Hang 10: a prosthetic adaptation for shoulder disarticulation

Developers: Lucas Hoffmann, Juan Velasquez

Supervising Professor:  Kevin Caves



Each year, approximately 185,000 Americans undergo amputation of a limb [1]. Our client is part of that group of people as she has had a complete amputation of her right arm. As a result of the surgery, her right side is approximately 1 inch shorter than her left and contains bony protrusions which are sensitive to touch. Further, when she wears unmodified clothing, it slides off her right side. We created a device that provides our client with a cushioning support that protects her sensitive boney protrusions and at the same time keeps her clothes from sliding off her shoulder, leveling out the differences in length and giving her a more natural look.


Our client, Sarah, has had a complete amputation of her right arm. The procedure, which is known as Shoulder Disarticulation, removed all aspects of the arm and parts of the shoulder joint, leaving Sarah with only her clavicle and scapula on the right side of her body (Figure 1) [2]. When it comes to an above-elbow amputations, the preservation of length is an important goal because it will improve the contour of the shoulder and when too much must be removed it impairs the patient’s ability to properly fit clothing [3]. As a result of the surgery, Sarah’s right shoulder is approximately 1” shorter than her left. Due to this difference in length, when she wears unmodified clothing, it tends to slide off on her right side. Further, because of the surgery, there is a bony protrusion directly under the collar bone on her right side. This area is extremely sensitive and is a concern for Sarah, as contact with the area causes her pain.

Sarah has previously utilized prosthetics underneath her clothing but the artificial appearance of these did not appeal to her and she would prefer something more natural and comfortable. Sarah is not alone in her decision to abandon a prosthetic attachment. Around 20% of people that have used a prosthesis have abandoned it, citing comfort and cost as the primary factors [4]. Moreover, a different study shows that even if the wearer does not totally abandon the prosthetic, 55.3% of users cannot wear the device for more than 8 hours, again citing comfort as the primary concern [5].

Sarah is independent in all her activities. She lives alone and is active, spending a lot of her time in public and outside of the house. Therefore, there is a need for a device that Sarah can use daily and in public that not only keeps her clothing in place but also provides a cushioning support for her bony protrusion. Currently, there is nothing on the market that address this need, specifically. As a temporary solution, Sarah has tried to incorporate shoulder pads under her clothing. However, these were not comfortable to her, and in most cases, found they were too bulky. This was a good starting point for us and we have leveraged the geometry of a women’s shoulder pad as the inspiration for our design

Project Goals

The goal of this project is to develop a system that our client can use independently which prevents her clothing from slipping off her shoulder as well as provides protection over her sensitive, bony areas. The system will be usable by the client without any help from other people. The system will also able to be worn under clothing and will not require the client’s clothing to be altered in any way. It needs to be comfortable enough to wear all day, every day. In addition, the aspects that get dirty need to be removable and washable. While one iteration of the system is being cleaned, there must be a second that allows for continued use. Lastly, the anatomical differences of her shoulders need to be balanced, allowing a natural and even look when Sarah wears clothing.

Design and Development

Our design has three main components: the metal wire frame which maintains the shape of the shoulder pad, the memory foam pads that acts as a cushioning device, and the amputee sock that acts as the cover for the entire device (Figure 3). It is positioned on the right-side clavicle, under the bra strap. As outlined in the project goals, the device is discreet enough for Sarah to wear under her normal clothing and evens the size difference in length between her left and the right shoulder. The memory foam pad can’t be washed, so the device allows for the memory foam pad to be removed. Both the outer layer and the wire frame can be hand-washed together. The device is thin enough for Sarah to slip the device under her bra strap and thus not have to worry about it falling off her shoulder

Metal Wire Frame

The wire frame is made up of steel wires that are placed inside fabric that has stitched channels that allow for wires to run through the fabric and give the fabric a sturdy shape (Figure 4). The frame is 7 inches wide and 4 inches long.  The wires are malleable enough for the device to be shaped to our client’s anatomy while at the same time being sturdy enough to maintain that shape. A corrosion experiment was conducted, and it was determined that no additional treatment of the wire, other than the manufactured coating, was necessary. The ends of the channels are reinforced with additional fabric so that the wires will not poke out over time.

