Large Diameter Metal Research Articles

O113 ELEVATED METAL ION LEVELS CAN BE TOLERATED BY SOME PATIENTS

Abstract Introduction Ten years following withdrawal and revision of large diameter metal on metal hips (MOM), there remains an uncertainty in how best to manage asymptomatic patients with abnormal imaging and/or raised blood metal ion levels. This study investigates the trajectories of symptoms, serological metal ion tests and cross-sectional imaging in these patients. Methods 523 patients with 707 acceptable functioning MOM hips (defined as Oxford Hip Score (OHS) >30) on active monitoring were identified. Surveillance at two time intervals included: patient-reported pain and function (OHS), blood metal ion (Cobalt (Col) and Chromium (Chr)) and/or cross-sectional imaging with MRI. Results Mean serum metal ion levels in parts per billion (ppb) were Co1 4.5 (S.D. 11.5), Co2 4.7 (S.D. 11.6) and Ch1 3.0 (S.D. 4.8) and Ch2 3.2 (S.D. 4.9). Median OHS was 42 (IQR 28–27). OHS was not significantly correlated to serum metal ion levels (Col Pearson correlation = -0.105 P = 0.106, Chr Pearson correlation = -.125 P = 0.054). There was no significant change in Col (-0.48, P = 0.414) and Chr levels (-0.25, P = 0.325) between the two time intervals. 45 patients had metal ion levels >7 ppb, 64.4% had OHS >30. 6 patients had metal ions level greater than 50 ppb, with no significant deterioration of OHS. Conclusion Our results indicate that there are a subset of patients with high metal ion levels, stable imaging and acceptable function who can safely be actively monitored thereby assisting in joint decision making with this challenging patient group.

Large-diameter metal matrix composite lattice truss sandwich cylinder: Additive manufacturing, testing and analyzing

Large-scale additively manufactured (AM) metal matrix composite (MMC) lattice truss sandwich cylinders (LTSCs) have impending application in launch vehicle systems as ultra-light load-carrying structures capable of realizing one-piece molding and facilitating multi-function. The critical load of the cylinders, which are interstage structures that are greatly affected by buckling mode, is the most important indicator in the design phase. This paper describes the design, fabrication, testing and analyses of a metallic AM LTSC. To predict the failure load and pattern of the LTSC, an elastoplastic multi-failure analyzing method is proposed. The results give insights in the practical application of large-scale AM LTSCs in aerospace engineering when compared to widely studied carbon fiber reinforced composite LTSCs.

Ultimate Bearing Capacity Analysis of Pile Caps with New Socket Connections

Socket connection need a groove reserved in the cap to accommodate a bridge pier, which greatly weaken the vertical bearing capacity of the cap. The conventional treatment measure is to increase the thickness of the cap, and the corresponding cost will increase. The measures to enhance the vertical bearing capacity of socket caps without increasing the thickness of the cap were discussed in this paper, including a rough interface at the bottom of the pier, additional hanging bars, high-strength grouting material in the seam, and large-diameter metal corrugated pipes, etc. Based on a previous test, the finite element analysis of the vertical bearing capacity of pile caps with new socket connections was carried out. The analysis parameters included the construction method, steel bar diameter in the bottom of the cap, socket depth, thickness of the bottom plate, pile length, and friction coefficient, etc. The bearing capacity M–N relation of the full-scale model was also analyzed. Research indicated the vertical bearing capacity of the cap is mainly provided by rough interfaces, the bottom plate, and the additional hanging bars, and the contribution of the three parts was about 40%, 34%, and 26%; the vertical bearing capacity was proportional to the areas of steel bars on the cap and the thickness of the bottom plate, and was inversely proportional to the length of the pile. To obtain the vertical bearing capacity of the overall cast-in-place plan for the socket cap, the thickness of the cap needs to be increased by 27%. At last, a design formula for the calculation of the vertical bearing capacity was proposed.

Electromagnetic Feet With Soft Toes for Adaptive, Versatile, and Stable Locomotion of an Inchworm-Inspired Pipe Crawling Robot.

