Liner Failure Research Articles

Head size in Delta ceramic-on-ceramic total hip arthroplasty: a comparative registry study.

Optimal bearing size in total hip arthroplasty (THA) has not been clearly ascertained, but large diameter ceramic balls may improve function and implant stability, with minimal concerns for wear. Delta ceramic-on-ceramic (COC) THA were stratified based on head diameter (32, 36 and 40mm), aiming to assess: 1) survival rates, reasons for revision and hazard ratios for failure; 2) survival rates and hazard ratios for aseptic loosening, dislocation/primary instability, liner failure. A regional arthroplasty registry was enquired about Delta COC THA performed for primary osteoarthritis, stratified by head size. 13,161 primary cementless THAs were included in the study, with a mean follow-up of 5.7years (range: 0-17): 3980 (30.2%) 32mm balls, 8327 (63.3%) 36mm heads, 854 (6.5%) 40mm heads. The three cohorts achieved similar survival rates (p = 0.99) and adjusted hazard ratios (p > 0.05). No revisions for head breakage or metallosis occurred. When revision for cup aseptic loosening was the endpoint, the survival rates of three cohorts (p = 0.08) and the adjusted hazard ratios (p > 0.05) were similar. The three cohorts achieved comparable survival rates when revision for dislocation/primary instability was the endpoint (p = 0.08). When the endpoint was revision for liner breakage, 32mm cohort showed higher rates of revision (p = 0.01). No liner failure was detected in the 40mm cohort. 32mm, 36mm and 40mm provided similar 10-year survival rates in Delta COC THA. 40mm heads emerged as safe options but did not lower the revisions for dislocations/primary instability. IV (therapeutic study).

Systematic schemes for buckling analyses of a subsea bio-inspired non-circular FGM polyhedral liner with an arch invert

This study develops theoretical frameworks for the buckling failure of a non-circular thin-walled liner encased in a cracked pipeline with an arch invert. The buckling performance of the pipeline-liner system is improved by combining the polyhedral profiles and the Functionally Graded Materials (FGM). The liner is close-fitting to the inner surface of the pipeline. The energy function is obtained by assembling the thin-walled shell principle and the theory of minimum potential energy. Then, the nonlinear equilibrium equations and the buckling equations are derived to predict the buckling performances of the FGM polyhedral pipeline-liner system with an arch invert. Moreover, the present buckling behaviors of the system are compared with other available results, and good agreements are accomplished when the FGM polyhedral liner degenerates into an FGM circular liner or a homogeneous polyhedral liner. In addition, an enhancement coefficient is defined as the ratio of the buckling pressure of a polyhedral liner to a circular one. Finally, several key geometric and material parameters are examined to quantify their effects on the buckling behavior of the FGM polyhedral pipeline-liner system with an arch invert. These parameters are volume fraction exponents, polyhedral shapes, and thickness-to-radius ratios, respectively.

The Use of Large Metal Heads in Thin Vitamin E–Doped Cross-Linked Polyethylene Inserts Does Not Increase Polyethylene Wear in Total Hip Arthroplasty: 5-Year Results From a Randomized Controlled Trial

BackgroundVitamin E–doped cross-linked polyethylene (VEPE) has encouraged the use of larger heads in thinner liners in total hip arthroplasty (THA). However, there are concerns about wear and mechanical failure of the thin liner, especially when metal heads are used. The aim of this randomized controlled trial was to investigate if the use of a large metal head in thin VEPE liner would increase polyethylene wear compared with a standard 32-mm metal head and to compare periacetabular radiolucencies and patient-reported outcomes in THA. MethodsThere were 96 candidates for uncemented THA who were randomly allocated to either the largest possible metal head (36 to 44 mm) that could be fitted in the thinnest available VEPE liner (intervention group) or a standard 32-mm metal head (control group). The primary outcome was proximal head penetration, measured with a model-based radiostereometric analysis. Secondary outcomes were periacetabular radiolucencies and patient-reported outcomes. The midterm results of the trial at 5 years are presented. ResultsThe median total proximal head penetration (interquartile range) was −0.04 mm (−0.12 to 0.02) in the intervention group and −0.03 mm (−0.14 to 0.05) in the control group (P = .691). The rates of periacetabular radiolucencies were 1 of 44 and 4 of 42 (P = .197), respectively. Patient-reported hip function and health-related quality of life did not differ between the groups, but participants in the intervention group reported a higher level of activity (median University of California Level of Activity score 7 versus 6, P = .020). There were 5 revisions caused by dislocations (2), periprosthetic fracture (1), stem subsidence (1), or iliopsoas impingement (1). ConclusionsLarge metal heads in thin VEPE liners did not increase liner wear and were not associated with liner failure 5 years after THA.

