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Introduction: Hypertrophy of the tensor fascia lata muscle (HTFLM) is a rare complication after total hip arthroplasty (THA) and is a potential source of pain, palpable mass, or both. Materials and methods: We retrospectively analyzed 1285 primary THAs and 482 THA revisions (THAR) performed at our center from 2008 to 2014. Among these, five patients had HTFLM (average age 68.8 years). The type of surgery and symptoms were evaluated, as were imaging studies (CT or MRI) of both hips (10 hips), and functional outcomes with the Merle d'Aubigné score. Results: The suspected diagnosis was established at an average of 30.2 months after surgery. Four cases occurred after THA and one case after THAR. A modified Hardinge approach was used in four cases and a Röttinger approach in one case. Two cases had pain and palpable mass in the trochanteric region and three cases only pain. The asymmetric HTFLM of the THA side against the nonsurgical side was confirmed by measuring the cross section of the tensor fascia lata muscle on imaging. The sartorius muscle was measured for reference in each case. The Merle d'Aubigne scale had a mean value of 16.6 (range 13-18) at 38 months after the procedure. Conclusions: HTFLM after THA is a benign condition that could be mistaken for a tumor when presenting as a palpable mass. We propose that it should be considered in the differential diagnosis of pain in the lateral aspect of hips that have previously undergone THA. [ABSTRACT FROM AUTHOR]

Objective: To determine the accuracy of guided computed tomography aspiration in the detection of septic hip prosthesis before surgery.Materials and Methods: Sixty-three patients (35 women and 28 men; age range, 29-86 years; mean age, 71 years) with clinically suspected septic hip prosthesis were prospectively studied with independent review board (IRB) approval. Volume and microbiological cultures of aspirated fluid and several computed tomography imaging findings such as periprosthetic fluid collections, prosthetic acetabular malposition, and heterotopic ossification were analyzed. All patients underwent revision surgery and infection was finally diagnosed in 33 patients.Results: Statistical comparative analysis was performed comparing computed tomography aspiration and surgical findings (95% CI; level of significance at P=0.05 two-sided) with 70% sensitivity, 100% specificity, 84% accuracy, 100% positive predictive value, and 75% negative predictive value. Using Fisher's exact test, the presence of periprosthetic fluid collections (P=0.001), prosthetic acetabular malposition (P=0.025) and aspirated fluid volume (P=0.009) were significantly higher in infected than in non-infected prostheses, whereas heterotopic ossification was not (P=0.429).Conclusion: Computed tomography aspiration is accurate to preoperatively diagnose septic hip prosthesis on the basis of volume and bacterial cultures of aspirated joint fluid. Furthermore, imaging findings such as periprosthetic fluid collections and prosthetic acetabular malposition strongly suggest infected prosthesis. [ABSTRACT FROM AUTHOR]

KEY WORDS With the recent trend towards reducing hospital stay, it has become increasingly important to ensure that early patient discharge after total hip replacement is a safe practice. We evaluated complications and length of hospital stay associated with primary unilateral hip arthroplasty in 47 patients undergoing a new early discharge protocol consisting of at home based specialized care after hospital discharge. The mean length of stay (and standard deviation) in hospital was 4.59±0.68. The mean length of stay of home-based hospitalization was 3.7±1. The prevalence of postoperative complications was 12.8% and the readminssion rate was 6.4%. We saw a reduction of hospital stay with no difference in outcomes in comparison with previous data. On the basis of our findings we recommend the use of the early discharge protocol following elective primary total hip replacement and ongoing evaluation of the process. [ABSTRACT FROM AUTHOR]

