GB2398011A

GB2398011A - Alignment device for use in orthapaedic surgery

Info

Publication number: GB2398011A
Application number: GB0302533A
Authority: GB
Inventors: Robert Michael Wozencroft; Raymond Randle
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-02-04
Filing date: 2003-02-04
Publication date: 2004-08-11
Also published as: GB0302533D0

Abstract

An alignment device for use in the course of orthopaedic surgery on a patient knee, comprising an elongate first member for attachment to a lower leg or a patient below the knee, an elongate second member pivotally attached adjacent the first elongate member allowing pivotal movement in an anterior-posterior plane, further having locking means for locking the elongate second member at an angle relative to the first elongate member. Also disclosed are a tibia area guide, a surgical tool for implantation of a knee prosthesis, a tibial area guide insertion tool, a femur jig having a medial fin for receipt in an anterior-posterior slot cut in the femur, a femur jig having a slot for receiving a saw blade, a femur jig insertion tool, a femoral implant insertion tool, a tibial implant insertion tool and a method of surgery.

Description

239801 1

SURGICAL APPARATUS

FIELD OF THE INVENTION

This invention relates to surgical apparatus, more particularly to surgical apparatus for use in orthopaedic surgery on a patient's knee. Also described herein is a method for the use of such apparatus.

BACKGROUND TO THE INVENTION

The human knee is a complex joint. It is formed between the femur in the upper leg and the tibia which is the major long bone of the lower leg. The lower end of the femur is provided with a pair of condyles and the tibia has at its upper end a layer of cartilage which provide a lateral meniscus and a medial meniscus to receive the lateral condyle and the medial condyle respectively. Four separate ligaments stabilise the knee joint. On the sides of the joint lie the medial collateral ligament and the lateral collateral ligament which serve as stabilisers for side-toside stability of the joint. The medial collateral ligament is a broader ligament that is actual made up of two ligament structures, the deep and superficial components, whereas the lateral collateral ligament is a distinct cord- like structure. In the front part of the centre of the joint is an anterior cruciate ligament. This ligament is a very important stabiliser of the femur or the tibia and serves to prevent the tibia from rotating and sliding forward during agility, jumping and deceleration activities.

Directly behind the anterior cruciate ligament is its opposite, the posterior cruciate ligament. At the front of the knee the patella bears against the lower end of the femur and is connected to the patella tendon which is connected at its opposite end to the tibia.

The knee is subject to a great deal of stress during normal activity and is readily damaged, for example, as a 2 F037 result of sporting activities. It is also prone to generative disease.

In many patients with knee problems, a potential solution is to implant a knee prosthesis. This may be a complete prosthesis involving resection of the upper end of the tibia and implantation of an implant having menisci formed of a plastics material, such as high molecular weight polyethylene. In addition the lower end of the femur may be resected and a metal femoral prosthesis implanted to replace the natural condyles. It is, however, a disadvantage of such a surgical operation that both the anterior and posterior cruciate ligaments have to be sacrificed.

In an alternative surgical technique, the anterior and posterior cruciate ligaments are retained, in which case one or both menisci can be replaced with a corresponding individual tibial component, again with a plastics material meniscus. In this case the corresponding condyle may also be replaced by a metal prosthesis. Such a prosthesis is often termed a unicompartmental knee prosthesis.

Current surgical techniques are invasive and require considerable dissection in order to expose the surfaces of the bones to be replaced.

Many knee problems can be investigated and treated without the need for extensive orthopaedic surgery. One such technique is arthroscopy which is frequently used in the treatment of sports injuries in which, for example, damage has occurred to the knee cartilage. According to this procedure the surgeon makes small incisions or portals one of which is used for insertion of an endoscope through which a surgeon can observe the progress of the operation using a surgical tool inserted through another portal.

It would be desirable to develop surgical apparatus which would enable a surgeon to perform a knee prosthesis l 3 F037 implantation operation in the course of which the size of the surgical incision is minimised so as to minimise the trauma experienced by the patient and to hasten the rehabilitation process following the operation. It would further be desirable to provide surgical apparatus which enables the surgeon to use procedures for effecting implantation of a unicompartmental knee prosthesis in a patient's knee which utilise small incisions, preferably of no more than about l inch (2.54 cm) in length, to provide access for the surgeon to the bone surfaces to be resected and to permit the surgeon to effect resection and to implant the prosthesis. It would further be desirable to develop novel surgical apparatus enabling a surgeon to carry out with minimally invasive techniques a knee prosthesis implantation operation, more particularly an operation to implant a unicompartmental knee prosthesis.

BRIEF SUMMARY OF THE INVENTION

The present invention accordingly seeks to provide novel surgical apparatus enabling a surgeon to perform a knee prosthesis implantation operation in the course of which the size of the surgical incision is minimised so as to minimise the trauma experienced by the patient and to hasten the rehabilitation process following the operation.

It further seeks to provide surgical apparatus which enables the surgeon to use procedures for effecting implantation of a unicompartmental knee prosthesis in a patient's knee which utilise small incisions, preferably of no more than about l inch (2.54 cm) in length, to provide access for the surgeon to the bone surfaces to be resected and to permit the surgeon to effect resection and to implant the prosthesis.

The invention further seeks to provide novel surgical apparatus enabling a surgeon to carry out with minimally invasive techniques a knee prosthesis implantation 1 t 4 F037 operation, more particularly an operation to implant a unicompartmental knee prosthesis.

According to a first aspect of the present invention there is provided an alignment device for use in the course of orthopaedic surgery on the knee of a patient comprising: an elongate first member for temporary attachment to a lower leg of a patient below a knee requiring orthopaedic surgery, the elongate member having a lower end and an upper end; an elongate second member having a first end with an axial bore therein and a second end, the elongate second I member being pivotally attached adjacent its first end to the first elongate member adjacent to the upper end thereof for pivotal movement substantially in an anterior-posterior planes locking means for locking the elongate second member at a selected angle relative to the first elongate member.

Conveniently the locking means comprises an arcuate arm mounted on the first elongate member and a locking member for locking the elongate second member to the arcuate arm.

The arcuate arm may be provided with a transverse slot while I the locking member comprises a locking knob having a threaded shank that extends though the transverse slot and is threadedly received in a corresponding threaded transverse bore formed in the elongate second member adjacent the second end thereof. In addition, the arcuate arm may be provided with a longitudinal slot in which the elongate second member moves. Preferably the arcuate arm is provided with a graduated scale.

It is preferred that the first elongate member is extensible. I In the alignment device of the invention the first elongate member preferably has a notch at each end to permit t F037 the axis of the first elongate member to be aligned with respect to markings on the patient's skin so as to align the axial bore of the second elongate member with the weight bearing axis of the patient's tibia. Such markings can be made with the aid of a calibration device as described in our copending British Patent Application No. (Case 503615 - F036) filed simultaneously herewith, the entire disclosure of which is herein incorporated by reference.

In a preferred alignment device according to the invention at least one aperture is provided adjacent the upper end of the first elongate member for passage of a pin or screw for temporary attachment of the device to a patient's tibia. The alignment device may further include means mounted adjacent the lower end of the first elongate member for embracing the patient's leg and securing the lower end of the device to the outside of the patient's leg.

In a second aspect of the present invention there is provided a surgical implement for use in resection of an upper surface of a patient's tibia during a surgical operation to implant a unicompartmental knee prosthesis in the patient's knee comprising; an alignment device according to the first aspect of the invention; a support table mounted at an upper end of a shaft and orthogonal to its axis, the shaft being received in the axial bore of the second elongate member; and a cutting block mounted on the support table provided with at least one slot extending substantially in a plane parallel to the axis of the shaft for passage of a surgical saw for effecting a vertical cut in a patient's tibia during resection thereof and a transverse slot extending substantially orthogonal to the axis of the shaft for making 6 F037 a transverse cut in a patient's tibia at an angle determined by the selected angle.

In such a surgical implement the cutting block can be mounted on the table so as to be pivotable about an axis orthogonal to the upper surface of the table.

The cutting block may be removable from the table. In addition the table may be provided with a bore to receive a pin or screw for temporarily securing the table to a patient's tibia during the surgical implantation operation.

The surgical implement preferably further includes a stylus mounted on the cutting block having a tip positioned at a selected height above the transverse slot of the cutting block for determining the position of the top of the tibia of the patient prior to effecting the transverse cut during resection of the tibia. Additionally the cutting block may be provided with at least one bore for receipt of a pin or screw to permit temporary attachment of the cutting block to the tibia of the patient.

In a third aspect of the invention there is contemplated a tibia area guide for use in the surgical implantation of a unicompartmental knee prosthesis in a knee of a patient comprising a member adapted to be received on an upper end of a surgically resected tibia of the patient and having a dovetail section groove in an upper surface thereof for receipt of a saw guide for use in cutting a groove in a condyle of the patient's femur. In such a tibia area guide the undersurface of the member may be roughened to prevent slippage of the tibia area guide on the upper surface of the resected tibia during cutting of the slot in the condyle.

