- See:
-
Facet Joint Injuries
-
Hyperflexion Injuries
-
Oblique projections;
-
Pillar View
- Discussion:
- simple unilateral facet dislocation is often a stable injury, eventhough there is disruption of the
posterior ligament complex (involved joint capsule, posterior longitudinal ligament, and annulus);
- mechanism & anatomy of injury:
- injury involves forward rotation of one side of vertebra about contra-lateral
facet joint;
- simultaneous flexion-rotation injury produces unilateral interfacetal dislocation;
- interfacetal joint on side of direction of rotation is pivot:
- superior facet on contralateral side rides upward, forward,& over tip of inferior facet
of involved joint, coming to rest in intervertebral foramen anterior to inferior facet of joint;
- in this position, the intervertebral forament is "locked;"
- central portion of vertebral body subluxates about 25% of AP body diameter;
-
associated injuries:
-
inferior facet of dislocated joint is frequently treated;
- capsule of non dislocated joint is frequently disrupted;
- facet dislocations can also occur w/ concomitant frx of either facet or the entire lateral mass;
- partial tearing of posterior longitudinal ligament on affected side(s);
- anterior longitudinal ligament remains intact;
- Clinical Manifestation:
-
physical exam of the cervical spine:
- delays in diagnosis are not rare (40% of patients in one study).
- pts may have
torticollis:
- axial rotation to contralat side & lateral bend to injured side.
- Radiographs:
-
AP View:
- involved spinous process points to involved side;
-
lateral view:
- mild anterior subluxation of vertebral body above &soft-tissue swelling anteriorly;
- vertebral body is anteriorly displaced ( < 50% AP diameter)
- decrease overlap of articular processes relative to
facet joint above;
- two lateral masses of dislocated vertebra will overlap only
partially on
lateral view producing"bow tie" sign;
-
oblique view:
- anteriorly dislocated inferior articular process is forced down into lower 1/2 of
neuroforamen, causing nerve root compression;
- may readily be seen on the trauma
oblique radiograph.
-
dynamic lateral radiographs:
- (physician supervised) may determine if there is hypermobility;
- tomography:
- is useful to determine presence of a frx & extent of displacement;
- MRI:
- disk herniation can be identified either by MRI or by
myelography;
- anterior diskectomy and interbody fusion may be necessary if significant disk extrusion is present;
- failure to recognize a significant disk extrusion, which more commonly occurs with
bilateral
facet dislocation, can result in a catastrophic neurologic deficit;
- Reduction:
- Non Operative Treatment:
-
management of the spine injured patient:
- minimal subluxation is treated w/ Philadelphia-type collar for 6 wks;
- need careful f/u to ensure progressive subluxation does not occur;
- w/o disk widening or subluxation, unilateral facet dislocation is stable injury;
- if there is
< 3.5 mm of translation assoc w/ this frx-dislocation,
spine can undergo attempted reduction &
halo immobilization;
- first try skeletal traction, followed by open reduction if unsuccessful.
- use of closed reduction by manipulation under GEA should be used only w/ flouroscopy:
- successful closed reduction is followed either by halovest (for 3 month), or by posterior wiring & bone grafting.
- closed reduction w/ halo traction is successful in 50 % of pts;
- these may be treated with
halo vest immobilization;
- Indications for Surgery:
- failed closed reduction:
- if flexion extension views demonstrate persistent instability after 12 weeks, posterior stabilization is indicated;
-
middle column injury
- this injury frequently leads to late instability;
- early single level posterior fusion is therefore recommended;
-
signs of middle column disruption
- unilateral facet dislocation accompanied by > 25% subluxation;
- greater than 1.7 mm of disk widening;
- if initial displacement is > 3.5 mm;
- angulation > 11 deg (more than adjacent segments)
- Posterior Approach:
- open reduction is generally performed posteriorly, which allows direct visualization of the articular processes;
- posterior wiring w/ ICBG is performed for progressive subluxation;
- internal fixation must neutralize rotational forces;
- facet wiring & lateral mass plating may be used;
- w/ articular process frx or floating lateral mass bony block then resisting anterior shift on
affected side may be lost, & additional fixation is needed;
- Anterior Approach:
- provides a limited view & further disrupts disk;
- allows complete removal of disk, which eliminates risk of inducing paralysis from disk extrusion during reduction;
- Case Example:
Closed reduction of cervical spine dislocations.
Unilateral facet dislocations and fracture-dislocations of the cervical spine.
Neurological deterioration after reduction of cervical subluxation. Mechanical compression by disc tissue.
Unilateral facet dislocations and fracture-dislocations of the cervical spine.
Anterior decompression and arthrodesis of the cervical spine: long-term
motor improvement. Part I--Improvement in incomplete traumatic quadriparesis.
Anterior decompression and arthrodesis of the cervical spine: long-term motor improvement. Part II--Improvement in complete traumatic quadriplegia.
Unilateral facet dislocation of the cervical spine. An analysis of the x results of treatment in 26 patients.
