1,249 research outputs found

    Spatial Sensors for Quantitative Assessment of Retrieved Arthroplasty Bearings

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    Evaluation of retrieved joint arthroplasty bearings provides unique evidence related to the physiological environment in which bearing materials are expected to perform. This dissertation describes the development of novel spatial sensors and measurement strategies for standardized, quantitative assessments of arthroplasty bearings, including total knee replacements, unicompartmental knee replacements, and total hip replacements. The approach is to assess bearings that endured a finite duration of function in patients, with particular emphasis on expanding our understanding of the biomechanical conditions specific to bearing function and wear in the physiological environment. Several quantifiable parameters are identified that prove comparable to pre-clinical in vitro tibological evaluations, including knee wear simulation and analytical modeling. These comparisons provide clinical relevance to the existing methodologies, helping to verify that the biomechanical simulations accurately represent the in vivo conditions they are meant to simulate. The broad objective of this dissertation is to improve the longevity and function of arthroplasty bearing materials and designs. Assessments from the retrieved prostheses are discussed within the context of developing comprehensive approaches for the prospective evaluation of new materials and designs in joint replacements

    Failure of Primary Total Knee Arthroplasty: Establishing a Baseline for Retrieval Analysis Using Well-Functioning Necropsy Specimens

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    Introduction. Total knee arthroplasty (TKA) is an effective treatment for end-stage osteoarthritis of the knee. While many patients have positive functional and pain outcomes following primary TKA, a subset of patients have suboptimal outcomes, such as unexplained pain or aseptic loosening of the implant components necessitating revision of the index procedure. The understanding of the exact etiology of these suboptimal outcomes of primary TKA is in its infancy. In order to elucidate the etiology of failure in primary TKAs, a baseline for the factors contributing to arthroplasty failure and dissatisfaction must first be established. The purpose of this study was to investigate the relationship between soft tissue laxity, inflammatory cytokine concentrations, tissue metal concentrations, and wear scores of well-functioning implants retrieved from cadaveric specimens to determine the role of each of these factors in implant survivorship. It was hypothesized that decreased joint laxity would increase metal concentrations in the periprosthetic tissue, that cytokines specifically tied to the innate immune system would be elevated in laxer joints, and, lastly, that elevated inflammatory cytokines in the synovial fluid would be associated with elevated periprosthetic tissue metal concentrations. Methodology. A total of 33 cadaveric specimens with primary TKA were obtained from two sources, the Medical Education and Research Institute (Memphis, TN) and RestoreLife USA (Elizabethton, TN), as part of institution review board approved multi-institutional orthopaedic retrieval program. Prior to testing and retrieval, fluoroscopically-assisted radiographs were taken to assess if any evidence of radiolucencies were present and all replacements were determined to be well-fixed per the images. Synovial fluid was then aspirated from the joint, processed, and stored in a -80˚C freezer. Each specimen was mounted into a custom knee testing platform and the IE rotation, varus-valgus (VV) deflection, and AP translation was measured at 0˚, 30˚, 60˚, and 90˚ of flexion. After collection of the laxity data, tissue samples were collected from the supra- and infra-patellar regions, the medial and lateral gutter, and from the tibia. The polyethylene inserts were assessed for wear on the condylar, backside, and stabilizing post surfaces, when applicable, and the femoral condyle was assessed for damage. A bead-based multiplex assay using the Luminex MAGPIX platform (R&D Systems, Minneapolis, MN) was performed on the synovial aspirates for simultaneous detection of various inflammatory