A female, aged 27 years, was admitted to our hospital complaining of a radiating pain in the left leg. X-ray findigs showed the localized ossification situated at the posterior margin of the L4-5 vertebral body. On myelography posterior protrusion at L4-5 and L5-S1 intervertebral space were found. Her clinical signs seem to arisen from L5 nerve root compression due to the bony fragment at L4-5.
Laminectomy has been carried out. Bony fragment compressed L5 nerve root and dura mater posteriorly at the posterior site of the L4 vertebral body, and large protruded disc was found at L5-S1. Histologically, the excised bony fragment showed metaplastic ossification of the posterior longitudinal ligament.