Joint Biomechanics - Trunk Flashcards
Skeleton of the Trunk
Vertebral column is a complex structure that demands mobility and stability of the trunk and the extremities, as well and providing protection for the spinal cord.
Vertebrae of the Trunk
33 in total. Cervical spine: 7 Thoracic spine: 12 Lumbar spine: 5 - Mobile part Sacrum: 5 Coccyx: 3-4 - Immobile part \+ Sternum and ribs
What is the normal curvature of the trunk?
- Cervical lordosis
- Thoracic kyphosis
- Lumbar lordosis
- Sacral kyphosis
What is the function of the spine?
- Skeleton of the trunk
- Supports the body and participated in the thoracic and pelvic cavity
- Provides attachments for the ribs and strong muscles
- Protects thoracic and pelvic viscera
- Protects the spinal cord
- Provides stable mobility
- Protects organs
What is the function of the cervical spine?
- Most mobile region of the spine
- Supports the weight of the head (around 4kg)
- High compressive loading due to strong muscles
- Protects the spinal cord and part of medulla oblongata
- Positions the head in space and adapts the visual fields according to external stimuli.
Cervical Spine - Vertebrae and Joints
Atlas: C1
Axis: C2
Atlanto-occipital joint
Atlanto-axis joint
Intervertebral joint C2-C7 with IVD
Zygapophyseal joint
Joints between two adjacent laminae
Joints between two adjacent transverse processes
Joints between two adjacent spinous processes
Which equilibration process helps stabilize the head?
Must balance the weight of the head on top of a relatively thin and long lever, making it vulnerable to traumatic forces.
The increased development of the spinous process of C7(longer than others) that will serve as a lever for the muscular system. Important muscle attachment site for extensor muscles than help keep the head upright.
Cervical Gravity Line
Corresponds to a line from the center of the tip of the odontoid process that should touch the anterior body of C7.
If the line falls forwards of C7: forward head posture.
Upper Cervical Spine
Atlas C1 has no spinous process or body.
There is a specific movement between the occiput and atlas.
Dens axis of C2 is instead of the vertebral body and permits rotation.
Rotation starts between C1 and C2, no IVD between.
Atlanto-occipital Joint
Paired joints.
Between superior concave articular facets of atlas and convex condyles of the occiput.
No IVD.
Atlanto-occipital Joint - Flexion
Flexion: 10°
During flexion, occipital condyles glide postero-superiorly on the lateral masses of the atlas.
Limited by tension developed in:
- Posterior part of the joint capsules
- Posterior neck muscles (sub-occipitals)
- Posterior A-O membrane
- Ligamentum nuchae
Atlanto-occipital Joint - Extension
Extension: 20°
During extension, the occipital condyles slide anteriorly on the lateral masses of the atlas.
Limited by:
- The approximation of the occiput with the suboccipital muscles (mass of the muscle is in the way).
- The posterior arch of the atlas and axis.
- Tension in anterior A-O membrane and joint capsules.
Which articulation permits the nodding of the head?
Atlanto-occipital joint
Atlanto-occipital Joint - Lateral Flexion
8° on each side: movement of the skull against the atlas (5°) and the axis against C3 (3°).
Slipping of the occipital condyles:
- Ipsilateral side: moves towards the midline
- Contralateral side: moves away form the midline
Limited by:
- Tension in the joint capsule
- Contralateral alar ligament
Atlanto-occipital Joint - Rotation
Secondary to the rotation of the atlas around the dens of the axis. With regards to the lateral masses of the atlas: one occipital condyle moves forward and the other backwards.
We don’t analyze rotation in the joint because there is almost none (2°).
Atlanto-axial Joint
Lateral: Paired joints, between the inferior concave articular facets of the atlas and the superior facets of the axis.
Medial: Unpaired, between the dent of the atlas and the cartilage-covered anterior surface of the transversal atlantis ligament.
Atlanto-axial Joint - Rotation
45°
Rotation starts between C1 and C2, the head and C1 move as a single unit.
The lateral masses of the atlas glide over the articular surface of the axis (one forward, one backwards).
Limited by ligamentous structures: alar ligament.
Atlanto-axial Joint - Flexion/Extension
Flexion: 6-12°, the transverse ligament bends downwards.
Extension: 5-10°, the transverse ligament bends upwards.
Lateral mass of the atlas rolls and slides on the superior articular facet of the axis. - Permitted by the transverse ligament increasing the flexibility of the atlanto-axial joint.
