Herniated disc, ‘ruptured disc’, ‘prolapsed disc’ or ‘slipped disc’ is a condition in which the disk-like structure present between two adjacent segments of the spine (known as ‘vertebrae’) undergo degeneration and results in protrusion through the foramen or the opening through which the spinal nerves passes (known as ‘inter-vertebral foramen’), causing compression of the nerve root. The condition occurs at various regions in the back, especially the cervical region (neck) and the lumbar region (lower back) (Turek, 1998). Introduction The intervertebral disc is structures that are present between two adjacent vertebrae.
It is composed of two layers, namely an outer fibrous or hard layer (known as ‘annulus fibrous’) and an inner gelatinous or soft layer (known as ‘annulus pulposus’). In the cervical region, six intervertebral discs are present, and 7 vertebrae are present. Any of these could be affected with ruptured disc, resulting in the development of symptoms. The disease more often affects the fourth and the fifth vertebral region. It is also common in the fifth lumbar vertebrae and the first sacral vertebrae (Turek, 1998). Another condition related to herniated disc is ‘Schmorl’s nodes’ or ‘cartilaginous nodes’.
In this condition, the inner gelatinous pulposus of the disc protrudes through a defective opening present in the cartilaginous plate covering the disc (present in the weakest point of the disc). This protrusion results in an abnormal contour of the spine (Turek, 1998). Spondylosis is another condition related to herniated disc and is characterized by degenerative changes in intervertebral disc, the vertebrae and the neighboring structures. Bony outgrowths known as ‘osteophytes’ form in the intervertebral disc, which protrude the neighboring tissues causing the development of several symptoms.
This condition occurs in the cervical region, lumbar region and the lumbo-sacral region (Turek, 1998). Pathophysiology One of the major causes of health problems in the society is associated with the back and the neck. In the US, one of the commonest causes of disability before the age of 45 has been back problems, and slipped disc has been one of the frequent back problems. More than 50 billion dollars is spend every year in the US on managing back problems. About one percent of the population develops chronic back problems.
Every year, more than 50 % of the population has to refer to healthcare professionals for back-related issues (Engstrom, 2004 & Turek, 1998). In the cervical and the lumbar region, the disc is the largest, in order to enable movements of the spine. Ligaments are present in the anterior and the posterior portions of the spine, which hold all the vertebrae together. The intervertebral discs undergo age-related changes. During young age, the discs are yellow in color and elastic in nature. The water content is also high. However, with age the discs change color, become less elastic and lose their water content.
Their main function is to absorb the shock present in the spine and reduce the tension on the vertebrae and the nerves, during walking, running and other body movements. About one-fourth of the length of the spine is formed through the discs. Under normal situations, any damage to the nucleus pulposus does not cause any pain. The pain that arises from a protruded disc usually arises when the spinal nerves are pressed. During movement and injury, the spinal nerves are compressed causing pain and tenderness (Engstrom, 2004). The exact cause for herniation of the disc is not understood clearly.
However, several factors such as age, trauma, repetitive injuries, posture, body weight, etc, have an affect on the development and the progression of the disease. Overweight individuals are at a higher risk of developing lumbar disc herniation (Engstrom, 2004). Both the fibrosus and the pulposis do not have any nerve supply. When the disc material herniates, inflammation and production of certain substances that bring about inflammation may trigger off a relation and result in the development of back pain. the nerve fibers begins to grow into the inside portions of the diseased disc, which could result in the development of pain symptoms.
Besides, the nerve root may also get inflamed and/or compressed resulting in the development of pain symptoms. To some extent demyelination and loss of the axon can also result in the development of pain symptoms (Engstrom, 2004). In a study conducted by Bhardwaj et al (2004), it was demonstrated that although the incidence of herniated disc was very rare amongst twins, genetic factors could play a vital role in the development of the disorder. In this study, the case of herniated lumbar disc occurring in a pair of identical twins was taken.
Recent research suggests that heredity has up to a 60 % role in the development of herniated disc. The collagen present in the matrix of the disc can be affected by genetic factors. Collagen polymorphism is a process by which collagen can be expressed in more than one ways by the genes. Some of this collagen may be susceptible for degeneration, thus increasing the risk for the development of herniated disc (Evans, 2007 & Bhardwaj, 2004). Previous Studies Previous studies have demonstrated that with age, the spine undergoes degeneration. However, the entire process has still not been understood clearly.