Feet play an important role in the adaptive, versatile, and stable locomotion of legged creatures. Accordingly, several robotic research studies have used biological feet as the inspiration for the design of robot feet in traversing complex terrains. However, so far, no robot feet can allow legged robots to adaptively, versatilely, and robustly crawl on various curved metal pipes, including flat surfaces for pipe inspection. To address this issue, we propose here a novel hybrid rigid-soft robot-foot design inspired by the leg morphology of an inchworm. The foot consists of a rigid section with an electromagnet and a soft toe covering for enhanced adhesion to a metal pipe. Finite element analysis , performed under different loading conditions, reveals that due to its compliance, the soft toe can undergo recoverable deformation with adaptability to various curved metal pipes and plain metal surfaces. We have successfully implemented electromagnetic feet with soft toes (EROFT) on an inchworm-inspired pipe crawling robot for adaptive, versatile, and stable locomotion. Foot-to-surface adaptability is provided by the inherent elasticity of the soft toe, making the robot a versatile and stable metal pipe crawler. Experiments show that the robot crawling success rate reaches 100% on large diameter metal pipes. The proposed hybrid rigid-soft feet (i.e., electromagnetic feet with soft toes) can solve the problem of continuous surface adaptation for the robot in a stable and efficient manner, irrespective of the surface curvature, without the need to manually change the robot feet for specific surfaces. To this end, the foot development enables the robot to meet a set of deployment requirements on large oil and gas pipelines for potential use in inspecting various faults and leakages.

Through-Process Finite Element Modeling for Warm Flanging Process of Large-Diameter Aluminum Alloy Shell of Gas Insulated (Metal-Enclosed) Switchgear.

The large diameter metal shell component (LDMSC) is an important part of gas insulated (metal-enclosed) switchgear (GIS). The LDMSC with multi branches is filled with gas under certain pressure. The plastic forming process is an efficient approach to manufacturing the high reliability LDMSC. The warm flanging process has been widely used to form LDMSC using aluminum alloy. The forming process is characterized by local heating, and the distribution of temperature is strongly inhomogeneous. Although the wall thickness of the shell is 10 mm to 20 mm, the ratio of outer diameter to thickness is more than 40. These present some difficulties in the flanging process and result in some forming defects. Detailed forming characteristics are hard to obtain by analytical and experimental methods. Thus, the through-process finite element (FE) modeling considering heating, forming, unloading, and cooling is one of the key problems to research the manufacturing process of LDMSC. In this study, the through-process FE modeling of the warm flanging process of LDMSC using aluminum alloy was carried out based on the FORGE. The thermo-mechanical coupled finite element method was adopted in the modeling, and the deformation of the workpiece and the die stress were considered together in the modeling. A full three-dimensional (3D) geometry was modeled due to inhomogeneous distribution in all directions for the temperature field. The simulation data of local flame heating could be transferred seamlessly to the simulations of the deforming process, the unloading process, and the cooling process in the through-process FE model. The model was validated by comparison with geometric shapes and forming defects obtained from the experiment. The developed FE model could describe the inhomogeneous temperature field along circumferential, radial, and axial directions for the formed branch as well as the deformation characteristic and the unloading behavior during the warm flanging process. By using the FE model, the forming defects during the flanging process and their controlling characteristics were explored, the evolution of the temperature field through the whole process was studied, and deformation and springback characteristics were analyzed. The results of this study provide a basis for investigating deformation mechanisms, optimizing processes, and determining parameters in the warm flanging process of a large-diameter aluminum alloy shell component.

Consequences Following Distal Femoral Growth Plate Violation in an Ovine Model With an Intramedullary Implant: A Pilot Study.