Polymer Fatigue Evaluation Methodology for Unbonded Flexible Pipes

Polymer layers have been used in the offshore Oil & Gas industry for many years in unbonded flexible pipes for static and dynamic applications. The evaluation of fatigue performance for polymer grades in such applications is complex and no qualification method is well defined nor standardized at the time this article is written.Though historically no reported polymer fatigue field failures the complexity of unbonded flexible pipes, the conservatism of this industry makes the introduction of new polymer grades in risers for dynamic applications challenging. Development of a polymer fatigue methodology will allow the industry to quantitatively evaluate risks of fatigue failure of liners and thereby be important in introducing new material grades.In this paper, a design fatigue methodology is built based on inputs from a specific project and results from small- and full-scale tests. The pipe curvature ranges, extracted from the project location, are used to obtain an accumulated tensile strain which is then converted into an accumulated tensile stress. The fatigue damage is then determined, using a design curve established from bending or tension-tension fatigue testing performed on dumbbells from pipe samples. Parameters are included to reflect geometrical effects from manufacturing process but also service life conditions with several temperature profiles. This method can be applied for pressure sheaths as well as sealed outer sheaths with relevant inputs related to their operating conditions. The obtained fatigue damage can then be used to validate the use of polymer grades for specific unbonded pipe designs under their service conditions.

An investigation on enhancing the bonding properties of PA11-CFRP interface in type IV high pressure hydrogen storage vessel through nanosecond pulsed laser treatment and failure mechanism research

At present, several key technologies remain to be addressed in the development of type IV high-pressure hydrogen storage vessels, especially the prevention of plastic liner collapse, which demands urgent resolution. One major factor contributing to plastic liner collapse is the weak interfacial bonding between the plastic liner and carbon fiber reinforced polymer (CFRP). Therefore, enhancing the bonding properties of the plastic liner-CFRP interface can effectively reduce the risk of liner failure. Nanosecond pulsed laser surface treatment, known for its high efficiency, precise control, and automation capabilities, was employed in this study to modify the surface of the PA11 liner. The bonding properties of the PA11-CFRP interface were comprehensively investigated through climbing drum peel (CDP) tests, flatwise tensile (FWT) tests, and surface performance assessments. Utilizing the Optimization module within the Response Surface Method (RSM) software Design Expert for analysis, it was found that, under the optimal parameters of 400 mm/s, 20 kHz, and 12.7 W for nanosecond pulsed laser treatment, the CDP strength increased to 24.1 N mm/mm, which was 4.74-fold higher than that of untreated samples. The FWT strength reached 2.43 MPa, which was 8.35-fold higher than that of untreated samples. The increase in interfacial bonding strength after laser treatment primarily resulted from the formation of periodic grooves on the PA11 surface, along with an increase in surface roughness. This approach presents a promising direction for the surface treatment of plastic liners in type IV hydrogen storage vessels prior to winding and is poised to enhance the safety of such vessels.

A closer look at the corrosion of steel liner embedded in concrete

Containment wall of nuclear power plants is an example of a concrete structure enveloping a steel liner plate. In this research, the situations observed in connection with liner failures were investigated, namely the presence of a piece of wood (foreign matter) and a delamination gap between steel liner and concrete, with the purpose to study and define the corrosion mechanism of the steel liner plate and identify which factors promote or impede the occurrence of corrosion.Specimens were concrete slabs containing a steel plate, an inlay to modify the conditions at the steel surface, and electrodes for electrochemical measurements. The inlays represented “normal” concrete, low-pH concrete, a piece of wood, and a delamination gap between concrete and steel, and the same systems supplemented with chlorides. The results from two-year tests with wetting-drying cycles revealed localized corrosion in steel underneath the piece of wood, close to the inlay perimeter. The attack could be explained mainly by the mechanism of crevice corrosion. In contrast, no corrosion attack of steel liner could be detected in specimens with the delamination gap. The results from the experiments and steel liner characterization are provided in this paper, together with the reasoning behind the proposed degradation mechanism.

