GB2441863A

GB2441863A - A Surgical Saw Guide

Info

Publication number: GB2441863A
Application number: GB0717138A
Authority: GB
Inventors: Michael Bullivant
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-09-15
Filing date: 2007-09-04
Publication date: 2008-03-19
Also published as: GB0618153D0; GB0717138D0

Abstract

A surgical saw guide assembly comprising a frame 1 arranged to be detachably mounted on a bone 41 and a saw guide 2 mounted on the frame and movable relative to the frame. An introducer handle 39 is detachably connected to the assembly to allow the surgeon to manipulate the device into position. The frame is rigidly fixed to the bone by fixation pins that extend through holes 12 on the side of the frame. The saw guide block is able to effect five cuts of the distal end of a femur. A knee prosthesis femur component 48 is then attached to the extremely accurately cut bone.

Description

2441863

1

SURGICAL GUIDE

The present invention relates to a surgical guide assembly, a method of preparing a bone for a surgical 5 operation and a method of performing a surgical operation. The present invention is particularly, although not exclusively relevant to knee joints.

According to one aspect of the present invention, a 10 surgical guide assembly comprising a frame arranged, in use, to be detachably mounted on a bone and a surgical guide mounted on the frame and being movable relative to the frame.

15 The guide may be movable in at least one and preferably two or three directions perpendicular to each other. The guide may be pivoted about one axis and preferably two axes that are at an angle to each other. The angle of at least one of the axes relative to the frame may be 20 arranged to be altered.

The assembly may include at least one adjustment mechanism connecting the frame with the guide which mechanism may directly connect the frame and guide.

2 5

The mechanism may include a universal joint for instance extending from the guide to the mechanism.

The mechanism may include a first control member rotatable 30 about a first axis and connected to the guide whereby rotation of the first control member about the first axis causes the portion of the guide to which the first member is connected to move in an arc about the first axis.

The mechanism may include means to alter the extent of the first axis such as to move the extent of the first axis between spaced parallel positions.

The guide may be movable relative to the first control member towards or away from that member.

The mechanism may include a second control member movable relative to the first control member such as by relative rotational movement. Movement of the second member may be arranged to alter the position of the first axis relative to the frame. The second control member may be pivotably movable only relative to the frame. The axis of rotation of the second member may be coincident with or offset from the connection of the first member to the guide.

There may be a plurality of adjustment mechanisms each having any of the aforementioned features. For instance there may be three adjustment mechanisms. The first axes of the two or more adjustment mechanisms may be parallel with each other.

The assembly may have position sensing means arranged, in use, to give an indication of the position of the guide relative to a bone. The sensing means may be used to effect adjustment of the position of the guide relative to the frame for instance by providing information necessary to effect adjustment of at least one adjustment mechanism such as by effecting adjustment of at least one first control member or alternatively or additionally at least one second control member.

The sensing means may be arranged to compare the sensed position with a desired portion such as by comparing electronically the sensed and desired position. The electronic comparison may be arranged to show the alterations required to the control member or members.

The guide may include a location member arranged, in use, to contact the bone. The position of the location member relative to the guide may be adjustable rotationally or translationally or both relative to the guide. The guide may include at least two and preferably three location members. At least two locations members may be movable translationally in parallel directions. At least one location member may be arranged to be detachably engaged by a tool arranged to manipulate the mechanism in place. The or each location member may be detachable from the guide.

The guide may include a plurality of differently angled guideways such as two, three, four or five. At least two guideways may extend in directions that cross each other, for instance in the direction towards the bone or the guideways may cross each other within the guide.

The guide may include alteration means arranged to alter the relative positioning of at least two guideways. The alteration means may be arranged to alter the distance between at least two guideways whilst maintaining the same relative angle between the guideways. The alteration means may comprise at least one spacer. The alteration means may be arranged to alter the relative position of at least two cuter guideways relative to each other to either side of at least one intermediate guideway.

4

The or each guideway may comprise a saw guide such as a slot.

5 The surgical guide assembly may comprise a saw guide assembly such as a knee saw guide assembly. The guide may be arranged, in use, to cut two spaced cuts along either side of a femur in the general elongate extent of the femur or a cut across the femur or at least one cut 10 transverse to the elongate of the femur or any combination thereof.

