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The challenges of culture-negative periprosthetic joint infection (PJI) have led to the emergence of molecular methods of pathogen identification, including next-generation sequencing (NGS). While its increased sensitivity compared with traditional culture techniques is well documented, it is not fully known which organisms could be expected to be detected with use of NGS. The aim of this study was to describe the NGS profile of culture-negative PJI.Patients undergoing revision hip or knee arthroplasty from June 2016 to August 2020 at 14 institutions were prospectively recruited. Patients meeting International Consensus Meeting (ICM) criteria for PJI were included in this study. Intraoperative samples were obtained and concurrently sent for both routine culture and NGS. Patients for whom NGS was positive and standard culture was negative were included in our analysis.The overall cohort included 301 patients who met the ICM criteria for PJI. Of these patients, 85 (28.2%) were culture-negative. A pathogen could be identified by NGS in 56 (65.9%) of these culture-negative patients. Seventeen species were identified as common based on a study-wide incidence threshold of 5%. NGS revealed a polymicrobial infection in 91.1% of culture-negative PJI cases, with the set of common species contributing to 82.4% of polymicrobial profiles. Escherichia coli, Cutibacterium acnes, Staphylococcus epidermidis, and Staphylococcus aureus ranked highest in terms of incidence and study-wide mean relative abundance and were most frequently the dominant organism when occurring in polymicrobial infections.NGS provides a more comprehensive picture of the microbial profile of infection that is often missed by traditional culture. Examining the profile of PJI in a multicenter cohort using NGS, this study demonstrated that approximately two-thirds of culture-negative PJIs had identifiable opportunistically pathogenic organisms, and furthermore, the majority of infections were polymicrobial.Diagnostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Preoperative anemia is an established risk factor for complications following total joint arthroplasty. Postoperative anemia can be managed with allogeneic blood transfusion, but this has inherent risks. A thorough preoperative workup can help to diagnose anemia and optimize these patients for surgery to minimize the need for postoperative transfusion. Perioperatively, the amount of blood loss can be minimized by using hypotensive anesthetic techniques and administering antifibrinolytic agents. Last, in the event that allogeneic blood transfusion is still required, strict transfusion guidelines should be followed. Evidence-based interventions for preoperative, perioperative, and postoperative blood management in total joint arthroplasty will be reviewed.

Background Diagnosis and treatment of culture negative total knee arthroplasty (TKA) periprosthetic joint infection (PJI) is challenging. There is debate over whether culture negative PJI confers increased risk of failure and which organisms are responsible. It is also unclear as to what factors predict conversion from culture negative to culture positivity. To address these issues, we performed an observational study to detect factors associated with transition from culture negative to culture positive TKA PJI in those patients that failed irrigation and debridement (I&D), determine the incidence of this transition, and identify those organisms that were associated with treatment failure. Methods A multicenter observational cohort study was performed on patients with TKA PJI as defined by Musculoskeletal Infection Society criteria without cultured organisms and treated with I&D. Primary outcome was failure defined as any subsequent surgical procedure. Secondary outcome included cultured organism within 2 years of initial I&D. Results Two hundred sixteen TKA I&D procedures were performed for PJI, and 36 met inclusion criteria. The observed treatment failure rate for culture negative PJI treated with I&D was 41.67%. Of those culture negative I&Ds that failed, 53.33% became culture positive after failure. Of those that converted to culture positive, 62.5% were Staphylococcus species. The odds ratio associated with becoming culture positive following culture negative treatment failure in the setting of antibiotic administration prior to the initial I&D procedure was 0.69 (95% confidence interval 0.14-3.47, P = .65). Conclusion Many cases of culture negative TKA PJI treated with I&D eventually fail and become culture positive. Staphylococci are common organisms identified after culture negative PJI.

Background: Reinfection rates after two-stage exchange arthroplasty for prosthetic joint infection (PJI) have been reported as high as 33 % in the literature. Understanding risk factors for treatment failure will help to preoperatively counsel patients on the likelihood of successful treatment and possibly influence the surgeon's treatment algorithm. This study aimed to delineate whether the presence of a draining sinus tract is associated with risk of failure of two-stage exchange arthroplasty. Methods: We performed a single institution, multi-center retrospective chart review of outcomes of patients treated for PJI with two-stage exchange arthroplasty between June 2006 and May 2016. For patients treated prior to 2011, PJI was defined based on the preoperative work-up and intraoperative findings as determined by the attending surgeon. After 2011, PJI was defined using MSIS consensus criteria. All patients had a minimum of follow-up of 2 years or treatment failure prior to 2 years. Treatment failure was defined as reinfection or failure to complete two-stage exchange secondary to persistent infection or other host factors. Operative reports and clinical notes were reviewed to assess for presence of a draining sinus tract. Results: 240 patients were treated for PJI with intended two-stage exchange arthroplasty. The overall rate of treatment failure was 29.6 % (71/240), while the overall rate of reinfection was 13.3 % (32/240). A total of 39 patients did not complete second stage revision; final treatment for these patients was amputation, fusion, or chronic antibiotic suppression. A total of 52 of 240 patients (21.7 %) had a draining sinus tract at presentation. Patients with a sinus tract were significantly less likely to be replanted compared to those without a sinus tract at presentation (13.3 % vs. 26.9 %, p=0.02). However, when accounting for all mechanisms of treatment failure, including reinfection following replantation, there was no statistically significant difference detected between the sinus and no-sinus groups (27.7 % vs. 36.5 %, p=0.22). Discussion: A draining sinus tract represents a chronic, deep infectious process with ultimate compromise of overlying soft tissues. Thus we hypothesized it would be associated with failure in a two-stage exchange arthroplasty. These data demonstrate that patients with a draining sinus are significantly less likely to undergo re-implantation. This provides evidence to the paucity of data surrounding draining sinuses and two-stage PJI treatment.

