Lower Stiffness Orthopaedic Implants for Hemiarthroplasty

One of the main drawbacks of hemiarthroplasty is that it involves the articulation of a foreign material against the native cartilage, and hence the native cartilage experiences accelerated wear. It is hypothesized that lowering the stiffness of hemiarthroplasty implants will decrease contact pressure and increase contact area, thus decrease wear. Lowering the stiffness was done using finite element analysis to lower the stiffness of the implant materials, and then to change the internal structure of the implants to increase their compliance. Structural changes produced no noticeable or favourable results, whereas material produced improved results for stiffnesses below a Young’s modulus of 300 MPa. A cadaveric study was done to compare a high, mid, and ultra-low stiffness material to the native state. It was found that only the ultra- low stiffness material improved contact mechanics. Future hemiarthroplasty implant designs should focus on using materials with a Young’s modulus below the aforementioned threshold

Computer Aided Tools for the Design and Planning of Personalized Shoulder Arthroplasty

La artroplastia de hombro es el tercer procedimiento de reemplazo articular más común, después de la artroplastia de rodilla y cadera, y actualmentees el de más rápido crecimiento en el campo ortopédico. Las principales opciones quirúrgicas incluyen la artroplastia total de hombro (TSA), en la quese restaura la anatomía articular normal, y, para pacientes con un manguito rotador completamente desgarrado, la artroplastia inversa de hombro (RSA), en la que la bola y la cavidad de la articulación glenohumeral se cambian. A pesar del progreso reciente y los avances en el diseño, las tasas de complicaciones reportadas para RSA son más altas que las de la artroplastia de hombro convencional. Un enfoque específico para el paciente, en el que los médicos adaptan el tratamiento quirúrgico a las características del mismo y al estado preoperatorio, por ejemplo mediante implantes personalizados y planificación previa, puede ayudar a reducir los problemas postoperatorios y mejorar el resultado funcional. El objetivo principal de esta tesis es desarrollar y evaluar métodos novedosos para RSA personalizado, utilizando tecnologías asistidas por ordenador de última generación para estandarizar y automatizar las fases de diseño y planificación.Los implantes personalizados son una solución adecuada para el tratamiento de pacientes con pérdida extensa de hueso glenoideo. Sin embargo, los ingenieros clínicos se enfrentan a muchas variables en el diseño de implantes (número y tipo de tornillos, superficie de contacto, etc.) y una gran variabilidad anatómica y patológica. Actualmente, no existen herramientas objetivas para guiarlos a la hora de elegir el diseño óptimo, es decir, con suficiente estabilidad inicial del implante, lo que hace que el proceso de diseño sea tedioso, lento y dependiente del usuario. En esta tesis, se desarrolló una simulación de Virtual Bench Test (VBT) utilizando un modelo de elementos finitos para evaluar automáticamente la estabilidad inicial de los implantes de hombro personalizados. A través de un experimento de validación, se demostró que los ingenieros clínicos pueden utilizar el resultado de Virtual Bench Test como referencia para respaldar sus decisiones y adaptaciones durante el proceso de diseño del implante.Al diseñar implantes de hombro, el conocimiento de la morfología y la calidad ósea de la escápula en toda la población es fundamental. En particular, se tienen en cuenta las regiones con la mejor reserva ósea (hueso cortical) para definir la posición y orientación de los orificios de los tornillos, mientras se busca una fijación óptima. Como alternativa a las mediciones manuales, cuya generalización está limitada por el análisis de pequeños subconjuntos de pacientes potenciales, Statistical Shape Models (SSMs) se han utilizado comúnmente para describir la variabilidad de la forma dentro de una población. Sin embargo, estos SSMs normalmente no contienen información sobre el grosor cortical.Por lo tanto, se desarrolló una metodología para combinar la forma del hueso escapular y la morfología de la cortical en un SSM. Primero, se presentó y evaluó un método para estimar el espesor cortical, a partir de un análisis de perfil de Hounsfield Unit (HU). Luego, utilizando 32 escápulas sanas segmentadas manualmente, se creó y evaluó un modelo de forma estadística que incluía información de la cortical. La herramienta desarrollada se puede utilizar para implantar virtualmente un nuevo diseño y probar su congruencia dentro de una población virtual generada, reduciendo así el número de iteraciones de diseño y experimentos con cadáveres.Las mediciones del alargamiento de los músculos deltoides y del manguito rotador durante la planificación quirúrgica pueden ayudar a los médicos aseleccionar un diseño y una posición de implante adecuados. Sin embargo, tal evaluación requiere la indicación de puntos anatómicos como referencia para los puntos de unión de los músculos, un proceso que requiere mucho tiempo y depende del usuario, ya que a menudo se realiza manualmente. Además, las imágenes médicas, que se utilizan normalmente para la artroplastia de hombro,contienen en su mayoría solo el húmero proximal, lo que hace imposible indicarlos puntos de unión de los músculos que se encuentran fuera del campo de visión de la exploración. Por lo tanto, se desarrolló y evaluó un método totalmente automatizado, basado en SSM, para medir la elongación del deltoides y del manguito rotador. Su aplicabilidad clínica se demostró mediante la evaluación del rendimiento de la estimación automatizada de la elongación muscular para un