59 research outputs found
Biomechanics of Contemporary Implants and Prosthesis: Modeling, Experiments, and Clinical Application
Modern medicine is now more oriented towards patient-based treatments. Taking into account individual biological features allows for increasing the quality of the healing process. Opportunities for modern hardware and software allow not only the complex behavior of implants and prostheses to be simulated, but also take into account any peculiarities of the patient. Moreover, the development of additive manufacturing expands the opportunities for materials. Technical limits for composite materials, biomaterials, and metamaterials are decreasing. On the other hand, there is a need for more detailed analyses of biomechanics research. A deeper understanding of the technological processes of implants, and the mechanobiological interactions of implants and organisms will potentially allow us to raise the level of medical treatment. Modern trends of the biomechanics of contemporary implants and prostheses, including experimental and mathematical modeling and clinical application, are discussed in this book
Finite element simulation of hip joint replacement under static and dynamic loading
The objective of this work is to develop methods for the structural analysis of orthopaedic implants. The central argument is that, if stress distributions are interpreted in the context of failure models of the component materials, significant advantages can be made in our ability to design these devices. The artificial hip joint is used throughout as an example.
The finite element method was used as a structural analysis tool and its pplicability was discussed. Validity and accuracy were assessed and results were ompared with previous experimental and finite element studies. By comparing tress distributions with failure criteria for prosthesis and cement, the suitability of roposed design changes were assessed and guidelines for materials selection were resented. Prediction of bone stresses were also given for different prosthesis designs n the region of the artificial hip joint where bone adaption contributes to failure. hereafter the focus was on utilizing a new technique to develop a new hip prosthesis model.
This study was divided into two parts according to the loading type. In this regard the stress field in the artificial hip components (prostheses, cement mantle, and bone) is analysed statically and dynamically to assess the implant longevity. In this static analysis all the simulations were conducted by assuming the peak loads during the normal gait at a particular time (static loads). The aim was to study the effects of a set of variables within which an optimal prosthesis design can be made by means of finite element analysis to qualify and quantify the stresses and the strains in natural and treated human femur for different cases of implantation. Until now, models developed to predict stresses in total hip replacements have been generally poorly validated. This could be because all the pre-clinical simulations were performed statically, that is by selecting the greatest load at a particular time of the activity cycle. The second part of the study was aimed to take into consideration, in designing total hip replacement, another factor belongs to the patient activity (stamping, jumping, walking, etc) and the effect of impact over the prosthesis head during these activity into the prosthesis performance. This study considered the prosthesis hip deformation with time, dynamic loads study. The elimination of impact cracking was considered by studying the effect of using “damper” trapped between the grooved prosthesis collar and the bone. Material selection of the total hip replacements was also investigated under the dynamic loading. The approaches of prosthesis fixation have been studied, too. This study was conducted by onstructing three-dimensional finite element model for a femur implanted with a cemented prosthesis with a representative physiological loading condition by using he LS-DYNA3D software
Um novo modelo de conceito para implantes ortopédicos instrumentados ativos
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
ITAP: Clinical outcomes and implant design optimisation using numerical modelling
Redistribution of the flow of forces through the body, such as that after amputation and/or implantation of a skeletally anchored amputation prostheses, leads to bone remodelling. Periprosthetic bone resorption can destabilise skeletally anchored amputation prostheses. Therefore, implants that minimise bone resorption will achieve a more successful long term bone fixation. Bone remodelling outcome measures rely on implant design using mechanoregulatory bone remodelling theory. Mechanoregulation is implemented by functions that link a local mechanical stimulus to a local change in the structure or properties of bone material. This thesis uses the strain adaptive remodelling theory at the time of implantation with periprosthetic strain energy density as the outcome parameter. Clinical trial data was collected from a patient with a skeletally anchored amputation prostheses; The Intraosseous Transcutaneous Amputation Prosthesis (ITAP). The clinical trial ran from 2008 – 2019, the data was investigated for patterns between implant design and fixation success. This thesis reports trends in fixation success and bone change using a developed fixation success score. There was an ideal implant length to bone length ratio range and a straight, tapered stem with a flared bone collar growth shape were beneficial to fixation success. Conversely, one or more parameters associated with pressfit fixation were detrimental to fixation success. Results between the clinical and numerical data compared favourably; clinically, regions of periprosthetic bone growth were also observed by regions of high strain energy density in the finite element analysis and vice versa at the implant tip and osteotomy face. This thesis provides skeletally anchored amputation prostheses design guidelines that will minimise bone resorption when measured with strain energy density. Moreover, that future skeletally anchored amputation prostheses parameterised design can and should be used as a tool to assess bone fixation outcome in pre-clinical assessments
Development of Optimal Total Hip Joint Replacement
