Diagnosis of Spondylolisthesis

Diagnostic Testing for Spondylolisthesis

Evaluation of spondylolisthesis includes a patient history, a physical examination, and radiological imaging studies.

Patient History

The patient history includes questions regarding:

• Overall health of patient - history of smoking, surgery, occupation, lifestyle, lower back pain
• Duration of symptoms
• Activities that exacerbate the pain
• Location of pain
• Exercise history, sports participation and relation to pain
• Acute or gradual onset of pain

Physical Examination

During the physical examination, the physician will pay particular attention to the following:

• Body habitus - the physique or body build
• Body posture
• Spinal alignment
• Spinal mobility
• Presence of muscle spasm
• Lower spine range of motion
• Pain on flexion or extension - patient may have pain raising legs straight up
• Positions that provoke the pain or radiculopathy
• Hamstring muscle tightness
• Muscle strength in legs
• Reflexes and sensation in the legs
• Dermatomes - areas of the skin supplied by nerve fibers originating from a single dorsal nerve root. Evaluation is important in order to recognize nerve root damage or radiculopathy. Radiculopathy is suspected when there is loss of sensation in a dermatome.
• Gait pattern - to assess the degree to which the patient walks with knees flexed, lumbar stiffness, and lordosis or kyphosis

• Neurological signs - these are present in up to one-third of individuals with spondylolisthesis and may include:

  • atrophy of muscle
  • reflex changes
  • weakness
  • bowel/bladder symptoms

In patients with high-grade spondylolisthesis, the doctor will evaluate:

• Clinical deformity
• Postural alignment
• Spinal mobility
• Neurological signs and symptoms

In adults with low grade spondylolisthesis, there is usually minimal or no gait disturbance noticeable since the deformity is longstanding and the patient has usually unknowingly compensated for gait disturbances. The source of pain is mechanical and is worsened by activity so relief usually comes with rest, whereas, with high grade spondylolisthesis, there is more neurological involvement making pain relief more difficult to achieve.

Imaging Studies

Imaging (radiologic) studies are extremely valuable for visualizing the degree of vertebral slip as well as stress injury or fracture of the pars. An X-ray is usually the first radiological image taken since it clearly defines the spinal structures and their relative positions. Plain lumbosacral X-rays (anterior, posterior, lateral, and oblique views) often demonstrate cracks or fractures in the pars interarticularis (sometimes called the "Scottie dog" sign on an oblique X-ray).

A standing, lateral x-ray of the lumbosacral spine is used to determine:

• Severity or magnitude of forward slippage of the vertebra by the Meyerding scale

• Degree of slip angle - the higher the degree of the slip angle, the more serious the problem and the higher the chance for additional slippage. Measurement of the slip angle determines the degree of lumbosacral kyphosis (outward curvature of the spine). The normal angle of the lower spine is slightly lordotic (inwardly curved) but with high-grade spondylolisthesis, the angle is either neutral (totally flat) or kyphotic (outwardly curved). The more severe the angle, the greater the kyphosis. Some individuals present with signs of scoliosis (sideward curvature above the lumbosacral area. A high slip angle is associated with:

  • greater degree of spinal instability
  • progression of deformity before or after surgery
  • pseudoarthrosis (fusion failure)
  • anatomic compensation changes of the sacrum as the slip progress - the sacrum may become more vertically oriented to accommodate the slip of the upper vertebra
  • lumbar index - this quantifies the shape that L5 takes as a higher slip grade develops. It is used mostly to assess the risk of slip progression in children.

If the diagnosis is not clear from X-ray or if there is a need to see specific areas of the spine more clearly, other imaging modalities may be used including:

• Single-photon emission computed tomography (SPECT) - this is a bone scan that uses a radioactive isotope called technetium (Tc99-m) to view the spine and helps in early identification of stress injuries to the pars interarticularis. SPECT helps in localization of defects and fracture-healing potential. If a bone scan is positive, it indicates that slippage may still be ongoing which can impact therapy. If it is negative, the slippage is no longer acute and the potential for benefit from certain therapies such as fusion surgery is reduced.
• Computerized axial tomography (CAT scan) - very effective in the diagnosis of spondylolysis, disk degeneration, facet joint changes, stenosis, and presence or absence of bony structures around healed microfractures of the pars as well as cracks, unhealed microfractures, and the degree of severity of spondylolytic defects.

• Magnetic resonance imaging (MRI) - this is not as effective as CAT in visualizing bony detail but has the advantage of avoiding use of radiation. MRI is effective in visualizing:

  • soft tissue structures (nerves and disks between vertebrae) and their relationship to the vertebra
  • if adjacent disks have suffered damage (such as "wear and tear") because of the slippage
  • signs of edema (swelling) around the spondylolytic defect
  • nerve root compression and the presence of spinal stenosis

CAT scan and MRI are performed if there is a need to see bone damage more clearly than is visualized on an X-ray or if there is a need to determine the presence of nerve compression.