WO2004100839A1

WO2004100839A1 - A prosthetic component, a method of attaching a prosthetic component to a bone, a method of performing knee replacement surgery and a frame for application to a knee joint during knee replacement surgery

Info

Publication number: WO2004100839A1
Application number: PCT/AU2004/000659
Authority: WO
Inventors: Eugene Sherry; Boris Rjazancev
Original assignee: Eugene Sherry; Boris Rjazancev
Priority date: 2003-05-19
Filing date: 2004-05-19
Publication date: 2004-11-25
Also published as: AU2003902467A0

Abstract

The prosthetic component (1) includes a plurality of formations, in the form of circular projections (2, 3 and 4), which inter-engage with corresponding formations, in the form of recesses (54, 55 and 56) provided in the bone. Some of the disclosed preferred methods enable the preferred embodiment (1) to be slidably engaged with the bone (8) from either the medial or the lateral side of the knee joint. Also disclosed is a frame (37) and associated jig (46) to assist a surgeon to form the required corresponding formations in a bone (8).

Description

TITLE: "A prosthetic component, a method of attaching a prosthetic component to a bone, a method of performing knee replacement surgery and a frame for application to a knee joint during knee replacement surgery."

FIELD OF THE INVENTION:

The present invention is predominantly applicable to the field of orthopaedic surgery and in particular to the insertion of prosthetic components onto bone. Other aspects of the invention are particularly applicable to the field of knee replacement surgery and will be described hereinafter with reference to this application. However, it will be understood that the invention is not limited to this particular field of use.

BRIEF DISCUSSION OF THE PRIOR ART

Known prosthetic components are generally attached to bones via spikes, stems or fastening means such as screws, nails etc. For example, in knee replacement surgery the femoral and tibial prosthetic components are typically driven into the ends of the femur and tibia by displacing the stem or other fastening means along a direction which is parallel to the respective longitudinal axes of the femur and tibia. The longitudinal driving of a spike into the bone may inadvertently in some circumstances expel fatty material from within the bone into the circulatory system, potentially with serious or fatal ramifications for the patient. Additionally, to provide the access required to drive the prosthetic components in such a direction, it is typically necessary for the initial incision in knee replacement surgery to be positioned along the front of the knee joint, however this may lead to extended recuperation times due to the relatively low level of blood supply to this region of the knee.

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

SUMMARY OF THE INVENTION: According to a first aspect of the invention there is provided a prosthetic component fastenable to a bone, said prosthetic component including a formation for slidable engagement with a conesponding formation provided upon said bone such that said prosthetic component is keyed into said bone.

Preferably the formation interference fittingly engages the conesponding formation.

One prefened embodiment of the invention has a formation in the form of a projection disposed on the prosthetic component, the projection defining an elongate dimension. In this prefened embodiment the conesponding formation is a recess defined within the bone. Preferably the projection has a substantially constant cross sectional shape along the elongate dimension. More preferably the cross sectional shape is substantially circular. Similarly, the recess defined within the bone preferably has a substantially constant cross sectional shape which is more preferably substantially circular.

Preferably a plurality of projections each having parallel elongate dimensions are disposed on the prosthetic component and the conesponding formation is in the form of a plurality of parallel recesses defined within the bone.

Preferably the cylindrical projection is hollow and defines a housing for bone in the form of a cylindrical rod. Also preferably the cylindrical projection includes a plurality of apertures to allow bone growth through said apertures.

Also preferably, the formations provided upon the prosthetic component are resilientiy deformable so as to provide shock absorption intermediate the prosthetic and the bone.

According to a second aspect of the invention there is provided a method of attaching a prosthetic component to a bone of a patient, said method including the steps of: providing a prosthetic component having one or more elongate projections; boring one or more recesses into said bone; and slidably engaging said one or more projections with said one or more recesses so as to key said prosthetic component into said bone. According to a third aspect of the invention there is provided a method of performing knee replacement surgery to a knee joint of a patient, said method including the steps of: providing a prosthetic component having one or more projections; surgically accessing the knee joint from either a medial side or a lateral side of the knee joint; boring one or more recesses into a bone adjacent said knee joint; and slidably engaging said one or more projections with said one or more recesses so as to key the prosthetic component into said bone.

According to another aspect of the invention there is provided a frame for application to a knee joint during knee replacement surgery, said frame including: a frame body; attachment means disposed on said body for releasably securing the frame to a predefined point on said knee joint; and jig receiving means disposed on said body and adapted to secure one or more jigs onto said frame, each of said jigs including surgical tool guidance means adapted to direct surgical tools towards predefined sites on said knee joint.

Preferably the body includes first and second members adapted for respective disposition adjacent first and second sides of the knee joint. More preferably the first side is a medial side of the knee joint and the second side is a lateral side of the knee joint.

In one embodiment the attachment means includes at least one arm adapted for disposition along an epicondylar axis of said knee joint. In this embodiment the arm is adapted for clamping engagement with a lower femur adjacent the knee joint. More particularly, the arm is threadedly engagable with said body such that screwing of the arm displaces it towards the lower femur so as to provide the clamping engagement.

