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Fig 1. Top-to-bottom view of the intervertebral disc with an annular tear. Nucleus pulposis is the central portion and the annulus fibrosus is the outer
The intervertebral disc is a cartilaginous structure that separates the vertebral bodies and serves the function as a shock absorber and a spacer. The outer portion of the disc is a tough fibrous structure known as the annulus fibrosus. The annulus connects the two vertebrae together and helps contain the more gelatinous center of the disc, the nucleus pulposus. The nucleus is hydrated with water and serves to absorb shock through the spine (figure2).
Fig 2. Forces through the disc are distributed from the gelatinous nucleus to the outer tough annulus as well as the cartilaginous endplate of the vertebrae
Just like other cartilage structures the disc is prone to injury. If the annulus tears and no inner disc material ruptures we call this an annular tear. Because the outer 1/3 of the disc has a rich supply of pain receptors this can lead to back pain. In time the injured fibers heal with scar tissue and symptoms subside. Unfortunately, this tissue has a very low blood supply making the healing process last several months in most cases. The injured disc may also be prone to eventual rupture or early degeneration.
Most annular tears are the result of the natural aging process and are the result of wear and tear. In almost all cases the major factor influencing these injuries are multifactorial. These factors include genetic disposition, healthy habits including diet, exercise and alcohol and tobacco use, repetitive activities, core strength, posture and ergonomics as well as acute injuries. Injuries often consist of a twist or torsion of the spine with or without a significant axial load.
Symptoms are predominately low back pain that is located in the middle of the back that may radiate across the back. Leg pain may be present but is less common unless a disc bulge or herniation is also present. Inflammation around the injury site may irritate the nerves, but this often is transient. Positions that add pressure to the disc such as sitting with a slouched posture tend to aggravate the symptoms. Other activities such as coughing, sneezing or lifting cause a transient increase in the pressure inside the disc that may also aggravate the back pain associated with annular tears.
After physical assessment special tests may be ordered to identify the injury. An MRI is often used to visualize the soft tissues of the spine, including the disc. Annular tears present as what is known as a high intensity zone, or area of white in the region that is typically black in the outer portion of the disc (figure 3). In some rare cases discography may be used to verify the disc as the painful structure. This test is purely diagnostic and not therapeutic. A saline mixture with x-ray dye is injected into the disc with a pressure reading. If this procedure reproduces back pain then verification of the disc as the pain generator is made.
Fig 3. Axial lumbar MRI showing a high intensity zone (arrow) in the back of the disc. This represents an annular tear with tissue injury.
In most instances a focused course of physical therapy along with anti-inflammatory medication, limited rest, limiting impact activities and activity modifications is sufficient to allow the disc to heal. This injury may take several months to heal. During that time the aim is to set the environment for healing while minimizing aggravating activities. It is important to stay active during this phase and to identify activities that both alleviate and aggravate the symptoms to allow for optimizing the healing process. Surgery is rarely needed for these injuries and conservative care is the mainstay of treatment.
For More information on Dr. Perry, visit https://www.vailortho.com/doctors/James-Perry
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