Prostheses (or prosthetics) are artificial devices that replace body parts (e.g., fingers, hands, arms, legs). Generally, prostheses may be used to replace body parts lost by injury or missing from birth. The quality of prostheses has greatly improved in recent years. For example, a prosthetic limb may be molded to have the same shape and density as the person's remaining limb. In addition, elastomeric polymer skins may be used to form the prosthetic limb and give the prosthetic limb a life-like appearance. As another example, improvements in prosthetic limbs may allow for increased feedback and movement.
However, prosthetic limbs still present numerous challenges, particularly in the area of looking and performing as the actual human limbs being replaced. An intact human foot, connected to its ankle, travels through stance and swing phases of a gait cycle during each stride of motion, whether the motion involves walking, jogging, or running. In order to provide higher performance prosthetics, prosthetic feet made of composite materials are often used to provide the energy return characteristics desired by an amputee. For example, a leaf spring composite prosthetic foot may provide desirable characteristics for a foot amputee.
In order to improve the appearance of prosthetic feet, the prosthetic feet are often covered with a cosmetic foot shell that forms an open cavity around the functional prosthetic foot structure. Existing foot shells may be thin-wall hollow shells that do not enhance the prosthetic foot function and often diminish prosthetic foot response. For example, these existing foot shells may be made of polyurethane, PVC (polyvinyl chloride), silicone or other plastics and rubber substitutes. One common problem with foot shells is the internal cavity of the foot shell does not securely hold the prosthetic foot, composite leaf spring foot or other prosthetic foot elements in place which causes the foot to be loosely connected to the foot shell and amputee's shoe. This lack of a secure connection may impede feedback to the user and decrease overall performance of the prosthetic foot.
Reference will now be made to the examples illustrated in the drawings, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the technology is thereby intended. Alterations and further modifications of the features illustrated herein, and additional applications of the examples as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure are to be considered within the scope of the description.
The present technology provides a prosthetic foot cover with an integrated framework, lattice framework(s) or lattice networks. The integrated frameworks and lattices can be made using an additive manufacturing process or a 3D (three-dimensional) printing process. The integrated lattice frameworks may be made of an elastic polymer, another flexible material or a semi-rigid polymer material that can used in a 3D printing process.
Additive manufacturing (AM) may be used to create intricate lattice structures to meet a wide variety of design requirements in a prosthetic limb. AM offers the opportunity to create generative lattice structures for a variety of prosthetic foot designs. Intricate lattice features that were once difficult to produce using injection molding can now be integrated into prosthetic limbs to optimize performance. The benefits of lattice structures can be further used to enable mass customization of prosthetic limbs and more specifically prosthetic feet.
Most prosthetic feet have been covered with a cosmetic foot shell that creates an open cavity around the foot structure. In the past, foot shells have been thin-wall hollow shells that do not enhance the prosthetic foot function and often diminish prosthetic foot response. These thin walls were also solid walls. A common problem with foot shells is that the internal cavity does not securely hold the prosthetic foot elements (e.g., composite leaf spring) of a prosthetic foot in place which may cause the foot to only be loosely connected to the cosmetic foot shell and may impede feedback to the user. Therefore, a secondary foam filler may be used to fix the prosthetic foot in place within the foot shell in order to remedy this issue, but this foam filler tends to inhibit the movement of the prosthetic foot inside the shell.
An outer membrane layer 108 may be disposed over the lattice foot framework 106 to cover and support the lattice foot framework 106. The prosthetic foot cover may have a thin-wall lattice membrane to cover the lattice foot framework. The outer membrane layer 108 may also be removable. In another configuration, the outer membrane layer 108 may be fixed to or additively formed with the lattice foot framework 106. The lattice structure of the lattice framework 106 may be a uniform lattice where the lattice sub-shapes are uniform in size. Alternatively, the lattice foot framework 106 may include lattices of varying sizes 120, as will be discussed in more detail later.
In the past, passive prosthetic foot systems have had limited potential to adjust the functional characteristics of the prosthetic system since the systems have often relied on elastomeric inserts in a foot cover to achieve a desired response. In the present technology, the foot cover can be used to adjust the prosthetic foot and may be utilized as a functional member of the foot system to provide enhanced performance to an amputee. The foot cover can also offer a means to regulate and control the foot system by controlling the density of the lattice that is used. The design of lattice foot structure may be tailored to provide a specific compliance (or stiffness) so that the entire gait cycle is optimized to the user's needs.
In one configuration of the technology, the foot cover may be additively manufactured by selective laser sintering (SLS) which fuses a polymer powder or plastic powder (e.g., nylon or polyamide) laid down in powder layers into a foot cover structure using a computer guided laser that activates layers of the powder. This configuration of the present technology allows the lattice foot framework to be created using SLS but since the outer membrane layer is separate, this allows the outer membrane layer to be removed and the polymer powder can be easily emptied from the lattice. Otherwise, if the outer membrane layer and lattice are manufactured together using SLS, the powder and its added weight may be difficult to remove from the foot cover. The outer membrane layer can be removed after the outer membrane is manufactured in the same powder volume or powder stack, or the outer membrane layer can be manufactured separately so that the powder can be removed from lattice foot framework.