Preferably the arm is hollow so as to allow for passage of a first guide wire through the arm and into the femur to further attach the frame to said knee joint. A prefened embodiment includes one or more apertures allowing for passage of a second guide wire through said apertures and into said femur to further attach the frame to said knee joint. Preferably the first guide wire is parallel to, and spaced apart from, the second guide wire, when in use. A prefened embodiment has one or more jigs which include hollow cylinders having an outer surface for guiding soft tissue adjacent the knee joint and an inner surface adapted to guide one or more coring tools. Preferably the internal surface of the hollow cylinder has a diameter sized so as to match an exterior diameter of said coring tool so as to orient and position the coring tool relative to predefined sites on the knee joint.

Preferably, whilst guided by the hollow cylinders, the coring tools are parallel to the epicondylar axis and are positioned so as to minor a disposition of projections on a compatible prosthetic component.

A prefened embodiment further includes apertures allowing for passage of a third guide wire through the apertures and into the femur and for allowing for passage of a fourth guide wire through the apertures and into the femur. In such an embodiment, outer edges of the guide wires and the coring tools define resection planes for osteotomy of a femoral condyle of the knee joint.

The prefened embodiment further includes tibial jigs for the positioning and guiding of coring tools for coring of the tibia. Preferably the tibial jigs also provide guidance for the osteotomy of the tibia.

According to yet another aspect of the invention there is provided a prosthetic component for knee replacement surgery, said prosthetic component being fastenable to a bone having an elongate dimension, said prosthetic component including a formation for slidable engagment with a conesponding formation provided upon said bone, said slidable engagement taking place in a direction transverse to said elongate dimension.

Preferably the formation has a substantially constant cross sectional shape extending in said direction transverse to said elongate dimension and the conesponding formation also has a substantially constant cross sectional shape extending in said direction transverse to said elongate dimension.

In one prefened embodiment the formation is a plurality of parallel fins extending in said direction transverse to said elongate dimension and the conesponding formation is a plurality of parallel channels extending in said direction transverse to said elongate dimension. In an alternative prefened embodiment the formation is a plurality of parallel channels extending in said direction transverse to said elongate dimension and the conesponding formation is a plurality of parallel fins extending in said direction transverse to said elongate dimension.

Preferably said direction transverse to said elongate dimension extends between a medial side of the knee and a lateral side of the knee.

BRIEF DESCRIPTION OF THE FIGURES:

A prefened embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a plan view of a left femoral prosthetic component according to the present invention; Figure 2 is a rear view of the left femoral prosthetic component;

Figure 3 is a front view of the left femoral prosthetic component;

Figure 4 is a cross sectional side view of the left femoral prosthetic component, with the cross section taken along line 4 - 4 of figure 1;

Figure 5 is a plan view of a right femoral prosthetic component according to the present invention;

Figure 6 is a rear view of the right femoral prosthetic component;

Figure 7 is a front view of the right femoral prosthetic component;

Figure 8 is a sectional side view of the right femoral prosthetic component, with the cross section taken along line 8 - 8 of figure 5; Figure 9 is a front view of a tibial prosthetic component according to the present invention;

Figure 10 is a side view of the tibial prosthetic component;

Figure 11 is a bottom view of a tibial prosthetic component;

Figure 12 is a plan view of a spacer prosthetic component according to the present invention;

Figure 13 is a cross sectional view of the spacer prosthetic component with the cross section taken along line 13 - 13 of figure 12; Figure 14 is a cross sectional view of a spacer prosthetic component having a positive inclination, with the cross section taken along line 14 - 14 of figure 12;

Figure 15 is a cross sectional view similar to that of figure 14, however in relation to a spacer having a negative inclination; Figure 16 is a cross sectional view similar to that of figure 14, however in relation to a spacer having a normal inclination;

Figure 17 is a side view of a patella prosthetic component according to the present invention;

Figure 18 is a plan view of a patella prosthetic component according to the present invention;

Figure 19 is a front view of a patella prosthetic component according to the present invention;

Figure 20 is a front view of alternative embodiments of femoral and patella prosthetic components according to the present invention; Figure 21 is a side view of the femoral and patella prosthetic components;

Figure 22 is a pre-operative perspective view of a patient's knee with a line showing the geometry of the initial incision in a prefened method according to the invention;

Figures 23 and 24 are perspective views of a knee joint showing reference axes used in the prefened method;

Figure 25 is a perspective view showing a surgeon palpating the epicondylar axis of the lower femur;

Figure 26 is a perspective view showing a surgeon applying a frame along the epicondylar axis; Figure 27 is a perspective view showing a surgeon passing a guide wire through the lower femur;

Figure 28 is a perspective view showing a prefened alignment of the frame relative to the knee joint;

Figure 29 is a perspective view a surgeon passing a second guide wire through the lower femur;

Figure 30 is another perspective view showing a prefened alignment of the frame relative to the knee joint;

Figure 31 is a perspective view showing a jig as applied to the guide wires; Figure 32 is a perspective view showing a surgeon inserting soft tissue guides into the jig;

Figures 33 to 37 are perspective views showing coring of the lower femur;

Figure 38 is a perspective view showing a surgeon passing a third guide wire through the lower femur;

Figures 39 and 40 are perspective views showing the line along which the lower femur is osteotomised;

