Biomechanics

Biomechanics is a vast discipline within the field of Biomedical Engineering. It explores the underlying mechanics of how biological and physiological systems move. It encompasses important clinical applications to address questions related to medicine using engineering mechanics principles. Biomechanics includes interdisciplinary concepts from engineers, physicians, therapists, biologists, physicists, and mathematicians. Through their collaborative efforts, biomechanics research is ever changing and expanding, explaining new mechanisms and principles for dynamic human systems. Biomechanics is used to describe how the human body moves, walks, and breathes, in addition to how it responds to injury and rehabilitation. Advanced biomechanical modeling methods, such as inverse dynamics, finite element analysis, and musculoskeletal modeling are used to simulate and investigate human situations in regard to movement and injury. Biomechanical technologies are progressing to answer contemporary medical questions. The future of biomechanics is dependent on interdisciplinary research efforts and the education of tomorrow’s scientists

Identification of hip fracture patients from radiographs using Fourier analysis of the trabecular structure: a cross-sectional study

Peer reviewedPublisher PD

Fracture of the tibial baseplate in bicompartmental knee arthroplasty

Introduction. Bicompartmental knee arthroplasty (BKA) addresses combined medial and patellofemoral compartment osteoarthritis, which is relatively common, and has been proposed as a bridge between unicompartmental and total knee arthroplasty (TKA). Case Presentation. We present the case report of a young active man treated with BKA after unsuccessful conservative therapy. Four years later, loosening with fracture of the tibial baseplate was identified and the patient was revised to TKA. Discussion. Although our case is only the second fractured tibial baseplate to be reported, we believe that the modular titanium design, with two fixation pegs, is too thin to withstand daily cyclic loading powers. Light daily routine use, rather than high-impact sports, is therefore advised. Failures may also be related to the implant being an early generation and known to be technically complex, with too few implant sizes. We currently use TKA for the treatment of medial and patellofemoral compartment osteoarthritis

MedEdit : a computer assisted image processing and navigation system for orthopedic trauma surgery

The surgery of fractured bones is often a very complex problem. That is the reason why it would be beneficial to create a geometric and mechanic model of the bones before surgical intervention. The model geometry is based on the CT images of the patient and the known physical properties of the bone. A computerised system is presented here, called MedEdit, which helps a surgeon plan an operation. The system includes a Finite Element Analysis (FEA) program to measure the stress effects of the possible surgical solutions. Following the simulation and analysis of the behaviour of the modelled bone, surgeons can find the best surgical solution for the patient

Phase-field modeling of brittle fracture with multi-level hp-FEM and the finite cell method

The difficulties in dealing with discontinuities related to a sharp crack are overcome in the phase-field approach for fracture by modeling the crack as a diffusive object being described by a continuous field having high gradients. The discrete crack limit case is approached for a small length-scale parameter that controls the width of the transition region between the fully broken and the undamaged phases. From a computational standpoint, this necessitates fine meshes, at least locally, in order to accurately resolve the phase-field profile. In the classical approach, phase-field models are computed on a fixed mesh that is a priori refined in the areas where the crack is expected to propagate. This on the other hand curbs the convenience of using phase-field models for unknown crack paths and its ability to handle complex crack propagation patterns. In this work, we overcome this issue by employing the multi-level hp-refinement technique that enables a dynamically changing mesh which in turn allows the refinement to remain local at singularities and high gradients without problems of hanging nodes. Yet, in case of complex geometries, mesh generation and in particular local refinement becomes non-trivial. We address this issue by integrating a two-dimensional phase-field framework for brittle fracture with the finite cell method (FCM). The FCM based on high-order finite elements is a non-geometry-conforming discretization technique wherein the physical domain is embedded into a larger fictitious domain of simple geometry that can be easily discretized. This facilitates mesh generation for complex geometries and supports local refinement. Numerical examples including a comparison to a validation experiment illustrate the applicability of the multi-level hp-refinement and the FCM in the context of phase-field simulations