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Background Periprosthetic joint infection (PJI) is a leading cause of revision arthroplasty. Considerable controversy still exists whether single- or two-stage exchange is the better approach for patients with chronic PJI. Historically, single-stage exchange arthroplasty was thought to have an unacceptably high risk of reinfection compared with two-stage exchange but recent studies have demonstrated that this may not be the case. To be considered for single-stage exchange, patients should meet certain criteria including a preoperatively identified nonvirulent pathogen in an immunocompetent host with an uncompromised soft tissue envelope. It is unclear what proportion of patients with chronic PJI actually meet these criteria. Additionally, patients who meet the criteria for single-stage exchange are selected because, in principle, they may be more likely to be able to overcome the infection, but it is unknown what the reinfection risk is in patients undergoing two-stage exchange who might have met selection criteria for single-stage exchange. Questions/purposes (1) What percentage of patients with chronic PJI treated at our institution met the International Consensus Meeting criteria for single-stage exchange arthroplasty? (2) Is the risk of persistent or recurrent infection lower for patients treated with two-stage exchange who met International Consensus Meeting criteria for single-stage exchange than it is among those who did not meet those inclusion criteria? Methods Between 2012 and 2016, one referral center treated 120 patients with chronic PJI as determined by Musculoskeletal Infection Society (MSIS) criteria. During this time, we used single-stage exchange only rarely in patients with chronic PJI (3%; four of 120), and only in oncologic patients with mega-prosthesis implants; 7% (eight of 120) underwent other procedures (resection arthroplasty or arthrodesis). Of the remaining 108, 16% (17) were lost to follow-up; the remaining 91 were evaluated in this retrospective study. To answer our first question, we applied the International Consensus Meeting indications for single-stage exchange, which were a known nonvirulent preoperative organism, an immunocompetent host, and a healthy soft-tissue envelope without a sinus tract; we then calculated the percentage of patients who would have met those criteria. To answer our second question, we compared those who would and would not have met those criteria in terms of the proportion who were determined to be infection-free at 2 years using the MSIS criteria. Results Only 19% (20 of 108) of patients met the International Consensus Meeting criteria for single-stage exchange. With the numbers available, there was no difference between those who met and did not meet those criteria in terms of the proportion of patients who had persistent or recurrent infection 2 years after treatment (three of 15 versus 32% [24 of 76]; p = 0.38). Conclusions We found that only a small proportion of patients who presented with chronic PJI to a referral center would have been suitable for single-stage direct exchange; with the numbers available, we found no difference in the reinfection risk after two-stage revision in those patients compared with those who would not have met those criteria. Consequently, it is possible that a small proportion of patients may benefit from single-stage exchange, but our small sample size may have missed important differences in reinfection risk, and so our findings on that question must be considered preliminary. Larger studies randomizing patients who meet single-stage criteria to either single- or two-stage exchange will better elucidate the true reinfection risk in this patient population. Level of evidence Level III, therapeutic study.

Background Organisms may persist on polymethylmethacrylate (PMMA) spacer surfaces, and subclinical infection is postulated to be a source of infection recurrence. Several small patient series have shown a high proportion of positive sonication cultures on PMMA spacers at the second stage of a two-stage revision. However, the association between a positive sonication culture and the risk for recurrence of infection after two-stage exchange is not fully elucidated. Questions/purposes Are cultures derived from sonication of antibiotic spacers associated with infection control or recurrence after two-stage revision for prosthetic joint infection (PJI)? Methods Between September 2013 and April 2016, we treated 67 patients with PJI with two-stage revisions. At the second stage, all cement spacers were explanted and sonicated. A total of`10 (15%) patients were lost to followup or failed to reach 1-year followup during the study period, and another 16 (24%) were excluded for prespecified reasons, leaving 41 patients for analysis in this study. Of the 41 patients included in this study, there were 25 TKAs, 15 THAs, and one distal femoral replacement. All patients met the Musculoskeletal Infection Society criteria for PJI at Stage 1 of the two-stage revision. The most common infecting organisms prompting two-stage revision were methicillin-sensitive Staphylococcus aureus and coagulase-negative staphylococci. PMMA spacers were most frequently loaded with gentamicin or gentamicin/vancomycin. Standard 6-week intravenous antibiotic courses were used for index infections and postreimplantation suppression was used for 3 months in all patients as determined by cultures and sensitivities. Patients were assessed for recurrence of infection at postoperative clinic visits completed at standard intervals. The average length of followup was 1.9 years with a range of 1 to 3.3 years. Results Sonication cultures that reached a threshold of 5 colony-forming units for positive culture had poor screening utility for subclinical persistent infection (sensitivity: 0%; confidence interval [CI], 0%-60%), but reasonable use for ruling in successful two-stage revision (specificity: 95%; 95% CI, 82%-99%). Positive sonication culture results in the two of 41 (4.9%) explanted spacers yielded coagulase-negative staphylococci, different from primary prosthesis cultures in both patients (Corynebacterium and Proteus mirabilis), and did not alter antibiotic choice. Neither of the patients has developed a reinfection at followup of 1.2 and 1.9 years. Of the 39 two-stage revisions with negative spacer sonication cultures, four developed reinfections. Conclusions Positive sonication fluid culture of PMMA spacers during reimplantation surgery was not associated with persistent or recurrent infection at minimum followup of 1 year. We do not recommend routine sonication of explanted PMMA spacers in the absence of clinical evidence suggesting persistent infection. Multicenter, prospective studies with long-term followup are needed to determine if sonication of PMMA spacers can predict persistent or recurrent infection. Level of evidence Level III, diagnostic study.