Figures 41 to 43 are perspective views of the osteotomised lower femur;

Figure 44 is a perspective view of prosthetic components used in the prefened method according to the invention;

Figure 45 is a perspective view of a femoral prosthetic component;

Figure 46 is a perspective view showing a femoral prosthetic component prior to insertion onto an osteotomised lower femur;

Figure 47 is a perspective view showing a surgeon sliding a femoral prosthetic component onto an osteotomised lower femur;

Figure 48 is a perspective view of a femoral prosthetic component mated with an osteotomised lower femur;

Figures 49 to 54 are perspective views of a prosthetic knee joint according to a prefened embodiment of the present invention; Figure 55 is a side view of a patella showing a portion which is resected;

Figure 56 is a side view of a patella prosthetic component which is installed in the place of the resected portion shown in figure 55;

Figure 57 is a schematic diagram showing a uni knee replacement;

Figure 58 is a schematic diagram showing a total knee replacement subsequent to the uni knee replacement shown in figure 57 using an extension of the same rails used for the uni knee replacement;

Figure 59 is a schematic diagram showing an initial medial incision to assist with the displacement of a patient's skin, fat and fascia;

Figure 60 is a schematic diagram showing a capsular incision to assist with the displacement of a patient' s fibrous sack which holds the bone ends together;

Figure 61 is a schematic diagram showing a front view of a frame as applied onto a patient's knee joint, with the patient's leg in the fully extended position;

Figure 62 is a schematic diagram showing a side view of the frame as applied to a patient's knee joint, with the patient's leg in the fully extended position; Figure 63 is a schematic diagram showing a femoral jig as applied to the frame, with the patient's leg in the fully extended position;

Figure 64 is a schematic diagram showing the resected femur and the tibial jig as applied to the tibia, with the patient's leg in the fully extended position; Figure 65 is a schematic diagram showing the resected femur and the tibial jig as applied to the tibia, with the patient's leg in the 90° flexed position;

Figure 66 is a schematic diagram showing the resected femur and the resected tibia;

Figure 67 is a schematic diagram showing the prosthetic components as applied to form a total knee replacement;

Figure 68 is a schematic diagram showing a resected upper tibia and a tibial prosthetic component poised for installation;

Figures 69 to 74 are schematic illustrations of an additional prefened embodiment of a method of preforming the invention; Figure 75 is a cross-sectional diagram showing an interface between an embodiment of the invention and a bone; and

Figure 76 is a cross-sectional diagram showing an alternative prefened formation engaged with a conesponding formation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS :

Referring to the figures, a first embodiment of a prosthetic component is a left femoral prosthetic component (1) which is adapted for fastening to the end of a patient's femur (8) adjacent the left knee joint (9). The femoral prosthetic component (1) includes a formation in the form of three cylindrical projections (2, 3 and 4) which each define parallel elongate dimensions. Each projection (2, 3 and 4) has a substantially constant cross sectional shape along the elongate dimension. In the illustrated prefened embodiments the cross sectional shape is circular, however it will be appreciated that other shapes could also be utilised. The projections (2, 3 and 4) are joined to the prosthetic component (1) along respective connection lines (10, 11 and 12) which extend along the length of the curved outer surface of each cylindrical projection (2, 3 and 4).

As best shown in figure 47, the projections are slidably engageable with a conesponding formation in the form of three recesses (5, 6 and 7) provided upon the bone (8). The recesses (5, 6 and 7) are parallel to each other. Each of the recesses (5, 6 and 7) defined within the bone (8) has a substantially constant cross sectional shape, which is circular.

However, in other prefened embodiments, the cross-sectional shapes of the formation and the conesponding formation differ. Nevertheless, the two cross-sectional shapes are capable of keying inter-engagement. An example of such an embodiment is shown in figure 76 in which the prosthetic component (120) has a formation (121) that has a rectangular cross-sectional shape, whereas the bone (123) has a conesponding formation

(122) that has a circular cross-sectional shape.

In one embodiment the diameter of the circular cross sectional shape of the recesses (5, 6 and 7) is roughly equal to that of the projections (2, 3 and 4). In other embodiments the diameter of the circular cross sectional shape of the recesses (5, 6 and 7) is very slightly less than that of the projections (2, 3 and 4) so as to provide an interference fit there between. It will be appreciated that other options are available for providing such an interference fit, for example in alternative embodiments the recesses and/or the projections (2, 3 and 4) are very slightly out of parallel. In yet further embodiments the recesses (2, 3 and 4) and/or the projections (2, 3 and 4) are very slightly off straight.

The prosthetic component (1) slides in a direction defined by the elongate dimensions of the projections (2, 3 and 4) onto the end of the bone (8), starting from either the medial side or the lateral side of the knee joint (9). Once slid onto the bone (8), the prosthetic component (1) is keyed into the bone (8). In other words, the engagement provided by the interlocking projections (2, 3 and 4) and recesses (5, 6 and 7) assists to retain the prosthetic component (1) onto the end of the bone (8) despite the application of a force on the prosthetic component (1) directed along the longitudinal axis of the femur (8).