According to a fourth aspect of the invention there is provided a surgical tool for use in the surgical implantation of a unicompartmental knee prosthesis in a knee 7 F037 of a patient comprising a first end, a second end, and means connecting the first and second ends, the first end comprising a block formed with a saw guide slot in an upper side thereof for receipt of a saw blade for cutting an S anterior-posterior slot in a condyle of the patient's femur, and a tongue member which extends forwardly of the block having a groove in an upper surface thereof aligned with the saw guide slot and which has a dovetail section for receipt in a corresponding dovetail section groove in an upper surface of a tibia area guide so that the saw guide slot and the groove in the tongue member face upwardly. Preferably the saw guide slot and the groove in the tongue member both widen in the forward direction of the tool. In such a surgical tool it is preferred that the second end has a predetermined thickness less than that of a corresponding tibial implant.

A fifth aspect of the invention is concerned with a tibial area guide insertion tool comprising; an elongate body having a groove in an upper side thereof, a forward portion having a dovetail section for receipt in a corresponding dovetail section groove in a tibia area guide, and an inclined front ends an operating lever pivotally mounted adjacent a rear end of the elongate body for pivotal movement between a forward open position and a rearward closed position; and an operating rod adapted to be received in the groove in the elongate body and pivotally attached at a rearward end thereof to the operating lever, the operating rod having at a forward end thereof a pair of aligned transverse projections for cooperation with the inclined front end of the elongate body and a pressure portion on its underside; whereby upon inserting the dovetail section of the elongate body in a corresponding dovetail section of a tibia 8 F037 area guide and pivoting the operating lever to its rearward closed position the operating rod may be drawn rearwardly along the groove so as to cause the transverse projections to move down the inclined front end and press the pressure portion against the tibia area guide to hold the tibia area guide firmly on the tool.

In a sixth aspect the invention provides a femur jig for use in surgical preparation of a femur of a patient in readiness for implantation of a femoral implant comprising: a web portion including a forward portion for insertion in a surgically prepared slot in a condyle of the femur of the patient and having on a rearward portion thereof means for facilitating gripping by a femur jig insertion tool.

A preferred femur jig further comprises: a body portion including means for cooperation with a surgical tool.

In a first form of such a femur jig the web portion extends downwardly and forwardly from the body portion and the body portion is provided with a bore whose axis lies substantially in the plane of the web portion, the bore being adapted to act as a guide for a drill for drilling a first hole in the femur of the patient for receipt of a posterior peg of a femoral implant.

In another preferred femur jig the web portion extends downwardly and forwardly from the body portion, and a rod portion is integrally formed with the web portion and has an axis which lies substantially in the plane of the web portion, the rod portion being adapted for insertion in a first hole drilled in the femur of a patient intended for eventual receipt of a posterior peg of a femoral implant, the body portion being provided with a bore whose axis lies substantially in the plane of the web portion, the bore having an axis substantially parallel to that of the rod 9 F037 portion and being adapted to act as a guide for a drill for drilling a second hole in the femur of the patient for receipt of an anterior peg of a femoral implant.

In yet another preferred form of femur jig according to the invention the web portion is integrally formed with posterior and anterior rod portions whose axes are substantially parallel to one another and are adapted for insertion in corresponding posterior and anterior holes drilled in a femur of a patient intended for eventual receipt of posterior and anterior pegs respectively of a femoral implant, and the web portion is adapted so that, after insertion in the surgically prepared slot in the condyle to a depth corresponding to the depth to which the medial fin of the femoral implant will eventually be implanted, it extends from the slot to a rearward edge which is shaped so as to extend substantially parallel to the corresponding locus of the bearing surface after eventual implantation of the femoral implant, the rearward edge being adapted to serve as a template for a surgical burr for resection of bone of the condyle in readiness for insertion of the femoral implant.

In yet another form of femur jig according to the invention the web portion is integrally formed with a rod portion which has an axis that lies substantially in the plane of the fin means for insertion in a first hole drilled in the femur intended for eventual insertion of a posterior peg of a femoral implant, and the body portion comprises a flange integrally formed with a lower part of the web portion and having a transverse surface substantially orthogonal to the plane of the web portion for guiding a saw blade during making a posterior cut in the femur of a patient.

According to a seventh aspect of the present invention 1 1 F037 there is provided a femur jig for use in surgical preparation of a femur of a patient in readiness for implantation of a femoral implant comprising: a body portion having on a rearward side thereof a projecting web portion provided with means for facilitating gripping by a femur jig insertion tool and provided with a pair of substantially parallel forwardly projecting rod portions for insertion in respective posterior and anterior holes drilled in a condyle of the femur of the patient for eventual reception of posterior and anterior pegs of a femoral implant, the body portion being further provided with a slot extending from a rear face to a forward face thereof extending from top to bottom of the body portion for receipt of a saw blade for extending a surgically prepared slot in the condyle that extends from behind the posterior hole at least as far as the anterior hole.

An eighth aspect of the invention provides a femur jig insertion tool for insertion into a surgically prepared slot in a condyle of a femur of a patient comprising: an elongate tool body having (i) a channel in an upper surface thereof defined by side walls, (ii) a jig-receiving slot at its forward end for receipt of a web portion of a femur jig, the web portion having an indentation therein, and (iii) a lateral slot in each side wall of the channel having an open upper end and a rear surface that is inclined downwardly towards the rear of the channel; an operating rod having a shaped forward end adapted for reception in the indentation in the web portion of the femur jig and a lateral projection on each side of the operating rod for reception in a lateral slot; and operating lever means pivotally mounted on a rearward end of the tool body for drawing the operating rod rearwardly along the channel so as to cause the projections F037 to move downwardly and rearwardly as they follow the inclined surfaces of the slots, thereby to cause the shaped forward end to enter the indentation and grip the web portion of a femur jig in the jig-receiving slot.

A ninth aspect of the invention provides a femoral implant insertion tool comprising) a body having a forward end, a rearward end, an axis extending between the forward and rearward ends, and an internally threaded axial bore; a pair of jaw members each pivotally mounted on the body adjacent the rearward end thereof, having a jaw at a forward end thereof extending inward over a forward end face of the body, and having a ramp surface extending rearward of the bodyi a handle threadedly engaged in the threaded bored and a collar on the handle adapted for engagement with the ramp surfaces on the jaw members as the handle is screwed into the body so as to cause the jaw members to pivot inwardly towards the body and the jaws to move inwardly over the front face of the body; whereby, upon placing a bearing surface of a unicompartmental femoral implant against the front surface with the jaws retracted and rotating the handle so as to cause the jaw members to pivot inwardly, the unicompartmental femoral component may be gripped firmly during implantation into a surgically prepared condyle of a femur of a patient.

A tenth aspect of the invention is concerned with a tibial implant insertion tool comprising) a body having a front end, a rear end, an axis extending between the front and rear ends, and an axial internally threaded bore; a ledge at its front end; 12 F037 a gripping arm pivotally mounted to the body adjacent the rear end of the body and having a forward end provided with a pressure pad and a ramp surface extending rearwardly of the body; a handle threadedly engaged in the bore in the body; and a collar mounted on the handle and adapted to bear on the ramp surface on the gripping arm as the handle is screwed into the body so as to cause the gripping arm to pivot inwardly towards the body and the pressure pad to move towards the ledge; whereby, upon placing a metal plate of a unicompartmental tibial implant against the ledge with the gripping arm retracted and rotating the handle so as to cause the gripping arm to pivot inwardly towards the body and the pressure pad to contact a meniscus of the unicompartmental tibia implant, the unicompartmental tibial component may be gripped firmly during implantation onto a surgically resected upper surface of the patient's tibia.

The invention further relates to a surgical kit comprising a combination of two or more of the following: (i) an alignment device as defined above; (ii) a surgical implement as defined above; (iii) a tibia area guide as defined above; (iv) a surgical tool as defined above) (v) a tibial area guide insertion tool as defined above; (vi) a femur jig as defined above) (vii) a femur jig insertion tool as defined above; (viii) a femoral implant insertion tool as defined above) (ix) a tibial implant insertion tool as defined above.

Also described herein is a method of effecting implantation in a knee of a patient of a unicompartmental 13 F037 knee prosthesis comprising (i) a tibial implant comprising a metal backing plate and a meniscus of a biocompatible plastics material and (ii) a femoral implant having a polished front bearing surface for bearing on the meniscus, an anterior peg and a posterior peg on its rear side for receipt in surgically prepared holes in a femur of a patient, and a fin on the rear side in alignment with the anterior and posterior pegs, the method comprising the steps of: resecting an upper end portion of the tibia of the patient to provide a bearing surface for the metal plate of the tibial implant; cutting an anterior-posterior slot in a condyle of the femur of the patient in readiness for receipt of a posterior part of the fin of the femoral component; drilling a first hole in the condyle with its axis substantially in alignment with the plane of the slot in readiness for receipt of the posterior peg of the femoral component; drilling a second hole in the condyle with its axis extending substantially parallel to the axis of the first hole and in alignment with the plane of the slot in readiness for receipt of the anterior peg of the femoral component; extending the slot in the anterior direction through the second hole in readiness for receipt of an anterior part of the fin of the femoral component; resecting sufficient bone of the condyle adjacent each side of the slot to provide a bearing surface for an anterior part of the rear side of the femoral component) and making a posterior cut in the condyle to provide a bearing surface for a posterior part of the rear side of the femoral component. 1 1

