Spine, pelvis, and tempromandicular joint anatomy

Spine and pelvis region

Components of spine (vertebral column)

• 24  vertebrae
• 2 fused bones the sacrum and coccyx
  • Divided into 5 areas- cervical, thoracic, lumbar, sacral, and coccygeal

Function of spine

• Provides a strong and flexible framework that supports the body’s weight, allowing for standing, walking, and moving freely.
• Encases and protects the spinal cord
• Connecting discs allow for a wide range of motion, including flexion, extension, rotation, and lateral flexion.
• Thoracic spine and ribs protects vital internal organs such as the heart and lungs.
• Maintain proper balance and posture by distributing the body’s weight evenly.

Bony structures

• Typical components in definitions below

Special bony components of each segment

• Cervical: supports head and neck, muscles are attached to allow a large freedom of movement

  • C1 and C2 allow for rotation without compression of spinal cord

• Costotransverse and costovertebral

  • Articulation between ribs and transverse processes of spine
  • Prominent (easily palpable) spinous process

• Thoracic: supports axial loading, attached to ribs to form the most rigid section of the spine.

  • Prominent (easily palpable) spinous process

• Lumbar: largest vertebrae transfer wt. bearing loads and increases mobility of the trunk.

• Sacrum

  • Composed of 5 fused bones

Special joints of spine

• Atlanto-occipital joint- articulation between occipital bone and C1 which allows head nodding to occur
  • Atlanto-axial joint- articulation between C1 and C1 which allows for head rotation
• Facet joints
  • Aid in movement of spine as a whole
• Intervertebral joints
  • Allow for movement at single vertebral body and assist with transferring load from one vertebral body to another
• Sacroiliac joints
  • Aid in movements of lower axial skeleton and lower extremities

Other important features of spine

• Intervertebral discs
  • Annulus fibrosis
    • Composed of collagen fibers, fibrocartilage, and water
    • Vascularized and neural connections
    • Functions to maintain integrity of vertebral column during compression, torsion, shearing, and distracting forces
  • Nucleus pulposus
    • Composed of proteoglycans and water with minimal collagen
    • Avascular and no neural connections
    • Functions to maintain integrity of vertebral column during compression, torsion, shearing, and distracting forces
  • Vertebral endplate
    • Composed of proteoglycans, collagen, fibrocartilage, and water
    • Functions to diffuse nutrients to annulus fibrosis and nucleus pulposus

Ligaments

• Alar
  • Connects dens to occipital condyle
  • Functions to limit flexion, contralateral lateral flexion, and contralateral rotation
• Anterior longitudinal ligament
  • Connects anterior and lateral surfaces of vertebral bodies from C2- sacrum
  • Function to reinforce the anterolateral portion of the intervertebral discs
• Posterior longitudinal ligament
  • Located on the posterior surface of vertebral bodies from C2- sacrum
  • Function to prevent hyperflexion of the vertebral column and to protect the spinal cord from foreign objects and displaced disc material.
• Ligamentum flavum
  • Connects vertebra to the lamina above it; runs from C2-sacrim
  • Function to limit flexion (greatest in lumbar spine)
• Interspinous ligament
  • Runs between spinous processes
  • Function to limit flexion
• Iliolumbar ligament
  • Connects L5 vertebrae to ilium
  • Functions to limit motion between L5 and S1

Capsule

• Facet joints
  • Role is to provide reinforcement to ligaments by limiting motion and stabilizing spine
• Sacroiliac joints
  • Role is stabilizing the sacroiliac joint, limiting its movement, and protecting the joint by distributing biomechanical loads.

Nerves

• Spinal nerves are mixed nerves that connect the spinal cord to the rest of the body. They carry both sensory (dorsal rami) and motor (ventral rami) information between the central nervous system (brain and spinal cord) and the peripheral nervous system (body and muscles).
• Location of spinal nerves
  • Cervical: exit at the level above the associated vertebrae
  • Thoracic/lumbar: exit below the level of associated vertebrae

Spinal and pelvis movements

General rules regarding facet joint opening and closing

• Flexion (bending forward):
  • When you bend forward, the facet joints on the back of the spine open up, allowing for more space between the vertebrae.
• Extension (bending backward):
  • Conversely, when you bend backward, the facet joints close together, creating a more stable and compressed position.
• Sidebending:
  • During sidebending, the facet joints on the side you are bending towards close, while the facet joints on the opposite side open.
• Rotation:
  • During rotation, the facet joints on the ipsilateral side compress together, while the facet joints on the opposite side tend to open.

Joint movements (arthrokinematics)

• Flexion
  • The inferior facet of the vertebra above slides upward and forward relative to the superior facet of the vertebra below
• Extension * The superior facets glide downward and backward, while the inferior facets, the lower articular processes, move upward and forward. posteriorly
• Lateral bending

  • Right lateral bending

    • The left (contralateral) facet joint moves upward and anteriorly to open, while the right (ipsilateral) facet joint moves down and posteriorly to close.
    • Causing facet closure on right side and opening on left side

  • Left lateral bending

    • The left (contralateral) facet joint moves upward and anteriorly to open, while the right (ipsilateral) facet joint moves down and posteriorly to close.
      • Causing facet closure on left side and opening on right side
• Cervical rotation

  • Right rotation

    • The left facet joint of the upper vertebra moves anteriorly (forward) while the right facet joint moves posteriorly (backward).
      • At the same time, the intervertebral foramen on the right side (ipsilateral side of the rotation) closes, and the foramen on the left side (contralateral side) opens.

  • Left rotation

    • The right facet joint of the upper vertebra moves anteriorly (forward) while the left facet joint moves posteriorly (backward).
      • At the same time, the intervertebral foramen on the left side (ipsilateral side of the rotation) closes, and the foramen on the right side (contralateral side) opens.

Coupled movements

• Cervical spine
  • C1: lateral bending and rotation occur in different directions (occurs if spine in neutral, flexion, and extension)
  • C2-C7: lateral bending and rotation occurring in the same direction (occurs if spine in neutral, flexion, and extension)
• Lumbar/thoracic spine
  • If spine in flexion: side bending and rotation will occurring in same direction
  • If spine in extension/neutral: side bending and rotation will occur in opposite directions
• Lumbopelvic joint
  • When in flexion: lumbar spine flexes followed by pelvis rotation anteriorly, ending with hip flexion
  • When in extension (when coming from flexed position): hips extend followed by pelvis rotating posteriorly, and spine extending
• Sacroiliac joint
  • Nutation: flexion of sacrum causes posterior tilt of ilium (in frontal plane)
  • Counternutation: extension of sacrum causes anterior tilt of ilium (in frontal plane)
  • Anterior innominate: anterior superior iliac spine (ASIS) moves downward (in sagittal plane)
  • Posterior innominate: anterior superior iliac spine (ASIS) moves upward (in sagittal plane)