Alternatively, the outer membrane layer can be exchanged for any outer membrane layer that is made by any manufacturing process (e.g., additive, injection, or otherwise). This may provide any cosmetic appearance that an amputee desires. For example, a foot cover can be provided that is larger than the lattice foot framework. Then the foot cover can be placed over the lattice foot framework and the foot cover can be heated (e.g., boiled in water or using heated air) to shrink the foot cover to fit over the lattice foot framework.
The lattice foot framework 108a, 108b and the prosthetic foot 104 may be inserted into or covered by the outer membrane layer 106. The lattice foot framework 108a, 108b and the outer membrane layer 106 may be a single unit, as illustrated, in order to cover the prosthetic foot 104. For example, the lattice foot framework 108a, 108b and the outer membrane layer 106 may work with the prosthetic foot 104 as a system to tune the total response of the prosthetic foot.
The foot cover may be composed of lattice structures with mechanical properties that can be used to enhance the functional characteristics and responsiveness of the prosthetic foot. For example, the foot cover may have a lattice structure that become an integral part of the prosthetic foot. The lattice structures may enable a specific desired response to be integrated into the foot cover. One configuration of this technology incorporates a uniform lattice structure which provides a predictable response due to the homogeneous density. Another variation uses a combination of different density lattices of various densities to generate a variable dynamic response for optimizing the functional characteristics for the user. For example, a first density of lattice cells may exist in a first area and second density of lattice cells may exist in a second area to provide separate response in each area.
The open cavity design may be lighter than the lattice foot framework depending on the internal support used. The open cavity design may accommodate a variety of internal structures. The internal structures may be a variety of configurations, such as leaf springs, which can be altered to meet design parameters for a specific amputee. In the case of using resilient leaf springs for the support structure, the resilient leaf springs may offer better cyclic performance (i.e., long-term durability) over time.
In some configurations as described earlier, the lattice structure may be a variable lattice structure where portions of the lattice structure have a different density of the mesh and wall thickness as compared to other parts of the lattice structure. The lattice foot framework may have a variable material stiffness in separate areas throughout the cover due to the ability to create customizable lattice density and member thickness by using an additive manufacturing process. The material stiffness can be tuned and optimized to maximize desirable performance characteristics such as energy return or high frequency vibration dampening.
The additive manufacturing process enables the cover and the cavity formed by the sidewall support layer 1102 to be custom fit to each prosthetic foot model. This prosthetic foot shape may vary from user to user, activity to activity or from year to year as the prosthetic foot design changes. Being able to conform the cover to the prosthetic foot, enables the foot cover to: better stay on the prosthetic foot, provide a more natural look and provide a more natural feel when walking or running.
The lattice structure illustrated in
The lattice structure illustrated can match the stiffness of polyurethane foam by tuning lattice density and member thickness. For example, some structure arrangements of the open lattice structure may target the stiffness of the foam to within 1% to 10% of the stiffness of the foam. In this example, the open lattice foot cover may be made of thermoplastic polyamide elastomer that uses polyamide for hard segments and polyether for soft segments that replicate the response of polyurethane. In addition, the lattice structure may be able to approximate the stiffnesses of many linear elastic materials (e.g., natural rubber, synthetic rubber, silicone rubber, aluminum, steel, etc.).
A solid support ring 1308a-b in the inner cavity 1310 can be provided at locations where a foot plate from the prosthetic plate is expected to contact the inner cavity 1310. This solid support ring 1308a-b can increase rigidity and prevent the prosthetic foot from stretching the foot cover out. The solid support ring 1308a-b may also prevent the foot cover from becoming loose.
This foot cover allows variable stiffness along the length or on the height by varying the density of the open lattice structure. Customizable stiffness in certain areas may be provided for an amputee as needed. In addition, the open lattice structure may be customizable for an amputee for their anatomy, by their weight or for specific activities.
In addition, a heel pad 1304 may be formed at the base of the heel area for the foot cover 1300. The size, depth and dimensions of the heel pad may be varied depending the desired characteristics of the foot cover. A solid heel block 1310 can help avoid the propagation of lattice failure because the heel of the foot may otherwise produce loads that can start to propagate cracks through the lattice structure. In addition, a solid heel block 1310 or internal heel core may stop the propagation of failure at the sharp corner of the heel which can otherwise start to propagate cracks under load. Such solid pieces in strategic locations can increase the fatigue life and durability for the heel pad and overall heel.
The use of an open lattice design allows for easy evacuation of liquids and foreign objects (e.g., dirt, rocks, sticks, etc.) that may enter the lattice framework. The drainage of the open lattice design can be very useful in a submerged liquid setting such as in boating, at the beach, in the pool, during scuba diving, etc. In the past, other solid foot covers have acted like a bucket by filling with water and the amputee then has to remove the foot cover to drain the foot cover of water. Such problems are avoided with an open lattice framework.
