Custom Loss Functions in XGBoost Algorithm for Enhanced Critical Error Mitigation in Drill-Wear Analysis of Melamine-Faced Chipboard.

The advancement of machine learning in industrial applications has necessitated the development of tailored solutions to address specific challenges, particularly in multi-class classification tasks. This study delves into the customization of loss functions within the eXtreme Gradient Boosting (XGBoost) algorithm, which is a critical step in enhancing the algorithm's performance for specific applications. Our research is motivated by the need for precision and efficiency in the industrial domain, where the implications of misclassification can be substantial. We focus on the drill-wear analysis of melamine-faced chipboard, a common material in furniture production, to demonstrate the impact of custom loss functions. The paper explores several variants of Weighted Softmax Loss Functions, including Edge Penalty and Adaptive Weighted Softmax Loss, to address the challenges of class imbalance and the heightened importance of accurately classifying edge classes. Our findings reveal that these custom loss functions significantly reduce critical errors in classification without compromising the overall accuracy of the model. This research not only contributes to the field of industrial machine learning by providing a nuanced approach to loss function customization but also underscores the importance of context-specific adaptations in machine learning algorithms. The results showcase the potential of tailored loss functions in balancing precision and efficiency, ensuring reliable and effective machine learning solutions in industrial settings.

Cup positioning and its effect on polyethylene wear of vitamin E- and non-vitamin E-supplemented liners in total hip arthroplasty: radiographic outcome at 5-year follow-up.

BACKGROUND: Aseptic loosening remains a challenging problem after total hip arthroplasty. Accurate cup placement and supplementation of antioxidants in acetabular liners might reduce material failure rates. The aim of this study is to assess the effect of the cup position on the wear behaviour of UHMWPE-XE and UHMWPE-X liners in vivo using virtual radiographs. METHODS: We conducted a prospective, randomized, controlled, multicenter trial. Clinical data of 372 probands were analyzed. Anteroposterior pelvic X-rays of 324 patients immediately postoperatively and after 1 and 5 years were evaluated by the RayMatch® analysis software regarding cup position and wear behaviour. RESULTS: Mean cup anteversion was 20.3° (± 7.4) and inclination was 41.9° (± 7.0) postoperatively. 62.3% of all patients had an anteversion and inclination within the Lewinnek safe zone. Anterior and anterolateral approaches led to significantly higher cup anteversion compared to lateral approaches (27.3° ± 5.5; 20.9° ± 7.2; 17.5° ± 6.6; p < 0.001 and p = 0.001, respectively). Mean anteversion increased to 24.6° (± 8.0) after 1 year (p < 0.001). Only one revision occurred because of implant dislocation. Wear rates from UHMWPE-X and UHMWPE-XE did not differ significantly. Anteversion angles ≥ 25° correlated to increased polyethylene wear (23.7 µm/year ± 12.8 vs. 31.1 µm/year ± 22.8, p = 0.012) and this was amplified when inclination angles were ≥ 50° (23.6 µm/year ± 12.8 vs. 38.0 µm/year ± 22.7, p = 0.062). CONCLUSION: Anterior approaches lead to the highest inaccuracy of cup placement, but cup positioning outside the Lewinnek safe zone does not necessarily cause higher dislocation rates. Moreover, mean anteversion increased by approximately four degrees within the first year after operation, which is expected to be functional due to a regularization of pelvic tilt after intervention. Mid-term wear rates of UHMWPE-X and UHMWPE-XE liners are comparable, but steep cup positions lead to significantly increased polyethylene wear. In summary, a re-evaluation of target zones for intraoperative cup positioning might be considered. In the long-term reduced oxidative embrittlement could lead to superior wear behaviour of vitamin E-blended liners.

Complexity and sophistication of Early Middle Paleolithic flint tools revealed through use-wear analysis of tools from Misliya Cave, Mount Carmel, Israel.