Abductor deficiency after total hip arthroplasty is a rare and challenging problem facing reconstructive surgeons today. The etiologies are vast. Herein, we review the relevant anatomy of the abductor mechanism, as well as the course and potential sites of injury for the superior gluteal nerve. The diagnosis can be challenging, but a focus on history and physical examination is the most important diagnostic tool. Supplemental modalities include plain radiographs, arthrography, ultrasound, electromyography, and magnetic resonance imaging. A variety of treatments exists for symptomatic abductor deficiency. We review potential modalities ranging from soft tissue transfers, trochanter fixation and osteotomy with a slide, as well as potential revision components.

There is evidence that sonication of explanted prosthetic hip and knee arthroplasty components with culture of the sonication fluid may enhance diagnostic sensitivity. Previous studies on the use of implant sonicate cultures have evaluated diagnostic thresholds but did not elaborate on the clinical importance of positive implant sonicate cultures in the setting of presumed aseptic revisions and did not utilize consensus statements on periprosthetic joint infection (PJI) diagnosis when defining their gold standard for infection. (1) How do implant sonicate cultures compare with preoperative synovial fluid cultures and intraoperative tissue cultures in the diagnosis of PJI in both THA and TKA when compared against Musculoskeletal Infection Society (MSIS) criteria for PJI? (2) Utilizing implant sonicate cultures, what is the relative prevalence of bacterial species identified in PJIs? (3) What is the incidence of positive implant sonicate cultures in the setting of presumed aseptic revision hip and knee arthroplasty procedures, and what treatments did they receive? Between 2012 and 2016 we performed implant sonicate fluid cultures on surgically removed implants from 565 revision THAs and TKAs. Exclusion criteria including insufficient data to determine Musculoskeletal Infection Society (MSIS) classification, fungal-only cultures, and absence of reported colony-forming units decreased the number of procedures to 503. Procedures represented each instance of revision surgery (sometimes multiple in the same patient). Of those, a definitive diagnosis of infection was made using the MSIS criteria in 178 of 503 (35%), whereas the others (325 of 503 [65%]) were diagnosed as without infection. A total of 53 of 325 (16%) were considered without infection based on MSIS criteria but had a positive implant sonicate culture. Twenty-five of 53 (47%) of these patients were followed for at least 2 years. The diagnosis of PJI was determined using the MSIS criteria. Sensitivity of implant sonicate culture was greater than synovial fluid culture and tissue culture (97% [89%–99%] versus 57% [44%–69%], p < 0.001; 97% [89%–99%] versus 70% [58%–80%], p < 0.001, respectively). The specificity of implant sonicate culture was not different from synovial fluid culture or tissue culture with the numbers available (90% [72%–97%] versus 100% [86%–100%], p = 0.833; 90% [72%–97%] versus 97% [81%–100%], p = 0.317, respectively). Coagulase-negative Staphylococcus was the most prevalent organism for both procedure types. In PJIs, the five most frequent bacteria identified by synovial fluid, tissue, and/or implant sonicate cultures were coagulase-negative Staphylococcus (26% [89 of 267]), methicillin-susceptible Staphylococcus aureus (19% [65 of 267]), methicillin-resistant S. aureus (12% [43 of 267]), α-hemolytic Streptococci (5% [19 of 267]), and Enterococcus faecalis (5% [19 of 267]). Fifty-three of 325 (16%) presumed aseptic revisions had a positive sonication culture. Thirty-four percent (18 of 53) of culture-positive aseptic revision patients received antibiotic treatment for infection and 8% (4 of 53) underwent a secondary revision. The routine use of implant sonicate cultures in arthroplasty revisions improves the diagnostic sensitivity for detecting the presence of bacteria in both clinical and occult infections. Future studies will need to refine colony-forming unit thresholds for determining clinical infection and indications for treatment. Level III, diagnostic study.

BACKGROUND: Blood transfusion in total knee arthroplasty (TKA) is associated with increased morbidity, including periprosthetic joint infection (PJI). Tranexamic acid (TXA) reduces blood transfusion rates, but there is limited evidence demonstrating improved outcomes in TKA resulting from TXA administration. The objectives of this study were determining whether TXA was associated with decreased rate of PJI, decreased rate of outcomes associated with PJI, and whether there were differences in rates of adverse events. METHODS: A multicenter cohort study comprising 23,421 TKA compared 4,423 patients receiving TXA to 18,998 patients not receiving TXA. Primary outcome was PJI within two years of TKA. Secondary outcomes included revision surgery, irrigation and debridement, transfusion, and length of stay. Adverse events included readmission, deep vein thrombosis, pulmonary emboli, myocardial infarction, or stroke. Adjusted odds ratios were determined using linear mixed models controlling for age, sex, thromboembolic prophylaxis, Charlson comorbidity index, year of TKA, and surgeon. RESULTS: TXA administration reduced incidence of PJI by approximately 50% (OR 0.55; p=0.03). Additionally, there was decreased incidence of revision surgery at two years (OR 0.66; p=0.02). Patients receiving TXA had reductions in transfusion rate (OR 0.15; p

Periprosthetic joint infection (PJI) continues to be a devastating problem in the field of total joint arthroplasty, and recent literature can be used to make the preoperative diagnosis of PJI, guide nonsurgical and surgical treatment, and provide postoperative antimicrobial management of PJI patients. The diagnosis of PJI relies on traditional serum and synovial fluid tests, with newer biomarkers and molecular tests. Surgical treatment depends on the duration of infection, host qualities, and surgeon factors, and procedures include débridement, antibiotics, and implant retention, one-stage exchange arthroplasty, two-stage exchange arthroplasty, resection arthroplasty, fusion, or amputation. Appropriate management of PJI involves coordination with infectious disease consultants, internal medicine physicians, and orthopaedic surgeons. Antimicrobial management is guided by the organisms involved, whether it is a new or persistent infection, and antibiotic suppression should be administered on an individual case basis. The goals of this instructional course lecture are to review the most relevant recent literature and provide treating physicians and surgeons with the most up-to-date armamentarium to reduce the recurrence of PJI.

