CT-guided biopsy in suspected spondylodiscitis: microbiological yield, impact on antimicrobial treatment, and relationship with outcome

Abstract

Purpose: To investigate the clinical impact of CT-guided biopsy, as performed in routine clinical practice, in patients with suspected spondylodiscitis on MRI in terms of culture yield, impact on antimicrobial treatment, and outcome.

Methods: This study included 64 patients with MRI findings compatible with spondylodiscitis who underwent CT-guided biopsy.

Results: Initial CT-guided biopsies were culture-positive in 20/64 (31.3%, 95% confidence interval [CI] 21.2-43.3%). Repeat CT-guided biopsies (after initial negative biopsy) were culture-positive in an additional 5/15 (33.3%, 95% CI 15.2-58.3%). Serum leukocytes, C-reactive protein, pre-biopsy use of antibiotics, neurological symptoms, MRI findings, vertebral height loss, and hyperkyphosis were not significantly different between culture-positive and culture-negative cases (P = 0.214-1.000); 75% (15/20) of initial CT-guided biopsies that were culture-positive provided additional information to clinicians for guiding antibiotic treatment. Sixty-two of 64 patients (96.9%, 95% CI 89.3-99.1%) would have been adequately treated if a strategy was followed that would subject all patients without clinical findings suspicious for "atypical" microorganisms and negative blood cultures to empirical antibiotics (i.e., clindamycin for coverage of Gram-positive bacteria) without using biopsy results to determine the optimal antibiotic regimen. Outcome within 6 months (development of neurologic or orthopedic complications, surgery, and death) was not significantly different (P = 0.751) between culture-positive and culture-negative patients.

Conclusions: Although CT-guided biopsies are culture-positive in a minority of cases, the majority of positive cultures are useful to tailor antibiotic treatment. Empirical treatment with clindamycin may cover almost all micro-organisms in positive biopsy specimens, provided patients are not immunocompromised. Outcome appears similar between culture-positive and culture-negative patients.

Keywords: Biopsy; CT; Culture yield; Spine infection; Spondylodiscitis.

Fig. 1

An 80-year-old woman with MRI findings consistent with osteoporotic vertebral fractures. Sagittal T1-weighted (a), fat-suppressed T2-weighted, and gadolinium-enhanced subtraction images (c) show collapse of vertebrae T12 (continuous arrows) and T8 (dashed arrows), with edema (b) and gadolinium enhancement of anterior and posterior portions of the T12 vertebra (c), and the impression of some edema in adjacent discs (b). However, there is no clear involvement of two consecutive vertebrae. Moreover, the involvement of multiple levels and the configuration of the affected vertebrae strongly suggest osteoporotic vertebral fractures. This patient underwent CT-guided biopsy with spondylodiscitis in the differential diagnosis of the original clinical report, but was excluded from this study

Fig. 2

A 54-year-old woman with MRI findings consistent with acute Schmorl node. Sagittal T1-weighted (a), fat-suppressed T2-weighted (b), gadolinium-enhanced T1-weighted (c), and gadolinium-enhanced subtraction images (d) show a focal impression in the superior endplate of the L3 vertebra with surrounding pathological signal intensity (arrows), but involvement of only one endplate and no diffuse signal intensity abnormality of the adjacent disc. This patient underwent CT-guided biopsy with spondylodiscitis in the differential diagnosis of the original clinical report, but was excluded from this study

Fig. 3

A 67-year-old man with MRI findings typical of spondylodiscitis. Sagittal fat-suppressed T2-weighted (a) and gadolinium-enhanced T1-weighed images (b) show involvement of the L4 and L5 vertebrae (arrows), and also increased T2 signal of the L4-L5 disc (a). Axial gadolinium-enhanced T1-weighted image (c) shows a paravertebral phlegmon (arrowheads). CT-guided biopsy was performed (d), with positive cultures for Staphylococcus warneri

Fig. 4

A 88-year-old man with MRI findings atypical of spondylodiscitis. Sagittal T1-weighted (a), fat-suppressed T2-weighted (b), gadolinium-enhanced T1-weighted (d), and gadolinium-enhanced subtraction images (e) show pathological signals in both the L2 and L3 vertebrae (arrows and arrowheads), but no clear T2 hyperintensity or gadolinium enhancement of the L2–L3 disc. Axial T2-weighted (c) and gadolinium-enhanced T1-weighted images (f) do not show any paravertebral phlegmon or abscess either. CT-guided biopsy was culture-negative