Introduction
Background
Spondylodiskitis (spondylodiscitis, infectious spondylitis) is an infection that involves 1 or more of the extradural components of the spine. Although it affects a small proportion (2-7%) of all patients with osteomyelitis, it is important because of its potential morbidity and mortality. Infectious spondylitis most commonly appears as spinal osteomyelitis and/or diskitis. Its complications include paraspinal and epidural abscess formation.
Pyogenic spinal infections most commonly are caused by Staphylococcus aureus (in 60% of patients) and Enterobacter species (in 30% of patients). Osteomyelitis caused by Salmonella is most often seen in patients with sickle cell disease. Pseudomonas aeruginosa, Serratia species, and Candida species most often affect patients with a history of intravenous drug abuse. Mycobacterium tuberculosis causes most nonpyogenic spinal infections; however, fungi (eg, Cryptococcus species, Aspergillus species, coccidioidomycosis) also may cause infections.1,2,3,4,5
Related eMedicine topics:
Pott Disease (Tuberculous Spondylitis)
Diskitis
Related Medscape topics:
Specialty Site Radiology
Specialty Site Orthopaedics
Resource Center Spinal Disorders Resource Center
Resource Center Back Pain Resource Center
CME/CE The Many Faces of Ankylosing Spondylitis: Evidence-Based Approach to Diagnosis and Management
Pathophysiology
In spondylodiskitis (spondylodiscitis, infectious spondylitis), the 3 main routes of infection are hematogenous spread, direct inoculation, and contiguous spread.
In adults, most cases of spondylodiskitis result from direct inoculation after spinal instrumentation procedures, including surgery, discography, and epidural injections. Infections that spontaneously result from a hematogenous source (eg, bacteremia, intravenous drug abuse) usually begin in a lumbar or thoracic vertebral body subjacent to the vertebral endplate through seeding of septic emboli via small, penetrating end arteries. Hematogenous spread along the Batson venous plexus is no longer considered a major route of infection.
In adults, infection enters the disk space by means of contiguous involvement and by neovascular proliferation.
Loss of disk height may occur as pyogenic organisms release enzymes that dissolve the nucleus pulposus.
Nonpyogenic organisms, such as those that cause tuberculosis (TB), lack proteolytic enzymes; therefore, they tend to spare the disk. These infections are characterized by large paraspinal lesions that are disproportionate with regard to the amount of local bone destruction. Infection may spread to the psoas muscle and result in paravertebral abscesses that tend to calcify (this is especially characteristic of nonpyogenic infections).
In children, most cases of spondylodiskitis are spontaneous and are related to hematogenously borne infection of the intervertebral disk; infection spreads via residual vascular channels that lead directly into the disk. These channels typically regress by the age of 15 years.
Spread from an adjacent source, such as a psoas abscess (see Image 1), is an uncommon mechanism. CSF and lymphatic spread are also uncommon routes of infection.
Risk factors for spondylodiskitis include age older than 50 years, diabetes, immunosuppression, paraplegia, previous spinal fracture, and urinary tract instrumentation.6
Frequency
United States
Spondylodiskitis (spondylodiscitis, infectious spondylitis) represents approximately 2-7% of all cases of osteomyelitis; the disease is increasing in frequency.
International
Nonpyogenic (ie, granulomatous) infections of the spine occur more frequently in countries where tuberculosis and brucellosis are endemic than in the United States.
Tuberculosis of the spine (ie, Pott disease) is most prevalent during the fifth decade of life. Paraspinal collection and multivertebral infections are more common than pyogenic infections.
Mortality/Morbidity
Symptoms of spondylodiskitis (spondylodiscitis, infectious spondylitis) may be present for months before the diagnosis is confirmed; this may result in progression of the local disease process. Patients may present with hip contracture or paralysis resulting from abscess formation in the paraspinal or epidural spaces.
In the past, acute deterioration from epidural abscess was a rare complication; however, this complication is increasing in frequency among patients with diabetes, as well as among immunosuppressed patients and persons who abuse intravenous drugs.
- Patients with epidural abscess may present with back pain, fever, or neurologic deficit and/or obtundation.
- Less than 2% of patients with epidural infection are children.
- Acute deterioration from epidural abscess may result from mechanical compression of the spinal cord from a mass effect of the phlegmonous tissues or from spinal instability or ischemic compromise.
- Subarachnoid puncture is not recommended in patients with epidural abscess in the region of the abscess; the procedure may be performed remotely.
- The effects of epidural abscess are seen in the thoracic region in 50% of cases, in the cervical region in 25%, and in the lumbosacral region in 35%.
- Surgical decompression and drainage and prolonged antibiotic use are standard treatment methods, although some patients may be treated conservatively, especially if the disease is extensive and involves many levels of the spine.
- The mortality rate from spondylodiskitis may be as high as 30%.
Race
Spondylodiskitis (spondylodiscitis, infectious spondylitis) has no racial predisposition.
Sex
The male-to-female ratio of spondylodiskitis (spondylodiscitis, infectious spondylitis) is 1.5-3:1.
Age
All age groups are susceptible to spondylodiskitis (spondylodiscitis, infectious spondylitis); however, adults older than 50 years are most often affected.
- Patients with a history of intravenous drug abuse or underlying conditions, such as end-stage renal disease, diabetes, and AIDS, present at a relatively young age.
