• Curved stack of 33 vertebrate divided into Chapter 9 5 regions
• Cerivcal Region – 7 Biomechanics of the Human Spine • Thoracic Region – 12 • Lumbar Region – 5 • Sacrum – 5 fused • Coccyx – 4 fused
Motion Segment Vertebral Joints
• 2 adjacent vertebrae and the associated soft tissues
• Functional unit of the • Anterior spine – intervertebral symphysis joints • Posterior – Gliding diarthrodial facet joints
Facet Joint Functions Intervertebral Discs
• Channel and limit ROM in the different regions of • Fibrocartilaginous discs that cushion the anterior the spine spinal symphysis joints • Assist in lad bearing, sustaining up to 30% of the • Composed of a nucleus pulposus surrounded by compressive load on the spine the annulus fibrosus – Especially in hyperextension
1 Spinal Curves Spinal Movements
• All three planes • circumduction
• Lordosis – Exaggerated lumbar curve
• Kyphosis – Exaggerated thoracic curve
• Scoliosis – Lateral spinal curvature
Cervical Flexors Abdominal Flexors
• Rectus capitus anterior • Rectus abdominis • Rectus capitis lateralis • Internal obliques • Longus capitis • External obliques • Longus colli
• 8 pairs of hyoid muscles
Cervical Extension Thoracic/Lumbar Extensors
• Erector Spinae • Splenius capitis – Iliocostalis – Longissimus – Spinalis • Splenius cervicis • Semispinalis – Capitis – Cervicis • Assisted by: – Thoracis – Rectus capitis • Deep Spinal Muscles posterior major/minor – Multifidi – Obliques capitis – Rotatores – Interspinales superior/inferior – Intertransversarii – Levatores cotarum
2 Lateral Cervical Flexors Lateral Lumbar Flexors
• Sternocleidomastoid • Quadratus Lumborum
• Levator scapulae • Psoas Major • Scalenus – Anterior • Lumbar – Posterior Flexors/Extensors – Medius – unilaterally • Cervical flexors/extensors – Unilaterally
Forces Acting on the Spine Anatomical Load
• Body Weight • Body weight acts anterior to the spine • Ligament Tension – Causing forward bending • Muscle Tension (moment)
• External loads
Spinal Loading Lifting Loads
• Because the spine is curved, body weight, acting • Compression vertically, has components of both compression (F C) • Anterior Shear and shear (F S) at most motion segments.
3 Lumbar Hyperextension Lumbar Hyperextension
• Produces compressive forces on facet joints
• Supporting up to 30% of force • Bending load (moment) in posterior direction • Anterior Tension • Posterior Compression
Spinal Rotation
• Generates shear stress in the intervertebral discs
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