Lumbar spine and pelvis

Question 1

Impact that altered spinal curves can have on overall mechanics

Question 2

Form force closure

Answer 2

Form closure:
– when structures have congruent shaped and they are close fitting and they make a congruent shape, where there are not extra forces needed to maintain the stable state of the system during loading and unloading situations
—- the sacrum and ilium each have one flat surface and one rigid surface which interlock together, promoting stability
—- the position of the bones in the SIJ creates a ‘keystone-like’ shape which adds to the stability in the pelvic ring.
—- this keystone shape is created, as the sacrum has a wider side superiorly, which allows the sacrum to be wedged in between the ilium

Force closure:
– stability caused by muscles, ligaments and tendons
—- other forces acting across the joint to create stability. This force is generated by structures with a fibre direction perpendicular to the sacroiliac joint and is adjustable according to the loading situation
—- muscles, ligaments and thoracolumbar fascia all contribute to force closure

Question 3

Force coupling

Answer 3

Pelvis force coupling:

– occurs around the acetabular socket
– looks at the relationship between the anterior and posterior pelvic musculature

Anterior superior pelvic musculature:
– abdominal muscles
Anterior inferior pelvic musculature:
– hip flexors:
—- psoas, iliacus and pectineus
—- rectus femoris

Posterior superior pelvic musculature:
– erector spinae muscles
– quadrates lumborum
– latissimus dorsi can influence it
Posterior inferior pelvic musculature:
– hamstrings

It is the push and pull off the anterior and posterior pelvic muscles that allows rotation of the pelvis, so normal biomechanics and gait can be maintained

If someone is having problems going up and down stairs or just having problems with their centre of gravity in general, you need to look at these structures that influence the rotation of the pelvis

Question 4

Structure and function of intervertebral discs

Answer 4

Nucleus pulposus:
– 77% water
—- water is a non-compressive fluid, allowing a state of ‘preloading’ to occur
—- this allows a greater resistance to compressive force
—- the fluid nature of water allows for resistance to lateral flexion

– 14% proteoglycan
– 4% collagen

Annulus fibrosis:
– 70% water
– 15% collagen
– 5% proteoglycan

—- the layering of the annulus allows tolerance to asymmetrical loading, especially torsion
—- 20 alternating orientation of layers of annulus allows for multiple vectors of movement
—- the annulus fibrosis and nucleus pulposus become a functional couple, and their reliant on each others structural integrity
—- this becomes a mechanism for self-stabilisation

— the semi fluid quality of discs accommodates the variation in angle between vertebrae to accommodate the changes in lordotic and kyphotic curves

Innervation:
– usually has no nerve supply
– apart from the peripheral posterior aspect innvervated by the sinuvertebral nerve.
– lateral aspect- anterior and posterior grey rami

Intervertebral discs make up 20-25% of the total length of the spinal column
– when we get older discs can dehydrate and flatten due to them being filled with water, this is why we shrink as we get older sometimes

The discs separate the vertebrae as part of a functional segmental unit acting in concert with the facet joints.

Allow the spine to be flexible without sacrificing a great deal of strength

Provides cushioning for the vertebrae and reduce the stress on the vertebrae during impact (act as a shock absorber for the spine)

They help protect the nerves that run down the spine

Question 5

Understand the impact altered angulation of pelvis has on spinal mechanics
and curves

Answer 5

Anterior pelvic tilt:
– Anterior tilt will put huge pressure on the lumbar sacral angle and increase the risk of a slippage of the lumbar vertebra in either L5 or S1
– will also caused an increased lumbar lordosis meaning the facets can be approximated causing an increased likelihood of lumbar facet dysfunction and puts more pressure on discs increasing the likelihood of a herniation/prolapse
– can also cause muscular imbalances and have altered movement patterns
– an increased anterior pelvic tilt can be seen in pregnancy during 30 weeks of pregnancy

Posterior pelvic tilt:
– posterior rotation of the inominates
– gives the appearance of a flat back as the lumbar lordosis is reduce and more flattened out
– seen 12-24 weeks of pregnancy
– causes vertebrae to be stacked more on top of each other
—- obviously as the curves of the spine are designed as a whole for weight bearing, the flattening of the lumbar spine will cause decreased shock absorption in the spine putting it under more pressure
—- also the flatter the spine is the more stacked on top of each other they are, and this can put the discs under more pressure

Question 6

Understand the impact of conditions such as Scoliosis and Schuerman’s can
have on spinal mechanics

Answer 6

Scoliosis- developmental problem where the spins twists causing lateral deviation:
- TSP:
— can lead to excessive side bending and rotation affecting the thoracic compliance and rib extension, this meaning it can lead to a reduce breathing mechanics

• LSP:
  — degenerative scoliosis most frequently occurs in the lumbar spine
  —

Schuermans kyphosis:
- Type 1 affects just the thoracic spine
- Type 2 affects both the TSP and LSP

TSP:
– leads to excessive thoracic kyphosis, resulting in reduced rib excursion and thoracic expansion. Which can have an affect on breathing mechanics, reducing it as the thoracic musculature won’t move be able to move as much

LSP:
– increased type 1 Shuermanns increased thoracic kyphosis, an increase TSP kyphosis can have a direct affect on the lumbar spine increasing its lordosis
—- this will approximate the facets, and increase pressure on the discs

– type 2 is endplate changes without significant wedging and leads to a loss of lumbar lordosis, it is often related to trauma and is more likely to be symptomatic

Question 7

Understand the process of spondylosis

Answer 7

Definition:
– spinal degeneration

Structures involved:
– vertebrae, discs, facets, capsules, muscles, and ligaments

Initial phase:
– degeneration of the discs leading to reduced disc height
—- this can increase likelihood of herniation
– this leads too approximation of facets and ligamentous laxity
– resulting in acute episodes of pain and muscles spasms

Middle stage:
– segment instability due to the ligamentous laxity
—- can also occur in pregnancy
– chronic muscle fatigue, hypoxia and micro trauma due to increased stabilising effort from the muscles
– resulting in constant low grade ache

Late stage:
– osteophyte formation around facets and vertebral bodies due to the degeneration occurring due to the approximation of facets etc, this leads to more episodes of acute pain along with constant acute from overuse of paraspinal musculature