Abstract: Position reference members are provided as part of an orthopaedic implant system. Both position reference members can be implanted on or in the same bone as the other parts of the implant. One of the position reference members is fixed to the bone and the other position reference member is movable with another part of the implant, such as a stem received in the intramedullary canal. The movable position reference member can move with respect to the fixed position reference member. At least one of the position reference members includes indicia such as a main scale or a vernier scale. Parts of the indicia and position reference members are radio-opaque and parts are radiolucent. Post-operative changes in the relative positions of the position reference members can be measured by radiography or fluoroscopy so that changes in the implant position can be monitored over time.

Abstract: A prosthetic orthopaedic head has a fluid chamber defined therein. A fluid filter is positioned in the fluid chamber. In response to a load being exerted on the prosthetic head, synovial fluid is advanced through a filter thereby removing debris from the synovial fluid. A method of operating a prosthesis is also disclosed.

Abstract: A joint prosthesis (10) for cooperation with a long bone (12) and a second bone (26) for use in arthroplasty is provided. A cavity (20) is formed in the long bone (12) and defined by an inner wall (30) of the long bone (12). The prosthesis (10) includes a stem component (32) including a distal portion (34) of the stem component (32) for placement at least partially within the cavity (20) of the long bone (12) and for securing to the long bone (12). The stem component (32) defines a longitudinal axis (36) of the stem component (32). The prosthesis (10) also includes a second component (32) securable to the second bone (26) and for cooperation with the stem component (32). The prosthesis (10) further includes a bearing (40) for placement in the cavity (20) between the stem component (32) and the long bone (12) so that the distal portion of the stem component (32) is spaced from the inner wall (30) of the long bone (12).

Abstract: A prosthetic orthopaedic head has a fluid chamber defined therein. A fluid filter is positioned in the fluid chamber. In response to a load being exerted on the prosthetic head, synovial fluid is advanced through a filter thereby removing debris from the synovial fluid. A method of operating a prosthesis is also disclosed.

Abstract: A joint prosthesis (10) for cooperation with a long bone (12) and a second bone (26) for use in arthroplasty is provided. A cavity (20) is formed in the long bone (12) and defined by an inner wall (30) of the long bone (12). The prosthesis (10) includes a stem component (32) including a distal portion (34) of the stem component (32) for placement at least partially within the cavity (20) of the long bone (12) and for securing to the long bone (12). The stem component (32) defines a longitudinal axis (36) of the stem component (32). The prosthesis (10) also includes a second component (32) securable to the second bone (26) and for cooperation with the stem component (32). The prosthesis (10) further includes a bearing (40) for placement in the cavity (20) between the stem component (32) and the long bone (12) so that the distal portion of the stem component (32) is spaced from the inner wall (30) of the long bone (12).

Abstract: An implantable pressure measurement device is effective to measure a physiological pressure, which pressure can be ascertained by external imaging of the device. In one embodiment, a predetermined amount of a fluid is sealed in a flexible member which is disposed in a housing. A position indicating member is coupled to one end of the flexible member. The fluid expands and contracts the flexible member in response to external pressure changes. A physiological pressure is determined by ascertaining the relative location of the position indicating member on the housing. An external imaging system is used to view scale markings located on the position indicating member and the housing. In another embodiment, an elongate member is axially movable within a housing. A sealing member seals an amount of air in a portion of the housing and is sealably engaged with one end of the elongate member. A physiological pressure is determined using an imaging system to determine the position of the elongate member.