Locked facet injuries

This is usually the result of a severe flexion injury which can result in disrupting the normal relationship between the facets. The inferior facet of the level above is usually posterior to the superior facet of the level below. Facets that are just before the point of locking are known as perched facets.

Flexion and rotational injury will result in a unilateral locked facet while an extreme hyperflexion force will result in a bilateral locked facet. Bilateral locked facets usually present with cervical spinal cord injury and injury to the cervical roots.

Diagnosis is usually made on the lateral cervical spine and AP radiographs. Both unilateral and bilateral locked facets will often produce subluxation. Horizontal subluxation of greater than 3.5 mm of

m Is this injury associated with spinal cord damage?

Fig. 4.52 Quiz case.

Fig. 4.53 Locked facets. AP cervical spine.There is malalignment of the spinous processes (arrows) at the C5-C6 level corresponding to the level of locked facets (Fig. 4.52). Incidental nodular densities and smooth pleural thickening at the left lung apex are calcified granulomas and pleural reaction related to previously healed TB.

Fig. 4.53 Locked facets. AP cervical spine.There is malalignment of the spinous processes (arrows) at the C5-C6 level corresponding to the level of locked facets (Fig. 4.52). Incidental nodular densities and smooth pleural thickening at the left lung apex are calcified granulomas and pleural reaction related to previously healed TB.

one vertebral body on another or greater than 11 degrees of angulation of one vertebral body relative to the next indicates ligamentous instability.

In unilateral facet dislocation, the AP view of the spinous process above the subluxation rotate to the same side as the locked facet (see Fig. 4.53). On the lateral cervical-spine radiograph, 'bow-tie' or 'bat-wing' appearances of the locked facets is seen referring to visualisation of the left and right facets at the level of the injury instead of the usual normal superimposition of the facet joints.

Subluxation may be seen in unilateral locked facets. However, it is almost always seen in bilateral locked facets with usually greater than 25% of the vertebral body being subluxed anterior relative to the vertebral body below. Disruption of the posterior ligamentous complex may produce widening of the interspinous distance and there may also be a widening of the disc space. Oblique films may help better demonstrate the locked facets which usually will be seen blocking the neuroforamina. MRI may be utilised to assess integrity of the disc space and exclude an extruded disc that could be impinging on the spinal cord [2, 5, 6].

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Essentials of Human Physiology

Essentials of Human Physiology

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