title: Experimental measurement of ligament force, facet force, and segment motion in the human lumbar spine.
abstract: Facet forces, longitudinal ligament loads, and vertebral body motion were experimentally measured in five fresh human lumbar spine segments, L1-L2. Strain gages on the bone surface were used to quantify facet loads. Buckle transducers were used to measure anterior and posterior longitudinal ligament loads. The three-dimensional motion of the motion segment was measured with an instrumented spatial linkage. The facets were found to carry no load in flexion, large loads during extension (205 N at a 10 Nm moment and a 190 N axial load), torsion (65 N at a 10 Nm moment and a 150 N axial load), and lateral bending (78 N at a 3 Nm moment and a 160 N axial load). The facet contact site on the inferior articular process of L1 was found to move inferiorly to a position of tip impingement near the lamina as extension moments increased. Impingement occurred in the range of 4-6 Nm extension. The posterior and anterior longitudinal ligaments were predominantly loaded in flexion and extension, respectively. No ligament loads occurred in lateral bending and torsion. A 1 cm strip of the anterior longitudinal ligament carried loads up to 130 N at the largest extension moment of 11.4 Nm. The posterior longitudinal ligament had a 60 N load at the largest flexion moment of 7.1 Nm. There was no pre-load in the ligament detectable with the buckle transducers (> 4 N). The facets and ligaments began carrying load immediately with applied load, without a lax region. The experimental technique developed and used provides a good tool for obtaining simultaneous facet joint loads, ligament loads, and vertebral body motion without altering the motion segment.
authors: Department of Orthopaedic Surgery University of Minnesota, Minneapolis 55455.
authors: M J
authors: MJ
authors: Schendel
authors: K B
authors: KB
authors: Wood
authors: G R
authors: GR
authors: Buttermann
authors: J L
authors: JL
authors: Lewis
authors: J W
authors: JW
authors: Ogilvie
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002138:Calibration; D005260:Female; D006801:Humans; D008022:Ligaments / Q000033:anatomy & histology / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009068:Movement; D012399:Rotation; D012815:Signal Processing, Computer-Assisted; D013314:Stress, Mechanical; D014159:Transducers