The case in study is of an individual with arthrogryposis multiplex congenita (AMC) who cannot bend his elbows or feed himself efficiently due to elbow contractures. An automatic fork was designed to assist the subject in self feeding. With the push of a button, the fork with the food on it will move toward his mouth for ingestion. The study is intended to increase his independence and self esteem while investigating the possibility of applying the technology to other AMC patients.
Assistive eating utensil; assistive fork; arthrogryposis multiplex congenita
Arthrogryposis multiplex congenita (AMC) is a disease characterized by multiple permanent joint contractures (1), and involves limited or fixed mobility of multiple joints. In Greek, its name means “many crooked joints at birth” although it initiates early on during fetal development if the fetus does not move around enough due to neurological, muscular, connective tissue, or skeletal abnormalities or intrauterine crowding (2,3). AMC occurs in about one out of every three thousand births (4). Individuals with AMC have trouble performing routine tasks such as walking and eating. In particular, because of fused elbow joints, our subject cannot eat in an ordinary fashion. When attempting to eat with a fork, he successfully pokes the food with the prongs and rotates the fork towards his face, but upon lifting his arm upward using his shoulder joints, his arm extends linearly away from his mouth and he cannot close the resulting gap of several inches between the food and his mouth. As a result he either needs to be fed, or feeds himself in a very inconvenient manner.
This study is intended to fulfill several needs of our subject, a child with AMC. Namely, he deserves self esteem, which can be achieved in one way by his having similar capabilities to his peers during meal time. To that end, we are designing an eating utensil that our subject will be able to use independently. The utensil will be able to move the food to his mouth through his decreased range of motion by lengthening itself with minimal effort on the user’s end. Currently, there are several eating utensils designed to assist people with varying disabilities. Weighted utensils are available on the market for patients with Parkinson’s disease (PD), although some studies argue that they do not alleviate hand tremors (5). Doctor’s also advise PD patients to use a rocker knife and “spork” when eating (6). Angled or curved utensils are also sold to help individuals with limited wrist motion. In addition, available on the market is a telescoping fork, called the “Freeloader,” that can be lengthened when pulled at. This device, along with the others however, would not meet our subject’s needs since each would still require bending of the elbows in order to reach the food to the mouth. For the more physically impaired there are motorized devices such as the Winsford Feeder ®, which costs about $3000. This is not ideal for our subject due to the high cost and the issue of portability. While there are a number of solutions on the market for some individuals, there is no current device that exists between the extremes of these passive and active technologies and is appropriate for our subject.
To gain a better understanding of the gaps left by the devices available on the market, we met with our subject to establish the parameters required in our device design. During the meeting, we had him simulate eating with the Freeloader while using play dough to mimic food. We found that when he attempted to use a table fork he was able to reach the food on the table to place it on the fork, but upon rotating his wrist towards his mouth his fingers were about 32 centimeters (cm) away, while the fork was only 22 cm long. Simply using a longer utensil would not solve the problem since that would not allow him to pick up the food from the plate easily, thereby creating a problem on the other end. It was clear from our observations that the design would require a mechanism that would elongate the fork to provide the subject ease of use on both ends, while placing the food on the fork and while bringing it to his mouth.
Another point of consideration as we were observing the subject was the time frame in which our device would fully extend. Our subject would get frustrated if his food came to his mouth in an exaggerated slow motion. On the other hand, it would not be safe for him to have a fork coming at him too quickly. We approximated that a full extension of the fork in about 3 seconds was a reasonable time to wait for his food and would be comparable to the eating kinematics of someone without AMC. More importantly, it would not pose a hazard to the user.
Additionally our observations revealed that the subject did not encounter any difficulties maneuvering in the fork when it was fully extended with the added weight of ‘food’ placed on the prongs of the fork. However, when a conservative amount of weight was placed on the opposite end of the utensil to simulate the weight of an attached motorized unit, he had trouble maneuvering the fork. Therefore the distribution of weight on the device became a major design consideration as well.
Finally, we had to keep in mind that our subject is ten years of age and as he grows, his arm will be even further away from his mouth. While currently the distance between his fingers and his mouth when his arm is fully extended is only 32 cm, the average corresponding length in an adult is about 56 cm (7). Therefore, if the device is intended for long term usage, it was imperative that the design would accommodate his growth.
