Intervertebral discs act as cushions between the vertebrae, providing support to the bone structure of the neck and back. Each disc forms a cartilaginous joint to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together.
Discs consist of a strong fibrous outer ring (the annulus fibrosis) that surrounds the inner gelatinous nucleus pulposis. The strong annular fibers contain the nucleus and distribute pressure evenly across the disc. The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's daily activities and keeping the two vertebrae separated. The disc can be likened to a doughnut, whereby the annulus fibrosis is similar to the dough and the nucleus pulposis is the jelly.
Most annular tears are caused by the natural aging process. Since the neck and back are responsible for bearing most of a person’s body weight, they are susceptible to a great deal of wear over time. By the age of 30, most people’s intervertebral discs have begun to degenerate to a certain degree. This degeneration, combined with continuous repetitive activities (e.g. bending, lifting, twisting, sitting) can lead to annular tears since the annulus fibrosus is in a weakened state. Also, traumatic injury can cause an annular tear. This is typically seen in those who participate in high-impact sports such as gymnastics and football and in people with strenuous occupations. Studies also indicate that annular tears may lead to premature degeneration of the disc, endplates, and facet joints.
Figure 1: Annular Tear Viewed on MRI
Patients usually seek the guidance of a primary care physician or back specialist when experiencing pain that may be associated with an annular tear. It is known that the outer 1/3 of the disc’s annular ring is highly innervated with pain fibers. Thus, if a tear involves the outer 1/3 it may be painful. Predominant symptoms in many patients with an annular tear in the low back include back pain in excess of leg pain, and the pain tends to be centered more towards the midline rather than off to one side. Also, pain is often worse when sitting than when standing, and coughing, sneezing, forward bending and lifting tend to aggravate the symptoms.
After a physical assessment, a doctor will typically perform one or more diagnostic tests to localize the likely source(s) of your pain. An MRI or CT scan can be used to visualize an intervertebral disc, but a tear of the annulus may not always be seen. Also, even if an annular tear is confirmed, it may not be causing pain. Occasionally your doctor may suggest a discography to see if the disc is truly the source of your pain. The procedure is performed under x-ray guidance and allows your physician to assess the integrity of the disc and monitor your experience of pain at the same time.
Figure 2: Lumbar Disc with Annular Tear
Figure 3: Lumbar Disc with Annulus Nucleus
Assuming that the patient isn’t experiencing debilitating or rapidly worsening symptoms, treatment for an annular tear will normally begin with a well designed physical therapy program, low-impact exercises, over-the-counter or prescription anti-inflammatories and pain medication, and limited rest. In most cases, the patient will find sufficient pain relief from a combination of these treatments over several weeks. However, if pain persists, a spine specialist may recommend more advanced treatments, including surgery to alleviate the lingering discomfort.