CA1258152A - Joint prosthesis - Google Patents
Joint prosthesisInfo
- Publication number
- CA1258152A CA1258152A CA000508986A CA508986A CA1258152A CA 1258152 A CA1258152 A CA 1258152A CA 000508986 A CA000508986 A CA 000508986A CA 508986 A CA508986 A CA 508986A CA 1258152 A CA1258152 A CA 1258152A
- Authority
- CA
- Canada
- Prior art keywords
- tray
- insert
- tab
- prosthesis
- wall
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
JOINT PROSTHESIS
ABSTRACT
An implantable joint prosthesis comprising a metal tray and rigid plastic insert removably fitted into the tray.
The tray has an upper surface and a lower surface. The lower surface has at least one stem for insertion into a human bone.
The upper surface of the metal tray has a generally flat continuous central region and an upwardly extending wall enclosing the major portion of the central region. Recesses are provided adjacent the base of the wall on opposite sides of the tray. The rigid plastic insert has a generally flat continuous lower surface and a first and second tab at the lower edge of the insert at a location which corresponds to the recesses in the tray. A narrow slot is provided in the lower surface of the insert and spaced immediately behind at least the first tab to allow the first tab to deflect when the insert is forced into the tray.
ABSTRACT
An implantable joint prosthesis comprising a metal tray and rigid plastic insert removably fitted into the tray.
The tray has an upper surface and a lower surface. The lower surface has at least one stem for insertion into a human bone.
The upper surface of the metal tray has a generally flat continuous central region and an upwardly extending wall enclosing the major portion of the central region. Recesses are provided adjacent the base of the wall on opposite sides of the tray. The rigid plastic insert has a generally flat continuous lower surface and a first and second tab at the lower edge of the insert at a location which corresponds to the recesses in the tray. A narrow slot is provided in the lower surface of the insert and spaced immediately behind at least the first tab to allow the first tab to deflect when the insert is forced into the tray.
Description
8~5~
Background of the Invention Field of the Invention The present invention relates, in general, to prosthetic devices such as artificial joints, particularly artifi-cial knee joints, and, more particularly, to suchdevices in which the plastic portion of the device can be replaced.
Prior Art Artificial implantable prostheses to replace human joints have been available for some time. These prostheses generally consist of a metallic portion which interfaces with a plastic member. For example, in a knee joint, the natural knee joint includes the end of a femur which has two knob-like processes, the medial condyle and the lateral condyle, which are smooth and rest on the medial condyle and lateral condyle of the tibia. The condyles of the tibia are very smooth and slightly cupped to pro-vide a surface on which the femur condyles can articulate.
In the event that a knee joint is replaced, the femur and/or the tibial portions of the joint are replaced.
The femoxal component is usually a metal implant which is anchored in the femur. The tibial component comprises an ultra-high molecular weight polye-thylene member which may be anchored in a metal tray. The polyethylene member provides the smooth-cupped surfaces on which the femoral component rests during norma~ motion. One of the draw-backs in such joint replacement procedures is the~ Eact tha-t the plastic components may slowly deform because of cold flow or may wear. The deformation or wear may require the eventual replacemen-t of at least the plas-tic portion of the tibial knee prosthesis.
The knee prosthesis must also be properly sized and fitted to the patient by the orthopaedic surgeon when the implant procedure is undertaken. Because of the great variety of different configurations of the human knee, there must be an extensive variety of different sized knee prostheses available to -the surgeon during the surgical procedure so that the proper prosthesis may be selec-ted for implantation. One of the vari-abilities in the prosthesis is the height of the tibial component of the joint. Prior patents have suggested that the tibial portion of the joint be composed of a metal tray and a replaceable polyethylene insert, so that the metal tray could be implanted into the tibia, and the surgeon would have available plastic components of different heights to properly size the prosthesis during the surgical procedure. In order to provide this flexibilityl it is necessary to have some system of securing the plastic component of the tibia prosthesis into the metal tray. U.S. Patent 4,257,129 discloses such a system with a metal tray and a removable poly-ethylene insert in the tray. The polyethylene insert is secured to the tray using a dovetail joint in the tray with a matching dovetail joint in the polyethylene insert. In addition, there are two pins to secure the insert into the tray. A first pin extends through the polyethylene insert and into the tray in the vertical direction, and a second pin extends in the horizontal direction to secure the first pin in position. To re-move the plastic insert, the pins are removed and the polyethylene insert can be removed by sliding the poly-ethylene insert outof the dove-tail grooves of the metal tray.
