What is a Disc Tear?
A disc or annular-tear (or fissure) represents a degenerative or traumatic change in an interveterbral disc1. These tears involve separations or breaks in the fibers comprising the annulus fibrosus, or the fibrous outer-most portion of an intervertebral disc. These fibers run radially (outward from the center), transversely (lying across), and concentrically (circularly, progressively more distant from the center), much like the layers of an onion. Together they form layers of fibrous tissue that surround the internal portions of the disc.
A disc tear is distinct from disc degeneration or disc herniation (a slipped disc) 1. When portions of the annulus fibrosus tear, the integrity of the disc becomes compromised; this can cause pathology such as bulging, prolapsed and more which can compress local structures. However, it is not until the tear completely opens a channel for the innermost substance to leave the disc entirely that a herniation has occurred.
Disc tears can result in back pain, which has been estimated to affect between 12-35% of the population in the western world. Tears can be a result of disc degeneration and can result in subsequent herniation7. Tears and disc degeneration can begin to accumulate very early; one study estimates that 20% of teens have mildly degenerated discs. This degeneration increases with age, especially in males. It’s important to note than degeneration does not necessarily imply a pathologic process, or that trauma is a prerequisite1. While trauma can cause tearing, many of these disc tears are merely the result of aging. It is equally important to note that while disc tears may cause pain, they are often asymptomatic.
The spine consists of a column of bones, known as vertebrae, which are stacked atop one another from the pelvis to the base of the skull, protecting the spinal cord6. Intervertebral discs lie in between these vertebrae, connecting the bones together and forming the primary joints of the spine7. These discs support upper-body weight and muscle activity allowing for motion such as bending and flexing. The discs themselves consist of the tough annulus fibrosus which contains a gel-like inner portion called the nucleus pulposus. These intervertebral discs contain few blood vessels, but do have nerves in the outermost layers of the annulus fibrosus.
Disc tears frequently progress into disc degeneration, or spondylosis, most commonly of the lumbar spine5. This degeneration may arise from aging or trauma. With age, the nucleus pulposus comes to resemble the annulus fibrosus and the disc essentially dehydrates and shrinks7. Excessive mechanical loading (compression, bending, twisting strain) can exacerbate this degeneration3. As tears accumulate during this process (or with trauma), nuclear fluid can accumulate toward the edge of the disc causing stimulation of local nerves and pain2. Local pain has been attributed to biochemical waste accumulation, stretching of the outer layers of the annulus fibrosus and the presence of scar tissue, but this is still an area of great controversy7. Pain can also be induced by the compression of nearby nerve roots if disc tearing compromises the integrity of the disk and leads to bulging or protrusions; a condition known as a radiculopathy9. A radiculopathy can cause mild to severe pain in the back, neck, lower and upper extremities, as well numbness and/or weakness in some circumstances. This pain can be very diverse, ranging from a dull ache to a stabbing or pulsing sensation, and typically occurs on one side of the body6.
The disc tears themselves can be divided into four common subtypes:
- With concentric tears (also known as circumferential tears, or delaminations), the broken fibers are parallel with the borders of the intervertebral disc at some distance in between the center and edge1. Tears here create spaces between adjacent concentric fibers which can fill with fluid, such as the nucleus pulposus. These tears often occur with compressive stress on older discs3.
- Radial tears typically result with compromise of disc fibers as they extend from the nucleus toward the edge of the disc (usually posteriorly, and sometimes downward and/or transversely as well) 1. Radial tears are probably part of the aging process and frequently occur without any pain or related symptoms, but are thought to be a necessary condition for future deterioration2. In fact, one study has shown that 35% of discs removed from patients over 40 years of age had a radial tear, and another study has shown detectable disc bulging related to radial tears in younger persons. Radial tears are associated with nuclear degeneration, and the inflammatory reaction it precipitates can be associated with pain even without herniation3, 4.
- A horizontal tear in the disc is called a transverse tear, which are usually small and may represent early stages of age-related disc deformity1. These are often found in conjunction with radial tears.
- Peripheral rim tears3 – more frequent in anterior annulus, associated with bony outgrowths and trauma
Tears are commonly seen as early as 15 years of age3. With growth and increases in stress on a developed, structural defects begin to occur and will typically peak at middle age. These tears are most common in the lumbar spine, and are generally benign as long as they remain small. In fact, these minor disc tears will appear before any degeneration can be visualized with imaging technology8.
