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