The Early Middle Paleolithic (EMP) is a less-studied phase of the Levantine Middle Paleolithic, attributable to the small number of sites discovered. Drawing on the dense archaeological accumulations at Misliya Cave, Mount Carmel, Israel, the present study seeks to trace EMP daily activities and behavioral patterns through the prism of use-wear analysis. The emergence of the laminar and Levallois technologies that form the EMP toolkit is investigated to reveal other dimensions of tool novelties. Through microscopic analyses, integrated with experimentation, the most outstanding aspect revealed in this study is the extensive evidence of hafting, which included the use of binding together with various techniques for tool design. A unique treatment was identified, never reported before, entailing the abrasion of cortical surfaces and protruding dorsal ridges. Other aspects include the clear preference for pointed tools as a leading morphological trend and the use of retouch as a mean to create durable working edges and facilitate grip arrangements. The analysis demonstrates the venue of use-wear to trace a wide variety of practices, including consumption-related (processing hunted game and edible plants) and craft-related (hide processing, woodworking, and perhaps stone working) activities that otherwise hardly leave a trace in the archaeological record. By exploring these features, the research provides important insights into early hominin behavior and way of life during the EMP, emphasizing the novelties brought by the earliest Homo sapiens out of Africa.

Vitamin E-blended highly cross-linked polyethylene liners in total hip arthroplasty: a randomized, multicenter trial using virtual CAD-based wear analysis at 5-year follow-up.

BACKGROUND: Progressive oxidation of highly cross-linked ultra-high molecular weight (UHMPWE-X) liners is considered to be a risk factor for material failure in THA. Antioxidants such as vitamin E (alpha-tocopherol) (UHMWPE-XE) were supplemented into the latest generation of polyethylene liners. To prevent inhomogenous vitamin E distribution within the polymer, blending was established as an alternative manufacturing process to diffusion. The purpose of the present study was to investigate the in vivo wear behavior of UHMWPE-XE in comparison with conventional UHMWPE-X liners using virtual CAD-based radiographs. METHODS: Until now, 94 patients from a prospective, randomized, controlled, multicenter study were reviewed at 5-year follow-up. Of these, 51 (54%) received UHMWPE-XE and 43 (46%) UHMWPE-X liners. Anteroposterior pelvic radiographs were made immediately after surgery and at 1 and 5 years postoperatively. The radiographs were analyzed using the observer-independent analysis software RayMatch® (Raylytic GmbH, Leipzig, Germany). RESULTS: The mean wear rate was measured to be 23.6 µm/year (SD 13.7; range 0.7-71.8 µm). There were no significant differences between the two cohorts (UHMWPE-X: 23.2 µm/year vs. UHMWPE-XE: 24.0 µm/year, p = 0.73). Cup anteversion significantly changed within the 1st year after implantation independent from the type of polyethylene liner [UHMWPE-X: 18.2-23.9° (p = 0.0001); UHMWPE-XE: 21.0-25.5° (p = 0.002)]. No further significant changes of cup anteversion in both groups were found between year 1 and 5 after implantation [UHMWPE-X (p = 0.46); UHMWPE-XE (p = 0.56)]. CONCLUSION: The present study demonstrates that the addition of vitamin E does not adversely affect the midterm wear behavior of UHMWPE-X. The antioxidative benefit of vitamin E is expected to become evident in long-term follow-up. Cup anteversion increment by 5° within the 1st year is likely a result of the released hip flexion contracture resulting in an enhanced posterior pelvic tilt. Therefore, a reassessment of target values in acetabular cup placement might be considered.

Pounding tools in HWK EE and EF-HR (Olduvai Gorge, Tanzania): Percussive activities in the Oldowan-Acheulean transition.

In this paper, we present pounded objects from excavations at HWK EE and EF-HR, which are studied from macro and microscopic perspectives. Analysis of HWK EE revealed one of the largest collections of percussive objects from Olduvai Gorge, while excavations at EF-HR have allowed us to recover a much wider collection of percussive tools than previously recorded. Differences are observed between the two localities. At the Acheulean site of EF-HR, percussive tools were predominantly used in the production of flakes and large cutting tools (LCTs). At the Oldowan site of HWK EE, the tool repertoire probably related to a wider range of activities, including bone breaking and bipolar knapping. Comparison of these two assemblages, potentially produced by different hominin species, helps provide a wider picture of pounding activities during the Oldowan-Acheulean transition at Olduvai Gorge.

Wear Analysis of Highly Cross-Linked Polyethylene in Young and Active Patients at Average Fourteen Years: A Concise Follow-Up of a Previous Report.

