Michael J. Young, M.D. and Richard T. Holt, MD
Spine Surgery, PSC 210 East Gray Street Suite 601, Louisville, KY 40202
Infections of the spinal column is a very broad topic and includes those diseases that arise spontaneously and those that are secondary to some inciting event. True infections are uncommon, particularly in the industrialized countries of the world.
The estimated annual frequency is 0.037 for disc space infection, 0.037 for bacterial vertebral osteomyelitis and 0.037 epidural abscesses. Post-operative wound infections range from 1% after a simple discectomy to 6-8% after attempted fusion with hardware.
A certain group of people are at risk. These are the smokers, the obese, the malnourished, the immunosuppressed, either from acquired immunodeficiency syndrome or medical treatment for tumors; arthritis; organ transplantation; drug addicts; diabetics; or those who have undergone recent urinary tract instrumentation.
The symptoms vary with the particular disease but constant back pain without a history of trauma is worrisome. Often there is a delay in diagnosis because of the subtle presentation, the failure to appreciate unrelenting pain, and the absence of systemic signs such as temperature elevation.
The laboratory study may be misleading, normal white blood cell counts are common, radiographs often show no abnormalities early in the course of the illness, and even more sensitive diagnostic tests such as bone scans may not become positive for a week. When the diagnosis is suspected, the MRI now seems to be the most reliable early confirmatory test, while elevations of the erythrocyte sedimentation rate are a valuable screening test.
Discitis, or disc space infection, is an inflammatory lesion of the intervertebral disc that occurs in adults but more commonly in children. Its cause has been the subject of debate, although most authors believe it to be infectious. The infection probably begins in one of the continguous end plates, and the disc is infected secondarily. Severe back pain that begins insidiously is characteristic of the disease. Although most children will continue to walk in spite of the pain, young children may refuse to ambulate.
The characteristic finding is extension of the spine and the child's complete refusal to flex the spine. Children with discitis usually are not systemically ill. They rarely have an elevated temperature and their white blood cell count is frequently normal. However the erythrocyte sedimentation rate is usually increased. Lateral radiographs of the spine usually will reveal disc space narrowing with erosion of the vertebral end plates of the contiguous vertebrae. bone scanning may be helpful in localizing a lesion that is difficult to diagnose clinically.
Some bone scans are falsely negative, so the diagnosis of disc space infection should not be excluded simply because the bone scan is normal. Magnetic resonance imaging (MRI) seems to be helpful in identifying a disc space infection. The appropriate treatment of these lesions has been the subject of controversy.
Most authors recommend plaster cast immobilization, a treatment that seems to be effective by itself in many cases. Some authors think that antibiotics also should be given because the condition most likely is an infection of the disc (the organism involved is frequently Staphylococcus aureus). In treating the lesion in children, a biopsy is not usually necessary. A biopsy may be indicated in adolescents or adults, especially if drug abuse is suspected, because of the possibility of organisms other than Staphylococcus aureus being present.
Glossary of Terms
Discitis - Infection of the disc space; an inflammatory lesion of the intervertebral disc that occurs in adults but more commonly in children.
Osteomyelitis - Infection of the bone. Vertebral osteomyelitis means infection of the vertebral bones of the spinal column.
Epidural Abscess - Epidural means space above the dura (covering of the spinal cord and nerve roots). Abscess is the collection of purulent fluid or "pus". Thus, this is an accumulation of purulent fluid around the covering of the spinal cord and nerve roots.
Erythrocyte Sedimentation Rate - Laboratory test measuring rate at which red blood cells settle in a test tube - this can be a measure of inflammation or infection in the body.
Bone Scan - Radiologic study where patient is injected with a radioactive tracer (usually technetium) that is absorbed by the skeleton. Increased activity is seen in arthritis, cancers and infection. A very sensitive test.
MRI (Magnetic Resonance Imaging) - Non-invasive radiological test providing excellent image of soft tissue and bones. Staphylococcus Aureus - Common bacteria in skin infections. The most common bacteria in bone bone infections. Biopsy - Obtaining a small amount of tissue or cells for examination.
Dysuria - Pain with urination.
Photophobia - Extreme sensitivity to bright lights.
Debridements - Removal of infected or dead tissue.
References and Suggested Readings
1. Baker et al: To decompress or not to decompress - Spinal epidural abscess. Clinical Infectious Diseases. 15:28-9, 1992.
2. Frymoyer JW et al: The Adult Spine: Principles and Practice. Raven Press 1991. New York New York. Chapters 38, 39, 71.
3. Green NE: Thoracolumbar Spine: Pediatric Aspects. Orthopaedic Knowledge Update 2, American Academy of Orthopaedic Surgeons. Park Ridge, IL p. 288, 1987.
4. Holt RT and Senter BS: Post-operative spinal infectious spine: State of the Art Reviews. Vol. 6, No. 2, p. 389-394, May, 1992.
5. Massie JB et al: Postoperative posterior spinal wound infections. Clinical Orthopaedics and Related Research. (284) p. 99-108, 1992.
6. Thalgott JS, Arther HB, Sasso RC et al: Postoperative infections with spinal implants: Classification and Analysis: A multicenter study. SPINE, 16:981 1984, 1991.