14 F037

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be clearly understood and readily carried into effect, some preferred embodiments thereof will now be described, by way of example only, with reference to the accompanying diagrammatic drawings wherein: Fig. l is a front view of a first calibration device which is useful in the practice of the invention; Fig. 2 is a perspective view of the device to Fig. l illustrating its method of preparation for application to a patient's lower leg; Fig. 3 is a perspective view of two of the calibration devices of Figs. l and 2 in place on the lower left leg of a patient; Fig. 4 shows an anterior posterior (AP) X-ray picture of a patient's foot and lower left leg after two of the calibration devices of Figs. l and 2 have been applied to the lower left leg in the manner illustrated in Fig. 3; Figs. 5 and 6 are enlarged views of upper and lower portions respectively of the X-ray picture of Fig. 4; Fig. 7 is a further media lateral (ML) X-ray picture of the patient's lower leg corresponding to the anterior posterior (AP) X-ray picture of Fig. 4; Figs. 8 and 9 are enlarged views of an upper portion and a lower portion respectively of the X-ray picture of Fig. 7; Fig. lo is a perspective view of an alignment device for use in the course of orthopaedic surgery on a patient's knee; Fig. It shows the alignment device of Fig. lo temporarily attached to the front of the patient's leg; Figs. 12 and 13 are enlarged views of an upper portion and a lower portion respectively of Fig. ll; Fig. 14 is a side view of the patient's left leg F037 showing the use of the alignment device of Figs. 10 to 13 in somewhat extended condition to determine the position of the top surface of the patient's tibia in preparation for resection thereof; Fig. 15 is a front view of the patient's knee after the preliminary cuts have been made in the tibia as part of resection; Fig. 16 is a front view of part of a second calibration device useful in the practice of the invention) Fig. 17 is a perspective view of the calibration device of Fig. 16i Fig. 18 is a front view of a further form of calibration device) Fig. 19 is an enlarged view of part of the calibration device of Fig. 18i Figs. 20 and 21 are front views of further forms of calibration device) Fig. 22 is a side view of a unicompartmental or unicondylar knee prosthesis showing the femoral implant and the tibial implant partly in section) Fig. 23 is a perspective view of the femoral implant of Fig. 22; Fig. 24 is a perspective view of the tibial implant of Fig. 22; Fig. 25 is a perspective view of a tibia area guide insertion tool in open condition) Fig. 26 is a perspective view of the tool of Fig. 25 gripping a tibia area guides Fig. 27 is a further perspective view of the tool of Figs. 25 and 26 with three tibial area guides of differing sizes) Fig. 28 is a perspective view of a patient's knee illustrating use of the tool of Figs. 25 to 27 to position a 16 F037 tibial area guide; Figs. 29 and 30 illustrate the formation of a slot in the end of the patient's femur) Fig. 31 is a perspective view of a femur jig holder; Fig. 32 is a perspective view of the femur jig holder of Fig. 31 with a series of five femur jigs; Fig. 33 is an enlarged view of one of the femur jigs of Fig. 32; Figs. 34 and 35 illustrate the use of a first femur jig to drill a first hole in the end of the patient's femur; Fig. 36 illustrates the use of a second femur jig to drill a second hole in the end of the patient's femur; Fig. 37 illustrates the use of a third femur jig for lengthening and enlarging the slot in the patient's femur; Figs. 38 to 44 illustrate the use of a fourth femur jig in the resection of the femoral condyle; Figs. 45 and 46 illustrate use of a fifth femur jig to effect the posterior cut in the femoral condyle; Fig. 47 is a perspective view of a femoral implant insertion tool gripping a femoral implant; and Fig. 48 is a perspective view of a tibial implant insertion tool gripping a tibial implant.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings, and to Fig. 1 in particular, a calibration device for use with the surgical tool of the invention comprises a strip 1 of a plastics material which is provided with a line of calibration markers 2 in the form of a small stainless steel or other radiopaque balls or discs (e.g. tantalum or lead balls or discs) which are typically about 1 mm in diameter. In the centre of the line of calibration markers 2 there is a primary calibration marker 3 which is a radiopaque ball or disc of somewhat larger diameter than calibration markers 2. Thus, for 17 F037 example, primary calibration marker 3 can be about 2 mm in diameter. The centres of each of the calibration markers 2 and 3 lie on a single line parallel to the edges of strip 1 with an equidistant spacing between the centres of adjacent markers. Typically this spacing is about 2.5 mm.

Strip 1 is also provided with a number of holes 4 whose centres lie on a line substantially parallel to the line of the calibration markers 2 and 3 with each hole 4 being positioned vertically above a corresponding calibration marker 2. Above primary calibration marker 3 strip 1 is formed with an elongate slot 5 whose axis lies substantially at right angles to the line of the holes 4. The spacing between the centres of adjacent holes 4 thus matches exactly that between adjacent markers 2, while the spacing between marker 3 and its adjacent markers 2 also matches the spacing between slot 5 and the adjacent holes 4.

The reverse side of strip 1 is provided with a layer of a skin-compatible adhesive which is covered with a peelable protective strip 6, as shown in Fig. 2. The plastics material of strip 1 can be, for example, one of the plastics

materials use for the manufacture of conventional aseptic or antiseptic plasters or wound dressings. Similarly the adhesive and the peelable protective strip 6 can be of the kind conventionally used in the manufacture of aseptic or antiseptic plasters or wound dressings.

The markers 2 and 3 can be held in place on strip 1 in any convenient manner, for example by being glued thereto.

Alternatively strip 1 can be formed by laminating two layers of plastics material one to another, using any suitable known technique, so as to sandwich the markers 2 and 3 therebetween.

Typically strip 1 is approximately 100 mm long and 18 F037 about 20 mm wide.

In use of the device of Figs. l and 2, the peelable protective strip 6 is first removed in a manner similar to the manner of preparing a conventional aseptic or antiseptic plaster or wound dressing for application to the skin. Two such strips l are attached to a lower leg of a patient requiring orthopaedic knee surgery, as illustrated in Fig. 3, in preparation for taking pre-operative X-ray pictures.

As can be seen from Fig. 3, each strip l is applied to the patient's leg so as to lie transverse to the weight bearing axis of the tibia and with the primary calibration marker 3 lying approximately in an anteriorposterior plane including the weight bearing axis of the patient's tibia, as judged by the eye of the radiographer or other person supervising the taking of the pre-operative X-ray pictures.

One of the two strips l is positioned on the patient's leg 7 a short distance below the patient's knee and the other one a short way above the patient's ankle.

After each strip l has been attached to the patient's skin, its position is marked on the patient's skin with the aid of a pen 8 or similar device which is used to apply an indelible ink through the holes 4 and slot 5. The resulting marks (see reference numerals 4' and 5' in Figs. It to 13) will indicate on the patient's skin a position in the longitudinal direction of the strips l corresponding to, but higher on the patient's leg than, a corresponding marker 2 or 3. Since slot 5 is elongated, the resulting ink mark 5' on the patient's skin will stand out from the marks 4' corresponding to the holes 4 and will indicate a position on the patient's leg corresponding to, but higher than, the primary marker 3.

The necessary pre-operative X-ray pictures are then taken. Typical X-ray pictures are depicted diagrammatically 19 F037 in Figs. 4 to 9. These show the results of X-ray scans taken on the lower left leg of a patient whose skin has had two strips 1 attached in a similar manner to that illustrated in Fig. 3. In these X-ray pictures the images are typically somewhat magnified compared with the bones and other features corresponding to those images by a scaling factor which is typically in the range of from about 1.01:1 to about 1.20:1. Hence the spacing between the images 2' of adjacent markers 2 will be, for example, from about 1.01 to about 1.20 times larger than the actual spacing between such adjacent markers. Typically the scaling factor is about 1. 1: 1.

The X-ray picture of Fig. 4 shows the bones of the patient's foot 9, as well as the patient's tibia 10, fibula 11, patella 12, and femur 13. Reference numeral 14 indicates the weight bearing axis of the patient's tibia.

Fig. 4 also shows the images 2' and 3' of the calibration markers 2 and 3.

By studying the X-ray picture of Fig. 4, the surgeon can assess where the weight bearing axis 14 of the patient's tibia 10 lies in relation to the images 2' and 3' corresponding to the calibration markers 2 and 3. Although the dimensions of the images of the patient's bones in the X-ray picture of Fig. 4 may not correspond to the actual dimensions of the patient's bones, due to the scaling factor mentioned above, the size of, and the spacing between, the calibration markers 2 and 3 is known with accuracy. Hence the surgeon can estimate how far the weight bearing axis 14 lies from the primary calibration marker 3 of the upper strip 1 and to which side and similarly how far away from the primary calibration marker 3 of the lower strip 1 the weight bearing axis 14 of the patient's tibia actually lies and to which side. F037

Fig. 7 is a corresponding media lateral X-ray picture of the same patient's lower left leg. From the images 2' and 3' of the calibration markers 2 and 3, the surgeon can estimate where a line 15 corresponding to the line 14 shown on Fig. 4 lies. (Line 14 actually represents an anterior posterior plane including the weight bearing axis of the patient's tibia, whereas line 15 indicates a media lateral plane including that axis). Reference numeral 16 indicates a line tangential to the right hand side of markers 2, 3 which will correspond approximately to the surface of the patient's skin. With the aid of the X- ray picture of Fig. 7 the surgeon can estimate the angle between a plane containing the line 16 and the plane upon which the transverse saw cut required in order to remove the medial side of the top of the patient's tibia 10 should be made as part of a surgical operation to implant a so- called unicompartmental knee prosthesis. That angle is not affected by the scaling factor mentioned above and is typically in the range of from about 80 to about 85 .

Reference numeral 17 indicates the plane of that saw cut.

