Cervical Spine Biomechanics- Lecture

Question 1

Cervical flexion

Answer 1

• Joint surfaces distract somewhat as the inferior articular process glides up and forward on the superior articular process
• Anterior portion of the intervertebral disc is compressed, posterior annular wall is stretched
• Anterior translation of the superior vertebra on the inferior vertebra
• The vertical dimension of the intervertebral foramen increases
• The posterior ligaments and muscles tighten, while the anterior ligaments and muscles are slackened
• Nerve roots are drawn upward and inward in the intervertebral foramen
• The dura is taut, increasing tension in the dura throughout the spinal column

Question 2

Cervical extension

Answer 2

• Inferior articular process glide down and backward on superior articular process - closed packed
• Posterior compression of the intervertebral disc, tensile loading of the anterior intervertebral disc
• Ligamentum flavum and dura relax (dural fold)
• The intervertebral foramen are reduced in vertical height
• Anterior muscles and ligaments tighten, posterior muscle and ligaments relax
• Posterior translation of the vertebra
• The dura relaxes and develops folds
• The nerve roots are relaxed

Question 3

Cervical lateral bending and rotation

Answer 3

• Coupled movement, due in part to facet joint orientation and the uncovertebral joint (Joint of Luschka)
• The contralateral inferior joint surface glides forward and up on the superior articular surface
• The joint surfaces are “opened” and the capsules receive tension
• Capsules on closing side are slackened (side you are rotating to)
• The intervertebral foramen’s vertical dimension increases
• The ipsilateral inferior articular joint surface glides down and back on the superior joint surface
• Joint surfaces are approximated - closed packed
• The anterior-posterior dimensions of the intervertebral foramen diminish
• The neural canal and contents are elongated / stretched on the contralateral side and shortened or compressed on the ipsilateral side

Question 4

Upper cervical spine flexion

Answer 4

• Occiput rolls forward while the occipital condyles glide posteriorly on the atlas
• Slight distraction between the odontoid (dens) and the anterior arch of the atlas
• Slight anterior translation of the atlas
• Posterior tension / anterior slack
• Tension in the spinal canal structures

Question 5

Upper cervical spine extension

Answer 5

• Occiput rolls backwards and condyles glide anteriorly
• Atlas translates posteriorly
• The superior odontoid approximates with the anterior arch of atlas, inferior portion opens
• Anterior structures become taut, posterior structures lax
• Intervertebral foramen narrows

Question 6

Upper cervical spine rotation

Answer 6

• Small amount of ipsilateral rotation and contralateral lateral bending at the O/A motion segment (not an active motion)
• Axis for C1 / C2 rotation is created by odontoid / transverse ligament complex
• Spinal canal volume is reduced
• Vertebral arteries are stressed
• C1 / C2: convex on convex joint surface configuration leads to increased height at neutral and decreased height at the extremes of rotation

Question 7

Upper cervical spine lateral bending

Answer 7

• Lateral bending at O/A and small amount at AA
• Occiput rolls ipsilaterally, condyles glide contralaterally
• Tension develops in the alar ligament on the contralateral side
• C2 rotates ipsilaterally
• Contralateral rotation of occiput on atlas