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Biomechanics of Human Spine ENT 214 Biomechanics.

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Presentation on theme: "Biomechanics of Human Spine ENT 214 Biomechanics."— Presentation transcript:

1 Biomechanics of Human Spine ENT 214 Biomechanics

2 Picture retrieved from http://en.wikipedia.org/wiki/Image:Spinal_column_curvature.png

3 Structure of the Spine What is the vertebral column?  a curved stack of 33 vertebrae structurally divided into five regions:  cervical region - 7 vertebrae  thoracic region - 12 vertebrae  lumbar region - 5 vertebrae  sacrum - 5 fused vertebrae  coccyx - 4 fused vertebrae

4 Picture retrieved from http://www.becomehealthynow.com/images/organs/spine/ant_lat.jpg

5 Structure of the Spine What is a motion segment?  two adjacent vertebrae and the associated soft tissues  considered the functional unit of the spine

6 Structure of the Spine Two adjacent vertebrae and the associated tissues comprise the motion segment. Supraspinous ligament Intervertebral joint and facet Spinous process Ligamentum flavum Interspinous ligament Transverse process Anterior longitudinal ligament Cartilaginous end-plate Intervertebral disc Intervertebral foramen with nerve root Posterior Anterior Vertebral canal Posterior longitudinal ligament Vertebral body

7 Structure of the Spine What are the joints between adjacent vertebrae?  intervertebral symphysis joints on the anterior side  two gliding diarthrodial facet joints on the posterior side

8 Structure of the Spine What is the function of the facet joints?  to channel and limit the range of motion in the different regions of the spine  to assist in load bearing, sustaining up to 30% of the compressive load on the spine, particularly when the spine is in hyperextension

9 Structure of the Spine What are the intervertebral discs?  fibrocartilaginous discs that cushion the anterior spinal symphysis joints  composed of a nucleus pulposus (colloidal gel with a high fluid content) surrounded by the annulus fibrosus (a thick, fibrocartilaginous ring that forms the disk exterior)

10 Picture retrieved from http://upload.wikimedia.org/wikipedia/commons/e/e9/ACDF_oblique_annotated_english.png Cervical Vertebra

11 Structure of the Spine What are the primary spinal curves?  the thoracic and sacral curves  concave anteriorly  are present at birth

12 Thoracic Vertebra Picture retrieved from http://upload.wikimedia.org/wikipedia/commons/d/d2/Gray90.png

13 Structure of the Spine What are the secondary spinal curves?  the lumbar and cervical curves  concave posteriorly  develop from supporting the body in an upright position after young children begin to sit and stand

14 Cervical Vertebra Picture retrieved from http://en.wikipedia.org/wiki/Image:Cervical_vertebra_english.png Picture retrieved from http://en.wikipedia.org/w iki/Image:Gray85.png

15 Picture retrieved from http://upload.wikimedia.org/wikipedia/commons/6/62/Gray94.png Lumbar Vertebra Picture retrieved from http://upload.wikimedia.org/wikipedia/commons/b/b2/Gray430.png

16 Structure of the Spine Lordosis - exaggerated lumbar curve Kyphosis - exaggerated thoracic curve Scoliosis - lateral spinal curvature Vertical alignment LordosisKyphosis Scoliosis

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18 Picture retrieved from http://www.childsdoc.org/spring2002/scoliosis2.jpg

19 Movements of the Spine What movements of the spine are allowed?  The movement capabilities of the spine are those of a ball and socket joint, including movement in all three planes and circumduction.  Mechanically:  Annulus fibrous – acts like coiled spring  Nucleus pulposus – acts like ball bearing

20 Movements of the Spine What muscles contribute to flexion of the spine in the cervical region?  rectus capitus anterior  rectus capitis lateralis  longus capitis  longus colli  eight pairs of hyoid muscles

21 Picture retrieved from http://upload.wikimedia.org/ wikipedia/en/6/6f/Rectus_c apitis_anterior_muscle.PN G

22 Movements of the Spine What muscles contribute to flexion of the spine in the abdominal region?  rectus abdominis  internal obliques  external obliques

23 Picture retrieved from http://upload.wikimedia.org/wikipedia/common s/3/32/Illu_trunk_muscles.jpg

24 Movements of the Spine What muscles contribute to extension of the spine in the cervical region?  splenius capitis  splenius cervicis  assisted by:  rectus capitis posterior major and minor  obliquus capitis superior and inferior

25 Picture retrieved from http://upload.wikimedia.org/wikipedia/common s/5/51/Splenius.png

26 Movements of the Spine What muscles contribute to extension of the spine in the thoracic and lumbar regions?  erector spinae - spinalis, longissimus, iliocostalis  semispinalis - capitis, cervicis, thoracis  deep spinal muscles - mulitifidi, rotatores, interspinales, intertransversarii, levatores costarum Picture retrieved from http://upload.wikimedia.org/wikipedia/common s/9/90/Gray389.png

27 Movements of the Spine What muscles contribute to lateral flexion of the cervical spine?  sternocleidomastoid  levator scapulae  scalenus anterion, posterior, & medius  PLUS the cervical flexors and extensors when developing tension unilaterally

28 Picture retrieved from http://upload.wikimedia.org/wikipedia/common s/1/1a/Sternocleidomastoideus.png

29 Movements of the Spine What muscles contribute to lateral flexion of the lumbar spine?  quadratus lumborum  psoas major  PLUS the lumbar flexors and extensors when developing tension unilaterally

30 Picture retrieved from http://upload.wikimedia.org/wikipedia/common s/8/8d/Quadratuslumborum.png

31 Loads on the Spine What forces commonly act on the spine?  body weight  tension in the spinal ligaments  tension in the spinal muscles  any external loads carried in the hands

32 Loads on the Spine In normal standing position, body weight acts anterior to the spine, creating a forward bending load (moment) on the spine.

33 Loads on the Spine Because the spine is curved, body weight, acting vertically, has components of both compression (F c ) and shear (F s ) at most motion segments. FcFc FsFs wt

34 Loads on the Spine During lifting, both compression and anterior shear act on the spine. Tension in the spinal ligaments and muscles contributes to compression. Muscle tension Shear reaction force Compression reaction force Joint center

35 Sample Problem 1 How much tension must be developed by the erector spinae with a moment arm of 6cm from L5-S1 joint center to maintain the body in the position shows on your right? Given that Head : 58 NArms : 81 N Trunk : 328 NBox : 111 N

36 Loads on the Spine Lumbar hyperextension can create a bending load (moment) in the posterior direction. compression tension

37 Loads on the Spine hyperextension Lumbar hyperextension produces compressive loads at the facet joints.

38 Loads on the Spine Spinal rotation generates shear stress in the intervertebral discs. Superior view Lateral view

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40 Human Posture When Lifting

41 Common Injuries  Low back pain  Soft tissue Injuries  Acute fractures  Stress Fracture – spondylolysis (fracture in vertebral neural arch)  Disc herniation


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