Proteome efficiency of metabolic pathways in Escherichia coli increases along the nutrient flow.

IMPORTANCE: Protein translation is the most expensive cellular process in fast-growing bacteria, and efficient proteome usage should thus be under strong natural selection. However, recent studies show that a considerable part of the proteome is unneeded for instantaneous cell growth in Escherichia coli. We still lack a systematic understanding of how this excess proteome is distributed across different pathways as a function of the growth conditions. We estimated the minimal required proteome across growth conditions in E. coli and compared the predictions with experimental data. We found that the proteome allocated to the most expensive internal pathways, including translation and the synthesis of amino acids and cofactors, is near the minimally required levels. In contrast, transporters and central carbon metabolism show much higher proteome levels than the predicted minimal abundance. Our analyses show that the proteome fraction unneeded for instantaneous cell growth decreases along the nutrient flow in E. coli.

Pulsatile Lavage Improves Tibial Cement Penetration and Implant Stability in Medial Unicompartmental Arthroplasty: A Cadaveric Study.

Cemented unicompartmental knee arthroplasty (UKA) shows good survivorship and function. However, implant failure, causing the need for revision, can occur. Aseptic loosening is still among the most common reasons for revision. The purpose of this study was to assess the influence of preimplantation lavage technique on tibial cement penetration depth, tibial cement volume, and load to fracture in the tibial component of mobile-bearing UKA. In 10 pairs of fresh frozen human tibiae, cemented UKA was implanted by an experienced surgeon. Tibial components were then implanted, left and right tibiae were randomly allocated to group A or B. Prior to implantation, irrigation was performed with either syringe lavage or pulsatile jet lavage in a standardized manner. Cement surface was 4170.2 mm2 (3271.6-5497.8 mm2) in the syringe lavage group, whereas the jet lavage group showed 4499.3 mm2 (3354.3-5809.1 mm2); cement volume was significantly higher as well (4143.4 mm3 (2956.6-6198.6 mm3) compared with 5936.9 mm3 (3077.5-8183.1 mm3)). Cement penetration depth was 2.5 mm (1.7-3.2 mm) for the jet lavage, and 1.8 mm (1.2-2.4 mm) for the syringe lavage. The mean fracture load was 4680 N in the jet lavage group and 3800 N in the syringe lavage group (p = 0.001). Subsidence was significantly higher for syringe lavage. This study suggests a correlation of cement penetration depth and cement volume to implant failure in the tibial component of a UKA using a cadaveric model. The type of bone lavage most likely influences these two key parameters.

Accuracy measurement of different marker based motion analysis systems for biomechanical applications: A round robin study.

INTRODUCTION: Multiple camera systems are widely used for 3D-motion analysis. Due to increasing accuracies these camera systems gained interest in biomechanical research areas, where high precision measurements are desirable. In the current study different measurement systems were compared regarding their measurement accuracy. MATERIALS AND METHODS: Translational and rotational accuracy measurements as well as the zero offset measurements of seven different measurement systems were performed using two reference devices and two different evaluation algorithms. All measurements were performed in the same room with constant temperature at the same laboratory. Equal positions were measured with the systems according to a standardized protocol. Measurement errors were determined and compared. RESULTS: The highest measurement errors were seen for a measurement system using active ultrasonic markers, followed by another active marker measurement system (infrared) having measurement errors up to several hundred micrometers. The highest accuracies were achieved by three stereo camera systems, using passive 2D marker points having errors typically below 20 µm. CONCLUSIONS: This study can help to better assess the results obtained with different measurement systems. With the focus on the measurement accuracy, only one aspect in the selection of a system was considered. Depending on the requirements of the user, other factors like measurement frequency, the maximum analyzable volume, the marker type or the costs are important factors as well.

Taper corrosion in total hip arthroplasty - How to assess and which design features are crucial?