A numerical approach for assessing internal pressure capacity at liner failure in the expanded free-field of the prestressed concrete containment vessel

Since containment building is the major shielding structure to ensure safety of nuclear power plant, the structural behavior and ultimate pressure capacity of containments must be studied in depth. This paper addresses ambiguous issue of determining free-field position for liner failure by suggesting an expanded free-field region and comparing internal pressure capacities obtained by test data, conservative assumption and suggested free-field region. For this purpose, a practical approach to determine the free-field position for the evaluation of liner tearing is carried out. The maximum principal strain histories versus internal pressure capacities among different free-field positions at various azimuths and elevations are compared with those at the equipment hatch as a conservative assumption. The comparison shows that there are considerable differences in the internal pressure capacity at liner failure within the expanded free-field region compared to the vicinity of the equipment hatch. Additionally, this study proposes an approximate correlation with conservative factors by considering the expanded free-field ranges and material characteristics to determine realistic failure criteria for liner. The applicability of the proposed correlation is demonstrated by comparing the internal pressure capacities of full-scale containment buildings following liner failure criteria according to RG 1.216 and an approximate correlation.

Highly Crosslinked Polyethylene Liner Thickness Does Not Influence Survival in Primary Total Hip Arthroplasty After Mean Follow-Up of 13 Years: A Study of 2,565 Hips With a Single Design Liner

BackgroundConcerns remain that thinner highly crosslinked polyethylene (HXLPE) liners in modern total hip arthroplasty (THA) may lead to premature liner-related failures or revision. The aim of this study was to evaluate the effect of liner thickness on survival and revision rates of HXLPE in primary THA after more than 10 years. MethodsWe retrospectively identified 2,565 primary THAs using HXLPE with a mean follow-up of 13 years (range, 11 to 19). Patients were grouped for each mm of polyethylene thickness. Liner thickness varied from 4.9 to 12.7 mm, with one third measuring less than 6 mm. Primary outcomes were reoperation, all-cause revision, and liner-related revision. ResultsThe reoperation rate was 7.3%, the all-cause revision rate was 5.6%, and the liner-related revision rate was 0.04%. There was no significant difference in all-cause revision when stratified by liner thickness (P = .286) and liner thickness was not associated with liner-related revision (n = 1). There was a statistically, but not clinically significant difference in mean liner thickness for the cohort that underwent reoperation (7.09 versus 6.89 mm, P = .01) and all-cause revision (7.16 versus 6.89 mm, P = .031). ConclusionIn our cohort, liner thickness was not associated with all-cause revision-free survival, and there was no clinically significant difference in liner thickness between those patients who did require a reoperation or all-cause revision, and those who did not. There was only 1 liner-related failure in the entire cohort. Our results indicate that using thinner HXLPE liners to maximize femoral head size in THA is a safe practice that does not lead to increased revision rates or liner failure at a mean 13-year follow-up.

Early failure of a highly cross-linked polyethylene inlay after total hip arthroplasty probably due to insufficient irradiation.

Highly cross-linked polyethylene (XLPE) is a major advance in total hip arthroplasty (THA), as it suffers from less wear and thus is associated with lower revision rates than standard ultra-high molecular weight polyethylene. Early failures are reported rarely, and associated with specific design or manufacturing issues. We report a case requiring early revision due to adverse reaction to polyethylene particles. Investigations identified insufficient irradiation as the most probable cause of failure. Here are reported the features of a clinical case with determination of the material properties of the retrieved XLPE liner and establishment of the appropriate calibration curves as reference. Periprosthetic joint infection could be ruled out with appropriate sampling as cause for the inflammatory periarticular tumour. Histology identified a massive macrophagic reaction to micrometric polyethylene particles. No component malposition was present, nor any third-body wear. The trans-vinylene index (TVI) indicated insufficient and potentially detrimental irradiation of the polyethylene, while gel content, crystallinity, melting temperature and oxidation index remained within expected ranges. Histologically proven failure of a XLPE THA liner was identifiable despite correct implantation of the components. The cause of failure most probably was an inadequate irradiation, as indicated by determination of the TVI. This case underscores the importance of histologic workup even in aseptic revisions, and of detailed analysis of retrievals. The calibration curves provided are essential for analysis of other retrievals.