Total hip replacement (THR) is a surgical process in which the hip joint is replaced by a hip prosthesis. It is one of the most popular and cost effective surgery. In particular in 2014, 83,125 primary procedures were recorded. Some of these operations need to be carried out again for different reasons after sometime. These are called revision (replacement of the prosthesis) procedures. Important studies and statistics suggest that the number of THR procedures is projected to increase by almost 175% by 2030. Aseptic loosening appears to be the most significant cause of failure in THR. Aseptic loosening might lead to revision surgery and in turn can be avoided by enhancing the stability and durability of the hip replacement. Primary stability attained after surgery is a determinant issue for the long-term stability of cementless hip arthroplasty. Primary stability is the level of relative micromotion between the femur and the prosthesis induced via the physiological joint forces following the surgery. The hip prosthesis is also exposed to dynamic loadings and activities of daily living, which can induce the stress distribution on the prosthesis of the hip joint model and affect the durability of the implant. The aim of this study is to develop an optimal total hip replacement (THR) implant with new and improved design features to achieve stability and durability. The micromotion between bone and implant interface and the stress distribution on the prosthesis and femur assembly has been reviewed and investigated. The laboratory testing were carried out on the femur including the compression, torsion and Brinell hardness testing. A compression testing using strain gauge technique done on the hip implant. Finite element analysis software used to simulate all compression and torsion testing assuming the same boundary and loading conditions and subsequently the computational results were compared with the earlier experimental data to verify the experiments and models used. 7 The comparative micromotion studies and findings of other researchers were used beside the clinical follow-up reports on success or failure rates of related hip designs, to justify the best solutions for design factors. In this computational approach researchers usually use finite element methodology to calculate micromotion of elements, sometimes known as migration. The elements exceeding the threshold limit would simulate the migration and subsequently eliminated from the assembly. This procedure recurs until reaching the convergence that derives a stable mechanical equilibrium. One of the restrictions of micromotion analysis was the inability to divide the final results into axial and rotational components. Therefore it would have been inappropriate to eventually conclude the best femoral stem, without considering the sustaining torsional loadings. Another limitation was that the micromotion analysis would not reflect the stress distribution on the hip prosthesis and consequently would ignore the potential high stress concentration that is associated with post operative pain as well as low durability and long-term stability. For these reasons stress analysis was carried out under dynamic loadings of nine different activities to examine the von Mises stress, shear stress and principal stress distribution of a cementless hip implant. In each activity realistic boundary and loading conditions of a complete assembly of femur and hip implant were investigated which includes defining of many variables including different geometry, material properties, boundary conditions, forces and moments of varying magnitude and orientation over specific time intervals. The critical points and areas that were developed in the entire 3D model were evaluated and explained. The finite element analysis which verified by experimental testing and hold the clinical relevance were used to decide the best optimal hip stem design amongst different presented design concepts. This was accompanied and improved with further stress analysis of different design factors to get the final optimal model. High offset stem option is a unique feature that helps tightening the abductor and boosts the hip implant stability with the ability to adjust neck and offset. It gives a surgeon more options to fix the most accurate offset and do the operation more effectively. The final optimal design and its advantages were presented in the last chapter
An Investigation Of The Design And Function Of Knee Joint-sparing Massive Endoprostheses
Distal femoral and proximal tibial joint-sparing bone tumour implants allow to preserve the knee, in limb salvage surgery. The aim of this thesis was to compare implant survival, functional outcomes, acceptance, proprioception and gait in patients with knee sparing implants and conventional knee sacrificing implants. Using FEA, a distal femoral implant and cadaver bone were modelled and parametrised to find the design that improves implant fixation. A survivorship study of 104 consecutive patients following knee sparing surgery (mean follow-up 36.1 ± 11.0 months) found an implant survival rate of 78% and this is comparable to the reported survival for joint sacrificing prostheses. Younger patients showed improved implant survival compared to older individuals. Plate fracture was not observed and aseptic loosening was the main reason for revision. Radiographic analysis indicated that implantation accuracy increased implant survival. Patient questionnaires showed that patients with knee sparing implants had more normal functional outcome and acceptance compared with patients with knee sacrificing implants. However, proprioception (joint position sense) was reduced in these patients. Using optoelectronic gait analysis system, hip, knee and ankle joint angle in 19 patients and 3 healthy subjects were measured. Ground reaction force and time in stance were also investigated. Joint symmetry in the joint sacrificing group was improved compared to the joint-sparing group, however overall, the joint-sparing tibial group demonstrated a more normal gait pattern. FEA results indicated that lower resection levels, reduced plate thickness and implant materials with lower modulus, decreased the stresses in the bone adjacent to the implant while loaded the bone more to reduce risk of stress shielding. To conclude, knee sparing endoprostheses provide a reliable alternative to knee sacrificing implants in limb reconstruction in selected patients. However, the current design of joint-sparing implants can be optimised to potentially improve bone remodelling and implant fixation
1st EFORT European Consensus: Medical & Scientific Research Requirements for the Clinical Introduction of Artificial Joint Arthroplasty Devices
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
- …