title: Effect of follower load on motion and stiffness of the human thoracic spine with intact rib cage.
abstract: Researchers have reported on the importance of the rib cage in maintaining mechanical stability in the thoracic spine and on the validity of a compressive follower preload. However, dynamic mechanical testing using both the rib cage and follower load has never been studied. An in vitro biomechanical study of human cadaveric thoracic specimens with rib cage intact in lateral bending, flexion/extension, and axial rotation under varying compressive follower preloads was performed. The objective was to characterize the motion and stiffness of the thoracic spine with intact rib cage and follower preload. The hypotheses tested for all modes of bending were (i) range of motion, elastic zone, and neutral zone will be reduced with a follower load, and (ii) neutral and elastic zone stiffness will be increased with a follower load. Eight human cadaveric thoracic spine specimen (T1-T12) with intact rib cage were subjected to 5Nm pure moments in lateral bending, flexion/extension, and axial rotation under follower loads of 0-400N. Range of motion, elastic and neutral zones, and elastic and neutral zone stiffness values were calculated for functional spinal units and segments within the entire thoracic section. Combined segmental range of motion decreased by an average of 34% with follower load for every mode. Application of a follower load with intact rib cage impacts the motion and stiffness of the human cadaveric thoracic spine. Researchers should consider including both aspects to better represent the physiologic implications of human motion and improve clinically relevant biomechanical thoracic spine testing.
authors.affiliation: The University of Kansas, Bioengineering, 1530 W 15th Street, Learned Hall Room 3135A, Lawrence, KS 66045, USA.
authors.forename: Hadley L
authors.initials: HL
authors.lastname: Sis
authors.affiliation: The University of Kansas, Mechanical Engineering, 1530 W 15th Street, Learned Hall Room 3138, Lawrence, KS 66045, USA.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Mannen
authors.affiliation: The University of Kansas, Bioengineering, 1530 W 15th Street, Learned Hall Room 3135A, Lawrence, KS 66045, USA.
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Wong
authors.affiliation: The University of Kansas, Bioengineering, 1530 W 15th Street, Learned Hall Room 3135A, Lawrence, KS 66045, USA.
authors.forename: Eileen S
authors.initials: ES
authors.lastname: Cadel
authors.affiliation: Beth Israel Deaconess Center, Harvard Medical School, 330 Brookline Ave, RN 115, Boston, MA 02215, USA.
authors.forename: Mary L
authors.initials: ML
authors.lastname: Bouxsein
authors.affiliation: Beth Israel Deaconess Center, Harvard Medical School, 330 Brookline Ave, RN 115, Boston, MA 02215, USA.
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Anderson
authors.affiliation: The University of Kansas, Bioengineering, 1530 W 15th Street, Learned Hall Room 3135A, Lawrence, KS 66045, USA; The University of Kansas, Mechanical Engineering, 1530 W 15th Street, Learned Hall Room 3138, Lawrence, KS 66045, USA. Electronic address: lfriis@ku.edu.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Friis
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D004548:Elasticity; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement; D016059:Range of Motion, Articular; D000070602:Rib Cage / Q000502:physiology*; D012399:Rotation; D013904:Thoracic Vertebrae / Q000502:physiology*; D016474:Weight-Bearing
keywords: Biomechanics; Follower load; Rib cage; Thoracic spine