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Study Design: Analysis of explanted MAGnetic Expansion Control (MAGEC) growing rods.Objective: The aim of this study was to quantify the rate of locking pin breakage in explanted MAGEC rods and compare with the manufacturer's data.Summary Of Background Data: On June 25, 2019, NuVasive released an Urgent Field Safety Notice stating that MAGEC rods manufactured before March 26, 2015 had a higher than expected locking pin breakage rate of 5%. For rods made on or after that date, no pin breakages had occurred.Methods: From our independent explant database of 139 explanted MAGEC rods supplied from 10 UK spinal centers (Belfast, Bristol, Birmingham, Edinburgh, Exeter, Leeds, Newcastle, Nottingham, Oxford, and Sheffield) and one Danish center (Aarhus), we divided the rods into those manufactured before March 26, 2015, and those manufactured on or after that date. MAGEC rods were cut open to fully assess internal components including locking pins. From each of the two cohorts, 10 locking pins were selected at random and their diameters were measured using a micrometer.Results: One hundred and five explanted MAGEC rods were made before March 26, 2015 and could be disassembled to allow the locking pin to be examined. Fifty-nine percent (62/105) of these locking pins had fractured. For the MAGEC rods manufactured on or after March 26, 2015, 21% (6/29) were found to have fractured locking pins. Locking pins in MAGEC rods made on or after March 26, 2015 were of a stronger material and a larger diameter.Conclusion: Fifty-nine percent of the locking pins in MAGEC rods manufactured before March 26, 2015 had fractured, far greater than the 5% stated in the Urgent Field Safety Notice. Locking pin fracture still occurred in MAGEC rods manufactured on or after that date, in 21% of cases. This contrasted with the 0% reported by the manufacturer.Level Of Evidence: 4. [ABSTRACT FROM AUTHOR]

Study Design: Analysis of explanted MAGnetic Expansion Control (MAGEC) growing rods.Objective: To analyze explanted MAGEC rods used in management of early onset scoliosis and identify the mode of failure in such cases.Summary Of Background Data: Magnetically controlled growing rods are increasingly used as the option of choice for early onset scoliosis. However, being more complex than conventional growing rods they are perhaps more likely to succumb to multifarious failure modes. In addition, metallosis has been reported around failed MAGEC rods.Methods: Explanted MAGEC rods from seven UK spinal centers were obtained for independent analysis. Thirty-four MAGEC rods, from 18 children, explanted for reasons including failure of rod lengthening and maximum rod distraction reached, were cut open to allow internal components to be evaluated and assessed.Results: Externally, all MAGEC rods showed localized marks, which were termed "growth marks" as they indicated growth of the rod in vivo, on the extending bar component. After cutting open, titanium wear debris was found inside all 34 (100%) MAGEC rods. Ninety-one percent (31/34) of MAGEC rods showed measurable wear of the extending bar, towards the magnet end. Substantial damage to the radial bearing was seen inside 74% (25/34) of MAGEC rods while O-ring seal failure was seen in 53% (18/34) of cases. In 44% (15/34) of MAGEC rods the drive pin was fractured but this was felt to be an effect of rod failure, not a cause.Conclusion: The combination of high volumes of titanium wear debris alongside O-ring seal damage likely accounts for the metallosis reported clinically around some MAGEC rods. Based on this explant data, a failure mechanism in MAGEC rods due to the natural off axis loading in the spine was proposed. This is the largest data set reporting a complete analysis of explanted MAGEC rods to date.Level Of Evidence: 4. [ABSTRACT FROM AUTHOR]

Bioengineering is a multidisciplinary science which requires mechanical engineering students, who typically have minimal knowledge of medicine, to rapidly gain a thorough understanding of the intricacies of human anatomy as well as of the specialist terminology. Teaching on a bioengineering module in a school of mechanical engineering at a UK university employed a combination of Primal Pictures anatomical software, human joint models, bespoke teaching materials and peer-to-peer learning. This mixture allowed engineering students to quickly construct an understanding of anatomical principles which they used in individual, assessed projects on total joint replacement. Anonymised, written feedback collected from the students over consecutive academic years revealed overwhelmingly positive learning experiences. In addition, assessed projects showed good knowledge of the anatomical descriptions necessary to understand and work with the science of joint replacement. [ABSTRACT FROM AUTHOR]

