THE POSTERIOR LIGAMENT COMPLEX IN CERVICAL SPINE TRAUMA

Abstract

The posterior ligament complex (PLC) in the cervical spine comprises the posterior longitudinal ligament, ligamentum flavum and ligamentum nuchae, the latter homologous with the supraspinous and interspinous ligaments at other levels of the spine. In determining instability, evaluation of the PLC is an essential part of the assessment of cervical spine injuries. Disruption of the PLC occurs following flexion injuries, both in compression and in distraction, and following extension injuries with compression. PLC disruption, diagnosed when clinical examination reveals localised posterior spinal tenderness and/or a widened interspinous gap, is confirmed on standard and dynamic flexion-extension radiographs and MRI.

This paper is a retrospective review of 162 patients treated for cervical injuries between 1997 and 2001. There were 83 (51%) distraction flexion, 37 (23%) compression flexion, 18 (11%) compression extension, 17 (10%) vertical compression, six (4%) distraction extension and one (1%) lateral flexion injuries. In 79 patients with pure ligamentous instability, an interspinous stabilisation procedure was performed, using a titanium cable. When associated fractures occurred with PLC disruption, neurologically intact patients were managed conservatively with traction followed by a spinal brace. Patients with a neurological deficit underwent surgery. Using delayed dynamic flexion-extension views and MRI, PLC disruption was diagnosed late in nine flexion distraction injuries without facet dislocation. At follow-up, flexion-extension views showed that all PLC disruptions with associated fractures had stabilised. There were two broken cables in patients who underwent surgery.

Patients with cervical instability following trauma may be treated non-operatively when there are associated fractures, while patients with pure ligamentous instability should undergo fusion. Further, to exclude occult PLC disruption, all cervical injuries should be reviewed on flexion-extension views once the paraspinal muscle spasm has settled.