Spondylodiscitis: a Retrospective Observational Study.

Overview

Spondylodiscitis is an infectious process affecting the vertebral bodies, intervertebral discs, and paraspinal tissues, sometimes involving the spinal cord, most often with a bacterial etiology. Instrumental diagnosis relies on CT, however, contrast-enhanced MRI is the most sensitive test for confirming the diagnosis, as abnormalities are usually detected earlier than with CT. More recently, nuclear diagnostics using 18-fluorodeoxyglucose (18-FDG) PET has proven very useful both for diagnosis and as a tool for monitoring therapeutic efficacy. Etiological diagnosis relies primarily on blood cultures and, if the former is not possible, diagnostic biopsy. Approximately one-third of patients lack a microbiological isolation, and the inability to implement targeted therapy is a known risk factor for treatment failure. Therapeutic indications are giving way to shorter courses based on the use of oral medications, even though the epidemiology of the countries from which most of the clinical indications and literature originate is profoundly different from that of Italy. An epidemiological analysis of the cases referred to our Center is therefore of primary importance.

Spondylodiscitis is an infectious process affecting the vertebral bodies, intervertebral discs, and paraspinal tissues, sometimes involving the spinal cord. The etiology is most often bacterial, with the main pathogens implicated being Staphylococcus aureus, streptococci, enterobacteriaceae, and other Gram-negative bacilli. Instrumental diagnosis relies on CT, which allows for the detection of lesions such as bony sequestrations and soft tissue abscesses, as well as the exclusion of epidural abscesses. Contrast-enhanced MRI, however, is the most sensitive test for confirming the diagnosis, as abnormalities are usually detected earlier than with CT. More recently, nuclear imaging, particularly 18-fluorodeoxyglucose (18-FDG) PET, has proven very useful both for diagnosing tissue with high glucose metabolism and as a tool for monitoring therapeutic efficacy. 18F-FDG-PET/CT has been associated with greater accuracy than MRI in diagnosing early spondylodiscitis in the first 2 weeks after symptom onset. Another important advantage of 18F-FDG-PET/CT over MRI is the potential identification of metastatic infectious foci, especially in patients with bacteremia, allowing for rapid source control. 18F-FDG-PET/CT is also useful for spondylodiscitis caused by mycobacteria, fungi, or Brucella, with some data suggesting different uptake values depending on the etiology. Etiological diagnosis, however, relies primarily on blood cultures, which can be positive in up to 50% of cases of native spondylodiscitis caused by S. aureus. When noninvasive isolation is not possible, a diagnostic biopsy is necessary. Despite the use of invasive techniques, approximately one-third of patients lack microbiological isolation, and the inability to implement targeted therapy is a known risk factor for treatment failure. It also leads to the use of broad-spectrum antimicrobials, with environmental and sometimes economic consequences. Therapeutic indications, until now based on case series and cohort studies dating back more than 40 years, are giving way to shorter courses based on the use of orally administered drugs. However, the epidemiology of the countries from which most of the clinical indications and literature on bone infections originate is profoundly different from that of Italy. Therefore, an epidemiological analysis of the cases referred to our Center is of primary importance.