Abstract: A knee joint prosthesis which comprises a tibial component (4, 6) and a femoral component (2). The femoral component has condyles (14, 16) which act against the tibial component, directly or indirectly, during flexing of the knee. A cam (20) on the femoral component acts against a post (26) on the tibial component at high flex angles. The surface of the post which is contacted by the cam at high flex angles is convex when the post viewed generally perpendicular to the tibial bone contact and bearing surfaces, and the femoral bearing surface which is provided by the cam, where it contacts the convex surface of the post at high flex angles, is locally concave (32) when viewed along the surface of the post which contacts the cam so that the area of contact between the post and the cam is greater at high flex angles than at lower flex angles.

Abstract: A knee joint prosthesis which comprises a tibial component (4, 6) and a femoral component (2). The femoral component has condyles (14, 16) which act against the tibial component, directly or indirectly, during flexing of the knee. A cam (20) on the femoral component acts against a post (26) on the tibial component at high flex angles. The surface of the post which is contacted by the cam at high flex angles is convex when the post viewed generally perpendicular to the tibial bone contact and bearing surfaces, and the femoral bearing surface which is provided by the cam, where it contacts the convex surface of the post at high flex angles, is locally concave (32) when viewed along the surface of the post which contacts the cam so that the area of contact between the post and the cam is greater at high flex angles than at lower flex angles.

Abstract: A knee joint prosthesis which comprises a tibial component (4, 6) and a femoral component (2). The femoral component has condyles (14, 16) which act against the tibial component, directly or indirectly, during flexing of the knee. A cam (20) on the femoral component acts against a post (26) on the tibial component at high flex angles. The surface of the post which is contacted by the cam at high flex angles is convex when the post viewed generally perpendicular to the tibial bone contact and bearing surfaces, and the femoral bearing surface which is provided by the cam, where it contacts the convex surface of the post at high flex angles, is locally concave (32) when viewed along the surface of the post which contacts the cam so that the area of contact between the post and the cam is greater at high flex angles than at lower flex angles.

Abstract: A knee joint prosthesis which comprises a tibial component (4, 6) and a femoral component (2). The femoral component has condyles (14, 16) which act against the tibial component, directly or indirectly, during flexing of the knee. A cam (20) on the femoral component acts against a post (26) on the tibial component at high flex angles. The surface of the post which is contacted by the cam at high flex angles is convex when the post viewed generally perpendicular to the tibial bone contact and bearing surfaces, and the femoral bearing surface which is provided by the cam, where it contacts the convex surface of the post at high flex angles, is locally concave (32) when viewed along the surface of the post which contacts the cam so that the area of contact between the post and the cam is greater at high flex angles than at lower flex angles.

Abstract: A guide block for use in surgery to locate a surgical tool accurately relative to an anatomical feature comprises a fixation part which can be fastened directly to the patient's tissue, and a guide part having at least one structural feature to engage a surgical tool to ensure that the tool is located appropriately relative to the patient's tissue. The guide part is mounted on the fixation part. The guide block includes at least two drives for adjusting the position of the guide part relative to the fixation part, so that the position of the guide part relative to the fixation part can be adjusted in at least two degrees of freedom. The fixation part of the guide block includes a housing which is hollow, and the drives are located inside the housing.

Abstract: A knee joint prosthesis which comprises a tibial component (4, 6) and a femoral component (2). The femoral component has condyles (14, 16) which act against the tibial component, directly or indirectly, during flexing of the knee. A cam (20) on the femoral component acts against a post (26) on the tibial component at high flex angles. The surface of the post which is contacted by the cam at high flex angles is convex when the post viewed generally perpendicular to the tibial bone contact and bearing surfaces, and the femoral bearing surface which is provided by the cam, where it contacts the convex surface of the post at high flex angles, is locally concave (32) when viewed along the surface of the post which contacts the cam so that the area of contact between the post and the cam is greater at high flex angles than at lower flex angles.

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: A knee joint prosthesis which comprises a tibial component (4, 6) and a femoral component (2). The femoral component has condyles (14, 16) which act against the tibial component, directly or indirectly, during flexing of the knee. A cam (20) on the femoral component acts against a post (26) on the tibial component at high flex angles. The surface of the post which is contacted by the cam at high flex angles is convex when the post viewed generally perpendicular to the tibial bone contact and bearing surfaces, and the femoral bearing surface which is provided by the cam, where it contacts the convex surface of the post at high flex angles, is locally concave (32) when viewed along the surface of the post which contacts the cam so that the area of contact between the post and the cam is greater at high flex angles than at lower flex angles.

