Spondylolisthesis Imaging

Practice Essentials

The word spondylolisthesis is derived from the Greek words spondylo, meaning spine, and listhesis, meaning to slip or slide. Spondylolisthesis is a descriptive term referring to slippage (usually forward) of a vertebra and the spine above it relative to the vertebra below it.

Spondylolisthesis has many etiologies, all of which ultimately lead to a loss of the stability offered by the locking mechanism of the articular processes of the vertebrae that allow the superior vertebrae to slide forward over the inferior vertebrae. The etiologies can be classified as congenital (dysplastic), spondylolytic (isthmic), degenerative, traumatic, pathologic, or iatrogenic (eg, postoperative).

The spondylolytic type is the most common form of spondylolisthesis.^[1] It affects the region of the pars interarticularis, which is roughly the region of the junction of the pedicle and lamina, where the articular and transverse processes of the vertebrae arise.

A defect at this point functionally separates the vertebral body, pedicle, and superior articular process from the inferior articular process and the remainder of the vertebrae. Thus, the defect cleaves the vertebra into 2 parts. The portion of the vertebra posterior to the defect remains fixed, and the anterior portions are free to potentially slip forward relative to the posterior structures and spine below. Note that a bilateral pars defect is needed to allow slippage.

​Preferred examination

Flexion-extension functional radiographs are considered the gold standard for diagnosis of degenerative spondylolisthesis, and a disc angle change >10° or change in translation >3 mm are generally used as cut-offs.^[2]  

Lateral and anteroposterior plain radiographs of the lumbar spine should be obtained in patients with complaints of back pain. The lateral view (seen in the image below) is useful in detecting spondylolisthesis; it may demonstrate the pars defect.

View Image

Spondylolisthesis. Straight lateral radiograph of the L4-S1 level of the spine shows a lucency at the pars area (arrow). Bilateral pars defects must b....

Bilateral oblique views are especially useful in visualizing the pars interarticularis defect, which has the appearance of a Scottie dog with a collar. An elongated pars also may be seen. (See the images below.)

View Image

Spondylolisthesis. Oblique projection radiograph shows the presence of bilateral pars defects (arrows), with an appearance resembling a Scottie dog wi....

View Image

Spondylolisthesis. Diagram in the oblique projection shows the components of the vertebrae that result in the appearance of a Scottie dog with a colla....

In addition, plain radiographs also may demonstrate congenital types of spondylolisthesis and the changes of spondylosis. In the setting of trauma, fractures may be apparent. Note that other causes of the patient's symptoms may be demonstrated, such as an osteoid osteoma, Paget disease, and osteolytic lesions. The grade of spondylolisthesis can be measured by using the lateral view (as seen in the images below).

View Image

Spondylolisthesis. Lateral lumbar spinal radiograph in a pediatric patient shows spondylolysis with grade 1 spondylolisthesis.

View Image

Spondylolisthesis. Grade 4 traumatic spondylolisthesis.

Cross-sectional imaging should be considered next.

In patients with back pain and no clinical findings of nerve root involvement, computed tomography (CT) scanning of the lumbar spine yields information regarding spondylolisthesis and its cause, along with other possible conditions, such as disk disease, disk herniations, spondylosis, and spinal canal stenosis. Other associations, such as spina bifida, may be seen. In patients with radiculopathy, CT myelography can yield information regarding nerve-root impingement and its etiology, such as disk herniation, abscess, or neoplasm. CT scanning is more sensitive for detecting spondylolysis, but occasionally this can be missed, since scanning occurs in the plane of the spondylolysis or from volume averaging. Sagittal reconstruction images are of help in patients with these findings.

Magnetic resonance imaging (MRI) has the distinct advantage of being able to image the spine in any plane without exposure to radiation. Typically, the axial and sagittal planes are used, but images in the coronal plane can also be acquired easily, if needed. MRI reveals spondylolisthesis on sagittal views. Spondylolysis may not be readily apparent on MRIs, especially if there is a mild degree of bony sclerosis. Other sclerotic lesions in the pars interarticularis, such as osteoblastic metastases, may give similar appearances.^{[3, 4, 5, 6]}

Traumatic cervical spine fractures and dislocations are common in clinical practice, but high-grade traumatic cervical spondylolisthesis is rare. Total spondylolisthesis, or dislocation of one cervical vertebra, can only occur with high-energy traumas such as motor vehicle collisions, diving accidents, or severe falls.  A detailed 3D reconstructive CT should be performed to evaluate the fracture, subluxations, and dislocations. MRI can be performed to analyze the spinal cord and ligamentous injuries, and CT angiography can be performed to demonstrate a vascular injury.^[7]

A grading system of spondylolisthesis is shown in the image below.

