M. Richter, H-J. Wilke, P. Kluger, L. Claes, W. Puhl

April 2000, Volume 9, Issue 2, pp 104 - 108 Original article Read Full Article 10.1007/s005860050219

First Online: 25 April 2000

The objective of this study was to determine which discoligamentous structures of the lower cervical spine provide significant stability with regard to different loading conditions. Accordingly, the load-displacement properties of the normal and injured lower cervical spine were tested in vitro. Four artificially created stages of increasing discoligamentous instability of the segment C5/6 were compared to the normal C5/6 segment. Six fresh human cadaver spine segments C4-C7 were tested in flexion/extension, axial rotation, and lateral bending using pure moments of ± 2.5 Nm without axial preload. Five conditions were investigated consecutively: (1) the intact functional spinal unit (FSU) C5/6; (2) the FSU C5/6 with the anterior longitudinal ligament and the intertransverse ligaments sectioned; (3) the FSU C5/6 with an additional 10-mm-deep incision of the anterior half of the anulus fibrosus and the disc; (4) the FSU C5/6 with additionally sectioned ligamenta flava as well as interspinous and supraspinous ligaments; (5) the FSU C5/6 with additional capsulotomy of the facet joints. In flexion/extension, significant differences were observed concerning range of motion (ROM) and neutral zone (NZ) for all four stages of instability compared to the intact FSU. In axial rotation, only the stage 4 instability showed a significantly increased ROM and NZ compared to the intact FSU. For lateral bending, no significant differences were observed. Based on these data, we conclude that flexion/extension is the most sensitive load-direction for the tested discoligamentous instabilities.

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