cytokines including: IL-1β, IL-6, MCP-1, and MIP-3α. Inductively coupled plasma mass spectrometry (ICP-MS) was performed at Brooks Applied Labs (Bothel, WA) on the periprosthetic tissue samples for determination of tissue cobalt (Co), chromium (Cr), and titanium (Ti) concentrations. Finally, statistical analysis was conducted using SigmaPlot (Systat Software, Chicago, IL) to elucidate whether any correlations existed between the aforementioned factors. Results. Decreased IE laxity at full extension was inversely correlated with increased Co concentrations in the periprosthetic tissues (ρ=-0.64, p=0.02) with a sample size (n) of 13 and a 95% confidence interval (CI) from -0.88 to -0.14. At 90° of flexion, anterior laxity was inversely correlated with Co concentrations (ρ=-0.66, p=0.03, n=11, 95% CI: -0.90 vi to -0.10). At 60° of flexion, anterior laxity was inversely correlated with Cr concentrations (ρ=-0.63, p=0.03, n=13, 95% CI: -0.88 to -0.12). Anterior laxity at 90° of flexion was also inversely correlated with Cr concentrations (ρ=-0.81, p=0.003, n=11, 95% CI: -0.95 to -0.41). Lastly, posterior laxity at 90° of flexion was inversely correlated with Cr concentrations in the periprosthetic tissues (ρ=-0.74, p=0.01, n=11, 95% CI: -0.93 to -0.25). At 60° of flexion, IE rotational laxity was inversely correlated with IL-1β concentrations (ρ=-0.55, p=0.02, n=18, 95% CI: -0.81 to -0.11). At 60° of flexion, VV laxity was inversely correlated with TNF-α concentrations (ρ=-0.78, p=2x10-4 , n=14, 95% CI -0.93 to -0.43). Additionally, VV laxity was inversely correlated with IL-1β concentrations (ρ=-0.48, p=0.04, n=18, 95% CI: -0.77 to -0.02) at 60° of flexion. At full extension, VV laxity was inversely correlated with IL-6 concentrations (ρ=-0.46, p=0.04, n=19, 95% CI: -0.76 to -0.01). Anterior laxity was directly correlated with IL-6 concentrations (ρ=0.53, p=0.02, n=18, 95% CI: 0.08 to 0.80) at 90° of flexion. Additionally, anterior laxity was directly correlated with MCP-1 concentrations (ρ=0.62, p=0.006, n=18, 95% CI: 0.22 to 0.84) at 90° of flexion. Cr was inversely correlated with IL-6 (ρ=-0.52, p=0.01, n=21, 95% CI: -0.78 to -0.11). Cr was also inversely correlated with MIP-3α (ρ=-0.46, p=0.04, n=21, 95% CI: -0.74 to -0.04). Discussion. The specimens included in this study consisted of primary TKA implants that were retrieved at necropsy and were determined to be well-fixed per fluoroscopic analysis. The first objective of this study was to establish a baseline of different factors that likely contribute to failure of primary total knee replacements. This study provided semi-quantitative assessment of wear of the condylar surface, backside surface, and stabilizing post, when applicable, and of damage to the bearing surface of the femoral components. Joint laxity was measured using a custom knee testing platform that had been previously studied and utilized in published journal articles and theses. Inflammatory cytokine profiles in the synovial fluid samples were presented and measureable levels of metal debris was found in the periprosthetic tissue samples. The second objective of this study was to determine if any significant relationships arose in correlation analysis of the latter three aforementioned factors. An inverse trend was observed between joint laxity and tissue metal concentrations, such that decreased laxity induced metal release from the implant components. A direct trend was observed specifically between increased anteroposterior laxity and elevated inflammatory cytokines. Lastly, an inverse trend was found between decreased tissue metal concentrations and increased inflammatory cytokines. The third, and future, objective of this study is to utilize these measurements and observations for comparison with failed implants retrieved at time of revision. While some meaningful relationships were observed in this study, there were several limitations that must be noted. Firstly, this study had a relatively small sample size. Secondly, the cohort included a wide range of implants including cruciate-retaining, posterior-stabilized, fixed bearing, mobile bearing, monoblock, and modular designs fabricated from different material

    1st EFORT European Consensus: Medical & Scientific Research Requirements for the Clinical Introduction of Artificial Joint Arthroplasty Devices