Introduction: Post-operative day (POD) 0 physical therapy (PT) after total knee arthroplasty (TKA) has been associated with improved outcomes such as shorter hospital length of stay (LOS), though p...

Background Total knee arthroplasty (TKA) periprosthetic joint infection (PJI) can be managed with debridement, antibiotic therapy, and implant retention (DAIR). Oral antibiotics can be used after DAIR for an extended time period to improve outcomes. The objective of this study was to compare DAIR failure rates and adverse events between an initial course of intravenous antibiotic therapy and the addition of extended treatment with oral antibiotics. Methods A multicenter observational study of patients diagnosed with a TKA PJI who underwent DAIR was performed. The primary outcome of interest was the failure rate derived from the survival time between the DAIR procedure and future treatment failure. Results One hundred eight patients met inclusion criteria; 47% (n = 51) received an extended course of oral antibiotics. These patients had a statistically significant lower failure rate compared to those who received only intravenous antibiotics (hazard ratio, 2.47; P = .009). Multivariable analysis demonstrated that extended antibiotics independently predicted treatment success, controlling for other variables. There was no significant difference in failure rates between an extended course of oral antibiotics less or more than 12 months (P = .23). No significant difference in the rates of adverse events was observed between patients who received an initial course of antibiotics alone and those who received a combination of initial and extended antibiotic therapy (P = .59). Conclusions Extending therapy with oral antibiotics had superior infection-free survival for TKA PJI managed with DAIR. There was no increase in adverse events, demonstrating safety. After 1 year, there appears to be no significant benefit associated with continued antibiotic therapy.

Scenario analyses have been used in multiple science-policy assessments to better understand complex plausible futures. Scenario archetype approaches are based on the fact that many future scenarios have similar underlying storylines, assumptions, and trends in drivers of change, which allows for grouping of scenarios into typologies, or archetypes, facilitating comparisons between a large range of studies. The use of scenario archetypes in environmental assessments foregrounds important policy questions and can be used to codesign interventions tackling future sustainability issues. Recently, scenario archetypes were used in four regional assessments and one ongoing global assessment within the Intergovernmental Science-Policy Platform for Biodiversity and Ecosystem Services (IPBES). The aim of these assessments was to provide decision makers with policy-relevant knowledge about the state of biodiversity, ecosystems, and the contributions they provide to people. This paper reflects on the usefulness of the scenario archetype approach within science-policy processes, drawing on the experience from the IPBES assessments. Using a thematic analysis of (a) survey data collected from experts involved in the archetype analyses across IPBES assessments, (b) notes from IPBES workshops, and (c) regional assessment chapter texts, we synthesize the benefits, challenges, and frontiers of applying the scenario archetype approach in a science-policy process. Scenario archetypes were perceived to allow syntheses of large amounts of information for scientific, practice-, and policy-related purposes, streamline key messages from multiple scenario studies, and facilitate communication of them to end users. In terms of challenges, they were perceived as subjective in their interpretation, oversimplifying information, having a limited applicability across scales, and concealing contextual information and novel narratives. Finally, our results highlight what methodologies, applications, and frontiers in archetype-based research should be explored in the future. These advances can assist the design of future large-scale sustainability-related assessment processes, aiming to better support decisions and interventions for equitable and sustainable futures. © 2019 by the author(s). Nadia Sitas, Ryan Blanchard, and Patrick O'Farrell were supported by SwedBio at Stockholm Resilience Centre funded by the Swedish International Development Cooperation Agency (SIDA). Zuzana Harm??kov? and Reinette Biggs were supported by the GRAID programme funded by the Swedish International Development Agency (SIDA). Reinette Biggs was also supported by the South African Research Chairs Initiative (SARChI) (grant 98766) and the Swedish Research Council (grant 621-2014-5137). Eefje den Belder was funded by the Ministry of Agriculture, Nature and Food Quality of the Netherlands. Support to Paula A. Harrison was provided by UK Department of Environment, Food and Rural Affairs and the EU-funded IMPRESSIONS project (Grant Agreement 603416).

Interspecific competition can influence patterns of habitat use by small mammals. We examined the effects of interspecific interactions on habitat use by prairie voles (Microtus ochrogaster) and meadow voles (M. pennsylvanicus), two species that co- occur in grass habitats in east-central Illinois, but differ in their tolerance of sparse cover (prairie voles are more tolerant than meadow voles of sparse cover). We conducted a species-removal study in open populations, a species-addition study with enclosed populations, and dyadic encounters in the field, using mown and unmown grass areas, and in the laboratory. In the species- removal study, we found a positive response of prairie voles to removal of meadow voles from unmown grass habitat, and of meadow voles to removal of prairie voles from mown grass habitat. Additionally, when both species were present in control sites, prairie voles were most abundant in mown grass and meadow voles in unmown grass. In enclosures we confirmed greater tolerance of sparse cover by prairie voles (similar numbers of individuals in mown and unmown sites) than meadow voles (more individuals in unmown than mown sites), and these patterns were unaffected by addition of the other species. In dyadic encounters conducted in the field, male prairie voles were dominant over male and female meadow voles in mown grass habitat, whereas female meadow voles were dominant over male and female prairie voles in unmown grass habitat. These dominance relationships, which are consistent with the known social systems of the two species, were not observed when dyadic encounters were conducted in the laboratory in a neutral arena that lacked structural habitat cues. Taken together, our data confirm differences between prairie voles and meadow voles in tolerance for sparse cover and indicate a role, though limited, for interspecific competition in reinforcing patterns of habitat use by each species.

