IE43512B1 - A femoral prosthesis - Google Patents

Abstract

1515021 Prosthetic knee joints RICHARDS MFG CO 8 May 1975 [8 May 1974] 19353/75 Heading A5R A femoral prosthesis 13 for a tibiofemoral joint, comprises an elongate lateral condyle member 19 and an elongate medial condyle member 21, each condyle member having longitudinally convexly curved articulating surface 29 for replacement of the corresponding condoloid articulating surface of the femur and an internal surface consisting of a planar portion adjacent one end of the condyler member and a longitudinally concavely curved portion adjacent the other end of the condyler member, a connecting member 27 extending between the one ends of the condyle members so as to maintain the condyle members in a transversely spaced relationship with their elongate axes parallel and their respective articulating surfaces in alignment, and means capable of anchoring the prosthesis to the lower end of the femur adjacent the tibia with the one ends of the condyle members positioned towards the arterial portion of the joint.

Description

This invention relates to a femoral prosthesis for use in correcting efective tibio-femoral knee joint, and particularly in the human knee joint.

Heretofore, various prostheses have been proposed for use in treating ective knee joints, for instance those described and claimed in Patent No. 395 and British Patent No. 1,390,494. Certain of these prostheses have n employed successfully, but have not always proved entirely satisfactory, tain of the prior prostheses, for example require a large amount of bone ?val and a complexity of operative procedures - this applies particularly to those stheses in which the entire joint between the tibia and femur is replaced. 3r prior prostheses, while requiring a minimum amount of bone removal and itively simple operative procedures, do not maintain the natural alignment reen the lateral and medial articulating surfaces of the knee joint. Still :r prior prostheses, while maintaining perfect alignment between the lateral medial articulating surfaces of the knee joint, tend to interfere with the :iate ligament of the knee joint, and are only of use in joints where the :iate ligament and/or menisci components of the knee joint are destroyed or have ι removed. - 2 43*12 The present invention seeks to provide a femoral prosthesis for the tibio-femoral joint that reduces or overcomes the problems and disadvantages of the prior prostheses.

Accordingly, this invention provides a femoral prosthesis for a tibio5 femoral joint, which prosthesis comprises an elongate lateral condyle member and an elongate medial condyle member, each condyle member having a longitudinally convexly curved articulating surface for replacement of the corresponding condoloid articulating surface of a femur and an internal surface consisting of a substantially planar portion adjacent one end of the condyle member and a longitudinally concavely curved portion adjacent the other end of the condyle member, a connecting member fixedly attached to and extending between the one ends of the condyle members so as to maintain the condyle members in a transversely spaced relationship with their elongate axes parallel and their respective articulating surfaces in alignment, and means capable of anchoring the prosthesis to the lower end of the femur adjacent the tibia with the one ends of the condyle members positioned towards the anterior portion of the joint and with the internal surfaces of the condyle members facing the femur.

The condyle members are similarly shaped and their articulating surfaces are held in alignment - that is to say, the curves defined by the two articulating surfaces have their origins on a common axis. It is the function of the connecting member to maintain the alignment and transverse spacing of the condyle members, so that the natural positioning of the lateral and medial articulating surfaces in the knee joint may be maintained when using the prosthesis of the invention; furthermore, the fixed spacing of the condyle members may simplify the operating procedures required for anchoring the prosthesis to the femur. The connecting member is preferably recessed from the articulating surfaces of the condyle members.

It is important that the connecting member should not interfere with the cruciate ligament of the knee joint. This is achieved by forming the prosthesis so that when it is anchored to the femur the connecting member lies towards the - 3 i δ 13 iterior of the joint. The anterior surface of the connecting member is preferably >ncave, to avoid the possibility of interference with the patella.

The articulating surfaces of the condyle members should be shaped so ; to be compatible with the plateau-like medial and lateral articulating surface on le tibia, and thus their shape reflects that of the portions of the condoloid irface of the femur that they replace. Preferably the articulating surfaces ‘scribe polycentric convex curves in a single, longitudinal direction.