Prior to the operation to implant a unicompartmental knee prosthesis in the medial side of the patient's knee, the strips 1 are removed and the patient's lower leg is sterilized in conventional manner using an antiseptic solution, such as an iodine solution, which will not remove the ink marks 4', 5' (see Figs. 11 to 13) made by the marker pen 8 on the patient's skin.

Fig. 10 shows an alignment device 20 for use in orthopaedic surgery on a patient's leg. This is illustrated in closed condition in Figs. 10 and 11 but in somewhat extended condition in Fig. 14. Alignment device 20 includes an elongate first member 21 which carries at its upper end a block 22 in which is mounted a pivot 23 for a second 21 F037 elongate member 24 which has a hollow upper end for receipt of a shaft 25 of a table 26 for a cutting block 27 for use in resecting a top end of a patient's tibia 10 during a surgical operation to implant a unicompartmental knee prosthesis. Table 26 is provided with a hole 28 for a purpose which will be described below.

The underside of cutting block 27 is provided with a cleat shaped key (not shown) which includes a transverse bar that is elliptical in plan and is received in a corresponding recess that is provided with an opening in the form of a matching elliptical slot (also not shown) to receive the transverse bar and that has undercut sides so as to provide a space within which the transverse bar can turn.

In this way cutting block 27 can be held in place on table 26 and yet can also be swivelled on table 26, while being readily removable when the surgeon so desires by rotation through an angle of about 90 about a vertical axis parallel to that of shaft 25. The forward face of cutting block 27 (which faces to the rear as depicted in Fig. 10) is curved.

At its lower end, first elongate member 21 carries a second block 29, the position of which in relation to block 22 can be adjusted as described below in relation to Fig. 14. Above block 29 is a further block 30 having a pair of wings 31 (only one of which is visible in Fig. 10) to one of which is attached a flexible coil spring 32 having at its free end a ring 33 for a purpose to be described hereinbelow.

Immediately above block 30 there is mounted a further arcuate block 34 which is formed with a slot 35 in a vertical plane containing the axis of elongate member 21 and also with a transverse slot 36. Vertical slot 35 receives a flattened end portion 37 of second elongate member 24 while transverse slot 36 receives a threaded shank 38 of a d 22 F037 securing member 39, shank 38 being received in a threaded bore adjacent the lower end of flattened end portion 37.

This threaded bore extends right through flattened end portion 37 so that securing member 34 can be fitted on either side of the alignment device 20 to suit the surgeon's convenience. Arcuate block 34 also bears a graduated scale on each side marked in degrees ( ) for a purpose to be described hereinafter.

Block 22 is formed with a notch 41 and with a pair of ears 42. Similarly block 29 is provided with a notch 43 and with a pair of ears 44.

As can best be seen in Fig. 14, alignment device 20 is extensible, an inner member 45 being slidably received within elongate second member 24 to permit use of the device on patients having different lengths of tibia. In order to increase the accuracy of assessment of the position of the weight bearing axis of the patient's tibia it is desirable to position devices 1 as near as possible to the ends of the patient's tibia. Hence it is convenient to be able to adjust the length of the alignment device. The inner member and elongate second member 24 can be fixed one to another in any convenient manner, for example by means of a locking screw (not shown).

Cutting block 27 carries a removable block 46 in which is mounted a curved stylus 47 for a purpose to be described hereinbelow. Block 46 is held on cutting block 26 by means of an adjustment knob 48 which comprises the head of a screw whose threaded shank is received in a threaded bore in the cutting block 27.

Cutting block 27 is further provided with a pair of vertical saw guide slots 49, 50 and with a horizontal saw guide slot 51 for making a transverse cut during resection of the patient's tibia. A pair of holes 52 are also 23 F037 provided in cutting block 27 through which pins (not shown) can be passed to secure cutting block 27 to the top of the patient's tibia 10. Block 22 is also formed with a bore 53.

Block 22 is provided with a pair of holes 54 (only one of which is visible in Fig. 10) for passage of corresponding screws or pins (not shown) by means of which the surgeon can secure block 22 to the patient's tibia 10 during the planned surgery on the patient's knee.

As described above in relation to Figs. 1 to 9, a pair of calibration devices 1 are attached to the patient's lower leg prior to pre-operative X-ray scanning. In addition the position of the calibration devices 1 are marked on the patient's leg (as shown at 4' and 5' in Fig. 11) in indelible ink using the marker pen 8 to record on the patient's skin the position of the holes 4 and slot 5.

Before the surgeon makes the first incisions, the calibration devices 1 are removed and the patient's skin is sterilized using an antiseptic solution in which the ink of the marker pen 8 is essentially insoluble.

The surgeon can utilise the X-ray pictures of Figs. 4 to 9 to assess where the weight bearing axis of the patient's tibia 10 lies. Thus, for example, in Fig. 4 the plane of the weight bearing axis 14 passes to the left of image 3' of primary marker 3, between the images 2' of the first and second calibration markers 2 of the upper calibration device 1. The plane of axis 14 also passes to the right of the image 3' of the primary calibration marker 3, between the images 2' of the first and second calibration markers 2 to the right of primary calibration marker 3 of that lower calibration device 1.

Although both of the calibration devices 1 have at this stage now been removed, there remain the markings 4', 5' in indelible ink on the patient's skin showing the positions of t 24 F037 the holes 4 and of slot 5 of each calibration device 1 which were vertically aligned with its calibration markers 2 and with its primary marker 3 respectively. By adjusting the length of the alignment device 20 as necessary and aligning the notches 41 and 43 in positions relative to the indelible ink markings 4', 5' on the patient's skin corresponding to the positions of the images 2' and 3' on the X-ray pictures of Fig. 4, the surgeon can ensure that the axis of first elongate member 21 is substantially aligned with the weight bearing axis of the patient's tibia, as illustrated in Figs. 11 to 13.

Fig. 11 illustrates diagrammatically the surgical opening 55 made by the surgeon in the patient's knee 56.

Typically, opening 55 is formed by making a substantially vertical cut approximately 1 inch (2.5 cm) in length or less (e.g. about 2.2 cm in length) through the tissue overlying the top of the patient's tibia 10 and the bottom of the patient's femur 13. As illustrated, the operation to be performed on the patient's knee is insertion of a unicompartmental or unicondylar knee prosthesis comprising a tibial component (not shown in Fig. 11) and a femoral component (also not shown in Fig. 11) on the medial side of the patient's knee 56. The surgeon can observe the progress of the operation by means of an arthroscope (not shown) inserted through a portal incision into the lateral side of the patient's knee.

Fig. 11 also shows how spring 32 is used to secure the lower end of alignment device 20 to the patient's lower leg.

As can be seen from Fig. 11, spring 32 passes around the patient's leg and ring 33 is secured over a pin 57 provided for that purpose on the other wing 31 (which is not visible in Fig. 10). In addition the surgeon can temporarily secure block 22 directly to the patient's tibia 10 by means of # F037 screws or pins passed through holes 54.

Having secured first elongate member 21 in position on the patient's leg, the surgeon can then pivot the elongate second member 24 about the pivot 23 until an inscribed line 58 (see Fig. 10) on flattened end 37 of second elongate member 24 is aligned with the appropriate indicium on the scale 40 corresponding to the angle which the surgeon has selected and which is indicated in Fig. 7. Having made this adjustment the surgeon then secures second elongate member 24 at the required angle by tightening securing member 39.

This will then set the horizontal saw guide slot 51 at the correct angle to make the lateral cut along plane 17 of Fig. 7.

Fig. 14 illustrates the alignment device 20 positioned on the patient's left leg (but with spring 32 omitted for the sake of simplicity). Indicium 58 is set at angle of approximately 82 . The tip of stylus 47 is inserted through surgical incision 55 and is observed by the surgeon through an arthroscope (not shown) inserted into the lateral side of the patient's knee. As shown, the tip of stylus 47 is resting on the top of the patient's tibia 10. Once the surgeon is satisfied that stylus 47 is in the correct position, table 26 is temporarily fixed to the patient's tibia with the aid of a pin or screw passed through hole 28.

The position of the saw guide slot 51 below the tip of stylus 47 is predetermined and is equivalent to the thickness of the tibial implant (not shown) to be implanted.

Thus the position of the resection level is now fixed.

Typically this distance is 7.5 mm. Then the surgeon can turn cutting block 27 about its vertical axis until he has aligned the appropriate vertical saw guide slot 49 or 50 to his satisfaction so that, when he eventually makes a vertical saw cut it will not damage either of the cruciate 26 F037 ligaments. In the case of a medial prosthesis for the left knee 56, the surgeon will use vertical saw guide slot 50.

Cutting block 27 can then be temporarily secured to the patient's tibia 10 by means of a screw or pin passed through one or both of holes 52.

The surgeon can then utilise a conventional reciprocating surgical saw (not shown) to make the vertical cut 59, using the appropriate one of the guide slots 49, 50, and to make the lateral cut 60, as shown in Fig. 15. After removing cutting guide 27 the surgeon can then complete the cuts needed to free the resulting resected piece 10' of the patient's tibia 10 and remove this as well as any knee fragments through incision 55. Alignment device 20 can then be removed after first having removed any pins or screws Is which have been used to hold it temporarily in position on the patient's tibia 10.

