An Adjustable Armrest Designed to Bear Weight Through the Hand
ABSTRACT
A fully adjustable armrest has been designed for adults with hemiplegia which will allow weight bearing through the palm of the hand. The intended goals of this armrest are to improve functional return, reduce glenohumeral subluxation and reduce pain in the hemiplegic upper extremity. A prototype armrest has been designed. It will be used in a study with several test subjects who will use the armrest for two months.
KEYWORDS
Adjustable armrest, subluxation, hemiplegia, wheelchair positioning
BACKGROUND
The overall goal of this study is to design and pilot a palm weight bearing armrest, that places the extremity in a position that has potential to increase motor recovery, decrease or prevent glenohumeral subluxation, and reduce overall upper extremity pain. To our knowledge there are no commercially available armrests that accomplish these goals. Currently, these goals are only accomplished by physical rehabilitative interventions such as passive range of motion and electrical stimulation.
Existing wheelchair upper extremity supports such as laptrays and armrests cause the elbow to act as the weight bearing surface. Based on clinical evidence, these devices tend to immobilize the forearm and elbow, and torque the shoulder as the body moves on it. The palm weight bearing armrest allows freedom of motion at the elbow which should protect the shoulder from torque as the body moves.
The configuration of the armrest is easily adjustable by a trained caregiver as the patient's hemiplegic upper extremity changes over time. It is well padded so the arm and hand position are comfortable to maintain for prolonged periods of time. This positioning device should require minimal education to the patient and caregivers.
STATEMENT OF PROBLEM
The goal of this project was to design and build an adjustable weight bearing armrest, that places the extremity in a position that has potential to increase motor recovery, decrease or prevent glenohumeral subluxation, and reduce overall upper extremity pain
DESIGN
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The general position of the upper extremity is as follows: the humerus is in neutral rotation and slight flexion and abduction, the elbow is in 20 to 30 degrees of flexion, the forearm is pronated, and the wrist and fingers are placed into a tolerable amount of extension which is adjustable on the armrest. The padding on the armrest begins distal to the elbow, so that the elbow can move into increased ranges of flexion as the body moves.
The forearm is supported on an ABS platform with a lateral edge. This is padded with one inch thick Sunmate foam. (See Figure 1.) A separate hand support is attached to the forearm support using a locking hinge (Adaptive Engineering Labs Biangular Bracket, Part # 80442). This hinge allows the angle of wrist extension to be adjusted. A curved palmer support is attached to the hand piece to keep the hand in a natural position. This armrest is attached to 7/8" diameter stainless steel tubing with a commercially available clamp.
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The armrest is mounted on the wheelchair using standard two-point armrest receptacles. The angle of the armrest is infinitely adjustable through a series of three telescoping tubes. The telescoping segments are composed of ¾" OD Delrin rod inside 7/8" OD, ¾" ID stainless steel tubing. The front and back posts are height adjustable, using shaft collars to lock their position. These are held in place using quick release pins. The cross piece on which the armrest is mounted must be able to telescope because its length changes as the angle of the armrest platform changes.
No strapping will be used to keep the arm in place on the armrest, to reduce the likelihood of putting stress on the shoulder joint when the patient moves his or her arm. The outside edge keeps the arm from falling off laterally. (See Figure 2.) Weight bearing on the hand should keep the arm in position during movement of the body.
EVALUATION/DISCUSSION
The prototype adjustable weight bearing armrest has been built and is ready for testing. Ten hemiplegic inpatients at the Rehabilitation Institute of Chicago (RIC) will be selected to trial the armrest. Upper extremity function, subluxation, and pain will be assessed prior to using the armrest. After being fit with the armrest, the force created through the upper extremity and muscle contraction of the hemiplegic shoulder girdle and upper extremity will be assessed. The patients will use the armrest during the inpatient stay, and continue to use the arm tray after discharge for six months. Measurements will be taken at discharge, and every two months after discharge. A phone call will be made monthly to follow the status of the subjects.
Kathryn E. Waldera, MS, ATP
Rehabilitation Institute of Chicago
Rehab Engineering Department
345 E. Superior St. Room 1561
Chicago , IL 60611
(312) 238-6409
