Neutrophil to Lymphocyte Ratio as an Indicator of Periprosthetic Joint Infection: A Retrospective Cohort Study

INTRODUCTION

Periprosthetic joint infection (PJI) after total joint arthroplasty (TJA) is a serious complication posing notable clinical implications for patients and substantial economic burdens. Neutrophil to lymphocyte ratio (NLR) is an emerging biomarker of inflammation, which may better predict PJI. The objective of this review was to evaluate NLR changes in patients with confirmed PJI, to compare NLR between an aseptic revision and a revision for PJI, and to establish whether an NLR of 2.45 is an appropriate cutoff for predicting infection.

METHODS

A retrospective review of patients who underwent revision TJA for PJI at a single center between January 1, 2005, and December 31, 2018, was performed and compared with an aseptic cohort who underwent aseptic revision TJA. NLR was calculated from complete blood counts performed at index surgery and at the time of revision surgery. Receiver operating characteristic curves were analyzed, along with sensitivity, specificity, and positive and negative likelihood ratios.

RESULTS

There were 89 patients included in each cohort. Mean NLR in patients who underwent revision for PJI was 2.85 (± 1.27) at the time of index surgery and 6.89 (± 6.64) at the time of revision surgery ( P = 0.017). Mean NLR in patients undergoing revision for PJI (6.89) was significantly higher than aseptic revisions (3.17; P < 0.001).

DISCUSSION

In patients who underwent revision surgery for PJI, NLR was markedly elevated at time of revision compared with the time of index surgery. Because it is a cost-effective and readily available test, these findings suggest that NLR may be a useful triage test in the diagnosis of PJI.

LEVEL OF EVIDENCE

Level III Diagnostic Study.

Factual corrections: Concerns and current evidence

Factual corrections that target misinformation improve belief accuracy. They do so across a wide variety of countries, political beliefs and demographic characteristics. Instances of backfire, wherein exposure to corrections reduce accuracy, are exceedingly rare and may be an artifact of research design. The evidence regarding other common concerns is mixed. While the effects on corrections on belief are not permanent, they are not entirely ephemeral, either. With some exceptions, corrections mostly only affect belief accuracy, with minor to nonexistent influence on downstream attitudes and behaviors. While corrections are not unpopular among the public, limited available evidence suggests that those who see misinformation are exceedingly unlikely to see relevant corrections.

Management of Greater Trochanteric Pain Syndrome After Total Hip Arthroplasty: Practice Patterns and Surgeon Attitudes

INTRODUCTION

Greater trochanteric pain syndrome (GTPS) or trochanteric bursitis is described as pain on the lateral side of the hip that does not involve the hip joint and can be elicited clinically by palpation over the greater trochanter. To date, there remains no consensus on clinical guidelines for either diagnosis or management of GTPS.

METHODS

To understand the practice patterns, beliefs, and attitudes relating to the management of GTPS after total hip arthroplasty, a survey was developed and completed by Canadian arthroplasty surgeons. The final survey consisted of 23 questions divided into three sections: 1) screening questions; 2) demographic information; and 3) practice patterns, attitudes, and beliefs.

RESULTS

Most surgeons use physical examination alone for diagnosis. A detailed analysis indicates that surgeons primarily treat GTPS with oral anti-inflammatories (57.1%), structured physiotherapy (52.4%), and steroid injections (45.2%). Management options are typically nonsurgical and comprise a combination of either unstructured or targeted physiotherapy, corticosteroid injections, or platelet-rich plasma.

DISCUSSION

There remains an absence of clinical consensus for the diagnosis and management of GTPS after total hip arthroplasty. Physical examination is most often relied on, regardless of the availability of imaging aids. While common treatments of GTPS were identified, up to one-third of patients fail initial therapy.

Global taxonomic, functional, and phylogenetic diversity of bees in apple orchards

An essential prerequisite to safeguard pollinator species is characterisation of the multifaceted diversity of crop pollinators and identification of the drivers of pollinator community changes across biogeographical gradients. The extent to which intensive agriculture is associated with the homogenisation of biological communities at large spatial scales remains poorly understood. In this study, we investigated diversity drivers for 644 bee species/morphospecies in 177 commercial apple orchards across 33 countries and four global biogeographical biomes. Our findings reveal significant taxonomic dissimilarity among biogeographical zones. Interestingly, despite this dissimilarity, species from different zones share similar higher-level phylogenetic groups and similar ecological and behavioural traits (i.e. functional traits), likely due to habitat filtering caused by perennial monoculture systems managed intensively for crop production. Honey bee species dominated orchard communities, while other managed/manageable and wild species were collected in lower numbers. Moreover, the presence of herbaceous, uncultivated open areas and organic management practices were associated with increased wild bee diversity. Overall, our study sheds light on the importance of large-scale analyses contributing to the emerging fields of functional and phylogenetic diversity, which can be related to ecosystem function to promote biodiversity as a key asset in agroecosystems in the face of global change pressures.

Elevated rates of dietary generalization in eusocial lineages of the secondarily herbivorous bees

BACKGROUND

Within the Hymenoptera, bees are notable for their relationship with flowering plants, being almost entirely dependent on plant pollen and nectar. Though functionally herbivorous, as a result of their role as pollinators, bees have received comparatively little attention as models for insect herbivory. Bees often display dietary specialization, but quantitative comparison against other herbivorous insects has not previously been conducted.

RESULTS

In the most comprehensive analysis to date for 860 bee species, dietary specialization amounted to 50.1% of studied species collecting pollen from between 1 and 2 botanical families with a relatively long tail of dietary generalists, with 11.1% of species collecting from more than 10 botanical families. This distribution deviated from the truncated Pareto distribution of dietary breadth seen in other herbivorous insect lineages. However, this deviation was predominantly due to eusocial bee lineages, which show a range of dietary breadths that conformed to a normal distribution, while solitary bees show a typical truncated distribution not strongly different from other herbivorous insects. We hypothesize that the relatively low level of dietary specialization in bees as a whole reflects the relaxation of the constraints typically observed in herbivorous insects with a comparatively reduced importance of plant chemistry and comparatively increased importance of phenology and foraging efficiency. The long flight periods of eusocial bees that are necessary to allow overlapping generations both allows and necessitates the use of multiple flowering resources, whereas solitary bees with short flight periods have more limited access to varied resources within a constrained activity period.

CONCLUSIONS

Collectively, solitary bees show slightly lower specialization compared to other herbivorous insects, possibly due to their balanced relationship with plants, rather than direct antagonism such as seen in the direct consumption of plant tissues. An additional factor may be the mediocre diversity of bees at low latitudes combined with low levels of dietary specialization, whereas these areas typically display a high rate of specialization by herbivorous insects in general. Though the most important factors structuring dietary specialization in bees appear to differ from many other herbivorous insects, solitary bees show a surprisingly similar overall pattern of dietary specialization.

Marginalization Influences Access, Outcomes, and Discharge Destination Following Total Joint Arthroplasty in Canada's Universal Healthcare System

BACKGROUND

The influence of socioeconomic status on outcomes following total joint arthroplasty (TJA) in the Canadian single-payer healthcare system is yet to be elucidated. The objective of the present study was to evaluate the impact of socioeconomic status on TJA outcomes.

METHODS

This was a retrospective review of 7,304 consecutive TJA (4,456 knees and 2,848 hips) performed between January 1, 2001 and December 31, 2019. The primary independent variable was the average census marginalization index. The primary dependent variable was functional outcome scores.

RESULTS

The most marginalized patients in both the hip and knee cohorts had significantly worse preoperative and postoperative functional scores. Patients in the most marginalized quintile (V) showed a decreased odds of achieving a minimal important difference in functional scores at 1-year follow-up (odds ratio [OR] 0.44; 95% confidence interval [CI] [0.20, 0.97], P = .043). Patients in the knee cohort in the most marginalized quintiles (IV and V) had increased odds of being discharged to an inpatient facility with an OR of 2.07 (95% CI [1.06, 4.04], P = .033) and OR of 2.57 (95% CI [1.26, 5.22], P = .009), respectively. Patients in the hip cohort in V quintile (most marginalized) had increased odds of being discharged to an inpatient facility with an OR of 2.24 (95% CI [1.02, 4.96], P = .046).