Understanding the impact of adhesion on the mechanical behavior of shotcrete

ABSTRACT Shotcrete is widely used as part of ground support in underground excavations. Although adhesion is recognized as a critical mechanical property of shotcrete, there is no strong consensus from a design perspective on whether high or low adhesion is preferred. This is probably due to our relatively limited understanding of the role of adhesion on the field performance of shotcrete. Laboratory investigations can provide useful insights, but it is difficult to extrapolate to field conditions. Numerical models can complement laboratory investigations, but to develop confidence in their results, they must adequately reproduce the failure mechanism of shotcrete. This paper investigates how different adhesion properties control the mechanical behavior of shotcrete. Laboratory tests were used to calibrate a three-dimensional discrete element method model to capture the adhesion failure of a shotcrete liner. The developed model explicitly reproduced the adhesion failure mechanism, including the load redistribution, loading capacity, and displacement of the shotcrete liner. This was used as a basis for a parametric investigation of the impact of adhesion strength on the mechanical behavior of shotcrete. The numerical results indicated the significant implications in selecting adhesion properties of shotcrete and led to recommendations for adhesion capacity under different ground stress conditions.

Primary THA Using Thin Polyethylene Liners and Large Femoral Heads: A Minimum 5-Year Follow-Up.

Large femoral head sizes are commonly used in total hip arthroplasty (THA) to minimize the risk of instability. With small acetabular cup-size, large femoral head diameter often results in the use of thin polyethylene liners. The purpose of this study was to evaluate clinical and radiographic results of large femoral heads against thin polyethylene liners with minimum 5-year follow-up. This was a retrospective review identifying 58 primary THAs utilizing thin polyethylene inserts from one manufacturer (X3 polyethylene, Stryker, Mahwah, NJ) and large femoral heads (36 mm or greater) with minimum 5-year follow-up. A total of 3 patients were deceased and 11 lost to follow-up, leaving 44 patients for review. All patients were female with mean age 65.7 (range 26-85) and mean body mass index (BMI) 29.9 (range 19.6-45.4). Average length of follow-up was 8.5 years (range 5.1-11.3). Outcome measures included survivorship, complications, PROMs and radiographic analysis. There were four revisions: two aseptic loosening, one prosthetic joint infection, and one recurrent dislocation. Average HOOS-Jr, FJS-12, and patient satisfaction using Likert score was 94.3/100, 92.9/100, and 4.69/5.00, respectively, with 94% of patients reporting being satisfied or very satisfied. Radiographic analysis at average of 8.5 years demonstrated well-fixed implants without evidence of progressive radiolucent lines, osteolysis, or failure of the polyethylene liner. Survivorship using failure of the thin polyethylene liner as the endpoint was 100% at an average of 8.5 years. Thin polyethylene liners used with large femoral head sizes in small acetabular cups demonstrated excellent results at average 8.5-year follow-up with no cases of liner fracture or osteolysis.

Generic creep behavior and creep modeling of an aged surface support liner under tension

Polymer-based materials have been motivated to be an alternative support system element in the mining/tunneling industry due to their logistic and geotechnical benefits. Thin spray-on liner (TSL), a term to define the application of the material on the rock surface with a layer ranging from 2 mm to 10 mm in thickness, shows some promising results. TSLs are mainly composed of plastic, polymer, or cement-based ingredients to a certain proportion. This study intends to reveal the time-dependent response of TSL specimens, cured throughout 500 d, under four constant stress levels for stable laboratory conditions. The results were correlated using two interrelated equations to predict the material's service life (creep-rupture envelopes). The proposed correlations offered an insight into both the effective permanent support time and the strain amount at the liner failure. The time-dependent deformation of TSL, whose performance is highly responsive to creep behavior, was obtained so that the design engineers may use the findings to avoid the severe problems of material creep. Experimental data were also used to develop a Burgers (four-element) creep model. Since the liner has a nonlinear time-dependent behavior, creep models were built for each stress level separately. Subsequently, a generic equation was obtained using the nonlinear parametric dependencies. There is a good agreement between the proposed model and the experimental results. The proposed model can be used as a basis for future numerical studies related to the support behavior of aged surface support liners.