One of the main components of the spine that undergoes degeneration is the intervertebral disc. The height of the disc gradually reduces with age and the annulus bulges. The local instability of the spine tends to exaggerate the disc degeneration process. The abdominal and the muscles of the spine play a very important role in stabilizing the spine, and any disturbance to them would result in exaggeration of the disc degeneration process. The joint facets tend to experience higher amounts of load, leading to deposition of calcium on the disc. The herniation appears as bone spurs on a radiograph.
The herniation, formation of bone spurs, enlargement of the facet joint, etc, cause the narrowing of the spinal canal and intervertebral foramen. This tends to impinge upon the spinal nerve root causing the development of symptoms. Anteriorly, the bone spurs tend to impinge upon the nerve and posteriorly the facet joint undergoes hypertrophy, causing impingement of the foramen. Once the height of the intervertebral disc is lost, the vertical dimension of the foramen is also reduced causing impingement on the foramen. These dynamic changes tend to affect the dimensions of the spinal canal, resulting in the development of symptoms.
In a study conducted by Wong et al, it was found that lumbar pain can be represented in several ways, and it may be difficult to pinpoint the source of the pain and the exact location of the lesion. The physician should be really skilled at examining the spinal cord and pinpointing the source of the pain. He/she should have good knowledge of the spine especially with regards to anatomy and physiology of the spine. The physician should also be aware of the several problems and the mechanisms that work in several portions of the spine (Wong et al).
In a study conducted by Tampier et al (2007), it was found that delamination occurs causing damage to the disc. The damage was previously taught to have occurred between the layers of the annulus. The study was performed on 16 pig spines by mounting the segments of the cervical spine and the intervertebral disc and subjecting them to a load of 1472 N with several loading cycles. Then studies were performed through biopsy, X-ray and chemistry. Eight complete herniation and 4 partial herniations were produced. The first layer of the annulus developed damage at first.
Damage occurred layer by layer in the annulus resulting in herniation of the nucleus pulpsosus (Tampier, 2007). Conclusion Herniated disc is a degenerative disorder of the spine and is characterized by the protrusion of the disc material through the intervertebral foramen. This causes compression of the nerve root along with development of symptoms. It can occur at various levels of the spine, but is more common at the neck and the lower back region. Some of the conditions related to herniated disc include Spondylosis and Schmorl’s nodes. Herniated disc is a common health issue in the US.
Slipped disc is one of the most frequent causes of back problems resulting in severe disability to perform normal function. Back problems on the other hand occur in about one percent of the US population. As the cervical and lumbar regions have relatively larger discs, they are a frequent cause for herniated discs. The exact cause for herniated disc is not known, but several factors such as old age, abnormal back postures, trauma, excessive body weight, abnormal movements, etc, may exaggerate the problem. The nerve root may undergo compression and/or inflammation, resulting in the development of the symptoms.
Symptoms can also develop due to demyelination of the nerve and loss of the axon. Studies have demonstrated that to some extent herniated discs can be affected with genetic factors. This is due to the type of collagen, which is expressed by the genes. In the clinics, physicians often find it very difficult to diagnose and treat herniated discs. In each portion of the spine, certain mechanisms operate which the physician should know. Advanced diagnostic tests such as CT scans and MRI scans may be required to determine the protrusion of the disc material.
References:
Alexander, J.T. (1999). “Lumbar Spinal Stenosis: Diagnosis and Treatment Options. ” Jacksonville Medicine, June. http://www. dcmsonline. org/jax-medicine/1999journals/june1999/lumbar. htm Bhardwaj, R. & Midha, R. (2004). “Synchronous Lumbar Disc Herniation in Adult Twins. Case Report. ” The Canadian Journal of Neurological Sciences, 31(4). http://cjns. metapress.
com/app/home/contribution. asp? referrer=parent&backto=issue,22,30;journal,20,55;linkingpublicationresults,1:300307,1 Engstrom et al (2004), Neurobiology of Disease, in: Braunwald, E. , Fauci, A. S. , Kasper, D. L. , Hauser, S. L., Longo, D. L. and Jameson, J. L. (eds) Harrison’s Principles of Internal Medicine, 15th ed, vol. 2, New York: McGraw-Hill. Tampier, C. Et al (2007). “Progressive disc herniation: an investigation of the mechanism using radiologic, histochemical, and microscopic dissection techniques on a porcine model. ” Spine, 32(35), 2869-2874. http://www. ncbi. nlm. nih. gov/pubmed/18246010? ordinalpos=9&itool=EntrezSystem2. PEntrez. Pubmed. Pubmed_ResultsPanel. Pubmed_RVDocSum Turek, S. L. (1998). Orthopaedics: Principles and Their Application, Vol. 2, 4th ed, Philadelphia: Lippincott-Raven.