FIELD OF INVENTION

This invention relates to a surgical tool guide for use during an ankle joint replacement surgical procedure performed on a human patient, for guiding a surgical tool used during the surgical procedure. In this specification the term "ankle joint" must be interpreted to mean the synovial hinge joint connecting distal ends of the tibia and fibula in the lower leg with a proximal end of the talus bone in the foot. In this specification the term "first joint bone" must be interpreted to mean a reference to one of the tibia and talus bones of an ankle joint and the term "second joint bone" must be interpreted to mean a reference to the other of the tibia and talus bones. Furthermore, in this specification the term "replacement surgery" and "replacement surgical procedure" must be interpreted sufficiently broadly to include ankle bone resurfacing and ankle bone resurfacing surgical procedure, respectively. SUMMARY OF INVENTION According to the invention there is provided an ankle bone surgical tool guide for use during an ankle joint replacement surgical procedure performed on a human patient, for spacing and spatially orientating a first joint bone and a second joint bone of the patient's ankle joint relative to one another and for guiding at least one surgical tool used during the surgical procedure, the ankle bone surgical tool guide including: a first bone engaging formation in the form of a moulding which is constructed from anatomical data obtained of a region of the first joint bone so as to define complementary locating formations which correspond to anatomical formations of said region of the first joint bone, thereby to provide for secure releasable fitment of the first bone engaging formation to said region of the first joint bone, wherein the profile of said complementary locating formations of the first bone engaging formation conforms to the profile of said corresponding anatomical formations of said region of the first joint bone; a second bone engaging formation in the form of a moulding which is constructed from anatomical data obtained of a region of the second joint bone so as to define complementary locating formations which correspond to anatomical formations of said region of the second joint bone, thereby to provide for secure releasable fitment of the second bone engaging formation to said region of the second joint bone, wherein the profile of said complementary locating formations of the second bone engaging formation conforms to the profile of said corresponding anatomical formations of said region of the second joint bone; and at least one surgical tool guiding formation having a predetermined spatial position and orientation relative to the first and second bone engaging formations, for guiding displacement of the surgical tool relative to at least one of the first joint bone and the second joint bone during the surgical procedure; the ankle bone surgical tool guide being characterised in that the first bone engaging formation and the second bone engaging formation are spatially positioned and orientated relative to one another in a predetermined position and spatial orientation, such that after manipulation of the ankle bone surgical tool guide and the joint bones, in use, to achieve fitment of the first bone engaging formation to the first joint bone and fitment of the second bone engaging formation to the second joint bone, the first joint bone and the second joint bone are consequently orientated in a predetermined spatial orientation relative to one another and relative to the surgical tool guiding formation, thereby to position the surgical tool guiding formation at a predetermined position with respect to said one of the first joint bone and the second joint bone.

In a particular embodiment, the ankle bone surgical tool guide may include an outwardly projecting bone spacing formation which is configured and dimensioned to be inserted into a joint space defined between adjacent ends of the first joint bone and the second joint bone, the bone spacing formation further having a predetermined spatial position and orientation relative to the first and second bone engaging formations, whereby after secure fitment of the first bone engaging formation to said region of the first joint bone and fitment of the second bone engaging formation to said region of the second joint bone, and insertion of the bone spacing formation into said joint space, the bone spacing formation is operable to prise the first joint bone and the second joint bone a predetermined distance apart from one another. The bone spacing formation may have a pair of opposite major sides comprising a first major side which is brought into contact with the end of the first joint bone, in use, and an opposite second major side which is brought into contact with the end of the second joint bone, in use, when the bone spacing formation is inserted into the joint space. The first bone engaging formation may be at least partially defined on the first major side of the bone spacing formation. The second bone engaging formation may be at least partially defined on the second major side of the bone spacing formation. The surgical tool guiding formation of the ankle bone surgical tool guide may be in the form of one of a bone cutting guide for guiding a surgical bone cutting tool; a drill guide for guiding a surgical bone drilling tool; a marking guide for guiding a surgical bone marking tool; and a pin placement guide for guiding insertion of a surgical reference pin into one of the first joint bone and the second joint bone.