It is an important aspect of the present invention that the femoral •osthesis replaces substantially only the articulating surfaces of the femur, id thus reduces to a minimum the amount of bone removal required when anchoring ie prosthesis to the femur.

The means for anchoring the prosthesis to the femur preferably comprises e or more pegs upstanding from the internal surface of each condyle member, us, when the prosthesis is in position, the pegs may extend into holes formed the femur, generally being bound to the femur by a bone cement. One or more ooves are advantageously formed in and around each peg, which effectively increases e ability of the pegs to bind securely with the bone.

The anchorage of the prosthesis to the femur may be further assisted the provision of one or more grooves extending across the internal surface of ch condyle member, preferably across the longitudinally concavely curved portion ereof, which correspond to the posterior ends of the condyle members when the Dsthesis is anchored to the femur.

The femoral prosthesis of the invention may be employed in a tibio-femoral int in conjunction with a normal healthy femur. However, it often is the case it the femur and the tibia are both damaged, and both must be replaced. In that snt it is preferable to use the femoral prostheses of this invention in conjunction th a tibial prosthesis, such as is described and claimed in the aforesaid tent No. 998/80 which has been divided out of this application.

Some preferred aspects of the present invention will now be described, lugh only by way of illustration, with reference to the drawings in which:- 4 43512 Figure 1 is a side elevational view of a femoral prosthesis of the present invention.

Figure 2 is a front elevational view of femoral prosthesis of Figure 1.

Figure 3 is a top plan view of the femoral prosthesis of Figure 1.

Figure 4 is a top plan view of a tibial prosthesis constructed in accordance with the aforesaid Patent No. 998/80.

Figure 5 is a front elevational view of the tibial prosthesis of Figure 4, Figure 6 is a bottom plan view of the tibial prosthesis of Figure 4.

Figure 7 is a sectional view as taken on line VII-VII of Figure 5.

Figure 8 is a sectional view similar to Figure 7 but showing an alternative embodiment of a tibial component constructed in accordance with the aforesaid Patent No. 998/80.

Figure 9 is a somewhat diagrammatic side view of a tibio-femoral joint comprising a femoral prosthesis of the present invention and a tibia prosthesis according to the aforesaid Patent No. 998/80.

Figure 10 is a somewhat diagrammatic front view of the tibio-femoral joint of Figure 9.

The femoral prosthesis 13 of the present invention is for use in replacing the articulating surfaces of the femur 17 in a tibio-femoral joint 11 in a human knee. The prosthesis 13 comprises an elongate lateral condyle member 19 and an elongate medial condyle member 21 for replacing the articulating surfaces of the lateral condyle 23 and the medial condyle 25 of the femur 17. The articulating surface 29 of each condyle member 19, 21 is substantially the same shape as the normal articulating surface of each condyle 23, 25 of the femur 17. More specifically, the articulating surface of each condyle member 19, 21 is a convex polycentric curve. The femoral prosthesis 13 also comprises a connecting member 27 for fixedly connecting the lateral and medial condyle members 19, 21 together in a transversely spaced relationship to maintain perfect alignment therebetween and to prevent the condyle members 19, 21 from interfering with the cruciate ligament of the knee joint. - 5 ί connecting member 27 holds the condyle members 19, 21 apart a distance equal to = natural separation of the condyles 23, 25 of the femur 17. The connecting nber 27 is recessed from the articulating surface 29 of each of the condyle nbers 19, 21 and is positioned adjacent the: anterior end 31 of each of the idyle members 19, 21 so as not to interfere with the cruciate ligament of the =e joint and to allow full extension of the knee. The anterior side 33 of the meeting member 27 is concave as it extends between the lateral and medial condyle nbers 19, 21 for peventing the femoral component 13 from interfering with the tella of the knee joint. The femoral prosthesis 13 has anchoring means for ; internal surface 37 of each of the condyle members 19, 21 consists of a jstantially planar anterior portion and a longitudinally concavely curved ;terior portion, there being a peg 35 upstanding from the anterior portion of :h of the condyle members 19, 21 for extending into a corresponding cavity 39 in : condyles 23, 25 of the femur 17. The pegs 35 are preferably square in insverse cross section, and are tapered towards the distal end thereof to wide a taper lock fit with the corresponding cavity 39. A plurality of joves 41 are provided in and around each peg 35 for increasing the fixation >reof. The anchoring means also includes a plurality of grooves 43 extending •oss the inward face 37 of each of the condyle members 19, 21, adjacent the iterior ends 45 thereof.