The present invention also includes a method of preparing to perform a surgical operation comprising detachably 15 mounting a frame on a bone and moving a guide mounted on the frame prior to performing the surgical method.

The present invention also includes a method of performing a surgical operation comprising detachably mounting a 20 frame on a bone and moving a guide mounted on the frame and then performing the surgical operation.

The method may comprise first mounting the frame and then mounting the guide or mounting the combined frame and 25 guide block.

The method may comprise moving the guide in a first linear direction or in a first and second linear direction at right angles to each other or in first, second and third 30 linear directions at right angles to each other or about a first angular movement or about a first and second angular movement or about a first, second and third angular movement or about an axis chat is caused to move by the

5

linear movement or any combination thereof. The angular movement or movements may comprise movement about an axis or axes.

5 The method may comprise comparing the actual position of the guide with a reference position of the guide and altering the actual position to coincide with the reference position. The method may comprise mounting the frame on a bone with the guide at least initially being as 10 close as practical to the reference position and then, after mounting the frame, comparing the position of the guide with a reference position and altering the actual position, if necessary.

15 The method may comprise giving information such as displaying such information on the required alteration to be made to the guide which information may comprise giving information on at least two adjustments to be made at at least one location of the guide.

20

The method may comprise transmitting the actual position of the guide to a computer in order for the actual position to be compared to the required position.

25 The method may comprise predetermining the required position.

The method may comprise using a location member attached to the guide to contact the bone at a location spaced from 30 the guide to assist m locating the position of the guide.

The present invention includes preparing a bone for cutting and performing a cutting operation with the guide.

6

The present invention includes preparing a knee joint for a surgical operation and performing a knee joint operation.

5

The present invention includes any combination of the herein referred to features or limitations.

The present invention can be carried into practice in 10 various ways but one embodiment will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a saw guide block 2 and 15 an associated fixation frame 1;

Figures 2, 3 and 4 are an end, front and sectional view of an adjuster mechanism;

20 Figure 5 is a schematic perspective view of an electronic navigation system 10;

Figure 6 is a schematic perspective view of a patient with a knee joint exposed for operating on;

25

Figure 7 is a perspective view of the saw guide block;

Figure 8 is a perspective view of the fixation frame;

3 0 Figure 9 is a perspective view of the saw guide and the fixation frame showing a detachable introducer handle 39 holding and locating the guide in relation to the frame;

7

Figure 10 is a front coronal view of a distal femur 41;

Figure 11 is a lateral view of the distal femur 41 showing the saw guide fixation frame and introducer handle in 5 position;

Figure 12 is a close up sectional view of Figure 11 showing the region where the cuts are made;

10 Figure 13 is a view of the femur showing the attachment of an implant to the cut portion of the femur;

Figures 14A to 14D are end views showing the position of the axis of rotation of the guide block;

15

Figures 15 and 16 are coronal views of the guide block;

Figures 17 to 19 are distal end views of the guide block, and

20

Figures 20 to 22 are sagital views of the guide block.

The saw guide block is able to effect five cuts of the distal end of a femur 41, as shown in Figure 12. The saw 25 guide 2 is provided with a slot 27 which can guide a cutter through that slot to effect the vertical cut 45. Angular cuts 44 and 46 are made by passing a cutter through respective slots 30 and 29. An upper,

substantially horizontal cut 43 is effected by passing a 3 0 cutter through a slot 8 and a lower, downwardly and rightwardly inclined cut 47 (with respect to the drawing) is effected by passing a cutter through a slot 31. A knee prosthesis femur component 48 is then attached to the

8

extremely accurately cut femur 41, as shown in Figure 13. In an alternative guide (not shown) the slots 8 and 31 are parallel to each other to allow parallel cuts 43 and 47 to be made.

5

The way in which the cuts are made and how they are aligned together with how the guide block assembly 2 is connected to the frame 1 will now be described.

10 Commercially available operating theatres already have surgical electronic navigation systems (ENS).

The ENS is used to identify the patient's anatomical profile of a distal femur knee joint and to establish the 15 ideal size of knee prosthesis for the patient as well as the mechanical axis centres of the distal femur knee joint and the proximal femur head.

