• Parham Rasoulinejad, Stewart D McLachlin, Stewart I Bailey, Kevin R Gurr, Christopher S Bailey, and Cynthia E Dunning.
• Division of Orthopaedics, Department of Surgery, Western University, 1151 Richmond St, London, Ontario N6A 5B9, Canada.
• Spine J. 2012 Jul 1; 12 (7): 590-5.

Background ContextUnilateral facet disruptions are relatively common in the cervical spine; however, the spectrum of injury is large, and little is known regarding the magnitude of instability expected to be present in an isolated posterior osteoligamentous injury.PurposeTo quantify the contribution of the posterior osteoligamentous structures to cervical spine stability during simulated flexion-extension (FE), lateral bend (LB), and axial rotation (AR).Study DesignAn in vitro biomechanical study.MethodsEight cadaveric C2-C5 spines were used in this study. A custom-developed spinal loading simulator applied independent FE, LB, and AR to the specimens at 3°/s up to ±1.5 Nm. Using an optical tracking system, data were collected for the intact specimen and after sequential surgical interventions of posterior ligamentous complex (PLC) disruption, unilateral capsular disruption, progressive resection of the inferior articular process of C3 by one-half, and finally complete resection of the inferior articular process of C3. The magnitude of segmental and overall range of motion (ROM) for each simulated movement along with the overall neutral zone (NZ) was analyzed using two-way repeated-measures analyses of variance and post hoc Student-Newman-Keuls tests (α=.05).ResultsAn increase in ROM was evident for all movements (p<.001). Within FE, ROM increased after cutting only the PLC (p<.05). For AR, sectioning of the PLC and complete bony facet fracture increased ROM (p<.05). Lateral bend ROM increased after facet capsular injury and complete articular facet removal (p<.05). There was an overall effect of injury pattern on the magnitude of the NZ for both FE (p<.001) and AR (p<.001) but not for LB (p=.6); however, the maximum increase in NZ generated was only 30%.ConclusionsThe PLC and facet complex are dominant stabilizers for FE and AR, respectively. The overall changes in both ROM and NZ were relatively small but consistent with an isolated posterior osteoligamentous complex injury of the Stage I flexion-distraction injury.Copyright © 2012 Elsevier Inc. All rights reserved.

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