Although qualitative descriptions of degenerative changes in the intervertebral disc components have been reported, methods to quantify these changes are lacking. A methodology was developed in this study to quantify the three-dimensional geometrical variations of the annulus fibrosus and nucleus pulposus. Fresh isolated intervertebral discs with adjacent vertebral bodies of skeletally mature young and old adult primates were sectioned sequentially, and different staining methods were used to distinguish the annulus and nucleus. Histological images were examined using light microscopy and exported to a computer to trace the boundaries of the annulus fibrosus and nucleus pulposus. Dorsal to ventral depth, medial to lateral width, and caudal to cranial height measurements of the nucleus pulposus and its relative location to the annulus pulposus were obtained. In the young adult, the nucleus was translucent with scattered notochordal cells. In the older adult, the nucleus appeared as a dense region of amorphous, irregular collagen material. A higher geometrical variation of nucleus due to degeneration was noted in the sagittal plane compared to coronal plane. Determination of the three-dimensional geometrical variations and histology analyses will assist mathematical modelers to better define the disc to study the biomechanics of the cervical spine.

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