The present disclosure relates to a prosthetic device. In particular, the present disclosure relates to a finger prosthetic designed for partial finger amputees.
Digital amputation is a common injury that affects many individuals worldwide. In the United. States alone, it is estimated that about a quarter of a million individuals have non-thumb digital amputations. These injuries often result in extensive functional disability and a substantial social and economic cost to the society. More importantly, the outcome of digital dysfunction is detrimental to individual's daily activities, such as buttoning a shirt or unlocking a door. Therefore, the overall goal for these individuals is to rebuild a finger with restoration of normal function, stability, length, and sensation.
Amputees often have trouble with performing basic tasks, such as typing on a computer or gripping an item. Several devices exist to assist individuals with amputations. However, there are very few options available for individuals with amputations distal to the proximal interphalangeal (PIP) joint. Additionally, the custom-fit nature of existing prosthetic devices typically requires extensive machining techniques and hands-on labor, which drive up the cost of the prosthetic device.
Most prosthetic devices are produced by creating a mold of the individual's residual limb, which is then used to create a plaster cast. In turn, the plaster cast is then modified as needed before finally pulling a thermoplastic over the plaster cast to create a socket, where the residual limb is inserted. The socket is attached to one or more off-the-shelf and/or custom machined parts.
Often, the socket will not fit comfortably on the first attempt. Consequently, the process is repeated with further alterations made during the plaster cast modification stage. Additionally, the production of the mold often involves discomfort for the individual as it may involve wrapping their residual limb in plaster tape and holding until dry. The plaster cast created is prone to deformation and degradation over time, which may necessitate repeating the process numerous times. The process of iteration and alteration involves time consuming, hands-on skilled labor and thus drives up prosthetic cost.
Furthermore, existing prosthetic devices often use motors and batteries to support the finger through movement. The use of motors and batteries in a finger prosthetic device is undesirable for several reasons. For example, these devices increase complexity, are unreliable and more expensive to maintain (e.g., the motor may eventually fail).
Accordingly, there exists a critical need for a reliable, low-cost prosthetic device that can return normal functionality to an amputee.
Shown and described is a finger prosthetic that does not utilize batteries nor motors to power prosthetic movement. The finger prosthetic may be attached to an individual's hand and/or a portion of the amputated finger. Compared to the above prior attempts, the presently disclosed device solves the problems of current state of the art, meets the above requirements, and provides many more benefits.
In one aspect, disclosed is a novel finger prosthetic. In one embodiment, the finger prosthetic includes a midsection, a fingertip portion, and a ring. In this embodiment, the midsection, the fingertip portion, and the ring could be 3D printed.
The finger prosthetic includes a torsion spring system that comprises a fabricated torsion spring, a cable, and a pin. This torsion spring is embedded in the prosthetic distal interphalangeal (DIP) joint and applies a moment sufficient to passively extend said joint. This passive extension is in opposition to the active flexion of the prosthetic DIP joint. The active flexion is body powered; when the user flexes their proximal interphalangeal (PIP) joint, a cable transmits tension through the device which applies a moment in opposition to the torsion spring thus flexing the prosthetic DIP joint. The utilization of the torsion spring system embedded in the hinge is novel in the field of Distal Interphalangeal prosthetics. No known device utilizes such a spring system for the purposes and functions disclosed herein.
In one embodiment, an individual could wear the finger prosthetic by inserting their residual limb into the finger prosthetic. Once inserted, the end of the individual's residual limb is positioned in a socket formed in the finger prosthetic and the ring is positioned around the base of the residual limb. The ring provides stability to the rest of the finger prosthetic by resisting axial and angular displacement. The ring is attached to the midsection and the fingertip portion of the finger prosthetic via two lateral struts in one embodiment. Each strut has a hinge joint aligned with the individual's PIP joint so as not to obstruct flexion of the joint.
The midsection and the fingertip portion could interface via a hinge joint serving as a prosthetic distal interphalangeal (DIP) joint. This hinge joint is passively extended by a 90-degree torsion spring and can be actively flexed via a cable, which transmits tension whenever the individual flexes their PIP joint.
When the individual flexes their PIP joint, tension is generated in the cable and the cable pulls on the prosthetic fingertip thus flexing the prosthetic DIP joint simultaneously. When the individual wishes to extend the prosthetic DIP joint, he/she simply extends the PIP joint, causing the torsion spring to extend the prosthetic DIP joint. When the PIP joint is at rest, the cable will release the tension and the torsion spring will cause the DIP joint to extend to its upright position.
Again, depending on the embodiment, the device uses flexion of the PIP joint at the interface with the midsection to create tension in the cable. This tension compresses the legs of the torsion spring together and forces the device to bend at the positioned joints. When the individuals's appendage is relaxed, the tension in the cable is released, causing the embedded torsion spring to return to its natural position at 90 degrees.
The above objects and advantages are met by the present invention. Any combination and/or permutation of the embodiments is envisioned.
