The low back includes a number of important structures that can be related to symptoms of low back pain. The low back supports the body, allows movement, and protects the spinal cord and internal pelvic organs. These structures include the vertebrae, or bony spine, the discs, which lie between the vertebrae, the ligaments around the spine and discs, the spinal cord, and the nerves, which exit the spinal cord to innervate the periphery.
The spine consists of stacked vertebrae, which provide support and at the same time, are mobile. The spinal cord is shielded by the vertebra’s spinous process, a bony prominence. The vertebral body is the portion of a vertebra, which is in front of the spinal cord, and bears the weight of the body. The sacrum is the bone that is located between the buttocks, and the lumber vertebrae are stacked on top the sacrum. Ligaments are strong bands of fibrous connective tissue that attach bones to bones.
In between the vertebrae, the discs cushion the vertebral bodies. The discs minimize impact of stress on the spinal column. The discs have two parts, the central nucleus pulposus and a surrounding annulus fibrosus. A herniated disc occurs when the central portion ruptures through the outer ring. This causes irritation of the nerves adjacent to that segment of disc.
The nerves that exit the spinal cord through the vertebrae stimulate the muscles of the lower extremities and the low back, and send sensory impulses from the lower extremities to the brain.
Types of Low Back Pain
There are a number of types of low back pain. A stretch injury to the tendons, ligaments, or muscles of the low back is considered lumbar strain. This soft-tissue injury can occur due to trauma, improper use, or overuse. Injuries often heal within days or weeks and are referred to as acute, however those injuries lasting longer than three months are chronic. Lumbar strain, which occurs after any event that stresses the lumbar tissues, can range in severity. Treatment is usually rest, analgesic medications, heat, massage, and physical therapy to strengthen the back and abdominal muscles.
Nerve pain and irritation can be caused by impingement on the roots of the nerves as they exit the spinal cord. This is often a result of degenerative damage to the discs. When the central portion of the disc herniates through the outer ring of the disc, it impinges upon the spinal cord or the spinal nerves, causing sciatica, the type of nerve pain, which is exacerbated by movement at the waist, and travels from the buttocks to the lower leg. In severe cases, the nerve damage can be accompanied by loss of bowel and bladder control. Increased pain while lifting the lower extremities is suggestive of the diagnosis. Non-surgical measures, which may help relieve pain and spasms, include epidural steroid injection, physical therapy, ultrasound, exercises, and electrical stimulation.
Conditions that result in growth of the vertebrae or ligamentum flavum growth may limit the space for the spinal cord and nerves in the spinal column. One vertebra may slip on another one, known as spondylolisthesis. Spinal stenosis is compression of the nerve roots or spinal cord by bone spurs in the spinal canal. These types of nerve compression may lead to sciatic nerve pain, which worsens with walking and is relieved by rest. Some non-surgical options are exercises and epidural cortisone injections.
As we age, we experience changes in the composition of the bone and cartilage. Degenerative changes of the discs, which are composed of cartilage, is called spondylosis. Even if the disc does not herniate, localized pain may occur. Osteoarthritis of the facet joints, detected by x-ray, causes lumbar pain in the region, which can be evaluated by x-ray. Normally, degenerative back pain is treated conservatively, using medications to relieve sprain, spasm and inflammation, with heat and rest.
Scoliosis and spina bifida are congenital conditions, which may result in pain. Scoliosis is a curvature of the spine, and may be caused by a spinal abnormality or by a difference in length of the legs. Bracing may help. Spina bifida is a defect in the vertebral arch overlying the spinal canal, and may be accompanied by nerve damage to the nerves that supply the lower part of the body.
Vertebral fractures are an obvious cause of back pain, and in patients with osteoporosis, even minor stress on the vertebrae may lead to fracture and collapse. The onset of severe pain radiates around the waist and increases with body motions. Vertebral fractures will heal after weeks of rest and analgesics however at times, it may be advisable to stabilize the vertebral body with vertebroplasty or kyphoplasty.
Finally, arthritis frequently affects the low back and the sacroiliac joint which connects the base of the spine to the hip joint, often mimicking low back or buttock pain. This can be treated with physical therapy, anti-inflammatories including steroid injections. Should sacroiliac joint injections prove to be temporary in relief, radiofrequency ablation may help prolong relief.