CONCLUSION

Despite being a part of the Canadian universal single-payer healthcare system, the most marginalized patients had worse preoperative and postoperative function, and had increased odds of being discharged to another inpatient facility.

LEVEL OF EVIDENCE

IV.

Limited introgression from non-native commercial strains and signatures of adaptation in the key pollinator Bombus terrestris

Insect pollination is fundamental for natural ecosystems and agricultural crops. The bumblebee species Bombus terrestris has become a popular choice for commercial crop pollination worldwide due to its effectiveness and ease of mass rearing. Bumblebee colonies are mass produced for the pollination of more than 20 crops and imported into over 50 countries including countries outside their native ranges, and the risk of invasion by commercial non-native bumblebees is considered an emerging issue for global conservation and biological diversity. Here, we use genome-wide data from seven wild populations close to and far from farms using commercial colonies, as well as commercial populations, to investigate the implications of utilizing commercial bumblebee subspecies in the UK. We find evidence for generally low levels of introgression between commercial and wild bees, with higher admixture proportions in the bees occurring close to farms. We identify genomic regions putatively involved in local and global adaptation, and genes in locally adaptive regions were found to be enriched for functions related to taste receptor activity, oxidoreductase activity, fatty acid and lipid biosynthetic processes. Despite more than 30 years of bumblebee colony importation into the UK, we observe low impact on the genetic integrity of local B. terrestris populations, but we highlight that even limited introgression might negatively affect locally adapted populations.

Routine use of antibiotic-laden bone cement in total knee arthroplasty is a cost-effective practice in the single-payer healthcare system

PURPOSE

The purpose of this study was to determine the cost-effectiveness of antibiotic-laden bone cement (ALBC) in primary total knee arthroplasty (TKA) from the perspective of a single-payer healthcare system.

METHODS

A cost-utility analysis (CUA) was performed over a 2-year time horizon comparing primary TKA with either ALBC or regular bone cement (RBC) from the perspective of the single-payer Canadian healthcare system. All costs were in 2020 Canadian dollars. Health utilities were in the form of quality-adjusted life years (QALYs). Model inputs for cost, utilities and probabilities were derived from the literature as well as regional and national databases. One-way deterministic sensitivity analysis was performed.

RESULTS

Primary TKA with ALBC was found to be more cost-effective compared to primary TKA with RBC with an incremental cost-effectiveness ratio (ICER) of -3,637.79 CAD/QALY. The use of routine ALBC remained cost-effective even with cost increases of up to 50% per bag of ALBC. TKA with ALBC was no longer cost-effective if the rate of PJI following this practice increased 52%, or the rate of PJI following the use of RBC decreased 27%.

CONCLUSIONS

The routine use of ALBC in TKA is a cost-effective practice in the single-payer Canadian healthcare system. This remains to be the case even with a 50% increase in the cost of ALBC. Policy makers and hospital administrators of single-payer healthcare systems can leverage this model to inform their local funding policies. Future prospective reviews and randomized controlled trials from the perspective of various healthcare models can further shed light on this issue.

LEVEL OF EVIDENCE

III.

The new annotated checklist of the wild bees of Europe (Hymenoptera: Anthophila)

At a time when nature conservation has become essential to ensure the long-term sustainability of our environment, it is widely acknowledged that conservation actions must be implemented within a solid taxonomic framework. In preparation for the upcoming update of the IUCN Red List, we here update the European checklist of the wild bees (sensu the IUCN geographical framework). The original checklist, published in 2014, was revised for the first time in 2017. In the present revision, we add one genus, four subgenera and 67 species recently described, 40 species newly recorded since the latest revision (including two species that are not native to Europe), 26 species overlooked in the previous European checklists and 63 published synonymies. We provide original records for eight species previously unknown to the continent and, as original taxonomic acts, we provide three new synonyms, we consider two names as nomina nuda, ten names as nomina dubia, three as species inquirenda, synonymize three species and exclude 40 species from the previous checklist. Around a hundred other taxonomic changes and clarifications are also included and discussed. The present work revises the total number of genera for IUCN Europe to 77 and the total number of species to 2,138. In addition to specifying the taxonomic changes necessary to update the forthcoming Red List of European bees, we discuss the sampling and taxonomic biases that characterise research on the European bee fauna and highlight the growing importance of range expansions and species invasions.

Correcting COVID-19 vaccine misinformation in 10 countries

What can be done to reduce misperceptions about COVID-19 vaccines? We present results from experiments conducted simultaneously on YouGov samples in 10 countries (N = 10 600), which reveal that factual corrections consistently reduce false beliefs about vaccines. With results from these 10 countries, we find that exposure to corrections increases belief accuracy by 0.16 on a 4-point scale, while exposure to misinformation decreases belief accuracy by 0.09 on the same scale. We are unable to find evidence that either misinformation or factual corrections affect intent to vaccinate or vaccine attitudes. Our findings on effect duration are less conclusive; when we recontacted participants two weeks later, we observed 39% of the initial accuracy increase, yet this result narrowly misses conventional thresholds of statistical significance (p = 0.06). Taken together, our results illustrate both the possibilities and limitations of factual corrections. Evidence from 10 highly diverse populations shows that exposure to factual information reduces belief in falsehoods about vaccines, but has minimal influence on subsequent behaviours and attitudes.

Efficacy of hydrofibre dressing following total joint arthroplasty: a meta-analysis of randomised controlled trials

INTRODUCTION

In the United States, over 1,000,000 total joint arthroplasty (TJA) surgeries are performed annually and has been forecasted that this number will exceed 4,000,000 by the year 2030. Many different types of dressing exist for use in TJA surgery, and it is unclear if any of the newer, hydrofibre dressings are superior to traditional dressings at reducing rates of infections or improving wound healing. Thus, the aim of this systematic review and meta-analysis was to assess the impact of hydrofiber dressings on reducing complications.

METHODS

A systematic review and meta-analysis was performed using the online databases MEDLINE and the Cochrane Library. Randomized controlled trials (RCTs) comparing hydrofibre dressings to a standard dressing were included. Summary measures are reported as odds ratios (ORs) and mean differences (MDs) with 95% confidence intervals (CIs). Our primary outcome was prosthetic joint infection (PJI). Secondary outcomes included blisters, dressing changes and wound irritation.

RESULTS

5 RCTs were included. Hydrofibre dressing had no observable effect on PJI or wound irritation (OR 0.53; 95% CI, 0.14-1.98; p = 0.35). Hydrofibre dressings reduced the rate of blisters (OR 0.36; 95% CI, 0.14-0.90; p = 0.03) and number of dressing changes (MD -1.89; 95% CI, -2.68 to -1.11).

CONCLUSIONS

In conclusion, evidence suggests hydrofibre dressings have no observable effect on PJI and wound irritation. Evidence for reduction in blisters and number of dressings is modest given wide CIs and biased trial methodologies. Use of hydrofibre dressings should be considered inconclusive for mitigating major complications in light of current best evidence.

Risk factors for recurrence of periprosthetic joint infection following operative management: a cohort study with average 5-year follow-up

Background

Periprosthetic joint infections (PJIs) remain challenging to eradicate even after surgical management, which in most cases involves either debridement, antibiotics and implant retention (DAIR) or single- or two-staged revision. The purpose of this study is to determine predictors of PJI recurrence after operative management for PJI, and to determine differences in recurrence-free survival between DAIR and staged revision.

Methods

This is a retrospective analysis of prospectively collected data of revision hip and knee arthroplasty surgeries due to PJI between 2011 and 2018 at an academic hospital. Any patient undergoing revision surgery for PJI was included except if the index surgery information was unknown. The primary outcome was confirmed PJI recurrence. Multivariable logistic regression analysis was utilized to determine the relationship between the predictor variables and outcome variable. Log rank testing was used to compare recurrence-free survival between DAIR and staged revision.

Results

A total of 89 patients (91 joints) underwent revision surgery due to PJI. Younger age and presence of a sinus tract were statistically significant for risk of PJI recurrence. A multivariable logistic regression model including both variables was significant for predicting recurrence of PJI (χ2=10.2, P=0.006). Survival was not significantly different between patients who underwent DAIR versus a staged revision.

Conclusions

Younger patients and those with a chronic sinus tract are at significantly higher risk of recurrent PJI. This study also demonstrated that PJI can be successfully managed in the majority of cases with DAIR or staged revision.