Tears can be categorized in grades as follows7:
- Grade 0: no visible tears, normal nucleus
- Grade 1: tears are no more than 1/3 of the distance through the annulus fibrosus and become visible via imaging
- Grade 2: tears extend further toward the disc edge- potentially causing pain as it reaches innervated portions of the annulus fibrosus- but there is no bulging or gross deformity
- Grade 3: the tears have disrupted the entire disc, causing gross disc deformity (i.e. bulge, protrusion) or herniation. Pain may stem from compression of a nearby nerve root or via damage to the innervated portions of the annulus fibrosus
Diagnosis of a disc tear is made via a full history and physical examination by a physician, supported by an array of diagnostic tests. Diagnostic tests are usually reserved only for when pain is unresponsive to conservative treatment and persists longer than 4-6 weeks10.
Tests that may be ordered by a physician may include:
- X-Ray: a spinal x-ray can be used to rule out other possible causes of pain4, 10, 12
- MRI/CT: magnetic resonance imaging (MRI) or computed tomography (CT) scans can allow nerve compression to be visualized4, 10, 12. Disc tears can often be visualized as a high intensity zone (HIZ) using imaging technology such as MRI1. The HIZ is a high intensity signal that is distinct from other portions of the disc7.
- Electrical and nerve conduction tests can be done to isolate effected nerve roots4, 10, 12g
- Discography, or imaging of the disc itself, can be performed by injecting contrast material into a disc or vein and performing a CT/MRI scan to determine abnormalities and assess pain 4, 11, 12
Discography is more sensitive than MRI for detecting radial annular tears, as it easier to visualize the movement of contrast dye into torn spaces than to rely on HIZ’s from MRI, which can indicate other processes2, 4.
The gold standard for diagnosing disc tears and subsequent degeneration and/or herniation involves a technique called provocation discography, in which a physician pressurizes the disc with contrast material to confirm pain in a damaged disc followed by a non-pressuring contrast of the surrounding discs7. This is followed with a CT scan to visualize tears filled with contrast fluid. It is important to note that this technique can actually exacerbate the damage, and an alternative contrast (Gadolinium) has been developed7. This contrast is injected into a vein (instead of a disc), and travels to the vessels of the disc. Using MRI to follow the contrast, flow disruption from scar tissue can be visualized to confirm a tear.
The International Society for the Study of Pain has developed the following guidelines for diagnosing disc degeneration/tears7:
- No visible herniations can be visualized with imaging
- Pain occurs with provocation discography
- Discogram of surrounding discs is painless
- Disc tear must be visualized with imaging
In some cases, a lumbar herniated disc can cause a condition known as Cauda Equina syndrome if it compresses a certain group of nerve roots (the lumbar plexus) in the lower spine. Cauda Equina can cause additional symptoms such as urinary or bowel incontinence, impotence, and/or numbness in the groin area13. This syndrome is considered a surgical emergency, requiring immediate decompression of affected nerve roots.
Injured discs never truly heal to a pre-injury or pre-degenerative state3. A storm of biochemical activity occurs at a site of disc injury, and the healing process results in scar formation instead of new disc tissue. Scar tissue can perpetuate degeneration and irritate local nerve endings in the outer annulus fibrosus of the disc.
Most patients generally improve with conservative treatment7:
- Over the counter anti-inflammatory/pain relievers6, 12, 13 such as aspirin, ibuprofen and naproxen (NSAIDS) can be used for long term pain management and swelling reduction
- Prescription pain relievers6, 12, 13 such as opioids or narcotics can be prescribed for short term use in the event of significant pain
- Physical Therapy6, 12, 13 can help strengthen and stabilize muscles and joints, assist with practicing correct posture, and offer instruction for proper lifting techniques
Most people with herniated discs will not require additional intervention; however injections and/or surgery may be indicated when conservative treatment fails and pain persists6, 10, 12.