The interference fit between the projections (2, 3 and 4) and the conesponding formations (5, 6 and 7) assists the prosthetic component (1) to resist transverse displacement relative to the bone (8) due to forces acting upon the prosthetic component (1) in a direction which is transverse to the longitudinal axis of the bone (8).

Each of the projections (2, 3 and 4) in the illustrated prefened embodiment is hollow to enable housing of bone in the form of cylindrical rods (13, 14 and 15). Additionally, the projections (2, 3 and 4) each feature a plurality of apertures (16) to allow bone growth there through. In other words, once the prosthetic component (1) is keyed onto the femur (8), bone can grow through the apertures (16) so as to meld with the cylindrical rods of bone (13, 14 and 15), thereby further strengthening the fastening of the prosthetic component (1) to the femur (8). However in other embodiments the projections are solid.

The projections (2, 3 and 4) are resilientiy deformable so as to provide shock absorption at the interface between the prosthetic (1) and the bone (8). This assists to minimise the transfenal between the prosthetic component (1) and the bone (8) of any jarring forces that may be generated tlirough use of the prosthetic component (1).

A right femoral prosthetic component (17) is illustrated in figures in figures 5 to 8, upon which the same reference numerals mentioned above have been inserted to illustrate similar features. The outer surfaces (18) of the femoral prosthetic components (1 and 17) are designed in accordance with known principles of knee prosthetic components to allow for replacement of a knee joint.

The femoral prosthetic component (1) includes a trochlear groove (91) along which the patella (either the patient's natural patella, or a prosthetic patella (79), as the case may be) is slidably engagable.

Figures 9, 10 and 11 illustrate a prosthetic tibial component (19) which is adapted for fastening to the end of a patient's tibia (20) adjacent the left or right knee joint (9). The principles of fastening this prosthetic component (19) onto the tibia (20) are very similar to those associated with fastening the femoral prosthetic component (1) onto the femur (8), with the exception that two projections (21 and 22) are disposed on the prosthetic component (19) and two conesponding recesses (23 and 24) are bored into the tibia (20). The two projections (21 and 22) slide into engagement with the two recesses (23 and 24) from either the medial or the lateral sides of the knee joint (9), however in some prefened embodiments the sliding engagement takes place anteriorly or posteriorly. Once the tibial prosthetic component has been installed, the upper surface (25) provides a platform upon which one of the spacers (26) illustrated in figures 12 is supported. These spacers (26) operate in a manner which is known to those skilled in the art. As best shown in figures 14 to 16, various types of spacers (26) are available to suit different patients. In particular, the spacers (26) may feature a positive inclination, a negative inclination or a neutral inclination depending upon the desired prosthetic knee joint geometry.

Figures 17 to 19 illustrate a patella prosthetic component (29). This component is attached to the patella via projections (27 and 28) in a manner similar to that described above with reference to the femoral and tibial prosthetic components (1 and 19). Two conesponding recesses are bored into the patella to receive projections (27 and 28) and once again the component (29) is slid onto the patella from either the medial or lateral sides of the knee j oint (9) .

The components illustrated in figures 1 to 19 are utilised in a full knee replacement surgery. However, other embodiments of the invention are applicable to uni knee replacement and patello-femoral knee replacement surgery. In particular, prosthetic components suitable for patello-femoral knee replacement surgery are illustrated in figures 20 and 21. The femoral prosthetic component (30) for uni knee replacement surgery comprises an upper portion of the component (1) used for full knee replacement surgery. Prosthetic components suitable for uni knee replacement surgery are illustrated in figure 63.

A prefened method for attaching a prosthetic component (1) to a bone (8) of a patient includes the steps of firstly providing a prosthetic component (1) having a plurality of elongate projections (2, 3 and 4). Secondly, recesses (5, 6 and 7) are bored into the bone (8). Finally, the projections (2, 3 and 4) are slidably engaged with the recesses (5, 6 and 7) so as to key the prosthetic component (1) into the bone (8).

More specifically with regard to knee replacement surgery, the prefened embodiment of a surgical method commences with a medially based "C" shaped incision (31) following the contour of the medial femoral condyle, as shown in figures 22 and 59. This incision (31) is typically of approximately 5 to 6 cm length and is parapatellar to the tibial plateau. This initial medial incision (31) assists with the displacement of a patient's skin, fat and fascia. Advantageously, positioning the initial incision (31) adjacent to the medial femoral condyle ensures that the incision is spaced sufficiently far away from the tibial tubercle to minimise the risk of damaging the vulnerable tibial tubercle. As will be appreciated by those skilled in the art, damage to the tibial tubercle is extremely undesirable as the poor blood flow to the tibial tubercle generally necessitates extremely long recuperation periods. Additionally, the positioning of the incision (31) helps to ensure that the extensor mechanism of the knee is not disturbed. This contrasts with the initial incision typically made in prior art knee replacement surgery which is usually along the front of the knee and therefore closer to more vulnerable bodily parts. A second incision (89), as shown in figure 60, is a capsular incision to assist with the displacement of a patient's fibrous sack which holds the bone ends together. This second incision (89) follows a similar line to that of the first incision (31) , with the exception of the end (90) which is adjacent the medial ligament (91). h this region the second incision (89) diverges away from the medial ligament to assist in minimising the risk of damaging said medial ligament. In other words, the second incision (89) is approximately 2 - 3 cm cranial and approximately 2 -3 cm caudal along the anterior border of the medial collateral ligament.