BACKGROUND: Concerns persist regarding the oxidative stability of annealed highly cross-linked polyethylene (HXLPE) and hence its wear performance especially long term in young and active patients. The purpose of this study is to assess the wear rates and clinical outcomes of a first-generation annealed HXLPE. METHODS: Forty-six patients (57 hips) with noncemented fixation, a mean age of 53 years, and a mean University of California Los Angeles activity score of 8 underwent primary total hip arthroplasty. A 28-mm femoral head against HXLPE liner was used in all cases. Linear wear rates were measured by 2 independent observers. Radiological and clinical assessments were recorded. RESULTS: At a mean of 14 years (range 10-17), the wear rate was 0.03 mm/y (SD ±0.02). There were no revisions for wear-related complications. Using revision for wear-related complications as an endpoint, the survivorship was 100% and we observed no osteolysis. Western Ontario and McMaster Universities Osteoarthritis Index, patient administered questionnaire, and Hospital for Special Surgery hip scores were 91/100, 5/100, and 37/40 respectively. CONCLUSION: This study confirms that a first-generation annealed HXLPE shows excellent wear and clinical results at 10-17 years in young and active patients. Oxidative degradation of an annealed HXLPE does not adversely affect wear and shows no other wear-related complications.

10-Year Follow-Up Wear Analysis of Marathon Highly Cross-Linked Polyethylene in Primary Total Hip Arthroplasty.

BACKGROUND: Short-term and intermediate-term wear rates for highly cross-linked polyethylene (HCLPE) liners in total hip arthroplasty (THA) are significantly lower than published rates for traditional polyethylene liners. The aim of this study was to report the longest-to-date follow-up of a specific HCLPE liner. METHODS: A series of 35 THAs using a specific HCLPE liner were reviewed. Anteroposterior radiographs were reviewed for femoral head penetration, the presence of femoral and/or acetabular osteolysis, long-term survival, total wear, and wear rates in all patients. RESULTS: The average patient age at time of surgery was 70 years with an average follow-up of 10 years (118 months; range, 7.2-13.4 years). The mean wear rate in our cohort was 0.07 mm/y. Total wear was 0.71 mm over the study period. No hips showed evidence of osteolysis in any zones. Survivorship at latest follow-up was 100% with all-cause revision as an end point. CONCLUSION: The wear rate of HCLPE liners continues to be lower than published wear rates for traditional polyethylene and continues to reaffirm the acceptably low wear rates using HCLPE acetabular liner in primary THA.

Characterizing the Lower Paleolithic bone industry from Schöningen 12 II: A multi-proxy study.

Although preservation of Paleolithic faunal assemblages from open-air settings is often poor, the Lower Paleolithic sites of Schöningen provide exceptionally well-preserved mammalian faunal material for investigating hominin/animal relationships. Pleistocene fossil assemblages, however, usually reflect a complex taphonomic history in which natural and anthropogenic processes are often superimposed. A number of examples of osseous finds that resemble tools were recently discovered in the MIS 9 deposits of Schöningen 12 II. Non-anthropogenic agents are known to produce surface modifications mimicking human artifacts and the identification of osseous remains used and/or deliberately modified by ancient hominins is often controversial in such old contexts. Multiple lines of evidence are thus useful for distinguishing between osseous artifacts and "eco-facts". In this paper, the recognition of the use of bone for different technological purposes by late Middle Pleistocene hominins is addressed through a multi-proxy study combining geoarcheology, bone taphonomy, zooarcheology, and use-wear analysis. This allowed the identification of the processes and agents responsible for the formation and modification of the different bone assemblages of Schöningen 12 II. Our analysis points to different types of bones having been likely used as tools. These results expand the diversity of the organic technological repertoire of the Middle Pleistocene hominins, making Schöningen 12 II a remarkable new source of information on osseous technology long before the Upper Paleolithic, the period traditionally viewed as the start of the systematic use of bone tools. Together with other observations of bone tools documented during the Lower and Middle Paleolithic, the results from Schöningen show that archeologists may have underestimated the diversity and importance of osseous technology among archaic hominins.

Minimum 10-Year Wear Analysis of Highly Cross-Linked Polyethylene in Cementless Total Hip Arthroplasty.

