see also:

• back pain in the ED
• orthopaedics in the ED
• the lumbosacral spine Xray

• a common incidental finding on the L/S spine Xray in the ED which is usually long standing but may be the result of acute trauma and may be the cause of the back pain and nerve compression.
• spondylolisthesis refers to the forward slippage (anterolisthesis) of one vertebral body with respect to the one beneath it.
• most commonly occurs with L5 slipping over S1, but it can occur at higher levels (particularly degenerative types).
• it may cause any degree of symptoms, from minimal symptoms of occasional low back pain to incapacitating mechanical low back pain, radiculopathy from nerve root compression, and neurogenic claudication.

• 5 types:
  • congenital or dysplastic (type 1)
    • due to a defect in the upper sacrum or arch of L5.
    • 94% are associated spina bifida occulta and high rates of S1 foraminal nerve root compression exists, even with grade 1 slips
  • isthmic (type 2) (5% of people)
    • These typically present in the teenage or early adulthood years and are most common at L5-S1.
    • results from a defect in pars interarticularis, which permits forward slippage of the superior vertebra
    • The pars interarticularis, or isthmus, is the bone between the lamina, pedicle, articular facets, and the transverse process
    • The pars may be congenitally defective (eg, in spondylolytic subtype of isthmic spondylolisthesis) or undergo repeated stress under hyperflexion and rotation, resulting in microfractures.
    • 3 sub-types:
      • Lytic (ie, spondylolysis) or stress fracture of the pars
      • Elongated yet intact pars
      • Acutely fractured pars
    • risk factors:
      • genetics
      • both lumbar lordosis and rotational forces are also believed to play a role in the development of lytic pars defects and the fatigue of the pars in the young
      • an association exists between high levels of activity during childhood and the development of pars defects
    • clinical features:
      • variable pain
      • restricted spinal range of movement
      • hamstring tightness - inability to flex hips with fully extended knees
      • hyperlordosis of the lumbar and thoracolumbar regions
      • hyperkyphosis at lumbosacral junction (as the center of gravity shifts to compensate for slip progression)
      • high grade slips may result in palpable step off, gait difficulty and trunk shortening (if spondyloptosis occurs)
  • degenerative (type 3)
    • ~5% of elderly men and 9% elderly women - mainly L4/L5, and lesser prevalence at L3/4
    • The L5 nerve root is usually compressed from lateral recess stenosis as a result of facet and/or ligamentous hypertrophy, and causes weakness of the extensor hallucis longus
    • results from chronic disc degeneration and facet incompetence
    • spondylosis is a general term reserved for acquired age-related degenerative changes of the spine (ie, discopathy or facet arthropathy) that can lead to this type of spondylolisthesis
  • traumatic
    • rare, results from fracture of any part of the neural arch or pars that leads to listhesis
  • pathologic (type 5)
    • results from a generalized bone disease, such as Paget disease or osteogenesis imperfecta
  • post-surgical / iatrogenic complications (type 6)

• grade of slippage in the sagiital plane:
  • Grade 1 - Less than 25% of vertebral diameter
  • Grade 2 - 25-50%
  • Grade 3 - 50-75%
  • Grade 4 - 75-100%
  • Spondyloptosis - > 100% ⇒ trunk shortening

• surgical fusion MAY be indicated if high grade slip >50%, neurologic involvement, traumatic aetiology, or likely to progress to high grade slip:
  • age < 15 years
  • females
  • ligamentous laxity
  • type 1 dysplastic slip
  • lumbosacral hypermobility
• most will not have surgery and be advised to modify activities

• high grade slip >50%
• neurologic involvement with signs
• traumatic or iatrogenic aetiology
• Type 1 and type 2 slips, with evidence of instability, progression of listhesis, or lack of response to conservative measures
• Type 3 (degenerative) listhesis with gross instability and incapacitating pain
• Postural deformity and gait abnormality¹⁾