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Posterior longitudinal ligament

The posterior longitudinal ligament (PLL) is a strong fibrous band running along the posterior surfaces of vertebral bodies within the vertebral canal, extending from the body of the axis (C2) down to the sacrum. It lies anterior to the spinal cord and posterior to the vertebral bodies and intervertebral discs, forming part of the spinal canal’s posterior wall. The PLL is narrower in the thoracic and lumbar regions and broader in the cervical region, and its fibers attach firmly to the intervertebral discs, helping to stabilize the spine and limit hyperflexion.

The PLL plays a crucial role in preventing posterior disc herniation from impinging on the spinal cord, while also serving as a landmark in spinal surgery and a reference for imaging assessment of degenerative changes, trauma, or ligamentous pathology.

Function

  • Stabilizes the posterior aspect of vertebral bodies

  • Limits hyperflexion of the spine

  • Prevents posterior disc herniation from compressing the spinal cord

  • Serves as a surgical and radiological landmark

  • Contributes to spinal canal integrity and spinal biomechanics

Synonyms

  • PLL

  • Ligamentum longitudinale posterius

  • Posterior vertebral ligament

MRI Appearance

T1-weighted images:

  • Appears as a thin, linear low signal intensity (hypointense) structure along the posterior vertebral bodies

  • Provides contrast against high signal bone marrow of vertebral bodies

  • Thickening or signal changes may indicate degenerative changes, ossification, or inflammation

T2-weighted images:

  • Remains low signal intensity (hypointense)

  • Adjacent disc and cerebrospinal fluid (CSF) provide contrast

  • Degenerative hypertrophy, ossification, or tearing may be seen as heterogeneous signal changes or focal thickening

STIR (Short Tau Inversion Recovery):

  • Normal PLL is low signal

  • Edema or inflammatory changes within the ligament appear hyperintense, highlighting acute injury or ossification-related stress

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal PLL usually shows no enhancement

  • Pathological PLL (ligamentitis, fibrosis, or tumor infiltration) may show mild to moderate enhancement, outlining abnormal tissue

CT Appearance:

  • Appears as a thin linear density along the posterior vertebral bodies

  • Ossification of the PLL (OPLL) is hyperdense and readily visible on CT

  • Axial, sagittal, and coronal reconstructions help assess thickness, ossification, and canal compromise

  • Excellent for detecting degenerative changes, calcification, trauma, or congenital abnormalities

MRI images

Posterior longitudinal ligament mri axial image -img-00000-00000

MRI images

Posterior longitudinal ligament c spine

CT images

Posterior longitudinal ligament ct axial image -img-00000-00000

CT image

Posterior longitudinal ligament ct axial iamge

MRI image

Posterior longitudinal ligament MRI sagittal anatomy image -img-00000-00000