The impact of socioeconomic status on implant selection for patients undergoing hip arthroplasty

© 2015, UTMJ. All rights reserved. Hip resurfacing arthroplasty (HRA) is an alternative to total hip arthroplasty (THA) that preserves proximal femoral bone stock. Patient socioeconomic status (SES) has been demonstrated to impact access to care for numerous healthcare interventions but little is known about its impact on HRA when compared to THA. The aim of this study was to investigate whether there are disparities in SES for patients receiving HRA or THA. A retrospective database review was conducted comprising 617 hip arthroplasty patients (310 HRA, 307 THA). Patient postal code was used as a surrogate marker for patients’ SES and referenced against Canada Census Tract data to determine patient income. Patients greater than 70 years of age and those who underwent THA as revision or for fractures were excluded from the study. There were 465 patients included in the analysis comprised of 273 HRA and 192 THA patients. HRA patients ($33,240, SD$8,206) had a significantly higher mean income than THA patients ($29,365, SD$7,119, p\u3c0.001). The percentage of patients that underwent HRA compared to THA increased as patients’ SES increased. Patients with an income greater than $25,000 were significantly more likely to undergo HRA rather than THA (OR ≥1.76), compared to patients with an income less than$25,000 in whom THA was more likely. There appears to be a disparity in SES between patients who receive HRA and THA. Further work is needed to better understand the factors that influence the choice of hip replacement for patients requiring surgical intervention

Valgus stress radiography following superficial medial collateral ligament reconstruction using a modified LaPrade technique with adjustable loop femoral fixation

Purpose of this study was to assess postoperative laxity of MCL reconstructions utilizing a modified LaPrade superficial MCL reconstruction. We retrospectively reviewed post-operative valgus stress radiographs in 23 multiligament injured patients who underwent concurrent sMCL and cruciate ligament reconstruction by a single surgeon. Post- operatively, 23 patients underwent valgus stress radiographs that were assessed at a mean of 8.7 months (range: 4-13 months), and mean SSD was 0.64mm ± 0.42mm. Eight patients underwent both pre- and post-operative valgus stress radiographs. Post-operative (0.09mm ± 0.63mm) SSD was found to be significantly reduced compared to pre-operative (2.07mm ± 0.44mm) SSD (mean diff. = 1.98mm, 95% CI = 0.72-3.24, P=0.007). Inter-observer reliability value for medial compartment gap measurement was 0.91 with a 95% confidence interval of 0.34- 0.97. In conclusion, presented technique results in excellent static stability of the knee as measured by valgus stress radiography at a minimum of 6 months postoperative. Level of Evidence: IV

Co-limitation towards lower latitudes shapes global forest diversity gradients

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers

Pantropical variability in tree crown allometry

Aim Tree crowns determine light interception, carbon and water exchange. Thus, understanding the factors causing tree crown allometry to vary at the tree and stand level matters greatly for the development of future vegetation modelling and for the calibration of remote sensing products. Nevertheless, we know little about large‐scale variation and determinants in tropical tree crown allometry. In this study, we explored the continental variation in scaling exponents of site‐specific crown allometry and assessed their relationships with environmental and stand‐level variables in the tropics. Location Global tropics. Time period Early 21st century. Major taxa studied Woody plants. Methods Using a dataset of 87,737 trees distributed among 245 forest and savanna sites across the tropics, we fitted site‐specific allometric relationships between crown dimensions (crown depth, diameter and volume) and stem diameter using power‐law models. Stand‐level and environmental drivers of crown allometric relationships were assessed at pantropical and continental scales. Results The scaling exponents of allometric relationships between stem diameter and crown dimensions were higher in savannas than in forests. We identified that continental crown models were better than pantropical crown models and that continental differences in crown allometric relationships were driven by both stand‐level (wood density) and environmental (precipitation, cation exchange capacity and soil texture) variables for both tropical biomes. For a given diameter, forest trees from Asia and savanna trees from Australia had smaller crown dimensions than trees in Africa and America, with crown volumes for some Asian forest trees being smaller than those of trees in African forests. Main conclusions Our results provide new insight into geographical variability, with large continental differences in tropical tree crown allometry that were driven by stand‐level and environmental variables. They have implications for the assessment of ecosystem function and for the monitoring of woody biomass by remote sensing techniques in the global tropics