In addition, the above and yet other objects and advantages of the present invention will become apparent from the hereinafter-set forth Brief Description of the Drawings, Detailed Description of the Invention and claims appended herewith. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the present disclosure. These features and other features are described and shown in the following drawings and detailed description.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
So that those having ordinary skill in the art will have a better understanding of how to make and use the disclosed composition and methods, reference is made to the accompanying figures wherein:
The present disclosure is directed to a new finger prosthetic. Although discussed herein with respect to a finger prosthetic for individuals with amputations distal to the proximal interphalangeal (PIP) joint, it should be understood that the mechanism by which the present invention functions (a torsion spring acted on by a cable in tension with a surrounding hinge system) can be used at other finger joints.
As discussed above, partial hand amputations are the most common amputation, accounting for 75 percent of all traumatic amputations. In 2005, 1.6 million persons were living with the loss of a limb. Over 500,000 people were affected by amputation of the hand or fingers in the United States in 2005. There are very few options available for individuals with amputations distal to the PIP joint. Therefore, the disclosed prosthetic design will serve to return normal functionality to an underserved portion of the finger amputee demographic. There is a limited number of companies producing prosthetics for amputations distal to the PIP joint. These current devices have many limitations as discussed herein that the present device overcomes. Additionally, the custom-fit nature of prosthetics typically requires extensive machining techniques and hands-on labor which drives up the cost of the prosthetic.
In fact, as many as 20% of nonmilitary amputees report an unmet need for rehabilitation services, largely because of inability to pay. In the present design to reduce cost and production time, all major components will be 3D printable. This allows for a more affordable and efficient process for size adjustment, refitting, and production.
In one embodiment, the present finger prosthetic is attached to the outside of the individual's hand. The subject wears the prosthetic by inserting their residual limb into the mechanism. Once inside, the end of the subject's residual limb will be in the device's socket and the base of their residual limb will have a ring around it. The ring provides stability to the rest of the prosthetic by resisting axial and angular displacement. The ring is attached to the body of the prosthetic via two lateral struts. Each strut has a hinge joint aligned with the subject's PIP joint so as not to obstruct flexion of said joint.
As further described herein, the body of the prosthetic device contains two segments: the midsection and the fingertip. These two segments interface via a hinge joint serving as a prosthetic DIP joint. This hinge joint is passively extended by a 90-degree torsion spring and can be actively flexed via a cable which transmits tension whenever the subject flexes their PIP joint. In short, when the subject flexes their PIP joint, tension is generated in the cable and the cable pulls on the prosthetic fingertip thus flexing the prosthetic DIP joint simultaneously. When the subject wants to extend the prosthetic DIP joint, they simply extend their PIP joint, causing the torsion spring to extend the prosthetic DIP joint. When the PIP joint is at rest, the cable will release the tension and the torsion spring will cause the DIP joint to extend to its upright position.
The present device is designed in such a way that production involves significantly less hands-on labor and is less physical invasive for the individual than compared to traditional methods. To produce the prosthetic device, 3D scans of the individual's residual limb are acquired and imported into Computer Aided Design (CAD) software along with the device's assembly.
Once in this CAD environment, the device's size and shape can be easily manipulated to fit the shape of the individual's residual limb. This 3D model can then be 3D printed. The only components which need to be added by hand are the tensile cable, the aluminum pin, and the spring which extends the prosthetic DIP joint. This production process serves to reduce hands-on labor and therefore cost while also reducing invasiveness and improving turnaround times.
The ring, midsection, and fingertip of the prosthetic, depending on the implementation, is constructed from 3D printed pieces and will also include a cable, spring, aluminum pin, and socket portion. Once assembled, the prosthetic can flex and relax by utilizing a cable.
The aforementioned mechanism containing the torsion spring and cable apparatus is a novel feature in the present prosthetic. Other companies have utilized the body powered feature, but competitor's prosthetics rely upon more complicated mechanisms with many moving parts. These mechanisms have more areas of friction, more parts to fabricate, and more failure modes. The present mechanism stresses simplicity to maximize strength and production efficiency while minimizing failure modes. Also, due to the mechanism of the device, the prosthetic can be synthesized without the use of a mold kit, which is typically necessary for other prosthetic syntheses. The dimensions of the prosthetic can be tailored per individual by 3D scanning the hand of the subject and then creating the device in a CAD program. This process saves on both time and money and creates a more accurate blueprint to create the prosthetic with. The cost of fabricating mold kits not only makes it more difficult for the consumer but increases the difficulty of the designer. Having a model of the residual limb in the virtual space allows for real-time fitting and accommodation of the irregular geometries present at the residual limb.
Again, the combination cable and spring system used for flexion and extension of the prosthetic DIP joint is wholly unique from other finger prosthetics. All major components of the device (ring, midsection, fingertip) are designed to be 3D printable. This is notable because if one were to completely 3D printable any other currently commercial finger prosthetic, it would not work as intended because of the complexity of the current prosthetic's working mechanisms and motors. Therefore, the present device is uniquely capable of taking advantage of 3D printing during its production. Most prosthetics are produced by creating a mold of the subjects residual limb which is then used to create a plaster cast which is then modified as needed before finally pulling a thermoplastic over the plaster cast to create the socket (where the residual limb is inserted). This socket is then attached to one or more off-the-shelf and/or custom machined parts.
