Posterior ring apophyseal fracture

• Osseous fragment displaced posteriorly to the endplate with rectangular or arc-shaped morphology on axial CT
• Posterior endplate cortical defect at the attachment site of Sharpey fibers
• High T2/STIR signal of acute fracture on MRI
• Corner defect on posterior endplate margin with associated disc herniation

• On CT, the fracture appears as an osseous fragment with rectangular or arc-shaped morphology displaced posteriorly to the vertebral endplate, best seen on axial imaging.
• A posterior cortical endplate defect is present at the site where the ring apophysis, a secondary ossification center, was attached to the vertebral body via Sharpey fibers.
• Four morphologic types exist: Type I avulsion of posterior cortical rim, Type II central cortical and cancellous fractures, Type III lateralized chip fractures, and Type IV spanning the entire posterior margin.
• On MRI, acute fractures demonstrate high T2 and STIR signal intensity within the fracture fragment, reflecting edema and early inflammatory response.
• Associated findings include posterior disc herniation, disc degeneration with loss of disc height, and potential compression of neural structures.
• The ring apophysis is a cartilaginous growth plate (until approximately age 18) connecting the posterior vertebral rim to the intervertebral disc, making this region mechanistically vulnerable.
• CT provides superior bony detail and is typically the first-line modality for diagnosis, while MRI is preferred for evaluating spinal cord and nerve root involvement.
• Most commonly occurs in the lumbar spine, particularly in adolescents during the vulnerable ossification window (ages 4-18 years).

• Schmorl node—central disc herniation through the endplate; distinguished by central rather than posterior location and lack of displaced cortical bone fragment.
• Posterior osteophyte—degenerative bony proliferation; lacks the acute fracture morphology and displaced fragment characteristic of ring apophyseal fracture.
• Disc calcification/ossification—calcified disc material without a distinct displaced osseous fragment or endplate cortical defect.
• Calcified disc fragment—calcification within herniated disc material; lacks the characteristic rectangular or arc-shaped fragment morphology and endplate attachment site.
• Limbus vertebra (normal variant)—triangular or quadrangular ossification at the vertebral corner; benign finding without acute fracture features or associated edema.

Describe the finding as 'posterior ring apophyseal fracture with osseous fragment showing [rectangular/arc-shaped] morphology displaced posteriorly from the [vertebral level], with associated posterior endplate defect and [degree] of posterior disc herniation.' Specify whether neural structures are compressed and note any associated degenerative features or height loss.

• Confusing posterior ring apophyseal fracture with the normal anatomic variant limbus vertebra, which is benign and does not require intervention.
• Misinterpreting the fracture as a Schmorl node (central disc herniation) by focusing on the disc component rather than the posterior displaced osseous fragment.
• Underestimating the clinical significance of what may initially appear as a small cortical defect, particularly if neural compression is not clearly evident on initial imaging.
• Relying solely on radiographs, which have limited sensitivity for detecting ring apophyseal fractures; CT is required for definitive diagnosis and characterization of fragment morphology.