U.S. Patent 4,207,627 discloses a knee prosthesis with a metal tray and two plastic inserts. The plastic inserts ~5&~
hav~ a lip on one side which fits in a r~cess in the metal tray to r~tain th~ ins~rt in th~ tray.
Summary of -th~ Inv~ntion The present inv~ntion provides an improved prosthesis in which the plastic insert can b~ readily fitted into the m~tal tray. The prosthesis provides an improved locking system to more positivcly secure the plastic insert into the tray wi-~h-out using pins or similar locking components. In thc pr~s~nt device, th~ plastic insert is snap fitted into thc metal tray on two opposed sidcs of the ins~rt and, although sccur~ly affix~d in the tray~ th~ ins~rt may readily be removed if necessary.
According to a further broad aspect of th~ present invention th~r~ is provided an implantabl~ joint prosthesis comprising a metal tray and rigid plastic inscrt removably fitt~d into the tray. The tray has an upper surface and a lower surfacc.
The lower surfac~ has at least one stem for insertion in-to a human bonc. The upp~r surfac~ of -the m~tal tray has a g~nerally flat continuous central region and an upwardly ~xtending wall enclosing the major portion of thc central region. Rec~ss~s ar~ provided adjacent the base of the wall on opposit~ sides of the tray. Th~ rig:id pl ast..i.c i.ns~.rl: has a g~nerally flat conZinuous lower slurclc~ and a first- and s~cond !.ab at t-hc lowcr c~dge of the insert at a location which corresponds to the r~cesses in the tray. A narrow slot is provid~d in the lowcr surface of th~ ins~rt and spaccd immediatcly b~hind at l~ast the first tab to allow the first tab to deflect when -the ins~rt is forccd into the tray.
1~5~
-3a-Descriptlon of the Drawings.
., . . . . . ~
E'ig. 1 shows an isometric view of an assembled prosthesis made according to the present invention.
Fig. 2 shows an exploded view of the two components of the prosthesis of the present invention.
Fig. 3 shows the bottom plan view of the plastic portion of the present prosthesis.
Fig. 3A shows a fragmentary view of the bottom plan view of the plastic portion of the prosthesis showing an alternative construction.
Fig. 4 shows a top plan view of the metal tray component of the present invention.
Figs. 5 and 6 show a technique to insert the plastic compo-nent of th~ present invention into the metal tray.
Fig. 7 shows placement of an extraction tool to remove the plastic insert from the metal tray.
Figs. 8 and 9 show a detailed fragmentary view of the locking elements in the plastic portion of the present - prosthesis.
Figs. 10 and 11 show details of the locking elements in the metal portion of the tray.
1~
Detailed Descri tion of the Present lnvention P
Although the present invention will be described in refer-ence to a tibial component of an artificial knee, the invention can be used for other implantable prostheses where a removable plastic insert is used in combination with a tray which is implanted in the human bone. An example of such other prostheses would include a shoulder prosthesis.
o Fig. 1 shows the completelv assem~led prosthesis of the present invention. It includes a metal tray component 15 into which is inserted a plastic element 16, which is hereinafter referred to as an insert. The metal tray can ~5 be any of the metals commonly used in the manufacture of implantable prostheses. The most common metals used for this purpose are titanium, chrome-cobalt alloys and stainless steel. Although the preferred material of construction of the tray is metal, it should be understood that reinforced plastics which are biologically compatible with the human body could also be employed to make the tray portion of the prosthesis. The plastic insert is usually made of medical grade ultrahigh molecular weight polyethylene. The polyethylene has the re~uired properties of rigidity and smoothness that allows the metal component of the prosthesis to ride on the plastic and be ca?able of moving readilv to provide the required degree of articulation for a knee prosthesis. The up?er surface of the tibial component has cup shaped bearing surfaces 35 which the condylar portions of the femoral component contact in the implanted prosthesis. There is a raised post 38 between the bearing surfaces which con-strains lateral movement of the knee. The upper surface topography of the insert can be varied depending on the degree of constraint desired in the prosthesis. The height of the post 38 above the bearing surfaces 35 and the configuration of the post can be varied to control the degree of constraint of the implanted prosthesis. The upper surface topography could be that shown in U.S.
