Disc versus Bone? Osteomyelitis Discitis Biopsy

Percutaneous Disc Biopsy versus Bone Biopsy for the Identification of Infectious Agents in Osteomyelitis/Discitis

Clinical question

Which diagnostic approach is more effective for vertebral discitis and osteomyelitis: intervertebral disc biopsy or vertebral body biopsy?

Take away point

Disc biopsies may provide superior diagnostic accuracy for vertebral discitis and osteomyelitis when compared to bone biopsy.

Reference

Zamarud A, Kesten J, Park DJ, et al. Percutaneous Disc Biopsy versus Bone Biopsy for the Identification of Infectious Agents in Osteomyelitis/Discitis. J Vasc Interv Radiol. 2024;35(6):852-857.e1. doi:10.1016/j.jvir.2024.02.016

Click here for abstract

Study design

Retrospective, observational, cohort study

Setting

Academic setting

Figure

Figure 1. Representative images from a disc biopsy procedure. A 75-year-old man with back pain underwent (a–c) magnetic resonance (MR) imaging and (d–f) fluoroscopy-guided bone biopsy. Sagittal (a) T2, (b) T1, and (c) contrast-enhanced MR images showed findings suspicious for L4/L5 discitis (arrow) and osteomyelitis of L4 and L5 (arrowheads). Percutaneous biopsy of the L4/L5 was performed in an oblique (d, e) anteroposterior and (f) lateral view. (d) A safe trajectory was noted on the oblique anteroposterior view (hemostat marker), and (e) an introducer needle was advanced in plane on this view into the disc space (arrow). (f) The introducer stylet was then removed, and a biopsy needle was used to sample the disc space (arrow).

Summary

Vertebral discitis and osteomyelitis (VDO) are severe spinal infections, potentially leading to significant neurological deficits and structural spinal damage. In addition to non-invasive imaging (MRI) to localize and characterize the extent of the infection, biopsy of the affected disc and/or vertebral body is obtained via a percutaneous image-guided approach (fluoroscopy or CT) for identification of the causative organism to tailor antibiotic treatment. The decision to perform a biopsy of the affected disc or vertebral body is typically left to the discretion of the proceduralist. This retrospective cohort study aimed to compare the diagnostic yield of disc biopsies versus vertebral body biopsies in patients with suspected VDO. It was hypothesized that percutaneous sampling of the disc rather than the affected vertebra would be more likely to yield a positive tissue culture as infection of the disc is believed to be the inciting event in most patients.

Patients included in the study underwent biopsy procedures between 2019 and 2023 due to suspected VDO. Inclusion criteria required patients to be >= 18 years of age with presumed VDO based on MR imaging who undergone percutaneous biopsy. Data were extracted from EMR, focusing on biopsy procedure details, culture results, patient demographics, imaging findings, and treatment outcomes. 66 patients were included in the study–36 had disc biopsies, 30 had vertebral body biopsies, and 6 (3 in each group) underwent repeated procedures given initial negative tissue sampling result. Biopsies were performed by 5 different neurointerventional radiologists and 1 neurosurgeon. The decision to biopsy the disc or bone was at the discretion of the physician with varying techniques. The primary outcome measure was the culture yield (positive or negative) after percutaneous sampling. Statistical analyses included chi-square tests and Fisher’s exact tests to compare positivity rates between the biopsy methods.

Patient characteristics did not different significant between the two groups, except for the history of intravenous drug use (26.7% compared with 5.5% in patients who underwent bone biopsy and disc biopsy, respectively). Disc biopsies had a significantly higher rate of positive cultures compared to bone biopsies; 41% compared to 15% There were no statistically significant association between the biopsy culture results and pre-biopsy antibiotic administration. Neither were there any significant association between pre-biopsy blood cultures and biopsy culture results; in fact, 90% of the cases had a negative blood culture prior to the biopsy. No adverse events were noted after the procedure in either procedure group.

The authors discussed the positive implications for clinical practice, including improved pathogen identification and thus more tailored antibiotic therapy for VDO. The authors’ findings corroborated with previous studies that have reported low diagnostic yields from bone biopsies. Limitations of the study included its small scale and retrospective nature. Overall, the authors concluded that percutaneous biopsy of VDO should prioritize sampling of the disc to increase the likelihood of a positive tissue culture and allow tailored narrowed antibiotic coverage.

Commentary

This retrospective study addresses the clinically relevant question of whether percutaneous biopsy for VDO should prioritize sampling the disc or bone to increase the probability of a positive tissue culture, enabling more targeted antibiotic therapy. 

However, the small sample size, the single-center nature of the study, and the potential bias introduced with each physician choosing a biopsy type at their own discretion may limit the strength of these results. Additionally, there was a minor discrepancy in culture results and results from histologic analysis. Two disc biopsy patients and 4 bone biopsy patients with negative culture results had an infectious etiology during histologic analysis. This suggests that histologic analysis may be complementary to tissue culture in detecting certain infections and should be explored in future studies. The significant difference in intravenous drug use history between the two groups could have also introduced a confounding variable and thus may have influenced the difference in outcomes slightly. This study could have benefitted from a multivariate analysis or propensity score matching to account for this difference. 

Despite all of these limitations, this study presents encouraging findings regarding the benefits of prioritizing percutaneous disc biopsy over bone biopsy for VDO. To integrate this approach into clinical practice, additional studies with larger sample sizes studied at multiple institutions and a more uniform cohort are necessary. Overall, these findings are the first step in shifting the clinical decision making of physicians in this setting and may prompt new guidelines in favoring percutaneous disc biopsy for VDO.

  

Post Author
Danielle Millner Balagtas, BA
MD Candidate, Class of 2027
University of Massachusetts Chan Medical School
@daniellelmb