The calibration device 1 of Figs. 1 to 9 is provided with a single row of markers 2, 3 and with a single row of holes 4 and slot 5. Alternatively the markers 2, 3 could be arranged in two parallel rows with the markers 2 in one row offset transversely with respect to the markers 2 in the other row. Similarly two parallel rows of holes 5 could be provided with the holes in one row being offset transversely with respect to the holes 4 in the other row.

An alternative form of calibration device 61 is shown in Figs. 16 and 17. This comprises a flexible strip 62 of radiopaque material, such as stainless steel, tantalum or lead, the ends of which are passed through a pair of links 63 and then bent back upon the strip 62. A pair of strap members 64, 65 are secured to respective links 63. At its free end, strap member 64 carries one part 66 of a hook and loop fastener (for example, a hook and loop fastener sold under the registered trade mark VELCRO), while the other 27 F037 strap member 65 carries the other part 67 of the hook and loop fastener. In this way the calibration device 61 can be secured around the lower leg of a patient requiring knee surgery.

Flexible strip 62 is provided with a series of holes 68 arranged in a line and with a central slot 69. Holes 68 constitute calibration markers for the device 61, while slot 69 performs the function of a primary calibration marker.

The use of calibration device 61 is similar to that of calibration device 1, of Figs. 1 to 9. Thus after application to the patient's leg in preparation for pre- operative X-ray scanning, a marker pen is used to mark in indelible ink the positions of the holes 68 and of the slot 69 upon the patient's skin. As in Fig. 3, two calibration Is devices 61 are positioned on the patient's lower leg before X-ray pictures are taken.

The resulting X-ray pictures will in this case show an opaque transverse band corresponding to the position in each of the strips 62 of the respective calibration devices 61, while the positions of the holes 68 and of the slot 69 will show up as clearer patches on the X-ray pictures. As with the calibration device 1 of Figs. 1 to 9, the surgeon can assess the position of the weight bearing axis of the tibia on the X-ray pictures relative to the positions of the holes 68 and slot 69 and can then use the alignment device 20 in conjunction with the ink marks on the patient's skin to set up the alignment device 20 in alignment with the axis of the patient's tibia 10.

Instead of utilising a fastener of the hook and loop type, the strap members 64, 65 could be fastened using a conventional buckle.

Yet another possibility is to replace the strap members 64, 65 with an elastomeric strip which is fixed at one end 28 F037 to one of the links 63 and is provided at its other end with a hook-shaped catch for engagement with the other link 63.

Figs. 18 and 19 show a further form of calibration device 70 which consists of a strip of radiolucent material, for example a plastics material of the type described above in relation to calibration device 1. As with calibration device 1, calibration device 70 can be provided on its rear side with a skin-compatible adhesive which, prior to use, is covered with a peelable protective strip (not shown).

Device 70 is formed with a series of holes 71, each surrounded by calibration marker in the form of a ring 72 of a radiopaque material, as can be best seen from Fig. 19, which is an enlarged view of one of the calibration markers 72. It also has a primary marker 73 also made of a radiopaque material which is provided with a cross-shaped slot 74.

The calibration device 70 can be used in a similar manner to that described above in relation to calibration device 1, the holes 71 and the cross-shaped slot 74 permitting marking of the patient's skin after application of the calibration device 70 thereto. In this case the images of the calibration markers 72 will take the form of rings, while the image of the primary calibration marker 73 will show up as a larger dark patch with a lighter patch corresponding to the cross-shaped slot 73.

Fig. 20 shows a still further form of calibration device 75 which is circular in plan but is otherwise similar in construction to the calibration device 70 of Figs. 18 and 19. This is provided with calibration markers 76 and primary calibration markers 77 which are similar to markers 72 and 73 respectively of device 70. Calibration device 75 may also find application in other forms of pre-operative X- ray imaging, for example to locate the position of the hip 29 F037 centre, the top of the tibia, a fracture, a tumour, kidney stones or gallstones, or a foreign metal body, such as a bullet.

Fig. 21 shows yet another calibration device 78 which is square in plan and is similar in construction to that of Fig. 20, the primary calibration marker 78 being similar to the primary calibration marker 73 of Fig. 18 and the corresponding primary calibration marker 77 of Fig. 20.

Calibration markers 80 are similar to calibration markers 72 and 76.

Fig. 22 is a side view, partially in section, of a unicompartmental knee prosthesis. This comprises a femoral implant 101 and a tibial implant 102. As can be seen from Fig. 22, femoral implant 101 is provided with a pair of pegs 103, 104 for reception in prepared bores in the lower end of the patient's resected femur. It also has a medial fin 105.

Conveniently the surgeon will have available three sizes of femoral implant 101.

Tibial implant 102 comprises a metal plate 106 to which is attached a meniscus 107 made of a plastics material, such as high molecular weight polyethylene. Meniscus 107 can, for example, be moulded on, or clipped to, metal plate 106.

The lower surface of plate 106 may be roughened or textured to facilitate bonding thereof to the upper end of the patient's resected tibia. As can be seen from Fig. 24 tibial implant 102 is generally D-shaped in plan and its maximum transverse dimension may be, for example, 38 mm, 41 mm, 44 mm, or 48 mm. The upper surface of meniscus 107 is appropriately dished (as can be seen from Fig. 22) to form a bearing surface for the femoral implant 101. Conveniently the surgeon will have available all three sizes of tibial implant, each in five different thicknesses.

In Fig. 25 there is shown a tibia area guide insertion F037 tool 108 which can be used, as indicated in Fig. 26 for insertion of a tibia area guide 109 for use in implantation of the unicompartmental (or unicondylar) knee prosthesis of Figs. 22 to 24.

Fig. 26 shows the tool 108 holding a tibia area guide 109 which has a similar D-shape in plan to tibial implant 102. As indicated in Fig. 27 tool 108 can be used with a variety of sizes of tibia area guides 109, 110, 111, each of which corresponds in plan to one of the sizes of tibial implant 102. Preferably the under surface of tibia area guides 109, 110, 111 is in each case formed with small spikes, or is textured, so that once it has been placed in position on the patient's resected tibia it will not tend to move laterally.

IS As can be seen from Figs. 26 and 27, each tibia area guide 109, 110, 111 is formed in its upper face with a wide groove 112 of dovetail section with undercut sides. Groove 112 could alternatively be, for example, of inverted T section or U- section or have vertical walls, in which case an appropriate modification to tool 108 is required.

Fig. 25 shows the tool in its fully open position which facilitates cleaning. At its forward end it carries a shaped portion 113 which is a snug fit in groove 112. It also has a sloping front end 114. An operating lever 115 is pivoted to the rear end of tool 108 for pivotal movement about pivot pin 116. Tool 108 also includes a rod 117 which is received in a channel 118 in the top side of the body of the tool 108 and is pivoted to the operating lever 115 by means of a pivot pin 119. At its front end rod 117 carries a soft silicone rubber pad 120 and is provided with a pair of lateral projections 121, only one of which is visible in Fig. 25.

In use of the tool 108, the operating lever 115 is F037 raised and the rod 117 lowered into the channel 118 so that projections 121 can clear the forward end of the tool and bear against the sloping front end 114. Then the dovetail shaped portion 113 can be slid into the groove 112 on a selected tibia area guide 109, 110 or 111 with the operating lever 115 still slightly raised. Upon lowering the operating lever 115, rod 117 is drawn backwardly along the channel 118 so that the projections 121 are forced downwardly along the sloping front end 114 so as to press pad 120 against the bottom of groove 112 to hold the selected tibia area guide 109, as shown in Fig. 26.

Following resection of the patient's tibia 10, the surgeon uses tool 108 to insert a tibia area guide 109 through the incision 55 and then manoeuvres it until he can place it on top of the patient's resected tibia 10, as shown in Fig. 28, having first positioned the patient's leg so that the knee is in flexion and ensured that it is satisfactorily restrained in this position. He then raises operating lever 115 thereby causing projections 121 to rise up the sloping front end 114 of tool 108 and releasing the pressure exerted on soft silicone rubber pad 120. (If he is not satisfied with the seating of tibia area guide 109 on top of resected tibia 10, then he can withdraw tibia area guide 109 and replace it with a tibia area guide of a different size, for example tibia area guide 110 or 111).

Once he is satisfied with the size and positioning of the tibia area guide, e.g. tibia area guide 109, he then withdraw tool 108 from groove 112 leaving area tibia area guide 109 temporarily in position and inserts a first end 122 of a dual ended spacer 123. First end 122 comprises a tongue member which is also of dovetail section so as to fit in groove 112.

Tibia area guide 109 is somewhat thinner than the 32 F037 tibial implant 102 eventually to be cemented in place on the resected upper end of the patient's tibia 10. First end 122 projects slightly above the upper surface of tibia area guide 109 after insertion in groove 112, so that the combined thickness thereby resulting corresponds to that of the selected tibial implant 102, e.g. 7.5 mm.

Since tibial implant 102 may be, for example, 7.5 mm, 9.0 mm, or 11.0 mm in thickness, the surgeon will use a corresponding dual ended spacer 123, depending upon the thickness of the tibial implant 102 eventually used. If after insertion of first end 122 there remains a gap between the condyle of the femur and the upper surface of tibia area guide 109, then the surgeon may choose to use a thicker tibial implant 102. He may then select a different double ended spacer 123 until he is satisfied with the flexion gap.

The other end 124 of dual ended spacer 123 has a predetermined thickness (e.g. 3.0 mm in the case of a tibial component 7.5 mm thick), for a reason which will be described hereafter.