conjunto de articulaciones artríticas del hombro utilizadas para la planificación preoperatoria de RSA, lo que confirma que es una herramienta adecuada para los cirujanos a la hora de evaluar y refinar las decisiones clínicas.En esta investigación, se dio un paso importante en la dirección de un enfoque más personalizado de la artroplastia inversa de hombro, en el que el manejo quirúrgico, es decir, el diseño y la posición del implante, se adapta a las características específicas del paciente y al estado preoperatorio. Al aplicar tecnologías asistidas por computadora en la práctica clínica, el proceso de diseño y planificación se puede automatizar y estandarizar, reduciendo así los costos y los plazos de entrega. Además, gracias a los métodos novedosos presentados en esta tesis, esperamos en el futuro una adopción más amplia del enfoque personalizado, con importantes beneficios tanto para los cirujanos como para los pacientes.Shoulder arthroplasty is the third most common joint replacement procedure, after knee and hip arthroplasty, and currently the most rapidly growing one in the orthopaedic field. The main surgical options include total shoulder arthroplasty (TSA), in which the normal joint anatomy is restored, and, for patients with a completely torn rotator cuff, reverse shoulder arthroplasty (RSA), in which the ball and the socket of the glenohumeral joint are switched. Despite the recent progress and advancement in design, the reported rates of complication for RSA are higher than those of conventional shoulder arthroplasty. A patient-specific approach, in which clinicians adapt the surgical management to patient characteristics and preoperative condition, e.g. through custom implants and pre-planning, can help to reduce postoperative problems and improve the functional outcome. The main goal of this thesis is to develop and evaluate novel methods for personalized RSA, using state-of-the-art computer aided technologies to standardize and automate the design and planning phases. Custom implants are a suitable solution when treating patients with extensive glenoid bone loss. However, clinical engineers are confronted with an enormous implant design space (number and type of screws, contact surface, etc.) and large anatomical and pathological variability. Currently, no objective tools exist to guide them when choosing the optimal design, i.e. with sufficient initial implant stability, thus making the design process tedious, time-consuming, and user-dependent. In this thesis, a Virtual Bench Test (VBT) simulation was developed using a finite element model to automatically evaluate the initial stability of custom shoulder implants. Through a validation experiment, it was shown that the virtual test bench output can be used by clinical engineers as a reference to support their decisions and adaptations during the implant design process. When designing shoulder implants, knowledge about bone morphology and bone quality of the scapula throughout a certain population is fundamental. In particular, regions with the best bone stock (cortical bone) are taken into account to define the position and orientation of the screw holes, while aiming for an optimal fixation. As an alternative to manual measurements, whose generalization is limited by the analysis of small sub-sets of the potential patients, Statistical Shape Models (SSMs) have been commonly used to describe shape variability within a population. However, these SSMs typically do not contain information about cortical thickness. Therefore, a methodology to combine scapular bone shape and cortex morphology in an SSM was developed. First, a method to estimate cortical thickness, starting from a profile analysis of Hounsfield Unit (HU), was presented and evaluated. Then, using 32 manually segmented healthy scapulae, a statistical shape model including cortical information was created and assessed. The developed tool can be used to virtually implant a new design and test its congruency inside a generated virtual population, thus reducing the number of design iterations and cadaver labs. Measurements of deltoid and rotator cuff muscle elongation during surgical planning can help clinicians to select a suitable implant design and position. However, such an assessment requires the indication of anatomical landmarks as a reference for the muscle attachment points, a process that is time-consuming and user-dependent, since often performed manually. Additionally, the medical images, which are normally used for shoulder arthroplasty, mostly contain only the proximal humerus, making it impossible to indicate those muscle attachment points which lie outside of the field of view of the scan. Therefore, a fully-automated method, based on SSM, for measuring deltoid and rotator cuff elongation was developed and evaluated. Its clinical applicability was demonstrated by assessing the performance of the automated muscle elongation estimation for a set of arthritic shoulder joints used for preoperative planning of RSA, thus confirming it a suitable tool for surgeons when evaluating and refining clinical decisions. In this research, a major step was taken into the direction of a more personalized approach to Reverse Shoulder Arthroplasty, in which the surgical management, i.e. implant design and position, is adapted to the patient-specific characteristics and preoperative condition. By applying computer aided technologies in the clinical practice, design and planning process can be automated and standardized, thus reducing costs and lead times. Additionally, thanks to the novel methods presented in this thesis, we expect in the future a wider adoption of the personalized approach, with important benefits both for surgeons and patients.<br /

