Laboratory Studies
There are no laboratory studies that would assist in diagnosis of spinal instability. Laboratory studies can be helpful in diagnosing certain conditions that could result in spinal stability, such as spine infections (complete blood count [CBC], erythrocyte sedimentation rate [ESR], C-reactive protein [CRP], blood cultures), rheumatoid arthritis (rheumatoid factor [RF]), ankylosing spondylitis (HLA-B27), multiple myeloma (serum immunoelectrophoresis, urine Bence-Jones proteins), and others.
Laboratory studies are routinely performed as a part of preoperative preparation for spine surgery.
Imaging Studies
Magnetic resonance imaging (MRI) of the spine and plain radiography with flexion and extension are the most useful imaging studies for evaluation of spinal instability. In addition to demonstrating vertebral displacement, vertebral deformation and neural compression, MRI provides invaluable information about spinal cord injury, neoplastic and infectious processes, and ligamentous disruption.
Computed tomography (CT) myelography is used when MRI cannot be obtained or has not provided the resolution necessary to assess the extent of neural compression. Plain CT is useful for assessing bone anatomy in the setting of vertebral fractures, spondylolysis, previous spine surgery, and congenital spine anomalies. CT may also be used to assess certain bony parameters (eg, pedicle size in the thoracolumbar spine, lateral mass anatomy in the cervical spine, and vertebral artery anatomy in the atlantoaxial [C1-2] region) in preparation for instrumentation of the spine.
To evaluate bone integrity before fusion when osteoporosis is suspected, a bone density scan is performed. Radionuclide bone scans have been supplanted by high-resolution CT for assessment of pseudarthrosis.
Other Tests
Electromyography (EMG) may be used to confirm nerve-root compression but does not play a direct role in establishing the diagnosis of spinal instability.
Procedures
Selective nerve-root injections can be used as a diagnostic tool to confirm that a particular nerve root is responsible for the pain syndrome. They are also used in a therapeutic capacity in nonsurgical management of spine disorders.
CT-guided biopsy/aspiration is used when tumor or infection is suspected and when the possibility of nonsurgical treatment is being entertained. When surgery has to be performed to decompress or stabilize the spine, the diagnosis can be obtained intraoperatively.
Substantial controversy exists regarding the value of diskography in diagnosis of diskogenic pain and in patient selection for fusion surgery. When performed, it should be accompanied by measurements of intradiskal pressure, documentation of severity and concordance of pain during injection, and postdiskography CT.
Histologic Findings
No histologic findings are relevant to the diagnosis of spinal instability, except when a neoplasm is the source of instability.
Staging
Because spinal instability is a heterogeneous condition, no uniform staging or grading system exists that would be relevant to all forms of spinal instability.
Spondylolisthesis, defined as anterior translation of a vertebral body in relation to the adjacent caudal vertebral body, is graded according to the system in Table 1 below. (See the image below.)
Table 1. Grading of Spondylolisthesis (Open Table in a new window)
Slip Distance/Anteroposterior Diameter of Vertebral Body |
Grade |
0-25% |
1 |
25-50% |
2 |
50-75% |
3 |
75-100% |
4 |
>100% |
Spondyloptosis |
Grade 1 spondylolisthesis in neutral position progresses to grade 2 with flexion, indicating overt instability in this case.
In the lumbar spine, spondylolisthesis is either isthmic, degenerative, or traumatic. Isthmic spondylolisthesis occurs because of a congenital weakness and subsequent fracture of pars interarticularis (usually of L5; see the image below), resulting in uncoupling and glacial anterior translation of one vertebral body over another.
Degenerative spondylolisthesis occurs because of severe degeneration of facet joints and incompetence of facet capsules, which lose the capacity to resist the flexion moment, resulting in translation. Traumatic spondylolisthesis represents a fracture-dislocation of the spine.
-
Bilateral jumped facet syndrome is example of overt spinal instability due to trauma. Note grossly abnormal displacement of C5 relative to C6 with neck flexion.
-
Example of anticipated instability. (A) Large mass affecting right C3-4 facet joint and lateral masses in patient with severe right-side neck and shoulder pain; (B, C) complete resection of tumor and simultaneous C3-4 anterior fusion to circumvent anticipated iatrogenic stability produced by radical resection of facet and lateral masses.