Once the knee joint (9) is sufficiently accessible, the surgeon palpates the epicondylar axis (32) of the lower femur (33) as shown in figure 25. This axis provides a reference axis for many of the following surgical steps. Alternative reference axes include the posterior condylar axis (34) and/or the longitudinal axis (35) of the tibia (36).

As shown in figures 26 and 61, once the patient's leg is fully extended the surgeon applies a frame (37) such that first and second ends (38 and 39) of first and second amis (40 and 41) are positioned along the epicondylar axis (32). Each of the arms (40 and 41) are threadedly engaged with the body of the frame (37), allowing the arms to be tightened onto the lower femur, thereby positioning the frame (37) such that the arms (40 and 41) are directed along the epicondylar axis (32). Thus the arms (40 and 41) function as attachment means to releasably attach the frame (37) to a predefined point on the knee joint. The arms (40 and 41) are hollow to allow the surgeon to pass a first guide wire (43) there through. As shown in figures 27 and 28, the guide wire (43) is passed through the lower femur (33) along the epicondylar axis (32).

The frame (37) is then rotated if necessary to ensure that the distal member (42) is parallel to the longitudinal axis of the patient's leg. Alternatively, assuming the patient's leg extends along a flat operating table, the surgeon may choose to use the operating table or the floor of the operating room as a reference axis against which to judge that the distal member (42) of the frame (37) is parallel. In this position a second guide wire

(44) is passed through an aperture (45) in the frame (37) and into the lower femur (33).

The second guide wire (44) is parallel to, and spaced apart from, the first guide wire (43). In this way the orientation and position of the frame (37) are affixed relative to the femur (8), as shown in figure 30.

A femoral jig (46) is applied to the frame (37) from the medial side of the knee joint (9) by threading the ends of the first and second guide wires (43) and (44) through apertures in the femoral jig (46) then displacing the femoral jig toward the knee joint such that it abuts an outer edge of the frame (37). In other words, the first and second guide wires (43) and (44) act as jig receiving means disposed on the body of the frame. Three soft tissue guides (47, 48 and 49) are then inserted through three further apertures (70, 71 and 72) defined by the femoral jig (46). The soft tissue guides (47, 48 and 49) are hollow cylinders having a lugs (50, 51 and 52) at one distal end each. One of the functions performed by the soft tissue guides is to assist in keeping soft tissue spaced from the knee joint (9) during surgery. Another function performed by the soft tissue guides is to guide coring tools (53) which are inserted into the hollow soft tissue guides. The interior diameter of the hollow soft tissue guides (47, 48 and 49) is sized so as to match the exterior diameter of the coring tools (50). Hence, once inserted into the soft tissue guides (47, 48 and 49), the coring tools (50) are oriented and positioned accurately relative to the femur (8). Thus the apertures (70, 71 and 72), in conjunction with the soft tissue guides (47, 48 and 49) function as surgical tool guidance means so as to direct surgical tools such as coring tools towards predefined sites on the knee joint. The coring tools (53, 64 and 65) are parallel to the epicondylar axis (32) and are spaced around the periphery of the femoral condyle when viewed from the medial side. They are also positioned so as to minor the disposition of the projections (2, 3 and 4) of the femoral prosthetic component (1).

The coring tools (53) are used to bore three cylindrical apertures (54, 55 and 56) into the lower femur (33). The cylindrical rods of bone (13, 14 and 15) which are extracted from the lower femur (33) by the coring tools (53) are kept aside by the surgeon for later use. Third and fourth guide wires (60 and 61) are inserted through apertures (62 and 63) in the femoral jig (46) and into the femoral condyle. The planes along which the osteotomy of the femoral condyle is performed are defined by the outer edges of the guide wires (43, 44, 60 and 61) and the three coring tools (53) relative to the epicondylar axis (32). hi other words, with reference to figure 37, a first resection plane is defined by the top of the second guide wire (44) and the top of the first coring tool (53). The second resection plane is defined by the top of the first coring tool (53) and an outer edge of the second coring tool (64). The third resection plane is defined by an outer edge of the second coring tool (64) and an outer edge of the third coring tool (65). The fourth resection plane is defined by an outer edge of the third coring tool (65) and an outer edge of the third guide wire (60). The final femoral resection plane is defined by the lower edge of the third guide wire (60) and the lower edge of the fourth guide wire (61). These planes are shown by the heavy line referenced (66) on figures 39 and 40. The cutting tool used to resect the lower femur (33) is guided by the various guide wires and/or coring tools. Once resected, the cylindrical apertures (54, 55 and 56) are each open along an outer edge and are now refened to as recesses (54, 55 and 56). Each of the recesses defines a slot along the intersection of the resections planes with the cylindrical apertures.