Tripolar Constrained and Dual Mobility Liners Are Both Successful When Cemented Into Tantalum Acetabular Revision Shells in Complex Revision Total Hip Arthroplasty

BackgroundInstability is a common complication after revision total hip arthroplasty. Tripolar constrained (TC) and dual mobility (DM) liners cemented into tantalum acetabular revision (TM) shells are established alternatives that reduce instability risk. This study compares outcomes of TC and DM liners cemented into TM shells in complex revision hip replacements.MethodsFifty cases using a TM shell and a TC or DM cemented liner with at least 12 months of follow-up were identified. There were 25 TC and 25 DM liners. Clinical, radiographic, and patient-reported outcomes were collected. Reasons for re-revision and failures were analyzed.ResultsThe average age was 73 years in the TC group and 75 years in the DM group. The median follow-up duration was 50 months (23 - 96) and 13 months (12 – 21) for the TC and DM groups, respectively. The mean Harris Hip Score improved from 37 to 61 for the TC group and from 51 to 73 in the DM group at the last review. Two TC cases required revision for wear and liner failure. One DM insert was changed at reoperation for periprosthetic femur fracture. There were no failures of cement fixation in either group and no revisions for cup loosening.ConclusionsIn complex revision hip replacement with a history of instability or judged to have a high risk of instability postoperatively, TC and DM liners cemented into tantalum revision shells are both successful, giving acceptable results. The improved arc of movement with DM liners, minimizing impingement, makes them preferable except when there is a global abductor deficiency or severe joint laxity.

Seismic dynamic analysis and structural integrity assessment of the PWR spent fuel pool under beyond design basis earthquake

A series of numerical analyses were carried out to assess the safety of spent fuel pool (SFP) of a pressurized water reactor (PWR) power plant in Taiwan. These analyses performed seismic force evaluation and 3D nonlinear finite element analysis (FEA) for the SFP under beyond design basis earthquake (BDBE). In addition, this study considered various in-structural response spectra (ISRS) with various damping ratios and the reduced factors to account for the partial cracking effects from BDBE. In the seismic force evaluation, the results show that the pool base takes the greatest uniform equivalent loading resulted from the cooling water, racks, and spent fuel components. For the walls, the south wall suffers the greatest equivalent force. The results of 3D FEA indicated that the largest values of stress and strain appear at the bottom corner near south wall of the channel between the main pool and cask loading pit for the overall SFP structure. It is also found that the influences of cracking effects on the seismic force calculation and structural analysis are significant. But comparing the results of numerical analysis by 5% damping ratio with 0.7 reduced factor and 10% damping ratio with 0.5 reduced factor, the impacts on the liner of the SFP are insignificant. Because the cooling water leakage depends on the liner failure, the influence on the leakage is small.

Advances on materials design and manufacture technology of plastic liner of type Ⅳ hydrogen storage vessel

The growing demand for type IV hydrogen tanks with long life, lightweight, high hydrogen storage density characteristics has posed new issues for liners. The paper discusses the causes of liner failure in terms of hydrogen permeation, thermal instability, and mechanical damage, as well as a focused analysis of alternative material optimization strategies. Through a detailed investigation of aggregate state structures, formulations and processes, the principles of material modification, primarily inorganic functional filler/polymer filler filling composite and laminated orientation, and their enhancing effects are sorted out. Besides, the benefits and drawbacks of blow molding, injection and welding, and the rotating technique, which were employed by some manufacturers are contrasted in the article, for overcome the problematic molding of hollow plastic liners with metal BOSS structures. This text will be a valuable resource for material exploitation as well as efficient and reliable molding of various liners. • Improve hydrogen storage density and application range by material modification. • The failure modes of the plastic liner material are discussed. • Hydrogen barrier, mechanical and thermal properties modify measures were reviewed. • Molding methods for synthetic liners containing metal inserts are compared. • The recommendations for future liner materials design and molding are presented.

