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The ability to enrol for protection is an effective defensive strategy that has convergently evolved multiple times in disparate animal groups ranging from euarthropods to mammals. Enrolment is a staple habit of trilobites, and their biomineralized dorsal exoskeleton offered a versatile substrate for the evolution of interlocking devices. However, it is unknown whether trilobites also featured ventral adaptations for enrolment. Here, we report ventral exoskeletal adaptations that facilitate enrolment in exceptionally preserved trilobites from the Middle Ordovician Walcott–Rust Quarry in New York State, USA. Walcott–Rust trilobites reveal the intricate three-dimensional organization of the non-biomineralized ventral anatomy preserved as calcite casts, including the spatial relationship between the articulated sternites (i.e. ventral exoskeletal plates) and the wedge-shaped protopodites. Enrolment in trilobites is achieved by ventrally dipping the anterior margin of the sternites during trunk flexure, facilitated by the presence of flexible membranes, and with the close coupling of the wedge-shaped protopodites. Comparisons with the ventral morphology of extant glomerid millipedes and terrestrial isopods reveal similar mechanisms used for enrolment. The wedge-shaped protopodites of trilobites closely resemble the gnathobasic coxa/protopodite of extant horseshoe crabs. We propose that the trilobites' wedge-shaped protopodite simultaneously facilitated tight enrolment and gnathobasic feeding with the trunk appendages. [ABSTRACT FROM AUTHOR]

Background: Migraine and depression are two of the most common and debilitating conditions. From a clinical perspective, they are mostly prevalent in women and manifest a partial overlapping symptomatology. Despite the high level of comorbidity, previous studies hardly investigated possible common patterns in brain volumetric differences compared to healthy subjects. Therefore, the current study investigates and compares the volumetric difference patterns in sub-cortical regions between participants with migraine or depression in comparison to healthy controls. Methods: The study included data from 43 930 participants of the large UK Biobank cohort. Using official ICD10 diagnosis, we selected 712 participants with migraine, 1 853 with depression and 23 942 healthy controls. We estimated mean volumetric difference between the groups for the different sub-cortical brain regions using generalized linear regression models, conditioning the model within the levels of BMI, age, sex, ethnical background, diastolic blood pressure, current tobacco smoking, alcohol intake frequency, Assessment Centre, Indices of Multiple Deprivation, comorbidities and total brain volume. Results: We detected larger overall volume of the caudate (mean difference: 66, 95% CI [-3, 135]) and of the thalamus (mean difference: 103 mm3, 95% CI [-2, 208]) in migraineurs than healthy controls. We also observed that individuals with depression appear to have also larger overall (mean difference: 47 mm3, 95% CI [-7, 100]) and gray matter (mean difference: 49 mm3, 95% CI [2, 95]) putamen volumes than healthy controls, as well as larger amygdala volume (mean difference: 17 mm3, 95% CI [-7, 40]). Conclusion: Migraineurs manifested larger overall volumes at the level of the nucleus caudate and of the thalamus, which might imply abnormal pain modulation and increased migraine susceptibility. Larger amygdala and putamen volumes in participants with depression than controls might be due to increased neuronal activity in these regions. [ABSTRACT FROM AUTHOR]

Background: Thymic malignancies are a heterogeneous group of rare cancers for which systemic chemotherapy is the standard treatment in the setting of advanced, recurrent or refractory diseases. Both environmental and genetic risk factors have not been fully clarified and few target-specific drugs have been developed for thymic epithelial tumors. A major challenge in studying thymic epithelial tumors is the lack of preclinical models for translational studies. Main body: Starting from bioptic material of two consecutive recurrences of the same patient, we generated two patient-derived xenografts. The patient-derived xenografts models were characterized for histology by immunohistochemistry and mutations using next-generation sequencing. When compared to the original tumors resected from the patient, the two patient-derived xenografts had preserved morphology after the stain with hematoxylin and eosin, although there was a moderate degree of de-differentiation. From a molecular point of view, the two patient-derived xenografts maintained 74.3 and 61.8% of the mutations present in the human tumor of origin. Short conclusion: The newly generated patient-derived xenografts recapitulate both the molecular characteristics and the evolution of the thymoma it derives from well, allowing to address open questions for this rare cancer. [ABSTRACT FROM AUTHOR]

Objectives: The anatomical features of the atlanto‐occipital joint can be potentially useful in re‐associating or excluding crania to atlases in commingled remains. This study investigated whether linear measurements and the 3‐dimensional (3D) surface of occipital condyles and articular facets of atlases can represent valid insights for this purpose. Methods: The variations among eight corresponding linear distances were analyzed in a sample of 150 individuals through six supervised machine learning techniques attempting to develop classifiers able to identify elements belonging to the same individual. Furthermore, a 3D analysis was conducted on the articular surfaces through superimpositions of 3D models of corresponding and non‐corresponding crania and atlases obtained by using respectively stereophotogrammetry and laser scanning. This analysis investigated differences in terms of point‐to‐point distances (Root Mean Square, RMS) of superimposed 3D surfaces. Results: None of the six machine learning techniques were able to correctly detect a satisfying percentage of correspondent pairs in the overall sample by using the linear variables. The 3D analysis of the articular surfaces found RMS values over 0.53 mm only for superimposed non‐corresponding surfaces, which sets a threshold value to identify 32% of incorrect pairs. Discussion: The re‐association of cranium to atlas proved to be challenging and hardly possible when considering only metric variables. However, the 3D geometry of the articular surfaces represents a valid variable for this purpose and 3D analyses pave the way for an initial exclusion of incorrect re‐associations, thus should not be considered as a re‐association method per se, but as an exclusionary screening technique. [ABSTRACT FROM AUTHOR]

Background: Migraine represents one of the most prevalent neurological conditions worldwide. It is a disabling condition with high impact on the working situation of migraineurs. Interestingly, gender-related differences regarding an association of migraine with important occupational characteristics has been hardly studied. Methods: The current study scrutinizes gender-specific differences in the prevalence of migraine across a broad spectrum of occupational categories, shedding also light on associations with important job-related features such as shift work, job satisfaction, and physical activity. The study included data from 415 712 participants from the UK Biobank cohort, using the official ICD10 diagnosis of migraine and other health conditions as selection criteria. Prevalence ratios of migraineurs compared to healthy controls among different occupational categories and job-related variables were estimated using log-binomial regression analyses. Statistical models were adjusted for important sociodemographic features such as age, BMI, ethnicity, education and neuroticism. To better highlight specific differences between men and women we stratified by sex. Results: We detected a differential prevalence pattern of migraine in relation to different job categories between men and women. Especially in men, migraine appears to be more prevalent in highly physically demanding occupations (PR 1.38, 95% CI [0.93, 2.04]). Furthermore, migraine is also more prevalent in jobs that frequently involve shift or night shift work compared to healthy controls. Interestingly, this prevalence is especially high in women (shift work PR 1.45, 95% CI [1.14, 1.83], night shift work PR 1.46, 95% CI [0.93, 2.31]). Conclusion: Our results show that migraine is genderdependently associated with physically demanding jobs and shift working. [ABSTRACT FROM AUTHOR]

The terminology "vitreous cortex remnants" (VCR) indicates the outermost lamellae of vitreous cortex that remains attached to the retinal surface as a consequence of vitreoschisis. The relevance of VCR removal in eyes with rhegmatogenous retinal detachment (RRD) is unknown. We conducted a review from January 1, 2000, to July 30, 2023, examining 1493 eyes. Outcome measures included: prevalence of VCR, relationship between VCR and detachment recurrence due to proliferative vitreoretinopathy (PVR), and relationship between VCR and epiretinal membrane (ERM) formation. A meta-analysis was performed with data reported as odds ratios (OR) or mean difference and 95 % confidence intervals. Prevalence of macular and peripheral VCR was 53.4 and 46.8, respectively, with an overall VCR prevalence of 50.8 (95 % CI 42.6, 59.1) Given the scarcity of available data, meta-analysis regarding the relationship between peripheral VCR and redetachment due to PVR was not feasible. The odds of developing ERM were not statistically different between eyes that had had macular VCR removal vs. eyes that had not (log OR −0.08 [95 % CI −1.06, 0.89 p= 0.89]. Additional prospective studies are required to verify whether removal of VCR may reduce the odds of recurrence of RRD due to PVR and the development of ERM. [ABSTRACT FROM AUTHOR]