BACKGROUND: In total hip replacement, wear and corrosion arising from modular taper connections have increasingly become a serious clinical concern. Previous studies led to confounding results regarding the role of specific taper design features, likely due to the application of different analytical approaches. Accordingly, this study has two major objectives: first, to evaluate different analytical approaches to evaluate the fretting-corrosion behavior; and secondly to determine the effect of four specific design variables: the taper engagement situation, the stem taper length and surface topography in terms of roughness and contact ratio. METHODS: An in vitro fretting-corrosion test setup was used including an aggressive solution. Cyclic loading was applied, varying from 300 N to 2500 N at a frequency of 3 Hz. Taper dummies covering different implant designs were tested in seven different test groups. Different quantitative and qualitative analytical test methods such as electrochemical characterization, ion analysis, gravimetry and corrosion scoring were applied in order to quantify the material degradation. RESULTS: A stepwise linear regression analysis showed that the taper engagement situation is the predominant factor that predicts the metal ion release from the taper connection, followed by the contact ratio of the taper surface and subsequently the taper length. A distal taper engagement situation, as well as a high contact ratio and a short taper length are the relevant parameters that decrease the metal ion release. Hereby, metal ion analysis turned out to be the most precise and reliable method for determining corrosive driven material loss, followed by gravimetry. CONCLUSION: It was found that the taper engagement length is the major design parameter that influences the total ion release. It further turned out, that the selection of an appropriate analytical approach is essential for the evaluation of the corrosion behavior of taper connections in an experimental setting.

Does Kinematic Alignment Increase Polyethylene Wear Compared With Mechanically Aligned Components? A Wear Simulation Study.

BACKGROUND: Kinematic alignment is an alternative approach to mechanical alignment. Kinematic alignment can restore the joint line to its prearthritic condition, and its advocates have suggested it may be associated with other benefits. But this alignment approach often results in tibial components that are placed in varus and femoral components that are placed in valgus alignment, which may result in an increased risk of component loosening because of wear. Like malaligned implant components, kinematically aligned knee implants could increase wear in vivo, but we lack comparative data about wear behavior between these approaches. QUESTIONS/PURPOSES: (1) Do the different alignment approaches (kinematic, mechanical, and purposefully malaligned components) result in different wear rates in a wear simulator? (2) Do the different alignment approaches lead to different worn areas on the polyethylene inserts in a wear simulator? (3) Do the different alignment approaches result in different joint kinematics in a wear simulator? METHODS: Mechanical alignment was simulated in a force-controlled manner with a virtual ligament structure according to the International Organization for Standardization (ISO 14243-1) using a knee wear simulator. To simulate kinematic alignment, flexion-extension motion, internal-external torque, and the joint line were tilted by 4°, using a novel mechanical setup, without changing the force axis. The setup includes bearings with inclinations of 4° so that the joint axis of 4° is determined. To verify the angle of 4°, a digital spirit level was used. To simulate malalignment, we tilted the implant and, therefore, the joint axis by 4° using a wedge with an angle of 4° without tilting the torque axes of the simulator. This leads to a purposefully malaligned tibial varus and femoral valgus of 4°. For each condition, three cruciate-retaining knee implants were tested for 3.0 x 10 6 cycles, and one additional implant was used as soak control. Gravimetric wear analyses were performed every 0.5 x 10 6 cycles to determine the linear wear rate of each group by linear regression. The wear area was measured after 3.0 x 10 6 cycles by outlining the worn areas on the polyethylene inserts, then photographing the inserts and determining the worn areas using imaging software. The joint kinematics (AP translation and internal-external rotation) were recorded by the knee simulator software and analyzed during each of the six simulation intervals. RESULTS: Comparing the wear rates of the different groups, no difference could be found between the mechanical alignment and the kinematic alignment (3.8 ± 0.5 mg/million cycles versus 4.1 ± 0.2 mg/million cycles; p > 0.99). However, there was a lower wear rate in the malaligned group (2.7 ± 0.2 mg/million cycles) than in the other two groups (p < 0.01). When comparing the total wear areas of the polyethylene inserts among the three different alignment groups, the lowest worn area could be found for the malaligned group (716 ± 19 mm 2 ; p ≤ 0.003), but there was no difference between kinematic alignment and mechanical alignment (823 ± 19 mm 2 versus 825 ± 26 mm 2 ; p > 0.99). Comparing the AP translation, no difference was found between the mechanical alignment, the kinematic alignment, and the malalignment group (6.6 ± 0.1 mm versus 6.9 ± 0.2 mm versus 6.8 ± 0.3 mm; p = 0.06). In addition, the internal-external rotation between mechanical alignment, kinematic alignment, and malalignment also revealed no difference (9.9° ± 0.4° versus 10.2° ± 0.1° versus 10.1° ± 0.6°; p = 0.44). CONCLUSION: In the current wear simulation study, the wear rates of mechanical alignment and kinematic alignment of 4° were in a comparable range. CLINICAL RELEVANCE: The results suggest that kinematic alignment with up to 4° of component inclination may give the surgeon confidence that the reconstruction will have good wear-related performance when using a modern cruciate-retaining implant. The malaligned group had the lowest wear rate, which may be a function of the smaller worn area on the inserts compared with the other two alignment groups. This smaller articulation area between the femoral condyles and polyethylene insert could increase the risk of delamination of malaligned components over longer test durations and during high-load activities. For that reason, and because malalignment can cause nonwear-related revisions, malalignment should be avoided. Further in vitro and clinical studies must prove whether the wear simulation of different alignments can predict the wear behavior in vivo.

