Endoskeletal and Exoskeletal Prosthesis

Advantages and Disadvantages

This story examines the advantages and disadvantages of two lower extremity prostheses designs – endoskeletal and exoskeletal and their differences. When you suffer limb lose, the timing of a prosthetic device depends on the location, length and how quickly the residual limb heals. A prosthetic device can replace some functions of the missing limb.Finding the right prosthetic device and learning how to use it can be difficult. While exoskeletal prostheses are not suitable for through-knee amputation, endoskeletal prostheses are suitable for all levels of amputation.  It is often lighter and is more cosmetic in nature. It also provides enough provisions for a good dynamic alignment. I lost my leg at age 5 when I was struck by an army truck while crossing the road. According to Amputee Coalition, there is an estimated two million people in the United States living with limb loss. “Among those living with limb loss, the main causes are vascular disease (54%) – including diabetes and peripheral arterial disease – trauma (45%) and cancer (less than 2%)”. After amputation, the next step is acceptance and living with it by means of prosthetic limbs. 

The goal of this story is to identify all the properties that results in the effectiveness of using this type of prostheses and through-knee amputation will be focused on throughout. This type of amputation has been abandoned by surgeons because the healing rate is very low. To be able to use a prosthetic limb, amputees will need rehabilitation first. The next step will be to practice using a prosthetic limb with a physiotherapist and sometimes occupational therapist. When designing a prosthetic lower limb socket, an orthotic must consider certain forces that will be applied between the prosthetic and the patients stump. In J Hughes article, Biomechanics of the through-knee prosthesis, “The functional loss suffered due to the absence of the normal knee joint is considerable for the TK amputee as it is for the AK” (TK-through knee, AK-above knee). 

Endoskeletal prosthesis is a type of prosthesis where the supporting structure is internal to the normal shape of the limb and exoskeletal prosthesis are on the outside. The cost of the materials needed for an endoskeletal design is cheaper than exoskeletal design and fabrication cost is usually reduced by 50 percent. Because of the type of socket and pylon used, together they weigh about one or one and a half pounds. Endoskeletal design prostheses are preferred over exoskeletal prostheses because during the rehabilitation process, the alignment can be modified. When I had my first prosthetic leg at 10 years old, it was an exoskeletal design. I remembered it being made of plastics and laminates. It was very rigid, heavy but lasted a long time. It couldn’t be adjusted. Unlike endoskeletal designs, these are protected from harmful elements such as moisture. The time that is required for fitment of endoskeletal prosthesis is much less as compared to exoskeletal prosthesis and they can be suitable to all levels of amputation which are great advantages. However, it is heavy and can be uncomfortable to use. Processing time also is much longer. Some surgeons have advised against through-knee amputation because the healing rate is very low, and it would be harder for the patient to use a prosthetic device in the future. An amputee needs a stable platform for prosthesis, so they prefer below knee amputation.

Endoskeletal

Exoskeletal

To learn more about this, I visited Madison Public Library and came across Ron Seymour’s book, “Prosthetics and Orthotics: Lower Limb and Spinal”. He stated that “the endoskeletal design permits new sockets to be made as the volume in the residual limb decreases, without altering the entire prosthesis”. Exoskeletal designs are more computer-aided and many orthotics had always recommended endoskeletal prosthesis because they are more adaptable, and the components are more adjustable.

Next, I visited Sisson Mobility Inc. in Madison, WI and spoke to the founder and President, David Sisson. He stated that he started building prosthetic limbs when he worked at a different clinic during the time he was studying in college. He decided to open his own clinic in the year 2000. I asked him about the debate between endoskeletal and exoskeletal prosthetic designs and what his thoughts were. He stated that exoskeletal designs were mostly for recreational activities or active people because it can enable high impact activities like running. He mentioned a statement from an actual amputee:

“I've been able to do so many things since I got [my ExoSym devices] for [the first time in] ten years, and what a joy it is. But what I haven't done is even more important—I haven't fallen down, and I haven't looked at my future as one slow slide into being in a wheelchair again. And I don't hurt anymore—the relief is amazing. It's hard to believe that being pain-free is going to be my new normal." – Nancy G. from Massachusetts 

He said some people prefer the extra durability of the exoskeletal type prosthesis even though the functions are similar regardless of the external look. Most patients he has worked with prefer the endoskeletal type because it gives them that comfort knowing that the cosmetic can always be modified. At the end of the day it’s up to the patient to choose.

To conclude, despite many extraordinary advances, the functionality of prosthetic limbs still remains limited. My personal experience as an amputee led me to argue that endoskeletal prostheses are better than exoskeletal because it is cosmetically appealing and light weight. It’s also more versatile and the socket allows for easy maintenance, adjustment and replacement of feet. However, a determination of what type of prosthesis is usually made by the prescribing physician and/or prosthetist based on each patient’s functional needs. An endoskeletal prosthetic design is usually recommended for geriatric amputees (older people with amputation or someone with lower extremity amputation), because of the ease with which the adjustments can be made.

-Harriet Gomez

Images from Pinterest and google.

09/17/2018