Patent 4,213,209 or ~.~. Patent 4,2g8,99~.
Fig. 2 shows an exploded view of the two components. The ste~s 17 are shown on the lower surface of the tray por-tion 15 of the prosthesis. In the implantation of the prosthesis, the upper surface of the tibial portion of the ~0 knee is usually cut to form a flat surface, and holes are drilled into that flat surface to accept the stem portions of the prosthesis. Although there are three stems shown in the present drawings, there may be a single stem or two stems, depending on the particular design of the prosthe-sis. There may be a porous metal or plastic coating 34 0,7one or more of the stems and on the bone contact surface of the tray. The pores in the porous coating are of sufficient size to allow bone to grow into the pores to more securely fix the prosthesis in place. ~1hen the present invention is used for a prosthesis other than a tibial prosthesis a stem would be designed to fit into the particular bone into which it would be implanted. The center region 18 on the upper surface of the tibial trav is relatively flat. There is a wall l9 around the periphery of the central region to hold the plastic insert 15 in place. There is a cutout portion 20 shown in the JhJ -l ~ 5n -6 ~ 8~S~
-drawing which would be em?loyed in a tibial prosthesis used in a surgical procedure in which the cruciate ligaments of the patient would not be removed. This cutout area provides clearance for the cruciate ligaments after the implant is in place. There are recesses or undercuts in the wall 19 on at least two opposed sides of the prosthesis. In the drawings, these recesses are shown as 21, 22 and 23 in the anterior or front area of the metal portion of the prosthesis. Rather than three separate recesses, a single continuous recess may be employed. There are recesses 24 and 25 in Fig. 4 in the back or posterior portion of the metal portion of the prosthesis.
The lower surface of the plastic insert is best shown in Fig. 3. As shown in Fig. 3, the plastic insert has tabs 27, 28 and 29 on the front or anterior section of the insert. If there is a single recess in the anterior portion of the tray, there may be a single table or more than one tab on the anterior portion of the plastic insert. These tabs will fit into the recess or recesses on the tray portion of the insert. As shown in Fig. 3, there are slots 32 cut in the insert immediately behind each of the tabs on the anterior ~ortion of the insert.
~s shown in Fig. 3, the slot extends beyond the ends of the tab throuqh the lower surface of the insert. As shown in Fig. 3A, the slot 32A may only extend in the plastic insert 16A for a length which is the length of the tab 29A. The slot is shown in cross section in Fig. 9. It is necessary for these slots to be immediately in back or rearward of of the tabs. A single tab, positioned in the center of anterior portion of the insert, is sufficient to lock the insert into the tray. The tabs on the posterior section of the insert may be identical to the tabs on the anterior section of the insert or they may be a tab of the construction shown in Fig. 8 of the drawing. The tab J & J - 1 1 5 0 ~S~81~Z
shown in Fig. 8 is capable of sliding into the undercut or recess in the posterior wall of the tray. In order for the tabs to slide into the notches there m~st be clearance between the top of the wall of the tray and that portion of the insert which lies on the top of the wall. The clearance is provided by an arcuate cutout 26 in the top of the wall and a corresponding arcuate surface 33 made in the portion of the insert that will overlie the top of the wall of the tray. Figs. 8 and 9 show the details of the posterior (Fig. ~) and anterior (Fig. 9) tabs which match into corresponding recesses in the metal tray, which are shown in Fig. 10 and Fig. 11. The purpose of the slot 32 is to allow the tab to deflect when the plastic insert is pushed into the tray in the manner shown in Figs. 5 and 5.
The slots 32 extend from the bottom flat surface of the insert into the body of the insert. The slot should extend into the insert to a depth which is greater than the dimension from the bottom of the insert to the hori-zontal portion of the tab. The corners of the sliding tab shown in Fig. 8 may be rounded rather than cut on angles.
The curved surface 33 above the tab matches the arcuate cutout 26 in the tray. The curved surfaces allow the tabs to slide into the undercut or recesses without interference between the top of the wall 19 and the upper edge of the insert.