The quality of diagnostic studies used for the diagnostic criteria of periprosthetic joint infections

BACKGROUND

Although periprosthetic joint infection (PJI) is a serious complication following a total joint arthroplasty procedure, there remains uncertainty regarding the diagnosis of PJI due to the lack of a globally accepted, standardized definition. The goal of this review is to critically analyze the quality of the evidence used for the novel 2018 MSIS PJI definition and identify gaps and limitations with using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool.

METHODS

References from the modified 2018 MSIS definition for PJI by Parvizi et al. were retrieved and manually reviewed. A total of 11 studies were assessed using a validated QUADAS-2 tool.

RESULTS

Many included studies had an unclear or high risk of bias for the Index Test domain due to a lack of blinding and lack of prespecified thresholds. A majority of studies utilized Youden's J statistic to optimize the thresholds which may diminish external validity. Likewise, several studies were assessed to have an unclear and high risk of bias for the Flow and Timing domain primarily due to a lack of reporting and a large number of exclusions. Overall, there was a low risk of bias for the choice of reference standard, its conduct and interpretation, as well as for the Patient Selection domain.

CONCLUSION

Although the literature used for the MSIS 2018 PJI definition is fraught with potential sources of bias, there may be a trend toward an improvement in the quality of evidence when compared to the earlier definition of PJI.

Causes and predictors of failed same-day home discharge following primary hip and knee total joint arthroplasty: a Canadian perspective

PURPOSE

Same-day home (SDH) discharge in total joint arthroplasty (TJA) has increased in popularity in recent years. The objective of this study was to evaluate the causes and predictors of failed discharges in planned SDH patients.

METHODS

A consecutive cohort of patients who underwent total knee (TKA) or total hip arthroplasty (THA) that were scheduled for SDH discharge between 01 April 2019 and 31 March 2021 were retrospectively reviewed. Patient demographics, causes of failed discharge, perioperative variables, 30-day readmissions and 6-month reoperation rates were collected. Multivariate regression analysis was undertaken to identify independent predictors of failed discharge.

RESULTS

The cohort consisted of 527 consecutive patients. 101 (19%) patients failed SDH discharge. The leading causes were postoperative hypotension (20%) and patients who were ineligible for the SDH pathway (19%). 2 individual surgeons, later operative start time (OR 1.3; 95% CI, 1.15-1.55; p = 0.001), ASA class IV (OR 3.4; 95% CI, 1.4-8.2; p = 0.006) and undergoing a THA (OR 2.0; 95% CI, 1.2-3.1, p = 0.004) were independent predictors of failed SDH discharge. No differences in age, BMI, gender, surgical approach or type of anaesthetic were found (p > 0.05). The 30-day readmission or 6-month reoperation were similar between groups (p > 0.05).

CONCLUSIONS

Hypotension and inappropriate patient selection were the leading causes of failed SDH discharge. Significant variability existed between individual surgeons failed discharge rates. Patients undergoing a THA, classified as ASA IV or had a later operative start time were all more likely to fail SDH discharge.

Diversity and Relative Abundance of Insect Pollinators in Moroccan Agroecosystems

Agroecosystems are often impoverished ecosystems, but they can host diverse communities of insects which provide ecosystem services. Specifically, crops may benefit from insect pollinators that increase their quantity and quality of yields. Basic knowledge is still needed regarding the identity, diversity, abundance, and ecology of insect pollinators in many parts of the world, especially in low and middle-income countries. In this study we investigate the potential of agroecosystems and crops in Morocco to host a high diversity of insect pollinators. We sampled insects in four eco-climatic regions encompassing a total of 22 crops for 2 years (2018–2019). After describing the general pattern of diversity and abundance of insect pollinators, we focused our comparative analyses on bees as they are known to be the most efficient and abundant group of insect pollinators. We recorded a total of 53,361 insect pollinators in all agroecosystems among which 37,091 were visiting crop flowers. Bees were by far the most abundant group visiting crops. Honeybees represented 49% of crop visitors followed by wild bees representing 33% of relative abundance. Three genera (Lasioglossum, Andrena, and Xylocopa) represented 53% of the total abundance of wild bees visiting crops. We identified a total of 213 species visiting crops (22% of national wild bee species richness). A comparison of the abundance, species richness, and community composition of wild bees visiting the same crops showed significant inter-regional differences for zucchini, faba bean, and eggplant. This study highlights the high diversity of pollinators in Moroccan agroecosystems and represents an important step toward exploring the Moroccan pollinator fauna. It provides basic information for future studies on pollinator conservation and pollination services.

Intermediate to Long-Term Outcomes and Causes of Aseptic Failure of an At-Risk Femoral Stem

BACKGROUND

The Accolade TMZF is a tapered-wedge cementless metaphyseal-coated femoral stem that was widely utilized from 2002 to 2012. In recent years, there have been reports of early catastrophic failure of this implant. The purposes of the present study were to establish the long-term survival of this stem and to analyze patients who underwent aseptic revision to understand the causes and risk factors for failure.

METHODS

We retrospectively reviewed the records of all patients who had undergone primary total hip arthroplasty with use of an Accolade TMZF stem at a high-volume arthroplasty center. The causes and timing of revision surgery were documented. Survivorship analysis was performed with use of Kaplan-Meier curves to determine the overall and aseptic survival rates at the time of the latest follow-up. Patient and implant factors commonly associated with aseptic failure were extracted, and a Cox proportional hazards model was used.

RESULTS

A consecutive series of 2,609 patients who had undergone unilateral primary total hip arthroplasty with use of an Accolade TMZF femoral stem were included. The mean time from the primary procedure was 11.3 years (range, 0 days to 19.4 years). The cumulative survival rate was 95.5% ± 0.1% at the time of the latest follow-up. One hundred and seven patients underwent revision surgery, with aseptic loosening of the femoral component being the most common cause of aseptic failure in this cohort (33 of 2,609; 1.3%). Smaller femoral size and larger femoral head offset were independent risk factors for aseptic failure.

CONCLUSIONS

To our knowledge, this is the largest series representing the longest follow-up of this tapered-wedge cementless femoral implant. Despite early concerns, the Accolade TMZF stem had excellent survivorship in this cohort. Trunnionosis as the cause for revision surgery was rare.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Diagnosing Periprosthetic Joint Infection: a Scoping Review

PURPOSE OF REVIEW

The goal of this review is to provide an up to date understanding of the utility and limitations of the current tests utilized in the diagnosis of periprosthetic joint infection (PJI) in total knee and hip arthroplasty.

RECENT FINDINGS

Despite the growth in literature surrounding PJI diagnosis, there remains challenges in establishing a diagnosis of PJI. A combination of clinical, serum, and synovial tests and microbiologic and histologic examinations can yield a diagnosis in the majority of cases. Novel molecular and imaging studies may be beneficial for indeterminant cases. A number of emerging diagnostic tests have been proposed and may be incorporated into diagnostic algorithms in the future. Recently proposed stepwise diagnostic algorithms have shown high sensitivity and specificity. The diagnosis of PJI remains challenging due to a lack of tests that can definitively rule out infection. Diagnosis and investigations should occur in a stepwise fashion. There has been a plethora of new diagnostic tests introduced in attempts to improve the accuracy of diagnostic algorithms. The definition and algorithms for the diagnoses of PJI will continue to evolve as new techniques and tests are introduced.

Are Functional Outcomes of a Total Hip Arthroplasty Predictive of a Contralateral Total Hip Arthroplasty: A Retrospective Cohort Study

BACKGROUND

Current literature suggests that 8%-35% of patients undergoing total hip arthroplasty (THA) undergo a subsequent contralateral THA. This study aims to determine if functional outcomes after primary THA predict outcomes in the subsequent primary THA of the contralateral side.

METHODS

A retrospective cohort of patients undergoing staged bilateral primary THA was reviewed. The Oxford Hip Score (OHS) was utilized as the functional outcome measurement tool and was assessed preoperatively and at one year postoperatively. The minimal clinically important difference (MCID) was assessed. Based on the first-side THA one-year outcomes, the odds of maintaining an MCID, or not, for the second-side THA were determined.

