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Objective:
Image-guided tissue biopsies are routinely performed in patients presenting with suspected spondylodiscitis, however, their diagnostic yield is debatable. Prior to proceeding with tissue biopsy, imaging modalities such as CT, MRI, or nuclear medicine scans are often utilized for diagnostic and planning purposes. The aim of this study is to evaluate the correlation between imaging features and CT-guided tissue biopsy results in the diagnosis of suspected spondylodiscitis.

Materials and Methods:
Retrospective single-center cohort study of patients undergoing CT-guided percutaneous vertebral or intervertebral disc biopsies performed by Interventional Radiologists of Liverpool Hospital, Sydney, between September 2017 and November 2020. Data collected includes basic demographic data such as gender and age, imaging features of CT and MRI as well as nuclear medicine scans, tissue biopsy culture results and histopathological analysis. Sensitivity and specificity were evaluated, Chi square analysis performed, as well as concordance analysis with Cohen’s kappa to identify the agreement between these diagnostic modalities (imaging and tissue biopsy) in diagnosing spondylodiscitis.

Results:
A total of 61 tissue biopsies were performed and included in the study, with a mean age of 64.8 years and a greater male proportion (68.8%). A majority of patients had both CT and MRI during the course of their presentation (36/61). A total of 16 samples returned a positive microbiological culture from the tissue biopsy. There were no statistically significant correlations between imaging features of both CT and MRI and a positive microbiological growth, with poor concordance values overall. MRI imaging features such as overall increased signals and paraspinal changes had the highest sensitivities (86.7% and 93.3%, respectively). The presence of increased intervertebral disc signal on MRI (<em>p</em> = 0.04) was the only imaging feature associated with a higher biopsy yield as defined by a positive histopathological result. Other imaging modalities, namely nuclear medicine scans, were not statistically significant in their association with a positive biopsy result on tissue culture (<em>p</em> = 1.00).

Conclusion:
The correlation between imaging findings suggestive of spondylodiscitis and a confirmative tissue biopsy defined by positive microbiological growth or histopathological evidence remains in question. However, MRI remains a superior imaging modality compared to CT with greater sensitivities overall in detecting features of discitis.