Platelet-leukocyte gel (PLG) contains high concentrations of platelets and leukocytes. As leukocytes play an important role in the innate host-defense, we hypothesized that PLG might have antimicrobial properties. This study investigated the antimicrobial activity of PLG against Staphylococcus aureus and the contribution of myeloperoxidase (MPO), present in leukocytes, in this process. Platelet-rich plasma (PRP) and platelet-poor plasma (PPP) were obtained from whole blood of six donors. PLG was prepared by mixing PRP with autologous (PLG-AT) or bovine thrombin (PLG-BT). Antimicrobial activity of PLG-AT, PLG-BT, PRP, and PPP was determined in a bacterial kill assay. MPO release was measured by ELISA and activity was measured using a MPO activity assay. Cultures showed a rapid decrease in the number of bacteria for both PLG-AT and PLG-BT, which was maximal between 4 and 8 h, to approximately 1% of the bacteria in controls. The effect of PLG-AT was largest and significantly different compared to PRP ( p ¼ 0.004) and PPP ( p < 0.001), however not compared to PLG-BT ( p ¼ 0.093). PLG-AT, PLG-BT, and PRP showed a comparable, gradually increasing MPO release. MPO activity was comparable for all groups and remained stable. No correlation between MPO release, activity, and bacterial kill could be found. PLG appears to have potent antimicrobial capacity, but the role of MPO in this activity is questionable. PLG might represent a useful strategy against postoperative infections. However, additional research should elucidate its exact antimicrobial activity. ß

No abstract

Periprosthetic joint infection (PJI) is a devastating complication after total joint arthroplasty, occurring in approximately 1%-2% of all cases. With growing populations and increasing age, PJI will have a growing effect on health care costs. Many risk factors have been identified that increase the risk of developing PJI, including obesity, immune system deficiencies, malignancy, previous surgery of the same joint and longer operating time. Acute PJI occurs either postoperatively (4 wk to 3 mo after initial arthroplasty, depending on the classification system), or via hematogenous spreading after a period in which the prosthesis had functioned properly. Diagnosis and the choice of treatment are the cornerstones to success. Although different definitions for PJI have been used in the past, most are more or less similar and include the presence of a sinus tract, blood infection values, synovial white blood cell count, signs of infection on histopathological analysis and one or more positive culture results. Debridement, antibiotics and implant retention (DAIR) is the primary treatment for acute PJI, and should be performed as soon as possible after the development of symptoms. Success rates differ, but most studies report success rates of around 60%-80%. Whether single or multiple debridement procedures are more successful remains unclear. The use of local antibiotics in addition to the administration of systemic antibiotic agents is also subject to debate, and its pro's and con's should be carefully considered. Systemic treatment, based on culture results, is of importance for all PJI treatments. Additionally, rifampin should be given in Staphylococcal PJIs, unless all foreign material is removed. The most important factors contributing to treatment failure are longer duration of symptoms, a longer time after initial arthroplasty, the need for more debridement procedures, the retention of exchangeable components, and PJI caused by Staphylococcus (aureus or coagulase negative). If DAIR treatment is unsuccessful, the following treatment option should be based on the patient health status and his or her expectations. For the best functional outcome, one-or two-stage revision should be performed after DAIR failure. In conclusion, DAIR is the obvious choice for treatment of acute PJI, with good success rates in selected patients. Key words: Arthroplasty; Prosthesis; Infection; Periprosthetic joint infection; Retention; Debridement antibiotics and implant retention; Debridement; Acute Core tip: Acute periprosthetic joint infection (PJI) is a major complication after total joint arthroplasty, and occurs either postoperatively or via hematogenous spreading. Debridement, antibiotics and implant retention (DAIR), the primary treatment for acute PJI, should be performed as soon as possible after the development of symptoms, and has success rates around 60%-80%. Whether single or multiple debridement procedures are more successful remains unclear. Sys- REVIEW

