Radiopaque scales have numerous uses in the field of surgery, especially orthopaedic surgery. Scales of this nature can be used to guide surgeons by taking intra-operative measurements, pinpoint insertion points on bones and detect locations of deformations and tumours inside the body. Despite this, these scales are not used widely enough because of its high cost and that there are no widely acceptable ways of developing them from off the shelf materials. This paper details the method of inventing a novel low-cost radiopaque scale using off the shelf materials such as Barium Sulfate and Iodinated Contrast Agent (ICA). The radiopaque scale was manufactured using Perspex ® and was filled with the contrast agents. The scales were then scanned using low-dose X-ray machines. The scale filled with Barium was found to be provide a better contrast image suggesting that the Barium to be a better high-contrast agent when compared to iodine and is recommended for use.

The American Board of Orthopaedic Surgery has mandated dedicated skills training for first-year orthopedic surgical residents. 1 Most residency programs address this requirement with training exercises with cadavers and plastic foam bones. Some programs incorporate one or more simulators in their skills training, including several sophisticated virtual reality simulators and a variety of low-tech simulators. Simulators are helpful because they can provide repeatable educational experiences and quantitative performance assessment. Unfortunately, few simulators have been developed for orthopedic trauma skills training. Even fewer simulators have been developed and validated with more advanced students, such as residents in their 3 rd or 4 th year of training, and for more complex surgeries. In contrast to the completely virtual surgical simulation using haptic feedback devices and sophisticated renderings of soft tissue deformation, our group has chosen to use physical models, real surgical instruments and position tracking in conjunction with virtual reality. 2–4 The physical models provide experience with the surgical tools, and enable more realistic hand movements and haptic cue feedback.

A Stellite 25 17mm tube valve based upon the Björk-Shiley Monostrut (BSM) valve design was developed for use in the Penn State Pediatric Ventricular Assist Device (PVAD) pump [1]. The hook of the valve was designed to hold a Delrin occluding disc in place while allowing the disc to tilt open 70 degrees from the closed position. Unlike common design constraints which remain in the elastic region, the hook experiences plastic deformation twice during the assembly process, making the material choice of Stellite 25 imperative. Stellite 25 is a cobalt-chromium-tungsten-nickel alloy (Co-20Cr-15W-10Ni) belonging to the material family of superalloys which are commonly used for wear-resistant applications exposed to heat, abrasion, and galling [2, 3]. Along with its excellent in vivo corrosion resistance [4], Stellite 25 exhibits high strength and ductility which permit the hook to be plastically deformed during disc installation while remaining below the strain to failure [3, 4]. Together these qualities make Stellite 25 an ideal material choice for the 17mm tube valve application. Predicting the resultant stresses and strains is critical for determining the safety and structural reliability of the Stellite 25 17mm tube valve for the PVAD after assembly. After performing finite element analysis (FEA), the simulation results were validated by deflection experiments and metallurgical investigations.

Intracerebral Hemorrhage (ICH) is the deadliest form of stroke and occurs when blood, leaked from a ruptured vessel pools in the brain forming a pool of semi-coagulated blood called a hematoma. 1 in 50 people will have an ICH in their lifetime [1] and the 30-day mortality rate is 43% with half of the deaths occurring in the acute phase, which motivates the need for safe and rapid treatment. However, literature reviews show no significant benefit of surgical removal vs. “watchful waiting”, despite the potential value of decompressing the brain. It has been hypothesized that this is due to the significant disruption of healthy brain tissue required to reach the hemorrhagic site in open brain surgery. Recent studies conducted on phantom models have shown that a robotic needle made from curved, concentric, elastic tubes can reach a hemorrhagic site through a needle-sized path to successfully aspirate the hematoma. This approach has the potential to decompress the brain with far less disruption to surrounding brain tissue [4]. Those initial experiments were conducted under guidance from periodic (low rate) CT [2]. The need for intraoperative imaging was motivated by the fact that the brain shifts during aspiration, collapsing to fill the cavity left by voided blood. This approach has the potential advantage of “one stop shopping”, since ICH is typically diagnosed in the CT scanner. It is appealing to treat ICH immediately after diagnosis, while the patient is still in the scanner. However, CT also has the drawback of requiring ionizing radiation, as well as providing only intermittent images rather than real-time information. In this paper, we consider a Magnetic Resonance Imaging (MRI) guided approach, which provides the converse in terms of both benefits and drawbacks. MRI is not typically used to diagnose ICH, but it can provide detailed soft-tissue and hematoma contrast [3], and fast image updates, enabling real-time monitoring of brain deformation during the aspiration process. Toward performing ICH aspiration with a concentric tube robot in an MRI environment, this paper presents accuracy and MR-compatibility tests for a new MR-compatible robot designed for ICH removal.