Post-discharge Mortality in Patients With Delirium and Dementia: A 3-Year Follow Up Study.

Background: Delirium and dementia are prominent psychiatric diseases in old age and connected with poor outcomes for people affected. Nevertheless, there is a lack of knowledge concerning the long-term prognosis of patients with dementia and delirium. This study analyzes mortality, readmission rates and discharge destinations of patients with dementia or delirium superimposed on dementia (DSD) within 3 years after discharge from hospital. Methods: A cross-sectional, monocentric cohort study was conducted at the department of geriatric psychiatry of the LVR hospital cologne, using structured telephone interviews and analyses from the clinical information system. All patients with dementia and DSD, admitted between December 2014 and November 2015, were screened for eligibility. Results: In total, 113 patients were included, 49 patients with dementia (M 80 years, female 49%) and 64 with DSD (M 82 years, female 47%). Three years after discharge, 66 patients (58%) had died (95% CI 91.9-112.5; p = 0.53). Within the first 3 months, 9 patients (14%) with DSD deceased, but no patient from the dementia group (95% CI 11.3-12.7; p = 0.01). Out of all patients, 17 patients were readmitted and nursing homes were the predominant discharge destination (55%). Conclusions: This analysis revealed a high post-discharge mortality rate of patients with dementia and DSD. For patients with DSD, a close clinical monitoring, mainly within the first 3 months after discharge, should challenge the significantly increased acute-mortality. These findings should set the pattern for a comprehensive analysis of long-term effects of dementia and DSD. More studies are required for better understanding and comparability in this field of research and healthcare.

Wear investigation based on a novel, anatomic shoulder prosthesis with bearing materials inversion.

INTRODUCTION: In shoulder arthroplasty, ultra-high-molecular-weight polyethylene is used as standard material for glenoid components. The emergence of wear particles and their influence on the aseptic loosening of joint replacements are well known. The aim of the present study is to investigate the wear behaviour of the implant combinations as well as the size and morphology of the released wear particles from novel anatomic shoulder prosthesis. Here, the main interest lies on the influence of material inversion and different conformities on wear behaviour. METHODS: Wear simulation was performed using a force-controlled joint simulator. The Modular-Shoulder-System from Permedica S.p.A. Orthopaedics was studied. Polyethylene wear was determined gravimetrically and was characterised by particle analysis. An abduction-adduction motion of 0°-90° lifting a load of 2 kg superimposed by an ante-/retroversion was chosen as the activity. In addition, an extreme test was performed to simulate subluxation of the joint. RESULTS: The results showed a wear reduction of approximately 70% and a significant decrease in the total number of wear particles due to the material inversion on the bearing materials. No reduction of wear could be determined by varying the conformity of the bearing partners. In the simulated subluxation, the material inversion shows an increase in wear. CONCLUSION: Compared to similarly investigated systems, the Modular-Shoulder-System shows a reduction in wear. This reduction shows that material inversion may lead to a wear reduction. However, if subluxation of the humeral head occurs more frequently, increased material wear can be expected with the Modular-Shoulder-System. An influence of the conformity on the wear behaviour could not be determined.

