Spondylolisthesis

Epidemiology:

  • Affects 5% of the population.
  • More common in males, but females often experience more severe cases.
  • Increased incidence among Eskimos.

Aetiology:

  • 25% of individuals with spondylolysis (pars defect) develop spondylolisthesis.
  • Most common at L5/S1, followed by L4/5, then L3/4.
  • Typically an acquired condition.

Classification:

Type (Wiltse):

  1. Dysplastic:
    • Facet joint anomaly with an intact posterior neural arch.
  2. Isthmic:
    • 2a: Stress fracture of pars (spondylolysis).
    • 2b: Elongated pars (most common).
    • 2c: Acute fracture of pars (rare).
  3. Other types:
    • Degenerative, post-traumatic, pathologic, iatrogenic (less common in children).

Grade (Myerding 1-5):

  • Grade 1: 0-25% slip.
  • Grade 2: 25-50% slip.
  • Grade 3: 50-75% slip.
  • Grade 4: 75-100% slip.
  • Grade 5: >100% (spondyloptosis).

Clinical Features:

  • Activity-related low back pain, exacerbated by extension activities.
  • Visible deformity.
  • Tight hamstrings.
  • L5 nerve root impingement.

Imaging:

  • Standing AP, Lateral, Oblique X-rays.
  • Scotty dog sign visible on oblique views.
  • CT scan is more effective than MRI.
  • Bone scan or SPECT scan may be used.

Risk of Progression:

  • High grade (3-4).
  • Dysplastic spondylolisthesis.
  • Females are at higher risk.
  • >40 degrees of lumbosacral kyphosis.
  • Progression is more likely pre-growth spurt.

Management:

Non-Operative:

  • Low grade asymptomatic: Observation.
  • Low grade symptomatic: Brace for 6 months.

Operative Indications:

  • High grade slip.
  • Evidence of progression to high grade.
  • Intractable pain.
  • Risk factors for progression:
    • Dysplastic spondylolisthesis (higher neurologic risk).
    • Intact posterior arch increases risk of neurologic injury if slip progresses.

Surgical Technique:

  • Posterolateral in situ instrumented fusion.
  • Concurrent decompression if there is neurologic compromise.
  • Reduction may be considered for high-grade slips but can increase the risk of L5 traction injury.

Complications:

  • Neurologic injury/cauda equina (rare).
  • Slip progression.
  • Pseudoarthrosis.
  • Continued pain.
  • Adjacent level degeneration.
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