title: Sagittal rotational stiffness and damping increase in a porcine lumbar spine with increased or prolonged loading.
abstract: While the impact of load magnitude on spine dynamic parameters (stiffness and damping) has been reported, it is unclear how load history (exposure to prolonged loading) affects spine dynamic parameters in sagittal rotation. Furthermore, it is unknown if both spine stiffness and damping are equally affected to prolonged loading. Using a pendulum testing apparatus, the effect of load magnitude and load history on spine sagittal rotational stiffness and damping was assessed. Nine porcine lumbar functional spine units (FSUs) were tested in an increasing compressive load phase (ICP: 44.85, 68.55, 91.75, 114.6kg) and then a decreasing compressive load phase (DCP: 91.75, 68.55, and 44.85kg). Each trial consisted of flexing the FSU 5° and allowing it to oscillate unconstrained. During the ICP, both stiffness and damping linearly increased with load. However, in the DCP, stiffness and damping values were significantly higher than the identical load collected during the ICP, suggesting load history affects sagittal rotational dynamic parameters. In addition, spine damping was more affected by load history than spine stiffness. These results highlight the importance of controlling load magnitude and history when assessing spine dynamic parameters.
authors.affiliation: Michigan State University Center for Orthopedic Research, Department of Osteopathic Surgical Specialties, College of Osteopathic Medicine, East Lansing, MI, United States. Electronic address: rlz@msu.edu.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Zondervan
authors.affiliation: Michigan State University Center for Orthopedic Research, Department of Osteopathic Surgical Specialties, College of Osteopathic Medicine, East Lansing, MI, United States.
authors.forename: John M
authors.initials: JM
authors.lastname: Popovich
authors.affiliation: Michigan State University Center for Orthopedic Research, Department of Osteopathic Surgical Specialties, College of Osteopathic Medicine, East Lansing, MI, United States.
authors.forename: Clark J
authors.initials: CJ
authors.lastname: Radcliffe
authors.affiliation: Michigan State University, Department of Statistics and Probability, East Lansing, MI, United States.
authors.forename: Pramod K
authors.initials: PK
authors.lastname: Pathak
authors.affiliation: Michigan State University Center for Orthopedic Research, Department of Osteopathic Surgical Specialties, College of Osteopathic Medicine, East Lansing, MI, United States.
authors.forename: N Peter
authors.initials: NP
authors.lastname: Reeves
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D019245:Compressive Strength; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology*; D008422:Materials Testing; D055595:Mechanical Phenomena; D016059:Range of Motion, Articular; D012399:Rotation; D013552:Swine; D013997:Time Factors; D016474:Weight-Bearing
keywords: Damping; Dynamics; Functional spinal unit; In vitro testing; Loading; Lumbar spine; Pendulum; Spine; Stiffness; Weight-bearing