Prosthetics for Children
Background
The CDC estimates that there are 1,500 babies born with upper limb reductions and 750 born with lower limb reductions per year. This is also known as congenital amputation or a kid born without a limb. This puts a lot of strain on the child as they grow older, but it also causes problems for the family as a whole. As I researched the different prosthetics that are used by children, I came to the consensus that these limbs are usually very expensive and the child grows out of it in a short period of time. Instead of the families spending thousands of dollars on a prosthetic limb for a 3-6 year old, they could have a cheaper option. I would like to create a prosthetic arm that allows for the family to buy less expensive prosthetics that their kid can use while he/she is still growing up. This is a much more practical option for families trying to save money because a child in the early stages of life does not use his limbs like adults do. It is important for kids to have a prosthetic because it allows for them to do everyday functions and feel normal. Some prosthetics can go upwards of $40,000 and most insurance companies don’t want to pay for them because the arm will probably be replaced every six to ten months because the child will grow.
The method that has been used the most in recent years is the use of 3D printing each segment of the arm and assembling them after. This is a very cost effective way because you are able make the arm out of material that is cheaper that the material used for higher end prosthetics. Another reason that 3D printing is smart is because you are making each part so if a joint breaks you can easily replace it instead of having to get the whole arm repaired or replaced. The arm is also able to be customized if the kid wants a certain color or pattern. During my research of this arm, I found out that the arm is triggered by a muscle pulse. For example, if you pulse your muscle the arm will close and a second pulse will open it back up. The design is very simple and is very easy to use, but I see a potential problem. Since the arm requires a pulse of muscle what if there is no muscle that is able to activate it. Another problem I see with the use of muscle activation is that if, for example, you are doing some sort of action like lifting a bucket and you pulse your muscle to grab the bucket, but what will happen when you start to lift the bucket you will need to use that muscle to help lift it. Will the hand open back up or will it be able to hold on to the bucket?
Design and functionality
As I start to come up with my design I want to keep my main principles in mind, I want to make an inexpensive, lightweight prosthetic for children. The first part to this design is the overall design and function of the arm. First, the functionality of the prosthetic. For my arm to be easy to use I want to make it as simple as possible. Throughout my brainstorming's sessions I was able to narrow it down to either using the pulse method or creating an arm that uses no technology. I decided to use the arm that uses know technology because I would be able to create this prosthetic with my own creativity. I also think that it would be a more cost effective option for families because you do not have to add in the cost of the technology into the selling price. By not using technology, the user (a child) will be able to still complete their daily tasks and it will be simpler for the child to use. Children use their arms in much simpler ways than adults do, that is why adults prosthetics are much more expensive. The pieces to the arm would be 3D printed allowing for the parts to be made faster and allows for a lightweight prosthetic for the user. There are many different types of plastic and other materials used for 3D printing objects, but the material I chose was PLA plastic. PLA plastic is very durable and strong. Although the filament is very thin, you can adjust the infill to strengthen the object. The infill is a crisscross pattern that is made inside the object to strengthen it, the bigger the infill the more the inside of the part is filled up with material.. To make my product very durable, but lightweight, I thought that it would be best to have the infill at 70-100%. This allows for each piece to be strong yet partially hollow on the inside. To maximize the durability of the prosthetic I would make the joints 100% filled to make them last longer. By using the PLA plastic the child is able to customize their prosthetic however they choose. This allows for the child to feel good when wearing it instead of thinking they are an outsider. Lastly, the PLA plastic is around $10 per pound which could allow you to make all the parts with spare pieces for around $20-25 (not including the cost it would take to print).
The prosthetic arm is going to be working without technology which some may think that this method would be impractical for a prosthetic, but you need to consider the fact that this is going to be used by young kids. It is not necessary for a kid to use a very expensive mechanical arm that they are going to grow out of. My prosthetic is designed to be easily replaceable so the parents do not spend tens of thousands of dollars on a prosthetic for their 5 year old. The arm will be able to do simple motions like help you pick up and hold an object or even help the kid throw a ball. Besides the arm going over the arm there will also be a strap that will help the arm from moving or falling. The strap will go over the shoulder on the side the prosthetic is and a connecting strap will go across the top of the chest and around the back for added support. Before you put the arm on there is a simple soft sleeve that goes under the prosthetic first, as you see in most cases with prosthetic legs. This sleeve helps with comfort and sweat control. Now the part that is going to take the most of the time printing is the upper/forearm segment of the prosthetic. The length and weight of the cast is going to vary for each child, but the design will stay the same. The hardest part about this design was finding a way for the arm to fit any kid and the solution I came up with was a way for the upper arm (above the elbow) to adjust so the cast could last longer. There would be two pieces that would bend around the arm of the child and you could tighten or loosen it as much as you like. The lower arm would be a cylinder that would be at around 90% infill. This arm would connect to the hand where some of the smaller pieces are. The palm would be 90-100% infill to make it as strong as possible while the finger pieces would be around 70-80%. The palm will connect the the fingers through a joint piece. The joint and the arm will be met at a hole in the palm where a rod will be placed through all the joints. This will allow for the joints to move freely making it easier to handle. Since the hole is in the front part of the palm this will allow for the fingers to only move 180 degrees. Each finger will have two corresponding finger parts that are connected to joints so the fingers can easily move. The joins will be connected the same way the joints were connected to the palm. The hand can be fit to the size of the kid and you can add a grip to the palm or fingers to make holding on to something a lot easier.
The last part to the design process is looking at how the arm is going to be used. As I stated earlier the arm is going to be used by kids who do not use their arms like an adult would. They are limited in the activities they have to do making my prosthetic perfect for them to use. The arm/elbow will have very limited movement because it will allow for the prosthetic to be stable at all times. On the other hand the fingers will have almost 180 degree motion allowing for the child to grab objects or help hold an object. The hardest part for me to decide what to do was to come up with a way for the fingers to move. Since I did not want to use technology in my design I thought the best way was to allow for the kids to move the fingers themselves. Although it is not the most practical way for the fingers to move, it allows for the kid to move the fingers into position. This decision was made because it would cost less to have the child move the fingers than have an expensive piece of technology move it.
Overall I was very pleased with the design I was able to create because I was able create a design form my own creativity. This design shows my higher level thinking because I was able to solve a problem that is currently in the world, the lack of a inexpensive prosthetic arm for children. I was able create a design based on the lacking aspects of some of the other prosthetics I had researched previously. I believe that this prosthetic can help make a difference in the world because I have create a very creative way to help children all across the world.