The snap tab is shown in detail in Fig. ~. The forward end of the tab may be cut on a radius to provide a camming action against the top edge of the wall 19 to force the tab to deflect rearward when a force is applied downward to set the insert into the tray. In an alternate con-struction, Fig. 5-7, the forward edge of the tab is angled at an angle of between about 45 and 60. This also provides a camming action to force the tab rearward when a force is applied downward to seat the insert into the tray. The width of the slot should be at least equal to ,~J-1150 -8- ~ 5~
the width of the table to allow the ta~ to be deflected into the 510t and clear the wall of the tray.
~hen it is desired to insert the plastic component, the posterior tabs are inserted into the posterior undercut or recesses of the tray by sliding the insert from front to bac~ of the tray until the tabs are in the recesses as shown in Fig. 5. The anterior portion of the tray is then positioned immediately over the anterior recesses and forced downward. ~Jhen the plastic insert is pushed down-ward, the tabs are deflected ~s they are capable of moving backward because of the slot behind the tabs in the bottom of the plastic insert. After the horizontal portion of the tabs have cleared the top of the recess, the tab will revert back to the position shown in Fig. ~, and the plastic insert will be firmly locked into the tray.
The bottom surface of the insert is flat and has a lower portion which is dimensioned to fit within the interior wall of the tray. The height of the lower portion is substantially the same as the height of the wall of the tray. The upper portion of the insert is dimensioned so that its outer periphery is the same as the outer periphery of the wall of the tray. The ~unction between the lower and the upper portions of the insert is a hori20ntal ledge that rests on the top of the wall 19 when the insert is in place in the tray. The dimensions of the lower portion of the plastic insert are slightly smaller, 1 to 25 thousands of an inch, than the dimensions of the space within the wall of the tray to compensate for the differences in thermal expansion between the plastic of the insert and the metal of the tray. The upper surface of the plastic insert need not be coextensive with the ton of the metal tray. The upper surface of the insert can extend beyond the dimensions of ~he tray if desired.
However, the lower surface of the plastic ins~rt must be J ~ J -1150 ~ ~8~5f~
_9_ dimensioned to fit within the wall of the metal tray and be locked into the tray.
As shown in Figs. 5 and 6 there is a cutout portion or opening 30 located ln the center of the anterior surface of the insert where the insert meets the top of the wall of the tray. The opening 30 is of a height and width to receive the forward end of the removal tool as shown in Fig. 7. The forward end of the tool has a bifurcated tip 36 with a portion of the tip integral with each of the handles of the toolO To remove the insert from the tray, the tip is inserted into the cutout portion and the handles 37 forced towards one another moving the tip portions 36 in opposite directions and forcing the insert out of the tray.
The tip of the extraction tool may be of sufficient length so that force may be exerted against the tab to push the tab back into the slot to allow the horizontal portion of the tab to clear the notch.
J~'-1150
Background of the Invention Field of the Invention The present invention relates, in general, to prosthetic devices such as artificial joints, particularly artifi-cial knee joints, and, more particularly, to suchdevices in which the plastic portion of the device can be replaced.
Prior Art Artificial implantable prostheses to replace human joints have been available for some time. These prostheses generally consist of a metallic portion which interfaces with a plastic member. For example, in a knee joint, the natural knee joint includes the end of a femur which has two knob-like processes, the medial condyle and the lateral condyle, which are smooth and rest on the medial condyle and lateral condyle of the tibia. The condyles of the tibia are very smooth and slightly cupped to pro-vide a surface on which the femur condyles can articulate.
In the event that a knee joint is replaced, the femur and/or the tibial portions of the joint are replaced.
The femoxal component is usually a metal implant which is anchored in the femur. The tibial component comprises an ultra-high molecular weight polye-thylene member which may be anchored in a metal tray. The polyethylene member provides the smooth-cupped surfaces on which the femoral component rests during norma~ motion. One of the draw-backs in such joint replacement procedures is the~ Eact tha-t the plastic components may slowly deform because of cold flow or may wear. The deformation or wear may require the eventual replacemen-t of at least the plas-tic portion of the tibial knee prosthesis.