Background Despite modern fracture management techniques allowing for near anatomic reduction of acetabular fractures, there continues to be a risk of posttraumatic arthritis and need for total hip arthroplasty (THA). Few well-controlled studies have compared THA after acetabular fractures with THAs performed for other indications in terms of survivorship or complications, and none, to our knowledge, present 10-year survivorship data in this setting. Questions/purposes (1) How does the 10-year survival of THA compare between those patients who underwent THA after an acetabular fracture and those who underwent THA for primary arthritis or avascular necrosis (AVN)? (2) Is there an increased risk of serious complications like infection, dislocation, and aseptic loosening as well as heterotopic ossification associated with a THA performed after a previous acetabular fracture? Methods This retrospective case-control study compared findings of patients who underwent THA after acetabular fracture versus a matched cohort of patients who had received a primary THA for primary osteoarthritis or AVN. Between 1987 and 2011, we performed 95 THAs after acetabular fracture; of those, 74 (78%) met inclusion criteria and had documented followup beyond 2 years in our institutional registry. We selected 74 matched patients based on an algorithm that matched patients based on preoperative diagnosis, date of operation, age, gender, and type of prosthesis. During this time, we performed approximately 8000 THAs that were potentially available for matching based on complete followup beyond 2 years. We compared cases and control subjects using the KaplanMeier survivorship estimator as well as a comparison of the proportions in each group that developed major complications (including infection, dislocation, loosening, and heterotopic ossification) based a retrospective chart review. Results The 10-year survivorship after THA was lower in patients with a previous acetabular fracture than in the matched cohort (70%, 95% confidence interval [CI], 64%-78%, versus 90%, 95% CI, 86-

PurposeWe investigated the hypothesis that many total hip arthroplasty revisions that are classified as aseptic are in fact low-grade infections missed with routine diagnostics.MethodsIn 7 Dutch hospitals, 176 consecutive patients with the preoperative diagnosis of aseptic loosening of their total hip arthroplasty were enrolled. During surgery, between 14 and 20 tissue samples were obtained for culture, pathology, and broad-range 16S rRNA PCR with reverse line blot hybridization. Patients were classified as either not being infected, suspected of having infection, or infected according to strict, predefined criteria. Each patient had a follow-up visit after 1 year.Results7 patients were classified as infected, 4 of whom were not identified by routine culture. 15 additional patients were suspected of having infection. 20 of these 22 patients received a cemented prosthesis, fixated with antibiotic-loaded bone cement. All 22 patients received prophylactic systemic antibiotics. 7 of them reported complaints one year after surgery, but only one showed signs of early loosening. However, additional surgery was not performed in any of the patients.InterpretationAlthough the proportions were not as high as previously reported in the literature, between 4% and 13% of patients with the preoperative diagnosis of aseptic loosening were infected. However, as thorough debridement was performed during surgery and prophylactic antibiotics were used, the diagnosis of infection did not have any obvious clinical consequences, as most patients performed well at the 1-year follow-up. Whether this observation has implications for long-term implant survival remains to be seen.

