Introduction : Among the external manifestations of scoliosis, the rib hump constitutes one of the most disturbing aspects of the deformity for the patients. It may be associated to the axial rotations of the vertebrae, the ribs and the back surface. Only Stokes et al. studied the relations between those three variables, using spine and ribs 3D reconstructions obtained from non-standard radiographs and the reconstruction of the trunk's back.
Objectives : The objective of this study is to analyze the correlations between those three components, in a cohort of 13 patients with adolescent idiopathic scoliosis (AIS), using new reconstruction techniques.
Methods: For each patient, the surface of the whole trunk is acquired and reconstructed in 3D using the InSpeckĀ® system. The vertebrae and the ribs are reconstructed from standard frontal and lateral radiographs. The reconstructions are then merged using an elastic registration technique. Subsequently, for each thoracic level, the axial rotations of the vertebrae, the ribs and the corresponding trunk section are computed. Finally, a linear regression analysis is performed.
Results: Our results show a high correlation between the ribs and the back surface rotations, a lower correlation between the vertebrae and the back surface rotations and a low correlation between the ribs and the vertebrae rotations. Moreover, the vertebral rotation is generally higher in amplitude than the ribs and the back surface rotations.
Conclusion: This study indicates that ribs and back surface are closely related, but that back surface and vertebral rotation are not well correlated. It thus points out the importance of using trunk surface and not vertebral rotation to quantify the rib/chest asymmetry in AIS.