The femoral prosthesis of the invention may be used in a tibio-femoral int in conjunction with a healthy tibia, but where the tibia is damaged, it is iferably used in conjunction with the tibial prosthesis described and claimed the aforesaid Patent No. 998/80 embodiments of which are shown in gures 5 to 10.

The tibial prosthesis 15 comprises an elongate lateral plateau member 49 I an elongate medial plateau member 51 for replacing the articulating surfaces of the :eral plateau 53 and the medial plateau 55 of the tibia 47. Each plateau member has a substantially planar articulating surface 61 for coacting with the - 6 43512 femoral prosthesis 13. The planar articulating surface 61 allows the femoral prosthesis 13 to freely slide back and forth on the tibial prosthesis 15, thus enabling the two prostheses to find the best relative disposition for their coaction. However, where the ligaments of the knee joint are not strong, each plateau member 49, 51 preferably has a concave articulating surface 61^ (see Fig. 8) for limiting the amount of sliding movement of the femoral prosthesis 13 on the tibial prosthesis 15. The tibial prosthesis 15 comprises also a connecting member 57 for fixedly connecting the lateral and medial plateau members 49, 51 in a transversely spaced relationship with their elongate axis parallel and their articulating surfaces in alignment. The separation of the plateau members 49, 51 is necessary to prevent them from interfering with the cruciate ligament of the knee joint, and the connecting member 57 is positioned adjacent the anterior end 59 of the plateau members 49, 51 so as not itself to cause such interference.

Each plateau member 49, 51 has a longitudinal guide which is co-operable with the femoral prosthesis 13 to maintain the natural configuration of the bones in the joint. In the case of the lateral plateau member 49, this is an abutment surface 63 upstanding perpendicularly from the medial edge of the articulating surface 61 so as to abut the lateral condyle member 19 of the femoral prosthesis 13; and in the case of the medial plateau member 51, the longitudinal guide is an abutment surface 65 upstanding perpendicularly from the lateral edge of the articulating surface 61 so as to abut the medial condyle member 21 of the femoral prosthesis 13. The abutment surfaces 63, 65 each face the articulating surface from which they upstand, and are longitudinally convexly curved so as to allow the femoral prosthesis 13 a limited degree of rotation on the tibial prosthesis 15 about a vertical axis as their articulating surfaces coact. The abutment surfaces 63, 65 thus ensure that the articulating surfaces of the femoral and tibial prostheses coact properly, and prevent the condyle members of the femoral prosthesis from interfering with the cruciate ligament of the knee joint. - 7 ! S i 2 The tibial prosthesis 15 has anchoring means for fixedly anchoring the ibial prosthesis 15 to the upper end of the tibia 47. The anchoring means omprises a peg 67 upstanding from an internal surface 69 of each plateau member 49, 51 he peg being substantially adjacent the centre of the internal surface. The peg 67 s for the extension into a corresponding cavity 71 in the tibia 47. The pegs 67 are ircular in transverse cross section. Also, each peg 67 is tapered toward the istal end thereof to provide a tapered lock with the corresponding cavity 71. ich peg 67 has a circumferential groove 73 for increasing the fixation thereof, le anchoring means also includes a plurality of channels 75 located in the iternal surface 69 of each of the plateau members 49, 51 around each of the pegs 67. ich of the channels 75 preferably includes an undercut portion 77 for increasing the ixation thereof.

