ASEPTIC VERSUS SEPTIC FAILURES IN TOTAL HIP ARTHROPLASTIES-DIFFICULTY IN DETECTION OF BACTERIAL BIOFILM

Abstract

The determination of the cause of prosthetic failures in total hip arthroplasties can be difficult. Pre-operative imaging, including plain x-rays, tri-phse bone scan and MRI imaging have not been able to discern septic from aspectic causation. White blood cell scans, once thought specific for infection when positive, has demonstrated positivity in”wear and debris” reactions. Labs including WBC, Sed Rate, CRP can be elevated in septic, as well as, aseptic failures. Although frozen section is reliable showing acute inflammation for infection, chronic active inflammation which often is seen with chronic infections, can also be seen in aspectic failures. Cultures are often falsely positive, but in chronic infection it may be associated with less than 80% retrieval.

Five cases of acetabular loosening associated with radiolucencies around a prosthesis were studied. These cases had rapid failures and were thought to be secondary to an oil residual left after processing of an in growth prosthesis. All patients had a radiolucent zone around the bone prosthetic intersurface. The patients had increasing pain on weight bearing and a positive bone scan. Frozen section at the time of surgery demonstrated chronic inflammation and was culture negative. The acetabular prosthesis and associated parts were placed immediately in 80% Etoh and Tris buffer. Combinations of confocal laser microscopy with live-dead stains, FISH Probes for Staph., or scanning electron microscopy was performed looking for biofilm.

All five of the prosthesis or related parts showed the presence of bacterial biofilm. One of these had cement covering the porous portion.

These results demonstrate our inability to discern aseptic from septic loosening in total hip arthroplasty by the current clinical means.