The histology of periprosthetic tissue is a gold standard for the diagnosis of periprosthetic joint infection. However, the specificity and sensitivity of histology has never been 100%. In the present study we hypothesized that the type of microorganism could be related to the effectiveness of histology in the detection of infection. Frozen sections and cultures from periprosthetic tissue of 38 revision arthroplasties taken at the time of resection arthroplasty for the treatment of infection were retrospectively reviewed. Frozen sections were evaluated following Feldman’s criteria. A culture was considered positive when the same microorganism was isolated in at least two samples or when pus was present around the prosthesis. The literature providing information on histology and microbiology of arthroplasty-associated infection was reviewed. Coagulase-negative staphylococcus (CNS) was the etiology in 13 cases, Gram-negative bacilli in 8, Staphylococcus aureus in 7 , Candida sp in 2, Peptococcus sp in 2, Enterococcus sp in 1 and S. pneumoniae in 1. No microorganism was isolated in four cases. Almost all the frozen sections in the 38 cases were positive except in 2 of the 13 that were caused by CNS (15.3%). The articles reviewed supported our findings. Frozen section is a useful test to intraoperatively confirm an infection when preoperative septic loosening is suspected. However, histology has false-negative results when the infection is due to low-virulence microorganisms. [ABSTRACT FROM AUTHOR]

Background. There is no clinical trial analyzing the best moment to infuse an antibiotic during knee arthroplasty performed during ischemia. We designed a single-center, randomized, double-blind, placebo-controlled trial to evaluate whether antibiotic therapy hould be administered before tourniquet inflation or just before tourniquet deflation. Material and methods. Patients who underwent a primary knee arthroplasty were randomized to receive (1) 1.5 g of cefuroxime 10-30 min before inflation of the tourniquet and placebo 10 min before release of the tourniquet (standard arm) or (2) placebo 10-30 min before inflation of the tourniquet and 1.5 g of cefuroxime 10 min before release of the tourniquet (experimental arm). In both arms, a postoperative dose of 1.5 g of cefuroxime was given 6 h after the surgical procedure. The main variables associated with the rate of deep-tissue infection after 3 and 12 months of follow-up were gathered. Continuous variables were compared using Student's t test, and categorical variables were compared using the X2 test or Fisher's exact test. Results. From September 2004 through December 2005, a total of 908 patients were randomized, 442 and 466 of whom were allocated to the standard and experimental arms, respectively. There were no differences between treatment arms in terms of age, sex, comorbidity, American Society of Anaesthesiologists score, duration of surgery, need of blood transfusion, or fourth-day hematocrit. The rates of deep-tissue infection among the standard and experimental groups were 3.4% and 1.9%, respectively, at 3 months of follow-up (P=.21) and 3.6% and 2.6%, respectively, at 12 months of follow-up (P=.44). Conclusion. The administration of prophylactic antibiotics just before tourniquet release was not inferior to standard antibiotic prophylaxis. [ABSTRACT FROM AUTHOR]

Background: Appropriate interpretation of a frozen section has a relatively high specificity and sensitivity for the diagnosis of infection when septic loosening of a prosthesis is suspected. However, its usefulness for predicting the presence of microorganisms at the time of reimplantation after hip resection arthroplasty for the treatment of infection is not well defined. The aim of the present study was to evaluate the usefulness of histological analysis in this situation. Methods: From January 2002 to February 2006, a total of twenty-one patients underwent reimplantation after hip re- section arthroplasty for the treatment of infection. Histological studies and cultures of specimens of periprosthetic tissue that had been obtained at the time of reimplantation were retrospectively reviewed. The results of culture were considered positive when the same microorganism was isolated in at least two samples. Two histological criteria were used to diagnose infection: (1) Criterion A (the Feldman criterion), defined as the presence of at least five neutrophils per high-power field (x400) in at least five separate microscopic fields and (2) Criterion B (the Athanasou criterion), defined as the presence of at least one neutrophil per high-power field (x400), on average, after examination of ten microscopic fields. The sensitivity, specificity, positive predictive value, and negative predictive value of each of these criteria were calculated with use of microbiological results as the gold standard for defining infection. Results: Seven of the twenty-one patients had a positive result on culture, and the most common microorganism was coagulase-negative staphylococcus. The sensitivity, specificity, positive predictive value, and negative predictive value of frozen-section analysis were 28.5%, 100%, 100%, and 73.6%, respectively, according to the Feldman criterion and 71.4%, 64.2%, 50%, and 81.8%, respectively, according to the Athanasou criterion. The numbers of lymphocytes and plasma cells did not help in the diagnosis of infection. Fibrosis was more common in patients without an infection. Conclusions: The probability of infection is high when at least five neutrophils per high-power field are found in the periprosthetic tissue, but it is not possible to rule out infection when the number of neutrophils is less than five. Level of Evidence: Diagnostic Level I. See Instructions to Authors for a complete description of levels of evidence. [ABSTRACT FROM AUTHOR]