View Image

Spondylolisthesis. Diagram shows how to grade spondylolisthesis. The 2 arrows, one indicating vertebral body width and the other indicating the amount....

• References

Radiography

In patients with complaints of back pain, anteroposterior and lateral projection plain radiographs of the lumbar spine should be obtained, at the least.^{[8, 9, 6]}

The lateral view is especially useful in detecting spondylolisthesis. Moreover, the grade of spondylolisthesis is measured on the lateral view (as seen in the images below). The pars defect may or may not be visualized on the lateral view.

View Image

Spondylolisthesis. Lateral lumbar spinal radiograph in a pediatric patient shows spondylolysis with grade 1 spondylolisthesis.

View Image

Spondylolisthesis. Grade 4 traumatic spondylolisthesis.

Bilateral oblique views may be obtained to visualize the pars defect, which has the appearance of a Scottie dog with a collar (as demonstrated in the radiographs below). An elongated pars also may be seen. Note that oblique views increase the specificity, but not the sensitivity, for pars defects.^[10]

View Image

Spondylolisthesis. Oblique projection radiograph shows the presence of bilateral pars defects (arrows), with an appearance resembling a Scottie dog wi....

View Image

Spondylolisthesis. Diagram in the oblique projection shows the components of the vertebrae that result in the appearance of a Scottie dog with a colla....

Congenital and degenerative types of spondylolisthesis also can be visualized on plain radiographs. Lumbar degenerative spondylolisthesis most commonly occurs at the L4–L5 level, followed in frequency by the L3–L4, L5–S1, and L2–L3 levels. The slip occurs secondary to the degenerative changes of the facet joints. A grade 1 slip is most common followed by a grade 2 slip. The width of the lumbar canal can be directly measured on these films from the mid aspect of the vertebral body in front (anteriorly) to the dorsal (back) interlaminar line (line created by the lamina coming together to form the spinous process). The normal canal width should be 20 mm. Smaller widths are considered spinal stenosis.^[11]

In the setting of trauma, fractures may be apparent. Traumatic spondylolisthesis of the axis, also known as a hangman’s fracture, is caused by hyperextension of the neck. These fractures are classified according to the degree of anteroposterior deviation, presence of disruption of the posterior longitudinal ligament, position of the fracture line, and presence of a facet-joint dislocation.^[12]

Other causes of the patient's symptoms may be seen; these include an osteoid osteoma, Paget disease, and osteolytic lesions.

Degree of confidence

Five-view plain radiography of the spine is the standard for a plain radiographic evaluation.

Visualization of spondylolisthesis on standard radiographs, particularly lateral plain radiographs, confirms the presence of the condition. The etiology may not be readily evident, and other modalities may be needed for elucidation. CT scanning is perhaps the most valuable cross-sectional modality for this.

False positives/negatives

In the setting of trauma in a child, a pseudosubluxation of the vertebra in the cervical spine may be demonstrated; such a finding may cause some confusion with traumatic spondylolisthesis. Clinical correlation may be helpful, since focal tenderness at that level may require further evaluation clinically and/or radiologically; CT scanning may be needed.

No normal variants have been identified that mimic spondylolysis or degenerative changes.

• References

Computed Tomography

In patients with back pain and no clinical findings of nerve root involvement, computed tomography (CT) scanning of the lumbar spine yields information regarding spondylolisthesis and its cause, along with other possible conditions, such as disk disease, disk herniations, spondylosis, and spinal canal stenosis. Other associations, such as spina bifida, may be seen. In patients with radiculopathy, CT myelography can yield information regarding nerve-root impingement and its etiology, such as disk herniation, abscess, or neoplasm.

CT scanning of the spine can be performed with or without intrathecal contrast enhancement. Axial images are obtained in a plane parallel to the disk spaces at each level imaged. Sagittal reconstruction images (seen below) are obtained by using post-acquisition processing software. Bone window (eg, 1500/300 HU) and soft-tissue window (eg, 300/30 HU) settings are used.

