Hip | EPFL Graph Search

In vertebrate anatomy, hip (or coxa in medical terminology; : coxae) refers to either an anatomical region or a joint. The hip region is located lateral and anterior to the gluteal region, inferior to the iliac crest, and overlying the greater trochanter of the femur, or "thigh bone". In adults, three of the bones of the pelvis have fused into the hip bone or acetabulum which forms part of the hip region. The hip joint, scientifically referred to as the acetabulofemoral joint (art. coxae), is the joint between the head of the femur and acetabulum of the pelvis and its primary function is to support the weight of the body in both static (e.g., standing) and dynamic (e.g., walking or running) postures. The hip joints have very important roles in retaining balance, and for maintaining the pelvic inclination angle. Pain of the hip may be the result of numerous causes, including nervous, osteoarthritic, infectious, traumatic, and genetic. Structure Region The hip

Contact modeling and collision detection in human joints

Ehsan Arbabi

Collision detection among virtual objects is one of the main concerns in virtual reality and computer graphics. Usually the methods developed for collision detection are for either very general cases or very specific applications. The first main goal of this thesis is to propose accurate methods for collision detection in computer graphics for rotating or sliding objects. The methods take advantage of the limitation imposed on the rotating/sliding objects in order to ignore unnecessary calculations of the general methods and speed up the processing. In addition to finding the collision, the methods can also return penetration depths in either radial or cylindrical direction, which can be useful for further applications. The second main goal is to apply the proposed collision detection methods in biomedical research related to human hip joints. In fact, during the past few years, femoroacetabular impingement (FAI) was recognized as the leading pathomechanism contributing to a significant number of so-called "primary" hip osteoarthritis. Thus, having medical simulation of hip joint can help both physicians and surgeons for better diagnosis and surgical planning. For diagnosing some of the human joint diseases, it is important to obtain the joint's range of motion. By modifying the pre-processing stage of one of the collision detection methods, a new fast method for finding maximum range of motion in human joint was proposed and tested. The method is working without doing any collision detection tests and its accuracy does not depend on the rotational steps. We also suggested a novel fast strategy for diagnosing hip diseases based on hip contact penetration depths. In this strategy, the contact penetration depths during hip movement are calculated for diagnosing hip impingements, by using the proposed collision detection methods. The strategy has been tested on pathological hip models during a daily activity. The results were found correlated with the contact stresses estimated by finite element method (FEM). By evaluating the results, the strategy proved to be capable for distinguishing among different hip pathologies (e.g. cam and pincer impingements). In orthopedic simulations, the behavior of the bones and the related tissues are usually investigated during their movements about an estimated center of rotation. We also evaluated the importance of the hip joint center of rotation in medical simulations. For this reason, different centers of rotation calculated by five different methods were applied for hip movements about different medical axes of rotation. By calculating the hip contact penetration depths of ten patients during hip movements (using the proposed collision detection methods), the sensitivity of hip simulations to hip center of rotation has been evaluated. Hip contact pressure has been a notable parameter to evaluate the physical conditions inside the hip joint. Many computational approaches estimate the pressure and contact pressures via finite element methods (FEM) by using 3D meshes of the tissues. Although this type of simulation can provide a good evaluation of hip problems, the process may be very time consuming. Also, these mechanical methods strongly depend on the movement details. We proposed and tested a fast statistical model for estimating hip contact pressures during its movement, without performing mechanical simulations and without any need for movement details. The estimation is done by evaluating geometric features extracted from 3D meshes of hip tissues, in order to link an unknown target hip model to some already mechanically evaluated training hip models.

EPFL2009

Wearable exoskeletons to support ambulation in people with neuromuscular diseases, design rules and control

