Many individuals with lower-limb amputations or neuromuscular impairments face mobility challenges attributable to suboptimal assistive device design. Forward dynamic modelling and simulation of human walking using conventional biomechanical gait models offer an alternative to intuition-based assistive device design, providing insight into the biomechanics underlying pathological gait. Musculoskeletal models additionally enable understanding of prosthesis and/or exoskeleton contributions to the human musculoskeletal system, and device and user contributions to body support and propulsion during gait. This paper reviews current literature that have used forward dynamic simulation of clinical population musculoskeletal models to perform assistive device design optimization using optimal control, optimal tracking, computed muscle control and reflex-based control. Musculoskeletal model complexity and assumptions inhibit forward dynamic musculoskeletal modelling in its current state, hindering computational assistive device design optimization. Future recommendations include validating musculoskeletal models and resultant assistive device designs, developing less computationally-expensive forward dynamical musculoskeletal modelling methods, and developing more efficient patient-specific musculoskeletal model generation methods to enable personalized assistive device optimization.

The task of a powered knee orthotic device (PKOD) is to assist the knee joint so that its natural behavior can be restored. The key features of a PKOD that may help to regain such characteristics are low power consumption, fast response, compactness, and lightweight. This study proposes a novel design of PKOD, where we have focused on the betterment of the mentioned features with the help of a new mechanism, namely a four-bar controlled compliance actuator (FCCA). In FCCA, instead of using the widely used screw transmission mechanism, a four-bar mechanism is used to modify the joint's angular deviation and stiffness. The main advantages of using FCCA over other existing mechanisms are to reduce the power consumption by amplification of input motor torque and to achieve a faster response at the same time, and these are achieved by utilizing a simple four-bar mechanism. In the proposed design, FCCA controls both the stiffness of the artificial knee joint using a compliance mechanism as well as knee flexion with the help of a pulley arrangement. A three-dimensional (3D)-printed prototype of the proposed design has been developed, after optimizing the inherent design parameters. Simulation and experimental analysis are carried out in order to justify the performance of the proposed PKOD. The results have shown strong agreement with that obtained using analytical study and optimization. Moreover, the torque amplification is achieved, as desired.

Bone deformities are often complex three-dimensional (3D) deformities, and correcting them is difficult. To correct persistent clubfoot deformity in adolescents or adults, an external fixator is sometimes used to encourage tissue growth and preserve healthy tissues. However, it is difficult to set up, resulting in long surgeries and steep learning curves for surgeons. It is also bulky and obstructs patient mobility. In this paper, we introduce a new approach of defining clubfoot deformity correction as a six degrees-of-freedom (6DOF) correction, and then reducing it to just two degrees-of-freedom (2DOF) using the axis-angle representation. Therefore, only two physical trajectory joints are needed, which in turn enables a more compact fixator design. A computer planner was developed to minimize the bulk of the external fixator, and to optimize the distraction schedule to avoid overstretching the soft tissues. This reduces the learning curve for surgeons and shortens surgery time. To validate the system, a patient-specific clubfoot simulator was developed, and four experiments were performed on the clubfoot simulator. The accuracy of midfoot correction was 11 mm and 3.5 deg without loading, and 41 mm and 11.7 deg with loading. While the external fixator has to be more rigid to overcome resistance against correction, the surgical system itself was able to achieve accurate correction in less than 2 h. This is an improvement from the current method, which takes 2.5–4.5 h.

Instrument-assisted soft tissue mobilization (IASTM) is a manual therapy technique that is commonly used to treat dysfunctions in ligaments and other musculoskeletal tissues. The objective of this study was to develop a simple hand-held device that helps users accurately apply targeted compressive forces and stroke frequencies during IASTM treatments. This portable device uses a force sensor, tablet computer, and custom software to guide the application of user-specified loading parameters. To measure performance, the device was used to apply a combination of targeted forces and stroke frequencies to foam blocks and silicone pads. Three operators using the device applied targeted forces between 0.3 and 125 N with less than 10% error and applied targeted stroke frequencies between 0.25 and 1.0 Hz with less than 3% error. The mean error in applying targeted forces increased significantly at compressive forces less than 0.2 N and greater than 125 N. For experimental validation, the device was used to apply a series of IASTM treatments over three-weeks to rodents with a ligament injury, and the targeted compressive force and stroke frequency were repeatedly applied with an average error less than 5%. This validated device can be used to investigate the effect of IASTM loading parameters on tissue healing in animal and human studies, and therefore can support the optimization and adoption of IASTM protocols that improve patient outcomes.

