An adaptable human-like gait pattern generator derived from a lower limb exoskeleton

Walking rehabilitation processes include many repetitions of the same physical movements in order to replicate, as close as possible, the normal gait trajectories, and kinematics of all leg joints. In these conventional therapies, the therapist's ability to discover patient's limitations-and gradually reduce them-is key to the success of the therapy. Lower-limb robotic exoskeletons have strong deficiencies in this respect as compared to an experienced therapist. Most of the currently available robotic solutions are not able to properly adapt their trajectories to the biomechanical limitations of the patient. With this in mind, much research and development is still required in order to improve artificial human-like walking patterns sufficiently for valuable clinical use. The work herein reported develops and presents a method to acquire and saliently analyze subject-specific gait data while the subject dons a passive lower-limb exoskeleton. Furthermore, the method can generate adjustable, yet subject-specific, kinematic gait trajectories useful in programming controllers for future robotic rehabilitation protocols. A human-user study with ten healthy subjects provides the experimental setup to validate the proposed method. The experimental protocol consists in capturing kinematic data while subjects walk, with the donned H2 lower-limb exoskeleton, across three experimental conditions: walking with three different pre-determined step lengths marked on a lane. The captured ankle trajectories in the sagittal plane were found by normalizing all trials of each test from one heel strike to the next heel strike independent of the specific gait features of each individual. Prior literature suggests analyzing gait in phases. A preliminary data analysis, however, suggests that there exist six key events of the gait cycle, events that can adequately characterize gait for the purposes required of robotic rehabilitation including gait analysis and reference trajectory generation. Defining the ankle as an end effector and the hip as the origin of the coordinate frame and basing the linear regression calculations only on the six key events, i.e., Heel Strike, Toe Off, Pre-Swing, Initial Swing, Mid-Swing, and Terminal Swing, it is possible to generate a new calculated ankle trajectory with an arbitrary step length. The Leave-One-Out Cross Validation algorithm was used to estimate the fitting error of the calculated trajectory vs. the characteristic captured trajectory per subject, showing a fidelity average value of 95.2, 96.1, and 97.2%, respectively, for each step-length trial including all subjects. This research presents method to capture ankle trajectories from subjects and generate human-like ankle trajectories that could be scaled and computed on-line, could be adjusted to different gait scenarios, and could be used not only to generate reference trajectories for gait controllers, but also as an accurate and salient benchmark to test the human likeness of gait trajectories employed by existing robotic exoskeletal devices.The research was partially funded by CONACyT Doctoral program, Tecnolgico de Monterrey/Robotics Lab and research chair program for distinguished professors in Biomechatronics

Tribocorrosion behavior and ions release of CoCrMo alloy coated with a TiAlVCN/CNx multilayer in simulated body fluid plus bovine serum albumin

While the CoCrMo biomaterial is currently employed in artificial joints, there are medical concerns regarding its metal ion release and material loss caused by tribocorrosion. In this work, a TiAlVCN/CNx multilayer coating has been employed to improve the tribocorrosion-resistance of the CoCrMo substrate. During the tribocorrosion test, with the sample immersed in a simulated body fluid containing bovine serum albumin, open-circuit potential measurements showed more noble potential as well as a reduction of both the friction coefficient and wear-rate during the sliding phase. Inductive coupled plasma results demonstrate that the multilayer coating effectively blocked the emigration of metallic ions.Funding Agencies|CONACYT [FOMIX Jal-2010-10-149472]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Tecnologico de Monterrey research seed fund</p

Cutaneous lupus erythematosus: First multicenter database analysis of 1002 patients from the European Society of Cutaneous Lupus Erythematosus (EUSCLE)

In this prospective, cross-sectional, multicenter study, we assessed clinical and laboratory characteristics from patients with cutaneous lupus erythematosus (CLE) using the Core Set Questionnaire of the European Society of Cutaneous Lupus Erythematosus (EUSCLE). 1002 (768 females, 234 males) patients with different subtypes of CLE, such as acute CLE (ACLE, 304 patients), subacute CLE (SCLE, 236 patients), chronic CLE (CCLE, 397 patients), and intermittent CLE (ICLE, 65 patients), from 13 European countries were collected and statistically analyzed by an SPSS database. The main outcome measures included gender, age at onset of disease, LE-specific and LE-nonspecific skin lesions, photosensitivity, laboratory features, and the criteria of the American College of Rheumatology (ACR) for the classification of systemic lupus erythematosus. The mean age at onset of disease was 43.0±15.7 years and differed significantly between the CLE subtypes. In 347 (34.6%) of the 1002 patients, two or more CLE subtypes were diagnosed during the course of the disease and 453 (45.2%) presented with LE-nonspecific manifestations. Drug-induced CLE and SjögrenD́s Syndrome had the highest prevalence in SCLE patients (13.1% and 14.0%, respectively). Photosensitivity was significantly more frequent in patients with ACLE, SCLE, and ICLE compared with those with CCLE. The detection of antinuclear antibodies such as anti-Ro/SSA and anti-La/SSB antibodies revealed further significant differences between the CLE subtypes. In summary, the EUSCLE Core Set Questionnaire and its database facilitate the analysis of clinical and laboratory features in a high number of patients with CLE and will contribute to standardized assessment and monitoring of the disease in Europe. © 2012 Elsevier B.V