Initially, before meeting with the subject, several design concepts were considered. The first design concept was a device that would be similar to a piston in a pipette. That idea was rejected since it would not provide a reliable, steady displacement during extension and retraction of the fork. Another design concept was to have a flexible rod inserted in the backend of the Freeloader fork and have a manual winding mechanism to move the telescoping apparatus in and out. Considering the lack of speed and the substantial effort that would be required in this design concept, it was determined to not be ideal as well. This led us to decide the best design concept would be to have a motor attached to the end of the utensil that would provide the necessary torque and speed to wind and unwind the flexible rod with the flip of a switch. However, as mentioned previously, upon meeting with our subject we realized that this design concept required adjustment since the subject would not be able to independently and functionally handle the utensil with the weight of an attached motor on the end.
To address the issues found throughout our meeting with our subject described above, our final design was drafted. (See Figure 3). It involves a battery powered motor that is stationary on the table. The torque is transferred through a flexible Dremel® cable that is attached to a rotating threaded rod. A hollow cylinder encircles the threaded rod. To avoid the subject from hurting himself when using the device, a blunt, Gerber® toddler fork is attached to the end of the hollow cylinder. Finally, an outer case encloses the apparatus and serves as the handle of the fork. The threaded rod is locked in place in the casing to allow only rotational movement. As the rod turns, the surrounding cylinder is forced to translate linearly, guided by wings that follow grooves within the inside of the handle. The fork is designed to stop translating when it extends to a preset maximum allowable position. Additionally, the motor is accompanied with a clutch that prevents the motor from exerting an over-torque on the cable. The device is operated with an easy-to-activate rocker switch that can be set to forward, reverse, or off. The motor unit is covered with an aesthetic foam case to preserve minimum noise and disturbance.
Finally, the fork attachment can be easily removed between meals to allow for dishwasher cleaning. If desired, the rest of the apparatus can also be disassembled for a thorough cleaning.
This design will enable our subject to feed independently while building his self esteem. On a clinical perspective, it will encourage him to use his shoulders, wrists, hands, and fingers, which will improve his manual dexterity.
The design was accomplished while keeping costs to a minimum. The total amount spent on the final model was under seventy five dollars. What the fork offers the subject is arguably worth far more. Also, the fork costs forty times less than the Winsford Feeder® and is comparably more portable.
Several enhancements can still be added to our current design. A micro switch can be added to the device to shut the motor down as the translating cylinder approaches the maximum position. This will eliminate any noise that the clutch would otherwise generate as it engages. Finally, a more ergonomic grip can be achieved if the handle were made of rubber and have grooves for the placement of fingers.
(1) Merck Manuals Online Medical Library. Arthrogyposis Mulitplex Congenita. 2009-2010.
Retrieved April 21, 2010. http://www.merck.com/mmpe/sec19/ch288/ch288b.html
(2) MedicineNet.com. Definition of AMC (Arthrogyposis Mulitplex Congenita ). 2010. Retrieved
April 21, 2010. http://www.medterms.com/script/main/art.asp?articlekey=7533
(3) Healthline. Distal Arthrogryposis Syndrome. Retrieved April 21, 2010.
(4) Orthoseek. Arthrogryposis. 2010. Retrieved April 21, 2010.
(5) Clin Rehabil. 2002 Aug;16(5):481-92. A randomized controlled trial of the effects of weights on amplitude and frequency of postural hand tremor in people with Parkinson’s disease.Meshack RP, Norman KE. School of Rehabilitation Therapy, Queen’s University, Kingston, Ontario, Canada.
(6) WebMD. Parkinson’s Disease: Planning Daily Activities. 2005-2010. Retrieved April 21, 2010. http://www.webmd.com/parkinsons-disease/guide/parkinsons-daily-activities?page=2q1
This project was made possible with the support of grant number H133E050011 by the NIDRR. We also would like to thank Dr. Richard Foulds, PhD and Megan Damcott, MS, for advising our team and Children’s Specialized Hospital for their aid in providing us a customer for feedback. Finally, we appreciate John Hoinowski and Ghaith Androwis for their assistance in the lab.
Author Contact Information:
Benjamin Lieberman, 239 Zachary Ct., Lakewood, NJ 08701, 347-236-1499