The Eelectrophysiological Effects of Iron Overload on the Heart

Chronic iron overload (CIO) in patients leads to a cardiomyopathy characterized by conduction defects, including bradyarrhythmias. Using a murine model of CIO, we explored the effects of iron loading on the electrophyisology of the heart. Telemetric heart rate was reduced in conscious CIO mice compared to controls. Similarly, heart rates were depressed in both isolated CIO hearts and CIO mice following autonomic blockade, suggesting an intrinsic impairment of the SA node (SAN). Indeed, spontaneous action potential frequency was reduced in CIO SAN myocytes. The depressed pacing rate in CIO SAN myocytes was linked to reduced L-type Ca2+ current (ICa,L) density and a rightward shift in ICa,L activation, suggesting a selective reduction in α1D-mediated ICa,L. Western blot analysis demonstrates that the α1D isoform was reduced by ~ 89% in CIO atrial tissue. Therefore, the conduction defects under conditions of CIO are due to reductions in Cav1.3 channel expression in atrial tissue.MAS

Valgus Stress Radiography Following Superficial Medial Collateral Ligament Reconstruction Using A Modified LaPrade Technique With Adjustable Loop Femoral Fixation

Purpose of this study was to assess postoperative laxity of MCL reconstructions utilizing a modified LaPrade superficial MCL reconstruction. We retrospectively reviewed post-operative valgus stress radiographs in 23 multiligament injured patients who underwent concurrent sMCL and cruciate ligament reconstruction by a single surgeon. Post-operatively, 23 patients underwent valgus stress radiographs that were assessed at a mean of 8.7 months (range: 4-13 months), and mean SSD was 0.64mm ± 0.42mm. Eight patients underwent both pre- and post-operative valgus stress radiographs. Post-operative (0.09mm ± 0.63mm) SSD was found to be significantly reduced compared to pre-operative (2.07mm ± 0.44mm) SSD (mean diff. = 1.98mm, 95% CI = 0.72-3.24, P=0.007).  Inter-observer reliability value for medial compartment gap measurement was 0.91 with a 95% confidence interval of 0.34-0.97. In conclusion, presented technique results in excellent static stability of the knee as measured by valgus stress radiography at a minimum of 6 months postoperative

Does Time to Surgery Affect Outcomes for Periprosthetic Femur Fractures?

© 2017 Background: Periprosthetic femur fractures around total hip (THA) and total knee (TKA) arthroplasties are difficult complications to manage. With native hip fractures, delay to fixation has been correlated with an increase in postoperative mortality. The effect of time to definitive fixation of periprosthetic femur fractures around THA and TKA is not well established. The aim of our study is to evaluate the effect of time to definitive fixation on postoperative length of stay and mortality for patients with periprosthetic femur fractures around THA and TKA. Methods: A review of 2537 arthroplasty patient charts yielded 235 patients who were diagnosed with a periprosthetic femur fracture at our institution from 2005 to 2014. Time to surgical management, length of stay, demographics, referral status, fracture classification, and fixation modality along with mortality was recorded for all patients. Results: One hundred eighty patients met study inclusion (111 THAs, 69 TKAs). Average age was 79.2 years and 72.2% were female. The average time from admission to definitive fixation was 96.5 hours with 31.1% of patients having surgery within 48 hours after presenting to hospital. Postoperative length of stay and mortality were not affected by time to definitive fixation greater than 48 hours for either of the periprosthetic TKA or THA patient cohorts. Postoperative mortality within 1 year was 5.5% for all patients (6.3% THA, 4.3% TKA). Conclusion: The timing of fixation of periprosthetic femur fractures does not appear to affect postoperative length of stay or mortality within 1 year

Microsecond-sustained lasing from colloidal quantum dot solids

<p>Colloidal quantum dots have grown in interest as materials for light amplification and lasing in view of their bright photoluminescence, convenient solution processing and size-controlled spectral tunability. To date, lasing in colloidal quantum dot solids has been limited to the nanosecond temporal regime, curtailing their application in systems that require more sustained emission. Here we find that the chief cause of nanosecond-only operation has been thermal runaway: the combination of rapid heat injection from the pump source, poor heat removal and a highly temperature-dependent threshold. We show microsecond-sustained lasing, achieved by placing ultra-compact colloidal quantum dot films on a thermally conductive substrate, the combination of which minimizes heat accumulation. Specifically, we employ inorganic-halide-capped quantum dots that exhibit high modal gain (1,200 cm 1 ) and an ultralow amplified spontaneous emission threshold (average peak power of B50 kWcm 2) and rely on an optical structure that dissipates heat while offering minimal modal loss.</p