Total hip and knee arthroplasties are two of the most successful procedures. Both have been found to be cost-effective and beneficial to a patient’s quality of life [1–4]. Historically, joint arthroplasty was reserved for those above the age of 65 who were debilitated from the pain of end-stage osteoarthritis. However, as the success of the operation has become widely known, patients are often inquiring about joint replacement earlier to help maintain and/or restore activity including athletic participation. The young active patient with end-stage osteoarthritis is in a therapeutic dilemma. The mechanism of failure for the majority of lower extremity joint replacements at long-term follow-up is aseptic loosening [5]. There is obvious concern that joint arthroplasty in young patients would therefore succumb to wear earlier due to increased use, potentially condemning the patient to numerous revisions and potentially catastrophic failure in their lifetime [6–10]. Despite such concern, arthroplasty is used to treat end-stage osteoarthritis in younger patients that seek to restore function and even return to athletic activity [11, 12]. Fortunately, the concern for increased wear and early failure has not been fully realized, and survival rates as high as 94% can be found at nearly 20 years in young active patients [12]. In this chapter we will explore the literature and current recommendations concerning hip and knee arthroplasties in patients that wish to remain physically active in sports.

Background In total knee arthroplasty (TKA) periprosthetic joint infection (PJI), irrigation and debridement (I&D) with component retention is a treatment option with a wide variation in reported failure rates. The purpose of this study was to determine failure rates, outcomes, and factors that predict failure in I&D for TKA PJI. Methods A multicenter observational study of patients with a TKA PJI and subsequently undergoing an I&D with retention of components was conducted. The primary outcome was failure rate of I&D, where failure was defined as any subsequent surgical procedures. Results Two hundred sixteen cases of I&D with retention of components performed on 206 patients met inclusion criteria. The estimated long-term failure rate at 4 years was 57.4%. Time-to-event analyses revealed that the median survival time was 14.32 months. Five-year mortality was 19.9%. Multivariable modeling revealed that time symptomatic and organism were independent predictors of I&D failure. Culture-negative status had a higher hazard for failure than culture-positive patients. When primary organism and time symptomatic were selected to produce an optimized scenario for an I&D, the estimated failure rate was 39.6%. Conclusion I&D with retention of components has a high failure rate, and there is a high incidence of more complex procedures after this option is chosen. The patient comorbidities we investigated did not predict I&D success. Our results suggest that I&D has a limited ability to control infection in TKA and should be used selectively under optimum conditions.

Objective To evaluate whether knee contact force and knee pain are different between continuous and interval walking exercise in patients with knee osteoarthritis (OA). Methods Twenty seven patients with unilateral symptomatic knee OA completed two separate walking exercise sessions on a treadmill at 1.3 m/s on two different days: 1) a continuous 45 min walking exercise session, and 2) three 15 min bouts of walking exercise separated by 1 h rest periods for a total of 45 min of exercise in an interval format. Estimated knee contact forces using the OpenSim software and knee pain were evaluated at baseline (1st minute of walking) and after every 15 min between the continuous and interval walking conditions. Results A significant increase from baseline was observed in peak knee contact force during the weight-acceptance phase of gait after 30 and 45 min of walking, irrespective of the walking exercise condition. Additionally, whereas continuous walking resulted in an increase in knee pain, interval walking did not lead to increased knee pain. Conclusion Walking exercise durations of 30 min or greater may lead to undesirable knee joint loading in patients with knee OA, while performing the same volume of exercise in multiple bouts as opposed to one continuous bout may be beneficial for limiting knee pain.

Prosthetic joint infection should be considered as a possible diagnosis in any painful prosthetic joint at any time after the index procedure. Establishing a diagnosis of prosthetic joint infection can be challenging. Once the diagnosis is established, eradication of infection generally requires coordinated surgical and medical care. For a well-established infection, 2 stage revision arthroplasty is generally preferred by the authors. Static or articulating spacers can be used for the first stage.

Background Surgical site infection (SSI) after total joint arthroplasty (TJA) is a rare but devastating complication. Various skin antiseptic applications are used preoperatively to prevent SSI. Recent literature suggests 2% chlorhexidine gluconate (CHG) wipes reduce microbial content at surgical sites, but it is unclear whether they reduce rates of SSI.

Survival after solid organ transplants in the United States is increasing, and there is a need to understand the complications in knee arthroplasty patients who underwent organ transplantation. A retrospective study was conducted from 1993-2008 on 19 patients (23 knee arthroplasties) with previous successful solid organ transplants. Eleven knee arthroplasties were performed after renal transplantation, and 12 after nonrenal solid organ transplant (seven liver, four heart, one lung). Complications occurred in 9/23 patients (39.1%) and infections occurred in 4/23 patients (17.3%). Of the infected knees, two had MRSA, one had MSSA, and one Escherichia coli. Noninfectious complications (5/24, 21.7%) include aseptic loosening, quadriceps rupture, femoral fracture, hemarthrosis, and arthrofibrosis. All patients with complications were on immunosuppressant medications at the time of arthroplasty. There was a significantly higher rate of infection in the renal group compared to the non-renal group (P = 0.022). There was also a higher overall complication rate in the renal group however this did not reach significance.

