Zimmer Gmbh

Jonathan Blamey

John N Insall

Peter Stanley Walker

Michael Wadcock

Mark Alan Heldreth

Steven A Zawadzki

Shawn Elliott McGinley

The present invention provides an improved method and apparatus for preparing a femur to receive a modular prosthetic femoral component. A distal reamer having a plurality of sets of depth marks is utilized to prepare the distal femoral canal. The sets of depth marks on the distal reamer correspond in number to the number of distal femoral stems available for use with the particular modular prosthetic femoral implant set. Each set of depth marks comprises a plurality of indicator rings corresponding in number to the number of proximal bodies adapted for utilization with the prosthetic femoral component set. Prior to distal reaming, the appropriate set of depth marks and indicator ring is chosen corresponding to the modular components the surgeon wishes to utilize. Reaming then takes place until the chosen indicator ring is aligned with a reference point (e.g., the top of the greater trochanter). Upon reaching the appropriate reaming depth, the distal reamer is left in place in the femoral canal. A cannulated forming tool, e.g. a rasp or reamer, is thereafter positioned over the shank of the distal reamer and utilized to effect proximal canal sizing. The distal reamer head is sized whereby the proximal reamer, e.g., will abut the reaming head of the distal reamer when the proximal reamer reaches the appropriate depth associated with the shortest distal stem of the modular femoral component set. In this way, the head of the distal reamer provides a mechanical stop for the proximal reamer so that both under reaming and over reaming are avoided. In cases in which a longer femoral stem is utilized, a cylindrical spacer having a length corresponding to the length difference between the shortest distal stem and the chosen distal stem is utilized to provide a mechanical stop for the proximal reamer. The reamer spacer includes an elongate aperture sized whereby the reamer spacer fits about the shank of the distal reamer.

Method and apparatus for preparing a femur to receive a modular prosthetic femoral component

The prosthesis comprises a femoral component (2) having at least one substantially spheroidal condylar bearing surface (10,11), a tibial component (6) including a tibial platform (20), and a plastics meniscal component (7) located between the condylar bearing surface (10,11) an the tibial component (6) and being slidable on the platform (20). The meniscal component (7) is retained on a guide (23) upstanding from the platform (20). The guide (23) includes a post (24) and a cap (25) which is a snap-fit in a recess (30) in the meniscal component (7). The guide (23) is slidable in a track (32) within the meniscal component (7) so that movement of the meniscal component (7) in the anterior/posterior direction (A-P) is limited by impingement of the meniscal component (7) on the post (24) and/or on a rail member (21) projecting from the surface of the tibial platform (20). To install the prosthesis, a femur (1) is resected to provide a base for receiving the femoral component (2), which is retained in the resected femur by pins (3). The tibia (4) is resected to provide a flat base into which the tibial component (6) is fixed by a stem (5).

Prosthesis for knee replacement

The invention provides means for evaluating the fit of a knee replacement prosthesis on a resected tibial surface. A provisional instrument for this purpose includes a positioning tray having a peripheral profile corresponding to that of the tibial platform of the prosthesis, the tray having an upper surface and an under surface which is substantially flat and free from projections and the tray having a plurality of holes for receiving pins for temporarily attaching the positioning tray in a desired position on the resected tibial surface. Also disclosed is a jig for guiding, drilling and broaching operations, the jig having an aperture which is shaped to guide the broach. In addition, the invention includes a tibial broach which includes a hollow body having an upper end and a lower end and having an anvil at its upper end, an interior face and a posterior face which slopes downwardly towards a lower end, the posterior face having a series of teeth which are formed in the hollow body, such that bone cut by the teeth as the broach is driven into an intramedullary canal of a tibia passes into the hollow body.

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Wiltshire, United Kingdom

Jonathan Blamey