Abstract: A prosthetic joint assembly that includes a shell including an inner surface. The assembly also includes a bearing member including an outer surface. The bearing member is received by the shell such that the outer surface of the bearing member is adjacent the inner surface of the shell. Furthermore, the joint assembly includes a compressible member that is rigidly fixed to the inner surface of the shell or the outer surface of the bearing member to only cover a portion thereof. The compressible member is made of a material that is different from the shell or the bearing member.

Abstract: The present invention discloses methods for enhancing the wear-resistance of polymers, the resulting polymers, and in vivo implants made from such polymers. One aspect of this invention presents a method whereby a polymer is irradiated, preferably with gamma radiation, then thermally treated, such as by remelting of annealing. The resulting polymeric composition preferably has its most oxidized surface layer removed. Another aspect of the invention presents a general method for optimizing the wear resistance and desirable physical and/or chemical properties of a polymer by crosslinking and thermally treating it. The resulting polymeric compositions is wear-resistant and may be fabricated into an in vivo implant.

Abstract: A joint prosthesis device comprises a head configured to fit within a cup and in one embodiment includes a first member for attachment to a first bone in a joint and including a first articulation surface portion defined by a first radius of curvature and a second member for attachment to a second bone in the joint and including a second articulation surface portion defined by a second radius of curvature and a third articulation surface defined by a third radius of curvature, wherein each of the second radius of curvature and the third radius of curvature has a length that is different from the length of the first radius of curvature by less than 0.05 millimeters and wherein the origin of the second radius of curvature is not coincident with the origin of the third radius of curvature.

Abstract: Methods and apparatus of the present invention provide for orthopaedic total replacement of the hip while substantially preserving muscles and soft tissues around the hip joint resulting in reduced healing time and decreased risk of dislocation following the procedure. In an exemplary embodiment, the acetabulum is prepared and fitted with a prosthetic acetabular cup 702 and a prosthetic femoral head 1102 is fitted into the prosthetic acetabular cup 702. An intramedullary rod 1502 is inserted longitudinally into the femur. A prosthetic femoral neck 3102 is then inserted from a point along the side of the patient's body and into the side of the femur and through a pre-existing lateral bore in the intramedullary rod 1502 and through the remainder of the femur to join the prosthetic femoral head 1102. The methods and apparatus include structures and techniques for fixing the prosthetic femoral neck 3102 in relation to the intramedullary rod 1502.

Abstract: The invention relates to a joint socket (1) for a hip-joint endoprosthesis (2), wherein the joint socket (1) comprises ageing-resistant materials and forms a low-abrasion sliding pair together with a joint head (3). The joint socket (1) provides an implant surface (4), which is formed from a material with a porous surface, wherein the isoelastic structure of the joint socket (1) according to the invention and the joint head (3) achieves a physiological load transfer by means of specially designed materials, of which the modulus of elasticity is adapted to the values of a spongy bone material.

Abstract: A hip implant assembly including body exhibiting a substantially spherical shaped ball and an elongated stem. An annular defining rim separates the ball from the stem and abuts, in a maximum inserting condition, an exterior surface of a reconditioned femur upon inserting the stem within an interior passageway associated with the femur. A three dimensional and interior volume defining support secures around the ball in a universally articulating permitting fashion, the support being fixed to a reconditioned acetabulum socket associated with an ilium bone by interconnecting posts and anchors established between the fixed support and the reconditioned surface of the acetabulum. A corresponding installation kit assists the preparation of the femur and ilium bones defining the hip joint, as well as the installation of the implant body into the upper conditioned femur end and the outer socket support to a reconditioned acetabulum defined in the ilium bone.

Abstract: The present invention relates to a new composition and medical implant made therefrom, the composition comprising a thick diffusion hardened zone, and preferably further comprising a ceramic layer. The present invention relates to orthopedic implants comprising the new composition, methods of making the new composition, and methods of making orthopedic implants comprising the new composition.

Abstract: A patient-specific acetabular resection guide includes a dome-shaped surface bounded by a periphery. The dome-shaped surface is a three-dimensional patient-specific surface designed to anatomically match and be received into an acetabulum of the patient, based on a three-dimensional image of a hip joint of the patient reconstructed from a medical scan of the hip joint. The resection guide includes a plurality of guiding formations defined on the resection guide and having patient-specific shapes and orientations for guiding corresponding osteotomies relative to the acetabulum for correcting hip dysplasia.

