Back basics
The low back or lumbar spine is the part of your body between the lower most ribs and the hip bone. It consists of a series of cylindrical structures or vertebral bodies with soft, rubbery discs in between. Tears of the outer fibrous connective tissue of the discs is the initiating injury, weakening the disc and predisposing to slipped, herniated or ruptured discs, usually occurring after improper lifting of heavy objects. The lumbar vertebrae are numbered L1 at the top to L5 at the bottom. Slipped or herniated discs commonly occur between L4 and L5 and L5 and S1 (First sacral vertebra) vertebral bodies. The vertebral body with the pedicles projecting on each side at the back which are connected further back by flat bony arches, or lamina from where the spinous process arise, form the central canal, housing and protecting the spinal cord and nerve roots. (Figure 1). The nerve roots go out of the spinal canal in between pedicles and sends branches to supply nerves to the back muscles and the lower extremities. Therefore, pain resulting from injuries to the disc may be felt at the low back in the upper part of the buttocks, and may radiate to the back parts of the thigh down to the legs below the knee or even down to the foot. This radiation, also known as sciatica, may be felt as pain, tingling or numbness. Coughing or sneezing can elicit back pain with or without sciatica in a patient with disc herniation. There may be muscle spasm of the back muscles resulting in temporary scoliosis or mild lateral curvature of the spine. The main problem may be a tear or bulging of the disc causing pain which may be projected or referred to the low back or lower extremities. In some cases the magnetic resonance imaging, or MRI, of the lumbar spine does not show any bulging of the disc that would implicate mechanical impingement on the nerve root. In these cases it is thought that a chemical reaction due to sensitivity to contents of the disc, irritating the nerve roots, may be present. Thus in acute disc herniation, pain medications, rest for a couple of days and physical therapy is all that is needed as initial treatment. It has been shown that bulging discs would subside during physical therapy or conservative treatment as shown by repeat MRI studies.
Fortunately, most acute back pain result from simple muscular sprains or strains which resolve even without treatment. Epidemiologic studies indicate that more than 80 percent of workers who suffered from an episode of back pain return to work within one month. Low back pain lasting for 12 weeks or more is called chronic back pain.
Lifting of heavy objects, repetitive bending, twisting, or continued standing or leaning may cause low back pain. Workers sometimes identify an event or injury in the workplace as the initial event leading to chronic back pain. Many of these however would show on MRI pre-existing degenerative changes in their lumbar spines. In these cases the injury may have contributed or aggravated the symptoms and it is in this context that workers compensation is settled.
The degenerative process
Disc herniation is just one aspect of the degenerative process in the spine. The discs are the largest structures in the body without blood supply which explains why they undergo degeneration early in life. Roberts and colleagues reported that degenerative changes have been seen as early as two years of age. It is this degeneration and age related changes that cause weakening of the fibrous tissue components of the disc and repetitive compressive forces or injuries may cause tears in the disc which may cause back pain. Other structures which may develop changes secondary to such disc changes are the facet joints. Disc bulges, facet joint arthritic changes and thickening of soft tissues all contribute to narrowing of the spinal canal as well as the foramina thru which spinal nerves exit. Narrowing of the spinal canal and the foraminae are termed stenosis and are usually termed either central or foraminal stenosis.
Like environmental factors, genetics may play a significant role in the causation of back pain. Patients born with congenital narrowing of the spinal canals are prone to developing symptoms of spinal stenosis earlier than the general population. They also have more pain due to disc herniations and have surgery more often.
Patients with lumbar spinal stenosis usually complain of inability to walk or stand for long periods. They develop back and leg pain frequently and have to stop walking or sit up to change position and relieve the pain. The classic symptom is the so-called shopping cart syndrome where patients are comfortable pushing their carts while shopping but couldn’t stand waiting in line at the counter where they have to straighten their backs. These symptoms are due to poor circulation to the nerves due to the narrowing or stenosis of the spinal canal or foramina. The recurrent leg pain and symptoms of these patients is called neurogenic claudication.
Low back pain treatment: What really works
Watchful waiting may initially be tried. Some doctors don’t even prescribe x-ray of the spine because most back pain subside in one month. With acute low back pain, one or two days of rest is recommended. People who strive to be up and about as soon as possible do better than those with little activity. Pain medications, non-steroidal anti-inflammatory drugs and epidural steroid injections may help relieve pain. Active back and abdominal muscle strengthening exercises and physical therapy is effective. Chiropractic treatment or manipulation is popular but its effectiveness is questionable. Pelvic traction, TENS, acupuncture, braces, massage therapy, biofeedback are not effective or have not been evaluated in well controlled trials. Modification of activities, cessation of smoking, and loss of weight are beneficial.
Avoidance of sleeping on the abdomen, use of medium firm mattress, lying on a flat surface with flexion of both hips and knees (the 90/90 rest position), standing and walking after one or two days of rest, swimming, stationary bicycle, and low impact aerobics are recommended.
There have been attempts to compare the outcomes of conservative versus surgical treatment for lumbar disc herniations. The earliest classic study was in 1983 by Weber and colleagues. Their study showed that surgically treated patients did better at one year and had fewer recurrences than the non-surgically treated group at four years. There was however no difference between the two groups at 10 years.
The development or worsening of neurologic symptoms, bladder and bowel movement difficulties indicate the need for urgent surgery. Failure of conservative treatment within 3 to six months is an indication for elective surgery.
Most patients with spinal stenosis do not have neurologic deficits and worsening or increased frequency of neurogenic claudication may indicate the need for surgery. It has been found in studies however that delaying surgery in these patients do not affect favourable outcomes of surgery. In 2000, the Maine Lumbar Spine Study of 148 patients with a 4 year follow up showed that 62 percent of surgically treated patients and 42 percent of the nonsurgical patients were satisfied with their current state at the end of treatment.
Red flags
Although the prognosis of back pain in general is favorable, there are red flags the presence of which may require a more focused approach. These are back pains associated with fever, weight loss, or loss of appetite, especially in older people. Falls resulting in significant back pain in older people may suggest osteoporotic vertebral fracture. Other red flags are urinary and bowel movement problems associated with back pain.
New therapies and methods
Gene therapy to prevent degeneration and inhibition of back pain causing substances to treat sciatica are being evaluated. Total disc and nucleus pulposus replacement systems are being introduced but these methods await long term results to allow their routine use for treatment of low back pain.
With the development of novel surgical or minimally invasive procedures, patients can now have disc surgery done as an outpatient procedure with faster recovery. Some patients even choose disc surgery in lieu of prolonged physical therapy.
