Discs are thick cushions made of cartilage that sit between each vertebra of the spinal column. Discs play a vital role in absorbing the forces that are placed on the spine during movement. Each disc is composed of a strong outer wall of fibres called the annulus. In the middle, is a softer gel-like core called the nucleus. Discs can become weakened and damaged through age or trauma caused by excessive pressure such as heavy lifting. This damage is called “herniation” which is an abnormal protrusion of the soft nucleus into or through the firmer annulus. Disc herniation can occur in four ways:
- Degeneration. The disc becomes weak and thinner and may shrink (typically this occurs with age) but the nucleus does not break through the outer wall of the disc.
- Disc prolapse. The disc has a pronounced bulge that puts pressure on the spinal canal or a nerve.
- Extrusion. The nucleus ruptures through the annulus but remains in one piece.
- Sequestration. The nucleus ruptures through the annulus but is separate from the main portion of the disc.
When a disc herniates, it usually causes pain. If the disc herniation is small, it may cause back pain. If the disc protrusion is larger, it may press into the spinal canal or onto a nerve. If it compresses a nerve, it may cause sciatica which is pain in the lower back and hip radiating down the leg. It generally radiates down the back or side of the leg but it can run down the front of the thigh. The pain may be in one or both legs. It can be associated with severe aching pain in the lower back and buttocks. If the compression is severe, it will cause numbness and tingling and may cause weakness of the muscles in one or both legs. In very severe cases, it can compress multiple nerves and cause urinary or bowel problems. Symptoms can range from mild and intermittent pain through to more serious cases, in which case severe pain, weakness or bladder or bowel control may be impaired or lost.
Most (90%) small disc herniations will heal with some resorption of the herniated disc material or the development of scar tissue. This generally can take anywhere from two weeks to up to 6 months. In 10% of cases, the disc causes severe pain and nerve compression or does not heal and surgery may be required. Conservative treatments such as rest, medication, corticosteroids and physiotherapy are usually tried initially.
Surgery is considered when patients have severe persistent back or leg pain, weakness or numbness of the legs or feet, difficulty walking or standing or bladder or bowel symptoms.
The objective of surgery in lumbar disc herniations is to remove the portion of the herniated disc that is causing the compression. Surgery is performed through a 2cm incision and the portion of the disc removed using special retractors, micro instruments and an operating microscope. Not all of the disc is removed, only the material that is compressing the nerve. Surgery generally takes 1.5 hours and most patients can be discharged home after 1-2 days. Most patients can return to their normal activities after lumbar disc surgery.