BRIEF DESCRIPTION OF THE DRAWINGS Further features of the invention are described hereinafter by way of a non-limiting example of the invention, with reference to and as illustrated in the accompanying diagrammatic drawings. In the drawings:

Figure 1 shows a fragmentary perspective view of a patient's ankle joint;

Figure 2 shows a perspective view of a prosthetic ankle joint;

Figure 3A shows a fragmentary perspective view of the ankle joint of Figure 1 , illustrating cut joint locating faces cut into the ankle joint of Figure 1 , for fitting the prosthetic ankle joint of Figure 2, thereto;

Figure 3B shows a side view of a prior art tibial alignment guide and ankle bone cutting guide for guiding the cutting of the joint locating faces of Figure 3A; Figure 4 shows a fragmentary perspective view of the prosthetic ankle joint of Figure 2, shown fitted to the cut joint locating faces of the cut ankle joint shown in Figure 3A;

Figure 5 shows a perspective view of a surgical tool guide, in accordance with the invention, shown fitted to an ankle joint; Figure 6 shows a perspective view of the surgical tool guide of Figure 5, shown after a part of the guide has been removed and showing a surgical guiding tool being guided by the surgical tool guide; Figure 7 shows a perspective view of the surgical tool guide of Figure 6, illustrating an inner side of the surgical tool guide of Figure 6; and

Figure 8 shows a sectional side view of the surgical tool guide of Figure 5, sectioned along section lines VIII - VIII of Figure 5.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 of the drawings shows an ankle joint of a human patient. The ankle joint is a synovial hinge joint connecting distal ends of a tibia 12 and a fibula 13 in a lower leg with a proximal end of a talus 14 bone of a foot of the human patient.

In order to restore functionality to a damaged ankle joint, a prosthetic ankle joint is fitted to the tibia and talus bones of the damaged ankle joint during an ankle joint replacement surgical procedure. Many different types of ankle prostheses are available, each having different configurations and fitment procedures. One example of a known prosthetic ankle joint is illustrated in Figure 2 of the drawings and is designated generally by the reference numeral 2. The prosthetic ankle joint 2 includes a tibial component 3, a talar component 4 and a meniscal bearing component 5. The tibial component 3 is disc shaped and has a pair of outwardly projecting tibial locating pegs 7 for locating the tibial component 3 with respect to the tibia 12, as will be explained in more detail herein below. The talar component 4 has a curved shape and has a pair of outwardly projecting talar locating pegs 6 for locating the talar component 4 with respect to the talus 14. The meniscal bearing component 5 is configured to fit between the tibial component 3 and the talar component 4 and to permit sliding motion of the tibial component 3 and the talar component 4 relative to one another. Figure 3A shows an ankle joint which has been prepared to receive the prosthetic ankle joint 2. More specifically, Figure 3A shows a number of joint locating faces which have been cut into the tibia 12 and talus 14 to provide for the secure fitment and alignment of the tibial component 3 and the talar component 4, relative to the tibia 12 and the talus 14, respectively. It will be understood that the joint locating faces serve to orientate and align the prosthetic ankle joint 2 relative to the tibia 12 and talus 14, in an orientation which approximates the anatomical normality of the patient's ankle joint. The joint locating faces shown in Figure 3A of the drawings include a tibia box cut 8 which removed a block of bone (the end of the removed bone is illustrated by broken lines in Figure 3A of the drawings); a pair of keyhole cuts 9 and a talar cut 1 1 .

In order to guide the cutting of the joint locating faces, a tibial alignment guide and ankle bone cutting guide is used. Figure 3B illustrates a typical tibial alignment guide and ankle bone cutting guide which is designated generally by the reference numeral 1 . The tibial alignment guide and ankle bone cutting guide is used to align the cuts made to the bones of the ankle joint. The guide 1 includes an elongate shaft 13 having a proximal clamp 21 connected at an upper end thereof, which is clamped to the leg, in use, as shown in Figure 3B of the drawings. The guide 1 further includes a mounting formation 17 for mounting one of a tibial cutting block (not shown) and a talar cutting block 19 thereto, for guiding the cutting of the tibia and talar bones, respectively. The guide 1 further has tensioning means for regulating the positions of cuts made to the bone so as to regulate the tension of the replacement joint. In use, prior to cutting the bones, the patient's foot is moved into its neutral flexion position (as shown in Figure 3B of the drawings) wherein dorsiflexion is 0° and plantarflexion is 90° between a longitudinal axis "y" of the tibia and a plantar aspect "z" of the foot.

A known disadvantage of the tibial alignment guide and ankle bone cutting guide 1 is that the fitment of the guide 1 requires estimation on the part of the surgeon. More specifically, the surgeon is required to align a longitudinal axis "x" of the elongate shaft 13 of the guide 1 so as to be parallel with respect to a longitudinal axis "y" of the tibia. This is difficult to estimate visually and a common error which is made is to align the longitudinal axis "x" of the elongate shaft 13 with the front of the tibia, i.e. instead of alignment with the longitudinal axis "y" of the tibia.

Figure 4 shows the prosthetic ankle joint 2 of Figure 2 fitted to the cut joint locating faces cut into the tibia 12 and talus 14. It will be appreciated that it is critical to cut the joint locating faces in the tibia 12 and talus 14 in a manner which will provide for the optimal alignment and fitment of the prosthetic ankle joint 2, so as to approximate the anatomical normality of the patient's ankle joint, after fitment of the prosthetic ankle joint 2 to the patient.