Abstract: A system for replacing a portion of a shoulder joint can include a tray having an outer surface and an inner surface. The outer surface can be adapted to engage a humeral stem. A bearing can include an outer bearing surface and an inner articulating surface. The outer bearing surface can be positioned adjacent to the tray. A ring can be selectively disposed between the tray and the bearing. The ring can define an annular body having a slit formed therein. The ring can be movable between a locked position wherein the ring retains the bearing relative to the tray and an unlocked position. A removal tool can define a proximal end and a distal end. The distal end can define a ring engaging surface and a bearing engaging surface. The ring engaging surface can be adapted to engage the ring at the slit such that the ring expands radially from the locked position away from engagement with the bearing to the unlocked position.

Abstract: A joint replacement prosthesis and procedure reduce the number of steps to complete a joint replacement. The joint replacement prosthesis comprises a ball and socket unit that fixes the ball in the socket prior to surgery. The unit is coupled to a bone structure in the patient and is coupled with a prosthesis that is fixed to another bone of the patient, such as a femoral implant fixed in a femur and providing a coupling at the end of a neck portion that is easily fit into a femoral head and acetabulum unit. A tether may be used to retain the ball in the socket and/or the ball may be retained by extension in the socket that do not restrict patient motion.

Abstract: The present invention relates to methods for making oxidation resistant medical devices that comprise polymeric materials, for example, ultra-high molecular weight polyethylene (UHMWPE). The invention also provides methods of making antioxidant-doped medical implants, for example, doping of medical devices containing cross-linked UHMWPE with vitamin E by diffusion and materials used therein.

Abstract: Hip prosthesis, comprising a first prosthetic body reproducing an acetabular cup and a second prosthetic body reproducing a femoral head and apt to work coupled to the first prosthetic body, wherein the prosthetic bodies have low debris production and different wettability (?) (FIG. 20A).

Abstract: An orthopedic prosthesis comprising a first component having a soft metal bearing surface and a second component having a hard metal bearing surface, in particular a hip prosthesis comprising a spherical bearing member, a femoral stem, and a modular neck configured for interposition between the spherical bearing member and the stem, together with an acetabular implant having a concave bearing surface configured for articulation with the spherical bearing member. One of the spherical bearing member and the concave bearing surface comprises a soft metal bearing surface, the soft metal bearing surface having a hardness of at least about 20 Rc, while the other one of the spherical bearing member and the concave bearing surface comprises a hard metal bearing surface, the hard metal bearing surface having a hardness greater than the soft metal bearing surface by at least about 15 Rc.

Abstract: Methods and apparatus of the present invention provide for orthopaedic total replacement of the hip while substantially preserving muscles and soft tissues around the hip joint resulting in reduced healing time and decreased risk of dislocation following the procedure. In an exemplary embodiment, the acetabulum is prepared and fitted with a prosthetic acetabular cup 702 and a prosthetic femoral head 1102 is fitted into the prosthetic acetabular cup 702. An intramedullary rod 1502 is inserted longitudinally into the femur. A prosthetic femoral neck 3102 is then inserted from a point along the side of the patient's body and into the side of the femur and through a pre-existing lateral bore in the intramedullary rod 1502 and through the remainder of the femur to join the prosthetic femoral head 1102. The methods and apparatus include structures and techniques for fixing the prosthetic femoral neck 3102 in relation to the intramedullary rod 1502.

Abstract: A method and apparatus for performing a minimally invasive total hip arthroplasty. An approximately 3.75-5 centimeter (1.5-2 inch) anterior incision is made in line with the femoral neck. The femoral neck is severed from the femoral shaft and removed through the anterior incision. The acetabulum is prepared for receiving an acetabular cup through the anterior incision, and the acetabular cup is placed into the acetabulum through the anterior incision. A posterior incision of approximately 2-3 centimeters (0.8-1.2 inches) is generally aligned with the axis of the femoral shaft and provides access to the femoral shaft. Preparation of the femoral shaft including the reaming and rasping thereof is performed through the posterior incision, and the femoral stem is inserted through the posterior incision for implantation in the femur.

Abstract: An orthopaedic joint prosthesis which is intended for the replacement of damaged or diseased joints of the human or animal body comprises a first component with a rounded head portion and a second component which comprises a hollow cup for receiving the head portion of the first component. The radius of curvature of one or both of the bearing surfaces changes varies that the bearing surface has a spherical portion at the pole and a space between the bearing surfaces which increases in size towards the lip of the cup.