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    Innovations in Orthopaedics and Traumatology have contributed to the achievement of a high-quality level of care in musculoskeletal disorders and injuries over the past decades. The applications of new implants as well as diagnostic and therapeutic techniques in addition to implementation of clinical research, have significantly improved patient outcomes, reduced complication rates and length of hospital stay in many areas. However, the regulatory framework is extensive, and there is a lack of understanding and clarity in daily practice what the meaning of clinical & pre‐clinical evidence as required by the MDR is. Thus, understanding and clarity are of utmost importance for introduction of new implants and implant-related instrumentation in combination with surgical technique to ensure a safe use of implants and treatment of patients. Therefore EFORT launched IPSI, The Implant and Patient Safety Initiative, which starting from an inaugural workshop in 2021 issued a set of recommendations, notably through a subsequent Delphi Process involving the National Member Societies of EFORT, European Specialty Societies as well as International Experts. These recommendations provide surgeons, researchers, implant manufacturers as well as patients and health authorities with a consensus of the development, implementation, and dissemination of innovation in the field of arthroplasty. The intended key outcomes of this 1st EFORT European Consensus on “Medical & Scientific Research Requirements for the Clinical Introduction of Artificial Joint Arthroplasty Devices”are consented, practical pathways to maintain innovation and optimisation of orthopaedic products and workflows within the boundaries of MDR 2017/745. Open Access practical guidelines based on adequate, state of the art pre-clinical and clinical evaluation methodologies for the introduction of joint replacements and implant-related instrumentation shall provide hands-on orientation for orthopaedic surgeons, research institutes and laboratories, orthopaedic device manufacturers, Notified Bodies but also for National Institutes and authorities, patient representatives and further stakeholders. We would like to acknowledge and thank the Scientific Committee members, all International Expert Delegates, the Delegates from European National & Specialty Societies and the Editorial Team for their outstanding contributions and support during this EFORT European Consensus

    Um novo modelo de conceito para implantes ortopédicos instrumentados ativos

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    Doutoramento em Engenharia MecânicaTotal hip replacement (THR) is one of the most performed surgical procedures around the world. Millions of THR are carried out worldwide each year. Currently, THR revision rates can be higher than 10%. A significant increase of the number of primary and revision THRs, mainly among patients less than 65 years old (including those under 45 years old) has been predicted for the forthcoming years. A worldwide increase in the use of uncemented fixation has also been reported, incidence caused mainly by the significant increase of more active and/or younger patients. Besides the significant breakthroughs for uncemented fixations, they have not been able to ensure long-term implant survival. Up to date, current implant models have shown evidences of their inability to avoid revision procedures. The performance of implants will be optimized if they are designed to perform an effective control over the osseointegration process. To pursue this goal, improved surgical techniques and rehabilitation protocols, innovative bioactive coatings (including those for controlled delivery of drugs and/or other bio-agents in the bone-implant interface), the concepts of Passive Instrumented Implant and Active Instrumented Implant have been proposed. However, there are no conclusive demonstrations of the effectiveness of such methodologies. The main goal of this thesis is to propose a new concept model for instrumented implants to optimize the bone-implant integration: the self-powered instrumented active implant with ability to deliver controlled and personalized biophysical stimuli to target tissue areas. The need of such a new model is demonstrated by optimality analyses conducted to study the performance of instrumented and non-instrumented orthopaedic implants. Promising results on the potential of a therapeutic actuation driven by cosurface-based capacitive stimulation were achieved, as well as for self-powering instrumented active implants by magnetic levitation-based electromagnetic energy harvesting.A artroplastia total da anca (THR) é um dos procedimentos cirúrgicos mais realizados à escala global. Milhões de THRs são realizadas todos os anos em todo o mundo. Atualmente, as taxas de revisão destas artroplastias podem ser superiores a 10%. O número de THRs primárias e de revisão têm aumentado e estima-se que cresçam acentuadamente nos próximos anos, principalmente em pacientes com idades inferiores a 65 anos (incluindo aqueles com menos de 45 anos). Também se tem verificado uma tendência generalizada para o uso de fixações não cimentadas, incidência principalmente causada pelo aumento significativo de pacientes mais jovens e/ou activos. Embora se tenham realizado avanços científicos no projeto de implantes não cimentados, têm-se verificado o seu insucesso a longo-prazo. Encontram-se evidências da ineficácia dos modelos de implantes que têm sido desenvolvidos para evitar procedimentos de revisão. O desempenho dos implantes será otimizado se estes foram projetados para controlarem eficazmente o processo de osseointegração. Para se alcançar este objetivo, têm sido propostas a melhoria das técnicas cirúrgicas e dos protocolos de reabilitação, a inovação dos revestimentos (onde se incluem os revestimentos ativos projetados para a libertação controlada de fármacos e/ou outros bio-agentes) e os conceitos de Implante Instrumentado Passivo e Implante Instrumentado Ativo. Contudo, não existem demonstrações conclusivas da eficácia de tais metodologias. O principal objetivo desta tese é propor um novo modelo de conceito para implantes instrumentados para se otimizar a integração osso-implante: o implante instrumentado ativo, energeticamente auto-suficiente, com capacidade de aplicar estímulos biofísicos em tecidos-alvo de forma controlada e personalizada. A necessidade de um novo modelo é demonstrada através da realização de análises de otimalidade ao desempenho dos implantes instrumentados e não-instrumentados. Foram encontrados resultados promissores para o controlo otimizado da osseointegração usando este novo modelo, através da atuação terapêutica baseada na estimulação capacitiva com arquitetura em co-superfície, assim como para fornecer energia elétrica de forma autónoma por mecanismos de transdução baseados em indução eletromagnética usando configurações baseadas na levitação magnética