RESULTS

The study cohort consisted of 551 patients and 1102 primary THAs. The average postoperative OHSs were similar after the first and second THA. Patients achieving the MCID with the first-side surgery were 2.6 times (95% confidence interval 1.0 to 6.64, P = .04) more likely to achieve the MCID for the second-side surgery than patients failing to reach the MCID for their first-side surgery. After the first THA, 29 (5.3%) patients failed to reach the predefined MCID for the OHS compared with 54 (9.8%) patients undergoing their second THA (odds ratio: 1.96 [95% confidence interval: 1.23 to 3.1], χ² = 8.14, P = .005).

CONCLUSIONS

Functional outcomes after the first THA are predictive of functional outcomes of the second THA. Patients are more likely to achieve a clinically significant improvement after their first THA related to higher preoperative OHSs before the second THA.

Unicompartmental Knee Arthroplasty: Survivorship and Risk Factors for Revision: A Population-Based Cohort Study with Minimum 10-Year Follow-up

BACKGROUND

Operative management for end-stage knee osteoarthritis (OA) primarily consists of arthroplasty. Total knee arthroplasty (TKA) is the so-called gold standard for multicompartmental OA. In selected patients, specifically those with unicompartmental OA and no definite contraindications, realignment osteotomies and unicompartmental knee arthroplasty (UKA) are viable options. UKA offers several advantages over TKA, including preservation of both cruciate ligaments, faster recovery, and less osseous resection. The purpose of this study was to determine the survivorship of UKAs and risk factors for all-cause revision surgery in patients with a minimum follow-up of 10 years in a large population-based database.

METHODS

We performed a population-based cohort study using linked administrative databases in Ontario, Canada. We identified all UKAs performed from January 2002 through December 2006. All patients had a minimum 10-year follow-up. Demographic data and outcomes were summarized using descriptive statistics. We used a Cox proportional hazards model with the Fine and Gray method accounting for competing risks such as death to analyze the effect of surgical and patient factors on the risk of revision of UKA.

RESULTS

A total of 4,385 patients were identified as having undergone primary UKA from 2002 through 2006 in Ontario. Of these patients, 779 underwent revision surgery, for a cumulative risk for all-cause revision of 16.5% at 10 years (95% confidence interval [CI]: 15.4% to 17.7%). Mechanical loosening was the reason for 83.4% of all revisions. Male sex, diabetes, an age younger than 50 years, and cementless implants were significant risk factors for revision surgery. Residence in a rural or urban setting, income quintile, discharge destination, and type of OA were not associated with the risk of revision. Survivorship at 1, 5, 10, and 15 years was 97.2%, 90.5%, 83.5%, and 81.9%, respectively.

CONCLUSIONS

This study demonstrated a >80% long-term survivorship for UKA based on a large administrative database sample and identified important risk factors for failure including male sex, younger age, diabetes, and cementless fixation. This study found rates of survivorship similar to those previously reported in the literature, while identifying key risk factors for failure. Patient selection has always been identified as a key factor in ensuring successful UKA, and the risk factors identified in this study may help guide decision-making for surgeons and patients dealing with unicompartmental knee OA.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Phenology and flowering overlap drive specialisation in plant-pollinator networks

Variation in dietary specialisation stems from fundamental interactions between species and their environment. Consequently, understanding the drivers of this variation is key to understanding ecological and evolutionary processes. Dietary specialisation in wild bees has received attention due to their close mutualistic dependence on plants, and because both groups are threatened by biodiversity loss. Many principles governing pollinator specialisation have been identified, but they remain largely unvalidated. Organismal phenology has the potential to structure realised specialisation by determining concurrent resource availability and pollinator foraging activity. We evaluate this principle using mechanistic models of adaptive foraging in pollinators within plant-pollinator networks. While temporal resource overlap has little impact on specialisation in pollinators with extended flight periods, reduced overlap increases specialisation as pollinator flight periods decrease. These results are corroborated empirically using pollen load data taken from bees with shorter and longer flight periods across environments with high and low temporal resource overlap.

Expanding insect pollinators in the Anthropocene

Global changes are severely affecting pollinator insect communities worldwide, resulting in repeated patterns of species extirpations and extinctions. Whilst negative population trends within this functional group have understandably received much attention in recent decades, another facet of global changes has been overshadowed: species undergoing expansion. Here, we review the factors and traits that have allowed a fraction of the pollinating entomofauna to take advantage of global environmental change. Sufficient mobility, high resistance to acute heat stress, and inherent adaptation to warmer climates appear to be key traits that allow pollinators to persist and even expand in the face of climate change. An overall flexibility in dietary and nesting requirements is common in expanding species, although niche specialization can also drive expansion under specific contexts. The numerous consequences of wild and domesticated pollinator expansions, including competition for resources, pathogen spread, and hybridization with native wildlife, are also discussed. Overall, we show that the traits and factors involved in the success stories of expanding pollinators are mostly species specific and context dependent, rendering generalizations of 'winning traits' complicated. This work illustrates the increasing need to consider expansion and its numerous consequences as significant facets of global changes and encourages efforts to monitor the impacts of expanding insect pollinators, particularly exotic species, on natural ecosystems.

Compositional flexibility in Li-N-H materials: implications for ammonia catalysis and hydrogen storage

Li–N–H materials, particularly lithium amide and lithium imide, have been explored for use in a variety of energy storage applications in recent years. Compositional variation within the parent lithium imide, anti-fluorite crystal structure has been related to both its facile storage of hydrogen and impressive catalytic performance for the decomposition of ammonia. Here, we explore the controlled solid-state synthesis of Li–N–H solid-solution anti-fluorite structures ranging from amide-dominated (Li_4/3(NH₂)_2/3(NH)_1/3 or Li_1.333NH_1.667) through lithium imide to majority incorporation of lithium nitride–hydride (Li_3.167(NH)_0.416N_0.584H_0.584 or Li_3.167NH). Formation of these solid solutions is demonstrated to cause significant changes to the thermal stability and ammonia reactivity of the samples, highlighting the potential use of compositional variation to control the properties of the material in gas storage and catalytic applications.

A wide solid solution based on the lithium imide anti-fluorite structure is demonstrated and related to its energy storage functions.

The Changing Characteristics of Arthroplasty Patients: A Retrospective Cohort Study

BACKGROUND

Total joint arthroplasty (TJA) is among the most common operations performed worldwide, with global volumes on the rise. It is important to understand if the characteristics of this patient population are changing over time for resource allocation and surgical planning. The purpose of this study is to examine how this patient population has changed between 2003 and 2017.

METHODS

A retrospective review of a prospective TJA database was conducted. Age, gender, body mass index, comorbidities, American Society of Anesthesiologists class, responsible diagnoses, and comorbidities were compared over 5-year intervals between 2003 and 2017. All patients undergoing primary, elective TJA were included.

RESULTS

Overall, 17,138 TJAs were included. Mean body mass index increased over the study period for total hip arthroplasty (THA; 29.4-30.4 kg/m², P < .0001) and total knee arthroplasty (TKA; 32.0-3.1 kg/m², P < .0001) patients. THA patients were significantly younger in more recent years (68.0-66.8 years old, P = .0026); this trend was not observed among TKA patients. Over the study period, a significantly higher proportion of patients were American Society of Anesthesiologists class III/IV for THA (50.5%-72.3%) and TKA (57.5%-80.7%) (P < .00001). Prevalence of common comorbidities did not change significantly.

CONCLUSION

The key findings of this retrospective analysis of a large prospective database are that patients undergoing TJA are becoming younger and more obese. It is unclear whether patients are becoming more medically complex. These trends paint a concerning picture of a population that is increasingly complex, and may require a greater allocation of resources in the future.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Global patterns in bumble bee pollen collection show phylogenetic conservation of diet

Bumble bees (Bombus) are a group of eusocial bees with a strongly generalised feeding pattern, collecting pollen from many different botanical families. Though predominantly generalists, some bumble bee species seem to have restricted dietary choices. It is unclear whether restricted diets in bumble bees are inherent or a function of local conditions due to a lack of data for many species across different regions. The objective of this study was to determine whether bumble bee species displayed specific patterns of pollen collection, and whether patterns were influenced by phylogenetic relatedness or tongue length, a trait known to be associated with structuring floral visitation. Bumble bee pollen collection patterns were quantified from 4,132 pollen loads taken from 58 bumble bee species, representing 24% of the pollen-collecting diversity of this genus. Phylogenetic trait mapping showed a conserved pattern of dietary dissimilarity across species, but not for dietary breadth. Dietary dissimilarity was driven by collection of Fabaceae, with the most similar species collecting around 50%-60% of their diet from this botanical family. The proportion of the diet collected from Fabaceae also showed a conserved phylogenetic signal. Greater collection of Fabaceae was associated with longer tongue lengths, with shorter tongued species focusing on alternative botanical families. However, this result was largely driven by phylogenetic relatedness, not tongue length per se. These results demonstrate that, though generalists, bumble bees are still subject to dietary restrictions that constrain their foraging choices. These dietary constraints have implications for their persistence should their core resources decline in abundance.

