Logo

    Related Topics

    From Musculoskeletal System

    Sternum
    Breastbone located in the center of the chest.
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.
    Rotator Cuff Tendons
    Tendons of the rotator cuff muscles.
    Medial Collateral Ligament (MCL)
    Knee ligament that stabilizes the inner knee.
    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Tibialis Anterior
    Muscle that dorsiflexes and inverts the foot.
    Phalanges (14 bones)
    14 bones forming the toes.
    Pivot Joints
    e.g., atlanto-axial joint
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Clavicle
    Collarbone connecting the arm to the body.
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Patella
    Knee cap, protecting the knee joint.
    Occipital Bone
    Bone forming the back and base of the skull.
    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.
    Levator Ani
    Pelvic floor muscle responsible for lifting the anus.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Flexor and Extensor Groups
    Muscles responsible for flexing and extending the hand and wrist.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Temporalis
    Muscle involved in closing the jaw.
    Mandible
    Lower jawbone that houses the teeth.
    Coccygeus
    Pelvic floor muscle supporting the coccyx.
    Parietal Bones
    Bones forming the sides and roof of the skull.

    Posterior Longitudinal Ligament

    Reviewed by our medical team

    Spinal ligament running along the back of the vertebral column.

    1. Overview

    The posterior longitudinal ligament (PLL) is a major stabilizing ligament of the vertebral column. It runs along the posterior surface of the vertebral bodies, within the vertebral canal, and helps maintain spinal alignment while limiting hyperflexion. The PLL is narrower and weaker than its anterior counterpart (the anterior longitudinal ligament) but is critically positioned to protect neural elements, particularly the spinal cord and nerve roots.

    2. Location

    The PLL is located inside the vertebral canal, along the posterior aspects of the vertebral bodies:

    • Extends from: The body of the axis (C2 vertebra) to the sacrum.

    • Positioned posterior to: The vertebral bodies and intervertebral discs.

    • Anterior to: The spinal cord and meninges.

    • Spans: The entire length of the vertebral column except the atlas (C1), with a continuation into the tectorial membrane superiorly.

    3. Structure

    The PLL is a narrow, ribbon-like ligament composed of dense regular connective tissue:

    • Width: Narrow over vertebral bodies and slightly wider over intervertebral discs.

    • Fibers: Longitudinally oriented collagen fibers arranged in superficial (long) and deep (shorter, segmental) layers.

    • Attachment: Firmly adheres to intervertebral discs and vertebral margins, but less so to the vertebral bodies themselves.

    • Histology: Dense collagen with some elastic fibers; provides strength with limited flexibility.

    4. Function

    The posterior longitudinal ligament plays several important mechanical roles:

    • Limits hyperflexion: Resists excessive forward bending of the spine, especially in the cervical and thoracic regions.

    • Supports intervertebral discs: Provides posterior reinforcement of the annulus fibrosus.

    • Maintains alignment: Helps keep vertebral bodies in a straight column and contributes to overall spinal stability.

    5. Physiological role(s)

    Although passive, the PLL supports various physiological processes by maintaining the integrity of the spinal column:

    • Protects neural elements: Forms part of the anterior wall of the vertebral canal, safeguarding the spinal cord and nerve roots.

    • Limits disc protrusion: Acts as a barrier to posterior migration of intervertebral disc material (e.g., in disc herniation).

    • Contributes to proprioception: Contains mechanoreceptors that provide feedback to the central nervous system regarding spinal position and motion.

    6. Clinical Significance

    The PLL is involved in several spinal pathologies and clinical scenarios:

    • Disc herniation:

      • Posterolateral disc herniation is more common than posterior due to the PLL’s reinforcement in the midline but relative weakness laterally.

    • Spinal canal stenosis:

      • Thickening or ossification of the PLL (as seen in OPLL) can compress the spinal cord or cauda equina, leading to neurological deficits.

    • Ossification of the posterior longitudinal ligament (OPLL):

      • More common in East Asian populations; can cause progressive myelopathy due to spinal cord compression.

    • Trauma and instability:

      • Disruption of the PLL (e.g., in spinal fractures or dislocations) is considered a marker of spinal instability and may warrant surgical intervention.

    • Surgical relevance:

      • The PLL is often removed during spinal decompression surgeries like laminectomy or discectomy to relieve pressure on the spinal cord or nerves.

    Did you know? Tendons attach muscles to bones.