A rare case of an infected chronic hematoma in a patient with immunodeficiency syndrome mimicking a soft tissue neoplasm is presented. There are few reported cases of hematogenous infection of chronic hematomas, which be difficult to differentiate from soft tissue neoplasms. [ABSTRACT FROM AUTHOR]

A retrospective study was performed to evaluate the cement mantle in two groups of patients treated with the acetabular components of cemented Exeter total hip arthroplasties (THAs). Two groups of 20 patients were compared: Group 1 received non-flanged acetabular cemented cups (Contemporary, Stryker) and Group 2 received flanged acetabular cemented cups (X3 Rim Fit, Stryker). Cups in Group 2 were implanted after using a rim cutter device. Group 2 showed better penetration of cement in zone 1 (10.76 mm compared with 2.93 mm; p = 0.008) and a thicker cement mantle in zone 1 (3.57 mm compared with 2.89 mm; p = 0.04). More cups in Group 2 had a cement mantle thickness less than 3 mm (30 % in Group 1 compared with 70 % in Group 2; p = 0.0039). No other radiological differences were observed. These results favor the use of a rim cutter device and flanged cup to improve the cement mantle for the acetabular components of cemented Exeter THAs. However, the improvements were less than expected. In view of the results of previous studies, further research is therefore needed to assess the value of this approach in improving the acetabular cement mantle. [ABSTRACT FROM AUTHOR]

Background: Surgical site infection (SSI) rate after surgery for hip fracture is about 4%. The aim of the present study was to review the efficacy of dual prophylaxis using teicoplanin plus cefuroxime and risk factors for SSI.Patients: Operations for hip fracture from 2012 to 2013 were retrospectively reviewed. Relevant information was gathered: Demographics, comorbidities, ASA score, laterality, type of fracture, type of surgery, d from admission to surgery, length of surgery, hemoglobin value at admission, urinary or respiratory infections, and the need for pre-operative, intra-operative, and post-operative red blood cell (RBC) transfusion. Prophylaxis consisted of cefuroxime and teicoplanin during the induction of anesthesia. U.S. Centers for Disease Control and Prevention (CDC) criteria for superficial and deep SSI were applied. Univariate and multivariable analysis were performed.Results: Six hundred fifty-seven patients were included in the study. Thirteen (2.0%) SSI were identified, six superficial (0.9%), and seven deep (1.1%). Staphylococcus aureus was isolated in two infections (one superficial and one deep). The SSI rate was 2.4% in intra-medullary nails (n = 334), 1.4% in prostheses (n = 211), and 1.8% in other synthesis (n = 112). Parameters independently associated with SSI were: Intra-operative RBC transfusion (OR: 11.6, p = 0.002), length of surgery >120 min (OR: 4.5, p = 0.02), and having a urinary infection (OR: 4.28, p = 0.02).Conclusion: Dual prophylaxis including cefuroxime and teicoplanin was associated with a 2% rate of SSI. Staphylococcus aureus caused only two SSIs. Reducing SSI is of utmost importance for patients' quality of life and to avoid additional cost of surgical procedures. Therefore, more experience with dual prophylaxis is needed to confirm our results. [ABSTRACT FROM AUTHOR]