Background: Migraine and depression are highly prevalent and partly overlapping disorders that cause strong limitations in daily life. Patients tend to respond poorly to the therapies available for these diseases. OnabotulinumtoxinA has been proven to be an effective treatment for both migraine and depression. While many studies have addressed the effect of onabotulinumtoxinA in migraine or depression separately, a growing body of evidence suggests beneficial effects also for patients comorbid with migraine and depression. The current meta-analysis systematically investigates to what extent onabotulinumtoxinA is efficient in migraineurs with depression.Methods: A systematic literature search was performed based on PubMed, Scopus and Web of Science from the earliest date till October [Formula: see text], 2020. Mean, standard deviation (SD) and sample size have been used to evaluate improvement in depressive symptoms and migraine using random-effects empirical Bayes model.Results: Our search retrieved 259 studies, eight of which met the inclusion criteria. OnabotulinumtoxinA injections administered to patients with both chronic migraine and major depressive disorder led to mean reduction of [Formula: see text] points (CI [[Formula: see text]], [Formula: see text]) in the BDI scale, of [Formula: see text] points (CI [[Formula: see text]], [Formula: see text]) in the BDI-II scale and of [Formula: see text] points (CI [[Formula: see text]], [Formula: see text]) in the PHQ-9 scale, when evaluating depressive symptoms. In the case of the migraine-related symptoms, we found mean reductions of [Formula: see text] (CI [[Formula: see text]], [Formula: see text]) points in the HIT6 scale, [Formula: see text] (CI [[Formula: see text]], [Formula: see text]) in the MIDAS scale, [Formula: see text] (CI [[Formula: see text]], [Formula: see text]) points in the VAS scale and of [Formula: see text] (CI [[Formula: see text]], [Formula: see text]) migraine episodes per month. Comorbid patients showed slightly better improvements in BDI, HIT6 scores and migraine frequency compared to monomorbid patients. The latter group manifested better results in MIDAS and VAS scores.Conclusion: Treatment with onabotulinumtoxinA leads to a significant reduction of disease severity of both chronic migraine and major depressive disorder in patients comorbid with both diseases. Comparative analyses suggest an equivalent strong effect in monomorbid and comorbid patients, with beneficial effects specifically seen for certain migraine features. [ABSTRACT FROM AUTHOR]

• We investigated the interposition of a stem taper adapter in terms of tribological interactions. • Investigations on wear, roughness, and corrosion on explants were conducted. • A higher incidence of second revisions on femoral head was noticed in absence of an adapter. • The surface analysis shows no predominant roughness values along any of the stem directions. • A homogeneous worsening or corrosion of the stem taper along the circumference was noticed. As revision surgeries of total hip arthroplasty are going to increase, success or failure of revised implants is a fundamental aspect in the orthopaedic field. Today, slight is known about the success rate of revised total hip arthroplasty when the femoral head is substituted on a retained stem. We wanted to investigate if the interposition of a stem taper adapter between the paired elements can influence this rate of success. From a total of more than 1000 revised implants, recorded during their follow up in a regional registry, the study was limited to the ones subjected to a surgical revision, where the head has been revised but the stem taper has not. Investigations on wear, roughness, and corrosion on the available explants were conducted, with the aim of providing visual and empirical response on the topic and to furnish to other researches useful data for comparison. Our results highlighted a higher incidence of second revisions when the femoral head is substituted without using an adapter. The topographic analysis refers that it is not evident a predominant roughness along any of the stems directions: no evidences were found that would define a recurrent rougher direction. This indicates a homogeneous worsening or corrosion of the stem taper along the circumference. Further, we found that the roughness values of the specimens analyzed not influence their surfaces and there is no a direct relation between the roughness of the bore heads and the stem tapers. [ABSTRACT FROM AUTHOR]

Background and purpose — Little is known about the role of retained trunnions in revision hip arthroplasties, i.e., when only the femoral head is substituted. Wear (fretting corrosion) and ceramic head fractures are 2 poorly understood concerns related to use, and the role of adapter sleeves has not been defined. In this registry study we assessed the influence of sleeve interposition on re-revision rates in revision hip arthroplasties with retained stems. Confounding factors (demographics, implant-related features) and failures were also analyzed. Patients and methods — We conducted a registry study on 1,127 revised implants (retained trunnion and head exchange). In 26% of implants an adapter sleeve was interposed; in 74% no adapter sleeve was implanted. Demographic and implant-related features were investigated including a descriptive analysis of failures. Results — The mean follow-up of revised implants with and without the use of an adapter sleeve was 3.3 and 5.1 years, respectively. The implant survival without an adapter sleeve was significantly higher, 98.4% (95% CI 96.9–99.8) vs. 95.2% (CI 93.2–96.6) with an adapter sleeve at 5 years. No re-revisions due to adverse local tissue reactions or ceramic head fractures were reported. In order to overcome the different distribution of head materials and head sizes in the two cohorts, only Delta balls were investigated. Interpretation — Adapter sleeve interposition had a minor influence on the revision rates. No adverse local tissue reactions or head fractures occurred. [ABSTRACT FROM AUTHOR]

Purpose: The effect of being obese on the long-term survival of total joint arthroplasty is persistently discussed. Considering only studies with large cohort of patients and meta-analysis, a high body mass index has been correlated with a higher incidence of complication but not univocally with a lower survival rate. In this study, we analyzed, retrospectively, the data of patients that received unicompartmental knee prostheses in order to examine if obesity has an effect on clinical outcomes.Methods: A retrospective multi-centre study was carried out on 4964 unicompartmental knee replacements between July 2000 and December 2016, the patients involved were 3976, with 988 bilateral cases. The patients were categorized into three groups: non-obese with a body mass index (BMI) < 30 kg/m2, obese with BMI ranged between 30 and 39 kg/m2, and morbidly obese (BMI ≥ 40 kg/m2). The outcome was measured using the Cox proportional hazards model with end point UKA revision for any reasons. Results were stratified for sex, age, weight, and bi-laterality.Results: The morbidly obese group was significantly younger and required a significantly longer operating time. No statistical significant differences were observed considering the BMI groups in terms of type of insert, type of tibial component, prosthetic condyle, and prosthesis fixation (p > 0.05; chi-square test).Conclusions: Obese and morbidly obese patients have as much to gain from total knee replacement as non-obese patients. [ABSTRACT FROM AUTHOR]

• Tribological behavior of total knee prostheses explants was investigated. • Roughness of femoral components with identical design was analyzed. • Lateral condyles show more surface damage than the medial ones according to load conditions. • At a macroscopic level the surfaces appears more damaged in high body mass index prostheses. • Statistical tests outline a significant difference in roughness for different implants sizes. Total replacement of the knee joint is a well-established surgical procedure performed to relieve pain and to restore the functionality of a compromised knee. Nevertheless, wear is still one of the main issues affecting joint prostheses, causing loosening and, eventually, implants failure. Surface roughness of the implant has been found to influence the mechanisms for premature wear, having relevant influence on the tribological performance. Joint load distribution have provided valuable insight into the knee loading patterns, showing that joint contact loads differ in medial and lateral condyles. We wondered if it is possible to find any alteration between surface roughness of medial and lateral sides and if the body mass index is in any way related to the in vivo roughening of the elements. For this purpose, 11 explants of total knee replacement (mean follow up of 3.2 years), with identical design, were analysed acquiring the roughness on the femoral components. Macroscopic inspections show that lateral condyles underwent more surface damage than the medial ones. However, surface roughness was not significantly different comparing medial and lateral sides. Statistical tests outlined a significant difference in surface roughness when distinct sizes of implants, namely 3 and 4, are considered. [ABSTRACT FROM AUTHOR]