Tissue crush injuries are more prevalent with laparoscopic surgery than open [1]. Injuries may become more frequent in robotic surgery, because force is often only evaluated by the visual deformation of the tissue [2]. A proposed solution by Sie et al. to mitigate these surgical errors is to create tissue-aware graspers which can be incorporated into existing surgical robots, such as the da Vinci [3]. Stephens et al. created a tissue-aware grasper using backend sensing on a da Vinci Si tool [4]. However, tissue identification can be further improved through properly understanding a dynamic da Vinci tool model. Therefore, instrumentation that can accurately and fully characterize existing robotic tools is needed. Various tool calibration set-ups have been created such as [5], which are not portable and often neglect dynamic ranges. The goal of this paper is to present a portable device that shows promise in capturing the dynamic range for da Vinci Si tools.

Living tissue engineered heart valves (TEHV) may circumvent ongoing problems in pediatric valve replacements, offering optimum hemodynamic performance and the potential for growth, remodeling, and self-repair [1]. Although a myriad of external stimuli are available in current bioreactors (e.g. oscillatory flows, mechanical conditioning, etc.), there remain significant bioengineering challenges in determining and quantifying parameters that lead to optimal ECM development and structure for the long term goal of engineering TEHVs exhibiting tissue architecture functionality equivalent to native tissue. It has become axiomatic that in vitro mechanical conditioning promotes engineered tissue formation (Figure 1), either in organ-level bioreactors or in tissue-level bioreactors with idealized-geometry TE constructs. However, the underlying mechanisms remain largely unknown. Efforts to date have been largely empirical, and a two-pronged approach involving novel theoretical developments and close-looped designed experiments is necessary to reach a better mechanistic understanding of the cause-effect interplay between MSC proliferation and differentiation, newly synthetized ECM, and tissue formation, in response to the controllable conditions such as scaffold design, oxygen tension, nutrient availability, and mechanical environment during incubation. We thus evaluate the influence of exterior flow oscillatory shear stress and dynamic mechanical conditioning on the proliferative and synthetic behavior of MSCs by employing a novel theoretical framework for TE. We employ mixture theory to describe the evolution of the biochemical constituents of the TE construct and their intertwined biochemical reactions, evolving poroelastic models to evaluate the enhancement of nutrient transport occurring with dynamic mechanical deformations, and computational fluid dynamics (CFD) to assess the exterior flow boundary conditions developed in the flex-stretch-flow (FSF) bioreactor [4–6].

Statistical Shape Modeling (SSM) is a powerful tool to capture the shape variation pattern across a group of shapes belonging to a certain shape class. SSM has seen many promising applications for the purpose of building Patient-Specific Model (PSM) because it avoids unwanted exposure to ionizing radiation from imaging modalities such as CT scanning and has potential as a cost-saving and time-efficient research and clinical tool. All that is needed to reconstruct the patient — specific data is to instantiate the statistical model already generated. The utility of the statistical model relies on a sufficiently large training set data pool from as many patients as possible; and more importantly, a reasonably good correspondence across the entire training set. As such, the description length has been used as a standard to measure the quality of correspondence and the statistical model, and the desired correspondence found by optimization. However, the previously proposed optimization schemes are too inefficient to be used for large data sets. We present a new optimization scheme based on B-spline freeform deformation and analytical adjoint sensitivity. This scheme is significantly more efficient in that it makes use of: 1) extraordinary efficiency of direct correspondence manipulation; 2) availability of analytical gradient due to the differentiable shapes and correspondence manipulation; 3) superiority of adjoint method when a large number of design variables are used in optimization. In the experimental part, we compare the efficiency of our method and current method for some benchmark examples where solutions are known. Additionally, we show the statistical models for a 3D distal femur bone training set. Such models have been previously used in osteosarcoma cases as a bone bank for bone allografts, where shape-matching is very important [1]. The graphical illustration of the training set and preliminary results of the obtained statistical modes are displayed in Figure 1, 2, 3, 4 and 5.

Many surgeons have come to view mitral valve (MV) repair as the treatment of choice in patients with mitral regurgitation (MR) [1]. According to recent long-term studies, the recurrence of significant MR after repair may be much higher than previously believed, particularly in patients with (ischemic mitral regurgitation) IMR [2]. We hypothesize that the restoration of homeostatic normal MV leaflet tissue stress in IMR repair techniques ultimately leads to improved repair durability. Therefore, the objective of this study is to develop a novel micro-anatomically accurate 3D finite element (FE) model that incorporates detailed collagen fiber architecture, accurate constitutive models, and micro-anatomically realistic valvular geometry to investigate the functional mitral valve and to aid in the assessment of the mitral valve repairs, especially the linking between the interstitial cellular deformations at the cellular level, the mechanobiological behaviors at the tissue level and the organ level mechanical responses as normal and repaired mitral valves maintaining their homeostatic state.