Postoperative Outcomes Following Total Hip and Knee Arthroplasty in Patients with Pain Catastrophizing, Anxiety, or Depression

BACKGROUND

The relationship among pain catastrophizing, emotional disorders, and total joint arthroplasty (TJA) outcomes is an emerging area of study. The purpose of this study is to examine the association of these factors with 1-year postoperative pain and functional outcomes.

METHODS

A prospective cohort study of preoperative TJA patients using the Pain Catastrophizing Scale and Hospital Anxiety and Depression Scale (HADS-A/HADS-D) was conducted. Postoperative outcomes included Visual Analog Scale (VAS) pain, Oxford, Harris Hip (HHS) and Knee Society (KSS) scores. Median regression was used to assess the pattern of relationship among preoperative clinically relevant catastrophizing (CRC) pain, abnormal HADS, and 1-year postoperative outcomes.

RESULTS

We recruited 463 TJA patients, all of which completed 1-year follow-up. At 1 year, CRC-rumination (adjusted median difference 1; 95% confidence interval [CI] 0.31-1.69, P = .005) and abnormal HADS-A (adjusted median difference 1; 95% CI 0.36-1.64, P = .002) were predictors of VAS pain, CRC magnification a predictor of HHS/KSS (adjusted median difference 1.3; 95% CI 5.23-0.11, P = .041), and abnormal HADS-A a predictor of Oxford (adjusted median difference 3.68; 95% CI 1.38-5.99, P = .002). CRC patients demonstrated inferior VAS pain (P = .001), Oxford (P < .0001), and HHS/KSS (P = .025). Abnormal HADS patients demonstrated inferior postoperative VAS (HADS-A, P = .025; HADS-D, P = .030) and Oxford (HADS-A, P = .001; HADS-D, P = .030). However, patients with CRC experienced significant improvement in VAS, Oxford, and HHS/KSS (P < .05) from preoperative to 1 year. Similarly, patients with abnormal HADS showed significant improvement in VAS pain and HHS/KSS (P < .05).

CONCLUSION

TJA patients who are anxious, depressed, or pain catastrophizing have inferior preoperative and postoperative pain and function. However, as compared to their preoperative status, clinically significant improvement can be expected following hip/knee arthroplasty.

Quantifying the Level of Evidence of Podium Presentations at the American Association of Hip and Knee Surgeons From 2015 to 2019

BACKGROUND

The American Association of Hip and Knee Surgeons (AAHKS) Annual Scientific Meeting is a leading forum for the presentation and dissemination of research regarding the management of hip and knee pathology making research presented at these meetings a representation of the current literature in the field. The purpose of this study was to quantify the level of evidence of podium presentations presented at the AAHKS annual meeting from 2015 to 2019.

METHODS

Two reviewers evaluated the abstracts for the available presentations. Basic science and biomechanical studies were excluded from the review. Economic studies that were not able to be evaluated based on the American Academy of Orthopedic Surgeon guidelines were also excluded. The two reviewers then independently evaluated each abstract and assigned a level of evidence (level I-V) based on the American Academy of Orthopedic Surgeon classification scheme.

RESULTS

A total of 258 podium presentations were included. In total, 17 (7%) abstracts were graded level I evidence, 57 (22%) were graded level II, 85 (33%) were graded level III, and 98 (38%) were graded level IV (Table 1). There was a significant change in the distribution of the level of evidence of podium presentations over time (χ² = 24.6, P = .02). The proportion of level I studies has increased between 2015 and 2019 (from 3.9% to 11.8%) with a concomitant decrease in level IV studies (from 42.3% to 21.6%) over that time period.

CONCLUSIONS

There has been a significant improvement in the levels of evidence of podium presentations at the AAHKS Annual Meeting from 2015 to 2019.

The bees of Lebanon (Hymenoptera: Apoidea: Anthophila)

The study of wild bees has markedly increased in recent years due to their importance as pollinators of crops and wild plants, and this interest has been accentuated by increasing evidence of global declines in their abundance and species richness. Though best studied in Europe and North America, knowledge on the current state of wild bees is scarce in regions where they are particularly diversified, such as the Mediterranean basin. The eastern Mediterranean country of Lebanon, located at the heart of the Levant in a biodiversity hotspot, is particularly poorly studied. The aim of this paper is to produce a first annotated checklist of the wild bees of Lebanon from new and museum collections, literature records, and verified occurrences from online databases. The present list totals 573 species for Lebanon of which 289 are reported for the first time, but the estimated diversity is likely to be closer to 700. Preliminary information on local distributions and flower records are also presented. The local species assemblages indicate affinities with montane habitats of the Mediterranean and Anatolia and the semi-arid habitats of the Levant and north Africa. This study also encourages further research on local wild bee faunas and the use of this knowledge for conservation purposes.

Randomized Controlled Trial of Sensor-Guided Knee Balancing Compared to Standard Balancing Technique in Total Knee Arthroplasty

BACKGROUND

Despite advances in total knee arthroplasty (TKA) technology, up to 1 in 5 patients remain dissatisfied. This study sought to evaluate if sensor-guided knee balancing improves postoperative clinical outcomes and patient satisfaction compared to a conventional gap balancing technique.

METHODS

We undertook a prospective double-blind randomized controlled trial of patients presenting for elective primary TKA to determine a difference in TKA soft tissue balance between a standard gap balancing (tensiometer) approach compared to augmenting the balance using a sensor-guided device. The sensor-guided experimental group had adjustments made to achieve a balanced knee to within 15 pounds of intercompartmental pressure difference. Secondary outcomes included differences in clinical outcome scores at 6 months and 1 year postoperative, including the Oxford Knee Score and Knee Society Score and patient satisfaction.

RESULTS

The sample comprised of 152 patients, 76 controls and 76 experimental sensor-guided cases. Within the control group, 36% (27/76) of knees were unbalanced based on an average coronal plane intercompartmental difference >15 pounds, compared to only 5.3% (4/76) within the experimental group (P < .0001). There were no significant differences in 1-year postoperative flexion, Knee Society Score, or Oxford scores. Overall, TKA patient satisfaction at 1 year was comparable, with 81% of controls and experimental cases reporting they were very satisfied (P = .992).

CONCLUSION

Despite the use of the sensor-guided knee balancer device to provide additional quantitative feedback in the evaluation of the soft tissue envelope during TKA, we were unable to demonstrate improved clinical outcomes or patient satisfaction compared to our conventional gap balancing technique.

The wild bees (Hymenoptera: Apoidea) of Morocco

Morocco is a well known hot-spot of biodiversity in the Mediterranean basin. While some taxa like vascular plants are relatively well recorded, important groups of pollinators like bees are still understudied. This article presents an updated checklist of the bee species of Morocco and includes a summary of global and regional distribution of each species. A total of 961 species belonging to six bee families and 68 genera are recorded: Andrenidae (8 genera, 217 species); Apidae (15 genera, 241 species); Colletidae (2 genera, 74 species), Halictidae (12 genera, 144 species), Megachilidae (28 genera, 271 species) and Melittidae (3 genera, 14 species). Among them, 67 species are recorded for the first time in Morocco. Around 70% of the bee fauna of Morocco consists of widespread Palaearctic species. Only 18% of Moroccan species recorded are restricted to North Africa and 8% are Moroccan single-country endemics (81 species). Afrotropical elements in the Moroccan fauna are few, with only 3% of Morocco species co-occuring in that region. This checklist is intended to stimulate new regional research on bees including their taxonomy and biogeography. As many groups of bees have been understudied, discovery of new species for science and new records for the country can be expected. Additional research including inventorying, monitoring, and integrative taxonomic studies are needed to develop a comprehensive strategy for bee conservation in Morocco.