Retrograde femoral nailing in skeletal immature patients would broaden the surgical options for fracture care and reconstructive procedures but involves violation of the open, active distal femoral physis with the potential for growth disturbance. The tolerance for putting a large diameter metal implant across the physis is largely unknown. The purpose of this pilot investigation was to define the upper limit of cross-sectional violation with a metal implant before causing premature growth arrest or inhibition using a sheep model. Eighteen sheep underwent placement of a retrograde, intramedullary implant at 3-months of age through an open distal femoral physis. The cross-sectional area of the physis was measured preoperatively and implants were selected that violated 3% to 8% of the cross-sectional area of the physis. Growth across the distal femoral physis was examined radiographically following surgery. Following euthanasia, both operative and no operative femurs were removed to compare differences in maximal lengths. The distal femora grew an average of 10.6±2.2 mm radio graphically after implantation. When compared with control specimens, only operative specimens with 8% of physeal violation demonstrated significant growth discrepancy with operative femurs measuring <2.1 mm in length compared with the contralateral control femur. Histologic analysis did not demonstrate any significant physeal bars formation. Distal femoral growth continues across the physis when 3% to 7% of the cross-sectional area of the physis is violated using a retrograde intramedullary implant. Specimens with 8% of growth violation demonstrated significant growth inhibition. As such, retrograde nailing through the distal femoral physis appears safe up to 7%. On the basis of previous anatomic data in humans and average nail sizes, violations of >6% of the physis with pediatric retrograde nailing would be uncommon. These findings suggest that retrograde nailing may be a viable option and merits further study. Level IV-case series.

Combined strengthening treatment of welded joints of metal pipes of large diameter

This article describes a method and device for the combined hardening treatment of welded joints of large diameter metal pipes, which allow to increase their strength and corrosion resistance due to the wave effect on the weld joint of the hardening tool and feeding the suspension into the working area without disturbing the overall process of welding pipes.

Dielectric Barrier Discharge Plasma Actuator Thrust Measurement Methodology Incorporating Antithrust Hypothesis

The thrust of the dielectric barrier discharge plasma actuator is the plasma body force minus the wall shear force, and it equals the net induced momentum. Thrust measurement simplicity makes it a good metric of the aerodynamic performance for active flow control applications. Uncertainty and non-repeatability issues with conventional test setups motivated development of a novel suspended actuator test setup and a measurement methodology consisting of a burn-in procedure followed by frequency scans at constant voltages. This approach led to observation of negative values of thrust, or “antithrust,” at low frequencies between 4 Hz and up to 64 Hz. The antithrust is proportional to the mean-squared voltage and is frequency independent. Departures from the parabolic antithrust curve are correlated with appearance of visible plasma discharges. The antithrust hypothesis is proposed. It states that the measured thrust is the sum of plasma thrust and antithrust. The magnitude of the antithrust depends on the actuator geometry, the materials, and the test installation. The dependence on test installation was validated by surrounding the actuator with a grounded large-diameter metal sleeve. A thrust data correction for antithrust enables meaningful comparisons between actuators at different installations. A strong dependence on humidity is also shown. The thrust significantly decreases with increasing humidity.

Оценка влияния трубного передела на свойства металла труб большого диаметра класса прочности К56

Оценка влияния трубного передела на свойства металла труб большого диаметра класса прочности К56

EUS-guided drainage for pancreatic walled-off necrosis by use of a novel large-diameter metal stent

EUS-guided drainage for pancreatic walled-off necrosis by use of a novel large-diameter metal stent

EUS-guided drainage for pancreatic walled-off necrosis by use of anovel large-diameter metal stent.

EUS-guided drainage for pancreatic walled-off necrosis by use of anovel large-diameter metal stent.