BackgroundSeveral studies suggest that histologic findings from tissues obtained at revision arthroplasty for failed metal-on-metal (MOM) total hip implants may reflect an immune reaction to particles or ions in some patients. However, only a limited number of cases without MOM implants were reported as controls in those studies.Questions/purposesThe purpose of this study is to better define the extent and distribution of morphologic features attributed to an immune reaction in tissues sampled at revision surgery for failed nonMOM THA.Patients and MethodsAs part of a multicenter, prospective study, we reviewed 612 capsular and interface tissues obtained from 130 patients at revision THA. The samples were selected from periacetabular regions (154 samples from 103 patients), femoral implant/cement-bone interface (154 samples from 79 patients), and from areas of the joint capsule that had an intraoperative gross appearance suggesting the possibility of either infection or metallosis (256 samples from 129 patients). All patients had more than one sample obtained. The extent and distribution of lymphocytes and plasma cells, acute inflammation, and visible particles of debris were graded using criteria similar to those described to grade inflammation around failed MOM implants.ResultsWe identified perivascular lymphocytes in 111 biopsy samples taken from 65 (50%) of 130 patients, and in 87 specimens from 57 (53%) of 107 patients thought to have aseptic loosening. Diffusely distributed lymphocytes were identified in 86 (66%) of 130 patients, and in 66 (62%) of the 107 hips with aseptic loosening, although few had the highest grade of inflammation. Increasing extent of diffuse and perivascular lymphocytes correlated with increasing extent of metal particles.ConclusionsMild lymphocytic inflammation, diffuse and especially perivascular, is common in tissues around failed nonMOM implants. Although extensive inflammation in an inflammatory pseudotumor pattern is rare, it does occur in some cases of failed metal-polyethylene hip arthroplasties. The importance of inflammation is unknown, but the extent of diffuse inflammation shows a positive correlation with metal debris, so it could reflect a reaction to particles or ions in some patients.

Background and purposeTo minimize the risk of hematogenous periprosthetic joint infection (HPJI), international and Dutch guidelines recommended antibiotic prophylaxis prior to dental procedures. Unclear definitions and contradictory recommendations in these guidelines have led to unnecessary antibiotic prescriptions. To formulate new guidelines, a joint committee of the Dutch Orthopaedic and Dental Societies conducted a systematic literature review to answer the following question: can antibiotic prophylaxis be recommended for patients (with joint prostheses) undergoing dental procedures in order to prevent dental HPJI?MethodsThe Medline, Embase, and Cochrane databases were searched for randomized controlled trials (RCTs), reviews, and observational studies up to July 2015. Studies were included if they involved patients with joint implants undergoing dental procedures, and either considered HPJI as an outcome measure or described a correlation between HPJI and prophylactic antibiotics. A guideline was formulated using the GRADE method and AGREE II guidelines.Results9 studies were included in this systematic review. All were rated “very low quality of evidence”. Additional literature was therefore consulted to address clinical questions that provide further insight into pathophysiology and risk factors. The 9 studies did not provide evidence that use of antibiotic prophylaxis reduces the incidence of dental HPJI, and the additional literature supported the conclusion that antibiotic prophylaxis should be discouraged in dental procedures.InterpretationProphylactic antibiotics in order to prevent dental HPJI should not be prescribed to patients with a normal or an impaired immune system function. Patients are recommended to maintain good oral hygiene and visit the dentist regularly.

No options are available for local antibiotic delivery from uncemented implants. By loading a porous titanium implant with a biomimetic HA-coating (PeriApatite, PA) with antibiotics, we could obtain adequate local antibiotic concentrations and reduce infection susceptibility. This study investigated the efficacy of a tobramycin-loaded PA-coated titanium foam implant in preventing infection, as well as the effects on osseointegration. In 72 New Zealand White rabbits, an uncoated (Ti), PA-coated (PA), or Tobramycin-PA-coated (PA-tobra) titanium foam rod was implanted intramedullary in the left tibiae after contamination of the implant bed with none (control), 10 3 , 10 4 or 10 5 CFU Staphylococcus aureus. PA-tobra implants were loaded with 2.4 mg tobramycin. After 28 days analysis was done by bacteriology, histopathology and histomorphometry. Six percent of the contaminated PA-tobra rabbits were infected, whereas this was 53 and 67% for PA and Ti, respectively (p < 0.001). Quantitative cultures were also significantly lower in the PA-tobra group (p ¼ 0.003). None of the control rabbits were infected. Histopathological and histomorphometrical scores were both better for the PA-tobra group, although only significant compared to Ti. No significant differences were observed between PA and Ti rabbits. We conclude that the application of tobramycin to PAcoated titanium foam implants appears to be an effective local antibiotic strategy for uncemented implants for infection prophylaxis and has a beneficial effect on implant fixation, which will result in improved long-term implant survival. ß