A replacement device for resurfacing a joint surface of a femur and a method of making and installing such a device is provided. The custom replacement device is designed to substantially fit the trochlear groove surface, of an individual femur. Thereby creating a xe2x80x9ccustomizedxe2x80x9d replacement device for that individual femur and maintaining the original kinematics of the joint. The replacement device may be defined by four boundary points, and a first and a second surface. The first of four points is 3 to 5 mm from the point of attachment of the anterior cruciate ligament to the femur. The second point is near the bottom edge of the end of the natural articulatar cartilage. The third point is at the top ridge of the right condyle and the fourth point at the top ridge of the left condyle of the femur. The top surface is designed so as to maintain centrally directed tracking of the patella perpendicular to the plane established by the distal end of the femoral condyles and aligned with the center of the femoral head.

1. Field of Invention
The invention relates generally to a replacement device for a knee joint, and more particularly, to a device for resurfacing the trochlear groove of a femur that is customized to an individual and to methods for installing and making the same.
2. Description of the Related Art
The human knee joint primarily includes three parts, anatomically referred to as the femur (thighbone), the tibia (shinbone) and the patella (kneecap). The knee joint is then further subdivided into two joints: the patella-femoral joint (space between the kneecap and distal anterior surface of the thighbone) and the tibia-femoral (space between the thighbone and shinbone).
During normal bending and straightening of the leg, the patella (kneecap) slides over the femur (thighbone) within a groove that is located on the front distal surface of the femur. This groove is referred to as the trochlear groove. Several types of abnormalities can occur with the movement of the patella over the femur. For example, the patella may dislocate or slip out of place, it may fracture, or develop a tracking problem. Normally, the patella tracks, or glides within the central region of the trochlear groove. A tracking problem occurs when the patella no longer remains centered within the groove as it glides over the femur. The resulting abnormal biomechanics can cause chronic pain in the joint and if left untreated, it can lead to degenerative arthritis.
The distal end of the femur (within which resides the trochlear groove) is covered with articular cartilage. This cartilage functions as a cushion between the femur and the tibia. In arthritis of the knee joint, the articular cartilage breaks down, either from abnormal wear as mentioned above, or from injury, age, congenital predisposition, inflammatory arthritis, or obesity, etc. When this cartilage breaks down, the cushion is lost, resulting in pain, swelling, bone spur formation and/or decreased range of motion of the knee joint.
Due to the inability of damaged cartilage to repair itself after injury, the range of treatment for patients with unicompartmental disease involving the patella is limited. The most commonly prescribed treatments included soft tissue releases and/or realignment of the patellar tendon, patellectomy, where the patella is completely removed, or a total knee replacement with a standardized patello-femoral-tibial prosthesis. In certain instances none of these procedures may be desirable or effective. For example, the soft tissue procedures may not work. A patient having undergone a patellectomy is left partially crippled due to the loss of the kneecap, which served to hold the joint together. Additionally, these patients often still suffer from pain due to contact of the remaining tendon moving directly over the groove. A total knee replacement with a standardized prosthesis is also far from ideal because much of the femur bone must be carved away in order to xe2x80x9cfitxe2x80x9d the distal surface of the femur to the standardized prosthesis. Additionally, the patients are often young and are likely to require replacement of the prosthesis. Each revision operation is more difficult. Therefore, there still is a need for a better treatment of patient""s with degenerative arthritis of their patella-femoral joint.
The present invention provides a replacement device that is customized to each individual knee joint. Due to the xe2x80x9cfittingxe2x80x9d of the replacement device to the patient""s femur, instead of the reverse as is the case with standard prosthetic devices, the patient""s original range and force of motion (kinematics) through the knee joint is preserved and the patient does not suffer from device-related pain. Also included is a method for making a customized replacement device and a marking template for such a device. Bone stock removal is limited and functionally is maximized.