Validating the in vivo performance of implantable medical devices requires robust computational models that utilize appropriate loading and boundary conditions to represent in vivo conditions. Fatigue safety factors derived from computational models are most meaningful when they are based on material life data obtained from physiologically relevant test conditions of samples with similar process and deformation histories. In this paper, we present selected results that leverage novel experimental techniques that we have used to design robust implant components and develop effective test methods to guarantee they will resist fatigue.

The application of Finite Element Modelling in Medical Applications has been evolving as the field of high importance especially in the development of medical devices. The Total Knee Arthroplasty [TKA] has been in existence for over 6 decades till now. The generic artificial knee implants used in the TKA have the restriction in its range of motion with around 90 degrees. A new design allowing flexion extension range of over 120 degrees was designed with a view to facilitate partial squatting and the same is used for the analysis purpose. The new design of the artificial knee has a flexion extension range of 130 degrees. The higher flexion of the knee is obtained by use of the rotating platform knee design principle and also by adopting a multi-radii approach for the femoral component design. The loading conditions of 10 times the body weight are considered for structural analyses of the novel knee. A maximum load of 700Kg were subjected on the knee implants. The finite element analyses of the designs were carried out based on standard biomaterial used in orthopedic implants. In this paper we have discussed the results of analyses of an artificial knee with Ti alloy. The results of the analyses were used in identifying areas of extreme stresses within the design and the spot prone for higher deformation. Based on these results slight modification on the designs was carried out. The results are also verified whether the body is within the linear deformation levels. As the results obtained were very satisfactory the models have been recommended for prototyping.

PLLA is a commonly used biodegradable polymer in stent designs because it is non-toxic and easily eliminated from the body. However, very little is known about the effect of loading conditions on the degradation rate. Rajagopal and Wineman developed a model of polymer degradation which is driven by load applied to the fiber [1]. Soares et. al. further developed this model for use with PLLA stent fibers under tensile loading conditions [2]. In this model the degradation rate is linearly related to deformation through the radius in the (I B , II B ) plane. Both models predict that greater deformation will induce a higher degree of degradation.

Stents are most commonly used in the relief of coronary artery stenosis, but in the last decade have found increasing applications in the treatment of other cardiovascular disease and in particular in heart valve replacement [1]. In transcatheter valve implantation, acquisition of high temporal and spatial resolution images during stenting procedure and patients’ follow-up is required to help the correct positioning of the device and to assess the mechanical performance over time. The imaging techniques routinely used for this purpose are 2D X-ray fluoroscopy and 3D computed tomography (CT), and recent studies have demonstrated their value as diagnostic tools [1–3]. However, these image modalities carry errors and the resulting information might not be accurate enough to be employed in engineering analyses of stent deformations, mechanics, dynamics and fracture. In this study, we aim to evaluate the errors of conventionally used clinical images (fluoroscopy and CT) and post-processing by comparison with ultra-high resolution micro-CT (μCT) as gold standard. Additionally, an optical image acquisition method and a high-radiation CT scan were evaluated as potential techniques to acquire geometrical data that could be used for computational and in-vitro engineering experiments.

Constitutive modeling is critical for numerical simulation and analysis of soft biological tissues. The highly nonlinear and anisotropic mechanical behaviors of soft tissues are typically due to the interaction of tissue microstructure. By incorporating information of fiber orientation and distribution at tissue microscopic scale, the structural model avoids ambiguities in material characterization. Moreover, structural models produce much more information than just simple stress-strain results, but can provide much insight into how soft tissues internally reorganize to external loads by adjusting their internal microstructure. It is only through simulation of an entire organ system can such information be derived and provide insight into physiological function. However, accurate implementation and rigorous validation of these models remains very limited. In the present study we implemented a structural constitutive model into a commercial finite element package for planar soft tissues. The structural model was applied to simulate strip biaxial test for native bovine pericardium, and a single pulmonary valve leaflet deformation. In addition to prediction of the mechanical response, we demonstrate how a structural model can provide deeper insights into fiber deformation fiber reorientation and fiber recruitment.

There are a range of physiological movements such as knee and hip flexion that result in the deformation and loading of the femoropopliteal artery, characterised as axial compression, radial compression, bending and torsion [1]. The SFA is a prevalent location for peripheral arterial disease often requiring percutaneous transluminal angioplasty followed by stenting to restore vessel patency and uncompromised blood flow. Whilst stent placement provides the required scaffolding of the artery, opening up blockages and preventing elastic recoil of the vessel, it alters axial rigidity, changing the way in which the vessel deforms. With extreme stent rigidity and long stent lengths, severe bending can occur in the unstented vessel portions, proximal and distal to the stent. This has been observed in angiographic images of stented vessels that show unstented artery portions bending in an exaggerated manner adjacent to stented regions [2, 3]. It is postulated that due to knee flexion, deformation characteristics of the vessel are changed with extreme curvatures induced, initiating large stresses in the vessel tissue which may contribute to vascular injury, intimal hyperplasia and restenosis [2]. The goal of this work was to determine the effect of stent placement on deformation characteristics of the SFA after knee flexion using an anatomically accurate, three dimensional finite element model of the leg. Deformation characteristics (length change, curvature change and axial twist) that result from knee flexion movements of the stented vessel are quantified and linked with stress and strain levels within the artery for various cases of stent length and location within the femoropopliteal artery.