Purposes: The aim of the present study was to evaluate the importance of isolated microorganisms according to the Gram stain and the type of antibiotic received on the outcome of early prosthetic joint infection (PJI) treated with debridement, antibiotics and implant retention (DAIR). Methods: From January 1999 to December 2009, all patients with an early PJI were prospectively registered in a database and they were retrospectively reviewed for this study. Results: During the study period, 160 patients met the inclusion criteria of the study. After a mean (SD) post-debridement follow-up of 5.2 (2.5) years, 117 patients (73.1%) were considered to be in remission and 43 (26.9%) were classified as failure. Variables associated with failure were liver cirrhosis (66.7% vs. 22.8%, p=0.001), diagnosis within the first 30 days from arthroplasty (30.4% vs. 8.0%, p=0.020), C-reactive protein (CRP) >12 mg/dl (46.7% vs. 21.2%, p=0.005), microorganism isolated in all deep samples (31.1% vs. 16.0%, p=0.047) and Gram-negative (GN) infection not treated with a fluoroquinolone (57.1% vs. 20.0%, P=0.004). Gram-positive (GP) infection not treated with rifampin was close to be statistically significantly associated with failure (34.4% vs. 19.2%, p=0.067). A multivariate analysis identified liver cirrhosis (OR: 12.4 CI95%: 3.1-49.7, p<0.001), CRP-value (OR: 1.06 CI95%: 1.0-1.11, p=0.049), and when a GN-infection was not treated with a fluoroquinolone (OR: 6.5, CI95%: 1.8-23.8, p=0.005) as independent predictors of failure. Conclusion: The remission rate of PJI treated with DAIR after 3 years of follow-up was 73%. The main predictors of failure were liver cirrhosis, the selected antibiotic most specially fluoroquinolones for GN and rifampin for GP infections, the C-reactive protein and the number of samples culture positive as a potential surrogate markers of bacterial density. [ABSTRACT FROM AUTHOR]

The prognosis associated with the DePuy ASR hip cup is poor and varies according to the series. This implant was withdrawn from use in 2010 and all patients needed to be assessed. We present the results of the assessment of our patients treated with this device, according to the Spanish Society of Hip Surgery (SECCA) algorithm published in 2011. This retrospective study evaluates 83 consecutive ASR cups, followed up at a mean of 2.9 years. Serum levels of chromium and cobalt, as well as the acetabular abduction angle, were determined in order to assess their possible correlation with failure, defined as the need for revision surgery. The mean Harris Hip Score was 83.2 (range 42-97). Eight arthroplasties (13.3%) required revision due to persistent pain and/or elevated serum levels of chromium/cobalt. All the cups had a correct abduction angle, and there was no correlation between elevated serum levels of metal ions and implant failure. Since two previous ASR implants were exchanged previously to the recall, the revision rate for ASR cups in our centre is 18.2% at 2.9 years. [ABSTRACT FROM AUTHOR]

Due to its advantages, ceramic-on-ceramic bearings have been widely used in young patients for almost 30 years. Long-term survivorship, low wear, and low biological reactivity to particles are some of its characteristics. Even though this material has had a lot of improvements, the risk of fracture is one of the concerns. There have been reports of fracture of ceramic in the acetabular liner and head but no fractures of both in the same patient. We report a case of a fracture in a sandwich type acetabular liner and the ceramic head in a patient involving ankylosing spondylitis. It occurred three years after the operation and with no history of direct trauma. We decided to change the bearing surfaces to metal polyethylene without removing the metal back. The patient is satisfied by the clinical results after a 5-year followup. [ABSTRACT FROM AUTHOR]

