Spondylolisthesis

Etiology

Spondylolisthesis commonly classifies as one of five major etiologies: degenerative, isthmic, traumatic, dysplastic, or pathologic. Degenerative spondylolisthesis occurs from degenerative changes in the spine without any defect in the pars interarticularis. It is usually related to the combined facet joint and disc degeneration leading to instability and forward movement of one vertebral body relative to the adjacent vertebral body. Isthmic spondylolisthesis results from defects in the pars interarticularis. The cause of isthmic spondylolisthesis is undetermined, but a possible etiology includes microtrauma in adolescence related to sports such as wrestling, football, and gymnastics, where repeated lumbar extension occurs. Traumatic spondylolisthesis occurs after fractures of the pars interarticularis or the facet joint structure and is most common after trauma. Dysplastic spondylolisthesis is congenital and secondary to variation in the orientation of the facet joints to an abnormal alignment.  In dysplastic spondylolisthesis, the facet joints are more sagittally oriented than the typical coronal orientation. Pathologic spondylolisthesis can be from systemic causes such as bone or connective tissue disorders or a focal process, including infection, neoplasm, or iatrogenic origin. Additional risk factors for spondylolisthesis include a first-degree relative with spondylolisthesis, scoliosis, or occult spina bifida at the S1 level.[1]

Epidemiology

Spondylolisthesis most commonly occurs in the lower lumbar spine but can also occur in the cervical spine and rarely, except for trauma, in the thoracic spine. Degenerative spondylolisthesis predominately occurs in adults and is more common in females than males with increased risk in the obese. Isthmic spondylolisthesis is more common in the adolescent and young adult population but may go unrecognized until symptoms develop in adulthood. There is a higher prevalence of isthmic spondylolisthesis in males. Dysplastic spondylolisthesis is more common in the pediatric population, with females more commonly affected than males. Current estimates for prevalence are 6 to 7% for isthmic spondylolisthesis by the age of 18 years, and up to 18% of adult patients undergoing MRI of the lumbar spine. Grade I spondylolisthesis accounts for 75% of all cases. Spondylolisthesis most commonly occurs at the L5-S1 level with an anterior translation of the L5 vertebral body on the S1 vertebral body. The L4-5 level is the second most common location for spondylolisthesis. 

Pathophysiology

Any process that can weaken the supports keeping vertebral bodies aligned can allow spondylolisthesis to occur. As one vertebra moves relative to the adjacent vertebrae, local pain can occur from mechanical motion or radicular or myelopathic pain can occur due to compression of the exiting nerve roots or spinal cord, respectively. Pediatric patients are more likely to increase spondylolisthesis grade when going through puberty. Older patients with lower grades I or II spondylolistheses are less likely to progress to higher grades over time.

History and Physical

Patients typically have intermittent and localized low back pain for lumbar spondylolisthesis and localized neck pain for cervical spondylolisthesis. The pain is exacerbated by flexing and extending at the affected segment, as this can cause mechanic pain from motion. Pain may be exacerbated by direct palpation of the affected segment. Pain can also be radicular in nature as the exiting nerve roots become compressed due to the narrowing of nerve foramina as one vertebra slips on the adjacent vertebrae, the traversing nerve root (root to the level below) can also be impinged through associated lateral recess narrowing, disc protrusion, or central stenosis. Pain can sometimes improve in certain positions such as lying supine. This improvement is due to the instability of the spondylolisthesis that reduces with supine posture, thus relieving the pressure on the bony elements as well as opening the spinal canal or neural foramen. Other symptoms associated with lumbar spondylolisthesis include buttock pain, numbness, or weakness in the leg(s), difficulty walking, and rarely loss of bowel or bladder control.

Evaluation

Anteroposterior and lateral plain films, as well as lateral flexion-extension plain films, are the standard for the initial diagnosis of spondylolisthesis. One is looking for the abnormal alignment of one vertebral body to the next as well as possible motion with flexion and extension, which would indicate instability. In isthmic spondylolisthesis, there may be a pars defect, which is termed the "Scotty dog collar." The "Scotty dog collar" shows a hyperdensity where the collar would be on the cartoon dog, which represents the fracture of the pars interarticularis. Computed tomography (CT) of the spine provides the highest sensitivity and specificity for diagnosing spondylolisthesis. Spondylolisthesis can be better appreciated on sagittal reconstructions as compared to axial CT imaging. MRI of the spine can show associated soft tissue and disc abnormalities, but it is relatively more challenging to appreciate bony detail and a potential pars defect on MRI.[2][3]

Treatment / Management

For grade I and II spondylolisthesis, treatment typically begins with conservative therapy, including nonsteroidal anti-inflammatory drugs (NSAIDs), heat, light exercise, traction, bracing, and/or bed rest. Approximately 10% to 15% of younger patients with low-grade spondylolisthesis will fail conservative treatment and need surgical treatment. No definitive standards exist for surgical treatment. Surgical treatment includes a varying combination of decompression, fusion with or without instrumentation, or interbody fusion. Patients with instability are more likely to require operative intervention.  Some surgeons recommend a reduction of the spondylolisthesis if able as this not only decreases foraminal narrowing but also can improve spinopelvic sagittal alignment and decrease the risk for further degenerative spinal changes in the future. The reduction can be more difficult and riskier in higher grades and impacted spondylolisthesis.[4][5][6][7][8][2][9][10](A1)

Differential Diagnosis

• Degenerative  Lumbar Disc Disease

• Lumbar Disc Problems

• Lumbosacral Disc Injuries

• Lumbosacral Discogenic Pain Syndrome

• Lumbosacral Facet Syndrome

• Lumbosacral Radiculopathy

• Lumbosacral Spine Acute Bony Injuries

• Lumbosacral Spondylosis

• Myofascial Pain in Athletes