1. Copyright © 2015 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited Supplemental PowerPoint Slides Mechanical Contribution of the Rib Cage in the Human Cadaveric Thoracic Spine Erin M. Mannen 1, John T. Anderson 2, Paul M. Arnold 3, Elizabeth A. Friis 4 1 The University of Kansas, Department of Mechanical Engineering, Lawrence, KS, USA, 1530 W 15th St., Learned Hall Room 3138, Lawrence, KS 66045, erinmannen@gmail.com 2 Children’s Mercy Hospital and Clinics of Kansas City, Orthopaedic Surgery, Kansas City, MO, USA, 2401 Gillham Rd., Kansas City, MO 64108, (816) 234-3693, jtanderson@cmh.edu 3 The University of Kansas Medical Center, Neurosurgery, Kansas City, KS, USA, 3901 Rainbow Blvd. MS 3021, Kansas City, KS 66160, (913) 588-7587, parnold@kumc.edu 4 The University of Kansas, Department of Mechanical Engineering, Lawrence, KS USA, 1530 W 15th St., Learned Hall Room 3138, Lawrence, KS 66045, (785) 864-2104, lfriis@ku.edu

2. Study Design and Methods Study Design. An in vitro biomechanical human cadaveric study of T1-T12 thoracic specimens was performed with four conditions (with and without rib cage, instrumented and uninstrumented) in flexion-extension, lateral bending, and axial rotation. The objective was to understand the influence of the rib cage on motion and stiffness parameters of the human cadaveric thoracic spine. Methods. Seven human cadaveric spine specimens (T1-T12) with four conditions (with and without rib cage, instrumented and uninstrumented) were subjected to 5 Nm pure moments in flexion-extension, lateral bending, and axial rotation. Range-of-motion, neutral and elastic zones, neutral and elastic zone stiffness values, and out-of-plane rotations were calculated for the overall specimen.

3. Key Points and Data In-plane range-of-motion is significantly higher without a rib cage for most modes of bending. Neutral zone stiffness is significantly higher with a rib cage present. Testing without a rib cage yields different motion and stiffness measures, directly impacting the translation of research results to clinical interpretation. Researchers should consider differences in testing without a rib cage when evaluating the mechanical impact of surgical procedures or instrumentation in cadaveric or computational models. Figure 4 Figure 5