Abstract: Methods, systems and devices for preventing prosthetic articulating surfaces from separating from each other. A containment system according to one embodiment seeks to prevent an implant stem head from dislocating from a prosthetic component while providing an increased range of motion over conventional constrained components. In one embodiment, an implant structural member includes a cavity and an opening having a lip, including a web along a portion of the lip. An implant stem head has a cooperating surface that corresponds with the web, so that when the cooperating surface of the implant stem head is aligned with the web, the head may be inserted into the implant structural member. The implant stem head is then rotated and the femoral stem component attached, thereby preventing dislocation of the head.

Abstract: Methods, systems and devices for preventing prosthetic articulating surfaces from separating from each other. A containment system according to one embodiment seeks to prevent an implant stem head from dislocating from a prosthetic component while providing an increased range of motion over conventional constrained components. In one embodiment, an implant structural member includes a cavity and an opening having a lip, including a web along a portion of the lip. An implant stem head has a cooperating surface that corresponds with the web, so that when the cooperating surface of the implant stem head is aligned with the web, the head may be inserted into the implant structural member. The implant stem head is then rotated and the femoral stem component attached, thereby preventing dislocation of the head.

Abstract: A hip implant assembly including a spherical shaped ball and an elongated stem. An annular defining rim separates the ball from the stem and abuts, in a maximum inserting condition, over an exterior reconditioned surface of the femur and upon inserting the stem within an interior passageway formed within the femur. A cup shaped support seats the ball in a universally articulating permitting fashion via a flexible and resilient ligament which extends from the ball and is received within a recess passageway of the cup. The cup also includes a mounting surface with a central projecting portion which is in turn resistively fitted within an undercut defined recess formed in the ilium bone in communication with a base surface of the reconditioned acetabulum socket.

Abstract: A ceramic-metal composite articulation is provided with substantial elimination of wear debris, wherein a ceramic material is provided with superior mechanical properties tailored for articulating with ceramic articulations having high flexural strength (greater than about 700 MPa), high fracture toughness (greater than about 7 MPam1/2) and a high Weibull modulus (greater than about 20), in comparison with presently available bio-ceramics such as alumina or zirconia. The mechanical property enhancement enables ceramic materials with greater reliability and significantly reduced in-vivo fracture risk to be obtained. Preliminary in-vitro wear performance, to several million cycles using established test protocols, of head/cup components in a prosthetic hip joint made from these ceramics also demonstrates the ultra low wear characteristics.

Abstract: Methods, systems and devices for preventing prosthetic articulating surfaces from separating from each other. A containment system according to one embodiment seeks to prevent an implant stem head from dislocating from a prosthetic component while providing an increased range of motion over conventional contrained components. In one embodiment, an implant structural member includes a cavity and an opening having a lip, including a web along a portion of the lip. An implant stem head has a cooperating surface that corresponds with the web, so that when the cooperating surface of the implant stem head is aligned with the web, the head may be inserted into the implant structural member. The implant stem head is then rotated and the femoral stem component attached, thereby preventing dislocation of the head.

Abstract: A prosthetic joint assembly that includes a shell including an inner surface. The assembly also includes a bearing member including an outer surface. The bearing member is received by the shell such that the outer surface of the bearing member is adjacent the inner surface of the shell. Furthermore, the joint assembly includes a compressible member that is rigidly fixed to the inner surface of the shell or the outer surface of the bearing member to only cover a portion thereof. The compressible member is made of a material that is different from the shell or the bearing member.

Abstract: An acetabular component for a prosthetic hip joint generally consists of an acetabular shell and an acetabular liner. The acetabular liner includes a cup portion and at least one constraining portion. The cup portion has a hemispherical or dome-shape that defines a hemispherical cavity for receiving a femoral head of a femoral component. The constraining portions may include extensions for retaining the femoral head in the cavity of the cup portion. The liner further includes cutout portions between the constraining portions. The acetabular liner is rotatable within the acetabular shell to provide a complete range of motion to the femoral component without fear of impingement, subluxation, or dislocation of the femoral head. The constraining portions may include inclined surfaces to induce rotation of the acetabular liner within the acetabular shell.

