Response of the Intervertebral Disk of the Rhesus Monkey to P-A Shear Stress

Abstract

The relative functions of spinal elements in resisting P-A shear stress are determined from measurements of force and displacement. The response of intact, enucleate and degenerate disks are presented, as well as stress-strain characteristics of the intervertebral disk and the roles of the articular facets and the nucleus pulposus.

Pure Shear Properties of Lumbar Spinal Joints and the Effect of Tissue Sectioning on Load Sharing

“…Although this study is limited by the use of a single value of loading that is relatively low in comparison to the quoted failure loads in shear, the choice of the single maximum load of 250 N for all specimens helped to avoid problems that might be encountered due to the relationship between load sharing and total applied load. 15 The importance of considering the deformation within the mounting arrangement has been emphasized by a earlier studies. 13,21 Therefore, all recorded displacement values were corrected against calibration data from a solid specimen to take the deformation of the mounting arrangement into account.…”

“…Recently, a few mechanical in vitro studies have been used to establish the relative contributions of the anterior column and the posterior elements to the shear properties of the intervertebral joint. 15,16 By comparing intact specimens against those without posterior ligaments and facet joints, they concluded that the disc complex accounted for approximately 85% of the average stiffness to failure and 74% of the ultimate load. The nucleus pulposus played an important part in the response to shear by comparing intact and enucleated specimens and indicated that the force in the disc at subfailure loading was generally some 40% of the total.…”

Computer Graphics Illustration of the Operation of the Intervertebral Disc

“…Shear has been studied experimentally Schultz et al, 1979;Lantz et al, 1980;Stokes and Medlicott, 1980) but was ignored by Hickey and Hukins (1980a). By 'shear' the authors mean translation of the cranial face of the disc with respect to the caudal face.…”

Structural Behavior of Human Lumbar Intervertebral Disc under Direct Shear

“…Most of the experimental work on the shear properties of the spine in vitro have focused on the coupled shear motion accompanying flexion—extension (6, 7). The function of the individual spinal structures with respect to shear was investigated by comparing intact specimens against those without posterior elements (8, 9). The authors concluded that the disc accounted for approximately 85% of the average stiffness to failure and 74% of the ultimate load.…”