The use of short stem designs in total hip arthroplasty is not a new concept, but its popularity has increased as a bone-sparing alternative to traditional stems. This study analyzed the midterm clinical and radiological results of the Taperloc Complete Microplasty stem (Zimmer Biomet® Warsaw, IN, USA). A total of 32 patients (20 men and 12 women) were retrospectively documented and received 40 stems (eight bilateral). The median patient age was 50 years (interquartile range 43-58) at the time of surgery. The median follow-up was 36.5 months (interquartile range 26.75-50.25). Indication for total hip arthroplasty was osteoarthritis (62.5% of patients), avascular necrosis (25%), and developmental dysplasia of the hip (12.5%). The Merle d'Aubigné score improved from a mean 11.5 preoperatively to a mean 17.5 at the latest follow-up. During X-ray assessment, we observed one subsidence of the stem (3 mm) and four cases of varus malalignment without clinical consequences. No cases of osteolysis were reported, and no stems were revised. According to our results, this short tapered stem shows a good early-term outcome. Prospective results and a longer follow-up are needed to assess the long-term survival of this stem fully. [ABSTRACT FROM AUTHOR]

Objectives The combination of a fluoroquinolone with rifampin is one of the cornerstones in the treatment of prosthetic joint infections (PJI) caused by staphylococci. Moxifloxacin is highly active against methicillin–susceptible Staphylococcus aureus (MSSA) and, therefore, is an attractive agent to use. However, several studies reported a lowering in serum moxifloxacin levels when combined with rifampin. The clinical relevance remains unclear. We determined the outcome of patients with early acute PJI caused by MSSA treated with either moxifloxacin/rifampin or levofloxacin/rifampin. Methods Medical files of patients treated with moxifloxacin/rifampin (University Medical Centre Groningen) or levofloxacin/rifampin (Hospital Clinic Barcelona) were retrospectively reviewed (2005–2015). Treatment failure was defined as the need for revision surgery and/or suppressive therapy, death by infection or a relapse of infection during follow-up. Results Differences in baseline characteristics between the two cohorts were observed, but prognostic parameters for failure, as defined by the KLIC-score (Kidney failure, Liver cirrhosis, Index surgery, C–reactive protein and Cemented prosthesis), were similar in the two groups (2.9 [1.5 SD] for the moxifloxacin group vs. 2.2 [1.2 SD] for the levofloxacin group [ P  = 0.16]). With a mean follow-up of 50 months (36 SD) in the moxifloxacin group, and 67 months (50 SD) in the levofloxacin group ( P  = 0.36), treatment was successful in 89% vs. 87.5%, respectively ( P  = 0.89). None of the failures in the moxifloxacin group were due to rifampin– or moxifloxacin–resistant S. aureus strains. Conclusion Our data indicate that moxifloxacin combined with rifampin is as clinically effective as levofloxacin/rifampin for early acute PJI caused by MSSA. [ABSTRACT FROM AUTHOR]

A reduction in femoral offset may decrease muscle tension and lead to spacer dislocations even though proximal femur, musculature and acetabulum remain intact. In this study, we aimed to determine whether postoperative lateral femoral offset (LFO) and modified vertical femoral offset (MVFO) values affect the risk of dislocation of a hip spacer.~Introduction~Background~We measured LFO and MVFO in properly centred, postoperative, anteroposterior radiographs of the pelvis in 66 patients (71 spacers). We then compared the operated and non-operated sides and recorded any dislocations.~Materials and Methods~Methods~Although LFO decreased (p<0.001), the reduction was not associated with dislocation (p = 0.471). MVFO remained unchanged after spacer implantation (p = 0.277) and was not associated with dislocation (p = 0.418).~Results~Results~In conclusion, the preformed spacer decreased LFO but not MVFO compared with the contralateral hip. The variations did not significantly affect the dislocation rate.~Conclusions~Conclusions [ABSTRACT FROM AUTHOR]

