Infection of Spinal Facets
Abstract & Commentary
Synopsis: Pyogenic spinal facet joint infections almost all occur in the lumbar region and, compared to infection of the disc or vertebral body, are often more acute in onset and more likely to be associated with unilateral pain.
Source: Muffoletto AJ, et al. Spine. 2001;26:1570-1576.
Muffoletto and colleagues report the characteristics of the 6 patients with hematogenous pyogenic facet joint infection seen among the 140 cases of pyogenic spinal infection at their institution over 13 years and also review 27 cases previously reported in the literature.
Among the total of 31 cases, the mean age was 55 years and there was a slight predominance of males. All but 1 infection involved the lumbar spine; the remaining case involved the cervical spine. Forty-two percent had coexisting extraspinal infection, 13% had diabetes mellitus, 10% had underlying liver disease, 6% were injection drug users, and 3% each had end-stage renal disease, alcohol abuse, and chronic corticosteroid use. Ninety-seven percent had pain, often acute in onset; 70% were febrile, 44% had radiculopathy, and 9% had a neurological deficit.
The sedimentation rate and C-reactive protein were elevated in all in whom the test was performed, but only 47% had an elevated WBC. Specimens for culture were obtained by percutaneous aspiration or during surgical intervention or by blood culture. Among cases in which a pathogen was identified, Staphylococcus aureus accounted for 81%.
Technetium-99 scans were positive in all 19 patients in whom it was performed and MRI demonstrated facet joint changes in 17 of 19 (89%), with changes in each case seen as early as 2 days after symptom onset. Epidural abscess was found in 25% of patients, epidural granulation in 38%, and paraspinal abscess in 19%. Most patients were managed surgically, but medical management alone has been successful in some cases.
Comment by Stan Deresinski, MD, FACP
The 4% incidence of facet joint involvement among all pyogenic spine infections is much higher than the 0.2% rate more commonly reported, although the latter figure may represent underdiagnosis and reporting. In addition to a hematogenous origin, infection of the facet joints may also occur after spinal surgery and after corticosteroid injection.
The average duration of symptoms in patients with facet joint infection prior to diagnosis tends to be shorter than those in patients with pyogenic spondylodiscitis and the symptoms are more likely to be unilateral in the former.
Gadolinium-enhanced MRI, because of its sensitivity and its ability to detect associated local complications, is the imaging procedure of choice. CT or fluoroscopically guided percutaneous aspiration is usually successful in obtaining samples for culture and may, in some cases, provide an adequate means of drainage, thus avoiding open surgical intervention. The percutaneous approach may also be used to drain associated psoas abscesses.
The differential diagnosis includes gout. In a recent report of a case of gouty arthritis involving an L4-L5 facet joint that mimicked an infectious process with epidural involvement, Barrett and colleagues state that 37 previous cases had been reported in the literature.1
Reference
1. Barrett K, et al. Neurosurgery. 2001;48:1170-1172.
Dr. Deresinski, Clinical Professor of Medicine, Stanford; Director, AIDS Community Research Consortium; Associate Chief of Infectious Diseases, Santa Clara Valley Medical Center, is Editor of Infectious Disease Alert.
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