Fifty-four patients (64 hips) underwent cementless total hip arthroplasty between 2000 and 2003 with a 22-mm zirconia ceramic bearing on highly cross-linked polyethylene, and were evaluated with a mean 11.9-year postoperative follow-up (range, 10-14 years). Linear wear was measured on the anteroposterior radiograph of the hip. No evidence of osteolysis and loosening was found on the final radiograph in any of the cases, and the steady-state linear wear rate was 0.017±0.018 mm/year. No significant correlation was found between the linear wear rate and age, body weight, cup inclination angle, or polyethylene thickness. Highly cross-linked polyethylene showed excellent wear resistance for >10 years when used in combination with 22-mm zirconia heads.

10-year follow-up wear analysis of first-generation highly crosslinked polyethylene in primary total hip arthroplasty.

Our goal was to report a 10-year follow up of linear penetration rates for HCLPE, and to determine whether a difference exists between penetrations measured on pelvis or hip anterior-posterior radiographs. We reviewed 48 total hip arthroplasties where a first-generation HCLPE liner was used. Femoral head penetration was measured on both AP pelvis and hip radiographs. Total wear and wear rate at 10 years were 1.26 mm and 0.122 mm/y, respectively. The rate decreased significantly after the first 2-3 years, plateauing at a wear rate of 0.05 mm/y for the last 5 years. The AP hip total wear and wear rate were 1.38 mm and 0.133 mm/y respectively, while rates were 1.13 mm and 0.109 mm/y respectively for the pelvis radiographs (P<.05). We found a significant difference in measurements of linear penetration when comparing AP pelvis vs. hip radiographs with lower rates recorded using an AP pelvis.

Complex dental wear analysis reveals dietary shift in Triassic placodonts (Sauropsida, Sauropterygia).

Placodonts were durophagous reptiles of the Triassic seas with robust skulls, jaws, and enlarged, flat, pebble-like teeth. During their evolution, they underwent gradual craniodental changes from the Early Anisian to the Rhaetian, such as a reduction in the number of teeth, an increase in the size of the posterior palatal teeth, an elongation of the premaxilla/rostrum, and a widening of the temporal region. These changes are presumably related to changes in dietary habits, which, we hypothesise, are due to changes in the type and quality of food they consumed. In the present study, the dental wear pattern of a total of nine European Middle to Late Triassic placodont species were investigated using 2D and 3D microwear analyses to demonstrate whether there could have been a dietary shift or grouping among the different species and, whether the possible changes could be correlated with environmental changes affecting their habitats. The 3D analysis shows overlap between species with high variance between values and there is no distinct separation. The 2D analysis has distinguished two main groups. The first is characterised by low number of wear features and high percentage of large pits. The other group have a high feature number, but low percentage of small pits. The 2D analysis showed a correlation between the wear data and the size of the enlarged posterior crushing teeth. Teeth with larger sizes showed less wear feature (with higher pit ratio) but larger individual features. In contrast, the dental wear facet of smaller crushing teeth shows more but smaller wear features (with higher scratch number). This observation may be related to the size of the food consumed, i.e., the wider the crown, the larger food it could crush, producing larger features. Comparison with marine mammals suggests that the dietary preference of Placochelys, Psephoderma and Paraplacodus was not exclusively hard, thick-shelled food. They may have had a more mixed diet, similar to that of modern sea otters. The diet of Henodus may have included plant food, similar to the modern herbivore marine mammals and lizards. Supplementary Information: The online version contains supplementary material available at 10.1186/s13358-024-00304-x.

Numerical investigation on the wear characteristics of hip implant under static loading.

Modern hip arthroplasty still faces the issue of wear in the articulating surface and wear induced debris. Thus, the design of hip implant is highly important for its longevity. Experimental demonstration of wear in hip implant involves both time and cost and, in this regard, finite element analysis acts as a suitable alternative. In this work, the wear characteristics of design modified and surface modified femoral head is studied. Femoral head is assumed to be made of Ti6Al4V and liner material is taken as UHMWPE. Design of the femoral head is modified by providing grooves on the femoral head as well as by providing an additional liner on the femoral head surface. Surface of the femoral head is modified with square or circular dimples. This work involves the development of femoral head model and its simulation using ANSYS under static load condition to get the contact pressure and sliding distance. Modified Archard's wear equation uses the contact stress and sliding distance to determine the wear volume produced per year and the obtained results are compared with that in the available literature. The study shows that the wear rate reduced up to 10% by surface modification and 3% by design modifications.

