Introduction: The primary aims of scoliosis surgery are to halt the progression of the deformity, and to reduce its severity (cosmesis). Currently, deformity correction is measured in terms of posterior parameters (Cobb angles and rib hump), even though the cosmetic concern for most patients is anterior chest wall deformity. In this study, we propose a new measure for assessing anterior chest wall deformity and examine the correlation between rib hump and the new measure.
Methods: 22 sets of CT scans were retrieved from the Paediatric Spinal Research Database. The Image J software (NIH) was used to manipulate formatted CT scans into 3‐dimensional anterior chest wall reconstructions. A & #8216;chest wall angle' was then measured in relation to the first sacral vertebral body. Two observers measured chest wall angles on two separate occasions one week apart. Inter and intra observer measurement differences were calculated for the new measure, and results correlated to clinical rib hump measurements for the same patients.
Results: The new anterior deformity measure was used to assess 22 sets of CT data (11 preop and 11 postop). Correlation analysis and linear regression were performed to investigate the relationship (if any) between rib hump and the new anterior deformity measure. The mean absolute intraobserver difference (repeated measures of anterior deformity by the same observer) was 0.9° (range 0–3°, SD 0.7°). The interobserver error (SD of the difference between measurements by 2 different observers) was ✓ 2xSD=1.6°. There was no statistically significant relationship between anterior deformity and rib hump (linear regression R2=0.001, correlation coefficient =0.03).
Conclusion: The chest wall angle is a reliable tool in the analysis of chest wall deformity. No correlation was found between the new measure and rib hump angle. This suggests that there is no correlation between anterior and posterior deformity measures. While most surgical procedures will adequately address the coronal imbalance & posterior rib hump elements of scoliosis, they do not reliably alter the anterior chest wall shape.
Significance: This study suggests that anterior chest wall deformity is to a large degree an intrinsic deformity, not directly related to vertebral rotation.