Do Rib-Based Anchors Impair Chest Wall Motion in Early Onset Scoliosis? - A Novel Investigation via Dynamic MRI

There is a concern in pediatric spine surgical practice that rib-based fixation may limit chest wall motion in early onset scoliosis (EOS). The purpose of this study is to assess the contribution of chest wall excursion to respiration before and after growth-friendly surgery.

Quantitative dynamic magnetic resonance imaging (QdMRI) is performed on 49 EOS patients (before and after surgery) and 191 normal children in this retrospective study. QdMRI is an image-based approach and allows for free-breathing image acquisition. Tidal volume parameters for chest walls (CWtv) and hemidiaphragms (Dtv) were analyzed on the concave and convex sides of the spinal deformity. EOS patients (1 to 14 y) and normal children (5 to 18 y) were enrolled, with an average interval of 2 years for dMRI acquisition before and after surgery.

CWtv significantly increased after surgery in all EOS patients ( P <0.05) by 51% for left CWtv and 41% for right CWtv without age correction, and 17% for LCWtv and 25% for right CWtv with age correction, respectively. For main thoracic curve (MTC) EOS patients, CWtv significantly improved after surgery by 50% (concave side) and 35% (convex side) after age correction ( P <0.05). The average ratio of Dtv to CWtv on the convex side in MTC EOS patients was not significantly different from that in normal children ( P =0.78). However, the concave side showed the difference to be significant ( P =0.019).

Chest wall component tidal volumes in EOS patients measured through QdMRI did not decrease after rib-based surgery, suggesting that rib-based fixation does not impair chest wall motion in pediatric patients with EOS. The proposed QdMRI method can be used to quantify the motion of the individual 3D chest wall and diaphragm before and after surgery, to assess deviations from normality, and to quantify alterations due to corrective surgery in EOS.

Level III evidence-retrospective study.