First end 122 extends forwardly from a shoulder portion which is formed with a slot 126 to receive a saw blade (not shown in Fig. 28). Slot 126 is aligned with a groove 127 in the upper surface of first end portion 122. The slot 126 is arranged so as to be a relatively tight fit at its rearward end for a reciprocating saw blade 128 but to widen slightly forwardly into slot 127 which also widens slightly forwardly.

Figs. 29 and 30 illustrate how a reciprocating saw blade 128 can be inserted in slot 126 and guided by groove 127 to cut a slot 129 in the condyle of the patient's femur 13. This slot is intended to receive a posterior part of the medial fin 105 of the femoral implant 101.

A femur jig holder 130 is illustrated in Fig. 31. This 33 F037 has an elongate body 131 which has a channel 132 along its upper surface. An operating lever 133 is pivotally attached by means of a pivot 134 near the rear end of the body 131.

An operating rod 135 is pivotally attached by means of pivot 136 tooperating lever 133 and is adapted to fit in channel 132. Near its forward end operating rod 135 is provided with lateral projections 137 which can be received in respective inclined slots 138 formed near the front of body 131. Operating rod 135 also has a shaped forward end 139.

The femur jig holder 130 is shown in its open position in Fig. 31. In this condition it can be cleaned readily.

Upon lowering operating rod 135 into channel 132 with the operating lever 133 raised, the lateral projections 137 can be lowered into the slots 138. Upon then lowering the operating lever 133, shaped forward end 139 is drawn towards the bottom of the channel 132 and can exert a gripping action on an appropriately shaped femur jig inserted in transverse slot 140.

Fig. 32 shows the femur jig holder 130 and a series of -20 five femur jigs 141, 142, 143, 144, and 145 which are designed for use in implantation of a femoral implant 101 of the appropriate size for implantation in the patient's knee.

Fig. 33 is an enlarged view of part of the fifth femur jig 145. As illustrated in Fig. 32, femur jig holder 130 is gripping third femur jig 143.

Each of the five femur jigs 141, 142, 143, 144, and 145, includes a web portion 146 which is formed on each face with an indent 147 which is adapted to engage with the shaped forward end 139 of the operating rod 135 of femur jig holder 130.

First femur jig 141 is sized so as to match a corresponding size of femoral implant 101, as will be described below, and is provided at the upper end of web 34 F037 portion 146 with a bush 148 having an aperture 149 extending through it. Extending forward from web portion 146 is a fin 150.

The use of first femur jig 141 is illustrated in Figs. 34 and 35.

As can be seen in Fig. 34, the surgeon has retained the patient's leg with the knee in flexion and has withdrawn first end 122 of the dual ended spacer 123 as well as the tibia area guide 109. Having now inserted second end 124 of dual ended spacer 123, the surgeon then uses femur jig holder 130 to insert first femur jig 141 so that the fin 150 is received in the previously formed slot 129 in femur 13.

The thickness of fin 150 is chosen so that it is a tight fit in slot 129. Moreover fin 150 is sized and shaped so that, IS when it is inserted into slot 129 to a depth corresponding to the depth to which medial fin 105 of the femoral implant 101 will eventually be implanted, the curvature of its lower edge 150' will, as can be seen from Fig. 35, extend substantially parallel to the corresponding curvature of the bearing surface 101' of the femoral implant 101. When correctly positioned in slot 129, fin 150 should project downwards beyond the surface of the condyle of femur 13 by a distance which, together with the thickness of second end 124, corresponds to the thickness of the selected tibial implant 102. Thus in the case of a 7.5 mm thick tibial implant 102, this distance should be 4.5 mm, since the thickness of second end is 3 mm. If the surgeon finds that the fin 150 projects too much, then he should force it further into slot 129 or deepen slot 129. Fig. 35 shows how the thickness of the second end 124 of dual ended spacer 123, when added to the projecting height of fin 150, corresponds to the thickness of the tibial implant 102. It can also be seen from Fig. 35 that, once the first femur jig F037 141 has been correctly positioned, the position of the posterior cut to be described below is fixed since this will correspond to the position of the upper edge 150" of fin 150 in slot 129. As already explained femoral implant 101 may be provided in a number of sizes, each of which will require use of a corresponding size of first femur jig 141.

Having inserted fin 150 in slot 129 in femur 13 with the patient's knee still in flexion, the surgeon can use the arthroscope to satisfy himself that the rear end of fin 150 is correctly positioned. In addition the surgeon can, whilst the first femur jig 141 and second end 124 remain in position as illustrated in Figs. 34 and 35, flex the patient's leg further or straighten it somewhat so as to check during these flexing and straightening movements that the tension in the patient's knee ligaments will be satisfactory. If the tension is too tight, then the surgeon can force first femur jig 141 further into groove 129. On the other hand, if the tension is too slack, the surgeon may decide to use a different thickness of tibial implant 102, in which case a different double ended spacer 123 with a different thickness of second end 124 should be selected.

He can also still decide to use a femoral implant 101 of a different size, in which case he will insert a new first femur jig 141 of appropriate size and repeat the test of the tightness of the ligaments.

It will be appreciated by the skilled reader from inspection of Fig. 34 that, at this stage of the operation, it is not possible to straighten the patient's leg fully because of interference between the forward end of fin 150 and second end 122.

Once the surgeon is satisfied that the correct size of first femur jig 141 has been correctly inserted to match the selected size of femoral implant 101 and that the correct 36 F037 size of double ended spacer 123 has been selected with the appropriate thickness of second end 124 to match the selected thickness of tibial implant 102, he can now drill a hole in femur 13 to receive the peg 104 of femoral implant 101, using aperture 149 as a guide for drill 151.

Having drilled a first hole in femur 13 for peg 104, the surgeon then removes first femur jig 141 and second end 124 of double ended spacer 123. He then inserts second femur jig 142 in slot 129, as illustrated in Fig. 36, having first straightened the patient's leg somewhat.

Second femur jig 142 is also designed to be a tight fit in slot 129. It is provided with a rod 152 which fits in the hole 153 which the surgeon has just drilled in the end of femur 13 using first femur jig 141. It also includes a small fin 154 which is adapted to fit in slot 129 in the end of femur 13. At its top end it is provided with a bush 155 which has a bore 156 formed through it.

Having positioned second femur jig 142 in position with the rod 152 engaged in hole 153 and with the small fin 154 engaged in slot 129, the surgeon can then drill a second hole in the end of femur 13 to receive peg 103 of femoral implant 101 using for this purpose drill 151 and bush 155 with its bore 156 as a drill guide.

Having drilled hole 157 to receive peg 103 of femoral implant 101, the surgeon next uses third femur jig 143 in the manner illustrated in Fig. 37. Third femur jig 143 is again designed to be a tight fit in slot 129 and comprises a body 158 from the front side of which projects the web portion 146. A pair of pegs 159, 160 project rearwardly from body 158. A slot 161 extends from the top to the bottom of body 158 and into each of pegs 159, 160.

With the patient's leg still slightly bent, the surgeon then inserts pegs 159, 160 of third femur jig 143 into holes 37 F037 153, 157 previously drilled in the patient's femur 13. The surgeon then uses saw blade 128 to extend slot 129 further around the end of the patient's femur, using the slot 161 as a saw guide.

Fig. 38 shows fourth femur jig 144 in more detail.

This is formed with a pair of pegs 162, 163 extending rearwardly from web portion 146. Again it is designed to be a tight fit in slot 129.

Still with the patient's knee slightly bent, the surgeon now introduces fourth femur jig 144 with the aid of femur jig holder 130 through the incision 55 so that peg 162 is received in hole 153, while peg 163 is received in hole 157 in the patient's femur 13. As can be seen in Fig. 38, the web portion 146 is partially received in the extended slot 129 but projects therefrom.

When correctly positioned in slot 129, web portion 146 of fourth femur jig 144 should project by a distance of, for example, 4.5 mm from the surface of the condyle of femur 13, when the surgeon has decided to use a tibial implant 102 that is 7.5 mm thick. Before proceeding further the surgeon checks the extension gap with the aid of second end 124 of dual ended spacer 123, as indicated in Fig. 39.

The purpose of fourth femur jig 144 is to act as a guide for a burr for shaping the end of the femur 13 in readiness for final implantation of the femoral implant 101.

Figs. 39 and 40 illustrate the correct position for the fourth femur jig 144 in the end of the patient's femur 13 for use of the burr. The surgeon has straightened the patient's leg and inserted second end 124 of the dual ended spacer 123 to check the extension gap. He can then, with second end 124 and fourth femur jig 144 still in place, flex the patient's leg somewhat to check the tension in the patient's knee ligaments during this flexing movement. When 38 F037 fourth femur jig 144 is correctly placed, the right-hand face of second end 124, as illustrated in Fig. 40, will be abutting the resected end of the patient's tibia 10, while the fourth femur jig 144 is positioned in the slot 129 in the end of the patient's femur with pegs 162, 163 inserted in holes 153, 157 respectively. When fourth femur jig 144 is correctly positioned, there should then be no gap between the projecting surface of its web portion 146 and second end 124 during the flexing movement just described.

If the surgeon finds that the extension gap is too small, then he should remove second end 124 of dual ended spacer 123 and force fourth femur jig 144 further into slot 129.

Fig. 40 also indicates the eventual position after implantation of femoral implant 101. In this case fin 105 is received in the remains of slot 129, whilst sufficient bone has been removed with the aid of the burr to allow femoral implant 101 to occupy the position shown in Fig. 40.

