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    Related Topics

    From Musculoskeletal System

    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Wormian Bones
    Sutural bones in the skull.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Sutures (in the skull)
    Fibrous joints between skull bones.
    Annular Ligament
    The annular ligament is a strong fibrous band encircling the head of the radius, stabilizing the proximal radioulnar joint and allowing smooth rotation of the forearm.
    Metacarpals (5 bones)
    5 bones forming the palm of the hand.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Hinge Joints
    e.g., elbow, knee
    Phalanges (14 bones)
    14 bones forming the toes.
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Ischium
    Part of the pelvis that supports weight while sitting.
    Pivot Joints
    e.g., atlanto-axial joint
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Tarsals (7 bones)
    7 ankle bones.
    Pelvic Floor Muscles
    Muscles that support pelvic organs.
    Masseter
    Muscle that elevates the mandible.
    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Acetabulum
    The acetabulum is the pelvic socket that connects with the femoral head to form the hip joint, vital for stability, movement, and weight-bearing.
    Lateral Collateral Ligament (LCL)
    Knee ligament that stabilizes the outer knee.
    Triceps Brachii
    Muscle responsible for elbow extension.
    Rectus Abdominis
    Abs muscle that flexes the trunk.
    Trapezius
    Muscle responsible for moving, rotating, and stabilizing the scapula.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).

    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? Each human hand has 27 bones.