One year with the COVID-19 pandemic - Lessons learnt? Intersectoral collaboration measures established during the crisis could benefit capacity and patient flow management in daily clinical practice.

PURPOSE: The COVID-19 pandemic has changed the way hospitals work. Strategies that were detached from the boundaries of departments and responsibilities in the COVID-19 pandemic have proven themselves under extreme conditions and show a beneficial influence on patient flow and resource management as well as on the communication culture. The continuation of closer interdisciplinary and cross-sectoral co-operation in a "new clinical routine" could have a positive impact on personnel concepts, communication strategies, and the management of acute care capacities and patient pathways. DESIGN/METHODOLOGY/APPROACH: The aim of the paper is to critically discuss the knowledge gained in the context of the COVID-19 pandemic from the various approaches in patient flow and capacity management as well as interdisciplinary co-operation. More recent research has evaluated patient pathway management, personnel planning and communication measures with regard to their effect and practicability for continuation in everyday clinical practice. FINDINGS: Patient flows and acute care capacities can be more efficiently managed by continuing a culture change towards closer interdisciplinary and intersectoral co-operation and technologies that support this with telemedicine functionalities and regional healthcare data interoperability. Together with a bi-directional, more frequent and open communication and feedback culture, it could form a "new clinical routine". ORIGINALITY/VALUE: This paper discusses a holistic approach on the way away from silo thinking towards cross-departmental collaboration.

Amorphous Carbon Coatings for Total Knee Replacements-Part II: Tribological Behavior.

Diamond-like carbon coatings may decrease implant wear, therefore, they are helping to reduce aseptic loosening and increase service life of total knee arthroplasties (TKAs). This two-part study addresses the development of such coatings for ultrahigh molecular weight polyethylene (UHMWPE) tibial inlays as well as cobalt-chromium-molybdenum (CoCr) and titanium (Ti64) alloy femoral components. While the deposition of a pure (a-C:H) and tungsten-doped hydrogen-containing amorphous carbon coating (a-C:H:W) as well as the detailed characterization of mechanical and adhesion properties were the subject of Part I, the tribological behavior is studied in Part II. Pin-on-disk tests are performed under artificial synovial fluid lubrication. Numerical elastohydrodynamic lubrication modeling is used to show the representability of contact conditions for TKAs and to assess the influence of coatings on lubrication conditions. The wear behavior is characterized by means of light and laser scanning microscopy, Raman spectroscopy, scanning electron microscopy and particle analyses. Although the coating leads to an increase in friction due to the considerably higher roughness, especially the UHMWPE wear is significantly reduced up to a factor of 49% (CoCr) and 77% (Ti64). Thereby, the coating shows continuous wear and no sudden failure or spallation of larger wear particles. This demonstrated the great potential of amorphous carbon coatings for knee replacements.

Duration of antibiotic treatment using procalcitonin-guided treatment algorithms in older patients: a patient-level meta-analysis from randomized controlled trials.

