In the context of the present invention, a prosthesis is a manufactured device for replacing a missing part of a body, such as a limb or portion thereof. There are two basic types of prosthesis: exoskeletal and endoskeletal. An exoskeletal prosthesis, also called a crustacial prosthesis, is supported by a rigid outer shell. An endoskeletal prosthesis is supported by internal support members. That is, structural support is provided by members inside the prosthesis.
Endoskeletal protheses are rapidly growing in popularity. A need exists for a reliable and efficient device and method that does not require a high degree of specialized equipment and/or skill for attaching an endoskeletal prosthesis to a patient, such as to the patient's molded stump socket or bandage wrap stump socket.
A stump socket is typically made by molding material around a person's stump or a positive model of the stump thereby forming a prosthetic socket or stump socket that can be worn by a patient over the stump and a remaining portion of a person's limb. Once the socket has been manufactured, or while it is being manufactured, it is secured to an attachment device which is then mounted to the endoskeletal prosthesis, typically by molding a portion of the stump socket to the attachment device.
A bandage wrap stump socket is made by applying activated plaster or resin bandage material over a person's stump and adjacent residual limb after an amputation operation.
Two types of attachment devices are known in the prior art. One type of attachment device that is commonly utilized to mount the stump socket to the prosthesis, shown in FIG. 3, is a flat metal disc or plate 30, typically having four threaded holes. The metal disc or plate can be round or square. Typically, the prosthesis is bolted or secured by other suitable threaded fasteners to the coupler thereby providing an artificial limb for the patient to wear. In order for the metal disc to be more securely attached to the stump socket, thermoplastic or other suitable material is molded around the periphery of the metal plate and around the bottom side of the metal plate opposite the side at which the persons' stump is to be located. Otherwise, the socket would detach more easily during use especially if a thermoforming resin is used. Thermoforming resins, such as polypropylene are especially difficult to use because such resins shrink when cooled. This bottom side is the same side to which the prosthetic device attaches to the plate by means of threaded fasteners. Thus, there is a layer of thermoplastic material between the plate and the end of the prosthetic device through which the fasteners pass to secure the prosthetic device to the plate. Since plastic material is sandwiched between the metal attachment plate and portion of the prosthesis attached to the plate, which is usually also metal, the plastic typically will deform under load and ,causes the socket to become loose. Some metal plate attachment devices have knurls on their side surfaces to facilitate attachment of the plate to the thermoplastic of the socket, but it is still necessary for the thermoplastic to be formed around the bottom side of the plate.
The flat metal plate attachment device poses an additional problem. During fitting to a patient, it is difficult to locate the metal plate on either the stump or on a positive model of the stump in the desired orientation. Since stumps and therefore the stump models typically have rounded ends, the flat metal plate device must be maintained in the desired orientation on the rounded end of the stump and/or stump model during the placing and at least partial curing of the moldable material around the metal plate and the socket. This balancing of the metal plate device is difficult, time consuming and skill intensive.
The second known attachment device is a wood attachment block 27, illustrated in FIG. 4. In order to fit the block to a patient, top surface 28 of wooden block 27 is carved out to fit the contours of the patient's stump socket. Typically, this requires a high level of skill and is time intensive. In addition, to secure the contoured wood block to the stump socket, thermosetting resins are typically used for the required adhesion to wood. These resins are difficult to work with because they are generally liquid and also are time consuming and toxic. Thus, not only is the fitting of wooden attachment blocks skill and time intensive, but it typically requires the use of toxic material to attach the block to the stump socket. Thermoforming resins are generally not suitable for wood attachment blocks.
Therefore, a need exists for a prosthetic attachment device that securely attaches to a prosthetic socket or stump socket without the aforementioned limitations. In addition, a need exists to reduce the amount of time and skill needed to attach an endoskeletal prosthesis to a prosthetic or stump socket. A need exists that permits use of thermoforming resins (especially polypropylene and transparent resins) without extending the resin over the bottom of the attachment device.