Our Experience with Short Stem Hip Replacement Surgery

Context-A short anatomical metaphyseal femoral stem is a desirable hip implant for bone and soft tissue preserving hip replacing surgery in young arthritic patients. Physiological loading of the proximal femur prevents stress shielding and preserves bone stock of the femur in the long run. Thus it is an ideal hip implant suited for conservative hip surgeries in active young adults with arthritic hips.Materials and methods-50 Proxima hip replacements were performed on 41 patients with a mean age of 45 over a 3-year period (between July 2006 and September 2009). Diagnosis of hip pathologies varied from osteoarthritis secondary to avascular necrosis, rheumatoid arthritis, post-tubercular arthritis to dysplastic hips. 9 of these patients had symptomatic bilateral hip involvement and underwent bilateral hip replacement in a single sitting. All patient had a Proxima metaphyseal stem implantation( DePuy, Warsaw) with either a large diameter metal on metal or pinnacle articulation. Clinical and radiological evaluation was done at 3 months, 6 months, 1 year and then yearly thereafter.Statiscal analysis used-VAS and Harris hip score formed the basis of evaluationResults-These patients were followed up for a mean period of 49 months (Range 36-72 months). The average incision size was 14.38 cm (10-18 cm) and blood loss was 269 ml (175-450 ml). There was no peri-operative mortality or serious morbidity in any patients. One patient had an intraoperative lateral cortex crack that required only delayed rehabilitation. Five of the 41 patients (12.1 %) had complications with three recovering completely and one requiring revision of femoral stem for aseptic loosening. One patient was lost in follow-up. Harris hip score improved from 52 to 89.3 at last follow-up. Overall 95.1% (39/41) patients had an excellent outcome at last follow-up.Conclusion-We conclude that Proxima metaphyseal stem provided clinically and radiologically stable fixation through snug fit initially followed by bone in-growth and was ideally suited to satisfy the requirements of a conservative hip implant. Unfortunately, due to unknown reasons, the implant has been recently withdrawn from the market by DePuy and is no longer available for use.Key MessageConservative hip stems that preserve bone and soft tissue at the time of surgery, prevent femoral stress shielding by circumferential loading, promote positive bone remodeling and help to make revision surgeries easier are ideally suited as hip implants for young active adults with end stage hip disease requiring hip replacement surgery.

PTU-002 EUS-Guided Insertion of Fully Covered Self-Expandable Metal Stents for Drainage of Pancreatic Walled-Off Necrosis Does Not Require Fluoroscopy

Introduction Transgastric placement of specially designed fully covered self-expandable metal stent (FCSMS) has improved the management and the outcome of walled-off necrosis (WON) after severe pancreatitis. Reduction of radiation exposure is of increasing importance. Therefore, we investigated whether transgastric insertion of FCMS for drainage of WON is possible only by EUS-guidance. Methods Patients with symptomatic pancreatic walled-off necrosis referred for endoscopic drainage were included. EUS-guided stent insertion was performed under concious sedation or endotracheal intubation. The pancreatic collection was accessed from the stomach using a linear echoendoscope with a 19 G access needle, a cystotome or directly using the hot Axios® device. After insertion of a guidewire and enlargement of the transgastric access by diathermy a fully covered self-expandable metal stent was inserted under EUS guidance without fluoroscopy. As clinically indicated, endoscopic necrosectomy was performed through the large diameter metal stent. When the collection had shrunk to less than 4 cm, symptoms and inflammatory parametrs had improved, the stent was endoscopically removed. Results 18 patients (median age: 55 years; range 48–63 years) with symptomatic WON (median diameter: 14 cm; range 8–18 cm) were referred for EUS-guided drainage. In 2 patients large traversing arteries within the cavity were detected by colour Doppler imaging during EUS, therefore the insertion of FCSMS was not attempted to avoid possible erosion of the vessels by the stent edges with reducing collection size. In all other patients (88.9%) the completely EUS-guided transgastric stent insertion without fluoroscopy was technically successful (6 AXIOS® and 10 Nagi® stents were inserted). The stent insertion into the cavity and the opening of the distal flange could be clearly visualised by EUS in all cases. After correct positioning of the FCSMS by EUS the proximal stent flange was deployed under endoscopic guidance. Two patients were readmitted with fever when the stent was blocked with debris. Seven patients required endoscopic necrosectomy through the FCSMS. One patient developed self-limiting bleeding. WON resolved in all patients within 8 weeks. Conclusion The good sonographic visibility of the FCSMS throughout the procedure allows safe and easy insertion of transgastric drainage under EUS-guidance without fluoroscopy. Reference 1 Seifert H, Wehrmann T, Schmitt T, Zeuzem S, Caspary WF. Retroperito-neal endoscopic debridement for infected peripancreatic necrosis. Lancet 2000; 356:653–5. Disclosure of Interest None Declared