Once this routine information has been established, 20 approximate spacer blocks 35 and 36 (which are shown in Figure 7) are incorporated into and attached to the saw guide block in any suitable manner. These spacers 35, 3 6 will alter the spacings of the cuts shown in Figure 12. The frame 1 is then attached to the guide block 2. This 25 is achieved by attaching two adjusters, as shown in Figures 2 to 4, to the left hand side of the frame 1 and one adjuster to the right hand side of the frame 1, when that frame is viewed in Figure 8. The adjusters are attached to plates 25 which are each provided with four 30 fixation holes for the adjusters and each adjuster includes a universal coupling 21 connected between the guide block 2 and the adjuster. A detachable introducer handle 3 9 is detachably connected to the assembly to allow

the surgeon to manipulate the device into the required position. Item 33 is a "T" shaped section of the saw guide block that is laying on its side. The universal couplings 21 and adjusters are permanently attached to 3 3 at the three centre lines of the universal joints 26. The adjuster is permanently attached to the fixation frame 1 with four screws each at 25, as shown in Figure 8. The anterior saw guide 32 in Figure 7 and its spacers 3 5 are detachable. The posterior saw guide 34 and its spacers 3 6 are detachable. The size of the spacers 35 and 36 depend on the size of implant required by the patient but the saw guides 32 and 34 are universal.

An ENS detector 11 is rigidly and permanently attached to the guide block 2, as shown in Figure 1, and allows the electronic navigation system to identify the embodiment and display its position in real time on its display screen relative to the patient as previously identified mechanical axis and anatomical profile.

After surgical exposure of the patient's distal femur 41, as seen in Figure 10, the assembly is presented to the patient's distal femur where contact is made between the assembly and the patient, as seen in Figure 11. The surgeon then adjusts the position of the assembly using the detachable introducer handle 3 9 and being guided by the interactive information from the display 14 of the ENS, as seen in Figure 5. Contact is made between an anterior setting finger 3, as seen in Figure 1, and the distal condyle reference studs 9, as seen in Figure 1, with the femur. When the ENS display 14, shown in Figure 5, indicates the assembly is correctly positioned, the frame 1 is rigidly fixed to the distal end of the

patient's femur 41 by multi fixation pins that extend through a number of fixation holes 12 on either side of the frame 1, as seen m Figure 11.

After fixation of the frame has taken place, the handle 39 is released using the locking handle 40 of Figure 9 and removed if required leaving the fixation frame and the saw guide block assembly attached to the patient.

After completion of this fixation process the anterior finger 3 and the location studs 9 are removed from the saw guide block assembly 2, Figure 1, leaving it totally supported by the adjusters 13, Figure 1, mounted on the support frame 1.

During the rigid fixation procedure it is very likely that the saw guide block assembly will no longer be in the optimum position relative to the mechanical axes of the patient initially indicated by the ENS. This will be confirmed by the visual display of the ENS 14, Figure 5. The embodiment has the facility to finely adjust the saw guide block relative to the frame to the original optimum position indicated by the ENS. This is done by one or more of the multiple adjusters 13 shown in Figure 1. These adjusters provide the ability for a surgeon to make fine adjustments to the position of the saw guide block for rotational and linear translation to correct any mechanical axis alignment cr positional errors that have occurred during the rigid fixation process. These adjustments comprise the following movements:-

11

1. Proximal and distal movement of the guide block along the axis of the femur together with rotation about the axis of the femur in the sagital plane.

5 2. Anterior and posterior movement of the saw guide block normal to the axis of the femur together with rotation about this axis in the sagital plane.

3. Rotation in the coronal plane.

10

The embodiment is adjusted for position by the surgeon who is guided by the electronic navigation system (ENS) 10. The ENS 10 uses the tracking marker 11, Figure 1, which is rigidly fixed to the saw guide block assembly 2, Figure 1. 15 The ENS is tracking the position of the saw guide block 2 in real time relative to the patients' anatomy by the use of stereo detector head 22, Figure 5, and is able to calculate the adjustment needed to correct the errors incurred during the fixation process. The ENS 10 displays 20 these errors to the surgeon on the display 14 along with the adjuster setting required to correct the position of the saw guide block 2 back into the optimum position. This information is in the form of letters or numbers or symbols or a combination and these are marked on the 25 adjuster setting wheels 23 and 24 as shown in Figure 3. Other methods of detection could be used.