Figs. 41 and 42 illustrate use of a burr 164 (which is conveniently of the type used in acromioplasty). This is mounted for rotation in a guide 165 on the end of tool 166.

As can be seen from Figs. 43 and 44, guide 165 is formed with a groove 167 which fits over the web portion 146 of fourth femur jig 144.

By moving guide 165 along the exposed end of web portion 146 of fourth femur jig 144, the surgeon removes bone from the end of the femoral condyle in which the femoral implant 101 is to be implanted. Having removed the bone along one side of fourth femur jig 144, he can then reverse the position of the guide 165 and replace it so that fourth femur jig 144 again engages in slot 167. Upon moving guide 165 again along fourth femur jig 144, the surgeon removes bone from the condyle on the other side of fourth 39 F037 femur jig 144.

Fig. 45 illustrates the situation at this stage of the implantation operation prior to use of the fifth femur jig 145. The slot 129 has been prepared for acceptance of the fin 105 on the femoral implant 101, while the holes 153 and 157 are ready to receive the pegs 103, 104 respectively of the femoral implant 101. Moreover an appropriate amount of bone has been resected from the femoral condyle. Fig. 44 also indicates the resected upper end of the patient's tibia 10.

The fifth femur jig 145 is also shown in Fig. 44. This is again designed to be a tight fit in slot 129 and has a rod 168, a small fin 169 and a small rearward projection 170 of the web portion 146, as well as a flange 171.

Using femur jig holder 130, the surgeon inserts rod 168 into the hole 153 so that small fin 169 and rearward extension 170 are received in the slot 129, as indicated in Fig. 46. The surgeon then uses the lower face of flange 171 as a guide for saw blade 128 to make the posterior cut in the patient's femur 13.

After ensuring that all bone fragments have been removed from the site of the operation, it is now time to insert the femoral implant 101 and then the tibial implant 102. For this purpose the femoral implant insertion tool 172 illustrated in Fig. 47 is used. This has a bush 173 of plastics material in which a handle 174 is freely mounted for rotation about its axis. Handle 174 can also move axially with respect to bush 173.

Attached to bush 173 is a body 175 which has an internal axial bore which is internally threaded and engages a corresponding screw thread on handle 174. Handle 174 also carried a frusto-conical collar 176. A pair of jaw members 177, 178 are pivotally mounted on body 175 by means of pivot F037 pins 179, 180. At their forward end jaw members 177, 178 carry jaws 181, 182. At their rearward ends jaw members 177, 178 are provided with ramp faces 183, 184.

To grasp the femoral implant 101, the handle 174 is first rotated so as to draw frusto-conical collar 176 away from body 175, thereby releasing any pressure on ramp faces 183, 184 and permitting jaws 181, 182 to be opened. A suitable part of the femoral implant 101 can then be applied against the front end of bush 173, as shown in Fig. 47, whereupon the surgeon can rotate handle 172 to force frusto- conical collar 176 towards body 175 thereby bringing it into engagement with ramp faces 183, 184 and causing jaws 181, 182 to close and grip the femoral implant 101. It is an advantage of the femoral implant insertion tool 172 that femoral implant 101 can be gripped at any desired angle.

The surgeon can then apply bone cement to the resected end of the femur 13 and/or to the femoral implant 101 and press the femoral implant 101 into place on the end of the patient's resected condyle with the pegs 103, 104 positioned in the holes 157, 153 respectively. Any superfluous cement can then be removed before it has set, whereupon the tibial implant 102 can then be placed in position. This is inserted with the aid of tibial implant insertion tool 185 shown in Fig. 48.

Tibial implant insertion tool 185 comprises a body 186 in which is threadedly engaged a handle 187 which carries a frusto-conical collar 188. A gripping member 189 is pivotally mounted on body 186 for pivotal movement about pivot pin 190. At its rearward end gripping member 189 is formed with a ramp face 191 which is adapted to cooperate with frustoconical collar 188. At its forward end gripping member 189 is provided with a soft plastics pad 192, e.g. of silicone rubber, for gripping the meniscus 107 of the tibial 41 F037 implant 102. The lower part of body 186 is provided with a forwardly extending flange (not shown) so that tibial implant 102 can be gripped between this flange and the soft pad 192.

After placing the femoral implant on the flange on the body 186, having first rotated handle 185 to relieve any pressure by frusto-conical collar 188 on ramp face 191, the surgeon can then rotate handle 185 in the opposite direction to cause frusto-conical collar 188 to bear against ramp face 191, thereby pressing soft pad 192 onto the top of the meniscus 107.

The surgeon then applies bone cement to the resected part of the patient's tibia 10 and/or to the underside of metal plate 106 and inserts tibial implant 102 into the correct position on the patient's resected tibia 10. After cleaning off any excess bone cement before it sets and checking that the implantation has been successfully performed, the surgeon closes the incision 55 and stitches up the wound, and also withdraws the arthroscope and closes the portal through which it has been inserted.

Instead of making second end 122 of dual ended spacer 123 a snug fit in groove 112 of tibia area guide 109, it may alternatively be designed so that the plane in which the saw blade 128 cuts can be adjusted in order that the surgeon can ensure that the plane of slot 129 lies in the proper anterior-posterior direction in the condyle of the patient's femur 13. This can be achieved, for example, by making the tongue member a loose fit in the groove 112 but instead providing it with a cylindrical peg on its undersurface to fit in a corresponding cavity in the bottom of groove 112 so that the tongue member can be pivoted about that cylindrical peg. Alternatively tibia area guide 109 may have a cylindrical peg on its upper surface which the tongue member 42 F037 of first end 122 has a corresponding cavity in it so as to allow a limited amount of rotation of first end 122 relative to tibia area guide 109. l