The present invention is directed toward a custom replacement device for resurfacing an articulating or joint surface of the femur and methods of making and installing such a device. This custom replacement device overcomes the problems associated with prior knee joint replacement devices or prostheses in that it is made specifically to fit the trochlear groove surface (surface over which the patella slides) of a femur from an individual patient. Thereby creating a xe2x80x9ccustomizedxe2x80x9d replacement device for that individual femur.
The replacement device is substantially defined by four outer points and first and second surface areas. The first of four points is defined approximately as being 3 to 5 mm from the point of attachment of the anterior cruciate ligament to the femur. The second point is defined approximately at or near the superior edge of the end of the natural cartilage. The third point is defined approximately at the top ridge of the right condyle. The fourth point is defined approximately at the top ridge of the left condyle. The first surface area is customized to substantially match the bone surface area of the trochlear groove of the femur. The second surface area has a tracking path that is approximately perpendicular to the end of the condyles of the femur. The thickness between the first and second surface areas may be approximately between 2 mm and 6 mm. To couple the replacement device to the femur, a pin protruding from the first surface area may be used to penetrate an opening in the femur prepared by a surgeon. Boney ingrowth may secure the prosthesis or bone cement may be used.
The replacement device can also include a customized drill guide that is substantially defined by first and second surface areas. The first surface area is customized to the surface area of the trochlear groove of the femur. The second surface area includes a hole that is aligned substantially to the pin to assist in drilling the opening into the femur for the pin.
In accordance with one aspect of the present invention, these and other objectives are accomplished by providing a replacement device having a top surface; a bottom surface; the bottom surface substantially formed to match the trochlear groove surface of a femur; and the top surface substantially tracking the trochlear groove of the femur.
In accordance with another aspect of the present invention, these objectives are accomplished by providing a system for installing a replacement device to a distal end of a femur having a trochlear groove surface, comprising: a marking template, wherein: the marking template has a back side substantially matching the distal end of a femur; and an opening through the marking template; a drilling apparatus to form a hole on the distal end of the femur assisted by the opening in the marking template; and a replacement device, wherein: the replacement device has a bottom side substantially matching the distal end of the femur; and a pin protruding from the bottom side of the replacement device adapted to insert into the hole on the distal end of the femur.
In accordance with yet another aspect of the present invention, these objectives are accomplished by providing a method of making a replacement device, comprising the steps of: forming a model of a distal end of a patient""s femur; forming a first mold from the model, wherein the first mold has a bottom side that substantially matches the trochlear groove of the patient""s femur, wherein the first mold has a top side opposite of the bottom side; coupling a peg on a predetermined location on the bottom side of the first mold; shaping the top side of the mold to substantially track the trochlear groove of the patient""s femur; forming a second mold from the first mold; and pouring viscous material into the second mold to make a replacement device.
In accordance with still another aspect of the present invention, these objectives are accomplished by providing a replacement device having a bottom side that substantially matches the trochlear groove of a patient""s femur, wherein the bottom side of the replacement device has a pin at a predetermined location; providing a marking template having a back side that substantially matches the trochlear groove of the patient""s femur, wherein the marking template has an opening corresponding to the predetermined location of the pin; removing the cartilage from the distal end of the femur; positioning the marking template about the femur substantially similar to the desired installed position of the replacement device; drilling a hole on the distal end of the femur though the opening of the marking template; removing the marking template from the femur; and inserting the pin of the replacement device into the hole of the femur to install the replacement device on the desired location of the femur.
Alternatively, a method of forming a customized replacement device for a femur will include the steps of duplicating the surface of the distal anterior femur from an individual; and using the duplicate to form a back surface of the customized replacement device and/or a customized marking template.

