Infected total knee arthroplasties present in a variety of different clinical settings. With severe local compromise and draining sinus tract around the knee, after adequate debridement, the resultant patellectomy with need for free muscle transfer and split thickness skin graft for closure, usually results in loss of quadriceps function. This necessitates the need for drop lock brace. No good mechanisms are available for reconstruction of large anterior defects in total infected total knees where this occurs. Can proximal placement of the knee joint with longer tibial segments aid in closure in patients with large anterior skin defects, and can this placement aid in quadriceps reconstruction to alleviate the need for drop lock braces while ambulating?Background
Questions
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.