Abstract: One of the claimed advantages of metal-on-metal total hip replacements is that they ‘self-polish’ in the body, however this assertion has not been supported by quantitative data. Two pairs of components, each consisting of a femoral head and acetabular cup, were obtained at revision surgery. They were subject to topographical analysis using a non-contacting profilometer. In the ‘worn’ regions a reduction in surface roughness was seen alongside a change in skewness values from positive to negative, while elastohydrodynamic theory suggested an improvement towards mild mixed lubrication during gait. Therefore self-polishing of metal-on-metal total hip replacements can occur in vivo. [Copyright &y& Elsevier]

Abstract: Due to their recent introduction there are few studies of retrieved resurfacing hip prostheses. Nine such components associated with groin pain in patients, and five associated with early fracture of the femur, were obtained and analysed using a roundness measuring machine. While the ‘fracture’ components showed no more than 3μm out of roundness, components associated with groin pain showed between 15 and 92μm out of roundness values. These latter results indicate wear and correlated with high metal ion levels in these patients, therefore the groin pain was likely associated with an adverse reaction to excessive metal wear debris. [Copyright &y& Elsevier]

Abstract: Various designs of two-piece finger prosthesis with conforming spherical surfaces have been proposed. These were compared by calculating the lubrication regime for the material combinations and operating conditions expected at the metacarpophalangeal joints of the fingers. Consideration was given to a range of loads from 2 to 50N, a range of entraining velocities from 0 to 30mm/s, and a range of prosthesis radii from 3 to 10mm. This theoretical lubrication analysis indicated that the optimum material combination of those available for two-piece metacarpophalangeal prostheses is in the order: ceramic-on-ceramic; metal-on-metal; pyrocarbon-on-pyrocarbon; and metal-on-polymer. However, it should be recognised that other factors may take precedence when choosing a material combination for a design of finger prosthesis. [Copyright &y& Elsevier]

• Fractography of explanted spinal rods illustrate multiple failure mechanisms. • Evidence of corrosion recognises that the pins have snapped long before explantation. • Failure modes illustrates the complexity of loading in spinal growing rods. The MAGnetic Expansion Control (MAGEC) spinal implant has transformed the treatment of early-onset scoliosis (i.e. abnormal curvature of the spine in children). Despite the innovative solution, the MAGEC device has encountered various performance issues. One component that has been frequently reported amongst the failure issues is the drive pin and the cause of these reoccurring fractures may be associated with multiple factors including over-loading, fatigue, and corrosion. This study aimed to examine the failure of eight broken drive pins from explanted MAGEC rods through fractography analysis, to better understand the factors leading to their fracture. The fracture surface of the drive pins was examined using Scanning Electron Microscopy (SEM). The clinical data were compared against observed failure modes. The fracture surfaces of four drive pins showed low cycle (high stress) or high cycle (low stress) fatigue failure mechanisms. The other four drive pins displayed environment assisted stress corrosion cracking. Almost all samples had evidence of corrosion after fracture with the amount of corrosion implying fracture occurred a relatively long time before explantation. Since multiple failure mechanisms of low cycle fatigue, high cycle fatigue or simultaneous effect of tension and corrosive environment have been observed, the fracture mechanisms illustrate the complexity of loading in these spinal growing rods. Evidence of corrosion after the failure recognises that the pins have snapped long before the device was explanted. [ABSTRACT FROM AUTHOR]

