Intervertebral DiscsStructure, Movement,

and Herniation Mike Pichette, Casey Moran, Kristen Palmer

Disc Layers & Tissue Structure

Annulus Fibrosis

• Concentric fibrocartilage rings

• Fibers oblique and at right angles

• Peripheral vascularity

Nucleus Pulposus

• Gelatinous central core

• Mostly water, the rest is collagen

• Avascular

Symphysis Joints

Thickness varies

No disc C1 and C2, L5/S1 most inferior

http://dmm.biologists.org/content/4/1/31/F1.large.jpg, http://www.spinemd.com/cache/images/Medtronic_disctobone_300_274_80.jpg, http://www.chirogeek.com/Anatomy%20Page/Images/Anatomy%20PG/blood-supply.jpg

Age Related Changes

AF thickens and ↑ load bearing

NP dehydrates, cellular changes

• ↓ Elastin and proteoglycans

• ↑ Collagen

Disc replacement

• Plastic and cobalt-chrome

• Viscoelastic polymer and beaded titanium

http://www.biomedcentral.com/content/figures/1746-6148-10-3-1-l.jpg, http://www.sonsa.org/images/ddd2.jpg, http://cdn.trustedpartner.com/images/library/TheSpineCenter2012/Content/ArtificialDisc300.jpg, http://medcitynews.com/wp-content/uploads/freedom-lumbar-disc-509-x-391.jpg

Vertebral Disc HerniationHerniation:

• Nucleus Pulposus moves out of place and breaks open, pressing into nerve root

Lumbar region most common

• Sciatica (pain from lower back into leg)

Symptoms:

• Dull or sharp pain, muscle spasms or cramping, leg weakness, numbness, tingling

Increased risk:

• Aging, lifestyle choices, poor posture, incorrect/repetitive lifting

Image: http://bhpain.com/yahoo_site_admin/assets/images/disc_herniation.138191338_std.gif

Stages of Disc Herniation

1. Disc Degeneration:

Aging causes NP to weaken

2. Prolapse:

Disc changed position leads to impingement

3. Extrusion: Nucleus Pulposus breaks through annulus fibrosus (no herniation)

4. Sequestered Disc:

Nucleus Pulposus breaks through the annulus fibrosus (HNP)

Miyakoshi et al. Case Study53-year-old Japanese male

Symptoms: sudden onset of incomplete paraplegia after lifting a heavy object

• Motor strength: 0/5 R LE and 0-2/5 L LE

• Sensory loss below level of umbilicus

• Urinary incontinence

MRI results: posterior epidural mass compressing the spinal cord at T9-T10 level

Case Study Cont.Surgical procedures: laminectomy at T9-T10,

facetectomy, removal of mass lesion, and posterior instrumented fusion

Intra-operative diagnosis: posteriorly migrated thoracic disc herniation

Prognosis: resumed to walking without a cane by 4 weeks post surgery

Discussion:

• Only 0.15% to 4% of all symptomatic disc herniations occur in thoracic spine

• Only 5 cases (in 2013) of posteriorly migrated thoracic disc herniation had been reported

• Should be considered for differential diagnoses

ReferencesColorado Comprehensive Spine Institute. (n.d.). Retrieved June 6, 2015, from http://www.coloradospineinstitute.com/subject.php?pn=cond-lumbardisc-3

Kim, I. S., et al. (2008). Posterior epidural migration of thoracic disc fragment. Journal of Korean Neurosurgical Society, 43(5): 239-241. doi: 10.3340/jkns.2008.43.5.239.

Marieb, E. N., & Hoehn, K. ( 2013). Human anatomy and physiology (9th ed). Glenview, IL: Pearson Education, Inc.

Miyakoshi, N. et al. (2013). Posteriorly migrated thoracic disc herniation: a case report. Journal of Medical Case Reports, 7: 41. doi: 10.1186/1752-1947-7-41.

Moore, K. L., Agur, A. M. R., & Dalley, A. F. (2011). Essential clinical anatomy (4th ed.). Baltimore, MD: Lippincott Williams & Wilkins.