ANATOMICAL LARGE FEMORAL HEADS: EARLY COMPLICATIONS AND MID TERM RESULTS

Purpose: mechanical complications such as malrestoration of hip anatomy still impede surgical results and patient satisfaction after THA. Anatomical femoral «mega-heads» are a novel approach which enables a surgeon to use a large diameter metal on metal implant to restore hip anatomy. Ability to place femoral head eccentrically on the femoral taper results in possible anteversion, retroversion, offset and lengthening. Our hypothesis is that use of this device will result in more accurate anatomical restoration and clinical results. Methods: 64 anatomical mega-head arthroplasties were evaluated. Preoperative planning was done in order to determine the desired position of the head, restore the anatomy and avoid leg lengthening. Patients were observed at an average of 50-months for both subjective and objective outcomes. Radiograph analysis assessed anatomical restoration. Results: 51 of the 64 hips were available for follow up. In 35 the head was placed eccentrically. In 20 the positioning was inferior, 6 — posterior, 3 — anterior, 1 — superior, and 4 inferior and posterior. Harris Hip and SF-36 scores improved significantly (P < 0.001). Mean radiographic limb and offset discrepancy were 0.1 and 0.01mm respectively. Six patients (11.7 %) underwent revision surgery; elevated metal ion levels and pseudotumor (3), acetabular component loosening (2), and unexplained hip pain (1). Conclusions: The novel anatomical femoral mega-head allows versatility in restoration of normal hip anatomy. Mid-term follow-up showed a higher than anticipated rate of complications for this cup design and reduced longevity of the implant. Novel ways need to be explored to allow such versatility in restoring hip anatomy.

Chromium nitride coating for large diameter metal-on-polyethylene hip bearings under extreme adverse hip simulator conditions

Large diameter total hip replacements using polyethylene liners have been proposed due to low wear and oxidative stability observed in the latest generation of this material. Concerns exist with large diameter metal bearing surfaces and ceramic heads are generally expensive to manufacture. A ceramic chromium nitride (CrN) coating on a metal head may be an alternative bearing surface, maintaining low polyethylene wear and minimising cobalt release. Vitamin-E blended highly crosslinked polyethylene liners (52mm diameter) paired with electron beam physical vapour deposited (EBPVD) CrN coated and uncoated CoCrMo heads were tested in a hip simulator. Under standard conditions no difference was observed in polyethylene wear rates (9.2 and 9.5mm3/mc) but the coating prevented cobalt release. Alumina particles produced substantial damage on the uncoated heads but did not damage the coated heads. Further testing without abrasive particles increased the polyethylene wear (469mm3/mc) and cobalt release (847ppb/mc) in the uncoated bearings yet remained low in the coated components (13mm3/mc wear, 17ppb/mc cobalt). Additionally, the coating reduced the generation of nanometre sized polyethylene particles by an order of magnitude under all adverse test conditions. This CrN coating may have the potential to reduce clinical wear allowing for large diameter components.

2D measurements of cup orientation are less reliable than 3D measurements

Background and purpose — 2D analysis of metal-on-metal (MoM) hip arthroplasty (HA) has been conducted in several large series on conventional radiographs with the use of Ein Bild Roentegen Analyse (EBRA) software, but there have been no comparisons with 3D analysis in the literature. The main aim of this study was to quantify the agreement in measurements of cup version of large-diameter MoM hips obtained by EBRA and by 3D computed tomography (3D-CT). The secondary aim was to quantify the agreement for cup inclination. Lastly, we wanted to determine the inter- and intra-observer reliability of both methods.Patients and methods — 87 MoM hips in 81 patients were analyzed for cup inclination and version in 2D on conventional radiographs using EBRA software. The results were compared with 3D measurements using CT.Results — Cup version was underestimated by EBRA when compared to 3D-CT, by 6° on average with the pelvis supine and by 8° on average with the pelvis orientated to the anterior pelvic plane (APP). For inclination, the mean difference was no more than 1°. 53% of hips were within a 10° safe zone of 45° inclination and 20° version when measured by 3D-CT with the pelvis supine (and 54% with the pelvis in the APP). The proportion was only 24% when measured by EBRA. Inter- and intra-observer reliability of cup version is poorer using 2D analysis than when using 3D-CT.Interpretation — Errors in version in 2D were due to the difficulty in delineating the cup rim, which was obscured by a large-diameter metal head of the same radio-opacity. This can be overcome with 3D analysis. The present study demonstrates that measurements using EBRA have poor agreement and are less reliable than those with 3D-CT when measuring cup version and inclination in MoM hips.