Porous-coated metaphyseal sleeves are designed to fill bone defects and facilitate osseointegration when bone loss in encountered during revision total knee arthroplasty (TKA). The purpose of this study is to evaluate short-term results of porous-coated metaphyseal sleeves with regards to implant fixation and clinical outcomes. A retrospective review was conducted on 50 patients (79 sleeves—49 tibial and 30 femoral) who had a press-fit metaphyseal sleeve with revision TKA. Tibial and femoral bone loss was classified according to the Anderson Orthopaedic Research Institute (AORI) bone defect classification. Post-operative complications of infection, revision surgery, and dislocation were assessed. Follow-up radiographs were evaluated for signs of loosening using the criteria developed by the Knee Society. The median follow-up was 58.8 months (range 25.8–93.0 months). The bone loss classifications were 1 type 1, 30 type 2a, 2 type 2b, and 17 type 3, and with regards to the femur, 5 were type 1, 8 type 2a, 31 type 2b, and 6 type 3. At final follow-up, 41/45 (91.1%) tibial and 28/29 (96.6%) femoral sleeves showed radiographic evidence of ingrowth. Of these 69 patients, all showed radiographic evidence of bony ingrowth. Three sleeves were revised for infection and two for loosening. The re-operation rate for loosening was 5/74 (6.8%) and for any reason was 14/74 (18.9%). Modular porous-coated press fit metaphyseal sleeves fill defects and provide evidence of radiographic ingrowth. Short-term stable fixation can be achieved with sleeves, which is helpful as more patients undergo revision total knee arthroplasty with greater bone loss. Longer duration studies are needed to ascertain the survival rate of these implants. IV.

Computer-assisted total knee arthroplasty (TKA) has been implemented to improve the accuracy of implant positioning and limb alignment. Studies have shown several benefits of computer-assisted TKA over conventional TKA. However, the technology is not without potential pitfalls. The following article is a technique guide for the use of computer-assisted navigation for TKA.

The isolated effect of physical therapy (PT) on total joint arthroplasty hospital length of stay (LOS) has not been studied. A prospective cohort study was conducted on 136 primary total joint arthroplasties (58 hips, 78 knees). The LOS was determined by the operative start time until the time of discharge. On postoperative day (POD) 0, 60 joints remained in bed, 51 moved to a chair, and 25 received PT (22 ambulated, 3 moved to a chair). Length of stay differed for patients receiving PT on POD 0 (2.8 ± 0.8 days) compared with POD 1 (3.7 ± 1.8 days) (P = .02). There was no difference in PT treatment based on nausea/vomiting, pain levels, or discharge location. Isolated PT intervention on POD 0 shortened hospital LOS, regardless of the intervention performed.

Joint instability has been suggested as a risk factor for knee osteoarthritis and a cause of significant functional decline in those with symptomatic disease. However, the relationship between altered knee joint mechanics and self-reports of instability in individuals with knee osteoarthritis remains unclear.Fourteen subjects with knee osteoarthritis and complaints of joint instability and 12 control volunteers with no history of knee disease were recruited for this study. Dynamic stereo X-ray technology was used to assess the three-dimensional kinematics of the knee joint during the loading response phase of gait.Individuals with concurrent knee osteoarthritis and joint instability demonstrated significantly reduced flexion and internal/external rotation knee motion excursions during the loading response phase of gait (P0.01), while the total abduction/adduction range of motion was increased (P0.05). In addition, the coronal and transverse plane alignment of the knee joint at initial contact was significantly different (P0.05) for individuals with concurrent knee osteoarthritis and joint instability. However, the anteroposterior and mediolateral tibiofemoral joint positions at initial contact and the corresponding total joint translations were similar between groups during the loading phase of gait.The rotational patterns of tibiofemoral joint motion and joint alignments reported for individuals with concurrent knee osteoarthritis and joint instability are consistent with those previously established for individuals with knee osteoarthritis. Furthermore, the findings of similar translatory tibiofemoral motion between groups suggest that self-reports of episodic joint instability in individuals with knee osteoarthritis may not necessarily be associated with adaptive alterations in joint arthrokinematics.

Geratric patients who are treated operatively or nonoperatively for acetabular fractures may develop posttraumatic arthritis. Performing delayed total hip arthroplasties (THAs) in this patient population may be more technically challenging. Previous operative reports, radiographs, and computed tomography scans may help with preoperative planning. Scarring of the sciatic nerve from previous surgeries may warrant the use of nerve monitoring. Special surgical considerations include choosing a surgical approach, especially through preexisting incisions; deciding whether or not to remove hardware; and removing heterotopic ossification (HO). Multiple fixation options should be available in light of possible acetabular deficiency, including autograft, allograft, structural augments, and acetabular cups offering different fixation options. The postoperative management may differ from primary THAs performed for osteoarthritis because these patients may require protection of weight-bearing status and may require HO prophylaxis. By using the techniques described in this article, delayed THAs after acetabular fractures have demonstrated good outcomes in the geriatric patient population.