Abstract: A method and apparatus for a prosthesis. At least a portion of the prosthesis is made from a ceramic that is treated with ion implantation, which causes a controllable, bilateral compressive stress of the ceramic. A diamond-like-coating (DLC) can be coated on the ceramic and in the same chamber as the ion implantation. After treating by ion implantation and coating with DLC, the ceramic will be strengthened and have a low coefficient of friction and thereby be made much less likely to fracture under load.

Abstract: At least one embodiment is directed to a system for measuring parameters of a skeletal system in positions of optimal alignment for implantation of an orthopedic device. The system comprises one or more position sensors (202, 204, 206, 208, 210, and 212), one or more measurement sensors (606), a processing unit (506), and a screen (502). The position and measurement sensors are in communication with the processing unit. Position and relational positioning information in conjunction with one or more parameter measurements is used to determine proper seating of an implant, device balance over a range of motion, and device stability. For example, measurement of loading over a range of motion can be used to determine the amount and type of adjustment required for an implant. The positional and measurement data is stored in a database and accessible to the processing unit (506) to aid the surgeon, hospital, and implant manufacturer.

Abstract: An improved hip prosthesis includes an acetabular cup bearing component constructed from a relatively hard and high strength ceramic material for articulation with a ball-shaped femoral head component which may be constructed from a compatible ceramic or metal material. In one form, the acetabular cup further includes a ceramic porous bone ingrowth surface adhered thereto for secure ingrowth attachment to natural patient bone.

Abstract: An implantable articulating bone prosthesis (e.g., hip or joint prosthesis) is provided, which includes a pair of articulation components respectively defining a pair of articulation surfaces movably engageable with each other. Each of the articulation surfaces is formed from a biocompatible ceramic (e.g., doped silicon nitride ceramic) having a flexural strength greater than about 700 Mega-Pascal (MPa) and a toughness greater than about 7 Mega-Pascal root meter (MPam0.5).

Abstract: A composition, a medical implant constructed from the composition, and a method of making the composition are described. The composition is a composite material, comprising a porous, reticulated, open cell network having at least part of its surface coated with blue-black or black oxidized zirconium.

Abstract: A modular hip joint implant and associated method. The modular hip implant includes a femoral stem having a proximal surface defining a dovetail groove having first and second female wings, and a neck component having a distal surface defining a semi-dovetail projection engaging the dovetail groove. The projection includes a single male wing mating with the first femoral wing.

Abstract: Femoral head modular resurfacing systems are described. The systems primarily include a head component and a stem component. The configuration of the head component and stem components allow for minimum invasiveness into the femur head region, thus conserving greater amounts of bone tissue than would be possible with conventional hip replacement systems. The systems also provide for various angles and offsets to be achieved between the systems and the femur head. The systems are useful in partial hip replacement procedures, as well as total hip replacement procedures, in which case an optional acetabular component would also be employed.

Abstract: A prosthetic constraining device for use with a hip replacement prosthesis that includes an acetabular cup assembly adapted to be bonded to a patient's pelvis and a femoral stem adapted to be bonded to the patient's femur, where the femoral stem includes a ball component at its proximal end received within the acetabular cup assembly to form a ball joint type coupling, and where the constraining device includes a ring having a central aperture, where the ring is adapted to be mounted to a rim of the acetabular cup assembly so that the femoral stem passes through the central aperture, where the diameter of the central aperture is less than the diameter of the ball component on the proximal end of the femoral stem so that the ring assists in maintaining the ball joint type coupling between the acetabular cup assembly and the femoral stem, and where the ring comprises a biologic material, a biologically reabsorbable material and a combination of biologic, or biologically reabsorbable materials.

Abstract: Methods and apparatus using a surgical navigation system during hip joint replacement surgery without separately affixing a marker to the femur. The navigation system acquires the center of rotation of the hip joint as well as at least one point on the femur in the pelvic frame of reference. From these two points, the navigation system calculates the position and length of a first line between the center of rotation of the hip joint and the point on the femur. A prosthetic cup is implanted and its center of rotation is recorded. A tool for forming the bore within which the stem of the femoral implant component will be placed is tracked by the navigation system. The navigation system calculates the position and length of a first line between the center of rotation of the prosthetic cup and the re-palpated first point. The surgical navigation system uses this information to calculate and display to the surgeon relevant information about the surgery.

