Biomechanics

Question 1

What are the 6 types of thoracolumbar motion possible?

Answer 1

• Dorso ventral flexion and extension (F/E)
• Lateral flexion (LF)
• Axial Rotation (Rot)
• Transverse shearing
• Vertical shearing
• Longitudinal compression and traction (decompression) of
the axial skeleton

Question 2

Describe the lumbosacral Motion unit

Answer 2

Lots more flexion and extention than lateral flexion n rotation

Anatomical features providing for a larger flexion-extension ROM:
• Angular divergence of dorsal spinous processes
• Less developed interspinous and supraspinous ligaments.
• Predominantly sagittal orientation of facets, with relatively small joint surfaces.
• Decreased diameter and increased thickness of interverteral disc.

• Anatomical features limiting lateral flexion and axial rotation ROM:
• Sagittally oriented facets with small joint surfaces.
• Facet joint with small degree of interlocking.
• In the horse, the presence of intertransverse joints.

Question 3

Lumbar motion:

Typical movement of lumbar spine

Answer 3

• Primary motion is flexion with less extension
• limited axial rotation- only possible with coupled flexion

Limited LF, its only possible with flexion and axial rot.

ROM: Flexion and extension is greater or even than lateral flexion and rotation.
• Anatomical features limiting flexion and extension:
• Width and height of dorsal spinous processes.
• Short interspinous ligaments.
• Lack of elasticity of supraspinous ligament.
• Strong ventral longitudinal ligament limits extension.
• Anatomical features limiting lateral flexion and axial rotation:
• Sagittaly oriented interlocking facets.
• Presence of lateral intertransverse joints, and their common ankylosis.

Question 4

Biomechanics of the Thoracic Spine:
Canine Morphology.

2 areas of thoracics of differing biomechanics. Describe biomechanics of T11-T13

Answer 4

T2-T10 Craniail Thoracics
T11-T13 caudal thoracics

T11 change of direction and facet alignment area very mobile, and prone to get painful and irritated. Quite hyper mobile so better of adjusting above and below?

Flexion and extension and increasing Lateral flexion and axial rotation compared to the lumbar vertebra
Anatomical features limiting flexion and extension:
• Width and height of dorsal spinous processes.
• Short interspinous ligaments.
• Lack of elasticity of supraspinous ligament.
• Strong ventral longitudinal ligament limits extension. Anatomical features limiting lateral flexion and axial rotation:
• Predominant sagittal orientation of facet joints

Question 5

T2-T10

What are the major movements assosiated and why ie thinking about their anatomy?

Answer 5

Flexion: vertebral slide in a 45 deg angle
anatomical features limit flexion and extention because of coronally orientated facets

Increasing LF and axial rotation as coupled motion
Movement restricted by ribs and scapula

Anatomical features lateral flexion and axial rotation

• coronal shape and orientation of facets
• short dorsal spinous processess
• thin ventral longitudinal ligament

Question 6

Biomechanics of the Thoracic Spine:
Equine morphology

There are 3 regions of differing biomechanics due to differing form and function

Answer 6

T2-T12- cranial thoracics
T13-T15, Transition region
T16- T18, Caudal thoracics (including the anticlinal)

Over 3 segments we go from sagitall to coronal facet orientated joints.

Question 7

First talk about the Caudal Thoracics T16-T18
Their ROM
and anatomical features

Answer 7

ROM: Lateral flexion and axial rotation are equal to, or greater than, flexion and extension.
Anatomical features limiting flexion and extension:
• Width and height of dorsal spinous processes.
• Short interspinous ligaments.
• Strong ventral longitudinal ligament limits extension. Anatomical features limiting lateral flexion and axial rotation:
• Sagittally oriented interlocking facets.
Overall decreased ROM

Question 8

Now talk about the transition region of equine thoracics T13-T15
Their ROM and anatomical features

Answer 8

ROM: Lateral flexion and axial rotation are greater than flexion and extension.
• Increasing ROM of Lateral flexion and rotation as coupled motion.
• Shape and orientation of the facet joints change in this region.
• Asternal ribs (caudal ribs not directly attached to the sternum)
• Short dorsal spinous processes.

Question 9

Now talk about Equine Segmental Thoracic motion
T2-T12
ROM and anatomical features

Answer 9

Cranial
Cranial thoracic region (T2 - T12)
ROM: Lateral flexion and axial rotation are greater than flexion and extension.
• Increasing ROM of lateral flexion and axial rotation as coupled motion.
• Anatomical features limiting flexion and extension:
• Coronal shape and orientation of facets.
• Anatomical features supporting lateral flexion and axial rotation:
• Coronal shape and orientation of facets.
• Thin ventral longitudinal ligament.

