Posterior ring apophyseal fracture

Posterior ring apophysis fractures occur in the immature skeleton, most commonly in the lumbar spine.

Epidemiology

Typically, adolescent males practicing sport activities.

Clinical presentation​

• back pain
• sciatica
• muscle weakness related with root innervation
• association with Scheuermann disease

Pathology

The ring apophysis is the part of the vertebral body connected to to intervertebral disc. It is firmly attached to disc fibrous annulus through Sharpey fibers through Sharpey fibers and its ossification occurs at 4 4-6 years old.

In the first years of life, the junction between ring apophysis and the rest of vertebral vertebral body is made through through a cartilage layer, that is only completely ossified around 18 years old, and this is a weak weak point.

Repeated trauma or stress forces can cause disc disc herniation through this layer causing ring ring apophysis fractures.

Radiographic features

CT

Considered best imaging modality. Findings include:

• osseous fragment displaced posteriorly to endplate with rectangular or arc shaped morphology on axial plane
• posterior endplate defect
• posterior disc herniation

MRI

• high T2/STIR signal of of acute fracture
• corner defect on posterior endplate margin
• disc degeneration and loss of height
• best method to evaluate nerve root / cauda equina compression

Differential diagnosis

On imaging consider

• Schmorl's node
• disc calcification/ossification
• calcified disc fragment
• posterior osteophyte