Tribological testing of potential hemiarthroplasty materials using a custom-designed multi-directional reciprocating rig

The material selection plays a major role in the design of a patellofemoral joint (PFJ) replacement due to the reported damage of the femoral condyles in deep knee flexion using ultra-high molecular weight polyethylene for the patellar components. The use of softer materials such as PCU and PVA/PVP may induce fluid film lubrication and thus reduce the risk of cartilage damage. This research aims to investigate in-vitro tribological performance of the articulation of cartilage-on-PCU (Bionate® I 80A and Bionate® II 80A) and cartilage-on-PVA/PVP (different concentrations and PVA to PVP fractions) using a custom-designed multi-directional pin-on-plate rig. PVA/PVP showed low COF values (between 0.12±0.01 and 0.14±0.02) which were closer to the cartilage-on-cartilage articulation (0.03±0.01) compared to PCUs (0.41±0.02 for Bionate® II 80A and 0.50±0.02 for Bionate® I 80A). However, these PVA/PVP hydrogels were worn massively after 15 h articulation against the condyles. On the other hand, the counter-face condyles of PCUs were severely damaged, similar to the damage observed in the cartilage-on-stainless steel articulation. Among the PCUs, Bionate® II 80A showed superior tribological performance without depending on the lubricant and surface roughness parameters. When a migrating cartilage contact was achieved by articulating PCU pins on cartilage plates, PCUs revealed similar COF values (0.04±0.01) to the cartilage-on-cartilage articulation. This work has shown that PVA/PVP hydrogels require further development to enhance their wear resistance if they are to be used as part of a joint replacement. However, they have low COF against articular cartilage and so are attractive possibilities for the future. The tested PCU grades have shown PCUs (especially Bionate® II 80A) can work with acceptably low COF under the right articulating conditions and that they have low wear in those tests. Therefore, the work in this thesis supports the further development of patellofemoral joint prostheses which include PCU components.Open Acces

Failure Analysis of Biometals

Metallic biomaterials (biometals) are widely used for the manufacture of medical implants, ranging from load-bearing orthopaedic prostheses to dental and cardiovascular implants, because of their favourable combination of properties, including high strength, fracture toughness, biocompatibility, and wear and corrosion resistance. Owing to the significant consequences of implant material failure/degradation, in terms of both personal and financial burden, failure analysis of biometals has always been of paramount importance in order to understand the failure mechanisms and implement suitable solutions with the aim to improve the longevity of implants in the body. Failure Analysis of Biometals presents some of the latest developments and findings in this area. This includes a great range of common metallic biomaterials (Ti alloys, CoCrMo alloys, Mg alloys, and NiTi alloys) and their associated failure mechanisms (corrosion, fatigue, fracture, and fretting wear) that commonly occur in medical implants and surgical instruments

Investigating the ideal deltoid kinematics and tension in reverse shoulder arthroplasty (RSA).