Memory Foam Pad

The memory foam was acquired by purchasing a neck pillow since the ends of the pillow had the desire shaped that we were looking for. The memory foam was cut using a hot wire cutter. The front padding insert is ¼ inch thick and the back-padding insert is ½” thick. The front pad needs to provide cushioning while maintaining discretion and the back pad needs to make up for the anatomical differences.  As can be seen from Figure 5, the memory foam pads were as long as the metal wire frame, 4 inches, but are only 3 inches wide. This allowed for a gap where the device sits on the clavicle, reducing bulkiness.

Outer Layer

The outer layer of the device material is from the CoolBlue prosthetic sock (Figure 6). The material is very soft, making the device very comfortable to wear for an extended period of time. The amputee sock material can be easily handwashed and dried so Sarah doesn’t have to worry about any problems related to the cleanliness or the smell of the device since the device is easy to maintain. The material has a high friction coefficient, thus the outer layer of the device as well as the device shape will make it that Sarah never has the fear of having her clothes constantly slip off her shoulder.


The first design spec that was evaluated was to see if the device would prevent clothes from the clients shoulder. We verified this by placing materials of known weight on the device and see if the material stays on the device or slides off the device. The prevention of sliding was then validated by having our client wear 5 different shirts and then see if there is any sort of sliding of her shirts. The client also has to be able to put the device on and remove the device without the help of others. To validate this we had several people put the device on and off and made sure that they didn’t have any difficulties with this task. To verify this we had our client put the device on and off and made sure that she could do it without us being in the room while she put it on. The device itself will get dirty and accumulate odor with wear so the device must be easily cleaned. To validate this we hand-washed the device three times and made sure that the device didn’t lose its form. To verify this we had our client wear the device for a day and then hand-wash it and see if there were any left over odors after she washed the device. The device also has to act as a cushioning device for the client’s sensitive boney area. To verify this we decided to hit the device with a 0.45 lbs.-f force while being worn by one of us and see if any deformation occurred or if we felt any impact of the force. This was then validated by us creating a Likert scale of cushioning for our device and then had our client fill it out and rate the device at least a 4 out of 5 in the Likert scale. The device also has to be light enough and comfortable enough for the client to wear for an extended period of time. To verify that our device was light enough we weighted the device and made sure that it weighed less than one pound. To verify the comfortability of the device we created our own scale and rated the device on a Likert scale. To validate both how the comfortable and how light enough the device was, we created a Likert scales for our client and had her at least rate the device a 5/5 on both scales.  Finally, the number one most important aspect of the device is that it must be discreet. The validate how discreet the device is we created a Likert scale and had ourselves rate the device at least a 4/5 on that scale. To verify this we had our client fill out and rate our device on that Likert scale and see if she rated it at least a 4/5 on that scale.

Discussion and Conclusions

The components of our system came together to produce a functioning device that fully complies with all design constraints and criteria. Each part of our device is specifically fabricated to provide the most comfortable experience for our client and at the same time be discreet. This design provides our client with a prosthetic shoulder that both acts as a cushioning device for her sensitive boney areas and an extended part of her shoulder so that it matches the length of her left shoulder and is able to provide enough support to prevent clothes from slipping off her shoulder. The final price of the device came to approximately $290, which is the price for the production of two of the devices that will allow her to use the device at all times while the other device is being cleaned. The design is also custom made, thus nothing like the device can be found on the market.


[1] People With Amputation Speak Out With the Amputee Coalition of America (ACA).

[2] “Shoulder Disarticulation and Forequarter Amputation: Surgical Principles”, Digital Resource Foundation for Orthotics and Prosthetics Community  http://www.oandplibrary.org/alp/chap10-01.asp

[3] Ovadia, Steven A., and Morad Askari. “Upper Extremity Amputations and Prosthetics.” Current Neurology and Neuroscience Reports. U.S. National Library of Medicine, Feb. 2015. Web. 15 Sept. 2018.


[4]  “A Survey on Activities of Daily Living and Occupations of Upper Extremity Amputees” NCBI, 2011, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3309384/

[5] “Amputee Patient and Comfort Compliance”, The Amputee Coalition, 2011, https://www.amputee-coalition.org/wp-content/uploads/2015/06/lsp_opedge-survey-article_120115-113042.pdf


We would like to acknowledge a number of people for their help in completing this project: National Science Foundation grant # CBET 3310005, Kevin Caves, Urvi Telang, Erin West, and the entire BME 460L Fall 2018 class.

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