Radiofrequency ablation (RFA) is an increasingly used, minimally invasive, cancer treatment modality for patients who are unwilling or unable to undergo a major resective surgery. There is a need for RFA electrodes that generate thermal ablation zones that closely match the geometry of typical tumors, especially for endoscopic ultrasound-guided (EUS) RFA. In this paper, the procedure for optimization of an RFA electrode is presented. First, a novel compliant electrode design is proposed. Next, a thermal ablation model is developed to predict the ablation zone produced by an RFA electrode in biological tissue. Then, a multi-objective genetic algorithm is used to optimize two cases of the electrode geometry to match the region of destructed tissue to a spherical tumor of a specified diameter. This optimization procedure is then applied to EUS-RFA ablation of pancreatic tissue. For a target 2.5 cm spherical tumor, the optimal design parameters of the compliant electrode design are found for two cases. Cases 1 and 2 optimal solutions filled 70.9% and 87.0% of the target volume as compared to only 25.1% for a standard straight electrode. The results of the optimization demonstrate how computational models combined with optimization can be used for systematic design of ablation electrodes. The optimization procedure may be applied to RFA of various tissue types for systematic design of electrodes for a specific target shape.

This paper presents design optimization of a magnetic resonance imaging (MRI) actuated steerable catheter for atrial fibrillation ablation in the left atrium. The catheter prototype, built over polymer tubing, is embedded with current-carrying electromagnetic coils. The prototype can be deflected to a desired location by controlling the currents passing through the coils. The design objective is to develop a prototype that can successfully accomplish the ablation task. To complete the tasks, the catheter needs to be capable of reaching a set of desired targets selected by a physician on the chamber and keeping a stable contact with the chamber surface. The design process is based on the maximization of the steering performance of the catheter by evaluating its workspace in free space. The selected design is validated by performing a simulation of an ablation intervention on a virtual model of the left atrium with a real atrium geometry. This validation shows that the prototype can reach every target required by the ablation intervention and provide an appropriate contact force against the chamber.

The total product life cycle (TPLC) of medical devices has been defined by four stages: discovery and ideation, regulatory decision, product launch, and postmarket monitoring. Manufacturers of medical devices intended for use in the peripheral vasculature, such as stents, inferior vena cava (IVC) filters, and stent-grafts, mainly use computational modeling and simulation (CM&S) to aid device development and design optimization, supplement bench testing for regulatory decisions, and assess postmarket changes or failures. For example, computational solid mechanics and fluid dynamics enable the investigation of design limitations in the ideation stage. To supplement bench data in regulatory submissions, manufactures can evaluate the effects of anatomical characteristics and expected in vivo loading environment on device performance. Manufacturers might also harness CM&S to aid root-cause analyses that are necessary when failures occur postmarket, when the device is exposed to broad clinical use. Once identified, CM&S tools can then be used for redesign to address the failure mode and re-establish the performance profile with the appropriate models. The Center for Devices and Radiological Health (CDRH) wants to advance the use of CM&S for medical devices and supports the development of virtual physiological patients, clinical trial simulations, and personalized medicine. Thus, the purpose of this paper is to describe specific examples of how CM&S is currently used to support regulatory submissions at different phases of the TPLC and to present some of the stakeholder-led initiatives for advancing CM&S for regulatory decision-making.

Robotic total hip arthroplasty is a procedure in which a milling operation is performed on the femur followed by insertion of a prosthetic implant. Although surgeons operate the robots, they do not control the choice of robotic tools and cutting strategies of the robot. Toolpath parameters, such as feedrate, tool geometry, and spindle speeds, govern the cutting forces of the robot. This research covers a methodological approach for finding optimal parameters such that cutting forces and surgical times are reduced. Many different types of orthopedic surgical burs were retrofitted into an advanced computer numerically controlled (CNC) machine, and the characteristics of each tool were evaluated. A simulation cutting model was then developed to find the parameters that could remove the most material in the fastest amount of time without violating any of the safety constraints of surgery. The new methodology proposed not only finds the theoretical optimal parameters but also expedites the process of finding sufficient parameters for orthopedic surgery.

Stent geometries are obtained by topology optimization for minimized compliance under different stenosis levels and plaque material types. Three levels of stenosis by cross-sectional area, i.e., 30%, 40%, and 50% and three different plaque material properties, i.e., calcified, cellular, and hypocellular, were studied. The raw optimization results were converted to clear design concepts and their performance was evaluated by implanting them in their respective stenosed artery types using finite element analysis. The results were compared with a generic stent in similar arteries, which showed that the new designs showed less recoil. This work provides a concept that stents could be tailored to specific lesions in order to minimize recoil and maintain a patent lumen in stenotic arteries.

Stroke is one of the leading causes of adult physical disability, and rehabilitation and hospitalization costs for stroke are among the highest for all injuries. Current rehabilitation techniques are labor intensive and time consuming for therapists and difficult to perform effectively. Research suggests that starting rehabilitation during the acute or subacute stage of recovery results in better outcomes than therapy delivered in the chronic stage. To improve the gait rehabilitation process, robot-assisted gait rehabilitation has gained much interest over the past years. However, many robot-assisted rehabilitation devices have limitations; one of which is being bulky and complex to handle. Large and expensive devices that require special training to operate are less attractive to clinics and therapists, and ultimately less likely to be available to patients especially at the early stage of stroke. To address these limitations, this research proposes a new gait rehabilitation device called the linkage design gait trainer (LGT). The device is based on a walking frame design with a simple four-bar linkage “end-effector” mechanism to generate normal gait trajectories during general walking and exercise. The design of the four-bar linkage mechanism was optimized for a particular gait pattern. A prototype of the device was developed and tested. The kinematics of the device itself and gait kinematics with and without assistance from the device were recorded and analyzed using an optical motion capture system. The results show the linkage mechanism is able to guide the leg of the user during over ground walking. There were some differences in the hip (20.5 deg RMS) and knee (14.8 deg RMS) trajectory between the person walking with and without the device assistance. The study demonstrated the concept and feasibility of this novel gait training device.