Abstract: The invention relates to an implant for relieving damaged areas of the surfaces of hip or shoulder joints from stress. Said implant can be introduced into the space between the joint surfaces of the condyle (11) and the socket (13) cooperating in the natural joint. The inventive implant is cup-shaped or cap-shaped, rests in the socket (13) by means of a convex external face, and sits on the condyle (11) by means of a concave internal face in the implanted state. The implant comprises at least two articulation layers (15, 17) which are movable relative to each other and encompass articulation surfaces that face one another in the implanted state.

Abstract: An assembly, for example for a reconstructive joint of the human body, comprises first and second parts which bear against one another. The first and second parts may both comprise a first polymeric material which is preferably polyetheretherketone in combination with carbon fibre.

Abstract: Systems and methods for determining placement of prosthetic components in joint including defining patient-specific frame of reference for joint, determining patient-specific postoperative range of motion of joint, evaluating patient-specific range of motion of joint, automatically planning placement of components balancing need for range of motion with prosthesis stability through bony coverage, and applying manual adjustments to the automatically planned placement of component by giving greater or lesser weight to need for range of motion or prosthesis stability through bony coverage. Apparatuses for defining center of prosthetic femoral head and axis of prosthetic femoral neck including primary cylinder, first alignment receptacle and second alignment receptacle, and a divot on exterior of primary cylinder, divot having normal parallel to longitudinal axis of second alignment receptacle and position of the divot being translated toward an opening of the first alignment receptacle on the primary cylinder.

Abstract: The present invention relates to a new composition and medical implant made therefrom, the composition comprising a thick diffusion hardened zone, and preferably further comprising a ceramic layer. The present invention relates to orthopedic implants comprising the new composition, methods of making the new composition, and methods of making orthopedic implants comprising the new composition.

Abstract: A replacement joint for a human body and a method of installing such a replacement joint is provided. A ball portion of the replacement joint is installed on an end of a first bone. A receptacle having an engagement surface that has an aspherical configuration is formed in a second bone. A socket portion of the replacement joint is inserted in the receptacle so as to receive the ball portion on the first bone. The socket portion has an engagement surface with an aspherical configuration complementary to the engagement surface of the receptacle in the second bone. The configurations of the engagement surfaces of the socket portion and the receptacle in the second bone are such that inserting the socket portion in the receptacle in the second bone provides the socket portion with at least four degrees of constraint.

Abstract: A prosthetic hip joint replacement system has a femoral component with a tapered trunion thereon. A modular head with a part-spherical outer surface terminating in a planar surface, engages the trunion. An acetabular cup member is provided for receiving the part-spherical head of a femoral implant, the cup member has a cavity having a part-spherical inner surface for receiving the modular head. The part-spherical inner surface of the cup defines a polar axis and an equator centered about a pole of the cavity. The cavity has a part-circular opening spaced from the pole a greater distance than the equator. Thus the inner part-spherical bearing surface extends beyond the 180° which the equator extends. The configuration of the part-spherical inner bearing surface causes a movement of translation of the head during rotation so that there is a crescent shaped retention area on each opposed side thereof.

Abstract: Provided is a novel hip replacement implant system that includes a ball assembly having a ball trunion, the ball assembly being configured as a replacement for the head of the femur and capable of being secured by the ball assembly trunion to a calcar implant element that can be securely seated in the calcar bone of the femoral neck, thus maintaining the load transfer function of the calcar bone of the femoral neck. A method of using the device is also provided.

Abstract: A hip prosthesis has a cup element having a part-spherical inner bearing surface and a spherical center through which the plane of a diametrical equator extends, and a ball shaped head which has a diameter to cooperate with the inner bearing surface to allow movement therein. The cup has a flat cordal lower surface parallel to the plane of an equator of the ball. The inner bearing surface has two or more equally spaced extension portions which extend beyond the diametrical equator towards the mouth of the cup. The surfaces of the two or more portions are relieved to enable the ball shaped head to be inserted into the cup by moving the flat on the ball across the face of one of the bearing surface extension portions and then rotating ball head to a position in which the flat on the ball head faces the mouth of the cup.

Abstract: A hip resurfacing femoral prosthesis has a sleeve component with an internal bore adapted to receive a femoral head and a partially conical outer surface. The sleeve is for use with a mating partial ball component shaped to conform to an acetabular socket. The sleeve is slotted or segmented to enhance the engagement with the femoral head. The partial ball component may be translated proximally and distally to reposition the outer surface by selecting sleeves with varying geometries.