These adjusters use one or more circular or polygon indicators marked with letters or numbers or symbols or a 30 combination to permit the surgeon to make the adjustments necessary to optimise the position of the saw guide block relative to the optimum mechanical axes of the patient. The ENS is able to determine the option position of the

12

femur component implant in relation to the mechanical axis and anatomical profile of the patient:.

The ENS is also aware of the saw guide block position relative to this optimum position and therefore any-positional errors that exist between the two.

The ENS is therefore able to calculate the adjustment settings needed to bring the saw guide block back into the optimal position therefore allowing it to make the saw cuts on the distal femur 41, as shown in Figure 12, and the correct position to ensure the correct placement of the knee prosthesis femur component 48 shown in Figure 13. The surgeon manipulates the setting wheels 23 and 24 as shown in Figure 3 on the adjusters 13 that match the letters or numbers or symbols to correspond with the setting requirements indicated by the ENS display 14 shown in Figure 5.

The adjusters use a principal of an eccentric bush 16, Figure 4, or eccentric crank 17, Figure 4, or a combination of both to adjust the relative position of the saw guide block assembly 2, Figure 7, to the distal end of the patients' femur 15, Figure 6.

One or more cylindrical bearing blocks 18, Figure 4, are attached to the frame I, Figure 8, on the support brackets 25 using fixing holes 37, Figure 8.

Into the plain bore of the bearing block 18, Figure 4, is inserted a bush with an eccentrically positioned bore 16, Figure 4.

13

This eccentric bore bush 16 has the ability to rotate within the bearing block 18 and be fixed in an index able range of rotational positions by means of a ball locator 19, Figure 4. These rotational positions correspond to 5 the setting positions provided by the ENS display 14, Figure 5 to the surgeon for adjustment of the saw guide block 2, Figure 1.

Fitting into the bore of the eccentric bush is an 10 eccentric crank shaft 17, Figure 4. This crank shaft 17 has the ability to rotate independently of the bush 16 and it also has the ability to have its rotation fixed in a range of rotational positions by means of a locator 20, Figure 4. These positions correspond to the setting 15 positions provided by the ENS display 14 to the surgeon for adjustment of the saw guide block 2.

The multipoint attachment between the saw guide assembly 2 and the adjuster assembly 13 is by a universal coupling.

20

Each adjuster assembly 13, Figure 1 has the ability to place the crank pin of the universal coupling 21, Figure 4 in a combination of radial positions relative to the centre position of the bearing block 18 or in the centre 25 position. Each position is achieved by the rotation of the crank 17 or the bush 16 or a combination of both.

The multi-point suspension of the saw guide block assembly 2 by the universal couplings 21, Figure 4 attached to the 30 adjuster assemblies 13 allow it to be repositioned to ensure that the bone cuts 43, 44, 45, 46 and 47, Figure 12 made on the distal end of the patients' femur 41, Figure

14

11 provide the optimum placement of the knee prosthesis femur component 48, Figure 13.

The number of rotational positions available for selection 5 by the adjusters 13 will be determined by the number of index points available to the eccentric bush 16, Figure 4 and the eccentric crank 17, Figure 4.

The combination of the adjuster positions will produce the 10 rotational or translation or a combination of corrective movements of the saw guide block assembly 2, Figure 7 to remove the positioning errors incurred during the rigid fixation procedure.

15 These corrections of the saw guide block assembly 2, Figure 7 ensure its optimum position for making the saw cuts to the femur.

Figures 14A to 14D show the axis of rotation of the guide 20 block relative to the adjusters in the neutral 12, 3 and 6 o'clock positions respectively. Figures 15 and 16 are top or coronal views showing the saw guide block in a first configuration, in which the adjusters 13A, 13B and 13C are in the neutral positions, for Figure 15 and are at 25 3,9 and 9 o'clock for Figure 16.

Figures 17, 18 and 19 are views looking from the end of the distal end of the femur back towards the proximal end of the femur (hip joint) showing the orientation of the 30 guide block with different positions of the adjusters 13A, 13B and 13C.

Figures 20, 21 and 22 are side or sagital views showing the position of the guide with different portions of the adjusters 13A, 13B and 13C.

Because the ENS is tracking the embodiment position in real time relative to the patient anatomic profile it will then confirm through visual or audio method that the optimum position of the saw guide block has been achieved. The surgeon can now visually check to confirm the acceptability of the positioning of the saw guide block before performing cuts on the distal femur 41.

