title: The effect of facet geometry on the axial torque-rotation response of lumbar motion segments.
abstract: The objective of this study is to examine the effect of the facet geometry on the axial torque-rotation response of lumbar motion segments. The three-dimensional facet geometry of 35 L2-3 and 35 L4-5 specimens has been quantified in terms of seven parameters from computed tomographic transverse sections taken at 2-mm intervals. The motion segments have then been subjected to axial torque, for a variety of preload conditions, to establish the axial torque-rotation response. There exists significant variation of facet geometry between the segment levels; however, the degree of facet asymmetry is identical for each level. No significant correlation exists between the lumbar facet geometry and the axial torque-rotation response. The facet joints do, however, act as a "positive stop" to axial rotation, regardless of their orientation. Therefore, axial rotation sufficient to cause disc injury may only be possible after facet failure.
authors.affiliation: Department of Mechanical Engineering, McGill University, Montreal, PQ, Canada.
authors.forename: A M
authors.initials: AM
authors.lastname: Ahmed
authors.forename: N A
authors.initials: NA
authors.lastname: Duncan
authors.forename: D L
authors.initials: DL
authors.lastname: Burke
mesh_terms: D002102:Cadaver; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009068:Movement; D012399:Rotation; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed; D014102:Torsion Abnormality