    Biomechanical Analysis of Fixation and Bone

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    Long-term survivorship of a total knee replacement (TKR) relies on the strength of bone around the implant and its initial stability. Aseptic component loosening caused by mechanical factors is a recognised failure mode for knee prostheses. Bone resorption due to “stress-shielding” of the stiff stemmed implants will potentially lead to weakened bone strength, and presents a challenge for revision TKR surgery. The aim of this study was to develop analytical methodologies for the investigation of fixation performance of TKR, and to gain a better understanding of the prosthetic design requirements, addressing two major mechanical problems of bone remodelling and aseptic loosening. Patient-specific finite element (FE) modelling incorporated with a strain-adaptive bone remodelling theory was used to simulate bone remodelling responses of the postoperative tibial fixation. The choice of cementing technique was found to influence the remodelling behaviour; cemented fixationmodelled as a firm anchorage of the prosthesis onto the bone, was predicted to induce greater stress-shielding effect consequently leading to severe proximal bone resorption; for a fixation relying on biological attachment of bony ingrowthmodelled as a less firmly anchored boneprosthesis interface, lesser proximal bone resorption was predicted. The consideration of bone remodelling in FE simulations for fixation analyses is paramount as it influenced the risk prediction of aseptic loosening between prosthesis designs. The cement tensile stresses and bone-prosthesis interface micromotions predicted were different prior to and after bone adaptation. FE predictions of the MIS mini-keel and standard stemmed prosthesis fixations after simulating six months of bone adaptation correlated well with the RSA measurements at a similar period. A modified in-vitro technique of measuring bone-prosthesis relative micromotion was developed for relating initial stability of the cemented and cementless (press-fit) tibial prostheses fixations to late aseptic loosening. The developed computational and invitro methods should be applicable to other joint replacements

    Biomechanical behaviour of cancellous bone on patellofemoral arthroplasty with journey prosthesis : a finite element study

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    Isolated patellofemoral (PF) arthritis of the knee is a common cause of anterior knee pain and disability. Patellofemoral arthroplasty (PFA) is a bone conserving solution for patients with PF degeneration. Failure mechanisms of PFA include growing tibiofemoral arthritis and loosening of components. The implant loosening can be associated with bone resorption, or fatigue-failure of bone by overload. This research work aims at determining the structural effects of the implantation of PF prosthesis Journey PFJ (Smith&Nephew, USA) on femur cancellous bone. For this purpose, the finite element (FE) method is considered to perform computational simulations for different conditions, such as well-fixed and loosening scenarios. From the global results obtained, in the well-fixed scenario, a strain decrease on cancellous bone was noticed, which can be related to bone resorption. In the loosening scenario, when the cement layer becomes inefficient, a significant increase of cancellous bone strain was observed, which can be associated with bone fatigue-failure. These strain changes suggest a weakness of the femur after PFA.Fundação para a Ciência e a Tecnologia (FCT