What are the two principal functions of the Intervertebral Disc?
- Separate two vertebral bodies (between C2 and S1), increasing the available motion.
- Transmit load from one vertebral body to the next.
Intervertebral Disc Thickness
Increases from cervical (3mm) to lumbar (9mm).
It is related to both the amount of motion and magnitude of the loads that must be transmitted.
Low weight bearing in cervical compared to high weight bearing in lumbar.
Three main components of IVD
- Nucleus pulposus
- Annulus Fibrosus
- Cartilaginous endplate
Nucleus Pulposus
Gelatinous structure 40-50%.
High water content: deformed under hydrostatic pressure, increasing in response to compressive loading and generates pressure in the annulus fibrosus.
Water content decreases with age (90% to 70%).
Annulus Fibrosus
Allows for the deformation.
15-25 concentric layers (lamellae).
Outer zone: fibrous sheath that possess high tensile strength made of type I collagen fibers. It connect the marginal ridges of two successive vertebrae.
Inner zone: fibrocartilaginous made of type II collagen fibers.
Cartilaginous Endplate (CEP)
Thin layers of hyaline cartilage that bind the disc superiorly and inferiorly separating it from the cancellous bone of the vertebral bodies above and below.
Under compression, the nucleus pulposus presses against the CEP and bony endplates, and it deforms.
Intravertebral Disc - Cervical
2/5 the height of the vertebrae (5mm).
Position of the nucleus polposus within the disc is central.
Oval shaped.
Intervertebral articulations in the cervical spine prevent the IVD from completely filling the vertebral body.
Intravertebral Disc - Thoracic
Disc is 1/4 the height of the vertebrae (7mm).
Position of the nucleus polposus is central.
Heart shaped.
Intravertebral Disc - Lumbar
Disc is 1/3 the height of the vertebrae (10mm)
Position of the nucleus polposus is posterior, because the posterior longitudinal ligament is weaker in lumbar region.
Kidney shaped.
Herniated Disc
Flexion of the spine is most responsible.
Annulus fibrosus is broken, nucleus polposus pops out, compressing the nerves.
Load-dependent fluid shifts in the disc
Nucleus pulposus acts as a hydraulic press.
Sustained pressure reduces height (throughout the day, constant pressure on the IVD will shorten them).
When pressure is released, the height of the disc increases.
Which forces are the IVD subject to?
- Compressive
- Bending
- Shear
- Torsional
Requirements of the IVD
- Must be soft enough to permit spinal motions.
- Must be stiff enough to maintain stability and withstand the large loads.
- Has the ability to absorb and dissipate energy that is generated during these activities.
Variation in Load on Lumbar Spine
25% Laying down 75% Laying on side 100% Standing upright 140% Sitting down 150% Bending over 185% Sitting and bending over 220% Bending over with weight 275% Sitting, bending over with weight
Compressive Force
Sum of force produced by the charge (box) added to muscle force + weight of the upper trunk.
Shear Force
Force applied parallel to a material, as opposed to normal compressive forces which are applied perpendicularly.
In the spine: parallel to vertebral body
Lower force in comparison to compressive force.
Zygapophyseal Joint - Cervical
Flat and oval articular facets in an oblique plane.
- Superior: face upwards and medially
- Inferior: face downwards, forwards and laterally
Zygapophyseal Joint - Thoracic
Thin and less triangular, that project vertically.
- Superior: face backwards and laterally
- Inferior: face forwards and medially
Zygapophyseal Joint - Lumbar
Massive. Superior and inferior facets are oriented almost sagittally.
- Superior: face backwards and medially
- Inferior: face forwards and laterally
Zygapophyseal Joint - Cervical Flexion
25°
Upper vertebral body tilts and slides superiorly on the lower.
Limited by tension developed in:
- The posterior longitudinal ligament
- Zygapophyseal joint capsule
- Ligamentum nuchae
- Posterior vertebral muscles (splenius capitis, erector spinae)
Zygapophyseal Joint - Cervical Extension
85°
Upper vertebral body tilts and slides posteriorly and inferiorly on the lower.
Limited by tension developed in:
- The anterior longitudinal ligament
- Impact of the superior articular process of the lower vertebrae on the transverse process of the upper vertebrae
- Impact of the posterior arches through the ligaments (can compress nerves in intervertebral foramen).
Zygapophyseal Joint - Cervical Lateral Flexion
45° on each side (decreases with age: age 90 - 26°)
The lower articular process on that side glides posteroinferiorly on the superior process of the vertebra below. Accompanied by a slight rotation on the same side.