- Childhood spinal infections are a distinct variety of spondylodiskitis that begins within the disk.
Anatomy
In cases of spondylodiskitis (spondylodiscitis, infectious spondylitis) in children, the mechanism of initiation and spread of hematogenous infection to the spine differs from that in adults.
Compared with adults, children have numerous paravertebral and intraosseous collateral arteries; in addition, in children, there is a direct blood supply to the intervertebral disk. These factors are conducive to direct inoculation. By the age of 15, this supplementary system regresses; it is absent in older patients.
Adult hematogenous infections typically begin through segmental arteries (ie, lumbar, intercostal arteries) that feed small, end-artery metaphyseal branches, causing infarction and bacterial seeding. Infection commonly begins in the anterior subchondral regions of the vertebral body because of the relatively rich supply of metaphyseal branches in these structures.
Spondylodiskitis most commonly involves the lumbar (45%), thoracic (35%), and cervical (10-20%) levels. Secondary epidural abscess formation occurs most frequently in the cervical spine, followed in frequency by the thoracic and lumbar spine. Multilevel or multifocal disease also may occur (most commonly with tuberculosis) and accounts for the remaining patients. In 67% of patients, 2 vertebral bodies and the intervening disk are involved.
Presentation
Although the clinical presentation of patients with spondylodiskitis (spondylodiscitis, infectious spondylitis) varies, it generally commences with the insidious development of localized back pain combined with nonspecific symptoms, such as malaise, fever, or weight loss. Fever and leukocytosis often are absent, but the erythrocyte sedimentation rate is elevated in 95% of patients. The C-reactive protein level is commonly elevated.
Patients are predisposed to spondylodiskitis if they have transient bacteremia; intravenous drug abuse; invasive spinal procedures; infection of the genitourinary tract, skin, and/or soft tissue; or infection of the respiratory tract; the etiology remains unknown in 37% of patients. A culture-specific diagnosis is critical for the optimal treatment of the infections. This diagnosis can be obtained by means of surgery or image-guided biopsy.
The virulence of the organism, the overall health of the patient with respect to chronic illness, and the interval before clinical presentation determine the extent of disease at the initial evaluation. Acute illness is usually defined as illness in which the patient presents within 1 week of symptom onset; in cases of chronic illness, patients may present months after the onset of symptoms.
Medical treatment is the first line of therapy for a patient with no neurologic complications. Usually, a 6-week course of culture-specific intravenous antibiotic, with or without an oral antibiotic, is recommended. External spinal immobilization and/or bracing is also recommended. Operative treatment may be required for patients with a neurologic deficit or spinal instability or in cases in which medical therapy has failed.
Preferred Examination
Although plain images, radiographs, CT, or nuclear medicine studies can help establish the diagnosis of spondylodiskitis (spondylodiscitis, infectious spondylitis), MRI is considered the modality of choice for evaluating the presence and severity of spinal infection. MRI is especially effective for evaluating the neural structures of the spine (ie, spinal cord, nerve roots) and extradural soft tissue.
Along with appropriate history taking, physical examination, and positive blood cultures, findings on MRI or radionuclide studies may confirm the diagnosis.
CT is most useful for characterizing vertebral osteomyelitis in patients with subacute or chronic illness. CT provides radiologic guidance for interventional procedures (ie, biopsy, drainage).
Conventional radiographs are insensitive to the acute changes seen in cases of spondylodiskitis, but they may be used on a limited basis in the follow-up of chronically ill patients.7,8,9,10,11,12,13
Limitations of Techniques
MRI is relatively expensive. In addition, it is contraindicated in patients with certain implanted medical devices (eg, pacemakers), and it is not tolerated by all patients because of claustrophobia or morbid obesity. Good MRIs require the cooperation of the patient; the quality of MRI is degraded by motions of the patient. Use of a gadolinium-based intravenous contrast agent is strongly recommended.
Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy.
NSF/NFD has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.
CT is quick and inexpensive, although it exposes the patient to ionizing radiation. In addition, it is associated with a low risk of an allergic reaction to the intravenous contrast agent, though detection of bone destruction or a paraspinal mass does not require the use of contrast material.
Radionuclide studies may be time consuming, and spatial resolution may be low.
With plain radiographs, results are often normal or nonspecific in patients with acute spinal infection.
Differential Diagnoses
[Reiter Syndrome, Musculoskeletal]
Ankylosing Spondylitis
Gout
Rheumatoid Arthritis, Spine
Other Problems to Be Considered
Degenerative endplate changes (most common mimic)
Neuropathic arthropathy
Postoperative changes (granulation tissue)
Neoplasia (metastasis)
Spondyloarthropathy of hemodialysis
Rheumatoid arthritis
Seronegative spondyloarthropathies (eg, ankylosing spondylitis, Reiter syndrome)
More on Spondylodiskitis |
 Overview: Spondylodiskitis |
| Imaging: Spondylodiskitis |
| Follow-up: Spondylodiskitis |
| Multimedia: Spondylodiskitis |
| References |
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Further Reading
Keywords
spondylodiskitis, spondylodiscitis, infectious spondylitis, infective spondylitis, osteomyelitis, vertebral osteomyelitis with discitis, IS, intravenous drug abuse, IVDA
