Wilmington robotic exoskeleton: a novel device to maintain arm improvement in muscular disease.

BACKGROUND: Upper-extremity movement is limited in individuals with muscular weakness. This paper describes a novel, articulated upper-extremity orthosis, the Wilmington Robotic Exoskeleton (WREX), which helps people overcome this movement deficit. METHODS: This prospective, case-controlled study involved an ambulatory patient with arthrogryposis multiplex congenita and 2 nonambulatory patients with spinal muscular atrophy type II. The WREX uses elastic bands to negate the effects of gravity; it allows a person with neuromuscular weakness to move their arm in 3 dimensions. The WREX can be fixed on a brace for ambulatory patients and on the wheelchair for nonambulatory patients. Assessment was performed through motion analysis (with and without the WREX), clinical examination, and qualitative questionnaire. RESULTS: Motion analysis showed a marked improvement in upper-extremity function with the WREX. The questionnaire illustrated enhanced functionality with the WREX including self-feeding, fine motor control, and use of a television remote control. Enhanced functionality resulted in improved quality of life by increasing participation in school, raising self-esteem, and increasing social interaction. Two unexpected outcomes were increased security with trunk inclination and amelioration of the effects of contractures. CONCLUSIONS: The WREX provided an increase in functionality and improved the quality of life of the patients. The device has become an integral part of the lives of the 3 patients. LEVEL OF EVIDENCE: Level III in Therapeutic Studies-Investigating the Results of Treatment.

Design and testing of a functional arm orthosis in patients with neuromuscular diseases.

The objective of this study was to determine the utility of a passive gravity-balanced arm orthosis, the Wilmington robotic exoskeleton (WREX), for patients with neuromuscular diseases. The WREX, a four-degrees-of-freedom functional orthosis, is energized by rubber bands to eliminate gravity and is attached to the wheelchair. The development and clinical testing of WREX is described in this report. Seventeen patients (14 boys and 3 girls) with muscular disabilities participated in the study. Ages ranged from 4 to 20 years. Criteria for inclusion included a weakened arm, use of a wheelchair, the ability to grasp and release objects, and the ability to provide feedback on device use. Testing consisted of administering the Jebsen test of hand function without WREX and then testing again after approximately two weeks of wearing the WREX orthosis. The timed results of each task within the test then were compared. Specific tasks related to vertical movement required less time to perform with the WREX. A large number of subjects were able to perform the Jebsen tasks with the WREX, where they were unable to perform the task without the WREX. Patients can benefit from WREX because it increases their performance in daily living activities and makes many tasks possible. The range-of-motion in the patients' arms increased considerably, while the time required to complete some of the Jebsen test tasks decreased. Most patients were very receptive to WREX, although a few were ambivalent.

Electronic monitoring of orthopedic brace compliance.

PURPOSE: Brace compliance measurement in adolescent idiopathic scoliosis (AIS) has been the subject of a few recent studies. Various sensors have been developed to measure compliance. We have developed a temperature-based data logger-the Cricket-specifically for scoliosis braces, with associated custom software, that is embedded directly in the brace. The purpose of this study was to analyze patterns of brace wear and patient compliance among children with AIS using the Cricket. METHODS: Fifty-five AIS patients prescribed various brace-time regimens were monitored using the Cricket. All subjects were treated with the Wilmington brace. The compliance rate for each group was determined. RESULTS: Overall compliance among subjects was 69.9 ± 31.5 %. Only 14.5 % met or exceeded prescribed brace time. This is consistent with previous compliance monitoring results. CONCLUSION: The results of this study objectively show the difference between prescribed and actual brace wear time and reaffirm the Cricket sensor as an accurate and comfortable brace-monitoring device.

Quantifying anti-gravity torques for the design of a powered exoskeleton.

