History and Physical Examination

Patients with back pain can be said to have either mechanical or nonmechanical pain.The key distinction is whether there is pain with activity. Many patients with sciatica re- port a sharp pain in the back and a burning pain that radiates down the back of the leg, sometimes as far as the toe, but often terminating behind the knee. Numbness and tingling (paresthesias) are also reported. Postural change may affect the quality of the pain; pain with movement implies disease at the joints of the spine, and pain worsened by sitting implicates the disks. The physical examination of a patient with low back pain should include observing gait, assessing spinal flexibility, testing motor strength (hip to toes), and assessing knee and ankle reflexes.

Patients with spinal stenosis may have neurogenic claudication, or leg pain during activity. This pain is superficially similar to that of vascular claudication. One key distinction between them is that forward bending, which distracts the spine and enlarges the spinal canal, improves the symptoms of neurogenic claudication only. Therefore, a patient with neurogenic claudication may have no pain while riding a bicycle, whereas a patient with vascular claudication will. Another distinction is that vascular claudication appears invariably with activity and is relieved consistently and promptly with rest, neither of which occurs with neurogenic claudication.

Other signs associated with back pain and sciatica include decreased spinal mobility; a positive straight leg raising test; altered sensory, motor, or reflex examination findings; and increased pain with increasing intraabdominal pressure (Valsalva maneuver). Acute pain to palpation suggests a nonorganic cause.

Imaging Studies

MRI is the diagnostic imaging modality of choice for disk disease, although the incidence of disk abnormalities in patients who have no pain is probably 30% or higher.3 MRI, therefore, is not clinically specific. However, it is sensitive. A sagittal view of the entire lumbar spine will clearly show bulges into the spinal canal. Axial views can show encroachment on the nerve root by highlight- ing disk material or osteophytes.

Plain radiographs may show degenerative joint disease of the spine, which is manifest as decreased space between the disks and osteophyte formation. Bone scanning is useful to exclude infection, occult fracture, or tumors; however, multiple myeloma, a blood cell malignancy commonly found in the spine, is not apparent on bone scans. The presence of vertebral compression fractures on radiographs suggests that an osteoporosis workup is indicated.

Laboratory Studies

Back pain is usually not associated with disease processes that can be identified with routine blood screening. If infection, tumor, or an inflammatory cause is suspect- ed, a complete blood cell count and an eryth- rocyte sedimentation rate or C-reactive protein level can be obtained for general screening.