Claims

43 F037 CLAIMS: 1. An alignment device for use in the course of

orthopaedic surgery on the knee of a patient comprising: an elongate first member for temporary attachment to a lower leg of a patient below a knee requiring orthopaedic surgery, the elongate member having a lower end and an upper end; an elongate second member having a first end with an axial bore therein and a second end, the elongate second member being pivotally attached adjacent its first end to the first elongate member adjacent to the upper end thereof for pivotal movement substantially in an anterior-posterior plane; locking means for locking the elongate second member at a selected angle relative to the first elongate member.
2. An alignment device according to claim l, wherein the locking means comprises an arcuate arm mounted on the first elongate member and a locking member for locking the elongate second member to the arcuate arm.
3. An alignment device according to claim 2, wherein the arcuate arm is provided with a transverse slot and wherein the locking member comprises a locking knob having a threaded shank that extends though the transverse slot and is threadedly received in a corresponding threaded transverse bore formed in the elongate second member adjacent the second end thereof.
4. An alignment device according to claim 2 or claim 3, wherein the arcuate arm is provided with a longitudinal slot in which the elongate second member moves.
5. An alignment device according to any one of claims 2 to 4, wherein the arcuate arm is provided with a graduated scale.
6. An alignment device according to any one of claims l to 44 F037 5, wherein the first elongate member is extensible.
7. An alignment device according to any one of claims 1 to 6, wherein the first elongate member has a notch at each end to permit the axis of the first elongate member to be aligned with respect to markings on the patient's skin so as to align the axial bore of the second elongate member with the weight bearing axis of the patient's tibia.
8. An alignment device according to any one of claims 1 to 7, wherein at least one aperture is provided adjacent the upper end of the first elongate member for passage of a pin or screw for temporary attachment of the device to a patient's tibia.
9. An alignment device according to any one of claims 1 to 8, further including means mounted adjacent the lower end of the first elongate member for embracing the patient's leg and securing the lower end of the device to the outside of the patient's leg.
10. A surgical implement for use in resection of an upper surface of a patient's tibia during a surgical operation to implant a unicompartmental knee prosthesis in the patient's knee comprising; an alignment device according to any one of claims 1 to 9; a support table mounted at an upper end of a shaft and orthogonal to its axis, the shaft being received in the axial bore of the second elongate member; and a cutting block mounted on the support table provided with at least one slot extending substantially parallel to the axis of the shaft for passage of a surgical saw for effecting a vertical cut in a patient's tibia during resection thereof and a transverse slot extending substantially orthogonal to the axis of the shaft for making a transverse cut in a patient's tibia at an angle determined F037 by the selected angle.
11. A surgical implement according to claim 10, wherein the cutting block is mounted on the table so as to be pivotable about an axis orthogonal to the upper surface of the table.
12. A surgical implement according to claim 10 or claim 11, wherein the cutting block is removable from the table.
13. A surgical implement according to any one of claims 10 to 12, wherein the table is provided with a bore to receive a pin or screw for temporarily securing the table to a patient's tibia during the surgical implantation operation.
14. A surgical implement according to any one of claims 10 to 13, further including a stylus mounted on the cutting block having a tip positioned at a selected height above the transverse slot of the cutting block for determining the position of the top of the tibia of the patient prior to effecting the transverse cut during resection of the tibia.
15. A surgical implement according to any one of claims 10 to 14, wherein the cutting block is provided with at least one bore for receipt of a pin or screw to permit temporary attachment of the cutting block to the tibia of the patient.
16. A tibia area guide for use in the surgical implantation of a unicompartmental knee prosthesis in a knee of a patient comprising a member adapted to be received on an upper end of a surgically resected tibia of the patient and having a dovetail section groove in an upper surface thereof for receipt of a saw guide for use in cutting a groove in a condyle of the patient's femur.
17. A tibia area guide according to claim 16, wherein the undersurface of the member is roughened to prevent slippage of the tibia area guide on the upper surface of the resected tibia during cutting of the slot in the condyle.
18. A surgical tool for use in the surgical implantation of a unicompartmental knee prosthesis in a knee of a patient r ' 46 F037 comprising a first end, a second end, and means connecting the first and second ends, the first end comprising a block formed with a saw guide slot in an upper side thereof for receipt of a saw blade for cutting the slot in the condyle, and a tongue member which extends forwardly of the block having a groove in an upper surface thereof aligned with the saw guide slot and has a dovetail section for receipt in a corresponding dovetail section groove in an upper surface of a tibia area guide so that the saw guide slot and the groove in the tongue member face upwardly.
19. A surgical tool according to claim 18, wherein the saw guide slot and the groove in the tongue member both widen in the forward direction of the tool.
20. A surgical tool according to claim 18 or claim 19, wherein the second end has a predetermined thickness less than that of a corresponding tibial implant.
21. A tibial area guide insertion tool comprising; an elongate body having a groove in an upper side thereof, a forward portion having a dovetail section for receipt in a corresponding dovetail section groove in a tibia area guide, and an inclined front end; an operating lever pivotally mounted adjacent a rear end of the elongate body for pivotal movement between a forward open position and a rearward closed position; and an operating rod adapted to be received in the groove in the elongate body and pivotally attached at a rearward end thereof to the operating lever, the operating rod having at a forward end thereof a pair of aligned transverse projections for cooperation with the inclined front end of the elongate body and a pressure portion on its under side; whereby upon inserting the dovetail section of the elongate body in a corresponding dovetail section of a tibia area guide and pivoting the operating lever to its rearward 47 F037 closed position the operating rod may be drawn rearwardly along the groove so as to cause the transverse projections to move down the inclined front end and press the pressure portion against the tibia area guide to hold the tibia area guide firmly on the tool.
22. A femur jig for use in surgical preparation of a femur of a patient in readiness for implantation of a femoral implant having a bearing surface for bearing on a meniscus of a tibial implant, an anterior peg and a posterior peg for insertion in corresponding holes drilled in a condyle of the patient's femur, and a medial fin for receipt in a substantially anterior-posterior slot cut in the condyle of the patient's femur, the jig comprising: a web portion having a forward end for insertion in a surgically prepared slot in a condyle of the femur of the patient, the jig having on a rearward portion thereof means for facilitating gripping by a femur jig insertion tool.
23. A femur jig according to claim 22, further comprising a body portion including means for cooperation with a surgical tool.
24. A femur jig according to claim 23, wherein the web portion extends downwardly and forwardly from the body portion and wherein the body portion is provided with a bore whose axis lies substantially in the plane of the fin means, the bore being adapted to act as a guide for a drill for drilling a first hole in the femur of the patient for receipt of a posterior peg of a femoral implant.
25. A femur jig according to claim 23, wherein the web portion extends downwardly and forwardly from the body portion, wherein a rod portion is integrally formed with the fin means and has an axis which lies substantially in the plane of the web portion, the rod portion being adapted for insertion in a first hole drilled in the femur of a patient 48 F037 intended for eventual receipt of a posterior peg of a femoral implant, wherein the body portion is provided with a bore whose axis lies substantially in the plane of the web portion, the bore having an axis substantially parallel to that of the rod portion and being adapted to act as a guide for a drill for drilling a second hole in the femur of the patient for receipt of an anterior peg of a femoral implant.
26. A femur jig according to claim 23, wherein the web portion is integrally formed with a rod portion which has an axis that lies substantially in the plane of the web portion for insertion in a first hole drilled in the femur intended for eventual insertion of a posterior peg of a femoral implant, and wherein the body portion comprises a flange integrally formed with a lower part of the web portion and having a transverse surface substantially orthogonal to the plane of the web portion for guiding a saw blade during making a posterior cut in the femur of a patient.
27. A femur jig according to claim 22, wherein the web portion is integrally formed with first and second rod portions whose axes are substantially parallel to one another and are adapted for insertion in corresponding posterior and anterior holes drilled in a femur of a patient intended for eventual receipt of posterior and anterior pegs respectively of a femoral implant, and wherein the web portion is adapted so that, after insertion in the surgically prepared slot in the condyle to a depth corresponding to the depth to which the medial fin of the femoral implant will eventually be implanted, it extends from the slot to a rearward edge which is shaped so as to extend substantially parallel to the corresponding locus of the bearing surface after eventual implantation of the femoral implant, the rearward edge being adapted to serve as a template for a surgical burr for resection of bone of the 49 F037 condyle in readiness for insertion of the femoral implant.
28. A femur jig for use in surgical preparation of a femur of a patient in readiness for implantation of a femoral implant comprising: a body portion having on a rearward side thereof a projecting web portion provided with means for facilitating gripping by a femur jig insertion tool and provided with a pair of substantially parallel forwardly projecting rod portions for insertion in respective posterior and anterior holes drilled in a condyle of the femur of the patient for eventual reception of posterior and anterior pegs of a femoral implant, the body portion being further provided with a slot extending from a rear face to a forward face thereof extending from top to bottom of the body portion for receipt of a saw blade for extending a surgically prepared slot in the condyle that extends from behind the posterior hole at least as far as the anterior hole.
29. A femur jig according to any one of claims 22 to 28, wherein the means for facilitating gripping by a femur jig insertion tool comprises an indent.
30. A femur jig insertion tool for insertion into a surgically prepared slot in a condyle of a femur of a patient comprising: an elongate tool body having (i) a channel in an upper surface thereof defined by side walls, (ii) a jig-receiving slot at its forward end for receipt of a web portion of a femur jig, the web portion having an indentation therein, and (iii) a lateral slot in each side wall of the channel having an open upper end and a rear surface that is inclined downwardly towards the rear of the channel) an operating rod having a shaped forward end adapted for reception in the indentation in the web portion of the femur jig and a lateral projection on each side of the F037 operating rod for reception in a lateral slot; and operating lever means pivotally mounted on a rearward end of the tool body for drawing the operating rod rearwardly along the channel so as to cause the projections to move downwardly and rearwardly as they follow the inclined surfaces of the slots, thereby to cause the shaped forward end to enter the indentation and grip the web portion of a femur jig in the jig-receiving slot.
31. A femoral implant insertion tool comprising; a body having a forward end, a rearward end, an axis extending between the forward and rearward ends, and an internally threaded axial bore; a pair of jaw members each pivotally mounted on the body adjacent the rearward end thereof, having a jaw at a forward end thereof extending inward over a forward end face of the body, and having a ramp surface extending rearward of the body; a handle threadedly engaged in the threaded bore; and a collar on the handle adapted for engagement with the ramp surfaces on the jaw members as the handle is screwed into the body so as to cause the jaw members to pivot inwardly towards the body and the jaws to move inwardly over the front face of the body; whereby, upon placing a bearing surface of a unicompartmental femoral implant against the front surface with the jaws retracted and rotating the handle so as to cause the jaw members to pivot inwardly, the unicompartmental femoral component may be gripped firmly during implantation into a surgically prepared condyle of a femur of a patient.
32. A tibial implant insertion tool comprising; a body having a front end, a rear end, an axis extending between the front and rear ends, and an axial 51 F037 internally threaded bore; a ledge at its front end; a gripping arm pivotally mounted to the body adjacent the rear end of the body and having a forward end provided with a pressure pad and a ramp surface extending rearwardly of the body; a handle threadedly engaged in the bore in the body; and a collar mounted on the handle and adapted to bear on the ramp surface on the gripping arm as the handle is screwed into the body so as to cause the gripping arm to pivot inwardly towards the body and the pressure pad to move towards the ledge; whereby, upon placing a metal plate of a unicompartmental tibial implant against the ledge with the gripping arm retracted and rotating the handle so as to cause the gripping arm to pivot inwardly towards the body and the pressure pad to contact a meniscus of the unicompartmental tibia implant, the unicompartmental tibial component may be gripped firmly during implantation onto a surgically resected upper surface of the patient's tibia.
33. A method of effecting implantation in a knee of a patient of a unicompartmental knee prosthesis comprising (i) a tibial implant comprising a metal backing plate and a meniscus of a biocompatible plastics material and (ii) a femoral implant having a polished front bearing surface for bearing on the meniscus, an anterior peg and a posterior peg on its rear side for receipt in surgically prepared holes in a femur of a patient, and a fin on the rear side in alignment with the anterior and posterior pegs, the method comprising the steps of: resecting an upper end portion of the tibia of the patient to provide a bearing surface for the metal plate of 52 F037 the tibial implant; cutting a slot in the end of a condyle of the end of the femur in readiness for receipt of a posterior part of the fin of the femoral component; drilling a first hole in the condyle with its axis extending into the slot in readiness for receipt of the posterior peg of the femoral component; drilling a second hole in the condyle with its axis extending into the slot in readiness for receipt of the anterior peg of the femoral component) extending the slot in the anterior direction through the second slot in readiness for receipt of an anterior part of the fin of the femoral component; resecting sufficient bone of the condyle adjacent each side of the slot to provide a bearing surface for a part of the rear side of the femoral component; and making a posterior cut in the condyle to provide a bearing surface for another part of the rear side of the femoral component.