Abstract: Medical prosthetic devices and in particular femoral head and/or acetabular cup of articular prostheses, made out of a cobalt alloy are submitted to a surface modification in order to obtain the formation of a thin surface layer constituted by Co—Ta and or Co—Nb intermetallic compounds, with the aim of inducing to the prosthetic device enhanced characteristics of biocompatibility, low metal ion release, higher hardness and wear resistance. The process of surface modification is performed by a treatment of the alloy in a molten salt mixture containing a tantalum halide, without applying any electrical field.

Abstract: A prosthesis member or assembly can be implanted in a portion of the anatomy. The prosthesis member, with various portions, defines a selected amount of a sphere to articulate or engage selected portions of the anatomy.

Abstract: Prosthetic hips are well known in the arts and have been successfully used for many years. There are, however, some inherent health problems associated with present art designs. All of the prosthetic hip designs utilize a variety of materials. Most used are plastic, ceramic and metal materials. One of the main problems associated with prior art prosthetic hips involves friction generated between cup and ball. Friction dislodges, from cup and ball surfaces, plastic, ceramic or metallic fragments during a patient's normal motor functions. These particles interact with the body's chemistry and may cause deleterious health side effects. Rubbing action between cup and ball also produces ions which can adversely affect the patient's health. It is therefore essential that friction between prosthetic hip cup and ball is reduced to a minimum. The design of the prosthetic hip presented herewith will alleviate some of the unwanted friction between cup and ball.

Abstract: A prosthetic joint in which at least one bearing component is made from solid diamond.

Abstract: A hip cup extraction apparatus (101) comprising a shaft (402), a handle (404), a semicircular cutting blade (406), a spring loaded latching member (408), and a head (100) for removing a hip cup (405) from a pelvic bone (401). The head (100) includes a semispherical section (102) terminating in a substantially planar surface (104), a hip cup extraction apparatus aperture (106), a retaining sleeve (108), and a three sided void (110). The head (100) may be configured for selective attachment to the hip cup extraction apparatus (101). The hip cup extraction apparatus (101) is inserted into the hip cup extraction apparatus aperture (106), and an optional spring loaded latching member (408) retains the head (100) in place. As the head (100) is being attached to the hip cup extraction apparatus (101), the semicircular cutting blade (406) may pass through the three sided void (110). Once the head (100) is attached to the hip cup extraction apparatus (101), the head (100) is inserted into the hip cup (405).

Abstract: A prosthetic joint in which at least one bearing component is made from solid diamond.

Abstract: A joint prosthesis device comprises a head configured to fit within a cup. The cup includes a concave cup surface defined by at least one radius of curvature RC. The head includes a convex head surface defined by at least one radius of curvature RH. The convex head surface is configured to engage the concave cup surface. The convex head surface provides an articulation zone where the head surface engages the cup surface. RC differs from RH in the articulation zone by a first amount. The convex head surface also provide a peripheral zone outside of the articulation zone. RC differs from RH in the peripheral zone by a second amount that is greater than the first amount. The peripheral zone generally extends over an area subtended by a minimum angle having a vertex at a center of the head.

Abstract: The present invention discloses methods for enhancing the wear-resistance of polymers, the resulting polymers, and in vivo implants made from such polymers. One aspect of this invention presents a method whereby a polymer is irradiated, preferably with gamma radiation, then thermally treated, such as by remelting of annealing. The resulting polymeric composition preferably has its most oxidized surface layer removed. Another aspect of the invention presents a general method for optimizing the wear resistance and desirable physical and/or chemical properties of a polymer by crosslinking and thermally treating it. The resulting polymeric compositions is wear-resistant and may be fabricated into an in vivo implant.

Abstract: Methods, systems and devices for preventing prosthetic articulating surfaces from separating from each other. A containment system according to one embodiment seeks to prevent an implant stem head from dislocating from a prosthetic component while providing an increased range of motion over conventional contrained components. In one embodiment, an implant structural member includes a cavity and an opening having a lip, including a web along a portion of the lip. An implant stem head has a cooperating surface that corresponds with the web, so that when the cooperating surface of the implant stem head is aligned with the web, the head may be inserted into the implant structural member. The implant stem head is then rotated and the femoral stem component attached, thereby preventing dislocation of the head.