Femoral insert

Claim 2

A femoral insert for a hip joint prothesis for use in a femur that has been cut across the femoral neck to form a cut surface, the insert comprising: a stem having a proximal end attachable to a generally spherical head member, a distal end and a bend located therebetween, the stem having a longitudinal axis below the bend, a load transferring means for transferring axial loads from said stem to said femur at said cut surface, and a guide means for locating said stem within said femur, said guide means and said stem cooperating to permit axial movement along said longitudinal axis, but to restrict any other movement of said stem within said guide means, said guide means being securable to said femur below said cut surface.

Claim 3

The insert of claim 1 wherein said load transferring means comprises a collar securable to said stem, said collar contacting said femur at an outer cortical bone section, when said insert is in position, said collar transferring axial loads from said stem to said cortical bone section.

Claim 4

The insert of claim 2 wherein said collar has an undersurface for seating against said cut surface of said femoral neck, said undersurface being conducive to bone ingrowth.

Claim 5

The insert of claim 1 wherein said guide means cooperates with said stem to restrict rotational movement of said stem about said axis, and further restricts movement of said stem in any direction generally perpendicular to said axis.

Claim 6

The insert of claim 1 wherein said guide means is a sleeve, having a central bore for receiving said stem therein.

Claim 7

The insert of claim 5 wherein said stem is of generally uniform cross-section for that portion of the stem cooperating with the sleeve.

Claim 8

The insert of claim 5 wherein said sleeve has an outer surface conducive to bone ingrowth.

Claim 9

The insert of claim 5 wherein said sleeve is generally tapered in outer contour and may be force fit into said femur.

Claim 10

The insert of claim 5 wherein said central bore has a tapered shoulder for accommodation of a portion of said bend of said stem when said stem moves axially.

Claim 11

The insert of claim 1 wherein said stem has a non-circular cross section below said bend, and said guide means comprises a sleeve having a corresponding, but slightly larger central bore which is non-circular in cross-section, said guide means allowing said stem to move axially, but restraining said stem for rotating about said longitudinal axis or moving in a direction generally perpendicular to said axis.

Claim 12

The insert of claim 9 wherein said stem has a pair of opposed grooves running parallel to said longitudinal axis below said, bend, and said sleeve has a pair of opposed ridges mating with said grooves.

Claim 13

The invention of claim 1 wherein said stem at said distal end, tapers to a rounded tip.

Claim 14

The invention of claim 12 wherein said stem tapers slightly near to said distal end by means of a narrowing step change in radius.

Claim 15

The invention of claim 1 wherein said stem includes a compressible non-metallic tip attached to said distal end.

Claim 16

The invention of claim 14 wherein said tip comprises a lattice of ultra high molecular weight polyethylene.

Claim 17

A femoral insert for a hip joint prothesis for use in a femur that has been cut across the femoral neck below its head to form a cut surface, the insert comprising: a stem having a proximal end attachable to a generally spherical head member, a generally rounded distal end and a bend located therebetween generally closer to said proximal end than said distal end, said stem having a longitudinal axis below said bend, a load transferring collar securable to said stem, said collar being of sufficient size to seat upon a cortical bone section of said femur when said insert is in position, said collar transferring axial loads from said stem to said cortical bone section, and a tapered sleeve securable within said femur below said cut line when said insert is in position, said sleeve allowing axial movement of said stem along said longitudinal axis, thereby allowing seating of said collar onto said cortical bone section, said sleeve restraining rotational movement of said stem about said longitudinal axis, thereby maintaining said proximal end, when said insert is in position, in position.

Claim 18

A femoral insert for a hip joint prothesis for use in a femur that has been cut across the femoral neck below its head to form a cut surface, the insert comprising: a stem having a proximal end attachable to a generally spherical head member, a generally rounded distal end and a bend located therebetween generally closer to said proximal end than said distal end, said stem having a longitudinal axis below said bend, a load transferring collar securable to said stem, said collar being of sufficient size to seat upon a cortical bone section of said femur when said insert is in position, said collar transferring axial loads from said stem to said cortical bone section, and a tapered sleeve securable within said femur below said cut line when said insert is in position, said sleeve allowing axial movement of said stem along said longitudinal axis, thereby allowing seating of said collar onto said cortical bone section, said sleeve restraining rotational movement of said stem about said longitudinal axis, thereby maintaining said proximal end, when said insert is in position, in position.

Claim 21

A method as in claim 17, wherein the step of securing the guide means within the femur includes cementing said guide means in place with bone cement.

Claim 22

A method as is claimed in claim 17, wherein the step of securing the guide means within the femur includes driving said guide means into said femur to form an interference fit.

Claim 23

A method as is claimed in claim 17, wherein the step of securing the guide means in place within the femur includes the step of providing a surface on said guide means conducive to bone ingrowth.

Claim 24

The method of claim 17, wherein said step of seating said collar on said cut surface further includes providing an undersurface on said collar conducive to bone ingrowth.

Claim 25

The method of claim 17 wherein said step of allowing said stem to move axially within said channel includes providing an open space below a distal end thereof.

Claim 26

The method of claim 17 wherein said step of allowing said stem to move axially within a said channel includes providing a non-metallic compressible tip at a distal end of said stem.