The Spine

Cervical Spine

Cervical Spine • Purpose • Support head • Shock absorption • Allow large degree of flexibility and ROM • Allow passage of nerves, vasculature, etc

Cervical Spine • CO - occipital • C1 - Atlas • C2 - Axis • C3-6 - general basic structure • C7

Cervical Spine • C1 - no body, disk and spinous process • Allows for free space • Large neutral zone and cord protection • More motion

Cervical Spine • Approximately 50% of flexion/extension or nodding occurs at occiput-C1 • Minimal to no lateral flexion/rotation Occipital condyles

Foramen magnum

Cervical Spine • The Axis (C2) • The dens, or odontoid process – is cradled in the anterior arch of the atlas – is a pivot for the rotation of the atlas

Cervical Spine anterior view

• C1-C2 segment – The primary motion at the C1-C2 joint is rotation

• Account for up to 50% of rotation in the neck and most of the initial ROM

posterior view

Cervical Spine • C2-7 – Facet orientation is roughly 45 degrees in the transverse plane – Allows for motion in all planes – More rotation and lateral flexion than other regions

•45 degrees （ transverse plane) •0 degree (frontal plane)

Cervical Spine 1 2 3 4

5 6 7

• Cervical lordosis C0-C7 averages 40° – Most of the lordosis occurs at the C1-C2 segment

Thoracic Spine

Thoracic Spine

Thoracic Spine • 12 Thoracic vertebrae: T1-T12 • Articulate with ribcage

Thoracic Spine • The vertebral body equals width and depth. • The ratio of disc diameter to height is highest – Decrease tensile forces – Decrease possibility of disc injury

• Posterior aspect becomes thicker and more compressive forces • End-plates become larger (higher compressive forces)

Thoracic Spine • Joints of Thoracic Spine – Costovertebral Joint – Costotransverse Joint

• Flexion and extension limited

Thoracic Spine • Less flexible due to rib articulation • Upper thoracic spine facet orientation – Limits flexion extension – 60 transverse/20 frontal

• Facets are more sagittal in T9-12 to allow flex/ext and rot of spinous process will be toward concavity (lumbar coupling)

• 60 degrees （ transverse plane) • 20 degrees (frontal plane)

Ribcage • Spine, ribs and sternum form a closed, cylindrical cavity • Protects internal organs • Resists displacement • Adds strength and stiffness – Moment of inertia increased to resist rotational motions

Thoracic Spine • Increased stiffness over osteoligamentous spine in four major physiologic directions • Increased axial stability over osteoligamentous spine by 4x • Decreased flexibility in traction over a scoliotic spine

Lumbar Spine

Lumbar Spine

Lumbar Spine • Most load bearing structures in the skeletal system • Largest body/disc, lamina and pedicles short and thick for load bearing

Lumbar Spine • L5 transitional, wedge shape of body and disc – Anterior > posterior. • L5-S1 most flexion extension. • Coupling of motion - right lateral flexion will result in right sidebend and left rotation of vertebral body

Lumbar Spine Motion Segment

D isc L1

Left Side View

L2

L3

Sagittal View L4

L5

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•90 degrees （ transverse plane) •45 degrees (frontal plane)

Lumbar Spine • Lumbar lordosis L1-S1 ranges from 30°–80° 1 2 3 4 5

– The apex of lumbar lordosis L3-L4

Movement of the Spine

Muscles of the Spine • Superficial group – Erector Spinae consists of 3 columns – Extend from the vertebrae to the ribs – Produce extension of the spine

Muscles of the Spine • Deep group – Interspinales, multifidus, rotatores, semispinalis, splenius – Extend from one vertebra to another – Extend and rotate the spine

Several factors influence the loads on the spine • The position of the object • The size, shape, weight, and density • The degree of flexion or rotation of the spine • The rate of motion

Loading of the spine during standing • The line of gravity of passes ventral to the fourth lumbar vertebral body • Forward-bending moment – Counterbalanced by ligament forces and erector spinal muscle – The erector spinae muscles ,the abdominal muscles are often intermittently active

Static loads on the lumbar spine during lifting • The highest loads on the spine are generally produced by external loads • Holding the object close to the body instead of away from it reduces the bending moment the lever arm is minimized

Line of Gravity

Exaggerated spinal curves • Lordosis - exaggerated lumbar curve • Kyphosis - exaggerated thoracic curve • Scoliosis - lateral spinal curvature

Abdominal Muscles • Rectus abdominis • Internal obliques • External obliques

rectus abdominis external obliques

Internal obliques