BACKGROUND: Older patients have a less pronounced immune response to infection, which may also influence infection biomarkers. There is currently insufficient data regarding clinical effects of procalcitonin (PCT) to guide antibiotic treatment in older patients. OBJECTIVE AND DESIGN: We performed an individual patient data meta-analysis to investigate the association of age on effects of PCT-guided antibiotic stewardship regarding antibiotic use and outcome. SUBJECTS AND METHODS: We had access to 9,421 individual infection patients from 28 randomized controlled trials comparing PCT-guided antibiotic therapy (intervention group) or standard care. We stratified patients according to age in four groups (<75 years [n = 7,079], 75-80 years [n = 1,034], 81-85 years [n = 803] and >85 years [n = 505]). The primary endpoint was the duration of antibiotic treatment and the secondary endpoints were 30-day mortality and length of stay. RESULTS: Compared to control patients, mean duration of antibiotic therapy in PCT-guided patients was significantly reduced by 24, 22, 26 and 24% in the four age groups corresponding to adjusted differences in antibiotic days of -1.99 (95% confidence interval [CI] -2.36 to -1.62), -1.98 (95% CI -2.94 to -1.02), -2.20 (95% CI -3.15 to -1.25) and - 2.10 (95% CI -3.29 to -0.91) with no differences among age groups. There was no increase in the risk for mortality in any of the age groups. Effects were similar in subgroups by infection type, blood culture result and clinical setting (P interaction >0.05). CONCLUSIONS: This large individual patient data meta-analysis confirms that, similar to younger patients, PCT-guided antibiotic treatment in older patients is associated with significantly reduced antibiotic exposures and no increase in mortality.

Taper junctions in modular hip joint replacements: What affects their stability?

BACKGROUND: Although taper junctions are beneficial in the reconstruction of hip joints, some clinical concerns like the formation of adverse local tissue reactions have recently emerged. These reactions are associated with wear and corrosion products from the interface of insufficient taper connections regarding strength. Commonly used tapers vary in their geometric and topographical design parameter. Therefore, this study aims to evaluate interactions between design and surgical related parameters to the taper connection strength. METHODS: In this study, the effect of the taper contact situation, surface roughness and head material in combination with assembly force on the taper connection strength were assessed using torque-off tests. Furthermore, the type of use in terms of single-use or re-use of the stem taper was investigated. RESULTS: The study showed that the impaction force is the predominant factor that determines the taper strength followed by the type of use and the head material. The contact situation seems to slightly influence the determined torque-off moment, whereas the surface topography of the stem taper obviously plays a minor role for the taper connection strength. CONCLUSION: Clinical users should be aware that an increased assembly force will strengthen the stability of the taper junction, whereas care should be taken when reusing hip stems with metal heads as this may decrease their connection strength.

Rheological behavior of an artificial synovial fluid - influence of temperature, shear rate and pressure.

Despite the excellent clinical performance of joint replacements, wear-induced aseptic loosening is a main cause of premature implant failure. Tribological testing is usually carried out using bovine serum as an artificial synovial fluid. In order to gain new insights into the suitability to simulate human synovial fluid and provide recommendations for the conditions of tribological testing, accurate rheological measurements on the influence of temperature, shear rate and pressure on density and viscosity were performed. Thus, a temperature dependence of density and viscosity could be verified, whereas both values decreased with higher temperatures. The temperature dependency of viscosity could be approximated by an Arrhenius model. Moreover, shear-thinning characteristics could be demonstrated and fitted to a Cross model, which agreed well with investigations on human synovial fluid reported in literature. Furthermore, an anomaly of pressure dependence of viscosity was found and correlated with the behavior of water as a main constituent. At room temperature, the viscosity initially decreased to a minimum and then increased again as a function of pressure. This was no longer distinct at human body temperatures. Consequently, the present study confirms the suitability of bovine serum as a substitute synovial fluid and emphasizes the importance of realistic testing conditions in order to ensure transferability and comparability.

Quantitative Measurements of Backside Wear in Acetabular Hip Joint Replacement: Conventional Polyethylene Versus Cross-Linked Polyethylene.