View Image

Spondylolisthesis. Sagittal CT reconstruction image shows the pars defect along with grade 1 spondylolisthesis (arrow).

View Image

Spondylolisthesis. Sagittal CT reconstruction image shows the pars defect along with grade 1 spondylolisthesis.

View Image

Spondylolisthesis. Sagittal CT reconstruction image shows the pars defect along with grade 1 spondylolisthesis (arrow).

Thin sections should be used to avoid problems, such as volume averaging. (Contiguous images also reduce such problems.) Indeed, if the sections are too thick and if a gap is present between sections, spondylolysis can be missed. In such cases, sagittal reconstructions may be of help in showing spondylolysis.

With spondylolysis, CT is performed as close as possible to an angle that is 90° to the level of interest. CT scans typically demonstrate a horizontally oriented defect in the pars, which interrupts the normally complete bony ring of the posterior elements.

Spondylolisthesis is evaluated best on lateral topogram, but it can be suggested in patients with spinal stenosis in the absence of disk pathology, posterior hypertrophic changes, or a congenitally narrow spinal canal. One typically looks for an elongated spinal canal (as seen in the images below).

View Image

Spondylolisthesis. Axial CT image shows bilateral spondylolysis (arrows). Note elongation of the spinal canal at this level.

View Image

Spondylolisthesis. Axial CT image shows bilateral spondylolysis (arrows). Note elongation of the spinal canal at this level.

CT scans can also demonstrate findings of congenital/dysplastic and degenerative types of spondylolisthesis. Abnormalities of the vertebral body or articular processes may be present.

Changes of spondylosis deformans (degenerative changes) are apparent on CT scans. Degenerative disease of the spine has a characteristic appearance involving a loss of disk space height with or without the presence of vacuum phenomenon, narrowing of the facet joint space, subchondral sclerosis, osteophyte formation, and subchondral cysts. Some or all of the changes may be present and cause altered alignment of the facet-joint articular surface, leading to slippage. Spinal canal and/or intervertebral neural foraminal stenosis may be present.

In traumatic spondylolisthesis, findings may include jumped facets and fractures of the articular processes and/or lamina that result in spondylolisthesis.

Degree of confidence

Usually, CT findings confirm the presence of spondylolisthesis, its etiologies, and potential complications. MRI provides complementary imaging in some patients with traumatic spondylolisthesis in whom information regarding ligamentous and spinal cord integrity is required. One of the limitations of CT scanning is that it does not demonstrate ligamentous injury well.

• References

Magnetic Resonance Imaging

MRI has the distinct advantage of imaging the spine in any plane. Typically, the axial and sagittal planes are used, but images in the coronal plane can also be acquired easily, if needed.^{[3, 4, 13, 14, 15]}

Spin-echo and fast spin-echo sequences are applied for image acquisition in these planes. A fat-saturation technique can be applied to minimize signal from fat and to bring out signal from fluid structures (eg, bone edema). Gradient-echo sequences can also be used; they have the advantage of faster image acquisition, limiting problems related to motion. In a postoperative patient, consideration should be given to gadolinium enhancement with T1-weighted spin-echo sequences.

Spondylolisthesis is confirmed by visualization on MRI. Spondylolysis may be difficult to appreciate, and plain radiographs and/or CT scans may be complementary in this regard.

Gadolinium-based contrast agents have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Systemic Fibrosis. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see Medscape.

MRIs should be scrutinized for the presence of a spondylolisthesis and for any abnormality of the pars interarticularis, pedicles, or facet joints. Nerve structures, including those exiting neural foramina, and the spinal canal should be evaluated.

A spondylolisthesis is best assessed on median sagittal images of the spine. The levels involved and the grade can be seen.

A spondylolysis pathologically can be a fibrous bridge or a pseudarthrosis, both of which have corticated/sclerotic margins in the adjacent portions of the bony ring. The bony sclerosis and fibrous tissue appear as an area of low signal intensity in the region of the pars interarticularis on images obtained with all sequences. This finding may not be easily seen and is a limitation of using MRI for spondylolysis.

Similar signal-intensity changes in these areas may be seen with bony sclerosis, volume averaging with adjacent osteoarthritic facet joints, osteoblastic metastases, and even involvement of the pedicles with Paget disease. Even if one sees normal bone signal extending from the vertebral body to the pedicle into the lamina, it is not possible to exclude a spondylolysis because there may be minimal sclerosis in the bone and because its signal intensity is similar to that of posterior element bone. This is a limitation of MRI in detecting spondylolysis.