Prosthetic joint infection is an uncommon but serious complication of total knee arthroplasty (TKA). Control of infection after TKA is not always possible, and the resolution of infection may require an above-knee amputation (AKA). The purpose of this study was to determine the etiology of AKA and the functional outcomes of AKA after infected TKA. We retrospectively reviewed 35 patients who underwent AKA after an infected TKA. The amputations were performed an average of 6 years (range, 21 days to 24 years) after primary TKA. There were 19 females and 16 males with a mean age of 62 years (range, 26–88 years). Patient demographic information, comorbidities, surgical treatments, cultures, and culture sensitivities were recorded. Complications and functional status, including SF-12 and activities of daily living questionnaires, after AKA were also studied. The minimum followup was 7 months (mean, 39 months; range, 7–96 months). Two patients died secondary to cardiac arrest and 13 more died during the followup period of unrelated causes. Nine patients required irrigation and debridement for nonhealing wounds after AKA and two patients had repeat AKA for bony overgrowth. Of the 14 patients fitted for prostheses, eight were functionally independent outside of the home. Patients fitted with a prosthesis had higher mean activities of daily living scores (58 versus 38) and also tended to be younger with fewer comorbidities than those who were not fitted with a prosthesis. We found low functional status in living patients with an AKA after infection with only half of the patients walking after AKA. Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Key Points Question Can exercise programs delivered at a later stage (>2 months) after total knee replacement improve the functional limitations that persist after surgery? Findings In this randomized clinical trial of 240 individuals at a later stage after knee replacement, all arms (physical therapy, community, and control) improved physical function. There were no differences between arms in the primary outcome of patient-reported physical function, whereas the secondary outcome of performance-based physical function demonstrated greater improvement in the physical therapy arm. Meaning While the primary outcome suggests no benefit of later-stage exercise programs, the secondary outcomes suggest beneficial effects of physical therapy but require confirmation., This randomized clinical trial compares the effectiveness of later-stage exercise programs of clinic-based physical therapy exercise or community-based group exercise vs usual care after total knee replacement and explores heterogeneity of treatment effects., Importance Several functional limitations persist after total knee replacement (TKR). Intensive exercise programs could resolve these limitations but are not well tolerated by many patients until a later stage (>2 months) after surgery. Evidence for exercise at a later stage after TKR is limited. Objectives To compare the effectiveness of later-stage exercise programs after TKR and to explore heterogeneity of treatment effects. Design, Setting, and Participants Three-arm single-blind randomized clinical trial (January 7, 2015, to November 9, 2017) using an intent-to-treat approach with follow-ups at 3 months and 6 months. The setting was Allegheny County, Pennsylvania (an outpatient physical therapy clinic and 4 community centers). Participants had primary TKR performed more than 2 months previously, were 60 years or older, experienced moderate functional limitations, and were medically cleared to exercise. Interventions Clinic-based physical therapy exercise (physical therapy arm), community-based group exercise (community arm), and usual care (control arm). The control arm continued their usual care, whereas the exercise arms participated in supervised exercise programs lasting 12 weeks. Main Outcomes and Measures The primary outcome was arm differences in the Western Ontario and McMaster Universities Osteoarthritis Index–Physical Function (WOMAC-PF) at 3 months. The secondary outcomes included performance-based tests germane to knee replacement and additional surveys of physical function. Data were analyzed by linear mixed models and responder analysis. Results A total of 240 participants (mean [SD] age, 70 [7] years; 61.7% female) were allocated to physical therapy (n = 96), community exercise (n = 96), or control (n = 48). All 3 arms demonstrated clinically important improvement. At 3 months, between-arm analyses for the WOMAC-PF demonstrated no differences between physical therapy and community (−2.2; 98.3% CI, −4.5 to 0.1), physical therapy and control (−2.1; 98.3% CI, −4.9 to 0.7), and community and control (0.1; 98.3% CI, −2.7 to 2.9). Performance-based tests demonstrated greater improvement in the physical therapy arm compared with both the community (0.1 z score units; 98.3% CI, 0.0-0.2) and control (0.3 z score units; 98.3% CI, 0.1-0.4) arms and the community arm compared with the control arm (0.2 z score units; 98.3% CI, 0.0-0.3). The physical therapy arm had more than 17.7% responders than the community arm and more than 19.0% responders than the control arm. There was no difference in responder rates between the community and control arms. Conclusions and Relevance Based on the primary outcome, participation in late-stage exercise programs after TKR offered no benefit over usual care. The benefits of physical therapy identified by the secondary outcomes and responder analysis require confirmation. Trial Registration ClinicalTrials.gov Identifier: NCT02237911

The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO) characterizes the radiation environment to be experienced by humans during future lunar missions. CRaTER measures the effects of ionizing energy loss in matter due to penetrating solar energetic protons (SEP) and galactic cosmic rays (GCR), specifically in silicon solid-state detectors and after interactions with tissue-equivalent plastic (TEP), a synthetic analog of human tissue. The CRaTER investigation quantifies the linear energy transfer (LET) spectrum in these materials through direct measurements with the lunar space radiation environment, particularly the interactions of ions with energies above 10 MeV, which penetrate and are detected by CRaTER. Combined with models of radiation transport through materials, CRaTER LET measurements constrain models of the biological effects of ionizing radiation in the lunar environment as well as provide valuable information on radiation effects on electronic systems in deep space. In addition to these human exploration goals, CRaTER measurements also provide new insights on the spatial and temporal variability of the SEP and GCR populations and their interactions with the lunar surface. We present here an overview of the CRaTER science goals and investigation, including: an instrument description; observation strategies; instrument testing, characterization, and calibration; and data analysis, interpretation, and modeling plans., United States. National Aeronautics and Space Administration (contract NNG05EB92C)

This article refutes the need for the posterior incision in minimally invasive two-incision total hip replacement. A description of how the Smith-Petersen, direct anterior, approach can be used to expose and implant the femoral components is given. Data from a prospective comparison of direct anterior and modified Hardinge approaches is presented. Seventy-nine patients in matched groups were analyzed. There was no difference between the groups in average body mass index, surgical time, incision length, hospital stay, pain, blood loss, or complications. At the six-month follow up evaluation slightly better outcomes were seen for the direct anterior approach when compared to the direct lateral approach. Limiting exposure to the anterior incision eliminates soft tissue and muscular damage. Other concerns such as intraoperative fractures, stem malpositioning, and prolonged surgeries are not seen with the direct anterior technique. Minimally invasive total hip arthroplasty can be performed safely with excellent results using the direct anterior incision alone.

Background: Exchange reamed nailing of the tibia is a common procedure in the treatment of an aseptic tibial nonunion. However, reports in the literature supporting this technique are limited. Methods: Forty patients with a tibial nonunion after initial unreamed intramedullary nailing were retrospectively assessed after an exchange reamed nailing. The main outcome measurements included radiographic and clinical union as well as time from exchange reamed nailing to union. Results: Thirty-eight patients achieved union of their fracture (95%). The average time from exchange nailing to union was 29 ± 21 weeks. Complications included one deep vein thrombosis (2.5%) and two hardware failures (5%). Conclusion: Exchange reamed nailing for nonunions of the tibia results in a high union rate and is associated with a low complication rate. This technique is recommended as a standard procedure for aseptic tibial nonunions after initial unreamed intramedullary nailing.

