Biomechanical role of lumbar spine ligaments in flexion and extension using a parallel linkage robot: A porcine model

This research focuses on the porcine lumbar spine ligaments' normal mechanical function. The contribution of the posterior spinal ligaments, facet joints and supraspinous/interspinous ligament interaction to the resistance of flexion and extension was quantified in porcine lumbar spine specimens using a serial dissection procedure. Pure moment loading and maintaining the kinematics during subsequent tests, using a parallel linkage robotic testing system, allowed the principle of superposition to be applied. The supraspinous/interspinous ligament interaction's contribution to resisting flexion was as large as that of the interspinous ligament and almost as large as that of the supraspinous ligament and facets. The supraspinous/interspinous ligament complex resisted flexion prior to half of full flexion and was the largest contributor to the resistance of flexion motion. The only structures involved in resisting extension were the facet joints and the intervertebral disc, with the facets' contribution being three times greater than that of the intervertebral disc.