    Wear and Boundary Lubrication in Modular Total Knee Replacements

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    Wear of the polyethylene (PE) bearing surface and wear particle-induced osteolysis (bone resorption) can lead to failure of modular total knee replacements and make expensive revision surgery necessary. Gamma-in-air sterilization of the PE insert and having a modular tibial component are both risk factors for excessive backside wear that contribute to osteolysis and implant failure. The overall wear (backside and topside) of modular total knee replacements has been subjected to considerable research in order to avoid such implant failure. The investigations reported in the present thesis evaluated both the clinical and in vitro wear performance of modular total knee replacements. The clinical investigations included damage assessment of retrieved PE inserts. A semi-quantitative grading method was developed and used to assess backside surface damage on 52 PE inserts retrieved from contemporary total knee replacement surgeries. Statistical analyses, such as univariate and multiple linear regression analysis, were performed to identify factors that influence backside damage including implant design features and patient characteristics. The damage features on the retrieved tibial PE inserts were also assessed with surface characterization techniques, such as scanning electron microscopy, energy dispersive X-ray analysis, and surface profilometry. To reduce surface damage and thus wear, PE inserts should be either gas-plasma or ethylene-oxide sterilized, used with polished tibial trays and held in place with a partial-peripheral locking mechanism. Synovial fluid samples were aspirated from a total of twenty patients and some basic biochemical analyses were performed. The total protein concentration, protein constituent fractions, the level of osmolality, and trace element concentrations were measured and compared with the same characteristics of four serum lubricants that were frequently used in simulator wear testing to mimic synovial fluid. In vitro investigations were conducted to explore the effects of some major constituents of the serum lubricants on the wear rate using a knee simulator apparatus. Increased protein constituent degradation led to increased wear. Such findings suggested that a protein layer acted as a boundary lubricant to protect the PE surfaces of knee implants. The protein constituent fractions of alpha calf serum (ACS) were similar to those measured for synovial fluid. These ACS lubricants were used in further wear studies in which hyaluronic acid (HA) and phosphate buffer solution (PBS) were successively added. The PBS was used in place of the distilled water to generate a serum lubricant with a clinically relevant level of osmolality. The thermal stability of the ACS lubricants and synovial fluid were measured. The thermal stability of the ACS lubricant that contained HA and PBS was about the same as that of human synovial fluid. The simulator wear rate of PE was significantly influenced by both HA and PBS. In further investigations, sodium azide, which has been used to inhibit microbial growth in simulator wear testing, was shown to be highly ineffective. Microbial contamination was recognized and the organism responsible was identified using standard microbiological methods. The use of an antibiotic-antimycotic mixture as the microbial inhibitor in the ACS + PBS + HA lubricant created a sterile environment and thus very clinically relevant environment for wear testing. The content of this thesis represents a comprehensive data collection on retrieval analysis and lubricant-specific knee simulator wear testing of modular total knee replacements. A more clinically relevant lubricant composition for simulator wear testing was proposed (U.S. patent Serial number 60/899,894; pending since February 9th, 2007) that improved upon the current guideline from the International Standards Organization for knee simulator wear testing. The present thesis should serve as a guide for the surgeon, researcher and the implant manufacturer to evaluate retrieved implant components and to select lubricant additives for wear testing that closely mimics the in vivo wear conditions

    Periprosthetic bone loss: diagnostic and therapeutic approaches.

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    Total joint replacement surgery is being performed on an increasingly large part of the population. Clinical longevity of implants depends on their osseointegration, which is influenced by the load, the characteristics of the implant and the bone-implant interface, as well as by the quality and quantity of the surrounding bone. Aseptic loosening due to periprosthetic osteolysis is the most frequent known cause of implant failure. Wear of prosthetic materials results in the formation of numerous particles of debris that cause a complex biological response. Dual-energy X-ray Absorptiometry (DXA) is regarded as an accurate method to evaluate Bone Mineral Density (BMD) around hip or knee prostheses. Further data may be provided by a new device, the Bone Microarchitecture Analysis (BMA), which combines bone microarchitecture quantification and ultra high resolution osteo-articular imaging. Pharmacological strategies have been developed to prevent bone mass loss and to extend implant survival. Numerous trials with bisphosphonates show a protective effect on periprosthetic bone mass, up to 72 months after arthroplasty. Strontium ranelate has been demonstrated to increase the osseointegration of titanium implants in treated animals with improvement of bone microarchitecture and bone biomaterial properties
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