Background: During the twentieth century, hip replacement became one of the most popular and successful operations. In the 1990s, a new type of hip replacement namely the metal‐on‐metal hip resurfacing was developed. This paper draws on one of the available implants, namely the DePuy Orthopaedics' Articular Surface Replacement (ASR) hip system which was withdrawn from the market because of higher than expected rates of failure. It examines media representations on the failure of the ASR metal‐on‐metal hip replacement device and its subsequent withdrawal from the market. Methods: Drawing on content analysis this paper explores how systemic failure of the medical implant was framed and performed by press media in the UK. Results: Two narratives were particularly important in framing press media coverage of the ASR case: the role of patients as passive recipients of care and a distinction between health and disability identities as related to how individuals' narratives about the past shaped their sense of present and future. In all cases, the voice of the orthopaedic surgeons responsible for the selection and implantation of the ASR devices remains silent. Conclusions: Press media coverage of medically induced harm in the UK is significantly less common than coverage of any other patient safety issues and public health debates. This study aims to contribute to the evidence base on how public discourse on medically induced harm becomes framed through the reported experiences of individuals in press media and also how this process influences the legitimacy of various solutions to medical errors or unanticipated outcomes. [ABSTRACT FROM AUTHOR]

The generation of particulate debris at the taper junction of total hip replacements (THRs), can cause failure of the artificial hip. The taper surfaces of femoral heads and trunnions of femoral stems are generally machined to a certain roughness to enhance fixation. However, the effect of the surface roughness of these surfaces on the fixation, wear and consequently clinical outcomes of the design is largely unknown. In this study, we asked whether a micro-grooved trunnion surface finish (1) improves the fixation and (2) reduces the wear rate at the taper junction of THRs. We used 3D finite element (FE) models of THRs to, firstly, investigate the effect of initial fixation of a Cobalt-Chromium femoral head with a smooth taper surface mated with a Titanium (1) micro-grooved and (2) smooth, trunnion surface finishes. Secondly, we used a computational FE wear model to compare the wear evolution between the models, which was then validated against wear measurements of the taper surface of explanted femoral heads. The fixation at the taper junction was found to be better for the smooth couplings. Over a 7 million load cycle analysis in - silico , the linear wear depth and the total material loss was around 3.2 and 1.4 times higher for the femoral heads mated with micro-grooved trunnions. It was therefore concluded that smooth taper and trunnion surfaces will provide better fixation at the taper junction and reduce the volumetric wear rates. [ABSTRACT FROM AUTHOR]

Purpose: Determine the incidence of metallosis around MAGEC rods. Methods: A multicentre explant database was searched to identify cases with complete intraoperative findings at rod removal. Surgeons removing rods detailed the presence or absence of tissue metallosis associated with rods. More recently surgeons measured the 'length' of tissue metallosis. Prior to rod disassembly, the majority underwent testing with an external remote controller (ERC). The impact of clinical and explant variables on metallosis was assessed. Results: Sixty-six cases were identified. Mean age at insertion was 8.1 ± 2.3 years with mean duration of implantation 37.6 ± 15.1 months. Tissue metallosis was noted at revision surgery in 52/66 cases (79%). Metallosis was noted more commonly when rods were removed during fusion surgery than rod removal/exchange (97% vs. 58% (p = < 0.01)). The mass at insertion was greater in cases with metallosis (25.9 ± 7.8 kg vs. 21.1 ± 6.2 kg, p = 0.04). Length of tissue metallosis was reported for 45 rods, median 9 cm (range 1–25). Metallosis was noted in 43/59 (73%) rods that produced no force and 22/30 (73%) rods that produced some force on ERC activation (p = 0.96). Wear debris was found within the actuator in all rods, and all but 3 rods had damaged O-rings. Conclusion: MAGEC rods are associated with tissue metallosis in the majority of cases. It is seen with functional rods as well as failed rods and appears related to wear debris within the actuator and high rates of O-ring failure. Until the implications of metal debris in children are known, we urge caution with the use of this implant. [ABSTRACT FROM AUTHOR]