The knee prosthesis must also be properly sized and fitted to the patient by the orthopaedic surgeon when the implant procedure is undertaken. Because of the great variety of different configurations of the human knee, there must be an extensive variety of different sized knee prostheses available to -the surgeon during the surgical procedure so that the proper prosthesis may be selec-ted for implantation. One of the vari-abilities in the prosthesis is the height of the tibial component of the joint. Prior patents have suggested that the tibial portion of the joint be composed of a metal tray and a replaceable polyethylene insert, so that the metal tray could be implanted into the tibia, and the surgeon would have available plastic components of different heights to properly size the prosthesis during the surgical procedure. In order to provide this flexibilityl it is necessary to have some system of securing the plastic component of the tibia prosthesis into the metal tray. U.S. Patent 4,257,129 discloses such a system with a metal tray and a removable poly-ethylene insert in the tray. The polyethylene insert is secured to the tray using a dovetail joint in the tray with a matching dovetail joint in the polyethylene insert. In addition, there are two pins to secure the insert into the tray. A first pin extends through the polyethylene insert and into the tray in the vertical direction, and a second pin extends in the horizontal direction to secure the first pin in position. To re-move the plastic insert, the pins are removed and the polyethylene insert can be removed by sliding the poly-ethylene insert outof the dove-tail grooves of the metal tray.
U.S. Patent 4,207,627 discloses a knee prosthesis with a metal tray and two plastic inserts. The plastic inserts ~5&~
hav~ a lip on one side which fits in a r~cess in the metal tray to r~tain th~ ins~rt in th~ tray.
Summary of -th~ Inv~ntion The present inv~ntion provides an improved prosthesis in which the plastic insert can b~ readily fitted into the m~tal tray. The prosthesis provides an improved locking system to more positivcly secure the plastic insert into the tray wi-~h-out using pins or similar locking components. In thc pr~s~nt device, th~ plastic insert is snap fitted into thc metal tray on two opposed sidcs of the ins~rt and, although sccur~ly affix~d in the tray~ th~ ins~rt may readily be removed if necessary.
According to a further broad aspect of th~ present invention th~r~ is provided an implantabl~ joint prosthesis comprising a metal tray and rigid plastic inscrt removably fitt~d into the tray. The tray has an upper surface and a lower surfacc.
The lower surfac~ has at least one stem for insertion in-to a human bonc. The upp~r surfac~ of -the m~tal tray has a g~nerally flat continuous central region and an upwardly ~xtending wall enclosing the major portion of thc central region. Rec~ss~s ar~ provided adjacent the base of the wall on opposit~ sides of the tray. Th~ rig:id pl ast..i.c i.ns~.rl: has a g~nerally flat conZinuous lower slurclc~ and a first- and s~cond !.ab at t-hc lowcr c~dge of the insert at a location which corresponds to the r~cesses in the tray. A narrow slot is provid~d in the lowcr surface of th~ ins~rt and spaccd immediatcly b~hind at l~ast the first tab to allow the first tab to deflect when -the ins~rt is forccd into the tray.
1~5~
-3a-Descriptlon of the Drawings.
., . . . . . ~
E'ig. 1 shows an isometric view of an assembled prosthesis made according to the present invention.
Fig. 2 shows an exploded view of the two components of the prosthesis of the present invention.
Fig. 3 shows the bottom plan view of the plastic portion of the present prosthesis.
Fig. 3A shows a fragmentary view of the bottom plan view of the plastic portion of the prosthesis showing an alternative construction.
Fig. 4 shows a top plan view of the metal tray component of the present invention.
Figs. 5 and 6 show a technique to insert the plastic compo-nent of th~ present invention into the metal tray.
Fig. 7 shows placement of an extraction tool to remove the plastic insert from the metal tray.
Figs. 8 and 9 show a detailed fragmentary view of the locking elements in the plastic portion of the present - prosthesis.
Figs. 10 and 11 show details of the locking elements in the metal portion of the tray.