Given the long-term problem of polyethylene wear, medical interest in the new improved cross-linked polyethylene (XLPE), with or without the adding of vitamin E, has risen. The main aim of this study is to gain further insights into the mutual effects of radiation cross-linking and addition of vitamin E on the wear performance of ultra-high-molecular-weight polyethylene (UHMWPE). We tested four different batches of polyethylene (namely, a standard one, a vitamin E-stabilized, and two cross-linked) in a hip joint simulator for five million cycles where bovine calf serum was used as lubricant. The acetabular cups were then analyzed using a confocal profilometer to characterize the surface topography. Moreover; the cups were analyzed by using Fourier Transformed Infrared Spectroscopy and Differential Scanning Calorimetry in order to assess the chemical characteristics of the pristine materials. Comparing the different cups' configuration, mass loss was found to be higher for standard polyethylene than for the other combinations. Mass loss negatively correlated to the cross-link density of the polyethylenes. None of the tested formulations showed evidence of oxidative degradation. We found no correlation between roughness parameters and wear. Furthermore, we found significantly differences in the wear behavior of all the acetabular cups. XLPEs exhibited lower weight loss, which has potential for reduced wear and decreased osteolysis. However, surface topography revealed smoother surfaces of the standard and vitamin E stabilized polyethylene than on the cross-linked samples. This observation suggests incipient crack generations on the rough and scratched surfaces of the cross-linked polyethylene liners. [ABSTRACT FROM AUTHOR]

A clear discrepancy between predicted in vitro and actual in vivo surface phase stability of BIOLOX®delta zirconia-toughened alumina (ZTA) femoral heads has been demonstrated by several independent research groups. Data from retrievals challenge the validity of the standard method currently utilized in evaluating surface stability and raise a series of important questions: (1) Why do in vitro hydrothermal aging treatments conspicuously fail to model actual results from the in vivo environment? (2) What is the preponderant microscopic phenomenon triggering the accelerated transformation in vivo? (3) Ultimately, what revisions of the current in vitro standard are needed in order to obtain consistent predictions of ZTA transformation kinetics in vivo? Reported in this paper is a new in toto method for visualizing the surface stability of femoral heads. It is based on CAD-assisted Raman spectroscopy to quantitatively assess the phase transformation observed in ZTA retrievals. Using a series of independent analytical probes, an evaluation of the microscopic mechanisms responsible for the polymorphic transformation is also provided. An outline is given of the possible ways in which the current hydrothermal simulation standard for artificial joints can be improved in an attempt to reduce the gap between in vitro simulation and reality. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine total knee polyethylene inserts from in vitro simulation to evaluate and display--using a 3D optical scanner--wear patterns and wear rates of inserts exposed to wear by means of simulators. Various sets of tibial inserts have been reconstructed by using optical scanners. With this in mind, the wear behavior of fixed and mobile bearing polyethylene knee configurations was investigated using a knee wear joint simulator. After the completion of the wear test, the polyethylene menisci were analyzed by an innovative 3D optical scanners in order to evaluate the 3D wear distribution on the prosthesis surface. This study implemented a new procedure for evaluating polyethylene bearings of joint prostheses obtained after in vitro wear tests and the proposed new approach allowed quantification of the contact zone on the geometry of total knee prostheses. The results of the present study showed that mobile TKPs (total knee prosthesis) have lower wear resistance with respect to fixed TKPs. [ABSTRACT FROM AUTHOR]

Background Currently, little is known about the effects that metal transfer affecting hip implants may have on roughness. The main aim of this study is to propose a metrological technique in order to better characterize this phenomenon on the surface of composite ceramic femoral heads, discussing its influence on the biotribological behaviour of the coupling. In addition, through the acquired data, we investigate whether the metal transfer extension and roughness alterations on a femoral head is correlated to the material, the follow-up of the implant and whether metal transfer is associated with changes in the roughness of alumina surface, considering different follow-ups . Methods Three generations of femoral heads manufactured in ceramic (Biolox ® , Biolox ® Forte, and Biolox ® Delta) were retrieved from patients after different implantation periods (mean follow up = 6.9 years) and they were analysed using a roughness tester and an optical non-contact 3D scanner, in order to characterize the metal transfer on the bearing surface. Results Surface area where the metal transfer was observed ranged between 29.6 mm 2 and 573.6 mm 2 . The mean values of Sa (average roughness) were different between the Affected Zone (0.3 ± 0.1 μm) and Unaffected Zone (0.03 ± 0.1 μm). In particular, regions of metal transfer were rougher than the non-metal transfer regions of the articular surface and this is demonstrated by both the areal roughness parameters considered: Sa (arithmetic mean height) and St (maximum height of the surface) parameters (p = 0.002, Wilcoxon paired-test). St parameter acquired on the Biolox ® Delta femoral heads showed the lowest mean value (11.92 μm). Conclusion We found no correlation between follow-up vs . roughness and total surface area of metal transfer. Furthermore, we found that the amount of areal coverage of metal transfer is correlated with the surface roughness. Finally, MT effect on composite ceramic implants caused lower height of peaks and valleys when compared to common ceramic. [ABSTRACT FROM AUTHOR]

Wear is currently quantified as mass loss of the bearing materials measured using gravimetric methods. However, this method does not provide other information, such as volumetric loss or surface deviation. In this work, we validated a technique to quantify polyethylene wear in three different batches of ultrahigh-molecular-polyethylene acetabular cups used for hip implants using nondestructive microcomputed tomography. Three different configurations of polyethylene acetabular cups, previously tested under the ISO 14242 parameters, were tested on a hip simulator for an additional 2 million cycles using a modified ISO 14242 load waveform. In this context, a new approach was proposed in order to simulate, on a hip joint simulator, high-demand activities. In addition, the effects of these activities were analyzed in terms of wear and deformations of those polyethylenes by means of gravimetric method and micro X-ray computed tomography. In particular, while the gravimetric method was used for weight loss assessment, microcomputed tomography allowed for acquisition of additional quantitative information about the evolution of local wear and deformation through three-dimensional surface deviation maps for the entire cups' surface. Experimental results showed that the wear and deformation behavior of these materials change according to different mechanical simulations. [ABSTRACT FROM AUTHOR]

The purpose of this work is to establish a protocol, which combines CAD modeling to non-destructive microscopic techniques of confocal Raman micro-spectroscopy and laser microscopy, to assess the in-vivo hydrothermal stability of ZTA femoral head retrievals. The combined effects of wear, biological environment, and in vivo occurring peculiar events as metal staining were evaluated on five retrieved ZTA femoral heads with implantation time ranging from 9 to 106 months. The protocol relies on the application of a polar grid on the entire surface of the head, which divides it into small sectors; each sector is then automatically screened with micrometer resolution. Maps are finally linked to each other and an in-toto view of the retrieved head becomes available in three dimensions. Upon combining analytical techniques with a solid modeling computer-aided design (CAD) software, it becomes possible to develop a 3D model of the femoral head, which comprehensively describes topographic, crystallographic, and micromechanical characteristics of the entire surface and immediate sub-surface. The combination of CAD, polarized Raman spectroscopy, and laser microscopy has led to in-toto screening of femoral head with micrometer-scale resolution, thus providing a new and comprehensive protocol for both quality assessments on new components and failure analysis on retrievals. [ABSTRACT FROM AUTHOR]