Limited by:
- Opposition of the articular facets
- Stretching of the contralateral zygapophyseal joint capsule
- Compression of the intervertebral disc
Zygapophyseal Joint - Cervical Rotation
50° in each direction (between C2-C7)(first 45° in C1-C2)
90-95° rotation between the whole cervical spine.
The lower articular process on the opposite side of the vertebrae above move against the superior facets of the lower vertebrae (increase the size of intervertebral foramen).
On same side of rotation, articular facets separate slightly (decrease the size of intervertebral foramen).
Limited by:
- Grinding contact of the opposite side facets
- Tension within both joint capsules
- Torsion of the intervertebral disc
Cervical Spine Rotation - Limitation
Rotation in sub-axial spine occurring only after the movement at C1 - C2 is completed.
Rotation in sub-axial spine is limited by IVD and articular facets.
Rotation at the A-A joint is predominantly limited by ligamentous structures, in particular the contralateral alar ligament.
A patient has pain when rotating his head at the beginning of the movement. What does this suggest?
A problem at the C1-C2 level (beginning of movement).
A patient presents hypermobility of the A-A joint. What does this suggest?
Laxity of the contralateral alar ligament.
Zygapophyseal Joint - Thoracic Flexion
30-40° Inferior articular process of the upper vertebra slide upwards over the superior processes of the lower vertebra. Compression of anterior part of IVD. Limited by: - Thoracic cage - Tension in supra and interspinous ligaments - Ligament flava - Posterior longitudinal ligament
Zygapophyseal Joint - Thoracic Extension
20-30°
Approximate the vertebrae posteriorly.
Limited by:
- Impact of the articular and spinous processes between adjacent vertebra.
- Tension in the anterior longitudinal ligament
Much more limited compared to flexion.
Zygapophyseal Joint - Thoracic Lateral Flexion
20-25°
The articular processes of the two adjacent vertebrae slide relative to each other
- On contralateral side: moving as during flexion (thoracic cage widening)
- On the ipsilateral side: moving as during extension (closing the diaphragm muscle)
Limited by:
- Impact of the articular processes on the side of the movement.
- Tension developed in the ligament flava and intertransverse ligaments of the opposite side.
Zygapophyseal Joint - Thoracic Rotation
35°
Inferior processes of the upper vertebrae slide sideways outside the superior processes of the lower vertebrae. Accompanied by a small degree of lateral flexion.
Rotation of the thoracolumbar region important during walking.
Limited by:
- Tension in the supra and interspinous ligaments and ligament flava.
Zygapophyseal Joint - Lumbar Flexion
Works in close relationship with thoracic spine and hip joint.
35-55°
Inferior articular process of the upper vertebra slide upwards over the superior processes of the lower vertebra.
Limited by:
- Organs
- Back muscles
- Hamstring tension
- Tension in supra and interspinous ligaments
- Ligament flava
- Posterior longitudinal ligament
Zygapophyseal Joint - Lumbar Extension
Follows the thoracic spine extension.
15-35°
Approximate the vertebrae posteriorly.
Limited by:
- Impact of the articular and spinous processes between adjacent vertebra
- Articular capsule
- Tension in the anterior longitudinal ligament
Zygapophyseal Joint - Lumbar Lateral Flexion
20-25°
The articular processes of two adjacent vertebrae slide relative to each other
- Lower articular process glides posteroinferiorly on the superior processes of the vertebra below
- Slight rotation on the same side
Limited by:
- Impact of the articular processes in the side of the movement
- Tension developed in the ligament flava and intertransverse ligaments of the opposite side
- Compression of IVD
- Stretching of the contralateral zygapophyseal joint capsule
- Tension in antagonist muscles
- Limited by floating ribs
Zygapophyseal Joint - Lumbar Rotation
0-7° (able to dissociate rotation at different levels)
Angle between articular facet and sagittal plane increase from cranial to caudal.
Orientation of articular processes limit rotation.
Inferior processes of the upper vertebrae slide sideways inside the superior processes of the lower vertebrae.
Limited by:
- Tension in the supra and interspinous ligaments and ligament flava.
- Articular process of inferior vertebra
Trunk Biomechanics of Walking
Rotation of thoracolumbar part extremely important.
Complex mechanism: occurring in opposite direction in the upper and lower part.
In order to maintain head facing forward, the pectoral girdle rotates in the opposite direction.
- No Rotation in the IVD between T7 and T8 but maximum rotation in opposite direction above T7 and below T8.
