26Postoperative diagnosis and outcome in @entity1 with revision arthroplasty for XXXX .

@entity1 @entity281 @entity1349
BACKGROUND: The most common cause of implant failure is @entity1349 ( @entity1349 ), followed by @entity281 ( @entity281 ). This study evaluates the incidence of @entity281 among @entity1 operated with suspected @entity1349 and whether the diagnosis of @entity281 was predictive of subsequent implant failure including re- @entity281 , at 2  years of follow up. METHODS: @entity1 undergoing revision hip or knee arthroplasty due to presumed @entity1349 from February 2009 to September 2011 were prospectively evaluated. A sonication fluid of prosthesis and tissue samples for microbiology and histopathology at the time of the surgery were collected. Implant failure include recurrent or persistent @entity281 , reoperation for any reason or need for chronic antibiotic suppression. RESULTS: Of 198 @entity1 with pre-and intraoperative diagnosis of @entity1349 , 24 (12.1  %) had postoperative diagnosis of @entity281 . After a follow up of 31  months (IQR: 21 to 38  months), 9 (37.5  %) of 24 @entity1 in the @entity281 group had implant failure compared to only 1 (1.1  %) in the 198 of @entity1349 group (p   <   0.0001). Sensitivity of sonicate fluid culture (>20  CFU) and peri-prosthetic tissue culture were 87.5  % vs 66.7  %, respectively. Specificities were 100  % for both techniques (95  % CI, 97.9-100  %). A greater number of @entity1 with @entity281 (79.1  %) had previous partial arthroplasty revisions than those @entity1 in the @entity1349 group (56.9  %) (p   =   0.04). In addition, 5 (55.5  %) @entity1 with @entity281 and implant failure had more revision arthroplasties during the first year after the last implant placement than those @entity1 with @entity281 without implant failure (1 @entity1 ; 6.7  %) (RR 3.8; 95  % CI 1.4-10.1; p   =   0.015). On the other hand, 6 (25  %) @entity1 finally diagnosed of @entity281 were initially diagnosed of @entity1349 in the first year after primary arthroplasty, whereas it was only 16 (9.2  %) @entity1 in the group of true @entity1349 (RR 2.7; 95  % CI 1.2-6.1; p   =   0.03). CONCLUSIONS: More than one tenth of @entity1 with suspected @entity1349 are misdiagnosed @entity281 . Positive histology and positive peri-implant tissue and sonicate fluid cultures are highly predictive of implant failure in @entity1 with @entity281 . @entity1 with greater number of partial hip revisions for a presumed @entity1349 had more risk of @entity281 . Early loosening is more often caused by hidden @entity281 than late loosening.