The cuts are performed using conventional and commercially available flat, rectangular oscillating saw blade 49, attached to hand power tools 50, driven by electricity or compressed gas. The cantilevered cutting edge 6 of the saw is inserted through the slots 8, 27, 29, 30 and 31 in the cutter guide block assembly and when it emerges at the other side it makes contact with the bone to perform the cut required.

The setting finger 3, Figure 1, mounted on the saw guide block assembly 2 is able to rotate about the centre fixing point 28, Figure 7, of its support column 4 and translate along the length of the elongated slot 5. The down turned tip 7 of the finger follows the plane cut by the anterior saw guide slot 8 . The tip 7 is placed onto the anterior surface of the distal femur to enable surgeon to visualise the location of the anterior saw cut that will be made from the saw guide block 32, Figure 7. The distal condyle contact studs 9, Figure 1, are threaded and pass through the chamfer saw guide block 33, Figure 7, and emerge on the opposite side of the saw guide to project a short

16

distance. The projected tips are used to steady the embodiment against the distal femur 41, Figure 10, and allow the surgeon to adjust the embodiment's position toward or away from the distal end of the femur by means of the thread.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any

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novel one, or any novel combination, of the steps of any method or process so disclosed.

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Claims

1. A surgical guide assembly comprising a frame arranged, in use, to be detachably mounted on a bone and a surgical guide mounted on the frame and being movable relative to the frame.

2. The surgical guide assembly according to claim 1, wherein the guide is movable in at least one direction.

3. The surgical guide assembly according to claim 1 or 2, wherein the guide is moveable in at least two directions perpendicular to each other.

4. The surgical guide assembly as in claims 1 to 3, wherein the guide is moveable in at least three directions perpendicular to each other.

5. The surgical guide assembly according to any preceding claim, wherein the guide is pivoted about one axis.

6. The surgical guide assembly according to claim 3 or 4, wherein the guide is pivoted about two axes that are at an angle to each other.

7. The surgical guide assembly according to claim 5 or 6, wherein the angle of at least one of the axes relative to the frame is arranged to be altered.

8. The surgical guide assembly according to any preceding claim, wherein the assembly includes at least

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one adjustment mechanism connecting the frame with the guide.

3. The surgical guide assembly according to claim 8,

wherein the mechanism directly connects the frame and guide.

10. The surgical guide assembly according to claim 8 or 9, wherein the mechanism includes a universal joint.

11. The surgical guide assembly according to claim 10, wherein the universal joint extends from the guide to the mechanism.

12. The surgical guide assembly according to any of claims 8 to 11, wherein the mechanism includes a first control member rotatable about a first axis and connected to the guide whereby rotation of the first control member about the first axis causes the portion of the guide to which the first member is connected to move in an arc about the first axis.

13. The surgical guide assembly according to any of claims 8 to 12, wherein the mechanism includes means to alter the extent of the first axis such as to move the extent of the first axis between spaced parallel posit ions.

14. The surgical guide assembly according to claim 12, wherein the guide is movable relative to the first control member towards or away from that member.

20

15. The surgical guide assembly according to any of claims 12 to 14, wherein the mechanism includes a second control member movable relative to the first control member such as by relative rotational movement.

5

16. The surgical guide assembly according to claim 15, wherein movement of the second member is arranged to alter the position of the first axis relative to the frame.

10 17. The surgical guide assembly according to claim 15

or 16, wherein the second control member is pivotably movable only relative to the frame.

18. The surgical guide assembly according to claim 17, 15 wherein the axis of rotation of the second member is coincident with the connection of the first member to the guide.

19. The surgical guide assembly according to claim 17 or 20 18 in which the axis of rotation of the second member is offset from the connection of the first member to the guide.

20. The surgical guide assembly according to any of 25 claims 8 to 19, wherein there are a plurality of adjustment mechanisms each having any of the aforementioned features.

21. The surgical guide assembly according to any of 30 claims 8 to 20, wherein there are three adjustment mechanisms.

21

22. The surgical guide assembly according to claims 20

or 21, wherein the first axes of the two or more adjustment mechanisms are parallel with each other.

5 23. The surgical guide assembly according to any preceding claim, wherein the assembly has position sensing means arranged, in use, to give an indication of the position of the guide relative to a bone.