Unveiling the prospects of point-of-care 3D printing of Polyetheretherketone (PEEK) patient-specific implants

Additive manufacturing (AM) or three-dimensional (3D) printing is rapidly gaining acceptance in the healthcare sector. With the availability of low-cost desktop 3D printers and inexpensive materials, in-hospital or point-of-care (POC) manufacturing has gained considerable attention in personalized medicine. Material extrusion-based [Fused Filament Fabrication (FFF)] 3D printing of low-temperature thermoplastic polymer is the most commonly used 3D printing technology in hospitals due to its ease of operability and availability of low-cost machines. However, this technology has been limited to the production of anatomical biomodels, surgical guides, and prosthetic aids and has not yet been adopted into the mainstream production of patient-specific or customized implants. Polyetheretherketone (PEEK), a high-performance thermoplastic polymer, has been used mainly in reconstructive surgeries as a reliable alternative to other alloplastic materials to fabricate customized implants. With advancements in AM systems, prospects for customized 3D printed surgical implants have emerged, increasing attention for POC manufacturing. A customized implant may be manufactured within few hours using 3D printing, allowing hospitals to become manufacturers. However, manufacturing customized implants in a hospital environment is challenging due to the number of actions necessary to design and fabricate the implants. The focus of this thesis relies on material extrusion-based 3D printing of PEEK patient-specific implants (PSIs). The ambitious challenge was to bridge the performance gap between 3D printing of PEEK PSIs for reconstructive surgery and the clinical applicability at the POC by taking advantage of recent developments in AM systems. The main reached milestones of this project include: (i) assessment of the fabrication feasibility of PEEK surgical implants using material extrusion-based 3D printing technology, (ii) incorporation of a digital clinical workflow for POC manufacturing, (iii) assessment of the clinical applicability of the POC manufactured patient-specific PEEK scaphoid prosthesis, (iv) visualization and quantification of the clinical reliability of the POC manufactured patient-specific PEEK cranial implants, and (v) assessment of the clinical performance of the POC manufactured porous patient-specific PEEK orbital implants. During this research work, under the first study, we could demonstrate the prospects of FFF 3D printing technology for POC PEEK implant manufacturing. It was established that FFF 3D printing of PEEK allows the construction of complex anatomical geometries which cannot be manufactured using other technologies. With a clinical digital workflow implementation at the POC, we could further illustrate a smoother integration and faster implant production (within two hours) potential for a complex-shaped, patented PEEK patient-specific scaphoid prosthesis. Our results revealed some key challenges during the FFF printing process, exploring the applicability of POC manufactured FFF 3D printed PEEK customized implants in craniofacial reconstructions. It was demonstrated that optimal heat distribution around the cranial implants and heat management during the printing process are essential parameters that affect crystallinity, and thus the quality of the FFF 3D printed PEEK cranial implants. At this stage of the investigation, it was observed that the root mean square (RMS) values for dimensional accuracy revealed higher deviations in large-sized cranial prostheses with “horizontal lines” characteristics. Further optimization of the 3D printer, a layer-by-layer increment in the airflow temperature was done, which improved the performance of the FFF PEEK printing process for large-sized cranial implants. We then evaluated the potential clinical reliability of the POC manufactured 3D printed PEEK PSIs for cranial reconstruction by quantitative assessment of geometric, morphological, and biomechanical characteristics. It was noticed that the 3D printed customized cranial implants had high dimensional accuracy and repeatability, displaying clinically acceptable morphologic similarity concerning fit and contours continuity. However, the tested cranial implants had variable peak load values with discrete fracture patterns from a biomechanical standpoint. The implants with the highest peak load had a strong bonding with uniform PEEK fusion and interlayer connectivity, while air gaps and infill fusion lines were observed in implants with the lowest strength. The results of this preclinical study were in line with the clinical applicability of cranial implants; however, the biomechanical attribute can be further improved. It was noticed that each patient-specific reconstructive implant required a different set of manufacturing parameters. This was ascertained by manufacturing a porous PEEK patient-specific orbital implant. We evaluated the FFF 3D printed PEEK orbital mesh customized implants with a metric considering the design variants, biomechanical, and morphological parameters. We then studied the performance of the implants as a function of varying thicknesses and porous design constructs through a finite element (FE) based computational model and a decision matrix based statistical approach. The maximum stress values achieved in our results predicted the high durability of the implants. In all the implant profile configurations, the maximum deformation values were under one-tenth of a millimeter (mm) domain. The circular patterned design variant implant revealed the best performance score. The study further demonstrated that compounding multi-design computational analysis with 3D printing can be beneficial for the optimal restoration of the orbital floor. In the framework of the current thesis, the potential clinical application of material extrusion-based 3D printing for PEEK customized implants at the POC was demonstrated. We implemented clinical experience and engineering principles to generate a technical roadmap from preoperative medical imaging datasets to virtual surgical planning, computer-aided design models of various reconstructive implant variants, to the fabrication of PEEK PSIs using FFF 3D printing technology. The integration of 3D printing PEEK implants at the POC entails numerous benefits, including a collaborative team approach, quicker turnaround time of customized implants, support in pre-surgical and intraoperative planning, improved patient outcomes, and decreased overall healthcare cost. We believe that FFF 3D printing of customized PEEK implants could become an integral part of the hospitals and holds potential for various reconstructive surgery applications