With reference to Figures 5 to 8 of the drawings, an ankle bone surgical tool guide, in accordance with the invention, is designated generally by the reference numeral 10. The guide 10 is configured for use during an ankle joint replacement surgical procedure performed on a human patient, for spacing and spatially orientating a first joint bone in the form of a tibia 12 and a second joint bone in the form of a talus 14 of a patient's ankle joint relative to one another and for guiding a surgical tool used during the surgical procedure.

As is best shown in Figures 5 and 8 of the drawings, the surgical tool guide 10 comprises, broadly, a guide body 15 including a first bone engaging formation in the form of a first moulding 16; a second bone engaging formation in the form of a second moulding 25; a bone spacing formation in the form of a tongue formation 18 projecting outwardly from the guide body 15 and a pair of guide blocks 20 fixed to the guide body 15.

The first moulding 16 is best illustrated in Figure 8 of the drawings. The first moulding 16 is constructed from anatomical data obtained from the patient's ankle joint prior to surgery. More specifically, the first moulding 16 is constructed prior to the surgical procedure, from anatomical data obtained by means of a radiographic scan of the bones of the patient's ankle joint, from which scan, a three-dimensional model (not shown) of the ankle joint is constructed. The first moulding 16 defines complementary locating formations 22 which correspond to anatomical formations 24 defined on the tibia 12. The locating formations 22 provide for secure fitment of the first moulding 16 to the distal end region of the tibia 12 in a specific position. More particularly, when the first moulding 16 is fitted to the tibia 12, the profile of the locating formations 22 of the first moulding 16 conform to the profile of corresponding anatomical formations 24 of the tibia 12.

The second moulding 25 is best illustrated in Figure 8 of the drawings. The second moulding 25 is constructed from anatomical data obtained from the patient's ankle joint prior to surgery. More specifically, the second moulding 25 is constructed prior to the surgical procedure, from the anatomical data obtained by means of the radiographic scan and the three-dimensional model of the ankle joint. The second moulding 25 defines complementary locating formations 29 which correspond to anatomical formations 31 defined on the talus 14. The locating formations 29 provide for secure fitment of the second moulding 25 to the end region of the talus 14 in a specific position. More particularly, when the second moulding 25 is fitted to the talus 14, the profile of the complementary locating formations 29 of the second moulding 25 conform to the profile of corresponding anatomical formations 31 of the talus 14. The tongue formation 18 is configured and dimensioned to be inserted into a joint space 26 defined between adjacent ends of the tibia 12 and the talus 14, as illustrated in Figure 8 of the drawings. The tongue formation 18 has a pair of opposite major sides comprising a first major side 28 which is brought into contact with the end of the tibia 12, in use, and an opposite second major side 30 which is brought into contact with the end of the talus 14, in use, when the tongue formation 18 is inserted into the joint space 26, as shown in Figure 8 of the drawings. The first moulding 16 is partially defined on the first major side 28 of the tongue formation 18. The second moulding 25 is defined on the second major side 30 of the tongue formation 18. The tongue formation 18 has a predetermined spatial position and orientation relative to the first and second mouldings 16, 25 and is integrally formed therewith. More specifically, the predetermined spatial position and orientation of the tongue formation 18 relative to the first moulding 16 and the second moulding 25 is determined from the anatomical data obtained by means of the radiographic scan of the ankle and from the three-dimensional model.

In use, after secure fitment of the first moulding 16 to said region of the tibia 12 and fitment of the second moulding 25 to said region of the talus 14 and after insertion of the tongue formation 18 into the joint space 26, as illustrated in Figure 8 of the drawings, the tibia 12 and the talus 14 are orientated in a predetermined spatial orientation relative to one another and relative to the guide blocks 20 thereby to locate the guide blocks 20 at predetermined positions with respect to the tibia 12 and the talus 14, for reasons which will be explained in more detail hereinbelow. As illustrated in Figure 8 of the drawings, the tongue formation 18 is operable to prise the tibia 12 and the talus 14 a predetermined distance apart from one another, for reasons which will be explained in more detail hereinbelow. The guide blocks 20 comprise the tibial guide block 20.1 and the talar guide block 20.2. The tibial guide block 20.1 and the talar guide block 20.2 each have a predetermined spatial position and orientation relative to the first and second mouldings 16, 25 which is determined when the guide 10 is constructed from the anatomical data obtained by the radiographic scan of the ankle and from the three-dimensional model. The tibial guide block 20.1 is integrally formed with the moulding 16. The tibial guide block 20.1 and the talar guide block 20.2 are releasably connectable to one another by means of a pair of dove-tail joints 27, as shown in Figure 5 of the drawings.

