posterior longitudinal ligament

posterior longitudinal ligament The posterior longitudinal ligament is a fibrous structure running within the vertebral canal along the posterior aspects of the vertebral bodies from the axis to the sacrum. It contributes to spinal stability and limits hyperflexion while interacting with adjacent dura mater and epidural venous plexus components. Its clinical relevance spans degenerative disease, trauma, infection, and surgical approaches to the spine.

Anatomy

The posterior longitudinal ligament extends from the posterior surface of the body of the axis (C2) inferiorly to the upper part of the sacrum, lying on the posterior aspects of the vertebral bodies and intervertebral discs within the vertebral canal. Laterally it narrows over the vertebral bodies and is broader at the intervertebral discs, with attachments to the annulus fibrosus of the discs and to the periosteum of the vertebral bodies; it is separated from the dura mater by the epidural space that contains the extradural fat and the internal vertebral venous plexus. The ligament’s collagenous fibers and elastic components vary along the cervical, thoracic, and lumbar regions, with noted thickening at the cervical level near the atlas–axis complex and tapering in the thoracic region adjacent to the thoracic vertebrae. Embryologically it derives from paraxial mesoderm and segmental sclerotome contributions similar to other axial skeletal ligaments described in classic texts such as those by Andreas Vesalius and later anatomists at institutions like the Royal Society. Histologically it showcases dense regular connective tissue with interspersed fibrocartilage at disc attachments, comparable to structures discussed in works by Henry Gray.

Function

The ligament functions as a restraining band preventing excessive flexion and posterior disc herniation, contributing to the integrity of the vertebral column during dynamic activities such as in clinical scenarios studied by Sir William Osler and in orthopedic practice at centers like Mayo Clinic. It helps maintain alignment between vertebral bodies and provides a barrier limiting posterior migration of nucleus pulposus material; in concert with the anterior longitudinal ligament and the interspinous and supraspinous ligaments, it forms part of the complex evaluated in spinal stability classifications referenced in trauma guidelines by entities such as the American Association of Neurological Surgeons and AO Spine. The ligament’s relationship with the epidural venous plexus and dura affects symptom generation in processes like epidural abscesses described in case series from tertiary hospitals including Massachusetts General Hospital.

Clinical significance

Degenerative changes including hypertrophy, ossification, and calcification can narrow the spinal canal and contribute to myelopathy, a phenomenon particularly recognized with ossification of the posterior longitudinal ligament (OPLL), which has been extensively reported in populations in Japan and studied by groups at Tokyo University and Kyoto University Hospital. Traumatic disruption or tearing can produce instability and predispose to posterior disc displacement implicated in acute spinal cord injury cases managed at trauma centers like Johns Hopkins Hospital. Infectious processes such as tuberculous spondylitis and pyogenic epidural abscess may involve or abut the ligament, producing radiculopathy and cord compression observed in reports from the World Health Organization and national health services. Neoplastic invasion by metastases from organs like breast cancer or prostate cancer may encroach upon the ligament and the posterior vertebral body margin. Clinically, compression of the spinal cord by pathology posterior to the vertebral body manifests with signs documented in neurology texts and taught in courses at institutions like Columbia University and the University of Oxford.

Imaging and diagnosis

Evaluation of posterior longitudinal ligament pathology employs modalities available at major radiology departments such as those at Cleveland Clinic and Mayo Clinic: magnetic resonance imaging (MRI) provides high-contrast visualization of ligamentous thickening, disc herniation, and spinal cord signal changes; computed tomography (CT) excels in detecting calcification and ossification patterns characteristic of OPLL as reported in radiologic series from Johns Hopkins Hospital; and myelography—historically described in literature from centers like UCSF—can outline compressive lesions when MRI is contraindicated. Plain radiography may show ossified density along the posterior vertebral margins in advanced cases, while dynamic flexion-extension radiographs can reveal instability. Imaging interpretation follows criteria from professional bodies such as the Radiological Society of North America and imaging findings guide multidisciplinary care recommended by organizations like the European Spine Journal.

Surgical considerations

Surgical management addresses decompression and stabilization and is tailored to pathology location, extent, and patient factors; approaches include anterior cervical discectomy and fusion (ACDF), posterior laminectomy or laminoplasty, and combined anterior-posterior procedures commonly performed by spine teams at institutions such as Mayo Clinic and Cleveland Clinic. When ossification of the posterior longitudinal ligament causes myelopathy, anterior removal of OPLL mass with fusion or posterior indirect decompression via laminoplasty—techniques refined by surgeons at Keio University and centers in Japan—are considered. In trauma, fixation constructs and alignment restoration reference classification systems by AO Spine and guidelines endorsed by North American Spine Society. Perioperative risks include dural tear, cerebrospinal fluid leak, epidural hematoma involving the internal vertebral venous plexus, and infection managed per protocols from institutions like Johns Hopkins Hospital and Massachusetts General Hospital. Preoperative planning integrates advanced imaging, neurologic assessment, and multidisciplinary discussion with anesthesiology teams at tertiary centers such as Stanford Health Care.

Category:Spinal ligaments