Cementation of a dual mobility cup in a well-fixed acetabular component- a reliable option in revision total hip arthroplasty?

BackgroundThe “cup-in-cup” technique allows for revision of failed total hip arthroplasty (THA) when the cementless cup is well fixed. Furthermore, it can be used for liner wear or mechanical failure where liner replacement may be impossible or impractical. Recently, the “cup-in-cup” technique in combination with dual mobility cups (DMC) has drawn increased attention. Our aim was to report on the clinical and radiographic outcomes following this surgery.MethodsFrom 2015 to 2020, 33 patients treated with the DMC- “cup in cup” technique were retrospectively reviewed. Fourteen patients had died while 19 were available for the final follow-up (FU), of which 15 underwent both a radiograph and a FU visit, 2 underwent a radiograph only and 2 underwent a telephone interview only. Patient-related outcome measures included the HHS and the WOMAC. Radiographs were assessed for implant loosening and positioning. Primary endpoint was revision of any cause and secondary endpoint was loosening of the DMC at the latest FU. The survival analysis was conducted using the Kaplan-Meier method.ResultsThe mean age at surgery was 78.6 ± 7.1 (63–93) years and the mean surgery duration was 124.4 ± 52.0 (60–245) minutes. Recurrent dislocation (42.4%), periprosthetic fracture (39.4%) and polyethylene wear (6.1%) were the most frequent reasons for surgery. The mean FU duration (n = 19) was 28.5 ± 17.3 (3–64) months. The mean HHS score at FU was 59.4 ± 22.2 (29–91) and the mean WOMAC score was 59.7 ± 25.6 (15.6–93.8).Two cups were revised due to instability and one revision was performed due to periprosthetic joint infection, accounting for an overall cup survival rate of 86.8% after a mean FU of 22.9 ± 18.0 (1.5–64.6) months. The survival rate free of loosening was 90.9% after a mean FU of 22.3 ± 18.5 (1.5–64.7) months.ConclusionsWe found that the cementation of a DMC in a well-fixed cup is a promising short- to mid-term treatment addressing THA instability especially in elderly and frail patients, who benefit from a reduced operation time. Proper cementation technique, adequate cup positioning as well as selection of a sufficiently large DMC are crucial for treatment success. Longer FUs will be needed in the future in order to further prove the benefit of this technique.

Seismic Moment Tensor Inversion of an Induced Microseismic Event, Offshore Norway: An Insight into the Possible Cause of Wellbore Liner Failure during a Drilling Operation

Abstract A microseismic event with Mw∼0.8 was recorded at the Grane oilfield, offshore Norway, in June 2015. This event is believed to be associated with a failure of the wellbore liner in well 25/11-G-8 A. The failure mechanism has been difficult to explain from drilling parameters and operational logs alone. In this study, we analyzed the detected microseismic event to shed light on the possible cause of this event. We inverted for the seismic moment tensor, analyzed the S/P amplitude ratio and radiation pattern of seismic waves, and then correlated the microseismic data with the drilling reports. The inverted seismic moment indicates a shear-tensile (dislocation) event with a strong positive isotropic component (67% of total energy) accompanied by a positive compensated linear vector dipole (CLVD) and a reverse double-couple (DC) component. Drilling logs show a strong correlation between high pump pressure and the occurrence of several microseismic events during the drilling of the well. The strongest microseismic event (Mw∼0.8) occurred during peak pump pressure of 277 bar. The application of high pump pressure was associated with an attempt to release the liner hanger running tool (RT) in the well, which had been obstructed. Improper setting of the liner hanger could have caused the forces from the RT release to be transferred to the liner and might have resulted in ripping and parting of the pipe. The possible direct impact of the ripped liner with the formation or the likely sudden hydraulic pressure exposure to the formation caused by the liner ripping may explain the estimated isotropic component in the moment tensor inversion in the well. This impact can promote slip along the pre-existing fractures (the DC component). The presence of gas in the formation or the funneled fluid to the formation caused by the liner ripping may explain the CLVD component.

