Spondylolysis and Spondylolisthesis

CHAPTER 13

Spondylolysis and Spondylolisthesis

Introduction/Etiology/Epidemiology

• Spondylolysis and spondylolisthesis are common causes of low back pain in children and adolescents.

• Spondylolysis (common)

— Most commonly an acquired condition caused by repetitive hyperextension of the lumbar spine resulting in a stress reaction or fracture of the pars interarticularis (area between the facet joints in the posterior portion of the vertebrae) of the vertebral neural arch.

— L5 vertebra is most commonly affected, followed by L4, and rarely L1-L3

— Rarely seen before age 5 years and then gradually increases to the adult prevalence of 4% to 6% by age 20 years

— More common in males than females (6:1)

— More common in those participating in certain sports that require hyperextension and loading of the spine (eg, gymnastics, diving, American tackle football [lineman position], weight lifting, soccer, volleyball, softball pitching, wrestling)

— Prevalence is up to 35% in pediatric athletes and from 2% to 6% in nonathletes.

• Spondylolisthesis (less common)

— Forward translation (slip) of one vertebra on the adjacent caudal vertebra

— Most frequently seen between L5 and S1, but can occur at more cranial levels

— Etiology falls into 1 of 6 broad categories (Box 13-1).

— Severity is graded by the Meyerding classification, taking into account the percentage of forward slippage (Figure 13-1).

■Grade 1: less than 25% of the vertebral body width

■Grade 2: between 25% and 50%

■Grade 3: between 50% and 75%

■Grade 4: between 75% and 100%

■The term spondyloptosis is used when the posterior aspect of the cranial vertebral level “falls off ” the anterior aspect of the inferior vertebral body.

Box 13-1. Wiltse Classification of Spondylolisthesis According to Etiology

I.	Dysplastic: Congenital elongation of the pars
II.	Isthmic IIA. Disruption of pars as a result of stress fracture IIB. Elongation of pars without disruption (repeated healed microfractures) IIC. Acute fracture through pars (rare)
III.	Degenerative: Caused by facet joint arthritic changes
IV.	Traumatic: Fracture in an area of the posterior vertebral arch other than the pars
V.	Pathologic: Pars defect secondary to infectious or neoplastic process

Figure 13-1. In the Meyerding classification, severity is graded by the amount of vertebral slip. As indicated by arrow, this image depicts a grade 3 slip (50%–75%).

Signs and Symptoms

• Starts as activity-related back pain, but can progress to constant discomfort

— Worse with extension; in early stage can be relieved with flexion, but in later stages even flexion can elicit pain

— Occasional radiation to the buttock or posterior thigh

• Paraspinal tenderness and spasms

• Tight hamstrings and hip flexors, and deconditioning

• Limited lumbar mobility

— Extension is limited by pain; as a result, patients often adopt a standing posture of slight lumbar flexion.

— Forward flexion can be limited because of the extremely tight hamstrings but is typically not painful.

• Positive single-leg extension test (Stork test)

• Positive straight-leg raise and weakness, particularly of the extensor hallucis longus (L5) and the peroneal muscles (S1), may identify nerve root impingement, which can occur with spondylolysis but also may indicate disk herniation.

• Rarely, patients present with cauda equina syndrome (radicular symptoms, or sacral anesthesia and bowel and bladder dysfunction, but with normal sensory, motor, and deep tendon reflexes on examination of lower extremities).

— Usually associated with a high-grade slip (> 50%) or dysplastic type (Box 13-1)

Differential Diagnosis

• Lumbar muscle strain

• Lumbar disk herniation

• Facet joint arthropathy

• Sacroiliac joint dysfunction or sacroiliitis

• Lumbar diskitis

Diagnostic Considerations

• Imaging is required for diagnosis.

— Radiography

■For a child or adolescent presenting with back pain, standing anteroposterior and lateral views of the lumbar spine and spot lateral radiograph of L5-S1

■Additional images—standing right and left oblique views—may be helpful for identifying a unilateral pars defect, but add radiation exposure

■In patients with spondylolysis, the pars defect has been described as having the appearance of a collar on a Scotty dog (Scotty dog sign) on the oblique view (Figure 13-2).

■The spot lateral is the most sensitive view and is also important in quantifying the amount of forward displacement of L5 on S1 (Figure 13-3).

— Magnetic resonance imaging (MRI)

■Preferred imaging to evaluate for spondylolysis, especially in early stages; shows high signal changes in pars on T2-weighted and/or short tau inversion recovery (commonly known as STIR) images (Figure 13-4).

■Also helpful for evaluating nerve root compression, disk abnormalities, and stenosis, or for ruling out other sources of back pain, such as tumor or infection, especially in cases with higher grade slips

■Not as useful for imaging chronic pars defects or evaluating bony healing of pars stress fractures

— Thin-cut computed tomography scan of L5-S1

■Delineates bony morphology better than radiography or MRI

■Helpful to assess healing or to determine if the spondylolysis is chronic (Figure 13-5)

■Radiation exposure is twice as high as with 2 radiographs.

— Single-photon emission computed tomography (SPECT) bone scan

■SPECT is no longer routinely used for evaluation of spondylolysis due to high level of radiation and advances in MRI techniques that afford higher sensitivity for detecting spondylolysis.