The shoulder is the one of the most active joints within the human body. Recruited in the majority of daily activities either in active use such as moving/carrying of objects or as a source of stability during locomotion. Therefore painful shoulder or its reduced mobility and function can be very debilitating hence affecting the quality of life. While shoulder pain and restricted motion encompasses a diverse array of pathologies, the most common causes are due to infection, arthritis, or trauma. Arthroplasty (the surgical reconstruction or replacement of a joint) of the shoulder has offered the potential for improved function and pain relief where the native structures have been damaged. The conventional total shoulder replacement, however, is not beneficial for all patients and may result in further pain and limited motion in persons with arthritic shoulders with a deficient rotator cuff. For these patients Reverse Shoulder Arthroplasty (RSA), in which anatomic concavities of glenohumeral joint are inverted, is a popular treatment. However, for optimal restoration of motion, the correct positioning of the glenohumeral centre of rotation and initial setting of the deltoid length (Deltoid Tension) must play an important role in the surgery outcome. A study of the key literature has shown that despite common use of RSA, its biomechanical characteristics during motion are not fully understood. This study investigates the influence of some of the key parameters on the intensity of forces and moments in the shoulder joint before, during and after RSA. These parameters include; geometry, kinematics and muscle passive force measurement (deltoid pretension measurement). To investigate the effect of geometrical changes on kinematics of shoulder after RSA, a musculoskeletal model of the shoulder is developed and simulated. Geometrical parameters of the musculoskeletal model are extracted from previous published studies. Results of the simulation enabled the detection of key parameters in reverse shoulder kinematics and its influence on determining the mechanical advantage of the shoulder mechanism. This identified the need for developing an X-ray imaging protocol and image processing tool that enable surgeons to predict optimum implants insertion position and estimate the performance of the shoulder before planning the operation. Subsequently, an assessment tool was proposed to assess shoulder Range of Motion (ROM) and deltoid muscle activity to both quantify and validate the predicted outcome of the surgery. The main purpose of this study is to measure the passive force exerted on the reverse shoulder joint during surgery as a criterion or measure of deltoid pretension. Hence a force sensor is designed, developed and tested in a custom built joint simulator. As part of this research and to allow objective assessment of the joint, a series of tools/hardware/software were proposed, designed and developed, and then tested and evaluated for effectiveness and functionality. The introduction of a system proposed here provides data which could be recorded in a database along with geometrics and kinematics pre and post operatively, residual force in glenohumeral joint intraoperatively and shoulder performance in terms of range of motion and EMG muscle activity of individual patients pre and post operatively. Such a database in time will enable us to find correlations between these parameters and the outcome of surgery in the long term. It is hoped that this will provide a tool for surgeons in future operations to who choose to use a more quantitative and repeatable way of optimizing the implant size and position accordingly

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 &amp; 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 &amp; 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 &amp; Specialty Societies and the Editorial Team for their outstanding contributions and support during this EFORT European Consensus

Treatment of patients with hand osteoarthritis : outcome measures, patient satisfaction, and economic evaluation

The aim of this thesis was to investigate the limitations in daily life, outcome measures, clinical outcomes with the emphasis on patient satisfaction, and economic aspects of the treatment of hand osteoarthritis (OA). Patients with hand OA report severe restrictions in daily life, in particular in opening food packaging. We defined guidelines for the industry on the production of easy-to-open food packaging to make life easier for patients in the future. For evaluating the outcome of an intervention, numerous patient-reported outcome measures are used at present with questionable measurement properties. We could show that the Michigan Hand Outcomes Questionnaire demonstrates good measurement properties in patients with trapeziometacarpal (TMC) OA. Many variables determine patient satisfaction with treatment; expectations being fulfilled, relief of pain or symptoms, and the restoration of hand function are the most important determinants. Evaluation of the outcomes of conservative and surgical management in patients with TMC OA showed that surgery leads to significantly improved hand function after one year, while conservative treatment is most effective in the first 6 months. From an economic point of view, surgery is associated with considerably higher costs than conservative treatment, with respect to both healthcare costs and loss of productivity.UBL - phd migration 201