The effectiveness of CT-guided percutaneous spinal biopsy in the diagnosis of osteomyelitis and discitis

Abstract

Purpose: Spinal infections such as vertebral osteomyelitis and discitis are severe diseases associated with complications including sepsis, spinal instability and neurological deficits if not treated appropriately1. Identification of the causative organism is therefore paramount to treatment, particularly as empirical antibiotic regimes can lead to unnecessary and prolonged antibiotic use, which has adverse consequences for the patient and resistance patterns2. Percutaneous CT-guided biopsies can assist with pathogen isolation and, thus, determine suitable treatment options1,3. However, success rates of microbiological identification after biopsies range from 31-57% in recent studies4-6 and potentially lower with pre-biopsy antibiotics7-9, although some studies disagree1,2. Methods and materials: A retrospective audit of all patients undergoing a CT-guided biopsy of either the intervertebral disc or vertebral body end plate for suspected spinal infection at Nambour Hospital between January 2009 and April 2015. Core biopsies were performed and specimens were sent for histological and microbiological analysis. The biopsy success rate was determined by the proportion of specimens where an organism was isolated. A review of case notes for subsequent clinical diagnosis and management was also performed to assess the therapeutic impact of the biopsy by determining the number of cases where the results led to a change in management. Further, administration of pre-biopsy antimicrobial therapy was analysed to assess if this reduces the likelihood of positive bacteriology. The affect of needle size, CT approach and number of passes on success rates were also examined. Results: A total of 14 patients had a CT-guided biopsy of the vertebral body end plate or intervertebral disc performed. The patients were aged 30-93 (mean = 60) and 64% were male. An organism was isolated in 11/14 patients (78.6%) including Staphylococcus Aureus (n = 1), Candida (n = 3), coagulase-negative Staphylococcus (n = 2), gram negative bacteria (n = 3) and other (n = 2). Blood cultures were positive in one patient and this corresponded with their biopsy organism. There was a raised white cell count in four patients (28.6%) and raised CRP in 13 patients (92.9%). Conclusion: Percutaneous CT-guided biopsy is an important investigation in the diagnosis of spondylodiscitis. In this study, an organism was isolated in 79% of biopsies performed which enabled appropriate targeted antibiotic treatment. This success rate is higher than in recent studies and as it is dependant on numerous factors, this study aims to evaluate these associated factors including needle size, CT approach, number of passes obtained and pre-biopsy antibiotic treatment.<br />