Comparison of clinical outcomes between total hip replacement and total knee replacement

Background: Total hip replacements (THR) and total knee replacements (TKR) are effective treatments for severe osteoarthritis (OA). Some studies suggest clinical outcomes following THR are superior to TKR, the reason for which remains unknown. This study compares clinical outcomes between THR and TKR.Aim: To compare the clinic outcomes of THR and TKR using a comprehensive range of patient reported outcome measures (PROMs).Methods: A prospective longitudinal observational study of patients with OA undergoing THR and TKR were evaluated using a comprehensive range of generic and joint specific PROMs pre- and post-operatively.Results: A total of 131 patients were included in the study which comprised the THR group (68 patients) and the TKR group (63 patients). Both groups demonstrated significant post-operative improvements in all PROM scores (P < 0.001). There were no significant differences in post-operative PROM scores between the two groups: Hip and Knee Osteoarthritis Outcome scores (P = 0.140), Western Ontario and McMaster Universities Osteoarthritis Index pain (P = 0.297) stiffness (P = 0.309) and function (P = 0.945), Oxford Hip and Knee Score (P = 0.076), EuroQol-5D index (P = 0.386) and Short-Form 12-item survey physical component score (P = 0.106). Subgroup analyses showed no significant difference (P > 0.05) between cruciate retaining and posterior stabilised prostheses in the TKR group and no significant difference (P > 0.05) between cemented and uncemented fixation in the THR group. Obese patients had poorer outcomes following TKR but did not significantly influence the outcome following THR.Conclusion: Contrary to some literature, THR and TKR are equally efficacious in alleviating the pain and disability of OA when assessed using a comprehensive range of PROMs. The varying knee prosthesis types and hip fixation techniques did not significantly influence clinical outcome. Obesity had a greater influence on the outcome following TKR than that of THR

Performance of multi junction photovoltaic cells with high concentration ratio

AbstractConcentrating solar radiation on Photovoltaic (PV) has the potential to replace the expensive PV material with cheaper optical elements which also enhance the overall electrical output. The use of high solar concentration ratios with the triple junction III-V solar cells offers potential of high solar cell efficiency and power output. However, using high concentration ratios will increase the solar cell surface temperature which is inversely proportional to the PV electrical efficiency. This work investigates the effect of active cooling on the performance of triple junction PV cells with high solar concentration (up to 500X) in the harsh environment of Saudi Arabia where ambient temperatures can reach to 50o C in summer time, but with good clearance index of 0.6 and high yearly solar radiation of up to 2200 kWh/m2. Simulation results showed that as the concentration ratio increases, the effect of cooling on the PV efficiency increases

Effects of contact resistance and metal additives in finned-tube adsorbent beds on the performance of silica gel/water adsorption chiller

Recently interest in adsorption cooling systems has increased due to their capability to utilise low grade heat sources and environmentally friendly refrigerants. Currently, most of the commercially available adsorption cooling systems utilise granular packed adsorbent beds. Enhancing the heat transfer process inside the adsorbent bed will improve the overall efficiency of the adsorption system. Using recently developed empirical lumped analytical simulation model for a 450 kW two-bed silica gel/water adsorption chiller, this paper theoretically investigates the effects of various adsorbent bed heat transfer enhancement techniques on the adsorption system cooling capacity. Firstly, coating the first adsorbent layer to the metal part and packing the rest of adsorbent granules to eliminate the thermal contact resistance between heat exchanger metal and granules while keeping the same level of permeability. Secondly, adding metal particles to the adsorbent in order to enhance the granules thermal conductivity. The effective thermal conductivity of adsorbent/metal mixtures were determined and validated by comparing it with published experimental data. Also, the combined effect of using both techniques simultaneously was investigated. All these investigations were carried out at various adsorption bed fin spacing. Results of the combined techniques showed that the enhancement in the cooling capacity and system coefficient of performance (COP) increased with increasing the fin spacing ratio to reach maximum of 25% and 10% respectively at fin spacing ratio of 2