As shown in previous studies, the modification of conventional polyethylene (CPE) to cross-linked polyethylene (XLPE) and the contribution of antioxidants result in a reduction in total wear. The aim of this study was to evaluate XLPE inserts with vitamin E and CPE regarding their resistance to the backside wear mechanism. A cementless hip cup system (Plasmafit® Plus 7, Aesculap) was dynamically loaded using CPE and XLPE inserts. The backside wear was isolated, generated and collected using the two-chamber principle. The chambers were filled with ultrapure water. After 2 × 106 cycles, the fluids were examined for wear particles according to a particle analysis. Using XLPE inserts, the backside wear was significantly reduced by 35%. While XLPE backside wear particles are significantly larger than CPE particles, they do not differ in their morphology. This study confirms the greater resistance to backside wear of XLPE compared to CPE. It can be assumed that the improved fatigue resistance of the vitamin E-stabilized XLPE inserts demonstrates XLPE's effectiveness against micro-motion and the resulting changing tensions in interface areas like surface breakdown, pitting and the release of very small particles.

Comparison of Different Locking Mechanisms in Total Hip Arthroplasty: Relative Motion between Cup and Inlay.

The resulting inflammatory reaction to polyethylene (PE) wear debris, which may result in osteolysis, is still considered to be a main reason for aseptic loosening. In addition to the primary wear in hip joint replacements caused by head-insert articulation, relative motions between the PE liner and the metal cup may cause additional wear. In order to limit this motion, various locking mechanisms were used. We investigated three different locking mechanisms (Aesculap, DePuy, and Zimmer Biomet) to address the resulting relative motion between the acetabular cup and PE liner and the maximum disassembly force. A standardized setting with increasing load levels was used in combination with optically based three-dimensional measurements. In addition the maximum disassembly forces were evaluated according to the ASTM F1820-13 standard. Our data showed significant differences between the groups, with a maximum relative motion at the maximum load level (3.5 kN) of 86.5 ± 32.7 µm. The maximum axial disassembly force was 473.8 ± 94.6 N. The in vitro study showed that various locking mechanisms may influence cup-inlay stability.

Understanding the use of observational and randomized data in cardiovascular medicine.

The availability of large datasets from multiple sources [e.g. registries, biobanks, electronic health records (EHRs), claims or billing databases, implantable devices, wearable sensors, and mobile apps], coupled with advances in computing and analytic technologies, have provided new opportunities for conducting innovative health research. Equally, improved digital access to health information has facilitated the conduct of efficient randomized controlled trials (RCTs) upon which clinical management decisions can be based, for instance, by permitting the identification of eligible patients for recruitment and/or linkage for follow-up via their EHRs. Given these advances in cardiovascular data science and the complexities they behold, it is important that health professionals have clarity on the appropriate use and interpretation of observational, so-called 'real-world', and randomized data in cardiovascular medicine. The Cardiovascular Roundtable of the European Society of Cardiology (ESC) held a workshop to explore the future of RCTs and the current and emerging opportunities for gathering and exploiting complex observational datasets in cardiovascular research. The aim of this article is to provide a perspective on the appropriate use of randomized and observational data and to outline the ESC plans for supporting the collection and availability of clinical data to monitor and improve the quality of care of patients with cardiovascular disease in Europe and provide an infrastructure for undertaking pragmatic RCTs. Moreover, the ESC continues to campaign for greater engagement amongst regulators, industry, patients, and health professionals in the development and application of a more efficient regulatory framework that is able to take maximal advantage of new opportunities for improving the design and efficiency of observational studies and RCT in patients with cardiovascular disease.

Carbon-fibre-reinforced PEEK: An alternative material for flexion bushings of rotating hinged knee joints?

