title: Load-displacement properties of the normal and injured lower cervical spine in vitro.
abstract: The objective of this study was to determine which discoligamentous structures of the lower cervical spine provide significant stability with regard to different loading conditions. Accordingly, the load-displacement properties of the normal and injured lower cervical spine were tested in vitro. Four artificially created stages of increasing discoligamentous instability of the segment C5/6 were compared to the normal C5/6 segment. Six fresh human cadaver spine segments C4-C7 were tested in flexion/extension, axial rotation, and lateral bending using pure moments of +/- 2.5 Nm without axial preload. Five conditions were investigated consecutively: (1) the intact functional spinal unit (FSU) C5/6; (2) the FSU C5/6 with the anterior longitudinal ligament and the intertransverse ligaments sectioned; (3) the FSU C5/6 with an additional 10-mm-deep incision of the anterior half of the anulus fibrosus and the disc; (4) the FSU C5/6 with additionally sectioned ligamenta flava as well as interspinous and supraspinous ligaments; (5) the FSU C5/6 with additional capsulotomy of the facet joints. In flexion/extension, significant differences were observed concerning range of motion (ROM) and neutral zone (NZ) for all four stages of instability compared to the intact FSU. In axial rotation, only the stage 4 instability showed a significantly increased ROM and NZ compared to the intact FSU. For lateral bending, no significant differences were observed. Based on these data, we conclude that flexion/extension is the most sensitive load-direction for the tested discoligamentous instabilities.
authors.affiliation: Department of Orthopaedics and SCI, University of Ulm, Germany. marcus.richter@medizin.uni-ulm.de
authors.forename: M
authors.initials: M
authors.lastname: Richter
authors.forename: H J
authors.initials: HJ
authors.lastname: Wilke
authors.forename: P
authors.initials: P
authors.lastname: Kluger
authors.forename: L
authors.initials: L
authors.lastname: Claes
authors.forename: W
authors.initials: W
authors.lastname: Puhl
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D002574:Cervical Vertebrae / Q000293:injuries* / Q000503:physiopathology; D006801:Humans; D007403:Intervertebral Disc / Q000293:injuries*; D007593:Joint Instability / Q000503:physiopathology*; D017846:Longitudinal Ligaments / Q000293:injuries*; D016059:Range of Motion, Articular / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology*