kin191 a.ch.10. lumbar. thoracic. anatomy

KIN 191AAdvanced Assessment of Lower Extremity Injuries

THE THORACIC AND LUMBAR SPINEANATOMY

INTRODUCTION

• BONY ANATOMY• ARTICULATIONS• LIGAMENTOUS ANATOMY• MUSCULAR ANATOMY• NEUROANATOMY

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• Cervical spine (7)– Greatest ROM– Spinal cord is the most vulnerable

• Thoracic spine (12)– Greatest protection of the spinal cord expense

of ROM because of large spinous process• Lumbar spine (5)– An equal balance between protection of the spinal

cord and available ROM• Sacrum (5) and coccyx (3~4)– Composed of fused bone– To affix the spinal column to the pelvis– Serve as a site for muscle attachment

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Spinal Column

• The segments of the mobile spinal column

• Cervical (n=7), thoracic (n=12), and lumbar (n=5) vertebrae

• Discs: 23

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Bony Anatomy (Lumbar)

• Total of 5 lumbar vertebrae• Components– Vertebral body– Transverse processes– Spinous process – Neural arch– Pedicle – Lamina

– Pars interarticularis– Intervertebral

foramen– Facet joints (superior

and inferior)

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Vertebral Body

Transverse Processes

Inferior Articular Facets

Spinous Process

Superior Articular Process

Lamina

Pedicle

• Vertebral body– Primary weight-bearing structure of

spine• Transverse processes– Attachment site for ligaments/muscles– Long for leverage/increasing

mechanical advantage• Spinous process– Attachment site for ligaments/muscles– Posterior projection (no inferior slant)

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• The Neural Arch– Formed by the pedicle and

lamina on each side• Pedicle – vertebral body to

transverse process• Lamina – transverse process to

spinous process

– Serves as the protective tunnel through which the spinal cord passes

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Pedicle

Lamina

• Pars Interarticularis– Between the superior and inferior

facets of the vertebra– A common site of stress fractures

in lumbar spine

• Intervertebral Foramen– The vertebral notch on the

inferior portion of one pedicle is matched with the vertebral notch on the superior portion of the pedicle below

– Nerve roots existing between the vertebrae

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• Facet joints (superior and inferior)– 2 sets for each vertebrae – articulation between

vertebral segments– Lumbar facet orientations• L1-L3 – sagittal plane• L4-L5 – frontal plane

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Intervertebral Disc• Dual purposes– Shock absorption (longitudinal and rotational)– Increase available ROM

• Components– Annulus (ring) fibrosus – tough/dense outer layer– Nucleus (cell)pulposus – flexible inner layer– “Jelly doughnut”

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• 23 intervertebral discs are found along the spinal column

• No disc between– C0-C1 (the skull and the first cervical vertebrae)– C1-C2

• Individual disc are referenced by the vertebrae between which they are found– The disc located between the fourth and fifth

lumbar vertebrae is known as the L4-L5 intervertebral disc

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• Permanent dehydration– Occurs through the aging process– Until the age of approximately 40 years, the

disc is fully hydrated after this age dehydration begins

– By age 60 years, the disc have reached their maximum state of dehydration• Decreasing ROM • A slight narrowing of the intervertebral foramen

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Nucleus Pulposus

• Elastic/gelatinous substance – 60-70 % of H20 content

• Deformable but resistant to compression• Affects of bipedal ambulation and aging

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Bony Anatomy (Thoracic)• Vertebral bodies– Smaller in thickness and diameter than lumbar

vertebral bodies

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• Spinous processes– Project inferiorly to limit extension ROM– Continue to serve as muscular and ligamentous

attachment sites

• Transverse processes– Thicker to allow for formation of costotransverse

joints on ribs 1-10– Ribs 11-12 are “floating” so no articulation with

transverse processes

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• Costovertebral joints– Articulation between each rib and thoracic spine

vertebral bodies– For T1 and T10-12, articulation with 1 rib on each

side (1 facet in middle)– For T2-T9, articulation with 2 ribs on each side at

inferior and superior costal facets

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• Ribs– True ribs (1-7) articulate with sternum through

own costal cartilages– False ribs (8-10) articulate with sternum through

conjoined costal cartilage– Floating ribs (11-12) have no anterior articulation

• Sternum– Manubrium (superior)– Body– Xiphoid process (inferiorly)

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ARTICULATIONS

• Synovial joints (joint capsule)– Superior and inferior facet joints

• Cartilaginous joints– Intervertebral disc and superior/inferior vertebral

bodies• Each segment has relatively little individual

mobility, but in combination allow for significant trunk/spine ROM

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Ligamentous Anatomy

• Anterior longitudinal ligament– Broad/thick, attaches to anterior aspect of

vertebral bodies and intervertebral discs– Limits spine extension (thinnest in lumbar area)

• Posterior longitudinal ligament– Thins distally, lines anterior portion of vertebral

foramen, limited intervertebral disc attachment– Limits spine flexion

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Ligamentous Anatomy

• Supraspinous ligament– Attaches tips of spinous processes together

• Interspinous ligaments– Fills space between adjacent spinous processes– Limit spine flexion and rotation

• Ligamentum flavum– Connect laminae of adjacent vertebrae– Reinforces facet joints

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A: Ligamentum flavum

B: Interspinous ligament

C: Supraspinous ligament

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MUSCULAR ANATOMY

• Extrinsic muscles– Rectus abdominus• Responsible primarily for trunk flexion

– Internal/external obliques (pocket muscle)• Responsible for lateral bending and/or spine rotation

– Transverse abdominus• Trunk stabilization

– Latissimus dorsi• Trunk stabilization via thoracolumbar fascia

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Abdominal Muscles

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• Intrinsic muscles– Quadratus lumborum – pelvis to transverse

processes– Erector spinae muscles (lumborum categorization)

– pelvis/sacrum and spinous processes to transverse processes)• Iliocostalis – most lateral

– Lumborum/Thoracis/Cervicis• Longissimus – intermediate

– Thoracis/Cervicis/Capitis• Spinalis – medial

– Thoracis/Cervicis/Capitis

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– Transversospinal muscles – transverse process to spinous process• Multifidus • Rotatores • Semispinalis

– Thracis/Cervicis/Capitis

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Muscular Anatomy

• Extrinsic muscles – indirect effect on spinal column– Latissimus dorsi• Spine extension and stabilization via fascia

– Rhomboid major and minor• Stabilization of thoracic spine and scapular adduction

– Trapezius (middle and lower fibers)• Stabilization of thoracic spine

• Will be covered in KIN 191B33

NEUROANATOMY

• Lumbar plexus• Sacral plexus

• Nerve roots named for spinal segment superior to corresponding nerve root level– L4 nerve root exits spinal column below 4th lumbar

vertebrae

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Lumbar Plexus

• Primarily arises from L2, L3, L4 nerve roots• Posterior (dorsal) branches combine to form

femoral nerve– Femoral nerve – posterior division of L2-L4

• Anterior (ventral) branches combine to form obturator nerve– Obturator nerve – anterior division of L2-L4

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Lumbar Plexus

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Sacral Plexus

• Primarily arises from anterior branches of L4 and L5 as well as S1 through S3

• Anterior (ventral) branches of L4-S3 combine to form tibial nerve– Tibial nerve – anterior division of L4-S3

• Posterior (dorsal) branches of L4-S2 combine to form common peroneal nerve– Common peroneal nerve – posterior division of

L4-S2

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Sacral Plexus

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Sacral Plexus

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