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Annular Tear

Summary

  • Disruption of the annulus fibrosus of an intervertebral disc ("annular fissure" is the preferred nomenclature)
  • Usually degenerative, occasionally traumatic
  • The hallmark is a T2 high-intensity zone (HIZ) in the posterior annulus, which may enhance1

Pathophysiology

  • Fissures are classified as concentric (between lamellae), radial (nucleus to outer annulus) or transverse (peripheral, near the ring apophysis)
  • Radial fissures are the type that permits disc herniation and are implicated in discogenic pain

Demographics

  • Most common in adults aged 30-50 years
  • Higher prevalence in:
    • Males
    • Individuals with physically demanding occupations
    • Those with a history of trauma or repetitive stress

Diagnosis

  • Clinical presentation:
    • Low back pain, often with radicular symptoms
    • Pain may worsen with certain movements or positions
  • Physical examination:
    • Limited range of motion
    • Positive straight leg raise test (for lower lumbar tears)
  • Diagnostic tests:
    • MRI is the gold standard for diagnosis
    • Discography may be used in select cases

Imaging

  • MRI findings:
    • High-intensity zone (HIZ) on T2-weighted images
    • Focal hyperintensity in the posterior annulus on T2-weighted images
    • Contrast enhancement of the outer annulus on post-gadolinium T1-weighted images
  • CT discography:
    • Contrast leakage into the annular tear
    • Useful for correlating pain with specific disc levels

panels-1

  • A 45-year-old patient presented with an acute radiculopathy in the left L4 distribution.
  • While there was only minimal intervertebral foraminal narrowing, the L4-5 disc that contained a T2-hyperintense annular tear made contact with the left L4 nerve root.

Treatment

  • Conservative: analgesia, activity modification and physiotherapy
  • Epidural steroid injection or surgery reserved for refractory radiculopathy

Differential diagnosis

Imaging differential Differentiating feature
Disc herniation Focal protrusion/extrusion of disc material beyond the annulus, often with nerve root contact
Modic type 1 endplate change Endplate T1 hypointensity/T2 hyperintensity, distinct from an intra-annular HIZ
Discitis/osteomyelitis Endplate erosion, disc-space T2 hyperintensity and rim-enhancing collection
Vertebral metastasis Enhancing marrow-replacing lesion with cortical destruction

  1. Hadjipavlou et al. Pathomechanics and clinical relevance of disc degeneration and annular tear: a point-of-view review. 1999. American journal of orthopedics (Belle Mead, N.J.) - Open in new tab. ↩