BACKGROUND: For prosthetic knee joints of the hinged type, typically polyethylene (PE) flexion bushings are used between axis and femoral component to prevent metallic wear. Nevertheless, PE-wear can lead to periprosthetic osteolysis followed by aseptic loosening of the implant. Based on high creep and wear resistance carbon-fibre-reinforced polyether ether ketones (CFR-PEEKs) could provide an alternative material to ultra-high-molecular-weight polyethylene (UHMWPE) for this bearing type. METHODS: Flexion bushings of four different materials were investigated (CFR-PEEK pitch fibres, CFR-PEEK PAN fibres, virgin PEEK without carbon fibres and UHMWPE) using a bushing tester. For determination of the polymeric and metallic wear, gravimetric measurements and particle analyses were performed. RESULTS: The polymeric wear rates of CFR-PEEK PAN (6.657 ±â€¯0.714 mg/106 cycles) and CFR-PEEK pitch (32.085 ±â€¯2.748 mg/106 cycles) were significantly higher compared to the polymeric wear rates of virgin PEEK (0.764 ±â€¯0.283 mg/106 cycles) or UHMWPE (-0.015 ±â€¯0.011 mg/106 cycles) (p < .001). In addition, the metallic wear rates were significantly higher when using bushings made of CFR-PEEK PAN (3.373 ±â€¯0.214 mg/106 cycles) and CFR-PEEK pitch (3.604 ±â€¯0.355 mg/106 cycles), than when using bushings made of virgin PEEK (0.177 ±â€¯0.049 mg/106 cycles) or UHMWPE (0.031 ±â€¯0.011 mg/106 cycles) (p < .001). The mean particle size of the two CFR-PEEK groups was significantly smaller compared to the virgin PEEK and UHMWPE group (p < .001). CONCLUSION: According to these results, the clinical use of CFR-PEEK in combination with CoCr could lead to higher wear rates and this should be avoided. Virgin PEEK may still be considered as an alternative to UHMWPE to use it for flexion bushings in a hinged knee joint.

Particle analysis of shape factors according to American Society for Testing and Materials.

Polyethylene wear is one of the major factors influencing the survivorship of joint replacements. Depending on the number, size and morphology of the polyethylene particles, biological responses of the periprosthetic soft tissue in terms of inflammatory processes can occur, leading to loosening of the implant. Various parameters are used to analyze wear particles, which are usually determined by examining scanning electron microscopy (SEM) images with a particle analysis program. In this study, three different software solutions for particle analysis (self-developed Particleanalyzer_HD, Leica QWin and ImageJ) were compared regarding particle number, size and morphology. These solutions were also compared to the American Society for Testing and Materials (ASTM) F1877-16 specifications regarding particle morphology. SEM image analysis revealed no differences for the equivalent circle diameter (p = 0.969). However, a significant difference was found for the aspect ratio between the Particleanalyzer_HD and the other two software solutions (p < 0.001) and between Leica QWin and the other two software solutions regarding the roundness (p < 0.001). Only the Particleanalyzer_HD showed an excellent agreement with the ASTM standard for both morphology parameters (intraclass correlation = 1.000). Only the Particleanalyzer_HD calculated the two morphology parameters according to the ASTM standard. A comparison of the particle morphology between different studies is barely possible, as different algorithms for particle analysis are used. It is strongly recommended that the calculation according to the ASTM standard is used to improve future comparability of findings from wear analysis studies. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:225-233, 2020.

Backside wear, particle migration and effectiveness of screw hole plugs in acetabular hip joint replacement with cross-linked polyethylene.