Flow phantoms are used to simulate and study the cardiovascular system, associated disease states and boundary conditions. A flow phantom reproduces the flow and pressure of a portion of the vascular system for use in bench top studies of the effect of different changes or devices on the pressure response and deformation of the vessels.

Compliant mechanisms are flexible devices that transform an input force to a displacement through elastic deformation. Advantages of using compliant mechanisms are that they are monolithic devices that contain flexible members that can undergo large deflection, have fewer joints, have increased reliability, increased precision and have fewer components compared to rigid-body mechanisms.

Lack of detailed stent artery interactions is responsible for rampant stent fracture in the human SFA or popliteal arteries. Armed with recent research work quantifying dynamic changes of the SFA and popliteal vessels, we investigated stent deformations under various modes of dynamic physiological conditions and their interactions using realistic artery constitutive models. Fatigue strains were calculated using finite element analysis and were compared with material’s endurance limit data obtained using a special V-shape sample. A linear damage accumulation formula (Minor’s rule) was employed to predict safety factors for the stent.

For centuries, surgeons have heavily relied on scalpels and sutures to reshape cartilage. Reshaping the cartilaginous frameworks of the head and neck requires open surgery to counteract the intrinsic elastic forces that resist deformation. Recently, non-surgical techniques that use radio frequency or laser sources to reshape cartilage have been developed, but they rely on heat generation and may produce thermal injury [1,3]. We recently developed new techniques to reshape cartilage called Electro-Mechanical Reshaping ( EMR ) that combines mechanical deformation with the application of low-level DC electric fields. Shape change is driven by electrochemical reactions that occur between electrodes placed in contact with the mechanically deformed specimen. Previous studies have shown that EMR of cartilage can be accomplished using graphite and aluminum surface electrodes [2,4]. In this study, EMR was further investigated with the use of needle electrodes that can be inserted into the mechanically deformed specimen rather than on the surface. Needle electrodes offer several advantages to surface electrodes because they can be incorporated into percutaneous surgical devices and instrumentation, deliver electric energy precisely to the site of desired shape change, and by design limit the spatial extent of tissue injury.

A modified Mach-Zender set-up in reflection is applied to record and reconstruct holographic amplitude and phase images. A charged couple device (CCD) is used to record a hologram and numerical reconstruction algorithms are then applied to rebuild the hologram for obtaining both phase and amplitude information. One could also focus on multiple focal planes from a single hologram, similar to the focusing control of a conventional microscope. The morphology and behavior of mammalian cells is determined by an interaction between signals from the intracellular matrix and the cellular responses. It is important to note that the physical aspect of the extracellular matrix is as significant as the chemical nature of it. Specifically the stresses, mechanical forces, and the profile of the external environment have major effects on cell behavior. The mechanical and physical characteristics of a tissue are greatly dependent on a hierarchical spatial arrangement of its extra-cellular matrix components. A key player in the ECM is collagen which exhibits significant tensile strength on the cellular scale. Digital holographic microscopy (DHM) is applied to study the deformation of collage matrix in response to cell migration.

We sought to determine the effects of head rotation, lateral neck flexion, and traction force on brachial plexus (BP) nerve strain, specifically at C5-C6 (Erb’s point), and C7, C8, and T1 roots in a multi-“filament” 3D model of the fetal BP. Using our constructed simulator and a tailored data acquisition system, strain readings were recorded and accurate to within <2%. Using our model and a position-sensing system, controlled loads and deformations were applied to a fetal head attached to a flexible spine. For each simulation, we measured BP strain at Erb’s point, and C7, C8, and T1 roots. Increasing total traction force increases strain in the upper and middle nerves (Erb’s point, C7, and C8). Lateral neck flexion produces the most strain (up to 25.4±6.6% in Erb’s point with 4.5 kg (10 lbs) of traction), with concomitant head rotation magnifying strain levels by up to a factor of 1.7. Increasing head rotation and lateral neck flexion increases the strain in the lower nerve roots more than in the upper roots. in general, upper nerves undergo double the strain of lower nerves. Direct axial traction has the least effect, with 4.5 kg of traction producing a peak strain of 3.6±2.5% at Erb’s point. BP strain can be reduced at Erb’s point, C7, and C8 by maintaining neutral alignment between the head and trunk prior to applying traction, which should be minimized.