Mechanical Design and Feasibility of a Finger Exoskeleton to Support Finger Extension of Severely Affected Stroke Patients

Abstract

In this paper we presented the mechanical design and evaluation of a low-profile and lightweight exoskeleton that supports the finger extension of stroke patients during daily activities without applying axial forces to the finger. The exoskeleton consists of a flexible structure that is secured to the index finger of the user while the thumb is fixed in an opposed position. Pulling on a cable will extend the flexed index finger joint such that objects can be grasped. The device can achieve a grasp size of at least 7 cm. Technical tests confirmed that the exoskeleton was able to counteract the passive flexion moments corresponding to the index finger of a severely affected stroke patient (with an MCP joint stiffness of k = 0.63Nm/rad), requiring a maximum cable activation force of 58.8N. A feasibility study with stroke patients (n=4) revealed that the body-powered operation of the exoskeleton with the contralateral hand caused a mean increase of 46 • in the range of motion of the index finger MCP joint. The patients (n=2) who performed the Box & Block Test were able to grasp and transfer maximally 6 blocks in 60 sec. with exoskeleton, compared to 0 blocks without exoskeleton. Our results showed that the developed exoskeleton has the potential to partially restore hand function of stroke patients with impaired finger extension capabilities. An actuation strategy that does not involve the contralateral hand should be implemented during further development to make the exoskeleton suitable for bimanual daily activities.

Design, modeling and analysis of a novel index finger exoskeleton for stroke rehabilitation

“…Using Bowden-cable-based series elastic actuation, Priyanshu et al offer a unique index finger exoskeleton that enables bidirectional torque control of the device with great backdrivability and low reflected inertia [9]. Many other studies have described various hand exoskeleton structures for rehabilitation [10,11]. However, many of them have a disadvantage, the design of the exoskeleton model is fixed, can not well meet all patients, and patients need to customize the model.…”

Bionic Design of a Novel Portable Hand-Elbow Coordinate Exoskeleton for Activities of Daily Living

“…After a stroke, patients with stiff finger joints initiate their hand movements from a bent position. Achieving sufficient hand opening is crucial for performing activities of daily living (ADL) [20]. When designing the exoskeleton joint range, we primarily consider the following three aspects: (1).…”

“…Therefore, to accommodate a wide range of objects for gripping, the device should be capable of achieving at least a 5-cm grip size, and preferably a 7-cm grip size. To achieve an opening greater than 5 cm with the average finger size, a bending angle of approximately 10 • (MCP joint) and 20 • (PIP joint) in the index finger is necessary [20]. (2).…”