# Low-Resource Prosthetic Devices for a Bilateral Amputee: Combining a Thermoformed Water Bottle Socket with a 3D Printed End Effector --- For more pictures from this project, [check out the gallery](https://hub.e-nable.org/u/kreeser1/gallery/custom-gallery/view?openGalleryId=89#.jpeg). --- A patient came to [Lake Victoria Disability Centre](wiki:/u/kreeser1/wiki/Lake+Victoria+Disability+Centre "Lake Victoria Disability Centre") (LVDC) accompanied by a liaison that helps to transport those in need from his village, four hours away, to LVDC for treatment. At 16, the patient came across a downed high-voltage electrical wire and was electrocuted. The trauma resulted in the loss of both of his arms above the elbow, as well as one of his legs at the knee. Now 18, he relies on his family to help him perform most tasks, and hasn’t been able to participate to his full potential in school. The P&O team and I discussed options, and I was given the final say on which approach to take. We decided that we would spend one day to make a set of functional, low-resource prosthetic devices until such time that the P&O department could fit him with a more robust, traditionally-made prosthetic. We chose to thermoform 1.5 L water bottles around plaster casts of the patient’s residual limbs, and 3D print a simple end effector to hold an utensil for eating. We determined that the residual limb on his right side was a length that would allow the use of a utensil in a fixed position, angled inward. In theory, he would be able to both scoop food onto the eating utensil and bring the utensil to his mouth without the need for a movable joint.  ###### Left: a 1.5 L plastic water bottle being held up to the patient’s residual limb. Right: A rough sketch of the proposed prosthetic device. --- ### Casting of the Residual Limbs I’ll be covering the full processes of taking casts of residual limbs [in another write up](wiki:/u/kreeser1/wiki/Creating+Soft+Sockets+and+3D+Scans+from+Plaster+Casts#null "Creating Soft Sockets and 3D Scans from Plaster Casts"). In brief, the patient removed his shirt and was draped with a plastic sheet to keep plaster off of his pants and torso. [Petroleum jelly](https://en.wikipedia.org/wiki/Petroleum_jelly) was applied lightly to both residual limbs, and each were wrapped with water-soaked [plaster](https://en.wikipedia.org/wiki/Plaster) bandages and the plaster was allowed to set. The negative casts were removed from the limb by carefully cutting down one side with a razor, perpendicular to a series of horizontal lines drawn in skin-marking pencil. The horizontal lines were for reference to ensure the seam of the cast can be closed and aligned properly later.  ###### Views of the negative plaster cast of the patient’s residual limb (left limb). Note the markings in skin-marking pencil (blue). --- Contours and measurements taken from the patient were sketched into the inside of the plaster cast with a skin-marking pencil, followed by skirting the cast with additional plaster bandage to make the rim of the opening even. Petroleum jelly was applied lightly to the inside of the negative cast, and a liquid plaster mixture was poured in. A metal bar was positioned within the cast, now serving as a mold, for ease of handling after the plaster positive cures and is removed from the mold. The plaster positive took approximately 45 minutes to fully cure, and was removed by cutting away the negative mold that surrounded it. ### Creating the Socket After post-processing the plaster positive, a 1.5 L plastic bottle was cleaned and dried. The bottom of the bottle was cut off leaving the neck and mouth of the bottle intact. Enough bottle should be left over to extend slightly beyond the skin-marking pencil line marking contour of the patient’s residual limb, which should have transferred from the negative cast to the positive cast. The bottle is slowly heated with a heat gun, making the plastic contract and conform to the contours of the plaster cast. As the plastic shrinks around the cast, it becomes thicker and sturdier. A handheld electric saw is used to cut the plastic bottle at the contour lines on the plaster cast, giving the socket its final shape.  ###### Rajab Hamis demonstrates the steps necessary to thermoform a plastic bottle around a plaster cast of a patient’s residual limb. --- The lip of the thermoformed socket is sanded down to smooth over any sharp edges or burrs left from the handheld electric saw. The socket was carefully dry-fit onto the patient’s residual limb, and we noted that we needed to remove material from the [axilla](https://en.wikipedia.org/wiki/Axilla) area which was chafing the patient when he moved his arm. The rim of the socket was then carefully lined with [PVC leather](https://en.wikipedia.org/wiki/Artificial_leather) using [contact adhesive](https://en.wikipedia.org/wiki/Adhesive#Contact) (Premia Bond) The purpose of lining the rim with PVC leather is to provide added protection against scratching the skin with the socket rim. The fit of the socket onto the residual limb was checked several more times before moving on in the fabrication process.  ###### Upper left: Sanding the rough edges of the lip of the thermoformed socket. Upper right: Checking the fit of the thermoformed socket on the patient. Lower left and lower right: Views of the thermoformed socket as PVC leather is being attached to the rim. --- The process was repeated for the residual limb on the other side, yielding a set of two thermoformed plastic water bottle sockets. A simple harness was fashioned by attaching a cloth strap to each socket with [rivets](https://en.wikipedia.org/wiki/Rivet), and a buckle slider to allow for tightening or loosening the straps.  ###### A simple harness is fashioned to connect the two sockets, and to aid in preventing the sockets from slipping off of the patient. --- ### Creating the 3D Printed End Effector We used an end effector design that Rajab had created for a previous patient.  ###### A previous patient at LVDC utilizing the end effector, and a similarly-thermoformed socket. --- The effector consisted of two parts: a stubby, tapered cylindrical base that is adhered directly to a bottle cap, and piece that slides onto the base that features two thermoformable prongs. The two pieces are designed in a way that allows the second piece to snap and lock onto the the first piece, and is removable in order to make it easy to wash. The second piece was dipped into near-boiling water and a spoon was placed between the prongs while the prongs were crimped. As the pronged cooled, they maintained a shape that could securely hold the spoon. A benefit of this prosthetic device design is the intrinsic means by which end effectors can be attached to the socket: simply adhering the effector to a bottle cap and twisting the the cap onto the bottle.  ###### The two-piece 3D printed end effector. Left: The end effector base attached to the water bottle cap. Right: The two-pronged, thermoformable end effector piece in position over the base. --- ### Testing the Prosthetic Device After working on the prosthetic device for the majority of the day, we bought the recipient a meal of rice and beans from a nearby food shack (*see [Mama Mzuka's Lunch Shack](wiki:/u/kreeser1/wiki/Lake+Victoria+Disability+Centre "Lake Victoria Disability Centre")*). The 3D printed end effector required several rounds of thermoforming to properly hold the spoon at an appropriate angle. After a few minutes of practice, he was able to scoop food onto his spoon and get the spoon to his mouth. He was able to do this again and again, with little outside help. We are very proud to say that he was able to feed himself with dignity that day for the first time in two years.  ###### The patient testing his new low-resource prosthetic device over a plate of rice and beans --- After our meal, we tested attaching a Hosmer hook to the thermoformed socket. We ran a line from the Hosmer hook, around his back, and to a makeshift harness secured to the opposite shoulder. In this simple test, he was able to open and close the hook providing proof-of-concept for attaching more sophisticated end effectors to this style of socket.  ###### The 3D printed end effector was replaced by a Hosmer hook for a successful proof-of-concept test. --- The final step of the creation of this low-resource prosthetic device was to finish adhering PVC leather to the outside of the socket to hide the fact that the socket was made from a plastic water bottle. Cosmesis is very important to patients in this part of the world and Rajab does his best to accommodate. ### e-NABLE Community Calls to Action Upper limb prosthetic sockets made from thermoformed plastic bottles are not ideal, but in a low-resource area they may be sufficient. It seems clear to me that the e-NABLE community could do good for the world by creating a line of 3D printable end effectors that could be glued or otherwise adhered to a standard twist-on bottle cap. The built-in feature of the bottle cap screwing onto the bottle allows for the possibility of presenting a recipient with a range of effectors that can pair with their socket, and provide the recipient with new tools in the future as they are developed. I believe the community could do additional good by designing a simple, 3D printable Hosmer hook-type end effector for use with this and other styles of low-resource socket.