1~
Detailed Descri tion of the Present lnvention P
Although the present invention will be described in refer-ence to a tibial component of an artificial knee, the invention can be used for other implantable prostheses where a removable plastic insert is used in combination with a tray which is implanted in the human bone. An example of such other prostheses would include a shoulder prosthesis.
o Fig. 1 shows the completelv assem~led prosthesis of the present invention. It includes a metal tray component 15 into which is inserted a plastic element 16, which is hereinafter referred to as an insert. The metal tray can ~5 be any of the metals commonly used in the manufacture of implantable prostheses. The most common metals used for this purpose are titanium, chrome-cobalt alloys and stainless steel. Although the preferred material of construction of the tray is metal, it should be understood that reinforced plastics which are biologically compatible with the human body could also be employed to make the tray portion of the prosthesis. The plastic insert is usually made of medical grade ultrahigh molecular weight polyethylene. The polyethylene has the re~uired properties of rigidity and smoothness that allows the metal component of the prosthesis to ride on the plastic and be ca?able of moving readilv to provide the required degree of articulation for a knee prosthesis. The up?er surface of the tibial component has cup shaped bearing surfaces 35 which the condylar portions of the femoral component contact in the implanted prosthesis. There is a raised post 38 between the bearing surfaces which con-strains lateral movement of the knee. The upper surface topography of the insert can be varied depending on the degree of constraint desired in the prosthesis. The height of the post 38 above the bearing surfaces 35 and the configuration of the post can be varied to control the degree of constraint of the implanted prosthesis. The upper surface topography could be that shown in U.S.
Patent 4,213,209 or ~.~. Patent 4,2g8,99~.
Fig. 2 shows an exploded view of the two components. The ste~s 17 are shown on the lower surface of the tray por-tion 15 of the prosthesis. In the implantation of the prosthesis, the upper surface of the tibial portion of the ~0 knee is usually cut to form a flat surface, and holes are drilled into that flat surface to accept the stem portions of the prosthesis. Although there are three stems shown in the present drawings, there may be a single stem or two stems, depending on the particular design of the prosthe-sis. There may be a porous metal or plastic coating 34 0,7one or more of the stems and on the bone contact surface of the tray. The pores in the porous coating are of sufficient size to allow bone to grow into the pores to more securely fix the prosthesis in place. ~1hen the present invention is used for a prosthesis other than a tibial prosthesis a stem would be designed to fit into the particular bone into which it would be implanted. The center region 18 on the upper surface of the tibial trav is relatively flat. There is a wall l9 around the periphery of the central region to hold the plastic insert 15 in place. There is a cutout portion 20 shown in the JhJ -l ~ 5n -6 ~ 8~S~
-drawing which would be em?loyed in a tibial prosthesis used in a surgical procedure in which the cruciate ligaments of the patient would not be removed. This cutout area provides clearance for the cruciate ligaments after the implant is in place. There are recesses or undercuts in the wall 19 on at least two opposed sides of the prosthesis. In the drawings, these recesses are shown as 21, 22 and 23 in the anterior or front area of the metal portion of the prosthesis. Rather than three separate recesses, a single continuous recess may be employed. There are recesses 24 and 25 in Fig. 4 in the back or posterior portion of the metal portion of the prosthesis.
The lower surface of the plastic insert is best shown in Fig. 3. As shown in Fig. 3, the plastic insert has tabs 27, 28 and 29 on the front or anterior section of the insert. If there is a single recess in the anterior portion of the tray, there may be a single table or more than one tab on the anterior portion of the plastic insert. These tabs will fit into the recess or recesses on the tray portion of the insert. As shown in Fig. 3, there are slots 32 cut in the insert immediately behind each of the tabs on the anterior ~ortion of the insert.
~s shown in Fig. 3, the slot extends beyond the ends of the tab throuqh the lower surface of the insert. As shown in Fig. 3A, the slot 32A may only extend in the plastic insert 16A for a length which is the length of the tab 29A. The slot is shown in cross section in Fig. 9. It is necessary for these slots to be immediately in back or rearward of of the tabs. A single tab, positioned in the center of anterior portion of the insert, is sufficient to lock the insert into the tray. The tabs on the posterior section of the insert may be identical to the tabs on the anterior section of the insert or they may be a tab of the construction shown in Fig. 8 of the drawing. The tab J & J - 1 1 5 0 ~S~81~Z
shown in Fig. 8 is capable of sliding into the undercut or recess in the posterior wall of the tray. In order for the tabs to slide into the notches there m~st be clearance between the top of the wall of the tray and that portion of the insert which lies on the top of the wall. The clearance is provided by an arcuate cutout 26 in the top of the wall and a corresponding arcuate surface 33 made in the portion of the insert that will overlie the top of the wall of the tray. Figs. 8 and 9 show the details of the posterior (Fig. ~) and anterior (Fig. 9) tabs which match into corresponding recesses in the metal tray, which are shown in Fig. 10 and Fig. 11. The purpose of the slot 32 is to allow the tab to deflect when the plastic insert is pushed into the tray in the manner shown in Figs. 5 and 5.