Characterisation of the oxide film on the taper interface from retrieved large diameter metal on polymer modular total hip replacements

Many metal joint failures have been associated with adverse local tissue reactions due to the response of the body to wear debris and corrosion products, released from the bearing surfaces or the taper interfaces. The oxide film on the CoCrMo plays an important role in the electrochemical behaviour, however, there is a lack of quantitative data on the structure and distribution of oxides following in vivo operation. In the present study, detailed analysis of the surface layer on the taper interfaces is provided. Two retrieved taper interfaces were analysed. Site-specific FIB/TEM cross-sections show evidence of the oxide film and the carbonaceous layer. High resolution TEM results show the oxide film has porous texture and EELS confirmed it is chromium oxide.

Large diameter metal on metal total hip replacement for femoral neck fractures with neurological conditions: A retrospective assessment.

Background:Patients with Parkinson's disease and poliomyelitis can have a femoral neck fracture; yet, the optimal methods of treatment for these hips remains controversial. Many constrained or semi-constrained prostheses, using constrained liners (CLs) with a locking mechanism to capture the femoral head, were used to treat femoral neck fractures in patients with neurological disorders. We retrospectively studied a group of patients with Parkinson's disease and poliomyelitis who sustained femoral neck fractures and were treated by total hip arthroplasty using an L-MoM prosthesis.Materials and Methods:We retrospectively reviewed 12 hips in 12 patients who underwent large-diameter metal-on-metal (L-MoM) total hip replacement between May 2007 and October 2009. Eight of the 12 patients (8 hips; 66.7%) had Parkinson's disease and 4 patients (4 hips; 33.3%) were affected with poliomyelitis.Results:The followup time was 5.2 years (range 3.6-6.0 years). At the latest followup, all the patients showed satisfactory clinical and radiographic results, with pain relief. No complications, such as dislocation or aseptic loosening occurred.Conclusion:We believe the use of L-MoM can diminish the rate of instability or dislocation, after operation. The L-MoM is an option for patients with Parkinson's disease and poliomyelitis with femoral neck fracture.

Technical Tip

We describe a salvage revision technique used in a patient with a painful metal-on-metal hip replacement, with local soft tissue swelling, lymphadenopathy, and elevated cobalt and chromium ions (Co 4.1 ppb and Cr 4.2 ppb). Cementing a polyethylene liner into an acetabular shell or cage is not new but, to date, there are no reports of cementing into a low-friction large-diameter metal bearing. Pull-out testing after roughening the highly polished cobalt chrome surface using a carbide burr increased pull-out strength from 1179 to 3500 N, equivalent to existing cement-in techniques. Following revision, metal ions returned to normal, hip function improved, and at 2 years’ follow-up there was no evidence of loosening. This is a promising technique for revision hip surgeons in select patients.

Interventional endoscopy for the treatment of pancreatic pseudocyst and walled-off necrosis (with videos).

Pancreatic pseudocysts and walled-off necrosis are typical late complications of acute pancreatitis, and they require drainage in symptomatic cases presenting with infection. Transgastrointestinal endoscopic treatment with endoscopic ultrasound-guided drainage has become common and yields a good treatment outcome for pancreatic pseudocyst. Walled-off necrosis, however, contains necrotic tissue, and thus many cases additionally require an invasive treatment that includes endoscopic necrosectomy. Methods that involve a procedure-specific large-diameter metal stent, additional endoscopic drainage techniques, and the hybrid approach method of adding percutaneous drainage have been described, and considerable advances in these methods have now made it possible to cure almost all cases of walled-off necrosis with endoscopic treatment alone. However, without being restricted to endoscopic treatments, a wide range of options including surgery should be considered as treatments for walled-off necrosis.