title: Failure of the human lumbar motion-segments resulting from anterior shear fatigue loading.
abstract: An in-vitro experiment was designed to investigate the mode of failure following shear fatigue loading of lumbar motion-segments. Human male lumbar motion-segments (age 32-42 years, n=6) were immersed in Ringer solution at 37°C and repeatedly loaded, using a modified materials testing machine. Fatigue loading consisted of a sinusoidal shear load from 0 N to 1,500 N (750 N±750 N) applied to the upper vertebra of the motion-segment, at a frequency of 5 Hz. During fatigue experiments, several failure events were observed in the dynamic creep curves. Post-test x-ray, CT and dissection revealed that all specimens had delamination of the intervertebral disc. Anterior shear fatigue predominantly resulted in fracture of the apophyseal processes of the upper vertebrae (n=4). Exposure to the anterior shear fatigue loading caused motion-segment instability and resulted in vertebral slip corresponding to grade I and 'mild' grade II spondylolisthesis, as observed clinically.
authors.affiliation: Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, U.K.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Skrzypiec
authors.forename: Katrin
authors.initials: K
authors.lastname: Nagel
authors.forename: Kay
authors.initials: K
authors.lastname: Sellenschloh
authors.forename: Anke
authors.initials: A
authors.lastname: Klein
authors.forename: Klaus
authors.initials: K
authors.lastname: Püschel
authors.forename: Michael M
authors.initials: MM
authors.lastname: Morlock
authors.forename: Gerd
authors.initials: G
authors.lastname: Huber
mesh_terms: D000328:Adult; D015775:Fractures, Stress / Q000473:pathology; D006801:Humans; D066298:In Vitro Techniques; D007403:Intervertebral Disc / Q000293:injuries / Q000473:pathology; D008159:Lumbar Vertebrae / Q000293:injuries* / Q000473:pathology; D008297:Male; D033081:Shear Strength; D013168:Spondylolisthesis / Q000473:pathology; D013314:Stress, Mechanical; D014732:Vibration / Q000009:adverse effects*
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