Local antibiotics in primary hip and knee arthroplasty: a systematic review and meta-analysis

BACKGROUND

Infection is a truly devastating complication of total joint arthroplasty, causing most patients to undergo a revision surgery, and to bear significant psychological and financial burden. The purpose of this study is to systematically evaluate the literature to determine the efficacy and complication profile of local antibiotic application in primary total joint arthroplasty.

METHODS

All studies of primary total joint arthroplasty which assessed local antibiotics in any form other than antibiotic-impregnated cement as an intervention were included. Studies that reported at least one outcome related to infection and were available in full text in English were eligible for inclusion. Studies which included both primary and revision cases but did not report the stratified data for each type of surgery and studies on fracture populations were excluded.

RESULTS

A total of 9 studies involving 3,714 cases were included. The pooled deep infection rate was 1.6% in the intervention groups and 3.5% in the control groups. Meta-analysis revealed a RR of 0.53 (95%CI: 0.35-0.79, p = 0.002) with no heterogeneity (I² = 0%) for infection in the intervention groups. Meta-analysis revealed a non-significant reduction in superficial infection rates in the intervention groups; however, there was a significant increase in aseptic wound complications in the intervention groups.

CONCLUSION

Local antibiotic application results in a moderate reduction in deep infection rates in primary total joint arthroplasty, with no significant impact on superficial infection rates. However, local antibiotic application may be associated with a moderate increase in aseptic wound complications.

Three Femoral Stem Designs Without Corrosion: A Review of 2095 Stems

Introduction

Corrosion at the head-neck interface of modular components in total hip arthroplasty (THA) has been reported as a cause of failure of modern total hip replacement implants. While this method of failure has been well described, it remains poorly understood. The purpose of this study is to review the three most commonly used uncemented femoral stems at our institution over the last fifteen years and to correlate any established risk factors with rates of revision, particularly corrosion.

Methods

We reviewed 2095 patients from March 2000 to September 2015 who underwent total hip arthroplasty with one of three uncemented femoral stem designs. All stems were made of a Ti6Al4V alloy with a 12/14 taper design. We included only those stems coupled with a CoCr head and a highly crosslinked polyethylene liner. We evaluated age, gender, body mass index (BMI), femoral head size, head length, neck angle and offset and correlated these to the incidence of all cause revision, as well as revision excluding infection.

Results

There were no recognized corrosion-related revisions identified. There was no association between age, BMI, gender, head length, neck angle and offset to all cause revision or revision with infection excluded (p>0.05). Femoral head size less than 32mm was associated with higher all cause revision rates (OR 4.60 (95% CI 1.8, 11.8)) and when excluding infection as a reason for revision (OR 4.94 (95% CI 1.7, 14.41)).

Conclusion

Over the last fifteen years, we have not identified any cases of corrosion with the three most commonly used femoral stems used at out institution. While we acknowledge that no femoral stem is immune to corrosion, certain femoral stem designs may be uniquely resistant to this mode of failure.

Level of Evidence

III.

Effect of the Extent of Release for Knee Balancing on Post-Operative Limb Coronal Alignment After Primary Total Knee Arthroplasty

Introduction

Outcomes and longevity of total knee arthroplasty (TKA) depend mainly on restoring knee function, through precise bony resection and appropriate soft tissue balancing. The current literature lacks evidence regarding the degree of radiographic change after intra-operative knee balancing. The purpose of our study was to assess the degree of change in coronal lower extremity alignment by comparing pre-operative to post-operative full-length radiographs (FLR) after quantifying the degree of intra-operative knee balancing and correlate patient-reported outcomes to the extent of balancing required.

Patients and Methods

One hundred and fifty-four patients undergoing primary TKA for varus knee osteoarthritis were included in the study. The performed soft tissue releases and bony adjustments to obtain a balanced TKA intra-operatively were prospectively documented and were grouped into minimal, moderate and extensive release groups. Hip-knee-ankle angle (HKA), anatomical femoral-tibial angle (FTA), condylar hip angle (CH), medial proximal tibial angle (MPTA) and condylar plateau angle (CPA) were measured on full-length radiographs both pre-operatively and post-operatively. Frequencies of the soft tissue releases and bony resections in addition to descriptive statistics of the measured angles on the radiographs were recorded. In addition, patient-reported outcome scores (PROMs) were compared between the grouped patients.

Results

Of those that were included in the study, 66 knees (42.9%) required minimal release to adequately balance the knee, while 70 (45.5%) required moderate release and 18 (11.7%) required extensive release. No statistically significant differences were found in change of alignment between the groups for all the measured angles. In addition, no difference in PROMs was seen between the groups both pre- and post-operatively.

Conclusion

Although we found no association between post-operative coronal alignment of a TKA and the degree of soft tissue release and bony resection, this likely represents the fact that a balanced TKA is dynamic and not dependent on change of single radiographic parameters. Patient-reported outcomes were not impacted by the extent of releases.

Accelerated surgery versus standard care in hip fracture (HIP ATTACK): an international, randomised, controlled trial

BACKGROUND

Observational studies have suggested that accelerated surgery is associated with improved outcomes in patients with a hip fracture. The HIP ATTACK trial assessed whether accelerated surgery could reduce mortality and major complications.

METHODS

HIP ATTACK was an international, randomised, controlled trial done at 69 hospitals in 17 countries. Patients with a hip fracture that required surgery and were aged 45 years or older were eligible. Research personnel randomly assigned patients (1:1) through a central computerised randomisation system using randomly varying block sizes to either accelerated surgery (goal of surgery within 6 h of diagnosis) or standard care. The coprimary outcomes were mortality and a composite of major complications (ie, mortality and non-fatal myocardial infarction, stroke, venous thromboembolism, sepsis, pneumonia, life-threatening bleeding, and major bleeding) at 90 days after randomisation. Patients, health-care providers, and study staff were aware of treatment assignment, but outcome adjudicators were masked to treatment allocation. Patients were analysed according to the intention-to-treat principle. This study is registered at ClinicalTrials.gov (NCT02027896).

FINDINGS

Between March 14, 2014, and May 24, 2019, 27 701 patients were screened, of whom 7780 were eligible. 2970 of these were enrolled and randomly assigned to receive accelerated surgery (n=1487) or standard care (n=1483). The median time from hip fracture diagnosis to surgery was 6 h (IQR 4-9) in the accelerated-surgery group and 24 h (10-42) in the standard-care group (p<0·0001). 140 (9%) patients assigned to accelerated surgery and 154 (10%) assigned to standard care died, with a hazard ratio (HR) of 0·91 (95% CI 0·72 to 1·14) and absolute risk reduction (ARR) of 1% (-1 to 3; p=0·40). Major complications occurred in 321 (22%) patients assigned to accelerated surgery and 331 (22%) assigned to standard care, with an HR of 0·97 (0·83 to 1·13) and an ARR of 1% (-2 to 4; p=0·71).

INTERPRETATION

Among patients with a hip fracture, accelerated surgery did not significantly lower the risk of mortality or a composite of major complications compared with standard care.

FUNDING

Canadian Institutes of Health Research.

Use of the Corail stem for revision total hip arthroplasty: evaluation of clinical outcomes and cost

Background

With the growing number of total hip arthroplasty (THA) procedures performed, revision surgery is also proportionately increasing, resulting in greater health care expenditures. The purpose of this study was to assess clinical outcomes and cost when using a collared, fully hydroxyapatite-coated primary femoral stem for revision THA compared to commonly used revision femoral stems.

Methods

We retrospectively identified patients who underwent revision THA with a primary stem between 2011 and 2016 and matched them on demographic variables and reason for revision to a similar cohort who underwent revision THA. We extracted operative data and information on in-hospital resource use from the patients’ charts to calculate average cost per procedure. Patient-reported outcomes were recorded preoperatively and 1 year postoperatively.

Results

We included 20 patients in our analysis, of whom 10 received a primary stem and 10, a typical revision stem. There were no significant between-group differences in mean Western Ontario and McMaster Universities Osteoarthritis Index score, Harris Hip Score, 12-Item Short Form Health Survey (SF-12) Mental Composite Scale score or Physical Composite Scale score at 1 year. Operative time was significantly shorter and total cost was significantly lower (mean difference –3707.64, 95% confidence interval –5532.85 to –1882.43) with a primary stem than with other revision femoral stems.

Conclusion

We found similar clinical outcomes and significant institutional cost savings with a primary femoral stem in revision THA. This suggests a role for a primary femoral stem such as a collared, fully hydroxyapatite-coated stem for revision THA.