The next step is to perform an osteotomy on the upper tibia (67). A further guide wire (68) is passed through the upper tibia (67) and through the frame (37). The femoral jig (46) is removed and replaced with a tibial jig (69) as best shown in figure 62. The tibial jig (69) is aligned by the first guide wire (43) and the further guide wire (68) so as to conectly position two apertures (70 and 71) relative to the tibia. These apertures (70 and 71) define the directions and positions for coring of the upper tibia (67). The surgeon may choose to prepare the upper tibia for coring and osteotomy with the patient's leg either fully extended as shown in figure 64 or with the knee joint flexed by 90°, as shown in figure 65, although variations to the tibial jig (69) are likely to be required when operating on these different leg configurations.

The coring of the upper tibia (67) results in two cylindrical apertures (72 and 73) in the upper tibia (67). The upper edges of these two cylindrical apertures define the plane for resection of the upper tibia (67). Once again, the coring tools are allowed to remain in the cylindrical apertures (72 and 73) so as to guide the cutting tool for resection of the upper tibia (69). This osteotomy turns the cylindrical apertures in the upper tibia (67) into recesses (72 and 73) open along an upper edge, as shown in figure 68.

The surgeon now attaches the femoral and tibial prosthetic components onto the resected bones. As best shown in figure 47, the femoral prosthetic component (1) slides onto the lower femur (33) starting from the medial side of the knee joint. The surgeon aligns the three projections (2, 3 and 4) with the three recesses (54, 55 and 56). The prosthetic component (1) is then displaced transverse to the longitudinal axis of the femur onto the end of the lower femur (33) adjacent the knee joint (9). The rods of bone (13, 14 and 15) which were previously extracted from the lower femur (33) are now placed into the hollow projections (2, 3 and 4) as best shown in figure 48. The rods of bone (13, 14 and 15) are impacted into position. Inserting the rods (13, 14 and 15) advantageously allows the femoral bone (8) to grow through the apertures 16 in the projections (2, 3 and 4) and to meld with the rods of bone (13, 14 and 15).

The projections (21 and 22) of the tibial component are then aligned with the recesses in the upper tibia (67) and the tibial prosthetic component (19) is slid onto the upper tibia (67) in a similar manner to that described above in relation to the sliding of the femoral prosthetic component (1) onto the lower femur (33). Once again, the rods of bone (74 and 75) which were extracted when coring the upper tibia are placed into the hollow projections (21 and 22) of the tibial prosthetic component (19).

The keying of the prosthetic components (1 and 19) into the ends of the bones (33 and 67) advantageously provides for early mechanical fixation. Additionally, over time the prosthetic achieves bony biological fixation as the bone grows through the apertures (16). In some prefened embodiments of the invention the prosthetic components (1, 19 and 79) are cemented into position, however in other prefened embodiments no such cement is utilised.

A spacer (26) is inserted intermediate the femoral prosthetic component and the tibial prosthetic component in accordance with known knee replacements principles. The spacer (26) is inserted from the medial side of the knee joint. In one prefened embodiment the spacer (26) is rigidly affixed to the tibial component (19). In yet other embodiments it is integral with the tibial component (19). Yet further embodiments provide for rotating spacers (26) as known in the prior art. The knee joint (9) is now replaced as shown in figures 49 to 54.

In some circumstances the surgeon may elect to place trial components onto the resected femur and tibial and to briefly assemble the knee joint with the trial components in order to check range of motion and joint stability. If the trial knee joint is considered satisfactory, the trial components are replaced with the actual prosthetic components. Alternatively, other trial components are tried until a suitable solution is found.

If the patella (76) also requires replacing the prefened embodiment includes a third jig attachable to the frame (37) so as to position coring tools to bore two cylindrical apertures (77 and 78) into the patella (76). The patella is then resected as shown in figure 55, thereby defining a slot along the intersection of the resection plane and the cylindrical apertures (77 and 78). hi this way, the cylindrical apertures are transformed into recesses (77 and 78). The patella prosthetic component (79) includes two projections (80 and 81) which slidably mate with the two recesses (77 and 78). Once again, the patella prosthetic component is slid onto the patella from the medial side of the knee joint (9). Typically the arcuate face (92) of the prosthetic patella component (79) is installed so as to mate with the trochlear groove 91 provided in the femoral prosthetic component (1).

As shown in figure 57, prefened embodiments of the present invention are also suited to uni knee replacement surgery. It is preferable to ensure that the recesses (82 and 83) used to affix the uni femoral prosthetic component (84) to the femoral condyle (85) for a uni operation can be extended to accommodate the larger femoral prosthetic component (1) if it subsequently becomes necessary to perform a total knee replacement on the patient's knee, as shown in figure 58. Similarly, the recesses (86 and 87) used to affix the uni tibial prosthetic component (88) to the femoral condyle (85) may be extended to accommodate the large tibial prosthetic component (19) if subsequently necessitated. This allows a uni knee replacement to be readily upgraded into a full knee replacement.

In some prefened embodiments surgeons may choose to utilise known computerised navigation systems for additional guidance in relation to positioning of surgical tools, however such systems are not essential to this invention. Advantageously, the use of a single frame (37) having a fixed position relative to the knee joint to align coring and resection of both the lower femur (33) and the upper tibia (67) (and the patella if necessary) helps the surgeon to ensure that the resulting replaced knee joint has the conect soft tissue tension. This is because the separation distance between the osteotomy cuts is accurately controlled by the combination of a frame (37) and the jigs (19 and 46) used in the prefened embodiment of the present invention. This compares well to the prior art methods which typically perform the osteotomies of the femur and tibia separately, then attempt to obtain an acceptable balance of soft tissue tension.