The Ornaments of the Arma Veirana Early Mesolithic Infant Burial.

Personal ornaments are widely viewed as indicators of social identity and personhood. Ornaments are ubiquitous from the Late Pleistocene to the Holocene, but they are most often found as isolated objects within archaeological assemblages without direct evidence on how they were displayed. This article presents a detailed record of the ornaments found in direct association with an Early Mesolithic buried female infant discovered in 2017 at the site of Arma Veirana (Liguria, Italy). It uses microscopic, 3D, and positional analyses of the ornaments as well as a preliminary perforation experiment to document how they were perforated, used, and what led to their deposit as part of the infant's grave goods. This study provides important information on the use of beads in the Early Mesolithic, in general, as well as the relationship between beads and young subadults, in particular. The results of the study suggest that the beads were worn by members of the infant's community for a considerable period before they were sewn onto a sling, possibly used to keep the infant close to the parents while allowing their mobility, as seen in some modern forager groups. The baby was then likely buried in this sling to avoid reusing the beads that had failed to protect her or simply to create a lasting connection between the deceased infant and her community. Supplementary Information: The online version contains supplementary material available at 10.1007/s10816-022-09573-7.

Mechanical, corrosion and biological behavior of centrifugal casting processed Mg-2Zn-1Mn alloy reinforced with ß Tricalciumphosphate (ßTCP) for orthopaedic applications.

Zinc and manganese were selected to develop magnesium alloys along with the bioactive ceramic ß Tricalciumphosphate (ßTCP) for biomedical applications fabricated by centrifugal casting. Microstructure, mechanical properties, corrosion properties, and biocompatibility of the Mg-2Zn-1Mn-xßTCP (x = 0, 2.5, 5 wt%) alloys have been investigated by use of an optical microscope, field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, XRD analysis, mechanical testing, cell toxicity and blood hemolysis. A microstructure study has shown that the addition of ßTCP significantly reduces the size of the grain. The experimental results of mechanical testing and corrosion studies show that the Mg-2Zn-1Mn-2.5ßTCP alloy performs better among the three alloys developed, and the values in Vicker's microhardness, compressive strength, density, and porosity with 47.32HV, 238.22 MPa,1.75 g/cm3 and 2.28% respectively and the values of corrosion potential (Ecorr), corrosion current density (Icorr), linear polarization resistance (Rp) and corrosion rate (mm/year) of the Mg-2Zn-1Mn-2.5 ßTCP alloy in the outer and inner layers were found to be -1.46V, 2.71 ×10-5 A/cm2, 1677Ω, 0.62 mm/year and -1.41V, 3.92 ×10-6A/cm2, 4286Ω, 0.20 mm/year respectively. MTT Test and hemolysis experiments revealed that the magnesium alloy had no cell toxicity and good cytocompatibility, however, it produced hemolysis to the blood system. It was proposed that surface modification be used to improve the blood compatibility of the magnesium alloy for use in blood environments.

Wear Analysis of Additively Manufactured Slipper-Retainer in the Axial Piston Pump.

Additive manufacturing (AM) of spare parts is going to become more and more common. In the case of hydraulic solutions, there are also some applications of AM technology related to topological optimization, anti-cavitation improvements, etc. An examination of all available research results shows that authors are using specialized tools and machines to properly prepare AM spare parts. The main aim of this paper is to analyze the influence of quick repair of the damaged slipper-retainer from an axial piston pump by using an AM spare part. Hence, it was prepared with a 100-h test campaign of the AM spare part, which covers the time between damage and supply of the new pump. The material of the slipper-retainer has been identified and replaced by another material-available as a powder for AM, with similar properties as the original. The obtained spare part had been subjected to sandblasting only to simulate extremely rough conditions, directly after the AM process and an analysis of the influence of the high surface roughness of AM part on wear measurements. The whole test campaign has been divided into nine stages. After each stage, microscopic measurements of the pump parts' surface roughness were made. To determine roughness with proper measurements, a microscopical investigation was conducted. The final results revealed that it is possible to replace parts in hydraulic pumps with the use of AM. The whole test campaign caused a significant increase in the surface roughness of the pump's original parts, which was worked with the AM spare slipper-retainer: (1) from Ra = 0.54 µm to Ra = 3.84 µm in the case of two tested pistons; (2) from Ra = 0.33 µm to Ra = 1.98 µm in the case of the slipper-retainer. Despite significant increases in the surface roughness of the pump's parts, the whole test campaign has been successfully finished without any damages to the other important parts of the whole hydraulic test rig.