- Injections: steroids6, 12, 13 can be injected directly into the affected area to control pain for longer periods of time by reducing inflammation around the nerve; oxygen-ozone7 and other chemonucleolysis agents can be injected into an affected disc to reduce volume and alleviate compression
- Minimally-invasive surgery:
- Annuloplasty7: electro-thermal devices (IDET) are applied to specific areas of the disc to apply heat/cold in such a manner to the annulus of the disc. This is typically used for painful disc tears. The device typically heats up inside the disc cauterizing the painful nerves and sealing a painful disc tear. – many of these procedures have been proven to have good outcomes
- Percutaneous/endoscopic disc decompression7: the use of lasers, radio waves, suction and other manual methods have been used through small incisions to decompress the disc and sometimes seal up tears- many have found good outcomes for these procedures and others believe the outcomes of these procedures are still questionable
- Surgical intervention7, 10: Open cervical/lumbar discectomy is the most common surgical treatment, particularly for lumbar herniations, and has been used and improved for the past 60 years. Part of the damaged disc is surgically removed to alleviate pressure and pain
Intervertebral disc tearing and related disc disorders are a vibrant area of research at present. Glucosamine and Chondroitin, over the counter supplements, are being investigated for beneficial effect to the biochemistry of intervertebral discs7. Outcomes have been positive, with results similar to annuloplasty.
Direct injection of disc growth factors to stimulate repair is being investigated, but is proving to be largely unsuccessful7. This has spawned interest in gene therapy in order to stimulate disc cells to secrete these chemicals on their own, but any results from this research lie distantly on the horizon.
Additional research is being done with the objective of augmenting the disc to counter any degeneration and maintain its non-pathological form7. This has involved the injection of bonding agents to fill gaps and maintain disc size.
Finally, investigations into the efficacy of entire disc implantations and replacements are underway, and are looking very positive. Disc implantation, in which injured or degenerated disc material is removed and replaced by an artificial device, is currently being used in Europe but is still in trial stages for use in the United States7.
1 Fardon, D.; Milette, P. Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology. Spine. Vol 26, E93-E113. 2001.
2 Milette, P. The Proper Terminology for Reporting Lumbar Intervertebral Disc Disorders. American Journal of Neuroradiology. Vol 18, 1859-1866. 1997.
3 Adams, M.; Roughley, P. What is Intervertebral Disc Degeneration, and What Causes it?. Spine. Vol 31, 2151-2161. 2006.
4 Milette, P. Classification, diagnostic imaging, and imaging characterization of a lumbar herniated disc. Radiologic Clinics of North America. Vol 36, 2000.
5 Hull, K.; et al. Lumbar spondylosis. First Consult, MD Consult Web site. Available at: http://www.mdconsult.com.ezproxy2.library.arizona.edu/das/pdxmd/body/234833011-6/1113289864?type=med&eid=9-u1.0-_1_mt_1017197. Posted September 19, 2007. Accessed February 3, 2011.
6 Nidus Information Services 2010: Herniated Disk. Patient Handouts page. MD Consult Web site, Core Collection. Available at http://www.mdconsult.com.ezproxy2.library.arizona.edu/das/patient/body/234155712-5/1108605568/10041/35144.html. Accessed February 3, 2011.
7 Raj, P. Intervertebral Disc: Anatomy-Physiology-Pathophysiology-Treatment. Pain Practice. Vol 8, 18-44. 2008.
8 Sharma, A.; et al. Temporal Association of Annular Tears and Nuclear Degeneration: Lessons from the Pediatric Population. American Journal of Neuroradiology. Vol 30, 1541-1545. 2009.
9 Robinson, J.; Kothari, M. Clinical features and diagnosis of cervical radiculopathy. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2010.
10 North American Spine Society 2009: Lumbar (open) Microscopic Discectomy. Patient Handouts page. Available at http://www.knowyourback.org/Pages/Treatments/SurgicalOptions/LumbarDiscectomy.aspx. Accessed February 3, 2011.
11 North American Spine Society 2006: Discography. Patient Handouts page. Available at www.spine.org/Documents/discography_2006.pdf. Accessed February 3, 2011.
12 Clinical Reference Systems 2010: Herniated Disk. Patient Handouts page. MD Consult Web site, Core Collection. Available at http://www.mdconsult.com.ezproxy2.library.arizona.edu/das/patient/body/234418695-2/1109885219/10068/37519.html. Accessed January 27, 2011.
13 Rihn, J.; et al. Herniated intervertebral disc. First Consult, MD Consult Web site. Available at: http://www.mdconsult.com.ezproxy2.library.arizona.edu/das/pdxmd/body/234418695-2/1108889771?type=med&eid=9-u1.0-_1_mt_1014932. Posted July 29, 2010. Accessed February 3, 2011.