Due to the need of high-speed and efficient biodosimetric assays for triage and therapy in the event of radiological or nuclear attack, a robotically based automated biodosimetry tool (RABiT) has been developed over the past few years. Adapting the micronucleus assay from filter plates to V-shaped plates presented challenges in the liquid handling, namely, cell splashing out of the V-shaped well plate during the cell harvesting, poor cell distribution on the bottom of the image plate during the dispensing, and cell loss from the image plate during the aspiration in the liquid handling process. Experimental and numerical investigations were carried out to better understand the phenomena and mitigate the problems. Surface tension and contact angle among the fluids and the plate wall were accounted for in the discrete and multiphase numerical models. Experimental conditions were optimized based on the numerical results showing the relationship between nozzle speed and amount of splashed liquid, and the relationship between aspiration speed and number of escaped cells. Using these optimized parameters, numbers of micronuclei in binucleated cells showed the same dose dependence in the RABiT-prepared samples as those in the manually prepared ones. Micronucleus assay protocol was fully realized on RABiT.

The accuracy of many freehand medical procedures can be improved with assistance from real-time localization. Magnetic localization systems based on harnessing passive permanent magnets (PMs) are of great interest to track objects inside the body because they do not require a powered source and provide noncontact sensing without the need for line-of-sight. While the effect of the number of sensors on the localization accuracy in such systems has been reported, the spatial design of the sensing assembly is an open problem. This paper presents a systematic approach to determine an optimal spatial sensor configuration for localizing a PM during a medical procedure. Two alternative approaches were explored and compared through numerical simulations and experimental investigation: one based on traditional grid configuration and the other derived using genetic algorithms (GAs). Our results strongly suggest that optimizing the spatial arrangement has a larger influence on localization performance than increasing the number of sensors in the assembly. We found that among all the optimization schemes, the approach utilizing GA produced sensor designs with the smallest localization errors.

This article studies the design of passive elastic elements to reduce the actuator requirements for powered ankle prostheses. The challenge is to achieve most of the typically nonlinear ankle response with the passive element so that the active ankle-torque from the actuator can be small. The main contribution of this article is the design of a cam-based lower-limb prosthesis to achieve such a nonlinear ankle response. Results are presented to show that the addition of the cam-based passive element can reduce the peak actuator torque requirement substantially, by ∼74%. Moreover, experimental results are presented to demonstrate that the cam-based design can achieve a desired nonlinear response to within 10%.

Bone transport distraction osteogenesis (BTDO) is a surgical procedure that has been used over the last 30 years for the correction of segmental defects produced mainly by trauma and oncological resections. Application of BTDO has several clinical advantages over traditional surgical techniques. Over the past few years, several BTDO devices have been introduced to reconstruct mandibular bone defects. Based on the location and outline of the defect, each device requires a uniquely shaped reconstruction plate. To date, no biomechanical evaluations of mandibular BTDO devices have been reported in the literature. The present study evaluated the mechanical behavior of three different shaped prototypes of a novel mandibular bone transport reconstruction plate and its transport unit for the reconstruction of segmental bone defects of the mandible by using numerical models complemented with mechanical laboratory tests to characterize strength, fatigue, and stability. The strength test evaluated device failures under extreme loads and was complemented with optimization procedures to improve the biomechanical behavior of the devices. The responses of the prototypes were characterized to improve their design and identify weak and strong regions in order to avoid posterior device failure in clinical applications. Combinations of the numerical and mechanical laboratory results were used to compare and validate the models. In addition, the results remark the importance of reducing the number of animals used in experimental tests by increasing computational and in vitro trials.

This paper presents an implantable device concept with applications for treating ocular diseases such as glaucoma, age-related macular degeneration (AMD), diabetic retinopathy, and retinitis pigmentosa. The design of a biodegradable drug delivery device concept consisting of a polydimethylsiloxane (PDMS) shell with a fluid reservoir and micro/nanofluidic tubes that allow the drug to be stored and delivered at a specified rate is discussed. Computational fluid dynamics simulations were conducted through various tube configurations in order to obtain the drug diffusion characteristics. The results from the simulation studies revealed information related to drug transport under varying design parameters. The design simulations were conducted with a desired rate. Based on results from several simulations, an optimization study was conducted to achieve the required dosage for about 2 years. The results obtained from the optimization study shows that the device concept can be extended for different drugs to treat ocular diseases.