As previously discussed above, the socket often will not fit comfortably on the first attempt and the process starts again with further alterations made during the plaster cast modification stage. Additionally, the production of the mold often involves discomfort for the subject as it may involve wrapping their residual limb in plaster tape and holding until dry. Problematically, the plaster casts created are prone to deformation and degradation over time which may necessitate starting the process from the beginning. The present device is designed in such a way that producing it involves significantly less hands-on labor and less invasive for the subject than traditional methods.
To produce the device, 3D scans of the subject's residual limb are acquired and imported into Computer Aided Design (CAD) software along with the present device assembly. Once in this CAD environment, the device's size and shape can be easily manipulated to fit the shape of the subject's residual limb. This 3D model can then be 3D printed. Again, the only components which need to be added by hand are the tensile cable and the spring which extends the prosthetic DIP joint. This production process serves to reduce hands-on labor and therefore cost while also reducing invasiveness and improving turnaround times.
Adverting to the Figures,
The midsection 12 includes a sidewall 22 that defines a chamber 24. The bottom end 16 of the midsection 12 includes an edge 26 that defines an open end of the chamber 24. The sidewall 22 includes a lower substantially cylindrically portion 28 with two diametrically opposed cut-outs 30 (
Referring to
With reference to
Referring to
The fingertip portion 18 includes a top end 54 and a bottom end 56 with an upwardly angled wall 58. The bottom end 56 includes a pair of inner knuckles 60 (
The finger prosthetic 10 could include a cable 64 made of any suitable material, such as polyethylene, and a torsion spring 66. The cable 64 is attached to the ring 20 and runs through the midsection 12 to its other attachment point at the distal end of the fingertip portion 18. The torsion spring 66 is embedded at ninety degrees in the DIP joint between the midsection 12 and the fingertip portion 18. It will be understood that the torsion spring 66 could be embedded at other angles.
One embodiment of a method to produce the finger prosthetic 10 is discussed below. A 3D scan of the individual's limb is used to acquire the inner dimensions where the residual limb interfaces with the prosthetic. It will be understood that residual limb is defined as the remaining appendage after the injury or amputation occurs. The 3D scan is placed in a computer aided design (CAD) software and used to model the socket of the midsection 12 where the residual limb will be inserted. This method ensures that the shape of the midsection interface and the diameter of the ring 20 provide an appropriate fit.
To maintain average finger length, the dimensions of the finger prosthetic 10 are approximated using the remaining fingers. For example, if an individual is missing their left index finger, the finger prosthetic 10 will approximate the length of the right index finger, if applicable. The midsection 12 and the fingertip portion 18 of the finger prosthetic 10 are modeled to have a length and thickness comparable to those of the individual's intact finger, per previously acquired 3D scans. The ring 20, the midsection 12, and the fingertip portion 18 are 3D printed on a suitable printer, such as a Markforged Mark II printer, using suitable material, such as a Markforged Onyx material, with continuous carbon fiber. In another embodiment, the 3D scan may be performed on a mold that the individual creates at home.
The method allows for at-home substitution of individual parts in the event that a certain part becomes damaged. The fingertip portion 18, the midsection 12, and the ring 20 are 3D printed in one embodiment, which facilitates the printing of a replacement part.
One embodiment to assemble the finger prosthetic 10 is discussed below. The midsection 12 and the ring 20 are snapped into the interlocking mechanisms of the respective parts. This will create the proximal interphalangeal joint and act as the hinge, where the finger prosthetic 10 will flex with the residual limb. The fingertip portion 18 is then attached by first inserting the spring 66 into the midsection 12 and the fingertip portion 18, then sliding the aluminum pin or pin 68 through the holes in the spring 66, the fingertip portion 18, and the midsection 12. This will create the distal interphalangeal joint of the finger prosthetic 10.
The cable is run from the fingertip portion 18, down through the midsection 12, and the ring 20. Once the cable 64 is run from top to bottom, the cable 64 is looped through the ring 20, the midsection 12, and the fingertip portion 18, where a knot can be tied between the two ends at the top of the fingertip portion 18. The remaining cable is trimmed.
The finger prosthetic 10 uses flexion, as shown in
It will be understood that the present invention will function and can be adapted for any joint in the body, which can be approximated as a revolute joint so long as there is a neighboring proximal joint, which can be flexed to generate tension in the cable. Additionally, the present invention can work for multi joint systems. For example, if an individual undergoes a finger amputation proximal to the PIP joint, the present invention can be used to simulate the motions of both the DIP and the PIP joint. In this case, the tension in the cable to simulate flexion may be generated by the flexion of the wrist or by the flexion of the PIP joint on a neighboring finger.
Although the invention herein has been described with reference to embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention.
It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.
The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 62/879,020 filed on Jul. 26, 2019 the disclosure of which is hereby incorporated herein by reference.
This invention was made with government support under Agreement No. 90RE5021-04-00 awarded by the National Institute on Disability, Independent Living, and Rehabilitation Research. The government has certain rights in this invention.
Number | Date | Country | |
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62879020 | Jul 2019 | US |