More than 60.000 hip arthroplasty are performed every year in Italy. Although Ultra-High-Molecular-Weight-Polyethylene remains the most used material as acetabular cup, wear of this material induces over time in vivo a foreign-body response and consequently osteolysis, pain, and the need of implant revision. Furthermore, oxidative wear of the polyethylene provoke several and severe failures. To solve these problems, highly cross-linked polyethylene and Vitamin-E-stabilized polyethylene were introduced in the last years. In in vitro experiments, various efforts have been made to compare the wear behavior of standard PE and vitamin-E infused liners. In this study we compared the in vitro wear behavior of two different configurations of cross-linked polyethylene (with and without the add of Vitamin E) vs. the standard polyethylene acetabular cups. The aim of the present study was to validate a micro X-ray computed tomography technique to assess the wear of different commercially available, polyethylene’s acetabular cups after wear simulation; in particular, the gravimetric method was used to provide reference wear values. The agreement between the two methods is documented in this paper. [ABSTRACT FROM AUTHOR]

Introduction: Since 1979 the number of patients treated with femoral stems has continued to grow, as well as the number of stems with features similar to the Zweymüller prosthesis produced by different companies. Identification can be problematic in case requiring revision. In the present paper, we present an overview of morphometric differences between the different stem designs, which can be useful for radiologic identification in revision cases.Methods: By doing some research on the Internet of specialized sites and worldwide literature, we searched for all femoral stems agreeing with Zweymüller principles (cementless, straight, tapered, rectangular cross-sectioned femoral stems).Results: We found 26 different stems from different companies producing or having produced in the past the Zweymüller-type femoral stems for hip prosthesis.Discussion: Accurate preoperative identification of the Zweymüller femoral stem type may be of critical importance to eventual outcomes following revision surgery. Each manufacturer has different instruments specific to the removal of their primary implants, and ensuring they are available can simplify the revision procedure significantly. Exact pre-operative planning is also necessary for selecting the correct ball head in cases where a stem is well-fixed and can be left in situ. The commonly used notation "Eurocone 12/14" provides no information about the actual taper angle. Whenever the stem is left in situ, the exact specifications of the taper must therefore be obtained from the manufacturer in order to use a metal sleeve that precisely fits it and the ball head. Failure to do so may result in severe complications, such as metallosis. In cases where it is not possible to identify the taper angle, the surgeon may even consider removal of the stem, though this significantly increases the surgical procedure's invasiveness. Only a single, uniform standard taper, such as that offered until 1994 by CeramTec, can solve these issues in the future.Conclusion: The survival rate of the Zweymüller stems after ten years was 96 % and the complication rate was very low. Pre-operative identification of the femoral implant is of considerable importance for planning and correctly implementing revision procedures. [ABSTRACT FROM AUTHOR]

Although metal transfer (MTR) has been observed in total hip replacement, little is known about its effects on the wear phenomena of bearing surface materials. This study was aimed at investigating the effects of MTR on the bearing surface of zirconia and Biolox ® Delta ceramic femoral heads, to identify prevalent surface patterns and morphologies as well as to evaluate possible phase changes upon MTR, assessing the monoclinic zirconia content and quantifying the tetragonal → monoclinic zirconia transformation. Selected Biolox ® Delta and zirconia femoral heads retrieved from patients after different implantation periods were analysed using a contact profilometer and micro-Raman spectroscopy. The roughness data showed that MTR significantly changed the contact surface of the coupling in the same manner for zirconia and Biolox ® Delta. The micro-Raman analyses showed that in the border control areas, the Biolox ® Delta retrievals were characterised by significantly higher monoclinic contents values compared to zirconia retrievals. Upon wear, zirconia femoral heads underwent a higher increase in the monoclinic content than Biolox ® Delta. The stress related to MTR appeared a particularly severe condition able to induce the phase transformation. In zirconia retrievals, the tetragonal→monoclinic transformation involved a thinner depth of material compared to Biolox ® Delta. [ABSTRACT FROM AUTHOR]

The problems associated with prosthetic failure and revision surgery still constitute the main clinical problem of prosthetic surgery. The objective of wear evaluation is to determine the wear rate and its dependence on the test conditions. To obtain realistic results, a wear test can be performed to reproduce in vivo working conditions and compare the wear characteristics of various total knee prostheses designs. At the state of the art, two simulation concepts are available and defined in ISO 14243 standards series. In both these guidelines, level walking is the sole activity of daily living that is represented for testing. With so many variables and so many sources of error and the sensitivity of the output to these errors, can the motion determined in the simulator be representative of the in vivo motion? This article goes beyond the current status of these knee simulations comparing literature results. [ABSTRACT FROM AUTHOR]

Wear of total hip prosthesis is a significant clinical problem that nowadays involves a growing number of patients. To acquire further knowledge on the tribological phenomena that involve hip prosthesis, wear tests are conducted on new biomaterials to increase materials life in orthopaedic implants. Advances in biomaterials for biomedical purposes have enhanced in the last years evolving in new improved ceramic and polymeric materials producing the so-called composite materials. This paper aims to review the evolution and the current state of the art of the ceramics composites and polymers commonly used in orthopaedic field as hip joint implants. This is specified through a schematic overview by describing, in particular, the evolution of various composites materials. The authors propose commentary on the evolution and current use of biomaterials for orthopaedic application on the evolution and actually used biomaterials for orthopaedic applications. [ABSTRACT FROM AUTHOR]

At the beginning of the 21st century, several scientific studies drew attention to the unsustainability of the massive use of fossil fuels as the main global source of energy and this led to international public organisations starting numerous projects aimed at containing the resulting greenhouse gas emissions. In this context, Automated People Movers can play an important role, as they are fully automated transport systems operating on a fixed track, along which the vehicles can be pulled by one or more steel wire ropes. This feature makes it possible to manufacture lighter and less energy consuming vehicles because of the on-board absence of propulsion, transmission and energy accumulation elements, with a consequent lightening of the structural parts. The use of electric energy to power these transport systems makes it possible to take advantage of energy sources that are not necessarily black-oil dependent. The energy aspect has been analysed using an original simulation model, developed with MATLAB®, in which several variables, including the vehicle load factor, have been considered. The results, expressed in terms of gep/(pass-km)w, have been compared with the specific energy consumption of alternative urban transit systems, according to the most recent technical literature. [ABSTRACT FROM AUTHOR]

All-trans-retinoic acid (ATRA) is a natural compound proposed for the treatment/chemoprevention of breast cancer. Increasing evidence indicates that aberrant regulation of epithelial-to-mesenchymal transition (EMT) is a determinant of the cancer cell invasive and metastatic behavior. The effects of ATRA on EMT are largely unknown. In HER2-positive SKBR3 and UACC812 cells, showing co-amplification of the ERBB2 and RARA genes, ATRA activates a RARα-dependent epithelial differentiation program. In SKBR3 cells, this causes the formation/reorganization of adherens and tight junctions. Epithelial differentiation and augmented cell-cell contacts underlie the anti-migratory action exerted by the retinoid in cells exposed to the EMT-inducing factors EGF and heregulin-β1. Down-regulation of NOTCH1, an emerging EMT modulator, is involved in the inhibition of motility by ATRA. Indeed, the retinoid blocks NOTCH1 up-regulation by EGF and/or heregulin-β1. Pharmacological inhibition of γ-secretase and NOTCH1 processing also abrogates SKBR3 cell migration. Stimulation of TGFβ contributes to the anti-migratory effect of ATRA. The retinoid switches TGFβ from an EMT-inducing and pro-migratory determinant to an anti-migratory mediator. Inhibition of the NOTCH1 pathway not only plays a role in the anti-migratory action of ATRA; it is relevant also for the anti-proliferative activity of the retinoid in HCC1599 breast cancer cells, which are addicted to NOTCH1 for growth/viability. This effect is enhanced by the combination of ATRA and the γ-secretase inhibitor N-(N-(3,5-difluorophenacetyl)-L-alanyl)-S-phenylglycine t-butyl ester, supporting the concept that the two compounds act at the transcriptional and post-translational levels along the NOTCH1 pathway. [ABSTRACT FROM AUTHOR]