• This is the first reported explant analysis of a Mobi-C cervical disc. • It was shown that migration of the insert occurred, leading to compression of the spinal cord, pain and eventually a revision operation. • While they may provide more normal biomechanics, non-constrained designs, such as the Mobi-C, may also be associated with excessive migration of the insert in vivo. • In common with explanted metal-on-polymer joint replacements, the metal articulating surfaces of the disc became rougher while the polyethylene insert became smoother in vivo. Ex vivo analysis of artificial discs is essential to better understand their ability to replace degenerated intervertebral discs. The Mobi-C differs from some other contemporary disc designs in that it has a mobile polyethylene insert that is sandwiched between superior and inferior cobalt chromium endplates. While some studies claim the Mobi-C to have restored normal cervical spinal biomechanics, others have noted high levels of migration. Our objective was to contribute to this debate by, for the first time, analysing an explanted Mobi-C cervical disc which was removed due to worsening myelopathy at the nano and macro scales. Intraoperatively, the insert was found to have excessively migrated and it compressed the spinal cord. Roughness was measured as 0.016 ± 0.006 μm (Sa) and 0.055 ± 0.020 μm (Sa) for the superior and inferior plates, and 1.210 ± 0.154 μm (Sa) and 0.446 ± 0.083 μm (Sa) for the superior and inferior surfaces of the insert. Compared to unworn surfaces, the roughness increased for the superior and inferior plates and decreased for both surfaces of the insert. However, the only statistically significant change occurred on the articulating surface of the inferior plate (p = 0.04). At the nanoscale, valleys dominated the articulating surfaces. The superior plate had a burnished appearance whereas the inferior plate appeared matt. Impingement was observed on the endplates. The insert was severely damaged, burnished and had scratches. Additionally, subsurface whitening and internal cracking were observed on the insert. [ABSTRACT FROM AUTHOR]

Study Design: Laboratory analysis of explanted MAGnetic Expansion Control (MAGEC) rods.Objective: The aim of this study was to identify the in vivo lengthening of MAGEC rods.Summary Of Background Data: Little data is available regarding the lengthening achieved by MAGEC rods.Methods: Cases were identified from the largest series of independently analyzed explanted MAGEC rods. The in vivo growth of rods was determined by the distance between the first "growth mark" and the actuator. The instrumented spinal lengthening was calculated for each construct. Constructs were considered functional if all rods could lengthen with external remote controller activation and no rods were "telescoping".Results: Fifty-five MAGEC constructs (99 rods) from 53 patients treated at 10 centers were included. The mean age at insertion was 8.5 years with rods implanted a mean of 35 months. Sixty rods were suitable for analysis with mean lengthening 21.7 mm, 8.9 mm/year. Of these 60 rods, three were maximally distracted. Mean instrumented spinal lengthening for 38 suitable cases was 22.1 mm, 8.4 mm/year. This was positively correlated with the duration of implantation (r = 0.34, P = 0.04) but negatively with patient age at insertion (r = -0.35, P = 0.03). The rate of instrumented spinal lengthening was negatively correlated with duration of implantation (r = -0.47, P = 0.004). Of 55 constructs, 34 were nonfunctional at time of removal with nine functional and 12 indeterminate. Functional constructs had been implanted significantly less time (20.0 vs. 39.7 months, P < 0.001) and lengthened less than those nonfunctional (12.3 mm vs. 23.3 mm, P = 0.04).Conclusion: This multicenter explant study represents the largest cohort managed with MAGEC rods reported. Rods are very rarely removed having fully lengthened with mean instrumented spinal growth of 22 mm over the implant's life. This may be explained by a high rate of lengthening mechanism failure in received rods after around 3 years in vivo. Our findings question the effectiveness of the MAGEC system and mandate urgent comparative clinical studies.Level Of Evidence: 4. [ABSTRACT FROM AUTHOR]

