Dual growing rod treatment in early onset scoliosis: the effect of repeated lengthening surgeries on thoracic growth and dimensions.

PURPOSE: To investigate changes in thoracic dimensions (TDs) following repeated lengthening surgeries after dual growing rod treatment of early onset scoliosis and thereby its effect on thoracic growth.
METHODS: All EOS patients treated with dual growing rod technique in Peking Union Medical College Hospital from June 2004 to June 2014 were retrospectively reviewed. Thoracic spine height (T1-T12), total spine height (T1-S1), maximal coronal chest width and pelvic inlet width (PIW) were measured on the posteroanterior X-ray images after initial growing rod insertion surgery and after each lengthening surgery. Absolute TDs measurements were normalized by PIW. Changes of absolute and normalized TDs measurements with age and number of lengthening surgeries were analyzed.
RESULTS: Radiographs of 229 surgeries of 53 EOS patients were measured, including 49 images after initial growing rod insertion surgery and 180 images of lengthening surgeries. Significant positive correlations between age and all three absolute TDs were found (P < 0.01) whereas significant negative correlations between age and all three normalized TDs (P < 0.01) were identified. Similarly, negative correlations were also identified between number of lengthening surgeries and the three normalized TDs (P < 0.01). Significant differences of normalized TDs were identified between initial surgery and the first lengthening through covariance analysis (P < 0.01). Yet, such differences were seldom seen between every two adjacent lengthening surgeries.
CONCLUSIONS: Growing rod technique could maintain TDs growth through repeated lengthening procedures but the growth rate was compromised as the number of lengthening procedures increased.