Analysis of hip joint cross-shear under variable activities using a novel virtual joint model within Visual3D.

Cross-shear forces occur between bearing surfaces at the hip and have been identified as a key contributor to prosthesis wear. Understanding the variation in relative motion paths between both individuals and activities, is a possible explanation for increased revision rates for younger patients and could assist in improved pre-clinical testing regimes. Additionally, there is little information for the pre-clinical testing of cartilage substitution therapies for younger more active individuals. The calculation of motion paths has previously relied on computational modelling software which can be complex and time-consuming. The aim of this study was to determine whether the motion paths calculations could be integrated into gait analysis software to improve batch processing, reduce analysis time and ultimately improve the efficiency of the analysis of cross-shear variation for a broader range of activities. A novel Virtual Joint model was developed within Visual3D for calculating motion paths. This model was compared to previous computational methods and found to provide a competitive solution for cross shear analysis (accuracy <0.01 mm error between methods). The virtual hip model was subsequently applied to 13 common activities to investigate local aspect ratio's, velocities and accelerations. Surprisingly walking produced the harshest cross shear motion paths in subjects. Within walking, of additional interest was that the localised change in acceleration for subjects was six times greater compared to the same point on an equivalent smoothed simulator cycle. The Virtual hip developed in Visual 3D provides a time saving technique for visualising and processing large data sets directly from motion files. The authors postulate that rather than focussing on a generalised smoothed cross-shear model that pre-clinical testing of more delicate structures should consider localised changes in acceleration as these may be more important in the assessment of cartilage substitutes sensitive to shear.

A durability study of a compression ignition engine operating with Thumba (Citrullus colocyntis) vegetable oil.

Vegetable oils are found suitable alternate of diesel fuel as per the results of short-run studies. Long-run studies with vegetable oil as a fuel pointed out the problems related to wear and maintenance of the engine. A single cylinder, variable compression ratio diesel engine was tested for 512 h (32 cycles of 16 h per day) to investigate longevity implications of fueling Thumba vegetable oil. Results of the study revealed that a very little damage was observed over the running surface of the cylinder liner, piston rings, valves, and valve seats. Wear in the piston outer diameter was observed to be 13 to 30 microns. Cylinder wear was about 80 microns. The closed gap in the oil piston ring increased up to 200 microns. Heavy carbon deposition was found on different internal parts of the engine, which indicates poor combustion of fuel. Amount of copper (66 mg/kg) and silicon (112 mg/kg) dissolved in the lubricating oil was found more than permissible limits (Cu 50 mg/kg, Si 25 mg/kg), after 450-h engine test run. But all the dissolve materials remain in allowable limits when the durability test conducted with diesel. Smoke, CO, HC, and NOX emissions were found to increase initially then decrease in the further engine running hours. But these emissions were found inferior to the engine emissions fueled with diesel in all the running hours. CO2 emissions were found superior throughout the test with the preheated T20 Thumba oil blend than diesel. The maximum reduction in the viscosity of the lubricating oil, during endurance testing, was found 60 centipoises but it was found 25 centipoises when the test conducted with diesel.

No Difference in Conventional Polyethylene Wear Between Yttria-stabilized Zirconia and Cobalt-chromium-molybdenum Femoral Heads at 10 Years.