A cross-section of part of an alternative embodiment of the invention is illustrated in figure 75. In this embodiment the prosthetic component (l lO)is fastenable to a bone (111), for example a femur or tibia. The bone (111) has an elongate dimension (which is oriented vertically as shown in figure 75). The prosthetic component (110) includes a formation in the form of channels (112) for slidable engagment with a conesponding formation in the form of fins (113) provided upon the bone (111). The cross sectional shapes of the fins (113) and the channels (112) are substantially constant extending in a direction transverse to the elongate dimension (which is into or out of the page as shown in figure 75). The slidable interengagement of the prosthetic component (110) and the bone (111) takes place in the direction transverse to the elongate dimension. The geometries of the fins (113) and channels (112) requires slidable inter-engagement of the prosthetic component (110) with the bone (111) to take place in the aforesaid direction transverse to the elongate dimension. More particularly, the aforesaid direction extends between a medial side of the knee and a lateral side of the knee. In this embodiment the fins (113) and channels (112) of such an embodiment do not key into each other, although an interference fit may optionally be employed.

In an alternative prefened embodiment (not illustrated) the fins are provided upon the prosthetic component and the channels are provided upon the bone.

With reference to the alternative embodiment of the invention illustrated in figures 69 to 74, the surgical procedure is as follows:

Step One (tibial osteotomy) Place arthroscope in lateral compartment.

Plan incision by placing upper tibial jig (TIB) connected to IM rod. Level of cut Determined by level of medial joint space. Pin TIB. Make incision (one cm), postero-medial upper tibia/tibio-femoral joint space. Perform osteotomy under vision. Osteotomise upper tibia and protect PCL.

Step Two (posterior femoral osteotomy)

Flex knee to 90 degrees (measure; ?lock IM rod in femur to IM rod in tibia). Use same incision. Create flexion gap.

Attach first (posterior) femoral cutting block (FEM l)to tibial jig. Create flexion gap with osteotomy of posterior femur.(cuts UP)

Step Three (anterior femoral osteotomy)

Plan second incision over medial patella-femoral interval. Attach second (anterior) femoral cutting block (FEM 2) to osteotomise anterior femur. Mark incision over medial patella-femoral interval. Make second (one-cm) incision (cuts UP). Perform anterior femoral osteotomy.

Step Four (lower femoral osteotomy)

Extend knee (and confirm by measurement). Use first incision. Create extension gap Use the first femoral cutting block (FEM l)attached to the tibial jig.

Create extension gap with osteotomy of the lower end of the femur (cuts UP).

Step Five (patella osteotomy) Use second incision

Attach patella-cutting block (PAT) to first femoral cutting block (FEM 1).

Push patella over anterior femur.

Osteotomise patella, (cuts UP)

Step Six ( component placement)

Connect incisions one and two. Place trial components and then final components. Need to 'over cut' femoral side

Need to slide plastic spacer in medially

Need to place tibial stem medially as separate tibial component ( ?as large screw along with two smaller screws).

Advantages provided by some prefened embodiments of the present invention include:

• a smaller more cosmetic scar hidden medially;

• the incision is anatomical and placed far from the tibial tubercle with a reduced chance of wound healing problems;

• the extensor mechanism is not disturbed (patella is NOT dislocated); • reduced blood loss;

• less risk of infection;

• more precise placement of the components;

• rapid mechanical fixation with no requirement for cement;

• earlier long-term bony incorporation and fixation; • reduced risk of expelling fatty material from inside the bone into the circulatory system;

• 'impact dispersal' to reduce impact/shear forces across the articular surfaces and so improve fixation and reduce long term wear and premature aseptic loosening of the components.

Whilst the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. For example, the prosthetic is applicable to fields other than knee replacement surgery, for example hip, ankle, shoulder, elbow, etc.

Claims

Claims:

I. A prosthetic component fastenable to a bone, said prosthetic component including a formation for slidable engagment with a conesponding formation provided upon said bone such that said prosthetic component is keyed into said bone.

2. A prosthetic component according to claim 1 wherein said formation interference fittingly engages said conesponding formation.

3. A prosthetic component according to claim 1 or 2 wherein said formation is a projection disposed on said prosthetic component, said projection defining an elongate dimension.

4. A prosthetic component according to any one of the preceding claims wherein said conesponding formation is a recess defined within said bone.

5. A prosthetic component according to claim 3 wherein said projection has a substantially constant cross sectional shape along said elongate dimension.

6. A prosthetic component according to claim 4 wherein said recess defined within said bone has a substantially constant cross sectional shape.

7. A prosthetic component according to claim 5 wherein said cross sectional shape of said projection is substantially circular.

8. A prosthetic component according to claim 6 wherein said substantially constant cross sectional shape of said at least one recess is substantially circular.

9. A prosthetic component according to claim 3 wherein said prosthetic component includes a plurality of projections each having parallel elongate dimensions.

10. A prosthetic component according to claim 9 wherein said conesponding formation is a plurality of parallel recesses defined within said bone.