Objective: The main goal of this case was to report the treatment of bicondylar fractures of the tibial plateau and the restoration of the metaphyseo-diaphyseal dissociation.Clinical Presentation and Intervention: A 54-year-old male who was cycling had a road accident that caused a closed fracture of the right tibial plateau and proximal fibula diagnosed by X-rays. The patient underwent surgery and was immobilized with a long-leg splint for 4 weeks. After immobilization, aggressive rehabilitation was done. Progressive quadriceps strengthening, movements to improve symmetrical weight bearing, and functional activities were performed. The patient improved muscle strength and obtained high scores for gait and balance in a relatively short time.Conclusion: In this report, a bicondylar tibial fracture treated with a two-incision approach and a double-plate osteosynthesis provided strong fracture stabilization and thereby allowed an early mobilization with aggressive rehabilitation. [ABSTRACT FROM AUTHOR]

Abstract: Small and large sized-mobile inserts (i.e. size #2 and size #6) were tested on a knee wear simulator for 2 million cycles, using bovine calf serum as lubricant. Gravimetric and micro-Raman spectroscopic analyses were performed on polyethylene inserts. Roughness analysis was performed on the metallic components. The larger size, i.e. #6, had almost twice weight loss with respect to the smaller one, i.e. #2 (37.8±2.8mg and 19.46±0.93mg, respectively). Significant statistical differences were observed in wear rates (p=0.001, Kolmogorov–Smirnov test for two samples). Raman spectroscopy showed a greater increase in crystallinity for the smaller inserts: upon wear, the orthorhombic content (α o) significantly increased at the expense of the third phase content (α b). [Copyright &y& Elsevier]

Experimental wear testing is an essential step in the evaluation of unicompartmental knee prostheses; the major mechanisms that dominate the wear of conventional ultra high molecular weight polyethylene tibial knee menisci are the sub-surface cracking and delamination that induce particle release by abrasion/adhesion and subsequently periprosthetic osteolysis. The aim of this study was to determine whether plastic deformation affects the wear of the polymer and to measure the magnitude of these effects. Wear test was performed using a displacement-control knee wear simulator with 'three-plus-one' stations, in accordance with the ISO 14243-3/2. A state-of-the-art coordinate measuring machine was used to quantify the volumetric mass loss of the mobile knee polyethylene menisci as well as creep/plastic deformations. The volumetric wear measured by this method was compared to that measured by the gravimetric method. Raman spectroscopy showed morphology changes induced by mechanical stress in both the upper and lower surfaces of the menisci. The amorphous content increased at expenses of the crystalline orthorhombic content, which generally decreased in all menisci. A slight orthorhombic → monoclinic phase transformation occurred upon mechanical stress. Plastic deformation appeared as the main factor affecting the trend of the spectroscopic markers and thus the morphology degradation. [ABSTRACT FROM AUTHOR]

Abstract: This work discusses the wear behaviour of two different ultra-high-molecular-weight-polyethylene tibial component designs. Mobile and fixed bearings were tested on a knee wear simulator for 5 million cycles using bovine calf serum as lubricant. We correlated the wear results with the chemical characterisation of the investigated materials: Fourier Transformed Infra Red Spectroscopy analyses, Differential Scanning Calorimetry and cross-link density measurements were used to assess the chemical features of this polyethylene. Mobile and fixed polyethylene inserts showed a different wear behaviour: the mobile designs components showed lower weight losses than the fixed components (109±6mg and 163±80mg, respectively). Significant statistical differences were observed in wear rate (P =0.035, Kolmogorov–Smirnov Test for two samples). From a molecular point of view, typical radiation-induced oxidation profiles were observed in all the tested polyethylene samples, but the overall degradation was more significant in the fixed bearing inserts and this is likely to play a role on the wear performances. [Copyright &y& Elsevier]

Total hip arthroplasty has yielded excellent results in decreasing pain and enhancing function in patients with hip degenerative disease. However, the problems associated with prosthetic failure and the consequent need for revision surgery still represent a major clinical issue. The most common reasons for revision surgery include implant loosening, periprosthetic osteolysis, infection, malalignment, stiffness, implant failure or fracture, and wear. The need for eliminating or reducing wear plays a crucial role in refining prosthesis composition and design. In this regard, it is important to develop new techniques for more accurate and reproducible measurement of wear. This should allow earlier detection of increased wear and thus permit earlier identification of patients who are at risk, and also help to identify faulty implant designs. This work is aimed at discussing the most common in vivo and in vitro methods used for evaluating the wear of hip prosthesis components. [ABSTRACT FROM AUTHOR]

Abstract: The complications associated with prosthetic failure and revision surgery still constitute the main clinical problem. The objective of wear evaluation is to determine the wear rate and its dependence on the test conditions. To obtain realistic results, a wear test can be performed to reproduce in vivo working conditions and compare the wear characteristics of various total knee prostheses designs. Two knee wear simulators with different input control mechanisms, displacement and force controlled, were used to assess the wear behavior of ultra-high molecular weight polyethylene uni-condylar knee prostheses. The differences in wear behavior were assessed using a state-of-art coordinate measuring machine; Raman spectroscopy was used to evaluate the possible crystallinity changes on the uni-condylar menisci induced by mechanical stress. These results were compared with available uni-condylar retrievals. Scratches were visible along the anterior-posterior direction emphasizing that the motion was constant during the movements under the displacement control simulation. On the contrary, different kinematics schemes were observed under the force controlled simulation. The structural Raman markers showed a good correlation with the coordinate measuring machine data, and in particular with the depth of the concavity formed upon in vitro testing or in vivo service. With regards to the in vitro tested components, the specimens tested under force controlled simulator, which underwent a higher volumetric loss, showed a higher increase of the amorphous content. At a molecular level, the wear mechanism did not appear significantly different for the three sets of specimens, with the exception of the amorphous content which, upon wear, increased in the in vitro tested components, while decreased in the retrievals. [Copyright &y& Elsevier]

Abstract: Six retrieved alumina hip implants were investigated for severe damage after a mean follow-up of 13 years (range: 8–21 years) using a multivariable approach: a coordinate measuring machine was used to quantify volumetric wear, the surface was characterized by scanning electron microscopy, and fluorescence and Raman spectroscopy were used to investigate the phenomenon on a micrometer crystal scale. All the femoral heads exhibited significant loss of roundness with heavy deviation from the original sphericity, showing an average volumetric wear of 602±3mm3. A smooth surface with occasional pits and agglomerates was observed; formation of craters and loss of surface integrity was revealed. The femoral heads characterized by the highest volumetric wear underwent the most significant stress on a micrometer crystal scale (i.e. the most pronounced changes in the width of the fluorescence and Raman bands). [Copyright &y& Elsevier]