Both total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA) are used to treat unicompartmental knee osteoarthrosis. Traditionally, TKA was believed to be a better option due to its durability, inclusive patient selection, and robust long-term data on its effectiveness to reduce pain and restore function (1). UKA was initially controversial. Studies conducted from the 1950s to the 1990s reported inconsistent results about the benefits of this surgical procedure (2).

The incidence of patella baja in total knee arthroplasty (TKA) revisions for aseptic and septic causes is not well defined. We retrospectively reviewed 101 mobile-bearing TKA revisions performed between 2003 and 2009. Aseptic (n=67) and septic (n=34) revisions were compared for patella baja. A nonarticulating spacer was used as the initial treatment for infected cases. The Insall-Salvati ratio was radiographically measured before surgery (preexplant for septic revisions) and at latest follow-up (postreplant for septic revisions). Mean (SD) Insall-Salvati ratio did not differ between groups before surgery, 1.00 (0.25) for aseptic and 0.96 (0.22) for septic, but differed significantly after surgery, 0.99 (0.23) for aseptic and 0.77 (0.24) for septic. After correcting for preoperative patellar height, there was a statistically significant postoperative difference between aseptic cases, 1.09 (0.19), and septic cases, 0.82 (0.21). There was also a significant difference in mean (SD) postoperative range of motion (ROM) between aseptic cases, 108.0° (20.7°), and septic cases, 92.2° (34.6°), and decreased ROM between cases with patella baja, 95.1° (31.6°) and cases without patella baja, 106.8° (23.6°). TKA revisions done for septic causes using a nonarticulating spacer resulted in a higher incidence of patella baja and decreased ROM.

Background To evaluate knee joint contact mechanics and kinematics during the loading response phase of downhill gait in knee osteoarthritis patients with self-reported instability. Methods Forty-three subjects, 11 with medial compartment knee osteoarthritis and self-reported instability (unstable), 7 with medial compartment knee osteoarthritis but no reports of instability (stable), and 25 without knee osteoarthritis or instability (control) underwent Dynamic Stereo X-ray analysis during a downhill gait task on a treadmill. Findings The medial compartment contact point excursions were longer in the unstable group compared to the stable (P = 0.046) and the control groups (P = 0.016). The peak medial compartment contact point velocity was also greater for the unstable group compared to the stable (P = 0.047) and control groups (P = 0.022). Additionally, the unstable group demonstrated a coupled movement pattern of knee extension and external rotation after heel contact which was different than the coupled motion of knee flexion and internal rotation demonstrated by stable and control groups. Interpretation Our findings suggest that knee joint contact mechanics and kinematics are altered during the loading response phase of downhill gait in knee osteoarthritis patients with self-reported instability. The observed longer medial compartment contact point excursions and higher velocities represent objective signs of mechanical instability that may place the arthritic knee joint at increased risk for disease progression. Further research is indicated to explore the clinical relevance of altered contact mechanics and kinematics during other common daily activities and to assess the efficacy of rehabilitation programs to improve altered joint biomechanics in knee osteoarthritis patients with self-reported instability.

Above-the-knee amputation (AKA) is a last-resort surgical option for the treatment of periprosthetic joint infection (PJI) with resistant organisms or with recurrent infections. Certain circumstances are unique to performing AKAs after total knee arthroplasty (TKA). When performing an AKA, the factors that require special attention include the indications for surgery, presentation and comorbidities, level of amputation, possible prosthesis removal, and potential complications. This chapter includes a discussion of the surgical techniques, postoperative stump care, options for prostheses, functional status, and long term follow up after AKA. This chapter provides comprehensive and relevant information for assessing, performing, and treating AKA patients after infected TKAs.

Cartilage damaged by trauma has a limited capacity to regenerate. Current methods for treating small chondral defects include palliative treatment with arthroscopic debridement and lavage, reparative treatment with marrow stimulation techniques (e.g. microfracture), and restorative treatment, including osteochondral grafting and autologous chondrocyte implantation. Larger defects are treated by osteochondral allografting or total joint replacements. However, the future of treating cartilage defects lies in providing biologic solutions through cartilage regeneration. Laboratory and clinical studies have examined the treatment of larger lesions using tissue engineered cartilage. Regenerated cartilage can be derived from various cell types, including chondrocytes, mesenchymal stem cells, and pluripotent stem cells. Common scaffolding materials include proteins, carbohydrates, synthetic materials, and composite polymers. Scaffolds may be woven, spun into nanofibers, or configured as hydrogels. Chondrogenesis may be enhanced with the application of chondroinductive growth factors. Finally, bioreactors are being developed to enhance nutrient delivery and provide mechanical stimulation to tissue-engineered cartilage ex vivo. The multi-disciplinary approaches currently being developed to produce cartilage promise to bring the dream of cartilage regeneration in clinical use to reality.

Staphylococcus decolonization prior to surgery is used to prevent surgical site infections (SSIs) after total joint arthroplasty (TJA). To determine if current treatment protocols result in successful decolonization of methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA), 106 consecutive patients were screened for nasal MSSA/MRSA colonization pre-operatively and on the day of surgery. Colonized patients used intranasal mupirocin twice a day and chlorhexidine showers daily 5 days prior to surgery. Pre-operatively, 24 joints (22.0%) were positive for MSSA colonization and 5 joints (4.6%) were positive for MRSA colonization. On the day of surgery, 3 joints (2.8%) who underwent decolonization were positive for MSSA colonization and 0 joints were positive for MRSA colonization. The reduction in MSSA colonization was significant (P