BACKGROUND: Concerns have arisen regarding deterioration of wear properties of yttria-stabilized zirconia (YSZ) femoral head on conventional polyethylene (PE) bearings due to YSZ phase transformation. QUESTIONS/PURPOSES: The purpose of this study was to determine if there is a difference in long-term PE wear properties between YSZ and cobalt-chromium-molybdenum (Co-Cr-Mo) femoral heads. METHODS: Ten-year radiographic wear assessment was performed on a cohort of patients enrolled in a prospective randomized clinical trial comparing total hip arthroplasty with YSZ or Co-Cr-Mo femoral heads on conventional, non-cross-linked PE. RESULTS: PE linear wear, annualized wear, and steady-state wear rates remained low and similar between groups. No cases of osteolysis were observed. CONCLUSIONS: Measured conventional PE wear was similar between YSZ and Co-Cr-Mo femoral heads with the steady-state wear rates for both remaining below the generally accepted threshold at which osteolysis typically occurs. Whether clinically relevant phase transformation with YSZ femoral heads occurs is uncertain; however, the use of YSZ femoral heads in this study was not associated with increased PE wear, osteolysis, or deterioration of wear properties.

Wear performance of retrieved metal-on-metal Pinnacle hip arthroplasties implanted before and after 2007.

OBJECTIVES: Previous studies have suggested that metal-on-metal (MoM) Pinnacle (DePuy Synthes, Warsaw, Indiana) hip arthroplasties implanted after 2006 exhibit higher failure rates. This was attributed to the production of implants with reduced diametrical clearances between their bearing surfaces, which, it was speculated, were outside manufacturing tolerances. This study aimed to better understand the performance of Pinnacle Systems manufactured before and after this event. METHODS: A total of 92 retrieved MoM Pinnacle hips were analyzed, of which 45 were implanted before 2007, and 47 from 2007 onwards. The 'pre-2007' group contained 45 implants retrieved from 21 male and 24 female patients, with a median age of 61.3 years (interquartile range (IQR) 57.1 to 65.5); the '2007 onwards' group contained 47 implants retrieved from 19 male and 28 female patients, with a median age of 61.8 years (IQR 58.5 to 67.8). The volume of material lost from their bearing and taper surfaces was measured using coordinate and roundness measuring machines. These outcomes were then compared statistically using linear regression models, adjusting for potentially confounding factors. RESULTS: There was no significant difference between the taper and bearing wear rates of the 'pre-2007' and '2007 onwards' groups (p = 0.67 and p = 0.39, respectively). Pinnacles implanted from 2007 onwards were revised after a mean time of 50 months, which was significantly earlier than the 'pre-2007' hips (96 months) (p < 0.001). A reduction in the time to revision was present year on year from 2003 to 2011. CONCLUSION: We found no difference in the wear rate of these implants based on the year of implantation. The 'pre-2007' hips had a two-fold greater time to revision than those implanted after 2007; this may be due to the increased surveillance of MoM hips following UK regulatory advice and several high-profile failures. Interestingly, we observed a decreasing trend in the mean time to revision every year from 2003 onwards.Cite this article: S. Bergiers, H. S. Hothi, J. Henckel, A. Eskelinen, J. Skinner, A. Hart. Wear performance of retrieved metal-on-metal Pinnacle hip arthroplasties implanted before and after 2007. Bone Joint Res 2018;7:595-600. DOI: 10.1302/2046-3758.711.BJR-2018-0143.R1.

Development of a preclinical natural porcine knee simulation model for the tribological assessment of osteochondral grafts in vitro.

In order to pre-clinically evaluate the performance and efficacy of novel osteochondral interventions, physiological and clinically relevant whole joint simulation models, capable of reproducing the complex loading and motions experienced in the natural knee environment are required. The aim of this study was to develop a method for the assessment of tribological performance of osteochondral grafts within an in vitro whole natural joint simulation model. The study assessed the effects of osteochondral allograft implantation (existing surgical intervention for the repair of osteochondral defects) on the wear, deformation and damage of the opposing articular surfaces. Tribological performance of osteochondral grafts was compared to the natural joint (negative control), an injury model (focal cartilage defects) and stainless steel pins (positive controls). A recently developed method using an optical profiler (Alicona Infinite Focus G5, Alicona Imaging GmbH, Austria) was used to quantify and characterise the wear, deformation and damage occurring on the opposing articular surfaces. Allografts inserted flush with the cartilage surface had the lowest levels of wear, deformation and damage following the 2 h test; increased levels of wear, deformation and damage were observed when allografts and stainless steel pins were inserted proud of the articular surface. The method developed will be applied in future studies to assess the tribological performance of novel early stage osteochondral interventions prior to in vivo studies, investigate variation in surgical precision and aid in the development of stratified interventions for the patient population.