2.3 Spinal mechanics & spinal disorders Flashcards
Facet orientations
Thoracic - rotation in coronal plane, limited by ribs
Lumbar - permit F/E in sagittal plane
Lumbosacral - limit movement in sagittal
*sacral facets also prevent sliding forward displacement of L5 (aided by ligaments, muscles, fascial capsules)
Where does flexion in the back usually occur?
- Mainly occurs in lumbar spine - enhanced by lumbar lordosis.
- Hyperflexion stretches sciatic nerve & may cause nerve root pain.
- Flexion causes nucleus to project posteriorly.
Extension of back
- Thoracic spine has minimal movement/retains kyphosis
- Lumbar increases lordosis
- Hyperextension increases stress on facet joints - ‘closes them down’
Lateral flexion & rotation of the back
- Small degree in thoracic spine but is limited by ribs.
- Most occurs in lumbar spine.
When are the back muscles electrically ‘quiet’?
In full flexion.
-dangers of ‘lifting’ in flexed and rotated posture
What is the function of transversospinalis?
- segmental stabiliser of the back
- together with deep abdominal muscles form a ‘corset’ around trunk connecting via lumbar fascia
- strengthened via contraction of deep abdominal muscles (transversus abdominis)
What types of low back pain are there?
- Mechanical type pain - muscle strains, disc prolapse
2. Compressive type pain - typically of nerve root
What happens to deep back muscles following injury?
Pain inhibits muscle contraction, consequently, transversospinalis (TrA) contraction has delayed onset and waste (can be retrained to stabilise lumbar spine).
*diff parts of body are recruited to contract together - integrated movements to facilitate each other’s role, but with injury, there is a significant delay in the contraction of TrA
How do you induce disc prolapse?
- lumbar flexion at 15deg to force nucleus posteriorly
- rotation 15deg produces maximum torsion in annulus where only 50% of the annulus fibres can resist force
- slight LF forces nucleus postero-laterally
- be fat/overweight
- contract trunk muscles
What are the stages of disc prolapse?
Disc prolapse is the penetration of nucleus into (and through) the annulus.
- Bulge
- Herniation
- Extrusion
Prolapse is generally postero-lateral due to PLL.
What do the posterior rami innervate?
- facet joints
- deep back muscles
- overlying skin
What is compressive type pain?
- occurs when nerve roots that leave the spine are irritated/pinched
- common causes: herniated discs, spinal stenosis (anything causing narrowing of bony tube that spinal nerves run in)
Disc prolapse & irritation of nerve roots: what does L5/S1 prolapse result in?
Affects S1 nerve (sciatic n’)
Pain = over hip, postero-lateral thigh, leg & heel. Partial sensory loss in S1 dermatome (back of calf, lateral heel)
Movement = restricted & painful. Weakened plantar flexion (difficulty walking on toes)
Signs = limited straight leg raise, diminished sensation. Wastage of calf muscles lateral foot, diminished or absent ankle reflex.
**L4/L5 also common
Disc & facet joint injury at cervical levels
- Less common than lumbar spine due to structure and loading
- Trauma usually related in F +/- rotation
- May impinge on cord +/- nerve roots in vertebral canal
Whiplash injury = acceleration of head in antero/posterior direction
Facet capsule & articular surfaces, and supporting ligaments are particularly susceptible to injury in hyperextension.
What is spondylosis?
Bones lose water and become less dense with age, hence spondylosis is the resultant overgrowth of bone producing bony spurs (osteophytes) to limit the movement of these bones.
The osteophytes can extend into the foramina, narrowing them (stenosis) and compressing exiting nerve roots.
