Importance of the problem

The incidence of vertebral osteomyelitis (VO) and spinal epidural abscess (SEA) are presently on the rise. An aging population with associated co‐morbidities, increased IVDU, and the prevalence of spinal instrumentation are among the reasons thought to explain the elevated rates of these spinal infections.^1–5 The incidence of VO has been reported to be 2.2–7.4 per 100 000 population per year,^6–8 and the incidence of SEA has been reported to be 0.2–2.8 per 10 000 hospital admissions per year,^9,10 or 1.8 per 100 000 persons per year.¹¹

Rationale

In order to assess treatment options and prognosis, one must first have the correct index of suspicion for VO and epidural abscess. Understanding the characteristic presentation of the problem permits accurate diagnosis.

Clinical comment

VO and SEA are serious conditions with significant morbidity and mortality. Unfortunately, the diagnosis is often difficult, and as a result delayed, which only increases morbidity and mortality.^12–14 It is essential to understand typical presentation, examination findings, and imaging characteristics in order to correctly diagnose the condition when present and provide efficient management.

Available literature and quality of the evidence

• Level I: 0 studies identified.
  
• Level II: 0 studies identified.
  
• Level III: 3 systematic reviews of retrospective observational studies, 1 retrospective case series study.

Findings

A systematic review and meta‐analysis of 12 retrospective studies considering the medical and surgical management of SEA found IVDU to be the most frequently reported risk factor (22%), and diabetes (27%) and hepatic disease to be the most commonly reported co‐morbidities. The most common symptoms were back pain (67%), motor weakness (52%), and fever (44%). There were significantly more patients with back pain, fever, and motor weakness compared to historical data.¹⁵ The grade of recommendation from this systematic review is low given the retrospective nature of the studies reviewed.

A systematic review of 14 retrospective studies found that back pain was the most common presenting symptom (85% of patients), followed by fever (60%), and neurologic deficit (34%). In the five studies that included duration of symptoms, the mean time from onset of symptoms to diagnosis ranged from 11 to 59 days. Paraspinal or epidural abscesses were found in 44% of cases of VO.¹⁶ A recent retrospective observational study over a 12‐year period found local tenderness in <20% of cases of VO.^17,18 Magnetic resonance imaging (MRI) is considered the gold standard for diagnosis of VO, with sensitivity/specificity >90%.^1,3,4,18 The systematic review found MRI to have a sensitivity and specificity of 94% but also noted that plain radiography revealed abnormalities in 89% of cases, though other reviews note its limited utility in early disease.^1,11 Notably, 6% of patients demonstrated continuous lesions spanning multiple levels, and 3% had skip lesions.¹⁶ The grade of recommendation from this review is low based on the low levels of evidence of the included studies.

A retrospective case‐control study of 233 adult patients with SEAs who underwent entire spinal imaging over an 18‐year period at a tertiary referral healthcare system found 22 patients with skip lesions. Three risk factors were identified: delay in presentation (>7 days), concomitant area of infection outside the spine, and an erythrocyte sedimentation rate (ESR) >95 mm/h at presentation. The predicted probability for the presence of skip lesions was 73, 13, 2, and 0% with the identification of 3, 2, 1, and 0 risk factors, respectively.¹⁹ The grade of recommendation from this single retrospective study is low based on the retrospective nature of the study.

Resolution of clinical scenario

• Axial pain, fever, and neurologic findings are the most common presenting symptoms, but they are not specific, and often not all found at the same time (grade of recommendation: low).
  
• MRI is the most useful diagnostic imaging modality. Consideration should be given to imaging the entire spine in cases of VO/SEA (grade of recommendation: low).
  
• Patients with delay in presentation, concomitant area of infection outside the spine, and ESR >95 are at high risk of having skip lesions (grade of recommendation: low).