Designing an upper extremity exoskeleton for people with arm weakness requires knowledge of the joint torques due to gravity and joint stiffness, as well as, active residual force capabilities of users. The objective of this research paper is to describe the characteristics of the upper limb of children with upper limb impairment. This paper describes the experimental measurements of the torque on the upper limb due to gravity and joint stiffness of three groups of subjects: able-bodied adults, able-bodied children, and children with neuromuscular disabilities. The experiment involves moving the arm to various positions in the sagittal plane and measuring the resultant force at the forearm. This force is then converted to torques at the elbow and shoulder. These data are compared to a two-link lumped mass model based on anthropomorphic data. Results show that the torques based on anthropometry deviate from experimentally measured torques as the arm goes through the range. Subjects with disabilities also maximally pushed and pulled against the force sensor to measure maximum strength as a function of arm orientation. For all subjects, the maximum voluntary applied torque at the shoulder and elbow in the sagittal plane was found to be lower than gravity torques throughout the disabled subjects' range of motion. This experiment informs designers of upper limb orthoses on the contribution of passive human joint torques due to gravity and joint stiffness and the strength capability of targeted users.

Series elastic actuator control of a powered exoskeleton.

A motorized upper extremity orthosis based on the passive WREX system is being developed. The orthosis is a 4 dof arm controlled by user residual force inputs. The arm is intended for people with neuromuscular weakness due to muscular dystrophy or spinal muscular atrophy. Previous work determined that actuation in parallel with gravity balancing springs required less torque than actuation in series. Compliance is achieved by using a series elastic actuator (SEA) by placing torsional springs between the motors and the WREX. A torque control was implemented on the SEA at the joint level. The response of the control law was characterized without disturbances. The SEAs were then attached to the orthosis to test the response with disturbances, and the control provided accurate joint torques.

Quantifying anti-gravity torques in the design of a powered exoskeleton.

Designing an upper extremity exoskeleton for people with arm weakness requires knowledge of the passive and active residual force capabilities of users. This paper experimentally measures the passive gravitational torques of 3 groups of subjects: able-bodied adults, able bodied children, and children with neurological disabilities. The experiment involves moving the arm to various positions in the sagittal plane and measuring the gravitational force at the wrist. This force is then converted to static gravitational torques at the elbow and shoulder. Data are compared between look-up table data based on anthropometry and empirical data. Results show that the look-up torques deviate from experimentally measured torques as the arm reaches up and down. This experiment informs designers of Upper Limb orthoses on the contribution of passive human joint torques.

Electronic monitoring of scoliosis brace wear compliance.

PURPOSE: Accurate evaluation of patient compliance with scoliosis brace usage has been a challenge for physicians treating patients with adolescent idiopathic scoliosis. This inability to accurately measure compliance has resulted in difficulty in determining brace treatment efficacy. This prospective study was performed to demonstrate the efficacy of using a new electronic brace compliance monitor, the Cricket. METHODS: The Cricket is a small encased circuit that can be attached to the brace and, by means of a temperature sensor, can record brace wear times. This study included ten subjects with adolescent idiopathic scoliosis who were prescribed the Wilmington scoliosis brace (thoraco-lumbo-sacral orthosis) into which the Cricket sensor was incorporated. Subjects kept a diary of brace wear times. RESULTS: Comparisons of data for the Cricket, subject diaries, and prescribed brace wear were evaluated. The mean error between the diary times and Cricket recording was 2%. Patient compliance was 78%. CONCLUSIONS: The Cricket is a reliable, accurate, and sensitive device to determine patient compliance with scoliosis brace usage.

Passive exoskeletons for assisting limb movement.

This article presents the state of the art in passive devices for enhancing limb movement in people with neuromuscular disabilities. Both upper- and lower-limb projects and devices are described. Special emphasis is placed on a passive functional upper-limb orthosis called the Wilmington Robotic Exoskeleton (WREX). The development and testing of the WREX with children with limited arm strength are described. The exoskeleton has two links and 4 degrees of freedom. It uses linear elastic elements that balance the effects of gravity in three dimensions. The experiences of five children with arthrogryposis who used the WREX are described.