Injury Risk Assessment of the Femur in Children with Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a genetic disorder characterized by increased bone fragility and decreased bone mass, which leads to high rates of bone fracture. OI has a prevalence of 1/5,000 to 1/10,000 in the United States. About 90% of persons with OI have a genetic mutation in the coding for collagen type I, which is the major protein of connective tissues, including bone. While its prevalence classifies it as a rare disease, it is the most common disorder of bone etiology. Until recently, little was known about the mechanics and materials of OI bone or their impact on fracture risk. Fracture risk is typically characterized by clinical type and radiographs. Finite element (FE) models have recently been developed to examine fracture risk during ambulation and various daily activities of the femur and tibia in children and adolescents with OI. This research aims to provide further information about the impact of OI in children and adolescents during loading conditions. FE models of the femur with normal bone, OI type I (mild) bone and OI type III (severe) bone material properties were developed and analyzed. These models showed the effects of lateral bowing versus increased gluteus medius and gluteus maximus force production on bone injury risk. Lateral bowing and muscle force increase permutations to the standard model of no bowing and normal muscle forces during ambulation showed significant changes to stress levels. Along with FE models, quantitative gait analyses were performed on 10 children with mild OI and ten age- and gender-matched controls to analyze the firing patterns of the gluteus medius and gluteus maximus muscles during normal ambulation. The OI population exhibited a delay in gluteus maximus activation. Additional FE models examined the impact of creating the model directly from a CT scan of a child with severe OI versus scaling a standard model to match the size and shape of and OI femur based on x-ray images alone. Comparison of these two model geometry development techniques resulted in a significant difference in femoral stresses and strains

Artificial intelligence in orthopaedic surgery

The use of artificial intelligence (AI) is rapidly growing across many domains, of which the medical field is no exception. AI is an umbrella term defining the practical application of algorithms to generate useful output, without the need of human cognition. Owing to the expanding volume of patient information collected, known as ‘big data’, AI is showing promise as a useful tool in healthcare research and across all aspects of patient care pathways. Practical applications in orthopaedic surgery include: diagnostics, such as fracture recognition and tumour detection; predictive models of clinical and patient-reported outcome measures, such as calculating mortality rates and length of hospital stay; and real-time rehabilitation monitoring and surgical training. However, clinicians should remain cognizant of AI’s limitations, as the development of robust reporting and validation frameworks is of paramount importance to prevent avoidable errors and biases. The aim of this review article is to provide a comprehensive understanding of AI and its subfields, as well as to delineate its existing clinical applications in trauma and orthopaedic surgery. Furthermore, this narrative review expands upon the limitations of AI and future direction