Adsorption Refrigeration Technologies

This chapter introduces a comprehensive overview about the principles, challenges and applications of adsorption refrigeration systems (ARSs), as a promising sustainable solution for many of cooling and heating applications. In addition to the features and the basics of ARSs, the following topics have been covered such as characteristics of working pairs, trends in improving the heat and mass transfer of the adsorber; advanced adsorption cycles and performance and operational data of some adsorption refrigeration applications. In some details, the operating range and the performance of ARSs are greatly affected by the employed working adsorbent/refrigerant pairs. Therefore, the study, development and optimum selection of adsorbent/refrigerant pairs, particularly the composite adsorbents, can lead to improving the performance and reliability of ARSs. Regarding the enhancement of heat and mass transfer in the adsorbent bed, two methods are commonly used: one is the development of adsorbents through different coating technologies or new materials such as metal-organic frameworks, and the second is the optimization of the adsorber geometrical parameters and cycle modes. Finally, a brief on some adsorption chillers applications have started to find their share in markets and driven by solar or waste heats

Tibiopedal arterial minimally invasive retrograde revascularization (TAMI) in patients with peripheral arterial disease and critical limb ischemia. On behalf of the Peripheral Registry of Endovascular Clinical Outcomes (PRIME)

Objectives and backgroundComplex peripheral arterial disease (PAD) and critical limb ischemia (CLI) are associated with high morbidity and mortality. Endovascular techniques have become prevalent in treatment of advanced PAD and CLI, and use of techniques such as tibiopedal minimally invasive revascularization (TAMI), have been proven safe in small, singleâ center series. However, its use has not been systematically compared to traditional approaches.Methods and resultsThis is a retrospective, multicenter analysis which enrolled 744 patients with advanced PAD and CLI who underwent 1,195 endovascular interventions between January 2013 and April 2018. Data was analyzed based on access used for revascularization: 840 performed via femoral access, 254 via dual access, and 101 via TAMI. The dual access group had the highest median Rutherford Class and lowest number of patent tibial vessels. Median fluoroscopy time, procedure time, hospital stay, and contrast volume were significantly lower in the TAMI access group when compared to both femoral/dual access groups. There was also a significant difference between all groups regarding location of target lesions: Femoropopliteal lesions were most commonly treated via femoral access; infrapopliteal lesions, via TAMI, and multilevel lesions via dual access.ConclusionsStandâ alone TAMI or tibial access as an integral part of a dual access treatment strategy, is safe and efficacious in the treatment of patients with advanced PAD and CLI who have infrapopliteal lesions. Larger prospective and randomized studies may be useful to further validate this approach.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154326/1/ccd28639.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154326/2/ccd28639_am.pd

Investigation of activated carbon/ethanol for low temperature adsorption cooling

Commercially available adsorption cooling systems use water/silica gel, water/zeolite and ammonia/ chloride salts working pairs. The water based pairs are limited to work above 0 °C due to the water high freezing temperature, while ammonia has the disadvantage of being toxic. Ethanol is a promising refrigerant due to its low freezing point (161 K), non-toxicity, zero ozone depletion and low global warming potential. Activated carbon (AC) is a porous material with high degree of porosity (500-3000 m2/g) that has been used in wide range of applications. Using Dynamic Vapour Sorption (DVS) test facility, this work characterizes the ethanol adsorption of eleven commercially available activated carbon materials for cooling at low temperature of - 15oC. DVS adsorption results show that Maxsorb has the best performance in terms of ethanol uptake and adsorption kinetics compared to the other tested materials. The Maxsorb/ethanol adsorption process has been numerically modeled using computational fluid dynamics (CFD) and simulation results are validated using the DVS experimental measurements. The validated CFD simulation of the adsorption process is used to predict the effects of adsorbent layer thickness and packing density on cycle uptake for evaporating temperature of -15oC. Simulation results show that as the thickness of the Maxsorb adsorbent layer increases, its uptake decreases. As for the packing density, the amount of ethanol adsorbed per plate increases with the packing density reaching maximum at 750 kg/m3. This work shows the potential of using Maxsorb/ethanol in producing low temperature cooling down to -15oC with specific cooling energy reaching 400kJ/kg