Question 10

Cranial thoracic region ie Withers area

area and anatomical features

Answer 10

Cranial thoracic region (withers area)
ROM: Lateral flexion and axial rotation are slightly greater than, or equal to,
flexion and extension.
• Anatomical features limiting flexion and extension:
• Coronally oriented facets with small, flat joint surfaces.
• Long dorsal spinous processes.
• Anatomical features limiting lateral flexion and rotation:
• Sternal ribs.

Question 11

C7 to T1 Transition into C spine

Describe ROM and Anatomical features

Answer 11

ROM: Flexion and extension is greater than lateral flexion and axial rotation.
• Anatomical features supporting increased flexion and extension:
• Flat and oval shaped facet articular surfaces.
• Short dorsal spinous process of T1.
• Weak to non existent interspinous ligament.
• Thick intervertebral disc.
• Anatomical features limiting lateral flexion and axial rotation:
• Sternal ribs
• Scapula

Huge amaount of flexion and extension in this area.

Question 12

Summary of intervertebral motion in Tspine

Answer 12

Form and function of the thoracic spine (Equine)
Three regions of differing biomechanics.
T2 - T12, cranial thoracics: Increased spinal stability associated with the ribs and rib cage.
T13, T14, T15, Transition region: region of the most coupled motion in the thoracolumbar spine.
T16 - T18 (caudal thoracics): motion similar to the lumbar spine
© International Academy of Veterinary Chiropractic 2019
73
Thoracolumbar
Module
Segmental Biomechanics
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Restricting and restraining the position and movement of the head and neck alters the movement of the back and stride characteristics.
With the head and neck in a high position, stride length as well as flexion and extension of the caudal back were significantly reduced.
Head and neck position influenced the movements of the back, especially in walk.
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General Intervertebral Motion: Summary
Form and function of the thoracic spine (Canine)
Two regions of differing biomechanics.
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T1 - T12, cranial thoracics: Increased spinal stability associated with the ribs and rib cage, ribcage.
T11 - T13: Motion similar to the lumbar spine.
T10: area of most coupled motion in the thoracolumbar spine.

Question 13

The Cog and Wheel Model:

Answer 13

Front and Hind End Centers of motion Chest should raise up and flex and hind should flex underneath them for their core to be properly engaged.

Question 14

Describe what engagement is and why it is important ie bow and string model

Answer 14

Engagement = Initiation of movement, active hindquarters
• Effective engagement is the basis for energy efficient movement.
• Very few animals engage well.
• 100% Efficiency = Treatment and trainings goal.
• Example: If a patient is at 50% efficiency, getting them to 75% helps them conserve energy and improve movement patterns => less “wear and tear”.

Question 15

What muscles are apart of the thoracic sling

Answer 15

Trapezius, serratus, subclavius, pectoralis, trapezius,

Question 16

What are some key characteristics of the front motion centre

Answer 16

Front Motion Center
Shoulder sling = Trunk suspension, stabilization, shock absorption, as well as braking and steering (together with neck).
• No clavicles/Collar bone.
• Muscle sling contraction is important for self-carriage ->
Contraction lifts the trunk and withers between scapulae.
• With training muscles get stronger = compared to growth
• Persistent elevation allows the horse to position and keep it‘s hind legs under the center of gravity (motion more pronounced and uphill) (Clayton).
• Steps of the forehand occur mostly as a result of the active movements of the hindquarters (Engagement).
• The horse primarily “catapults“ over the fixed leg of the
forehand.

This is so critical for shock absorption, ie horses that dont want to jump often have V tight sling muscles, so there is no shock absorption left, so they dont want to come down hard on their front end.

Question 17

Bow and string model:

What is thedsouble bow, dorsal string and ventral string?

Answer 17

Double Bow: Vertebrae, common ligaments of the spine, intrinsic muscles of the spine.
Dorsal String: Dorsal Spinal Musculature (Epaxial).
Extended dorsal parts additionally: Nuchal lig. and supraspinal lig. Splenius m., Erector spinae m. , hip extensors.
Ventral String: Ventral hypaxial muscles (longus capitus, longus colli, psoas, abdominal muscles).
Extended ventral parts additionally: ventral cervical flexors pectoralis and serratus, hip joint flexors.

Question 18

What are the effects of the rider on the horse?

Answer 18

Strong influence on balance and coordination of the horse
A slight shift in the position of the riders weight means the horse needs to rebalance slightly
If the horse is required to constantly shift its balance to compensate for the rider, it will be more difficult to move efficiently and with freedom.
• Tension in the rider is directly transferred to the horse, tensing up in the same area.