Spondylolisthesis (spondylo = spine, listhesis = slippage) refers to a slippage of one vertebral body over another usually due to defect in the pars interarticularis. This is a common injury of sports that involve repetitive flexion (bending forwards), extension (bending backwards) and rotation of the lower back, such as in cricket fast bowling.

The mechanism involves repeated bending stresses around the thinnest part of the lower vertebrae (pars interarticularis) eventually resulting in a break in the vertebra – Spondylolysis), usually L4-L5 or L5-S1. In more severe cases, the involved vertebra may slip forward, ie. Spondylolisthesis (as per diagram below).

Types and Causes

There are two main theories on what causes the increased stresses on pars interarticularis: 1) Repeated Hyperextension (increased strain from high forces through superior/inferior facets), and 2) Repeated Hyperflexion (erector spinae resists movement as downward pull increasing stress on pars interarticularis).

1. Isthmic/Spondylolysis (50% of cases)

  • Due to acute or repetitive fatigue leading to stress fracture of the pars interarticularis, more common in males > females.
  • Common sports include gymnastics, cricket, weight-lifting, football.
  • Typical x-ray appearance = neck of the ‘Scotty Dog’

2. Degenerative (25%)

  • Due to degeneration of discs and facet joints; common in 40+ year olds and females > males
  • Causes long-standing instability, most common at L4-5 level

3. Dysplastic/Congenital (14-21%)

  • Due to thin vertebral bones or defective facet joints
  • Most common during growth spurt and females > males

4. Traumatic and Pathological

  • Less common, due to acute fracture of the spine or bone problems (eg. severe osteoporosis or bone tumours, usu. metastatic)

Classifications and Grades of Severity

The degree of severity (slippage) is graded by how much a vertebral body has slipped forward over the body below it.

GRADE % of vertebral body slipped forward
Grade 1 <25%
Grade 2 25-50%
Grade 3 50-75%
Grade 4 75-100%
Grade 5 Vertebral body completely fallen off

Signs & Symptoms

  • Often asymptomatic initially
  • Low back pain +/- buttock and leg pain, especially after exercise (may feel like a muscle strain)
  • Pain (sciatica) +/- weakness in one or both legs (if severe slippage there could be nerve compression and narrowing of spinal canal – may require MRI)
  • Aggravating factors are activity, standing, extension, rotation
  • Easing factor is rest, sitting
  • X-ray: slipping seen on a lateral view
  • Palpable slip
  • Tight hamstrings/ilipsoas often with spasm
  • Increased lumbar spine lordosis
  • Waddling gait

Treatment

1. Conservative

  • Medication (to assist with pain, inflammation and spasm)
  • Interferential therapy, ice/heat as required for pain relief
  • Back care advice and education
  • Activity restrictions (no heavy lifting, excessive bending/twisting/stooping etc that causes stress to lumbar spine)
  • Physiotherapy rehab program including:
    • Training for core stability and strengthening exercises for back, abdominals, legs
    • Stretching for hamstrings, ilipsoas
    • Postural education and exercises
    • Joint mobilisations to stiff joints above and below (not at level of slip)
    • Hydrotherapy, swimming, land-walking exercises
    • Progressive return to sport when painfree on extension and good spinal stabilisation

2. Surgery

Indications for surgery are:

  • If conservative management fails leading to prolonged and disabling pain and sciatica
  • Spinal canal stenosis
  • Symptomatic radiographic instability
  • Symptomatic Grade 3-4 slip
  • Cord compression signs (eg. hyperreflexia, sensory deficits, bowel/bladder dysfunction)
  • Lower motor neurone lesion

Options for surgery are:

  • Pars interarticularis repair
  • Decompression +/- fusion
  • Interbody fusion
  • Reduction of the listhetic deformity

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