Mismatched outcomes for biodiversity and ecosystem services: testing the responses of crop pollinators and wild bee biodiversity to habitat enhancement

Supporting ecosystem services and conserving biodiversity may be compatible goals, but there is concern that service-focused interventions mostly benefit a few common species. We use a spatially replicated, multiyear experiment in four agricultural settings to test if enhancing habitat adjacent to crops increases wild bee diversity and abundance on and off crops. We found that enhanced field edges harbored more taxonomically and functionally abundant, diverse, and compositionally different bee communities compared to control edges. Enhancements did not increase the abundance or diversity of bees visiting crops, indicating that the supply of pollination services was unchanged following enhancement. We find that actions to promote crop pollination improve multiple dimensions of biodiversity, underscoring their conservation value, but these benefits may not be spilling over to crops. More work is needed to identify the conditions that promote effective co-management of biodiversity and ecosystem services.

Comparison of trans-cortical and cancellous screws to press fit for acetabular shell fixation in total hip arthroplasty: A cadaveric study

BACKGROUND

Total hip arthroplasty complications are associated with mechanical loosening of the acetabular component, which may be attributed to the type of fixation used (press fit, trans-cortical screws, cancellous screws). Therefore, the purpose of this study was to compare trans-cortical and cancellous screws to press fit for fixation of the acetabular shell.

METHODS

Five cadaveric pelvis specimens were hemisected (N = 10) at the sacroiliac joint. Each hemi-pelvis was initially tested with a press fit cup followed by the left and right pairs being randomized to either a cancellous or trans-cortical screw condition. Each fixation was tested by applying a load to a rod inserted into the centre of the acetabular cup at 0.5 mm/s, until failure occurred. The failure force, failure moment, and the rotation angle of the cup at failure were calculated.

FINDINGS

The cups fixated with a trans-cortical screw failed at a significantly greater mean [SD] force (1046.20 [386.52] N). The trans-cortical screws also significantly increased the angle of failure 46.29 (16.90) ° compared to the press-fit cups (6.73 [4.59] °). Finally, there was a significant increase in the failure moment, such that, the trans-cortical condition failed at a mean (SD) moment of 53.75 (16.24) Nm compared to 9.59 (1.85) Nm and 32.15 (18.16) Nm for the press fit and cancellous (p = 0.044) conditions, respectively.

INTERPRETATION

The acetabular shells that were fixated with trans-cortical screws provide greater stability compared to the press-fit cups or cancellous screws.

Gone girl: Richardson's ground squirrel offspring and neighbours are resilient to female removal

Within matrilineal societies, the presence of mothers and female kin can greatly enhance survival and reproductive success owing to kin-biased alarm calling, cooperation in territory defence, protection from infanticidal conspecifics, joint care of young and enhanced access to resources. The removal of mothers by predators or disease is expected to increase the stress experienced by offspring via activation of their hypothalamic-pituitary-adrenal axis, increasing circulating glucocorticoids and reducing offspring survival and reproductive success. Yet, few studies have removed mothers in the post-weaning period to examine the assumed physiological and fitness consequences associated with these mortality events. We examined how the loss of a mother affects juvenile Richardson's ground squirrels' (Urocitellus richardsonii) faecal glucocorticoid metabolites and their survival. Given that neighbours are often close kin, we further hypothesized that conspecific removal would similarly diminish the fitness of neighbouring individuals. Upon removing the mother, we detected no impact on offspring or neighbouring conspecific faecal glucocorticoid metabolites in the removal year, or on overwinter survival in the following year. Furthermore, no impact on neighbour reproductive success was detected. Given the high predation rates of ground squirrels in wild populations, resilience to a changing social environment would prove adaptive for both surviving kin and non-kin.

Preoperative Patient Factors Affecting Length of Stay following Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

BACKGROUND

Total knee arthroplasty (TKA) yields substantial improvements in quality of life for patients with severe osteoarthritis. Previous research has shown that TKA outcomes are inferior in patients with certain demographic and clinical factors. Length of stay (LOS) following TKA is a major component of costs incurred by healthcare providers. It is hypothesized that patient-related factors may influence LOS following TKA. The purpose of this systematic review and meta-analysis is to investigate these factors.

METHODS

Three databases (PubMed, Embase, and OVID Medline) were searched using variants of the terms "total knee arthroplasty" and "length of stay". Studies were screened and data abstracted in duplicate. The primary outcome was the effect of prognostic variables on LOS following TKA. Meta-analysis was performed using the Review Manager (RevMan) software (version 5.3. Copenhagen: The Nordic Cochrane Center, The Cochrane Collaboration, 2014).

RESULTS

A total of 68 studies met all inclusion criteria for this review. These studies comprised 21,494,459 patients undergoing TKA with mean age 66.82 years (range, 15-95 years) and 63.8% (12,165,160 of 19,060,572 reported) females. The mean MINORS score was 7, suggesting that studies had a low quality of evidence. Mean LOS following TKA has steadily decreased over the past 4 decades, partially because of the implementation of fast-track programs. Demographic factors associated with increased LOS were age >70 years (mean difference [MD] = 0.81; 95% confidence interval [CI] = 0.38-1.24), female gender (MD = 0.32; 95% CI = 0.29-0.48), body mass index >30 (MD = 0.09; 95% CI = 0.01-0.16), and non-White race (MD = 0.20; 95% CI = 0.10-0.29). Clinical factors associated with increased LOS were American Society of Anesthesiologists score 3-4 vs 1-2 (MD = 1.12; 95% CI = 0.58 to 1.66), Charlson Comorbidity Index > 0 vs 0 (MD = 0.77; 95% CI = 0.32 to 1.22), and preoperative hemoglobin < 130 g/L (MD = 0.66; 95% CI = 0.34 to 0.98).

CONCLUSION

This systematic review and meta-analysis showed that increased age, female gender, body mass index ≥ 30, non-White race, American Society of Anesthesiologists > 2, Charlson Comorbidity Index > 0, and preoperative hemoglobin < 130 g/L were predictors of increased LOS. Mean LOS has steadily decreased over the past decades with the implementation of perioperative "fast-track" programs. Future research should investigate the benefits of preoperative risk factor modification on LOS, in addition to novel surgical approaches, anesthetic adjuvants, and physiotherapy modifications.

LEVEL OF EVIDENCE

IV, systematic review, and meta-analysis of level III and IV evidence.

Catastrophic femoral head trunnion dissociation: a case series with surface wear analysis

INTRODUCTION

Modular designs enhance accuracy of limb length and offset during total hip arthroplasty. However, such interfaces can be the site of corrosion and implant failure. The purpose of this study was to review 5 cases of catastrophic femoral head trunnion dissociation to better understand clinical and implant related risk factors for this complication.

METHODS

We describe 5 cases of femoral head dissociation following significant trunnion wear. Patient and implant related factors are reviewed. Surface wear patterns were assessed using electron microscopy and wear patterns were described qualitatively.

RESULTS

Commonalties among 5 presented cases include male, age over 65 and increased BMI. All femoral heads were cobalt chromium with a head size of at least 36 mm or greater. 4 out of 5 had high offset. All stems were the same design. Surface wear analysis showed material removed initially on the inferomedial aspect of the trunnion where the femoral head contacted the stem.

CONCLUSIONS

Femoral head dissociation secondary to failure of the trunnion is a rare complication. We show associations with older age, increased BMI and male patients with increased femoral head size and offset. Material is removed initially inferomedially and progresses to fracturing the superior aspect of the trunnion.

The effect of altering head length on corrosion using a material loss method

INTRODUCTION

Corrosion at head neck taper junctions in total hip arthroplasty has increasingly been reported in the literature. Debate persists as to the exact causes and clinical significance of corrosion. Increased offset and head length has been correlated with an increased risk of tribocorrosion due to an adverse mechanical environment. The purpose of this study is to assess the effect of head length on corrosion of a metal-on-polyethylene articulation.

METHODS

Retrievals from a single institution of 28-mm cobalt chromium alloy heads with a 12/14 taper from a single manufacturer were studied. Corrosion of femoral head bores were studied utilising a material loss method. Testing was performed using co-ordinate measuring for maximum linear wear depth.