Abstract: A method of making a component (2) of an orthopaedic joint prosthesis, which has a bearing surface whose shape corresponds approximately to a part of a sphere and is symmetrical about its polar axis, involves use of a cutting tool (6) which has a circular cutting edge (12) and which can be rotated about an axis (8) which is perpendicular to the plane containing the said cutting edge (12). The method involves (a) rotating the component about its polar axis (4) and rotating the cutting tool (6) about its axis (8), with the cutting edge (12) of the cutting tool (6) in contact with the surface of the component (2); (b) moving the cutting tool (i) in a direction parallel to the polar axis (4) of the component (2) while leaving the angle between the axis of the cutting tool (6) and the polar axis of the component (2) unchanged, and (ii) along its axis (8); and (c) repeating step (a).

Abstract: A guide block for use in surgery to locate a surgical tool accurately relative to an anatomical feature comprises a fixation part which can be fastened directly to the patient's tissue, and a guide part having at least one structural feature to engage a surgical tool to ensure that the tool is located appropriately relative to the patient's tissue. The guide part is mounted on the fixation part. The guide block includes at least two drives for adjusting the position of the guide part relative to the fixation part, so that the position of the guide part relative to the fixation part can be adjusted in at least two degrees of freedom. The fixation part of the guide block includes a housing which is hollow, and the drives are located inside the housing.

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 (2) with a rounded head portion (103) and a second component which comprises a hollow cup (1) for receiving the head portion (103) of the first component. The radius of curvature of one or both of the bearing surfaces (3, 4) changes varies that the bearing surface has a spherical portion (100) at the pole and a space (109) between the bearing surfaces (3, 4) which increases in size towards the lip of the cup (1).

Abstract: A method of making a component (2) of an orthopaedic joint prosthesis, which has a bearing surface whose shape corresponds approximately to a part of a sphere and is symmetrical about its polar axis, involves use of a cutting tool (6) which has a circular cutting edge (12) and which can be rotated about an axis (8) which is perpendicular to the plane containing the said cutting edge (12). The method involves (a) rotating the component about its polar axis (4) and rotating the cutting tool (6) about its axis (8), with the cutting edge (12) of the cutting tool (6) in contact with the surface of the component (2); (b) moving the cutting tool (i) in a direction parallel to the polar axis (4) of the component (2) while leaving the angle between the axis of the cutting tool (6) and the polar axis of the component (2) unchanged, and (ii) along its axis (8); and (c) repeating step (a).

Abstract: An orthopaedic joint prosthesis comprises first and second articulating components having respective bearing surfaces in contact with one another. The material of the first bearing surface (14) comprises a metallic material and the material of the second bearing surface (6) comprises a ceramic material. The hardness of the metallic material is at least about 2500 MPa, and the hardness of the ceramic material is greater than that of the metallic material by at least about 4000 MPa.

Abstract: An extraction device (10,110) for removing a socket bearing insert (12) from an acetabular cup (14) in an acetabular prosthesis in which an extracting member (30, 130) is adapted for attachment to a groove (20) in the insert (12). The extraction device (10, 110) includes a support in the form of a sleeve (38, 138) which bears against the rim of the acetabular cup (14). The extraction device (10, 110) has means for providing an axial force exclusively between the extracting member (30, 130) and the support such that no force is transmitted to a bone to which the acetabular cup (14) is attached.

Abstract: An extraction device (10,110) for removing a socket bearing insert (12) from an acetabular cup (14) in an acetabular prosthesis in which an extracting member (30, 130) is adapted for attachment to a groove (20) in the insert (12). The extraction device (10, 110) includes a support in the form of a sleeve (38, 138) which bears against the rim of the acetabular cup (14). The extraction device (10, 110) has means for providing an axial force exclusively between the extracting member (30, 130) and the support such that no force is transmitted to a bone to which the acetabular cup (14) is attached.

Abstract: A joint prosthesis having two mutually articulating components that are made of a metal alloy. One of the components is made of an alloy having a low carbon content (0.03 to 0.10 wt. %) and the other component is made of an alloy having a high carbon content (0.18 to 0.35 wt. %). The articulating components may be, for example, a hip head prosthesis and an acetabular cup prosthesis.