Anatomical and Biomechanical Factors in the Curve Pattern Formation of Idiopathic Scoliosis

Abstract

The maximum range of motion between two adjacent vertebrae without soft tissues was measured from C1-C2 down to L5-S and factors such as rotation, lateral bending, extension, and flexion, during surface contact movement of the facet joints, were investigated. Thirty human cadaveric spines were studied. It was found that the individual spines had a characteristic level-dependent difference in the capacity for elementary motions at the facet joints. Those segments with restricted motion capacity were termed “spinal nodes”. The human spine usually has three to four spinal nodes between the skull and the sacrum. They are C7-T1, T4-T5, T8-T9, and T11-T12. This intrinsic structural character of the human spine is expressed as “nodal motion structure”. We postulate that this structure plays an important role in the formation of curve patterns in idiopathic scoliosis and other spinal deformities.