Abstract: Background: Modern unicompartmental knee prostheses represent a valid alternative to total knee replacement. It is known that variations in clinical alignment lead to altered biomechanics and abnormal wear. The aim of this study was to assess the influence, on wear behaviour, of two different cementing interfaces of the femoral components tested on a knee joint wear simulator. Methods: The wear tests were run in a knee wear simulator at a frequency of 1.1Hz for 3million cycles in accordance with ISO 14243-3. Twelve commercial mobile GUR 1020 UHMWPE meniscus specimens articulated in between 12 cobalt–chromium–molybdenum alloy femoral and tibial components covered by a multi-layer of chromium nitride and a final layer of zirconium nitride ceramic coating to prevent ion release from the substrate. Two wear tests were performed: in the first test, each femoral component was cemented into a custom made metallic-block shaped to perfectly host it. In the second test, synthetic composite femurs received the femoral components on the basis of guidelines used in current surgery. Findings: The two cementing interfaces showed a significantly different wear behaviour, quantified as mean weight loss (P <0.001). Scanning electron microscope examinations of new and tested metallic components showed macro- and micro-pores of few microns on both configurations. Interpretation: The wear pattern observed at 3million cycles showed differences between the two methods of fixation for the meniscus femoral components. [Copyright &y& Elsevier]

The success of a total knee replacement (TKR) strongly depends on the prosthetic design; this includes on one hand the best choice of the bearing materials to minimize wear, on the other hand a good orientation of the prosthetic components with respect to the loading directions. The aim of this study was to investigate the feasibility of a new experimental setup combining two fundamental aspects for the long-term success of knee implants: wear and micromotions. A novel procedure was used to simulate working conditions as close as possible to in vivo ones and to measure implant-bone micromotion, by means of fixing the femoral component of the prosthesis to the distal part of a synthetic femur to be tested through a knee simulator. Gravimetric wear of the tibial specimens was assessed at regular intervals. Implant-bone inducible micromotions and permanent migrations were measured at three locations throughout the test. Wear patterns on tibial specimens were characterized through a standardized protocol based on digital image analysis; fatigue damage in the cement was quantified. Some initial conditioning was noticed both in the wear process and microcracking distribution within the cement mantle. Similarity in wear tracks observed on tibial inserts and other retrieval studies, coupled with clinically consistent migration patterns for TKR, supports the efficacy of the new in vitro method presented. [ABSTRACT FROM AUTHOR]

Ceramic-on-ceramic and metal-on-metal bearing surfaces are often employed for total hip replacement because of their resistance to wear. However, they have some limits: brittleness is a major concern for ceramic, and ion release is a drawback for metal. To reduce the effect of these limitations, a hybrid coupling of ceramic-on-metal has been proposed. The theoretical advantage of this new coupling might lead orthopedic surgeons to use it indiscriminately. We asked whether the wear rate of this innovative solution was comparable with that of ceramic-on-ceramic, which is considered to be the gold standard for wear resistance. In a hip simulator study, we tested the wear pattern of a hybrid ceramic-on-metal coupling supplied by the same distributor; in particular, three different configurations were tested for 5 million cycles: 36-mm ceramic-on-ceramic, 32-mm and 36-mm ceramic-on-metal. These combinations were gravimetrically and geometrically evaluated. After 5 million cycles, the volumetric loss for the metal acetabular cups (Φ 36-mm) was 20-fold greater than that of the ceramic cups of the same size (Φ 36-mm); a volumetric loss of 4.35 mm3 and 0.26 mm3 was observed, respectively, for ceramic-on-metal and ceramic-on-ceramic combinations. Significant statistical differences were observed between all 36-mm different combinations ( P < 0.0001). The increased diameter of the 36-mm ceramic-on-metal configuration resulted in a lower volumetric loss compared with that of the 32-mm ceramic-on-metal configuration. Our findings showed an increase in wear for the proposed hybrid specimens with respect to that of the ceramic-on-ceramic ones. This confirms that even in the case of ceramic-on-metal bearings, mixing and matching could not prove effective wear behavior, not even comparable with that of the ceramic-on-ceramic gold standard. [ABSTRACT FROM AUTHOR]

Abstract: The removal of pathologically generated free radicals produced during ischemia, reperfusion and intracranical hemorrhage seems to be a viable approach to neuroprotection. However, at present, no neuroprotective agent has proven effective in focal ischemic stroke phase III trials, despite the encouraging data in animal models. This study aimed to explore the effect of the brain penetrant low molecular weight radical scavenger bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)-decandioate (IAC) in neurological damage subsequent to ischemia–reperfusion injury in Mongolian gerbils. We examined the intraperitoneal effects of IAC on temporary bilateral common carotid artery occlusion (BCCO) by means of morphological and histological analysis of the hippocampus. Significant dose-dependent protective effects of IAC (1 to 10mg/kg b.w.) against neuropathological and morphological brain changes were seen when administered i.p. 1h before temporary BCCO in Mongolian gerbils. When administered up to 6h after BCCO, IAC actually reverses the neurodegenerative processes (e.g. hippocampal cell viability) induced by ischemia in a dose-dependent fashion. Data show that IAC is highly effective in protecting and preventing oxidative brain damage associated with cerebral flow disturbances. It is also effective even in late treatment of the insult, emphasizing its potential role for the management of ischemic stroke patients. [Copyright &y& Elsevier]

Abstract: New cross-linked polyethylene acetabular cups, obtained by thermo-compression process, were compared with conventional and traditional commercially available cross-linked polyethylene in terms of wear behaviour in a hip simulator for 10 million cycles using bovine calf serum as lubricant. Gravimetric measurements revealed significant differences between the wear behaviours of the five sets of acetabular cups. In particular, this new type of thermo-compression cross-linked wore more than the traditional cross-linked polyethylene but exhibited a wear rate about four times lower than conventional ultra-high-molecular-weight-polyethylene. The FTIR analyses indicate that oxidation to various extents appears as a consequence of γ-irradiation in presence of oxygen. [Copyright &y& Elsevier]

Abstract: The clinical success of second-generation metal-on-metal hip replacement and the good tribological performance of alumina ceramic revived an interest in hip articulation as a solution to reduce wear. This study was aimed at characterizing the wear behaviour of new hybrid ceramic-on-metal bearings. In particular, this study investigated the wear behaviour of ceramic-on-metal hip components (three different diameters configurations: 28, 32 and 36mm), not specifically proposed to be coupled, in order to compare them with ceramic-on-ceramic, which is considered to be the gold standard for wear resistance. For this purpose, the weight loss over a standard wear simulation was monitored. Moreover, scanning electronic microscope observations were used to verify if any carbides removal, for the metallic components, triggered wears debris production promoting abrasive third-body wear. After five million cycles, our results showed significantly greater wear-in ceramic-on-metal compared with ceramic-on-ceramic, and significant greater wear for the 32-mm diameter compared with the 36-mm one. Our findings showed an increase in wear for the proposed hybrid specimens with respect to that of the ceramic-on-ceramic ones confirming that even in the case of ceramic-on-metal bearings, mixing and matching could not prove effective wear behaviour, not even comparable with that of the ceramic-on-ceramic gold standard. Wear patterns and roundness tolerances certainly discourage the coupling of components not specifically intended to be coupled. Unsuitable geometrical conformity could, in fact, result in a poor dynamic behaviour and lead to clinical failure. [Copyright &y& Elsevier]

Abstract: Background: To minimise wear of the meniscal component in total ankle replacement, a three-component artificial joint has recently been developed. This new prosthesis has convex spherical tibial and anticlastic talar metal components with non-anatomic but ligament-compatible shapes in the sagittal plane, and a fully conforming ultra-high-molecular-weight-polyethylene meniscal component inserted in between. The in vitro wear of meniscal components can be assessed using a four-station joint simulator. The study was aimed at comparing wear patterns obtained in vitro with those observed in implant retrievals with the same design. Methods: The wear tests were run in a joint wear simulator at a frequency of 1.1Hz for two million cycles. Three bearings within corresponding metal components were subjected to flexion/extension (range 0–58°), anterior–posterior translation (0–5.2mm), internal–external rotation (−1.9° to +5.7°), and a maximum axial load of 2.6KN. These conditions were taken from the most recent findings in ankle joint mechanics. Three prostheses of the same type were harvested from patients due to replacement failures not associated with the device, 24, 24 and 9months, respectively, after implantation. The in vitro worn components and the three retrievals were analysed by using a scanning electron microscope, a Coordinate Measuring Machine, and micro-Raman spectroscopy. Findings: Visual and microscopic observations, analyses, and Raman crystallinity-based measurements showed similarity between the patterns generated experimentally in the wear simulator and those seen in retrievals with similar wear life. Interpretation: A joint wear simulator like the one used in this study, once configured properly, appears to be suitable to assess wear rates also in total ankle prostheses. [Copyright &y& Elsevier]