The slots 32 extend from the bottom flat surface of the insert into the body of the insert. The slot should extend into the insert to a depth which is greater than the dimension from the bottom of the insert to the hori-zontal portion of the tab. The corners of the sliding tab shown in Fig. 8 may be rounded rather than cut on angles.
The curved surface 33 above the tab matches the arcuate cutout 26 in the tray. The curved surfaces allow the tabs to slide into the undercut or recesses without interference between the top of the wall 19 and the upper edge of the insert.
The snap tab is shown in detail in Fig. ~. The forward end of the tab may be cut on a radius to provide a camming action against the top edge of the wall 19 to force the tab to deflect rearward when a force is applied downward to set the insert into the tray. In an alternate con-struction, Fig. 5-7, the forward edge of the tab is angled at an angle of between about 45 and 60. This also provides a camming action to force the tab rearward when a force is applied downward to seat the insert into the tray. The width of the slot should be at least equal to ,~J-1150 -8- ~ 5~
the width of the table to allow the ta~ to be deflected into the 510t and clear the wall of the tray.
~hen it is desired to insert the plastic component, the posterior tabs are inserted into the posterior undercut or recesses of the tray by sliding the insert from front to bac~ of the tray until the tabs are in the recesses as shown in Fig. 5. The anterior portion of the tray is then positioned immediately over the anterior recesses and forced downward. ~Jhen the plastic insert is pushed down-ward, the tabs are deflected ~s they are capable of moving backward because of the slot behind the tabs in the bottom of the plastic insert. After the horizontal portion of the tabs have cleared the top of the recess, the tab will revert back to the position shown in Fig. ~, and the plastic insert will be firmly locked into the tray.
The bottom surface of the insert is flat and has a lower portion which is dimensioned to fit within the interior wall of the tray. The height of the lower portion is substantially the same as the height of the wall of the tray. The upper portion of the insert is dimensioned so that its outer periphery is the same as the outer periphery of the wall of the tray. The ~unction between the lower and the upper portions of the insert is a hori20ntal ledge that rests on the top of the wall 19 when the insert is in place in the tray. The dimensions of the lower portion of the plastic insert are slightly smaller, 1 to 25 thousands of an inch, than the dimensions of the space within the wall of the tray to compensate for the differences in thermal expansion between the plastic of the insert and the metal of the tray. The upper surface of the plastic insert need not be coextensive with the ton of the metal tray. The upper surface of the insert can extend beyond the dimensions of ~he tray if desired.
However, the lower surface of the plastic ins~rt must be J ~ J -1150 ~ ~8~5f~
_9_ dimensioned to fit within the wall of the metal tray and be locked into the tray.
As shown in Figs. 5 and 6 there is a cutout portion or opening 30 located ln the center of the anterior surface of the insert where the insert meets the top of the wall of the tray. The opening 30 is of a height and width to receive the forward end of the removal tool as shown in Fig. 7. The forward end of the tool has a bifurcated tip 36 with a portion of the tip integral with each of the handles of the toolO To remove the insert from the tray, the tip is inserted into the cutout portion and the handles 37 forced towards one another moving the tip portions 36 in opposite directions and forcing the insert out of the tray.
The tip of the extraction tool may be of sufficient length so that force may be exerted against the tab to push the tab back into the slot to allow the horizontal portion of the tab to clear the notch.
J~'-1150
Claims (7)
1. An implantable joint prosthesis comprising a metal tray and rigid plastic insert removably fitted into said tray, said tray having an upper surface and a lower surface, said lower surface having at least one stem for insertion into a human bone, said upper surface of said metal tray having a generally flat continuous central region and an upwardly extending wall enclosing the major portion of the central region, recesses adjacent the base of the wall on opposite sides of the tray, said rigid plastic insert having a generally flat continuous lower surface and a first and second tab at the lower edge of the insert at a location which corres-ponds to the recesses in the tray, a narrow slot in the lower surface of the insert and spaced immediately behind at least the first tab to allow the first tab to deflect when the insert is forced into the tray.