I I. A prosthetic component according to claim 7 wherein said projection is hollow.

12. A prosthetic component according to claim 11 wherein said hollow projection defines a housing for bone in the form of a cylindrical rod.

13. A prosthetic component according to claim 11 or 12 wherein said projection includes a plurality of apertures to allow bone growth through said apertures.

14. A prosthetic component according to any one of the preceding claims wherein said formations are resilientiy deformable so as to provide shock absorption intermediate the prosthetic and the bone.

15. A method of attaching a prosthetic component to a bone of a patient, said method including the steps of:

providing a prosthetic component having one or more elongate projections;

boring one or more recesses into said bone; and

slidably engaging said one or more projections with said one or more recesses so as to key said prosthetic component into said bone.

16. A method of performing knee replacement surgery to a knee joint of a patient, said method including the steps of:

providing a prosthetic component having one or more projections;

surgically accessing the knee joint from either a medial side or a lateral side of the knee joint;

boring one or more recesses into a bone adjacent said knee joint; and

slidably engaging said one or more projections with said one or more recesses so as to key the prosthetic component into said bone.

17. A frame for application to a knee joint during knee replacement surgery, said frame including:

a frame body;

attachment means disposed on said body for releasably securing the frame to a predefined point on said knee joint; and jig receiving means disposed on said body and adapted to secure one or more jigs onto said frame, each of said jigs including surgical tool guidance means adapted to direct surgical tools towards predefined sites on said knee joint.

18. A frame according to claim 17 wherein said body includes first and second members adapted for respective disposition adj acent first and second sides of said knee joint.

19. A frame according to claim 18 wherein said first side is a medial side of said knee joint.

20. A frame according to claim 18 or 19 wherein said second side is a lateral side of said knee joint.

21. A frame according to any one of claims 17 to 20 wherein said attachment means includes at least one arm adapted for disposition along an epicondylar axis of said knee joint.

22. A frame according to claim 21 wherein said at least one arm is adapted for clamping engagement with a lower femur adjacent said knee joint.

23. A frame according to claim 22 wherein said at least one arm is threadedly engagable with said body such that screwing of said at least one arm displaces said at least one arm towards said lower femur so as to provide said clamping engagement.

24. A frame according to any one of claims 21 to 23 wherein said at least one arm is hollow so as to allow for passage of a first guide wire through said arm and into said femur to further attach the frame to said knee joint.

25. A frame according to claim 24 further including one or more apertures allowing for passage of a second guide wire through said apertures and into said femur to further attach the frame to said knee joint.

26. A frame according to claim 25 wherein, in use, the first guide wire is parallel to, and spaced apart from, the second guide wire.

27. A frame according to any one of claims 17 to 26 wherein said one or more jigs include hollow cylinders having an outer surface for guiding soft tissue adjacent said knee joint and an inner surface adapted to guide one or more coring tools.

28. A frame according to claim 27 wherein said internal surface of said hollow cylinder has a diameter sized so as to match an exterior diameter of said coring tool so as to orient and position the coring tool relative to predefined sites on the knee joint.

29. A frame according to claim 27 or 28 wherein, whilst guided by the hollow cylinders, the coring tools are parallel to the epicondylar axis and positioned so as to minor a disposition of projections on a compatible prosthetic component.

30. A frame according to claim 25 further including apertures allowing for passage of a third guide wire through said apertures and into said femur.

31. A frame according to claim 30 further including apertures allowing for passage of a fourth guide wire through said apertures and into said femur.

32. A frame according to claim 31 wherein outer edges of the guide wires and the coring tools define resection planes for osteotomy of a femoral condyle of the knee joint.

33. A frame according to any one of claims 17 to 21, further including tibial jigs for the positioning and guiding of coring tools for coring of the tibia.

34. A frame according to any one of claims 17 to 21, further including tibial jigs for the guidance of osteotomy of the tibia.

35. A prosthetic component for knee replacement surgery, said prosthetic component being fastenable to a bone having an elongate dimension, said prosthetic component including a formation for slidable engagment with a conesponding formation provided upon said bone, said slidable engagement taking place in a direction transverse to said elongate dimension.

36. A prosthetic component according to claim 35 wherein said formation has a substantially constant cross sectional shape extending in said direction transverse to said elongate dimension.

37. A prosthetic component according to claim 36 wherein said conesponding formation has a substantially constant cross sectional shape extending in said direction transverse to said elongate dimension.

38. A prosthetic component according to claim 35 or 36 wherein said formation is a plurality of parallel fins extending in said direction transverse to said elongate dimension.

39. A prosthetic component according to claim 35 or 37 wherein said conesponding formation is a plurality of parallel channels extending in said direction transverse to said elongate dimension.

40. A prosthetic component according to claim 35 or 36 wherein said formation is a plurality of parallel channels extending in said direction transverse to said elongate dimension.

41. A prosthetic component according to claim 35 or 37 wherein said conesponding formation is a plurality of parallel fins extending in said direction transverse to said elongate dimension.

42. A prosthetic components according to any one of claims 35 to 41 wherein said direction transverse to said elongate dimension extends between a medial side of the knee and a lateral side of the knee.