Large acetabular defects remain a challenge in hip revision arthroplasty. Experience with Trabecular Titanium¿ (TT) cups (Limacorporate S.p.a.) has not been widely reported. Therefore, we assessed the survivorship and clinical and radiological outcomes of patients receiving TT cups, with or without supplementary trabecular titanium hemispherical modules for acetabular reconstruction, in primary and revision total hip arthroplasty (THA).~Background~Background~Between January 2009 and July 2014, we performed 67 revisions and 5 primary THAs using TT cups in 69 patients. To achieve stability and/or restore the hip's centre of rotation, hemispherical modules were used in 17 cases based on preoperative templating and/or intraoperative findings. Mean follow-up was 30.5 months. Acetabular bone defects were classified according to the Paprosky classification. Survivorship, functional outcomes (Merle d'Aubigné) and radiological outcomes were analysed.~Methods~Methods~8 patients underwent cup revision: 2 for loosening, 3 for infection, and 3 for hip dislocation. The remaining cases did not present radiological signs of loosening. None of the cases with Paprosky type I classifications needed revision, while 4 with type II and 4 with type III needed revision (p = 0.028). The respective mean values for pain, walking, and range of motion (Merle d'Aubigné scores ± standard deviation) were 3.6 ± 1.4, 3.7 ± 0.7, and 3.8 ± 0.6 preoperatively, and 5.7 ± 0.7, 5.3 ± 0.7, and 5.6 ± 0.7 at the latest follow-up (p<0.001).~Results~Results~In the short term, results with TT cups appear to be encouraging, with satisfactory survival rates for both simple and complex cases.~Conclusions~Conclusions [ABSTRACT FROM AUTHOR]

Objectives: Early prosthetic joint infections (PJIs) are managed with debridement, implant retention and antibiotics (DAIR). Our aim was to evaluate risk factors for failure after stopping antibiotic treatment.Methods: From 1999 to 2013, early PJIs managed with DAIR were prospectively collected and retrospectively reviewed. The main variables potentially associated with outcome were gathered, and the minimum follow-up was 2 years. For the present study, only patients who were in remission after one debridement and without long-term antibiotic suppression were included. The primary endpoint was implant removal or the need to reintroduce antibiotic treatment due to failure.Results: One-hundred-and-forty-three patients met the inclusion criteria. The failure rate after a median duration of oral antibiotic treatment of 69 days (IQR 45-95 days) was 11.8%. In 92 cases, PJI was due to Gram-positive microorganisms, in 21 cases PJI was due to Gram-negative microorganisms and in 30 cases PJI was due to a polymicrobial infection with both Gram-positive and Gram-negative microorganisms. In Gram-positive infections, rifampicin administered in combination with linezolid, co-trimoxazole or clindamycin was associated with a higher failure rate (27.8%, P = 0.026) than that in patients receiving a combination of rifampicin with levofloxacin, ciprofloxacin or amoxicillin (8.3%) or monotherapy with linezolid or co-trimoxazole (0%). Among patients with a Gram-negative infection, the use of fluoroquinolones was associated with a lower failure rate (7.1% versus 37.5%, P = 0.044).Conclusions: The only factor associated with failure was the oral antibiotic selection, not the duration of treatment. Linezolid, co-trimoxazole and clindamycin, but not levofloxacin, serum concentrations are reduced by rifampicin; a fact that could explain our findings. Further studies monitoring serum concentration could help to improve the efficacy of these antibiotics when administered in combination with rifampicin. [ABSTRACT FROM AUTHOR]