Amalric Louis Ortlieb

Neuromuscular diseases are degenerative and, thus far, incurable disorders that lead to large muscle wasting. They result in constant deterioration of activities of daily living and in particular of ambulation. Some common types include Duchenne muscular dystrophy, Charcot-Marie-Tooth disease, polymyositis and amyotrophic lateral sclerosis. While these diseases individually have a low rate of occurrence and are mostly unknown to most people, collectively they affect a significant part of the population. About 1 person in 2000 suffer from neuromuscular diseases, which means an approximate total of 370â000 people over the European continent. Recent technology breakthroughs have made possible the realization of advanced powered orthotics, which are commonly called exoskeletons. The most advanced devices have successfully been able to support patients in walking despite a debilitating condition such as complete spinal cord injury. Such technology could be ideal for people with mid-stage neuromuscular diseases as it provides more mobility and independence. This work investigates the definitions and requirements that would need to be fulfilled for any proposed orthotic device to assist people living with neuromuscular diseases. To define the needs of patients with neuromuscular disease, a large literature review is conducted on gait compensation patterns. The research also includes the data collection of experimental gait measurements from fourteen people with heterogeneous neuromuscular diseases. Conclusions show that orthotics for people with neuromuscular diseases require tunable assistance at each joint and a collaborative control strategy in order to let the user control motion. Eventually, most people may not be able to use crutches. A full lower limb exoskeleton, AUTONOMYO, is designed, realized and evaluated. A particular attention is put on the optimization of the actuator and transmission units. In order to reduce the effects of inertia and weight of those units, a design is explored with actuation remotely located from the joints. The transmission is realized by custom cable wire and pulley systems, combined with standard planetary gears. The dynamics of different coupling between the hip and the knee flexion/extension joints are explored, and their benefits and tradeoffs analyzed. A novel control strategy based on a finite-state active impedance model is designed and implemented on the AUTONOMYO device. The controller consists of three states of different active impedances mimicking a visco-elastic behavior. The switching condition between states is uniquely based on the hip flexion velocity to detect the user intent. The performance of the strategy regarding the detection of intention and the modulation of the assistance is evaluated on a test bench and in real conditions with healthy pilots and with a person with limb girdle muscular dystrophy. The preliminary results are promising since all pilots (including the one with muscular dystrophy) are able to initiate and terminate assisted walking on demand. They are all able both to walk with a good stride rate and to reach moderate velocities. Healthy pilots are able to ambulate alone with the exoskeleton, while the pilot with muscular dystrophy requires human assistance for the management of balance.

EPFL2019

Control Strategies for Lower-limb Exoskeletons: from Full Mobilization to Assistance of Balance

Romain Pierre François Baud

Bipedal locomotion is a remarkable feature of humans. This skill is necessary for the activities of daily living. Unfortunately, many people only partially benefit from it or miss it entirely because of a disability. This may result in a slower gait, less endurance before pain or exhaustion, inability to climb stairs, or even the permanent use of a wheelchair. This may make reaching remote places difficult, prevents from practicing some sportive activities, and limit the chances of social interaction. Robotic exoskeletons have been introduced recently to assist the gait. The control of such devices should be addressed with care, because of the interaction with the human user, which makes part of the system unpredictable or at least difficult to model. This PhD thesis report explores the broad range of existing control methods that are currently disseminated in the literature. All these references have been sorted with a novel classification that categorizes the subparts of an algorithm, instead of considering the entire one. This rational overview contribute to understanding what was already tried, and what is missing to the state of the art. Then, the developed modular control platformis described. This platform allowed sharing electronicmodules and software between all the devices and provided a consistent and efficient development experience. It could handle all eight exoskeletons of the laboratory, even though their hardware was never the same. Fully embedded and with a convenient development interface, it allowed testing efficiently in the field. The case of the fullmobilization for paraplegic users was tackled with the exoskeleton TWIICE, intended for personal use. A controller based on operating modes was implemented and allowed its user to walk again and overcome many types of obstacles of daily living, autonomously. This controller made TWIICE the current best performer for the "Powered Exoskeletons Race" category of the CYBATHLON competition, able to overcome all the six obstacles. A variant, WIITE, enabled another paraplegic user to practice ski touring in snowy mountains. This showed a use-case with a similar handicap, but a totally different need. TWIICE is sagitally constrained, is actuated at the hip and knee joints only and has a locked ankle, to be lightweight and cost-effective. Crutches are then required to maintain the user’s balance, which prevents using the arms for interaction with the surrounding environment. A controller performing dynamic balance with such hardware would be too complicated and probably not robust enough. A suggested acceptable trade-off was to let the user use freely his arms for interactions only while standing still and use normally the crutches while walking. The controller was biologically inspired, from healthy participants trying to keep standing dynamically in a passive constraining exoskeleton, called INSPIIRE. Dynamic standing balance control was successfully assessed with a complete paraplegic user wearing TWIICE. Finally, partial assistance techniques have been investigated. First, in running using SPRIINT, a unilateral hip orthosis to assist a transfemoral amputeed user. Second, the endurance augmentation in walking was also studied with HiBSO, a bilateral hip exoskeleton. A novel assistance controller was developed, able to immediately assist, from the beginning of the first step.

EPFL2020