10 24. The surgical guide assembly according to claim 23,

wherein the sensing means is used to effect adjustment of the position of the guide relative to the frame.

25. The surgical guide assembly according to claims 24 15 or 23, wherein the sensing means is arranged to compare the sensed position with a desired portion.

26. The surgical guide assembly according to any preceding claim, wherein the guide includes a location

20 member arranged, in use, to contact the bone.

27. The surgical guide assembly according to claim 26, wherein the position of the location member relative to the guide is adjustable rotationally relative to the

25 guide.

28. The surgical guide assembly according to clams 26 or 27 wherein the portion of the location member relative to the guide is adjustable translationally relative to the

3 0 guide.

29. The surgical guide assembly according to any preceding claim, wherein the guide includes at least two

22

location members that are movable translationally in parallel directions.

30. The surgical guide assembly according to claims 26 5 to 29, wherein at least one location member is arranged to be detachably engaged by a tool arranged to manipulate the mechanism in place.

31. The surgical guide assembly according to any 10 preceding claim, wherein the guide includes a plurality of differently angled guideways.

32. The surgical guide assembly according to claim 31, wherein at least two guideways extend in directions that

15 cross each other.

33. The surgical guide assembly according to either of claims 31 or 32, wherein the guide includes alteration means arranged to alter the relative positioning of at

20 least two guideways, the alteration means being arranged to alter the distance between the at least two guideways whilst maintaining the same relative angle between the guideways.

25 34. The surgical guide assembly according to claim 33,

wherein the alteration means comprises at least one spacer.

35. The surgical guide assembly according to any of

30 claims 33 or 34, wherein the alteration means is arranged tc alter the relative position of at least two outer guideways relative to each other to either side of at least one intermediate guideway.

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36. The surgical guide assembly according to any preceding claim in which the surgical guide assembly comprises a saw guide assembly that is arranged, in use,

5 to cut two spaced cuts along either side of a femur in the general elongate extent of the femur.

37. The surgical guide assembly according to any preceding claim in which the surgical guide assembly

10 comprises a saw guide assembly that is arranged, in use, to cut a cut across the femur.

38. The surgical guide assembly according to any preceding claim in which the surgical guide assembly

15 comprises a saw guide assembly that is arranged, in use, to cut at least one cut transverse to the elongate of the femur.

39. A method of preparing to perform a surgical 20 operation comprising detachably mounting a frame on a bone and moving a guide mounted on the frame prior to performing the surgical method.

40. A method of performing a surgical operation 25 comprising detachably mounting a frame on a bone and moving a guide mounted on the frame then performing the surgical operation.

41. The method as claimed in and claims 39 or 40, 3C wherein the method comprises first mounting the frame and then mounting the guide.

42. The method as claimed m claim 3 9 or 40, wherein the method comprises mounting the combined frame and guide block.

43. The method as claimed in claims and 39 to 42, wherein the method comprises comparing the actual position of the guide with a reference position of the guide and altering the actual position to coincide with the reference position.

44. The method as claimed in claim 43, in which the method comprises mounting the frame on a bone with the guide at least initially being as close as practical to the reference position and then, after mounting the frame, comparing the position of the guide with a reference position and altering the actual position, if necessary.

45. The method as claimed in any of claims 39 to 44, in which the method comprises giving information on the required alteration to be made to the guide which information comprises giving information on at least two adjustments to be made at least one location of the guide.

46. The method as claimed in any of claims 39 to 45, in which the method comprises transmitting the actual position of the guide to a computer in order for the actual position to be compared to the required position.

47. The method as claimed in any of claims 39 to 46 in which the method comprises predetermining the required position.

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48. The method as claimed in any of claims 3 9 to 47, in which the method comprises using a location member attached to the guide to contact the bone at a location spaced from the guide to assist in locating the position

5 of the guide.

49. A method of preparing a bone for cutting, the method including performing a cutting operation with the guide.

10

50. A method of preparing a knee joint for a surgical operation, the method including performing a knee joint operation with the guide.

15 51. A surgical guide assembly substantially as herein described and with reference to any of the Figures.

52. A method substantially as herein described,

including a method of operating a surgical guide assembly 20 as herein defined or described and with reference to any of the accompanying drawings.