In total hip arthroplasty, osteolysis of the acetabulum often occurs at the backside of cups in the area of screw holes, indicating a clinically relevant amount of polyethylene (PE) wear particles in this area. In order to avoid a possible migration of wear particles to the acetabulum-bone, screw hole plugs are provided for some implant systems. The aims of this study were to quantitatively determine backside wear and to investigate the migration behaviour of articulation-related wear particles in a cup system with open and closed screw holes by plugs. Titanium cup systems with backside holes for screw fixations were sinusoidally loaded with 2.7 kN. The articulation area was separated from the backside area of the cup. A defined amount of articulation-generated particles was added to the fluid of the articulation chamber. The fluids in the two chambers were separately filtered after 2 × 106 cycles for a particle analysis. Backside wear with noticeably small (65.6 ±â€¯4.2 nm) and round PE particles was identified. With both open and closed screw holes, a migration of the articulating wear particles from the articulation area behind the cup could be observed. Backside wear was estimated to be below 1% of the articulated wear. Screw hole plugs did not effectively prevent the migration of PE wear particles behind the investigated cups. STATEMENT OF SIGNIFICANCE: Backside wear occurs in a proven cup-system. Furthermore, it was quantitatively observed that articulation-generated wear products could migrate from the articulating area along the cup/liner-interface through the screw holes behind the cup. An almost unimpeded particle migration to the acetabulum-bone, in conjunction with very small backside wear particles, could produce a clinically relevant amount of PE with respect to pelvic lysis. These findings highlight the importance of management to avoid particle migration in artificial hip cups. Therefore, primarily the use of screw hole plugs, as far as available for the respective cup-system, is recommended. The aim of avoiding particle migration by plugs, but also by using a sophisticated anchoring mechanism between cup and PE liner should continue in future.

How prosthetic design influences knee kinematics: a narrative review of tibiofemoral kinematics of healthy and joint-replaced knees.

INTRODUCTION: To improve the total knee arthroplasty (TKA) prosthesis design, it is essential to study the kinematics of the tibiofemoral joint. Many studies have been conducted in this area; however, conflicting results and incomparable testing methods make it difficult to draw definitive conclusions or compare research from studies. The goal of this article is to introduce what is known about both healthy and prosthetic tibiofemoral joint kinematics. AREAS COVERED: Healthy tibiofemoral joint kinematics are reviewed in vivo by different activities, and the kinematics of existing knee prosthetic design features are considered separately. These features include but are not limited to cruciate retaining, posterior cruciate substituting, mobile-bearing, and high flexion. EXPERT COMMENTARY: The type of activity that is being performed has a great influence on the kinematics of healthy knees, and the influences of different TKA prosthetic design features on the kinematics are complex and varied. Moreover, the TKA postoperative functional performance is influenced by many factors, and prosthetic design is among them, but not the only one that defines the performance.

Backside wear in acetabular hip joint replacement.

INTRODUCTION: Besides head-insert articulation in hip joint replacements, micro-motions between the backside of assembled polyethylene acetabular liners and the metal cup may cause additional wear. Pelvic osteolysis frequently occurs in the region of screw holes, and cup loosening hints to clinically relevant amounts of polyethylene backside wear. It has yet to be confirmed whether backside wear particles differ in size and morphology compared to articulating wear. Previous methods have been limited to subjective assessment of backside surface damages without consideration of wear debris. The aim of this study was to develop and validate a method for quantitative in vitro measurements of polyethylene backside wear in artificial hip cups and to characterize these wear particles for the first time. METHODS: Titanium cup-systems (Plasmafit®Plus7, Aesculap, UHMWPE liner) were sinusoidally loaded (2.5 kN) and a torque of 5 Nm was simultaneously applied. The front and rear side of the cup were separated to isolate backside wear. After 2 × 106 cycles the surrounding fluid was filtered and a particle analysis was performed. RESULTS: Backside wear had a particles size of 64.1 ±â€¯1.9 nm and was verified as round and oval particles with partly rough outlines. An estimated total number of particles of 1.26 × 109 ±â€¯1.67 × 108 per 106 cycles was determined. CONCLUSION: Backside wear was estimated to be several times lower than published values of articulating wear. However, polyethylene backside wear particles represented significantly smaller particles with partly roughened outlines than articulating wear particles and may therefore cause higher biological response in macrophage-mediated bone resorption compared to articulated particles. STATEMENT OF SIGNIFICANCE: Within this study, an analytical method for quantitative measuring polyethylene backside wear of artificial hip cups was successfully developed and validated for the first time. It could be shown that backside wear is still present, even in modern cup-systems. These findings can be further used for investigations of the osteolytic potential of polyethylene particles, for evaluating and improving new implant systems and to evaluate the effectiveness of screw hole plugs to prevent the particle migration to the acetabulum.