An open lattice design for a foot cover also allows for simple cleaning of the foot cover with water or compressed air because water or air can easily enter the lattice for cleaning and then drain out or leave the open lattice framework. Such cleaning may take place without having to remove the prosthetic foot cover.
In addition, the open lattice structure may be manufactured by selective laser sintering of powder (as described earlier) to make the lattice structure. The open lattice structure makes removing or evacuating the powder from the selective laser sintering process straightforward because the unused powder can more easily escape from the open lattice structure.
The open lattice design also allows the weight of the cover to be optimized while still maintaining critical performance characteristics, such as strength, resilience and durability. Furthermore, when the open lattice structure is manufactured as a single-piece design then any need for additional hardware to affix or hold the foot cover on the prosthetic foot is avoided.
While
A lattice framework can also be incorporated in activity specific footwear and soles can be created using a lattice structure, which enables better adaption by amputees. In addition, amputees may no longer be restricted to only wearing existing types of shoes over a foot cover. For example, instead of providing a foot cover that looks like a human foot, a foot cover that looks like a shoe and has a sole with a lattice structure may be manufactured. In another example, the foot cover may have the appearance of a foot and a shoe may be worn over the foot cover but both the lattice framework in the foot cover and the shoe sole may be tuned for the individual amputee and the activities in which the amputee participates. Thus, customized sport soles can be designed for activity specific products to optimize user performance.
Prosthetic users can benefit from mass customization where the clinician may specify the desired compliance of the system for the user based on the results of a clinical evaluation. Therefore, the clinician can digitally select the design features to be incorporated into the prosthetic foot cover to achieve the desired foot response and then use generative design software to optimize the prosthetic foot cover for the user. The clinician can further adjust and fine tune the prosthetic device by creating a customized foot cover for the patient.
The lattice frameworks can also be used for creating mid-soles and outer soles which are designed for specific uses and for the shoes which are used with the prosthetic foot systems. With the advent of mass customization in shoes, the midsole of shoes may be generated and integrate into the overall prosthetic foot system. For example, sport specific soles which may incorporate a lattice structure tuned for participating in sporting events and such soles can be fabricated via AM (additive manufacturing).
The ability to create custom foot lattice structure enables the selective integration of complex lattice structures into a foot cover to regulate and control foot performance. For example, the lattice structure or lattice density can be discretely positioned throughout the prosthetic foot cover to achieve a desired response according to the user's needs and to produce a controlled response.
An Infinitely Variable Lattice Structure (IVLS) also provides the ability to selectively modify and alter the density/geometry of regions of the lattice foot framework to achieve the desired functional characteristics of the prosthetic foot.
In addition, the rollover characteristics of the foot system can be regulated and tuned by strategically positioning the lattice structure throughout the foot cover. For example, the tuning of the prosthetic foot may be considered a Lattice Tuned Design (LTD). Hollow chambers or highly compliant lattice structures can be used on the plantar surface of the cover to function as shock absorbers.
Another aspect of passive prosthetic foot systems is that there is limited potential to adjust the functional characteristics since they often rely on elastomeric inserts to achieve a desired response. Therefore, the present foot cover can be used to adjust the prosthetic foot and can be utilized as a functional member of the foot system which provides enhanced performance. The foot cover can also provide a means to regulate and control the foot system.
The present technology consolidates many individual parts in a single assembly and this in turn may reduce the part count of the prosthetic foot and result in better reliability. For example, a prosthetic foot cover, a lattice, a negative pressure pump and a customizable heel dampener may be contained within one prosthetic foot cover or within a monolithic device created using a single additive manufacturing or printing process.
Even though this technology described above refers to a foot, the same invention can be used in any type of prosthetic or robotic limb flexion device (e.g., any robotic joint). Alternatively, this technology described may be connected to a prosthetic knee system.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more examples. In the preceding description, numerous specific details were provided, such as examples of various configurations to provide a thorough understanding of examples of the described technology. One skilled in the relevant art will recognize, however, that the technology can be practiced without one or more of the specific details, or with other methods, components, devices, etc. In other instances, well-known structures or operations are not shown or described in detail to avoid obscuring aspects of the technology.
Reference was made to the examples illustrated in the drawings, and specific language was used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the technology is thereby intended. Alterations and further modifications of the features illustrated herein, and additional applications of the examples as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the description.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more examples. In the preceding description, numerous specific details were provided, such as examples of various configurations to provide a thorough understanding of examples of the described technology. One skilled in the relevant art will recognize, however, that the technology can be practiced without one or more of the specific details, or with other methods, components, devices, etc. In other instances, well-known structures or operations are not shown or described in detail to avoid obscuring aspects of the technology.
Although the subject matter has been described in language specific to structural features and/or operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features and operations described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. Numerous modifications and alternative arrangements can be devised without departing from the spirit and scope of the described technology.
This application claims benefit of U.S. Provisional Patent Application Ser. No. 62/948,611, filed Dec. 16, 2019 and U.S. Provisional Patent Application Ser. No. 62/948,621, filed Dec. 16, 2019, both of which are incorporated herein by reference.
Number | Date | Country | |
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62948621 | Dec 2019 | US | |
62948611 | Dec 2019 | US |