2. The prosthesis of claim 1 in which the surface of the forward edge of the first tab is cut on a radius to provide a camming surface with said upwardly extending wall to force the body of the tab rearward when a force is applied.
3. The prosthesis of claim 1 in which the surface of the forward edge of the first tab is at an angle of from 45 to 60 degrees and the interior surface of the top of the wall is cut at a similar angle to provide a camming surface to force the body of the tab rearward when a force is applied.
4. The prosthesis of claim 2 in which the configuration of second tab and the matching recess in the tray are generally rectangular.
5. The prosthesis of Claim 1 in which the plastic insert has a lower portion and an upper portion, the lower portion of the insert having a height equal to the height of the wall of the tray and dimensioned to fit within the wall of the tray with a clearance of from 1 to 25 thousands of an inch.
6. The prosthesis of Claim 4 in which the top of the wall of the tray, at a location over the second tab, is cut away to provide clearance for the second tab to be freely positioned in its recess.
7. The prosthesis of Claim 4 in which there is an opening in the center of the insert adjacent the top of the wall of the tray to receive a removal tool to remove the insert from the tray.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US73430085A | 1985-05-15 | 1985-05-15 | |
| US734,300 | 1985-05-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1258152A true CA1258152A (en) | 1989-08-08 |
Family
ID=24951111
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000508986A Expired CA1258152A (en) | 1985-05-15 | 1986-05-13 | Joint prosthesis |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1258152A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5108442A (en) * | 1991-05-09 | 1992-04-28 | Boehringer Mannheim Corporation | Prosthetic implant locking assembly |
| WO2000059411A1 (en) * | 1999-04-02 | 2000-10-12 | Fell Barry M | Surgically implantable knee prosthesis |
-
1986
- 1986-05-13 CA CA000508986A patent/CA1258152A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5108442A (en) * | 1991-05-09 | 1992-04-28 | Boehringer Mannheim Corporation | Prosthetic implant locking assembly |
| WO2000059411A1 (en) * | 1999-04-02 | 2000-10-12 | Fell Barry M | Surgically implantable knee prosthesis |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5147405A (en) | Knee prosthesis | |
| EP0510103B1 (en) | Prosthesis | |
| US4257129A (en) | Prosthetic knee joint tibial implant | |
| EP0904750B1 (en) | Rotatable joint prosthesis with axial securement | |
| US4759767A (en) | Prosthesis for tibial component of knee joint | |
| EP1104268B1 (en) | Retaining mechanism for a modular tibial component of a knee prosthesis | |
| CA2598630C (en) | Knee implant | |
| US6053945A (en) | Joint prosthesis having controlled rotation | |
| US6569202B2 (en) | Tray and liner for joint replacement system | |
| US5207711A (en) | Knee joint prosthesis | |
| US5201768A (en) | Prosthesis for implant on the tibial plateau of the knee | |
| EP2042134B1 (en) | Fixed-bearing knee prosthesis having interchangeable components | |
| US4205400A (en) | Metallo-polymeric prosthesis with cavitied interconnection | |
| EP2485686B1 (en) | Tibial implant base | |
| US4714474A (en) | Tibial knee joint prosthesis with removable articulating surface insert | |
| US5871541A (en) | System for producing a knee-joint endoprosthesis | |
| US6916340B2 (en) | Tibial prosthesis convertible in vivo to a modular prosthesis | |
| EP2319462B1 (en) | Prosthesis with composite component | |
| SE468199B (en) | KNAELEDSPROTES | |
| EP3626209B1 (en) | Tibial tray with fixation features | |
| EP1585464A2 (en) | Mobile bearing patellar prosthesis with orbital translation | |
| EP2574311B1 (en) | Fixed-bearing knee prosthesis having a locking mechanism with a concave-to-convex mating interface | |
| US20240041615A1 (en) | Tibial tray inserter | |
| CA1258152A (en) | Joint prosthesis | |
| CN113631122A (en) | Tibial baseplate for tibial component of knee prosthesis (tibial component including tibial baseplate) and method of manufacturing tibial baseplate |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |