Approach to the Patient with Low Back Pain, Lumbosacral Radiculopathy, and Lumbar Stenosis

Paul B. Nelson

A. Acute low back pain. Back pain is extremely common. Most adults can remember at least one episode of back pain sometime in their lives. Approximately 50% of working adults have back pain at least 1 day per year. Back pain has become one of the most expensive health care problems and has become a leading cause of disability among persons younger than 45 years. The estimated annual cost of medical care of patients with low back pain is more than 8 billion dollars.

B. Lumbar disc disease with sciatica. Patients with back and leg pain (sciatica) most likely have nerve-root compression secondary to rupture of a lumbar disc. Although it occurs occasionally in the pediatric and geriatric age groups, a ruptured disc generally occurs in the third to fifth decades of life. Approximately 90% of cases of rupture of lumbar discs occur between L4-5 and L5-S1; 5% occur at L3-4. The incidence of disc rupture is the same among men and women.

C. Lumbar spinal stenosis is any type of narrowing of the spinal canal, lateral recess, or intervertebral foramina secondary to congenital causes, disc degeneration, bony hypertrophy, ligamentous hypertrophy, or spondylolisthesis. Because it is caused primarily by degenerative change, the disease seldom occurs before the fifth decade of life. The mean age of patients undergoing operative procedures for lumbar stenosis is the sixth decade, although it sometimes occurs in the seventh and eighth decades. Lumbar stenosis is most commonly observed at L4-5 and L3-4.

I. ETIOLOGY

A. Acute low back pain.

Most low back is due to mechanical abnormalities (muscle strain, ligamentous injury, annular tears, etc.). With the disorder being so common and so often mechanical in nature, back pain must be considered a normal part of aging. Degenerative changes in the spine begin in the second decade of life and are extremely common by the fifth decade.

A small percentage of patients have structural abnormalities that account for low back pain. Spondylolisthesis, which is a forward slipping of one vertebral body over another, is caused by defects in the pars interarticularis (spondylolysis) in the younger age group and by degenerative changes in the older age group. Lumbar scoliosis, which is a lateral deformity of the spine, usually is caused by degenerative disease. Primary or metastatic bone tumors or infections of the disc or epidural space are much less common causes of back pain.

B. Lumbar disc disease with sciatica.

A lumbar disc acts as an articulation between the vertebrae and as a cushion. It is composed of a cartilaginous end plate and an outer annulus that surrounds the nucleus. Degenerative changes begin in the disc by the late 20s and are common by the fourth decade. Alterations in the lumbar disc from age alone and major or minor trauma can cause an intervertebral disc to rupture. The disc most commonly ruptures in a posterolateral direction. Disc extrusions and some protrusions can cause nerve-root or, less frequently, cauda equina compression.

C. Lumbar spinal stenosis.

Except in patients born with short pedicles, spinal stenosis is secondary to degenerative changes and many years of repetitive trauma. With age, the disc loses its water content and stops functioning as a cushion. There is increased stress on the bony vertebrae, the ligaments, and the facets. There is increased mobility of the vertebral bodies, ballooning of the disc, and hypertrophy of the ligaments. All these changes can cause narrowing of the lumbar canal. Absolute spinal stenosis is defined as a midsagittal diameter of 10 mm or less. A normal lumbar canal is 15 to 25 mm in diameter.

II. CLINICAL MANIFESTATIONS AND EVALUATION

A. History.

1. Acute low back pain.

The history interview must determine whether the back pain is mechanical or associated with a more serious problem. It must also determine whether there are any “red flags” that suggest more serious causes of the back disorder (Table 23.1). Symptoms and histories that should alert the physician that there may be a disorder more serious than regular mechanical low back pain include night pain, fever, severe back spasms, leg pain, leg weakness, leg numbness, bladder or bowel dysfunction, major trauma, minor trauma in a patient with osteoporosis, weight loss, lethargy, back pain in a child, history of previous bacterial infection, history of carcinoma, history of intravenous drug use, and a worker’s compensation or legal claim.

2. Lumbar disc disease with sciatica.

A patient with sciatica usually has a history of back pain for several days before the development of leg pain. In L4—5 and L5-S1 disc disease, the back pain actually may be somewhat relieved as the patient goes on to have burning discomfort in the buttocks and unilateral pain in the posterolateral aspects of both the upper and lower leg. There may also be numbness or tingling in a portion of the foot or toes. The less common L3-4 disc disease can cause pain in the groin and anterior aspects of the thigh and upper leg. The history occasionally is one of severe sciatic pain from the onset. Bilateral leg pain and bladder or bowel dysfunction suggest cauda equina compression from a large midline disc extrusion.

3. Lumbar spinal stenosis.

In spinal stenosis, the history is more important than the examination. The patient typically reports back and leg discomfort, numbness, or heaviness with standing or walking. Symptoms improve with rest or forward bending. The leg symptoms usually are asymmetric. Occasional patients have true sciatica.

B. Physical examination.

1. Acute low back pain.

Examination of a patient with acute low back pain should begin with inspection and palpation of the low back. Paravertebral muscle spasms may be present. In most cases of mechanical back pain, straight-leg-raise testing causes back pain only. Straight-leg-raise testing that causes back and leg pain suggest root or cauda equina compression. The neurologic examination should include walking on the heels and toes, squatting, and individual testing of the foot and toe dorsiflexors and plantarflexors, the quadriceps, and the iliopsoas muscles. The general examination should include palpation of the abdomen, to rule out an abdominal aortic aneurysm, and a rectal examination.

2. Lumbar disc disease with sciatica.

The patient walks in a slow, deliberate manner with slight forward tilt of the trunk. Paravertebral muscle tightness can cause decreased range of motion of the back, and asymmetric muscle tightness can cause associated scoliosis. The patient prefers to stand or lie rather than sit. The best position usually is lying on the unaffected side with the affected leg slightly bent at the knee and hip. The pain frequently is worsened by Valsalva’s maneuver.

TABLE 23.1 “Red Flags” That Suggest Serious Causes of Low Back Pain

Symptoms, History	Possible Diagnosis
Night pain	Tumor
Fever, history of recent bacterial infection or intravenous drug use, severe back spasms	Diskitis and epidural abscess
Leg pain	Nerve-root compression
Bilateral lower extremity weakness or numbness, bladder or bowel dysfunction	Cauda equina or conus compression
Major trauma	Fracture, dislocation
Minor trauma in a patient with osteoporosis	Compression fracture
History of carcinoma	Metastatic disease
Systemic symptoms such as fever, weight loss	Multiple myeloma
Back pain in a child	Tumor, tethered cord
Worker’s compensation or legal claim	Secondary gain