L5-S1 Joint
Sacrum tilted forward
- Lumbosacral angle between L5-S1 approximately 60°
Higher possibility of spondylolysis and spondylolisthesis (glide of a vertebra on another) because of:
- Degeneration of IVD
- Trauma
- Excessive mechanical stress
Anterior Pelvic Tilt
- Short-arc anterior rotation of the pelvis
- Extension of the lumbar spine
- Increases the lumbar lordosis
- Increases anterior shear force across the lumbar spine and lumbosacral junction (hip flexors compressed, lumbar muscle tension)
Posterior Pelvic Tilt
- Short-arc posterior rotation of the pelvis
- Flexion of the lumbar spine
- Decreases the lumbar lordosis
Therapeutic approach of stretching hip flexors and back extensors and strengthening of abdominal and hip extensor muscles (Hip flexor tension, Lumbar muscles compressed)
The Functions of the Abdominal Wall Muscles
Important so that we are able to do posterior tilt of the pelvis.
Protect viscera and maintain erect posture (along with bony structures).
Contraction of abdominal muscles:
- Help in expiration
- Raising intra-abdominal pressure (sneezing, coughing, micturating, defecating, lifting and childbirth)
Sacroiliac Joint - Nutation
Relative anterior tilt of the base (top) of the sacrum relative to the ilium (coccyx tilting away from the ischium).
Sacroiliac Joint - Counternutation
Relative posterior tilt of the base of the sacrum relative to the ilium (coccyx tilting towards the ischium).
Which two functions does the sacro-iliac perform?
- Stress relief mechanism within the pelvic ring
- Stable means for load transfer between the axial skeleton and lower limbs
Sacroiliac Joint: Nutation Torque
- gravity from body weight force and hip joint compression force generate a nutation torque at the sacroiliac joint.
- Nutation torque stabilises the sacroiliac joints.
- Muscle contraction creates an active nutation torque across the sacroiliac joints.
Manubriosternal Joint
Secondary cartilaginous joint
The two bones are covered with hyaline cartilage, between which a fibrocartilaginous disc.
7° movement (decreases and fuses with age)
Inhale: angle increases
Exhale: Angle decreases
Movements of the Thoracic Cage
- Vertical, transverse and anteroposterior diameters of the thorax increase during inspiration and decrease during expiration because of movements of the diaphragm, ribs and sternum.
- Ribs and costal cartilage move up and down depending on their length and weather it articulates directly with the sternum or not.
Common Movements at the Ribs
Costovertebral joint: twisting and gliding as the rib is raised or lowered.
Limited by the radiate and intraarticular ligaments
Costotransverse joint: Upper part rotation only, lower part gliding and rotation.
Where does the axis of the rib pass?
Passes along the neck through the costovertebral and costotransverse joints.
Runs backwards and laterally, following the inclination of the transverse processes of the vertebrae.
Changes along with the costotransverse joints.
Costotransverse Joints (1 to 10)
Articular facet on the costal tubercle of the rib. A costal fovea on the transverse process of the corresponding vertebra.
Changes in shape of joint surfaces between upper and lower part.
Joint capsule completely surrounds the joint.
3 Ligaments:
- Lateral costotransverse ligament
- Costotransverse ligament
- Superior costotransverse ligament
Movement of the Upper Ribs 2-5
Pump-handle movement
Increases antero-posterior diameter of thorax
Anterior ends raise with the body of the sternum
The body of the sternum is lifted is lifted upwards and outwards.
Movement of the Lower Ribs 8-10
Bucket-handle movement
Increases in transverse diameter of the thorax
Anterior ends move outward and upward
Widening of the infrasternal angle
Rotation and gliding of one bone against the other
Movement of the Medium Ribs 6-7
Can be pump-handle or bucket-handle depending on every person.
Movement of Floating Ribs 11-12
Little influence on increasing diameter of thorax.
Major role is attachment of the diaphragm and quadratus lumborum.
Movement of the Ribs with the Thoracic Spine
During flexion: ribs move closer to each other (limiting the flexion)
During extension: Ribs move further apart (intercostal muscles in tension)
During lateral bending: Concave side come together and convex side separate
During rotation: Slight horizontal displacement of one rib with respect to the other
Scoliosis
Caused by the lateral displacement and rotation of the vertebral bodies.
Has profound effects on the shape of the thorax, creating a convex and concave side. Shortened muscles on the concave side, lengthened muscles on the convex side.
