse could also happen despite excellent correction in Cobb angle. We investigated whether or not the anterior chest wall deformity was independent in the severity from the codevelopment of spinal curvature, translation, and vertebral rotation.
METHODS: In this retrospective study, 110 sets of computed tomographic scans, 70 of which had both pre- and postoperative images, were retrieved and analyzed. The ImageJ software (National Institutes of Health, Bethesda, MD) was used to manipulate formatted computed tomographic scans into 3-dimensional anterior chest wall reconstructions. Multiple anterior and posterior deformity parameters were evaluated, correlated, and compared.
RESULTS: The preoperative Cobb angle of major thoracic curve, chest wall angle (CWA), rib hump (RH), angle of the sternum relative to the apical vertebral body (α), sternum-rib ratio (S-R ratio), apical vertebral rotation (AVR), and angle of trunk rotation (ATR) averaged 54.4° ± 15.2°, 5.4° ± 3.9°, 14.7° ± 5.4°, 80.5° ± 7.8°, 1.3° ± 0.2, 12.3° ± 6.5°, and 8.8° ± 4.6°, respectively. The thoracic Cobb angle demonstrated moderate correlation with CWA, RH, α, S-R ratio, AVR, and ATR (r = 0.377, 0.604, -0.401, 0.514, 0.530, and 0.517, respectively, P < 0.001). The RH demonstrated moderate correlation with AVR (r = 0.546, P < 0.001). No statistically significant relationships between CWA and RH, AVR, and ATR were detected (r = 0.129, 0.043, -0.039, P > 0.05). The AVR demonstrated significant correlation with α and S-R ratio (r = -0.757, P < 0.001; r = 0.213, P < 0.05). Averaged CWA with different curve apex showed a normal distribution shape, with the highest at T9 level. The postoperative thoracic Cobb angle, S-R ratio, AVR, and ATR improved significantly (P < 0.05), with the exception of the postoperative CWA and α (P > 0.05). Postoperative |CWA| aggravated in 52.8% of the patients, with 38.6% beyond 5°, which showed a significantly lower average preoperative CWA (3.0° ± 2.8°) compared with the rest of patients with decreased CWA (7.9° ± 3.1°) (P < 0.001).
CONCLUSION: Idiopathic scoliosis is associated with distinctive anterior chest wall deformity, with its variations partially attributable to Cobb angle and apex location, but not directly correlated with AVR. Incidence of aggravated postoperative anterior chest wall shape is notable in our study, and patients should be informed of this risk beforehand. Small preoperative CWA and apical vertebra located above T9 were associated with relatively higher risk of postoperative chest wall shape aggravation.