Intervertebral Discs
Valsalva Maneuver
- involves activation of abdominal muscles while holding ones breath - creates a column of high pressure within the abdominal cavity - stabilizes trunk closer to a neutral position - creates an abdominal brace
Annulus Fibrosus
- made of steardy collagen fibers and elastin protein - arranged in concentric layers for reinforcement
Lumbar Spine Herniation
- most common
Trunk stability with lifting
- obtained though increased intrabdominal pressure through use of valsalva maneuver
Cervical Spine Herniation
- onset between 40-50
Advantage to maneuver
- overall result is increase in compressive loading of the spine and disc
People at greatest risk of disc lesions
- people around 40 or younger --> older people have less water in nucleus; disc less likely to rupture - only 10% require surgery
Most common direction of herniation
- posteriorlateral - anterior herniation is possible though
Pressures Exerted on the Disc
- pre-stressed by ligaments, even in supine
Ligaments of the Spine
- provide intrinsic stability so that it doesn't collapse
Purpose of Hydrophilic gel in the nucleus
- pulls water into disc to return the disc to normal height following compression
Outer Layer of Annulus
- type 1 and type 2 collagen fibers that blend with the anterior and posterior longitudinal ligaments and into the cartilaginous endplates - toward the center; less and less type 1 and more water
Disc Injuries
* Discs do not slip!, they can rupture
How is the spine completely unloaded?
* traction
Most common site of disc problems
- L5-S1 junction
How can PT intervene?
- Manage the way in which people load their spine - encourage overall good health habits
Muscles of the Spine
- add dynamic stability
Pressure to the nucleus pulposus
- allows uniform distribution of pressure throughout the disc - distributes compressive forces in all directions - transforms compressive forces into tensile forces for the annulus to resist
Cervical Disc
- annulus fibrosis is thicker anteriorly - posterior aspect is thinner and resembles a thick ligament with collagen fibers running vertical - no concentric layers of fibers
Bending and twisting with load
- annulus fibrosis more susceptible to damage - repeated twisting and bending can result in tears (horizontal herniation) --> usually posteriorlaterally
Disc Ruptures
- annulus weakens and tears - nucleus can push out, escape, and cause inflammation and pressure on SC, nerve roots, ligaments, and blood vessels
Anterior Column
- bears weight in normal standing
Disc Behavior
- behave elastically when loaded with compression - deform when loaded and return to normal upon removal - subjected to creep with repeated loading throughout the day (person shorter at end of day)
Annulus Fibrosis with posterior pelvic tilt
- bulges slightly anterior - nucleus under pressure from anterior to posterior, but is held in place by annulus
Annulus fibrosis with anterior pelvic tilt
- bulges slightly posterior - nucleus is under pressure from posterior to anterior but doesn't bulge anterior because of the tough fibers holding it in place
Disadvantage to maneuver
- cardiovascular disadvantage - increased abdominal pressure decreases blood flow return to the heart - increases risk of fainting and arrhythmias
Why?
- carries the greatest load - accumulation of stress from transition from lordosis to kyphosis
Fracture to endplate
- causes nucleus pulposus to push up into vertebrae (vertical herniation)
Abdominal Brace
- contraction of transversus abdominis pulls lumbar fascia tight and creates a supportive brace - assisted with contraction of internal obliques
Anterior Pelvic Tilt
- coupled with lumbar extension - deepens lumbar lordosis - causes a slight pinch in the annulus fibrosis posterior
Posterior Pelvic Tilt
- coupled with lumbar flexion - flattens lordosis
Disc Functions
- distribute loads down the spinal column - bears weight - restrains excessive movement between the bodies to avoid injury to the SC - allows some movement
Thoracic Spine Herniation
- doesn't occur as often but can happen
Safer technique
- exhale as you lift
Safer technique
- exhale as you lift to contract abdominal muscles to still create an abdominal brace
With flattened lordosis
- facet joints are pulled apart - posterior spinal ligaments are tight - anterior spinal ligaments are slack
With Increased lumbar lordosis
- facet joints push together - posterior spinal ligaments are on slack - anterior ligaments pulled tight
Prolapsed Disc
- flattened disc - posterior longitudinal ligament bulges out and feels the strain from annulus and nucleus
Nucleus Pulposus
- gel-like substance - 90% water - held in place by hydrophilic proteoglycans - contains some type 2 collagen and elastin - avascular and aneural - 15-16 concentric layers of fibers
Disc response to loads
- good at resisting compressive loads
Cartilaginous Endplate
- hyaline cartilage - attaches disc to adjacent vertebrae above and below the surface - allows for diffusion of water and nutrients to cross from the vascular vertebral body to the avascular disc
Posterior Column
- in normal standing, does not bear weight - when not in neutral position, it does (close packed = extension)
Schmorls Node
- vertical herniation - nucleus pulposus goes into vertebral body - caused from fractured endplates - may or may not be associated with back pain - relatively common
Loading to failure
- when compressive forces exceed the tissue limit, cartilaginous endplate is failed first (can result in fracture)
Unity of the Spine
- when one part moves, other parts move - accomplished via ligaments, muscles, and all other connective tissues of the spine and back
Three Parts
1. Annulus Fibrosus 2. Nucleus Pulposus 3. Cartilaginous Endplates * only outer layer is innervates: disc doesn't sense much pain