The femoral prosthesis 13 of the invention is preferably a one-piece instruction composed of a metallic material such as stainless steel or chromium ibalt alloy. The tibial prosthesis 15 is preferably a one-piece construction imposed of an ultra-high molecular weight polyethylene. It should be noted that ich peg 67 of the tibial prosthesis 15 is preferably provided with a marker 79 : stainless steel or chromium cobalt alloy wire or the like to provide an accurate ference for radio graphic determination of position and wear rates of the tibial os thesis 15.

The replacement of the articulating surfaces of the tibio-femoral joint th the femoral prosthesis 13 of the present invention and the tibial prosthesis 15 11 now be described. An incision is first made to allow access to the lower end the femur 17 and the upper end of the tibia 47 by means and methods well known to ose skilled in the art. The lateral and media) plateau 53,55 of the tibia 47 e then contoured by well known means to properly accommodate the tibial prosthesis Next, the lateral and medial condyles 23, 25 of the femur 17 are contoured by known means to properly accommodate the femoral prosthesis 13 taking into account / varus or valgus deformities, flexion contracture or hyper-extension of the tibionoral joint. The tibial prosthesis 15 is then fixedly anchored to the upper end - 8 43512 of the tibia 47 with the aid of a typical bone cement well known to those skilled in the art. The bone cement coacts with the pegs 67, circumferential grooves 73, channels 75 and undercut portions 77 to fixedly anchor the tibial prosthesis 15 to the upper end of the tibia 47. Next, the femoral prosthesis 13 is fixedly anchored to the lower end of the femur 17 with the aid of bone cement. The bone cement coacts with the pegs 35, the grooves 41 in and around the pegs and the grooves 43 to fixedly anchor the femoral prosthesis 13 to the lower end of the femur 17. It should be noted that the grooves 43 help prevent excess cement from excaping from between the femoral prosthesis 13 and the femur 17 as the femoral prosthesis 13 is being anchored to the femur 17. The incision is then closed in the manner well known to those skilled in the art.

Claims (3)

1. A femoral prosthesis for a tibio-femoral joint, which prosthesis comprises an elongate lateral condyle member and an elongate medial condyle member, each condyle member having a longitudinally convexly curved articulating surface for replacement of the corresponding condoloid articulating surface of a femur and an internal surface consisting of a substantially planar portion adjacent one end of the condyle member and a longitudinally concavely curved portion adjacent the other end of the condyle member, a connecting member fixedly attached to and extending between the one ends of the condyle members so as to maintain the condyle members in a transversely spaced relationship with their elongate axes parallel and their respective articulating surfaces in alignment, and means capable of anchoring the prosthesis to the lower end of the femur adjacent the tibia with the one ends of the condyle members positioned towards the anterior portion of the joint and with the internal surfaces of the condyle members facing the femur.

2. A femoral prosthesis as claimed in Claim 1, in which the connecting member is recessed from the articulating surfaces of the condyle members.

3. A femoral prosthesis as claimed in Claim 1 or Claim 2 in which the anterior side of the connecting member is concave. - 9 13 A femoral prosthesis as claimed in any of the preceding claims, in which means for anchoring the prosthesis to the femur comprises one or more pegs .anding from the internal surface of each condyle member. A femoral prosthesis as claimed in Claim 4, in which there is one peg landing from each condyle member. A femoral prosthesis as claimed in Claim 5, in which each peg member a square transverse cross-section and is tapered towards the distal end. A femoral prosthesis as claimed in any of Claims 4 to 6, in which there one or more grooves formed in and around each peg. A femoral prosthesis as claimed in any of Claims 4 to 7, in which the is for anchoring the prosthesis to the femur also comprises one or more grooves inding across the internal surface of each condyle member. A femoral prosthesis as claimed in Claim 8, in which the grooves are led in the longitudinally concavely curved portion of the internal surface of ι condyle member. A femoral prosthesis as claimed in any of the preceding claims, which ;omposed of a metal. A femoral prosthesis as claimed in Claim 10, in which the metal is nless steel or a chromium cobalt alloy. A femoral prosthesis substantially as described hereinbefore with rence to Figures 1, 2 and 3 of the accompanying drawings.