Abstract: Improved wear resistance in total knee replacement (TKR) is a suitable goal. Whereas the use of metal components is well established, mechanical loosening in recently introduced ceramic components are a cause of concern. The scope of this work was to test in vitro whether ceramic TKR femoral components are more prone to mechanical loosening than metal ones. Composite femurs were implanted with commercially available TKR metal components, and with ceramic components having identical shape to the metal ones. Implanted femurs were tested on a knee simulator for up to 5×10–6 cycles. Inducible micromotions and permanent migrations were recorded throughout the test. The cement layers were inspected for signs of damage or fracture. Micromotions and migrations were similar for metal and ceramic components: their magnitude and trend over time indicated that no implant was becoming loose. When there were statistically significant differences, the ceramic components were more stable than the metal ones. When the cement layers were inspected, a few short cracks were observed; most such cracks appeared during the first cycles, while no further damage occurred in the rest of the test. The type of damage found for both the metal and the ceramic components is compatible with well-fixed implants after long-term cycling. Altogether, no remarkable difference was found between the metal and ceramic components. Therefore, this study rejects the hypothesis that ceramic TKR femoral components are more prone to mechanical loosening. Although this study had a limited sample size, it provides novel pre-clinical indications about the potential of ceramic TKR femoral components. [Copyright &y& Elsevier]

Abstract: Interest in the rheology and effects of interacting surfaces is as ancient as man. This subject can be represented by a recently coined word: tribology. This term is derived from the Greek word “tribos” and means the “science of rubbing”. Friction, lubrication, and wear mechanism in the common English language means the precise field of interest of tribology. Wear of total hip prosthesis is a significant clinical problem that involves, nowadays, a too high a number of patients. In order to acquire further knowledge on the tribological phenomena that involve hip prosthesis wear tests are conducted on employed materials to extend lifetime of orthopaedic implants. The most basic type of test device is the material wear machine, however, a more advanced one may more accurately reproduce some of the in vivo conditions. Typically, these apparatus are called simulators, and, while there is no absolute definition of a joint simulator, its description as a mechanical rig used to test a joint replacement, under conditions approximating those occurring in the human body, is acceptable. Simulator tests, moreover, can be used to conduct accelerated protocols that replicate/simulate particularly extreme conditions, thus establishing the limits of performance for the material. Simulators vary in their level of sophistication and the international literature reveals many interpretations of the design of machines used for joint replacement testing. This paper aims to review the current state of the art of the hip joint simulators worldwide. This is specified through a schematic overview by describing, in particular, constructive solutions adopted to reproduce in vivo conditions. An exhaustive commentary on the evolution and actually existing simulation standards is proposed by the authors. The need of a shared protocol among research laboratories all over the world could lead to a consensus conference. [Copyright &y& Elsevier]

The wear of the ultra-high-molecular-weight polyethylene (UHMWPE) tibial insert was determined using a four-station knee simulator. The bearings were subjected to flexion/extension (between 0 and 58°), anterior–posterior translation (between 0 and −5.2 mm), internal–external rotation (between −1.9° and +5.7°), and a maximum axial load of 2.6 KN, as per ISO 14243−1,2,3. The wear tests were run at a frequency of 1.1 Hz for 5 million cycles, and the wear of the inserts ( n = 3) was determined using the gravimetric method. The novelty of the study was a special setup developed to simulate, as realistically as possible, in vivo conditions; this involved fixing the femoral component to the distal end of a synthetic femur model by a qualified orthopedic surgeon using an approved method. After 5 million cycles, the mean weight losses were 11.16, 19.74, and 12.61 mg for specimens #1, #2, and #3, respectively. Visual and nondestructive inspections for each of the test specimens showed similar wear tracks and these were very similar to those seen on inserts retrieved after 2 years in vivo. These results show the efficacy of the new in vitro UHMWPE wear assessment method. Furthermore, a comparison between the present in vitro results and those reported in a relevant previous study provide some insight into the influence of the method used to fix the femoral component to the simulator on the wear magnitude and patterns of the tibial insert. [ABSTRACT FROM AUTHOR]

Knee osteoarthritis is a complex clinical scenario where many biological and mechanical factors influence the severity of articular degenerative changes. Minimally invasive knee prosthetic surgery, with only a compartment replacement (unicompartmental knee replacement), might be a good compromise between osteotomy and total knee prosthesis. The focus of this study was to develop and validate a protocol to assess the fixation method of the femoral components in mechanical simulation, for pre-clinical validation; the wear behaviour of two different fixation frames was quantified and compared. In particular, two different wear tests were conducted using the same knee simulator, the same load profiles and the same kinematics; two different fixation methods were applied to the femoral sleds (synthetic femur and metal block). Surface characterization on both articulating bearings was performed by a roughness measuring machine and coordinate measuring machine. The wear produced by the tibial inserts using the synthetic femur was considerably higher than the wear registered by the metal-block holder. Roughness measurements on femoral sleds showed a limited number of scratches with high Rt values for the metal-block set-up; the damaged surface broadened in the case of femoral condyles and tibial inserts mounted on composite bone, but lower Rt and linear penetration values were measured. The two holding frames showed different wear activities as a consequence of dissimilar dynamic performance. Further observations should be made in vivo to prove the actual importance of synthetic bone simulations and specific material behaviour. [ABSTRACT FROM AUTHOR]

Abstract: In this study, five different types of conventional and cross-linked polyethylene (XLPE) (γ-sterilised PE GUR1020, EtO-sterilised PE GUR1020, γ-sterilised PE GUR1050, EtO-sterilised XLPE GUR1020, EtO-sterilised XLPE GUR1050) acetabular cups were tested on a hip joint simulator run for 5 million cycles in order to compare the relative long-term wear resistance in relation to material properties (PE grade, conventional or cross-linked) and sterilisation method (EtO treatment or γ-irradiation). Gravimetric measurements revealed significant differences between the wear behaviours of the five sets of acetabular cups. Weight loss was found to decrease along the series: γ-sterilised PE GUR1020>EtO-sterilised PE GUR1020>γ-sterilised PE GUR1050>EtO-sterilised XLPE GUR1050>EtO-sterilised XLPE GUR1020. The wear results were discussed in relation to the crystallinity degree of the cups which was determined by micro-Raman spectroscopy coupled to partial least-squares analysis. Within both conventional and cross-linked PE series, it appeared that higher crystallinity samples (i.e. γ-sterilised PE GUR1020 and EtO-sterilised XLPE GUR1050, respectively) were characterised by higher wear rates. The higher weight loss observed for PE GUR1020 was explained in relation to its lower molecular weight with respect to PE GUR1050. Raman analysis showed that wear testing did not significantly modify the crystallinity degree of any of the tested acetabular cups. The most worn cup, i.e. γ-sterilised PE GUR1020, appeared the most homogeneously polished upon wear testing, as confirmed by the lowest standard deviation associated to the crystallinity value recorded in the centre of the cup. The results of this investigation have clearly shown a dramatic wear reduction in favour of the cross-linked polyethylene. [Copyright &y& Elsevier]