The tibial guide block 20.1 defines a pair of surgical tool guiding formations in the form of drill guides 40, 42. The drill guides 40, 42 are configured to receive a surgical guiding tool 44 therein, as illustrated in Figures 6 and 7 of the drawings. The surgical guiding tool 44 is configured for guiding a surgical drilling tool (not shown) for drilling a hole into the tibia 12. After the hole is drilled into the tibia, the surgical guiding tool 44 guides the insertion of a surgical reference pin (not shown) into the tibia 12. The applicant envisages that the drill guides 40, 42 will have predetermined spatial positions and orientations relative to the first and second mouldings 16, 25 for guiding drilling and insertion of a pair of surgical reference pins (not shown) into the tibia 12 such that the projecting ends of the reference pins are spatially orientated and configured to serve as guides for guiding and aligning a cutting block (not shown) with respect to the tibia. More specifically, the applicant envisages that the cutting guide block will have guide passages which receive the projecting ends of the reference pins therein, for positioning and spatially orientating the cutting guide block with respect to the tibia 12, for guiding the cutting of the joint locating faces in the tibia 12, including the tibia box cut 8 and the pair of keyhole cuts 9, as illustrated in Figures 3A of the drawings. The talar guide block 20.2 defines a surgical tool guide in the form of a cutting slot 46 for guiding a blade of a surgical bone cutting saw for guiding the cutting of the talar cut 1 1 , as illustrated in Figure 3A of the drawings. The talar guide block 20.2 has a predetermined spatial position and orientation relative to the first and second mouldings 16, 25. As such, the cutting slot 46 also has a predetermined spatial position and orientation relative to the first and second mouldings 16, 25.

In use, the guide body 15 and the foot of the patient is manipulated by the surgeon to achieve fitment of the first and second mouldings 16, 25 to the tibia 12 and talus 14, respectively, and insertion of the tongue formation 18 into the joint space 26, as illustrated in Figure 8 of the drawings. In use, after fitment of the first and second mouldings 16, 25 to the ankle bones, and after insertion of the tongue formation 18 into the joint space 26, the foot is in its neutral flexion position (which position is shown in Figure 3B of the drawings). Furthermore, the tibia 12 and talus 14 are spaced an optimal, predetermined distance apart from one another. Also the cutting slot 46 will be optimally aligned with respect to the talus 14, so as to guide the cutting of the talar cut 1 1 for optimal alignment of the prosthetic ankle joint 2 relative to the ankle bones. It will thus be appreciated that the tongue formation 18 ensures that the tibia 12 and talus 14 are correctly spaced a predetermined distance apart from one another, prior to the guided cutting of the patient's bones. It will be appreciated that the guide 10 thus allows for the guided cutting of the patient's bones without the use of the tibial alignment guide and ankle bone cutting guide 1 , as described hereinabove and as illustrated in Figure 3B of the drawings. As such, the guide 10 thus does away with the need for estimation of the longitudinal axis "y" of the tibia 12, as is the case with the use of the tibial alignment guide and ankle bone cutting guide 1 . Accordingly, the applicant envisages that this is advantageous as the possibility of incorrect estimation of the longitudinal axis "y" of the tibia 12 by the surgeon, is eliminated when the guide 10 is used during the surgical procedure. Furthermore, the applicant envisages that the guide 10 is advantageous because the guide 10 does away with the need for the surgeon to estimate the neutral flexion position, as is required when using the tibial alignment guide and ankle bone cutting guide 1 shown in Figure 3B of the drawings. More specifically, it will be appreciated, in this regard, that after fitment of the guide 10 as described hereinabove and as illustrated in Figure 8 of the drawings, the tibia 12 and the talus 14 are spatially orientated relative to one another in the neutral flexion position.

Furthermore, the applicant envisages that flexibility can be provided to the surgeon, because the applicant envisages that the guide 10 may be used with a number of differently configured talar guide blocks from which the surgeon may select an appropriate one. More specifically, each guide block may have a cutting guide slot in a different position to the position of the guide slot 46 of the talar guide block 20.2. As such, the applicant envisages that the surgeon can thus select the most appropriate talar guide block and mount the selected guide block to the tibial guide block 20.1 by means of the dove tail joint of the guide blocks, which are similar to the dove tail joint 27 illustrated in Figure 5 of the drawings.

It will be appreciated that the exact configuration of the guide 10, in accordance with the invention, may vary greatly while still incorporating the essential features of the invention as described hereinabove. For example, the applicant envisages that, in other embodiments of the invention, the tongue formation 18 may be omitted, and a second moulding similar to the second moulding 25 may be provided for fitment of the guide to other regions of the talus bone, other than the regions adjacent the joint space. It will also be appreciated that other surgical tool guiding formations other than the surgical tool guiding formations described hereinabove, may be provided. For example, marking guides may be provided for guiding marking of the patient's bone with a marking implement. The markings may then serve as a reference to guided cutting of the patient's bone.