Ultrasound-guided aspiration may show higher sensitivity in diagnosing infection after THA
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Results presented here showed ultrasound-guided aspiration was more commonly successful and more sensitive in diagnosing periprosthetic joint infections in patients who underwent total hip arthroplasty.
“We believe that ultrasound-guided hip aspiration may become the preferred modality in diagnosing periprosthetic joint infection, but further prospective, randomized, controlled trials would be ideal in confirming this,” Emily Boes, MD, said in her presentation at the Musculoskeletal Infection Society (MIS) Annual Meeting.
Boes and colleagues retrospectively performed a chart review of all image-guided aspirations of THAs for periprosthetic joint infection. Researchers documented whether an aspiration was considered a success or dry tap, defined as less than 0.5 ccs, and recorded the volume of fluid obtained if successful.
“We looked at aspiration cell counts, gram stain and cultures, and we recorded all of the necessary data points to calculate an MIS score,” Boes said.
Of the 290 hip aspirations included in the study, Boes noted 155 were fluoroscopic-guided and 135 were ultrasound-guided aspirations. Ultrasound-guided aspiration had significantly fewer dry taps compared with fluoroscopy-guided aspiration, with a success rate of 69% for ultrasound-guided aspiration and 53% for fluoroscopy-guided aspiration, according to Boes.
“When looking at the fluid volume obtained, after excluding the dry taps, we found that ultrasound had a significantly higher amount of fluid obtained, with ultrasound being 13 ccs and fluoroscopy 10 ccs,” Boes said.
Researchers also compared the sensitivity and specificity between ultrasound- and fluoroscopy-guided aspiration in diagnosing periprosthetic joint infection both by culture results alone and by 2018 MIS criteria.
“Sensitivity and specificity are determined based on the results of a screening test compared to the results of the gold-standard test,” Boes said.
Among 47 patients who had both aspiration and intraoperative cultures, Boes noted the ultrasound-guided group had a significantly higher sensitivity at 75% vs. 50% in the fluoroscopy-guided group. She added the two groups showed no differences in specificity.
When using 2018 MIS criteria, Boes noted 152 fluoroscopy-guided aspirations and 134 ultrasound-guided aspirations had chronic periprosthetic joint infection, defined as more than 12 weeks from the index procedure.
“The sensitivity with this method in the fluoroscopy group was 52% and ultrasound 77%,” Boes said. “This was, again, significantly higher sensitivity in the ultrasound group and there was no difference in the specificity.”
Perspective
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Emily Boes, MD, and colleagues have presented an intriguing study evaluating the diagnostic utility of ultrasound vs. fluoroscopic techniques for aspirating patients undergoing THA who demonstrate clinical concern for periprosthetic joint infection.
The study findings confirm the vital importance of finding and sampling synovial fluid to establish or exclude the diagnosis of periprosthetic joint infection. Ultrasonography provides its operator with the ability to visualize intraarticular effusions, a key advantage over fluoroscopy. However, it is also critical to note that ultrasound is more of a technically demanding procedure which can depend on operator experience, as well as patient factors, including BMI, body habitus and if revision surgery has been previously performed.
The relevance of 'dry tap' aspirations continues to be unclear in the literature. The conclusions of the study force us to wonder if the previous conflicting literature is the result of inconsistent aspiration methods being performed. The study highlights the evident need in the periprosthetic joint infection clinical literature for a standardized method by which aspiration results and the technique utilized to be reported. The study also raises the question of whether an effusion by itself is suggestive of periprosthetic joint infection, a question which will hopefully be addressed through prospective investigations, improvement in imaging techniques and more standardized outcome reporting.
Reference:
Christensen TH, et al. J Arthroplasty. 2022;doi:10.1016/j.arth.2022.01.066.
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Boes E, et al. Paper 963. Presented at: Musculoskeletal Infection Society Annual Meeting; Aug. 5-6, 2022; Pittsburgh (hybrid meeting).
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