High signal intensity may be seen in the pars interarticularis with T2-weighted sequences. This finding indicates the presence of fluid, a pseudarthrosis, or bone edema from infection.

Degenerative disease can also be seen.^{[16, 17]} Narrowed disk space, with disk desiccation (low T2 signal intensity), should be sought. This disk narrowing causes superoinferior subluxation at the facet joint at the level of disease, resulting in anterolisthesis or retrolisthesis. Reactive marrow changes should also be sought; these are seen in portions of vertebral body adjacent to disks and also in marrow adjacent to facet joints and may result in abnormal signal intensity in the pars interarticularis.

Neoplastic disease involving the pars interarticularis or other parts of the vertebra typically yields low marrow signal intensity with all sequences. Infection may be evident as fluid signal intensity (bright on T2-weighted MRIs) from bone edema. Both disease processes show enhancement with a gadolinium-based contrast agent. Other diseases causing a sclerotic response (eg, Paget disease) result in low signal intensity with all sequences.

• References

Nuclear Imaging

Nuclear medicine has no role as a primary imaging modality in spondylolisthesis. Spondylolysis can be detected as areas of increased activity on bone scans, but the appearance is nonspecific, and such findings may be seen in other disorders (eg, neoplasms and infections). Usually, correlation with clinical and plain radiographic findings is helpful in narrowing the differential diagnosis.

Nuclear medicine imaging involves the use of diphosphonates labeled with technetium-99m (^99mTc). This is administered intravenously, and planar images of the whole body are acquired (as seen in the image below).

View Image

Spondylolisthesis. Planar image of lumbar spine in a 14-year-old with back pain. Note hot spots at L5 in the region, where one would see the pedicles ....

High count (1000 k) spot views of the lumbar spine are also obtained. Single-photon emission CT (SPECT) scanning, used to produce the images below, is a more powerful way to detect areas of increased activity that may not be readily apparent on planar images.

View Image

Spondylolisthesis. Axial single-photon emission CT (SPECT) image shows bilateral hot spots in the pars; these indicate spondylolysis.

View Image

Spondylolisthesis. Coronal single-photon emission CT (SPECT) image shows bilateral hot spots in the pars; these indicate active spondylolysis.

View Image

Spondylolisthesis. Sagittal single-photon emission CT (SPECT) image shows hot spots in the pars; these indicate active spondylolysis.

View Image

Spondylolisthesis. Sagittal single-photon emission CT (SPECT) image shows hot spots in the pars; these indicate active spondylolysis.

View Image

Spondylolisthesis. Sagittal single-photon emission CT (SPECT) image shows hot spots in the pars; these indicate active spondylolysis.

View Image

Spondylolisthesis. Sagittal single-photon emission CT (SPECT) image shows hot spots in the pars; these indicate active spondylolysis.

• References

Author

Zubin Irani, MD, MBBS, Clinical Staff, Department of Radiology, Dotter Interventional Institute, Oregon Health and Science University School of MedicineClinical Staff, Vascular Interventional Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA

Disclosure: Nothing to disclose.

Coauthor(s)

Jehangir J Patel, MD, Director, Musculoskeletal Radiology Service, Department of Radiology, Baystate Medical Center

Disclosure: Nothing to disclose.

Specialty Editors

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand

Disclosure: Nothing to disclose.

William R Reinus, MD, MBA, FACR, Professor of Radiology, Temple University School of Medicine; Chief of Musculoskeletal and Trauma Radiology, Vice Chair, Department of Radiology, Temple University Hospital

Disclosure: Nothing to disclose.

Chief Editor

Felix S Chew, MD, MBA, MEd, Professor, Department of Radiology, Vice Chairman for Academic Innovation, Section Head of Musculoskeletal Radiology, University of Washington School of Medicine

Disclosure: Nothing to disclose.

Additional Contributors

David S Levey, MD, Musculoskeletal and Neurospinal Forensic Radiologist; President, David S Levey, MD, PA, San Antonio, Texas

Disclosure: Nothing to disclose.