RESULTS

56 heads were examined with lengths of either -3, 0, +4 or +8 mm and all had been in situ for a minimum of 2 years. There were no significant differences in mean maximum linear wear depth (MLWD) (p = 0.6545). There was no correlation found between MLWD and the time implants were in situ (Spearman coefficient -0.1157) and no significant difference seen between high or standard offset stems (p = 0.1336).

CONCLUSION

In contrast to studies using qualitative methodologies, there was no correlation between head length and material loss when confined to a 28-mm head. Broad application of this outcome should be cautioned against as this study examined 1 taper construct and a metal-on-polyethylene articulation.

Honeybee dietary neonicotinoid exposure is associated with pollen collection from agricultural weeds

Neonicotinoid insecticides have been linked to bee declines. However, tracking the primary exposure route for bees in the field has proven to be a major logistical challenge, impeding efforts to restore pollinator health in agricultural landscapes. We quantified neonicotinoid concentrations and botanical species composition in 357 pollen samples collected from 114 commercial honeybee colonies placed along a gradient of agricultural intensity between June and September. Neonicotinoid concentrations increased through the season, peaking at the end of August. As a result, concentrations in pollen were negatively associated with collection from woody and crop plants that flower early-mid season, and positively associated with collection from herbaceous plants that flower mid-late season. Higher clothianidin and thiamethoxam residues were correlated with samples containing a greater proportion of pollen collected from agricultural weeds. The percentage of agricultural land within 1500 m was positively correlated with thiamethoxam concentration; however, this spatial relationship was far weaker than the relationship with the proportion of pollen collected from herbaceous plants. These results indicate that both plant species identity and agricultural dominance are important in determining honeybee neonicotinoid exposure through the pollen diet, but that uncultivated plants associated with agriculture are the source of the greatest acute exposure.

New data on the Iberian endemic bee genus Flavipanurgus Warncke Hymenoptera: Apoidea: Andrenidae): Ecological and genomic data reveal a hidden species

Flavipanurgus is a small genus of panurgine bees known only from the Iberian Peninsula. Despite its status as one of the few bee genera endemic to Europe, Flavipanurgus are poorly represented in collections and until recently, their ecology had been almost unknown. Flavipanurgus ibericus (Warncke, 1972) was described from southern Iberia, with a northern subspecies F. i. kastiliensis (Warncke, 1987) later described from the north. Recent collections in Portugal have revealed clear differences in the pollen collecting patterns of the two taxa, with southern females collecting exclusively from Jasione montana and northern females from Sedum species. In combination with this ecological difference, COI and 28S barcode data indicate that Flavipanurgus kastiliensis stat. nov. should be raised to full species status. The male of Flavipanurgus ibericus s. str. is described for the first time, and updated keys to Flavipanurgus species are provided. Flavipanurgus fuzetus Patiny, 1999 is recorded for the first time from Spain. Further significant records and new floral associations for Flavipanurgus are also presented.

Limited phenological and dietary overlap between bee communities in spring flowering crops and herbaceous enhancements

Wild bee populations have undergone declines in recent years across much of the Western world, and these declines have the potential to limit yield in pollination-dependent crops. Highbush blueberry, Vaccinium corymbosum, and tart cherry, Prunus cerasus, are spring-blooming crops that rely on the movement of pollen by bees and other insects for pollination. Wild bee populations can be increased on farmland by providing floral resources, but whether the addition of these plants translates into increased pollinator density on crop flowers has not been documented in most cropping systems. To determine the importance of providing additional floral resources for wild bee pollinator communities, we selected blueberry fields and tart cherry orchards with and without herbaceous floral enhancements in western Michigan, USA. The bee communities visiting crop flowers, enhancements and control grassy field margins were sampled over a 5-yr period. In addition, the pollen diets of the most abundant wild bee crop pollinators were quantified across Michigan to better understand their foraging niches and to identify potentially important alternative host plants. The presence of floral enhancements did not increase the abundance of wild bees on either blueberry or cherry flowers during bloom. The bee community visiting blueberry was evenly composed of short-season bees that fly only during the spring and long-season bees that fly in both spring and summer. In contrast, the bee community visiting cherry was dominated by short-season spring bees. The majority of pollen collected by the wild bee communities visiting blueberry and cherry was from spring-flowering woody plants, with limited use of the herbaceous enhancements. Enhancements attracted greater abundance and species richness of bees compared to control areas, including twice as many floral specialists. Conserving summer-flying, grassland-associated bees is an appropriate goal for pollinator conservation programs. However, herbaceous enhancements may not provide adequate resources for the wild bees that pollinate spring-flowering crops. This study demonstrates that an examination of the pollen collected by wild bees across their flight periods can identify plant species to help them persist in intensively managed landscapes.

An X-ray and Neutron Reflectometry Study of Iron Corrosion in Seawater

The corrosive breakdown of thin iron films supported on silicon substrates under a number of conditions is presented-in particular to understand better how iron, and hence ferritic steel, behaves in a salty water environment. A combination of X-ray and neutron reflectometry was used to monitor the structures of both metal and oxide surface layers and also organic corrosion inhibitors adsorbed at the iron/aqueous interface. A range of behavior in seawater was observed, including complete dissolution and void formation under the metal surface. Importantly, two simple treatments-UV/ozone or soaking in ultrapure water-were found to significantly protect the iron surface for considerable lengths of time, although evidence of pitting corrosion began after around 10 days. The underlying causes of the efficacies of these treatments were further investigated using X-ray photoelectron spectroscopy. In addition, three potential corrosion inhibitors were investigated: (i) dodecyltrimethylammonium bromide (DTAB) demonstrated no ability to protect the surface; (ii) sodium dodecyl sulfate (SDS) appeared to accelerate corrosion; and (iii) bis(2-ethylhexyl)phosphate showed an impressive level of protection (the neutron reflectometry results indicated a thick diffuse layer of surfactant of 23% surface coverage). These findings have been interpreted in terms of preferential inhibitor adsorption at cathodic and anodic surface sites (depending on the nature of the inhibitor).

Neutron diffraction and gravimetric study of the iron nitriding reaction under ammonia decomposition conditions

Ammonia decomposition over iron catalysts is known to be affected by whether the iron exists in elemental form or as a nitride. In situ neutron diffraction studies with simultaneous gravimetric analysis were performed on the nitriding and denitriding reactions of iron under ammonia decomposition conditions. The gravimetric analysis agrees well with the Rietveld analysis of the neutron diffraction data, both of which confirm that the form of the iron catalyst is strongly dependent on ammonia decomposition conditions. Use of ammonia with natural isotopic abundance as the nitriding agent means that the incoherent neutron scattering of any hydrogen within the gases present is able to be correlated to how much ammonia had decomposed. This novel analysis reveals that the nitriding of the iron occurred at exactly the same temperature as ammonia decomposition started. The iron nitriding and denitriding reactions are shown to be related to steps that take place during ammonia decomposition and the optimum conditions for ammonia decomposition over iron catalysts are discussed.

Neutron diffraction and gravimetric study of the manganese nitriding reaction under ammonia decomposition conditions

In situ neutron diffraction of ammonia decomposition over manganese reveals the structures of different nitrides and kinetic information about their formation.

Bulk phase behavior of lithium imide–metal nitride ammonia decomposition catalysts

Lithium imide is a promising new catalyst for the production of hydrogen from ammonia. This study reports the use of neutron and X-ray powder diffraction to investigate the presence of ternary nitrides in lithium-imide/metal nitride composite catalysts.

<i>Camptopoeum</i> (<i>Camptopoeum</i>) <i>baldocki</i> spec. nov., a new panurgine bee species from Portugal and a description of the male of <i>Flavipanurgus</i> <i>fuzetus</i> Patiny (Andrenidae: Panurginae)

Camptopoeum (Camptopoeum) baldocki spec. nov., a new European panurgine bee species is described and diagnosed. It is currently known only from saltmarshes along the southern coast of the central and eastern Algarve, Portugal. Observations and analysis of scopal pollen loads suggest narrow oligolecty on the similarly halophilous Frankenia laevis (Frankeniaceae). In addition, the allotype male of the Portuguese endemic Flavipanurgus fuzetus Patiny is described and the pollen preferences of Flavipanurgus are reviewed with the addition of new data from Portugal. As a genus, Flavipanurgus species appear to be narrowly oligolectic on a range of flowers from the botanical families Caryophyllaceae, Cistaceae and Crassulaceae.