The posterior longitudinal ligament runs the full length of the spinal canal on the posterior surface of the vertebral bodies, narrowing at each vertebral body level in a dumbbell shape and widening over each disc. This narrowing is clinically significant because it is less effective at containing lateral disc herniations, explaining why posterolateral rather than central herniations most commonly cause radiculopathy.
| Origin | Posterior body of C2 (continuous with the tectorial membrane above) |
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| Insertion | Continuous along the posterior surfaces of all vertebral bodies and discs to the sacrum |
| Actions | Resists spinal flexion; contains disc herniations centrally; reinforces the posterior annulus fibrosus |
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Ossification of the posterior longitudinal ligament (OPLL) is a condition most prevalent in East Asian populations in which the PLL undergoes ectopic ossification and causes progressive cervical myelopathy from spinal cord compression. It is identified on CT as a dense structure in the spinal canal and requires surgical decompression when symptomatic. The PLL is the anatomical barrier that limits the posterior spread of vertebral body metastases into the spinal canal.
Ectopic bone formation within the posterior longitudinal ligament producing progressive cervical myelopathy from spinal cord compression, managed with anterior corpectomy or posterior laminoplasty.