References

1. Canale S. Campbell's Operative Orthopedics. Vol 3. 9th ed. St Louis: Mosby-Year Book. 1998.
2. Petersen T, Laslett M, Juhl C. Clinical classification in low back pain: best-evidence diagnostic rules based on systematic reviews. BMC Musculoskelet Disord. 2017 May 12. 18 (1):188. [View Abstract]
3. Daghighi MH, Poureisa M, Arablou F, Fouladi DF. Supine spinal magnetic resonance imaging with straightened lower extremities in spondylolisthesis: a comparison with the conventional technique. Eur J Radiol. 2015 May. 84 (5):921-6. [View Abstract]
4. Kanno H, Ozawa H, Koizumi Y, Morozumi N, Aizawa T, Ishii Y, et al. Changes in lumbar spondylolisthesis on axial-loaded MRI: do they reproduce the positional changes in the degree of olisthesis observed on X-ray images in the standing position?. Spine J. 2015 Jun 1. 15 (6):1255-62. [View Abstract]
5. Nakayama T, Ehara S. Spondylolytic spondylolisthesis: various imaging features and natural courses. Jpn J Radiol. 2015 Jan. 33 (1):3-12. [View Abstract]
6. Segebarth B, Kurd MF, Haug PH, Davis R. Routine Upright Imaging for Evaluating Degenerative Lumbar Stenosis: Incidence of Degenerative Spondylolisthesis Missed on Supine MRI. J Spinal Disord Tech. 2015 Dec. 28 (10):394-7. [View Abstract]
7. Özdoğan S, Kaya M, Demirel N, Düzkalır AH, Yaltırık CK. Isolated C5 Vertebrae Dislocation with Trauma: An Extremely Rare Case of Isolated C5 Dislocation. Am J Case Rep. 2017 Nov 28. 18:1256-1260. [View Abstract]
8. Smith JS, Shaffrey CI, Fu KM, Scheer JK, Bess S, Lafage V, et al. Clinical and radiographic evaluation of the adult spinal deformity patient. Neurosurg Clin N Am. 2013 Apr. 24(2):143-56. [View Abstract]
9. Jeong HY, You JW, Sohn HM, Park SH. Radiologic evaluation of degeneration in isthmic and degenerative spondylolisthesis. Asian Spine J. 2013 Mar. 7(1):25-33. [View Abstract]
10. Amato M, Totty WG, Gilula LA. Spondylolysis of the lumbar spine: demonstration of defects and laminal fragmentation. Radiology. 1984 Dec. 153(3):627-9. [View Abstract]
11. Epstein NE, Hollingsworth RD. Nursing review of diagnosis and treatment of lumbar degenerative spondylolisthesis. Surg Neurol Int. 2017. 8:246. [View Abstract]
12. Khelifi A, Saadaoui F. Traumatic Spondylolisthesis of the Axis. N Engl J Med. 2017 May 4. 376 (18):1782. [View Abstract]
13. Kovacs FM, Royuela A, Jensen TS, Estremera A, Amengual G, Muriel A, et al. Agreement in the interpretation of magnetic resonance images of the lumbar spine. Acta Radiol. 2009 Jun. 50(5):497-506. [View Abstract]
14. Chung JY, Kim SK, Jung ST, Lee KB, Seo HY, Hu CY, et al. Spontaneous reduction finding: magnetic resonance imaging evaluation of segmental instability in spondylolisthesis. Asian Spine J. 2012 Dec. 6(4):221-6. [View Abstract]
15. Chaput CD, Allred JJ, Pandorf JJ, Song J, Rahm MD. The significance of facet joint cross-sectional area on magnetic resonance imaging in relationship to cervical degenerative spondylolisthesis. Spine J. 2013 Feb 25. [View Abstract]
16. Kraft CN, Pennekamp PH, Becker U, Yong M, Diedrich O, Lüring C, et al. Magnetic Resonance Imaging Findings of the Lumbar Spine in Elite Horseback Riders: Correlations With Back Pain, Body Mass Index, Trunk/Leg-Length Coefficient, and Riding Discipline. Am J Sports Med. 2009 Jul 2. [View Abstract]
17. Huang KY, Lin RM, Lee YL, Li JD. Factors affecting disability and physical function in degenerative lumbar spondylolisthesis of L4-5: evaluation with axially loaded MRI. Eur Spine J. 2009 Dec. 18(12):1851-7. [View Abstract]