A new lesser metatarsophalangeal joint replacement arthroplasty design - in vitro and cadaver studies

BackgroundIsolated degenerative joint disease and/or Freiberg’s infraction of the lesser metatarsophalangeal joint, although not frequent may become debilitating in the younger individual. Currently, once conservative management fails, the mainstay of treatment is debridement and excision-interposition arthroplasty. Replacement arthroplasty has been ineffective in the long term as the joints are subject to severe repetitive fatigue loading over small articulating surfaces through a wide range of motion. This is an in vitro and cadaver study of a new design replacement arthroplasty developed by the senior author.The aim of this study is to evaluate this novel replacement arthroplasty of the lesser metatarsophalangeal joint in a laboratory setting and cadaver implantation.MethodsThis three-component mobile bearing device is made of titanium and high density polyethylene which evolved over 4 years. It was subjected to 5,000,000 cycles in a laboratory under physiological and excessive forces to assess resistance to fatigue failure and wear pattern of the polyethylene liner. Following these tests, it was implanted in 15 fresh frozen cadavers at various stages of its development, during which the surgical technique was perfected. Range of motion and stability was tested using custom made instrumentation in four cadavers. The implant was inserted in a further two cadavers by an independent foot and ankle surgeon to check reproducibility.ResultsThe device showed almost no signs of wear or surface deformation under physiological forces. The surgical technique was found to be simple and reproducible in the cadaver trial.The average dorsiflexion was 28.5° and 28.9° pre- and post-implant respectively. The average plantar flexion was 33.8° and 20.8° pre- and post- implant respectively. The joints were stable both pre- and post-operatively. Post-operative stability was objectively assessed for dorsal displacement and dorsiflexion using a 5 kgf (49 N) and was found to be excellent.ConclusionThis novel lesser metatarsophalangeal joint replacement arthroplasty has been developed as an option in the surgical treatment of symptomatic degenerative joint disease and/or Freiberg’s infraction resistant to conservative treatment. The implant was found to be durable and resistant to wear in the laboratory testing. The cadaver studies have shown it to require minimal specialized instrumentation with good surgical reproducibility.This proof of concept study is the basis for clinical trials.

Improvement of loads calculation of the perforated liner in a geothermal production well

The integrity of perforated liners is crucial in geothermal production wells and this should be well designed according to correct standards. The available geothermal standards, such as the New Zealand Standard, NZS2403:2015, provides a general but less detailed discussion of geothermal perforated liner system design considerations.This research aimed to improve the limitations of NZS2403:2015 by calculating and evaluating the dynamic loads of perforated liner during four phases: borehole drilling and liner installation, flow testing, stand-alone production, and production during the injection operation. The data from production well HCE29 and injection well HCE29A, Dieng Field, Indonesia, were used in this research. In every phase, perforated liner yield strength changed, and load mechanisms varied between 1.3-2.7 and 1.6–4.6 times of the actual liner burst and collapse strength, respectively, and these lead to perforated liner failure and its lifetime reduction. The calculation results, combined with the significant production decline and production casing failure, indicated the perforated liner failure. The results also showed when it was mandatory to revise operation at later phases and to conduct appropriate maintenance according to actual perforated liner condition. Furthermore, this study can be used as a basis of future wells design and operation related to perforated liner.

Ceramic-on-ceramic catastrophic liner failure in total hip arthroplasty: Morphological and compositional analysis of fractured ceramic components

Surface bearing of total hip arthroplasty (THA) still is a strong subject of study due to the relatively high rate of failures caused by a multiplicity of factors including surgical technique, patient's attitude, and type/characteristics of the materials used (metal, ceramics, polyethylene) with their specific risk factors. Fractures of the ceramic components are rare but catastrophic events, with many concerns among the orthopaedic surgeons. Such complication is usually evaluated from a clinical viewpoint; this study provides a materials scientist's complementary perspective and comprehensively evaluates the surface and the mechanism of rupture of the ceramic liner in two cases with different ceramics (Biolox Forte and Biolox Delta) after ceramic-on-ceramic THA. The morphological and compositional analyses of the ceramic components were performed by field-emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS), along with macroscopic pictures. The SEM analysis of the ceramic liner showed many wear signs in all directions, while the EDS revealed the presence of titanium near to the fracture border, which might be interpreted as a consequence of the catastrophic contact between ceramic liner and metal back. Biolox Delta and Biolox Forte ceramic liners showed different patterns of fracture and surface modifications that are illustrated and discussed.