Custom replacement device for resurfacing a femur and method of making the same


An abutment with a molded part for the fastening of actuating pulls, preferably for actuating pulls at the transmission in motor vehicles. The abutment has a base plate with a self-locking wedge, a perforated plate and a stop which protrudes relative to the base plate. A molded part into which at least one cable pull projects and is enclosed and held by the molded part. The molded part has a conical support surface into which the self-locking wedge fits. A guide rod projects into the molded part and can snap into the perforated plate of the abutment. A lock is provided at the molded part and can be unlocked by the stop of the abutment and provides a connection between the abutment and the molded part.

1. Field of the Invention
The invention relates to an abutment with a molded part for fastening actuating pulls.
The abutment according to the invention with a molded part for fastening actuating pulls is particularly suitable for actuating pulls at a transmission in motor vehicles. The forces acting during gear shifting are supported by means of the abutment. The sheath of the actuating pull is fixedly connected with the transmission, and the applied force provides for the required shifting path.
2. Discussion of the Prior Art
In conventional abutments, the end fitting of the cable pull is inserted into an abutment and fastened therein by various mechanisms. These mechanisms can be attachment clamps, retaining rings or clips which are arranged directly on the abutment or end fitting. These solutions known from the prior art have a number of problems reflected in an excessive freedom from play, problems with positioning and compensation of tolerances, secure fixing and the unambiguity or clarity of fixing. There are cases in which the end fitting has not been correctly secured and yet will be functional for a certain time because, due to the tight fit between the abutment and the end fitting, incorrect locking or fixing is not immediately recognizable and is not noticeable until after several hours of operation, so that in the case of automobiles this leads the customer to the conclusion that there were manufacturing defects in the factory. Further, in the solutions according to the known prior art there is increased expenditure on assembly since a number of loosely connected parts are used. Complete accessibility of the parts at the transmission is often not ensured. Therefore, handling is difficult and the assembly force to be applied is restricted. This is particularly true when the space for assembly and disassembly with tools is distinctly difficult to access. In shifting mechanisms with a plurality of cable pulls, this set of problems is compounded, resulting in even more sources of defects.
WO 98/25036 A1 describes an abutment and molded part for fastening actuating pulls comprising a base plate with a conical support surface and a perforated plate identical to the base plate, a molded part into which a cable pull projects, and a guide rod which can snap into the perforated plate of the abutment. Due to the fact that the conical flank is not arranged in the axial direction, there is no freedom from play axially. The conical flank of the device also does not act as a self-locking wedge because, without additional locking, removal of the molded part is possible. Moreover, it is only possible to secure the connection by additional actuation of the locking pin. Accordingly, this device does not provide an uncomplicated connection for the fastening of actuating pulls with economical assembly.
Therefore, it is the object of the present invention to provide a mechanism for the fastening of one or more actuating pulls which enables fastening with economical and no tolerances in a fast, reliable and clear manner even in inaccessible places.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in an abutment having a base plate with a self-locking wedge, a perforated plate and a stop which protrudes relative to the base plate. This abutment should be formed of one part in practice, wherein the work material can be plastic, from which this part can be produced by injection molding in a simple, uncomplicated manner.
A molded part is inserted into this abutment; at least one cable pull projects into this molded part and is enclosed and held by the molded part. Also, this molded part can be a plastic part which simultaneously forms the injection molding around the cable pull. If more than one cable pull is to be fastened, a plurality of cable pulls project into the molded part and are enclosed by the molded part.
The molded part has at least one conical support surface into which the self-locking wedge fits. If the abutment has more than one wedge, the molded part can also have a plurality of conical support surfaces so as to increase stability between the molded part and the abutment.
A guide rod projects into the molded part so that it can snap into the perforated plate of the abutment. In the simplest case, the guide rod, which can have a rounded shape, is arranged in a tubular member, wherein there is a thickening or enlargement positioned at one end by which the guide rod can be pulled out in opposition to spring force, and the other end has a wedge shape. The guide rod is pulled out of the molded part, and the spring is tensed in the tube. A lock is arranged so as to be displaceable transverse to the movement direction of the guide rod, the guide rod being supported against a part of the lock in the tensioned state. The other part of the lock has an opening through which the front part of the guide rod can slide. When the lock is moved so that the opening frees the path of the guide rod, the guide rod slides through the lock so as to be propelled by spring force. It is possible to have a plurality of guide rods for high stability between the abutment and the molded part. However, it is also possible to connect a plurality of wedge-shaped ends with a guide rod.
The guide rod is to be pulled out before the molded part is connected with the abutment, wherein the spring is tensioned and the guide rod is held in the tensioned position by locking.
The guide rod is advantageously arranged in the direction opposite to the cable pull or cable pulls. If this is not permitted by the free space for assembly, it is also possible to arrange the lock on the same side as the cable pull.
When mounted, the molded part is pressed in the direction of the abutment, wherein a stop at the abutment acting against the locking of the molded part displaces the molded part so that the guide rod slides through the hole of the lock and, because of its shape, completely opens the lock and slides into the hole of the perforated plate and, in so doing, connects the abutment with the molded part, locking them together.
In this respect, the hole in the perforated plate is advantageously formed in such a way that it has a wedge shape into which the wedge of the lock can slide such that an especially good connection of the two parts is brought about. This is the case particularly when it also has a wedge shape opposite to the wedge face.
Due to the fact that the lock and perforated plate as well as the abutment and molded part have wedge-shaped elements sliding into one another, the device according to the invention ensures a correct and perfect fit. It is also ensured that no unnecessary play occurs and an automatic and continuous readjustment is carried out when wear occurs. Mounting is guaranteed at poorly accessible places due to the spring which acts automatically to a great extent and connects the two elements with one another securely and reliably. During disassembly, the guide rod, whose length is adapted to the assembly and disassembly conditions, enables simple detachment of the two parts from one another in an economical manner. The compact and robust construction forms a relatively simple open-closed tool.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

Abutment with molded part for fastening actuating pulls