Post-Operative Infection Imaging¶

Definition¶

Post-operative spinal infection complicates 1–12% of spinal surgeries, with instrumented posterior fusions carrying the highest risk. Imaging diagnosis is challenging because normal post-surgical changes mimic infection on MRI. Serial imaging and clinical correlation are essential.

Imaging Challenges¶

Normal post-surgical findings that can mimic infection: - Endplate edema at the surgical level (normal for 6–12 months) - Enhancement along the surgical tract (normal for months) - Small epidural fluid collections (seromas) - Disc signal changes after discectomy

Findings Suggesting Infection¶

Progressive or increasing enhancement on serial MRI (rather than decreasing)
Enlarging fluid collection with rim enhancement — suggests abscess
Restricted diffusion (DWI) within a collection — favors abscess over seroma
Paraspinal soft tissue enhancement extending beyond the surgical bed
Hardware loosening — lucency developing around screws
New disc enhancement with endplate destruction

CT¶

Fluid collection around hardware
Progressive screw loosening
Gas in soft tissues (normal early post-op, abnormal after 2–3 weeks)

Clinical Pearl

The key to diagnosing post-operative infection is serial comparison — infection shows progressive or worsening findings, while normal post-surgical changes improve over time. When in doubt, a DWI sequence can help: restricted diffusion within a post-operative fluid collection strongly suggests abscess rather than seroma.

Key Points¶

Post-operative infection is diagnostically challenging due to normal surgical changes
Serial imaging is essential — worsening findings suggest infection
DWI restricted diffusion distinguishes abscess from seroma
Progressive screw loosening can indicate infection
Clinical correlation (CRP, wound status) is critical
Biofilm on instrumentation is a major treatment challenge

References¶

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Corona-Cedillo R, Saavedra-Navarrete MT, Espinoza-Garcia JJ, Mendoza-Aguilar AN, Ternovoy SK, Roldan-Valadez E. Imaging Assessment of the Postoperative Spine: An Updated Pictorial Review of Selected Complications. Biomed Res Int. 2021;2021:9940001. PMID: 34113681. PMCID: PMC8154286.
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Dumont RA, Keen NN, Bloomer CW, Schwartz BS, Talbott J, Clark AJ, Wilson DM, Chin CT. The Clinical Utility of Diffusion-Weighted Imaging in Spinal Infection. Clin Neuroradiol. 2019;29(3):515–522. doi:10.1007/s00062-018-0681-5. PMID: 29582111. PMCID: PMC6158113.
Zabaglo M, Leslie SW, Sharman T. Postoperative Wound Infections. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2024. Available from: https://www.ncbi.nlm.nih.gov/books/NBK560533/