-
Spinal stenosis with fixed degenerative spondylolisthesis in elderly patient is common example of covert instability. Acceptable surgical treatment options include decompression alone vs decompression with fusion.
-
(A) Compression fracture; (B) burst fracture; (C) hyperextension injury to lamina and facets; (D) flexion-distraction (seatbelt) ligamentous injury and Chance fracture; (E) shear fracture-dislocations.
-
Example of application of biomechanical principles to spine surgery. Insertion of special pedicle screws (Schanz screws) pivoting on rod transfers instantaneous axis of rotation (IAR) to screw-rod interface. Compression of proximal end of screws produces distraction-reduction of vertebral burst fracture. If posterior longitudinal ligament is intact, retropulsion is corrected by ligament taxis. Image courtesy of Synthes, Inc.
-
Comparison of vertebral anatomy in cervical, thoracic, and lumbar spine. Note variation in anatomy and size of pedicles.
-
Loosening of this infected pedicle screw is evidenced by radiolucent halo (arrows) surrounding screw.
-
In this patient with T7-8 diskitis, vertebral enhancement on MRI persisted 8 weeks after clinical and microbiologic cure.
-
Grade 1 spondylolisthesis in neutral position progresses to grade 2 with flexion, indicating overt instability in this case.
-
Grade I isthmic spondylolisthesis at L5-S1. Arrow depicts L5 pars fracture.
-
C1-2 fusion with cable fixation (Gallie technique). In this case, fusion is supplemented with transarticular screws.
-
C1-2 fusion and cable fixation (Brooks technique). Image courtesy of Synthes, Inc.
-
C1-2 fusion with cable fixation (Sonntag technique): coronal (left) and sagittal (right) CT reconstructions.
-
C1-2 transarticular screw. Note proximity of vertebral artery to typical screw trajectory.
-
Anterior cervical plate, applied in this case after two-level anterior cervical diskectomy and fusion. Image courtesy of Synthes, Inc.
-
Large central disk herniations (A, B) and cervical spondylotic myelopathy with kyphosis (C) are two common indications for anterior cervical diskectomy and fusion.
-
C5-6 bilateral jumped facets associated with disk herniation (left) was treated with C6 anterior cervical decompression and fusion (right).
-
Anterior cervical diskectomy and fusion. (A) Disk removed and interspace prepared to receive graft; (B) iliac crest bone graft harvested; (C) bone graft; (D) graft inserted into disk space; (E) plate screwed to anterior surface of vertebral bodies.
-
Intraoperative fluoroscopy for pedicle screw insertion.
-
Pedicle screw fixation of lumbar spine. Image courtesy of Synthes, Inc.
-
Combined interbody and posterolateral lumbar fusion with pedicle screws: coronal (left) and sagittal (right) CT reconstructions.
-
Anterolateral lumbar corpectomy followed by reconstruction with fixed-height cage and dynamic rod system that allows compression across cage. Image courtesy of Synthes, Inc.
-
Modular posterior thoracolumbar instrumentation system, which is attached to spine by combination of screws and hooks, in turn attached to long rods. In this case, it is used for correction of scoliosis, using three-point bending biomechanical principles. Image courtesy of Synthes, Inc.
-
Anterolateral thoracic corpectomy followed by reconstruction with expandable cage and fixed plate-screw system. Image courtesy of Synthes, Inc.
-
Anteroposterior and lateral radiographs of anterior thoracic corpectomy and reconstruction for pathologic fracture due to vertebral osteomyelitis.
-
Modern operating room setup for spine surgery with fluoroscopy unit, neurophysiologic monitoring equipment, operating microscope, and digital radiology monitors.
-
Transition level syndrome: C6-7 disc herniation developed 6 years after C4-5 and C5-6 anterior cervical diskectomy and fusion.
-
Artificial lumbar disk. Image courtesy of Synthes, Inc.
