Annular Fissure¶
Definition¶
An annular fissure (also called annular tear) is a disruption of the concentric collagen fibers of the annulus fibrosus. These fissures or tears can be seen in both degnerative change as well as with acute injury and can serve as a pathway for nuclear material to herniate posteriorly.
Classification¶
| Type | Orientation | Location | Significance |
|---|---|---|---|
| Concentric (Type I) | Parallel to endplate, between annular lamellae | Any location | Delamination of annular layers; common with aging |
| Radial (Type II) | Perpendicular, from nucleus to outer annulus | Usually posterior or posterolateral | Most clinically significant; pathway for disc herniation |
| Transverse (Type III) | Horizontal at peripheral annular attachment | Usually anterior | Often related to trauma; Schmorl nodes may be associated |
Imaging Findings¶
MRI¶
- High-intensity zone (HIZ): focal bright T2 signal in the posterior annulus on sagittal T2-weighted images — this is the MRI correlate of a radial annular fissure
- Best seen on sagittal T2
- The HIZ is typically small, well-defined, and located at the posterior annular margin
- May enhance with gadolinium (granulation tissue/vascularization in the fissure)
Clinical Pearl
The high-intensity zone (HIZ) was originally proposed as a specific marker for a painful disc. While the HIZ does indicate an annular disruption, its specificity for pain is debated — HIZ is found in up to 25% of asymptomatic individuals. It should be considered one piece of the puzzle, not a definitive indicator of discogenic pain. Its presence alongside disc degeneration, Modic changes, and concordant clinical symptoms increases the likelihood of a symptomatic disc.
Key Points¶
- Annular fissures are tears in the annulus fibrosus — an early sign of disc degeneration
- Radial fissures (Type II) are most clinically important — they allow nuclear herniation
- The HIZ on sagittal T2 MRI is the imaging correlate of a posterior annular fissure
- HIZ is found in up to 25% of asymptomatic people — specificity for pain is limited
- Must correlate with clinical symptoms and other imaging findings
References¶
- Fardon DF, Williams AL, Dohring EJ, Murtagh FR, Gabriel Rothman SL, Sze GK. Lumbar disc nomenclature: version 2.0: Recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology. Spine J. 2014;14(11):2525–2545. PubMed | AJNR co-publication
- Peng B, Hou S, Wu W, Zhang C, Yang Y. The pathogenesis and clinical significance of a high-intensity zone (HIZ) of lumbar intervertebral disc on MR imaging in the patient with discogenic low back pain. Eur Spine J. 2006;15(5):583–587. PMC
- Bartynski WS, Agarwal V, Trang H, et al. Enhancing Annular Fissures and High-Intensity Zones: Pain, Internal Derangement, and Anesthetic Response at Provocation Lumbar Discography. AJNR Am J Neuroradiol. 2023;44(1):95–104. PMC
- Teraguchi M, Yim R, Cheung JP, Samartzis D. The association of high-intensity zones on MRI and low back pain: a systematic review. Scoliosis Spinal Disord. 2018;13:22. PubMed
- Munter FM, Wasserman BA, Wu HM, Yousem DM. Serial MR imaging of annular tears in lumbar intervertebral disks. AJNR Am J Neuroradiol. 2002;23(7):1105–1109. PubMed
- Smithuis R. Lumbar Disc Nomenclature 2.0. The Radiology Assistant. 2017. radiologyassistant.nl
- Annular fissure. Radiopaedia.org. radiopaedia.org/articles/annular-fissure