The Biomechanical Contribution of the Free Floating Ribs: A Pilot Study

Abstract

Human cadaveric spine testing is done to provide more knowledge for clinicians in understanding living patients and to validate surgical procedures. There are many limitations to cadaveric testing, whether it be equipment or physiological condition of the specimen. Clinically, floating ribs have been removed for procedures for cosmetic purpose or surgical repair. The understanding of the floating ribs in human cadaveric testing is limited and has never been quantified. The present study aims to examine the mechanical effects of the thoracic spine when the floating ribs are removed. Eight human cadaveric thoracic spine specimens (T1-T12) with intact rib cage were subjected to 5 Nm pure moments in axial rotation, lateral bending, and flexion/extension with a 400 N follower load before and after floating rib removal. Data was collected and calculated to determine overall range of motion, neutral zone, elastic zone, neutral zone stiffness, elastic zone stiffness, and maximum and minimum dynamic pressure. Overall range of motion was the only parameter that saw significant differences in axial rotation and lateral bending. No other significant differences were found. The study demonstrated that the floating ribs do biomechanically contribute to the thoracic spine. Therefore, it is necessary to include the floating ribs for future thoracic and thoracolumbar studies.