Tables
Slip Distance/Anteroposterior Diameter of Vertebral Body |
Grade |
0-25% |
1 |
25-50% |
2 |
50-75% |
3 |
75-100% |
4 |
>100% |
Spondyloptosis |
Fracture/Dislocation (Mechanism) |
Type/Issue |
Treatment |
C1 Jefferson fracture (axial loading) |
1. Isolated --> 2. With transverse ligament rupture --> 3. Widely diastatic --> 4. With odontoid fracture --> |
1. Hard collar 2. Halo 3. Consider occiput-C2 fusion 4. Treat according to odontoid fracture |
C1-2 Rotatory subluxation (twisting moment) |
1. Children, URI --> 2. Adults, tumor, trauma, infection --> |
1. Bedrest, analgesics, halter traction, soft collar 2. Traction, hard collar, halo, or C1-2 fusion depending on cause and duration |
Odontoid fracture (flexion in young, extension in old) |
1. Type 1 --> 2. Type 2, < 6 mm displaced --> 3. Type 2, >6 mm displaced or chronic or type 2A --> 4. Type 3 --> |
1. If no atlanto-occipital instability, collar × 3 mo 2. Halo × 3-6 mo 3. C1-2 fusion or odontoid screw 4. Halo × 6 mo |
C2 Hangman fracture (extension) |
1. Pars approximated-> 2. Pars separated, reducible --> 3. Pars separated, not reducible --> |
1. Hard collar × 3 mo 2. Reduce in extension, then halo × 3 mo 3. C2-3 fusion |
Unilateral jumped facet (flexion + rotation) |
1. Reducible --> 2. Not reducible --> 3. With facet fracture --> 4. With disk herniation --> |
1. Reduce and halo × 3 mo 2. Open reduction and posterior fusion 3. Open reduction and posterior fusion 4. Anterior decompression, open reduction, and anterior fusion |
Bilateral jumped facet (flexion) |
1. Reducible, without disk herniation --> 2. Not reducible, without disk herniation --> 3. With disk herniation --> |
1. Closed reduction, then posterior fusion 2. Open anterior or posterior reduction and fusion 3. Anterior diskectomy, reduction and fusion |
Subaxial spine axial loading injuries (axial ± flexion) |
1. Simple compression fracture --> 2. Burst fracture ± teardrop fracture --> 3. Burst + posterior column fracture --> |
1. Hard collar 2. Anterior corpectomy and fusion 3. Anterior corpectomy and fusion (± posterior fusion) |
Clay shoveler fracture (flexion) |
Always stable |
Soft collar and analgesics |
Anterior avulsion fracture (extension) |
Always stable |
Soft collar and analgesics |
Fracture |
Denis Columns Involved |
Treatment |
Compression fracture |
Anterior column |
Bracing (note that >50% vertebral body height loss or Cobb angle >30º predicts worsening of kyphosis) |
Compression fracture with splaying of spinous processes |
Anterior and posterior columns |
Posterior instrumented fusion |
Stable burst fracture (preserved posterior longitudinal ligament) |
Anterior column and part of middle column |
If no neural compromise, treat with TLSO brace If canal stenosis present, retropulsed fragment may be reduced by ligamentous taxis in distraction with posterior instrumented fusion |
Unstable burst fracture |
Anterior and middle columns with significant retropulsion, or all three columns |
Anterior decompression and instrumented fusion |
Flexion-distraction seat belt injury (ligamentous) |
Middle and posterior columns |
Posterior reduction and instrumented fusion |
Chance fracture (osseous) |
Two or three columns but with good bone contact |
TLSO brace |
Shear fracture dislocation |
Three columns |
Instrumented fusion, anterior, posterior, or both |
Type |
Fracture Anatomy |
1 |
Fracture through odontoid tip (rare) |
2 |
Fracture across base of odontoid process (most common) |
2A |
As in type 2, except with comminution of fracture line, reducing possibility of healing of fracture in halo or with odontoid screw |
3 |
Fracture extension into C2 vertebral body; because of larger bone contact area, fracture usually heals well in halo |
What would you like to print?
- Overview
- Presentation
- Workup
- Treatment
- Approach Considerations
- Nonoperative Therapy
- General Surgical Considerations
- Surgical Therapy for Atlantoaxial (C1-2) Instability
- Surgical Therapy for Subaxial Cervical Instability
- Surgical Therapy for Thoracic and Thoracolumbar Instability
- Surgical Therapy for Lumbar Spinal Instability
- Postoperative Care
- Complications
- Long-Term Monitoring
- Show All
- Media Gallery
- Tables
- References