Introduction: The pathogenesis of prosthesis loosening is not well understood. The aim of our study was to sonicate components of joint prostheses removed due to aseptic loosening, culture the sonicate fluid, and to correlate these results with the degree of radiological osteolysis. Methods: From January 2008 to June 2009 all consecutive patients who underwent a revision of hip or knee prosthesis due to aseptic loosening were included in the study. Aseptic loosening was established when the patient had radiological signs of loosening without symptoms or signs of infection. The diagnosis was confirmed when histology was negative, and ≥5 out of 6 standard cultures of periprosthetic tissue were negative. Bone lysis was measured according to the Paprosky or Engh classifications without knowing the result of sonication cultures. Removed components were placed in sterile bags and immediately transported to the microbiology laboratory and sonicated. Sonicate fluid was cultured and the results were correlated with the degree of bone lysis. The proportion of components with positive sonication culture according to the bone lysis classification was compared using χ test. Results: A total of 52 patients were included and 123 components were sonicated. In 30 patients at least 1 sonicated component was positive (57.7%) and 44 out of 123 (35.8%) components were positive. The proportion of positive sonication cultures was significantly higher in the group of components with a higher degree of bone lysis of 3 (76.5%) than in those with lower degrees (33.9% for 1 and 24% for 2) (χ test, p = 0.0004). Conclusions: Sonication cultures were positive in 57% of patients who underwent revision arthroplasty for aseptic loosening. The percentage of positive sonication cultures was significantly higher in patients with severe osteolysis. Level of evidence: level I of Prognostic Studies-Investigating the Effect of a Patient Characteristic on the Outcome of Disease. [ABSTRACT FROM AUTHOR]

Surgical navigation systems are offered to provide more precise implantation of the femoral component in hip resurfacing (HR), allowing to reduce the risk of malpositioning and of femoral neck fracture and notching. We conducted a retrospective analysis of 30 HR divided into two cohorts and compared the results of a nonnavigated group (15 hips) with those of a navigated group (15 hips). The BrainLAB Computer Navigation System was used in all cases. No notching occurred in either group. The femoral component did not show better positioning in the navigated group, but more outlier cases were observed in the nonnavigated group (7, versus 3 in the navigated group). Although there are no long-term studies showing that surgical navigation increases the survival of HR, the avoidance of outlier values justifies its use, especially during the surgical learning curve, which is a difficult and lengthy one. [ABSTRACT FROM AUTHOR]

Background: Appropriate interpretation of a frozen section has a relatively high specificity and sensitivity for the diagnosis of infection when septic loosening of a prosthesis is suspected. However, its usefulness for predicting the presence of microorganisms at the time of reimplantation after hip resection arthroplasty for the treatment of infection is not well defined. The aim of the present study was to evaluate the usefulness of histological analysis in this situation.Methods: From January 2002 to February 2006, a total of twenty-one patients underwent reimplantation after hip resection arthroplasty for the treatment of infection. Histological studies and cultures of specimens of periprosthetic tissue that had been obtained at the time of reimplantation were retrospectively reviewed. The results of culture were considered positive when the same microorganism was isolated in at least two samples. Two histological criteria were used to diagnose infection: (1) Criterion A (the Feldman criterion), defined as the presence of at least five neutrophils per high-power field (x400) in at least five separate microscopic fields and (2) Criterion B (the Athanasou criterion), defined as the presence of at least one neutrophil per high-power field (x400), on average, after examination of ten microscopic fields. The sensitivity, specificity, positive predictive value, and negative predictive value of each of these criteria were calculated with use of microbiological results as the gold standard for defining infection.Results: Seven of the twenty-one patients had a positive result on culture, and the most common microorganism was coagulase-negative staphylococcus. The sensitivity, specificity, positive predictive value, and negative predictive value of frozen-section analysis were 28.5%, 100%, 100%, and 73.6%, respectively, according to the Feldman criterion and 71.4%, 64.2%, 50%, and 81.8%, respectively, according to the Athanasou criterion. The numbers of lymphocytes and plasma cells did not help in the diagnosis of infection. Fibrosis was more common in patients without an infection.Conclusions: The probability of infection is high when at least five neutrophils per high-power field are found in the periprosthetic tissue, but it is not possible to rule out infection when the number of neutrophils is less than five.Level Of Evidence: Diagnostic Level I. [ABSTRACT FROM AUTHOR]