Study Design: Laboratory analysis of explanted MAGnetic Expansion Control (MAGEC) growing rods.Objective: The aim of this study was to measure the force produced by explanted MAGEC rods compared with new rods and assess the influence of clinical variables.Summary Of Background Data: MAGEC rods are increasingly used in early-onset scoliosis. Some data are available describing the structure of explanted MAGEC rods, but to date, no study has assessed their function.Methods: Explanted MAGEC rods were received from seven UK and one Danish center. The force produced by explanted rods on activation with the external remote controller was measured using a dedicated jig. Forces were compared with two unused rods as well as the manufacturer's defined standard (42 Ibf). Clinical variables were collected from contributing centers where possible and correlated with the force measurements.Results: Forty-five MAGEC rods from 25 cases were received for analysis. The mean age at insertion was 8.6 years and rods were in vivo for a mean of 2.7 years in predominantly dual rod constructs. Two unused MAGEC rods produced a mean force of 45.3 (0.25) and 50.2 (1.4) Ibf, above the manufacturer's stated standard. Of the 45 explanted rods, 10 (22%) produced force greater or equal to manufacturer's standard, mean 46.7 (2.7) Ibf. Six rods (13%) produced some force but less than the manufacturer's standard, mean 34.8 (3.6) Ibf. Twenty-nine rods (64%) produced no force. The duration the rods were in vivo was significantly negatively correlated with the force produced on testing (r = -0.63, P < 0.005). Of the 12 rods implanted longer than 38 months, none produced any force.Conclusion: This is the first study of the force, and hence likely function, of explanted MAGEC rods. The majority of explanted rods produced no force, while others produced reduced force. These findings raise questions regarding the longevity of the implant and further clinical outcome studies are recommended.Level Of Evidence: 4. [ABSTRACT FROM AUTHOR]

It has been proposed that an increased surface roughness of the femoral components of Total Knee Replacements (TKRs) may be a contributing factor to the accelerated wear of the polyethylene (PE) bearing and ultimately prosthesis failure. Oxidised Zirconium was introduced to the orthopaedic market in an attempt to reduce PE wear associated failures and increase the longevity of the prosthesis. In this study, non-contacting profilometry was used to measure the surface roughness of the femoral components of 6 retrieved TKRs (3 Oxidised Zirconium (OxZr) and 3 Cobalt Chromium alloy (CoCr) femoral components) and 2 as-manufactured femoral components (1 OxZr and 1 CoCr). A semi-quantitative method was used to analyse the damage on the retrieved PE components. The S a values for the retrieved OxZr femoral components ( S a = 0.093 µm ± 0.014) and for the retrieved CoCr femoral components ( S a = 0.065 µm ± 0.005) were significantly greater ( p < .05) than the roughness values for the as-manufactured femoral components (OxZr S a = 0.061 µm ± 0.004 and CoCr S a = 0.042 µm ± 0.003). No significant difference was seen between the surface roughness parameters of the retrieved OxZr and retrieved CoCr femoral components. There was no difference between the PE component damage scores for the retrieved OxZr TKRs compared to the retrieved CoCr TKRs. These results agree with other studies that both OxZr and CoCr femoral components roughen during time in vivo but the lack of difference between the surface roughness measurements of the two materials is in contrast to previous topographical reports. Further analysis of retrieved OxZr TKRs is recommended so that a fuller appreciation of their benefits and limitations be obtained. [ABSTRACT FROM AUTHOR]

This paper discusses an interdisciplinary research project testing the efficiency of European Bronze Age axes through experiments with replica tools and the usewear analysis of prehistoric axe-heads from the collections of the Great North Museum, Newcastle upon Tyne (UK). The project explores whether changes in axe-head design and hafting arrangement from early to late Bronze Age might have been motivated by a desire to improve tool efficiency. The team, comprising researchers with backgrounds in archaeology, engineering, and statistical data modelling, carried out several field and laboratory tests to address the research problem. They subsequently validated the test results through the microscopic analysis of original Bronze Age axe-heads. The data suggest that hafting technology, and especially the resilience of the haft-blade assembly, is more important than axe-head design per se in determining the efficiency and working performance of Bronze Age axes. The research provides a fresh answer to a question rooted in 19th century archaeology and charts an innovative multidisciplinary pathway for studying human technology through the ages. • Axes changed their head designs and hafting technologies throughout the Bronze Age. • The resilience of the haft-blade assembly is more important than axe-head design per se in determining axe efficiency. • Experimental archaeology, usewear analysis, and tribology can be used to test the working parameters of ancient tools. • Statistical methods can be used to validate the results of these tests. [ABSTRACT FROM AUTHOR]