We give an alternative and more informative proof that every incomplete $${\Sigma^{0}_{2}}$$ -enumeration degree is the meet of two incomparable $${\Sigma^{0}_{2}}$$ -degrees, which allows us to show the stronger result that for every incomplete $${\Sigma^{0}_{2}}$$ -enumeration degree a, there exist enumeration degrees x 1 and x 2 such that a, x 1, x 2 are incomparable, and for all b ≤ a, b = ( b ∨ x 1 ) ∧ ( b ∨ x 2 ). [ABSTRACT FROM AUTHOR]

Abstract: The present study was aimed at investigating the effects of the sterilization method and accelerated aging on the wear and morphology of ultrahigh molecular weight polyethylene. In a first test, gamma- and EtO-sterilized acetabular cups were tested in a hip joint simulator for two million cycles. After the test, the cups underwent an accelerated aging treatment (80°C, 4 weeks in air furnace) and were newly tested for another three million cycles. Wear was evaluated by gravimetric measurements, morphology by micro-Raman spectroscopy. During the first test, the EtO-sterilized cups underwent a significantly higher wear than the gamma-sterilized ones (62 and 30mg/million cycles, respectively). No significant crystallinity changes were observed. Upon accelerated aging, the crystallinity increase of the gamma-sterilized cups was more pronounced than for the EtO-sterilized cups, due to chain scission and oxygen incorporation. In the second test, the wear rate of EtO-sterilized cups decreased to 38mg/million cycles, while for gamma-irradiated cups it increased to 84mg/million cycles. At the same time, the latter cups underwent significant increases in temperature and crystallinity, due to the higher friction. For the EtO-sterilized cups a significant decrease in crystallinity was observed, due to the occurrence of an orthorhombic→monoclinic phase transformation. [Copyright &y& Elsevier]

Although polyethylene components have been used in the human joint for over 30 years, wear simulation studies are fundamental to assess wear resistance of total joint replacements. This assessment will help to obtain quality control and acquire further knowledge of the tribological processes that involve joint prostheses. As a result, the risk of implant failure of innovative prostheses will be reduced. The aim of the present study was to investigate the influence on wear of the polyethylene tibial inserts against metallic femoral components using a knee simulator following a standardized kinematics protocol (ISO/CD 14243-3.2). Four intact “small” size specimens of the tibial MP 913 were tested in a four-station knee wear simulator for two million cycles. The volumetric weight loss for the ultra-high-molecular-weight-polyethylene (UHMWPE) tibial inserts was 44 ± 2, 45 ± 3, and 47 ± 3 mg for the specimens #1–3, respectively. This study demonstrated a good repeatability among the stations of the knee simulator obtaining weight loss values congruent with those found by other authors using similar test conditions. [ABSTRACT FROM AUTHOR]

Abstract: Despite the fundamental value of wear simulation studies to assess wear resistance of total joint replacements, neither specialised simulators nor established external conditions are available for the human ankle joint. The aim of the present study was to verify the suitability of a knee wear simulator to assess wear rates in ankle prostheses, and to report preliminary this rate for a novel three-component total ankle replacement design. Four intact ‘small’ size specimens of the Box ankle were analysed in a four-station knee wear simulator. Special component-to-actuator holders were manufactured and starting spatial alignment of the three-components was sought. Consistent load and motion cycles representing conditions at the ankle joint replaced exactly with the prosthesis design under analysis were taken from a corresponding mechanical model of the stance phase of walking. The weight loss for the three specimens, after two million cycles, was 32.68, 14.78, and 62.28mg which correspond to a linear penetration of 0.018, 0.008, and 0.034mm per million-cycle, respectively for the specimens #1, #2, and #3. The knee wear simulator was able to reproduce load-motion patterns typical of a replaced ankle. Motion of the meniscal bearing in between the tibial and talar components was smooth, this component remaining in place and in complete congruence with the metal components throughout the test. [Copyright &y& Elsevier]

The need to improve the reliability of alumina and zirconia hip prostheses has led to the development of zirconia-toughened alumina (ZTA) ceramics. The set-up of new colloidal processing routes brought about new ZTA nanocomposites (NZTA) with a significantly smaller and narrower particle size distribution of zirconia than conventional powder mixing methods. These nanocomposites present reinforcement mechanisms other than transformation toughening, mainly based on residual thermal stresses. In this study, the wear behaviour of NZTA–NZTA couplings was evaluated in a hip joint simulator run for seven million cycles, in comparison with commercial and experimental alumina couplings. From a statistical point of view, the three sets of specimens did not show significant differences in wear behaviour. However, from a gravimetric point of view, the weight loss decreased along the series: experimental alumina > NZTA > commercial alumina. The R 1 and R 2 fluorescence bands (due to the Cr3+ ions naturally present in alumina ceramics as trace impurities) increased in intensity along the series: experimental alumina < NZTA < commercial alumina, indicating a progressive improvement of the surface quality. SEM analysis confirmed that the better the sample finishing, the better was the wear behaviour. By taking into account that the tested NZTA samples were prototypes (thus with a surface finishing worse than for a production type), it can be stated that NZTA can offer the option of improving the lifetime and reliability of ceramics. [ABSTRACT FROM AUTHOR]

Aseptic loosening due to wear and dislocation of the implant represents the main complication after total hip arthroplasty. To gain more insight into the influence of the implant position on wear, commercial alumina couplings have been tested in a hip joint simulator under three different angles of cup inclination (23°, 45°, 63°) with respect to a horizontal plane. The planned length of the test was ten million cycles. However, the test was stopped at 5.5 million cycles due to the fracture of one of the femoral heads, tested with at angle of 63°. The residual stress state in the worn acetabular cups and in the fractured femoral head were evaluated by the frequency shift and broadening of the R1 and R2 fluorescence bands due to the Cr3+ ions naturally present in alumina ceramics as trace impurities. The gravimetric measurements did not show significant differences among the three different inclinations tested, in agreement with previous simulator studies, but in disagreement with in vivo findings. The fluorescence measurements allowed to affirm that an angle of 63° represents a worsened mechanical condition for the prosthetic component, with a consequently higher probability of fracture and/or damage potentially conducive to massive wear. In the light of the fluorescence results, it did not appear surprising that the femoral head that fractured was the one being tested at 63°. [ABSTRACT FROM AUTHOR]

Abstract: The polyethylene (PE) for hip implants presents serious clinical problems; the production of debris may induce adverse tissue reactions that may lead to extensive bone loss around the implant and consequently osteolysis and implant loosening. Several attempts have been made to improve the wear properties of ultra-high molecular weight polyethylene (UHMWPE). More recently the attention of various researchers has been focused on cross-linked polyethylene (XLPE), due to its improved wear resistance with respect to conventional UHMWPE. This study was aimed at comparing the wear performances of clinically available acetabular liners (Zimmer Inc.) made of electron beam XLPE and conventional UHMWPE. To evaluate the influence of the material properties on wear, conventional UHMWPE and XLPE acetabular cups were tested against deliberately scratched CoCrMo femoral heads (Ra=0.12–0.14μm) in a hip joint wear simulator run for 3 million cycles with bovine calf serum as lubricant. Gravimetric measurements revealed significant differences between the wear behaviours of the two sets of acetabular cups: XLPE exhibited a wear rate about 40 times lower than conventional UHMWPE. Raman spectroscopy coupled to partial least-squares analysis was used to evaluate the possible crystallinity changes induced by mechanical stress (and thus the material wear resistance): only the UHMWPE cup which showed the highest weight loss displayed significant crystallinity changes. These results were correlated to the thickness of the plasticity-induced damage layer. The wear debris produced during the tests were isolated according to a validated protocol and imaged by scanning electron microscopy . The wear particles produced by XLPE were smaller than those produced by UHMWPE; the latter were observed as fibrillar and agglomerated particles. The mean equivalent circle diameter was 0.71 and 0.26μm for UHMWPE and XLPE, respectively. [Copyright &y& Elsevier]