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 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 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 bone engaging formation to said region of the first joint bone, wherein the profile of said complementary locating formations of the moulding conforms to the profile of said corresponding anatomical formations of said region of the first joint bone; 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 bone engaging formation, whereby after secure fitment of the moulding to said region of the first joint bone and insertion of the bone spacing formation into said joint space, the bone spacing formation is operable to displace the first joint bone and the second joint bone out of their natural relative anatomical positions and to space the first joint bone and the second joint bone relative to one another; and at least one surgical tool guiding formation having a predetermined spatial position and orientation relative to the bone engaging formation, for guiding displacement of the surgical tool relative to the second joint bone during the surgical procedure. 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 bone engaging formation may be at least partially defined on the first major side of the bone spacing formation. The second major side of the bone spacing formation may have a flat planar configuration.

The surgical tool guiding formation 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 the second joint bone.

The ankle bone surgical tool guide may further include at least one additional surgical tool guiding formation, the additional surgical tool guiding formation having a predetermined spatial position and orientation relative to the bone engaging formation and being configure for guiding displacement of a surgical tool relative to the first joint bone. The additional surgical tool guiding formation 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 marking tool; and a pin placement guide for guiding insertion of a surgical reference pin into the first 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 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;

Figure 7 shows a perspective view of the surgical tool guide of Figure 5, illustrating an inner side of the surgical tool guide of Figure 5; 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); and 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 1 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 is that the fitment of the guide 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 the 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, as illustrated in Figure 3 of the drawings. 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 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 surgical tools used during the surgical procedure. As is best shown in Figure 7 of the drawings, the surgical tool guide 10 comprises broadly, a guide body 15 including a bone engaging formation in the form of a moulding 16; 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 moulding 16.

The moulding 16 is best illustrated in Figures 7 and 8 of the drawings. The moulding 16 is constructed from anatomical data obtained from the patient's ankle joint prior to surgery. More specifically, the 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 moulding 16 defines complementary locating formations 22 on an inner side thereof which correspond to anatomical formations 24 defined on the tibia 12. The locating formations 22 provide for secure fitment of the moulding 16 to the distal end region of the tibia 12 in a specific position. More particularly, when the moulding 16 is securely and releasably fitted to the tibia 12, the profile of the locating formations 22 of the moulding 16 conform to the profile of corresponding anatomical formations 24 of the tibia 12.

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 moulding 16 is partially defined on the first major side 28 of the tongue formation 18. The second major side 30 of the tongue formation 18 has a flat planar configuration and defines a flat face 32. The tongue formation 18 has a predetermined spatial position and orientation relative to the moulding 16 and is integrally formed therewith. More specifically, the predetermined spatial position and orientation of the tongue formation 18 relative to the moulding 16 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 moulding 16 to said region of the tibia 12 and insertion of the tongue formation 18 into the joint space 26, the tongue formation 18 is operable to displace the tibia 12 and the talus 14 out of their natural relative anatomical positions and to space the tibia 12 and the talus 14 relative to one another. More specifically, the tongue formation 18 spaces the tibia 12 and the talus 14 a relatively greater distance apart from one another, when compared to a distance between the tibia 12 and the talus 14 when the tibia 12 and the talus 14 are in their natural relative anatomical positions.

The pair of guide blocks 20 comprises the tibial guide block 20.1 and the talar guide block 20.2. 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 each have a predetermined spatial position and orientation relative to the moulding 16, 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 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 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 3B of the drawings.

The tibial guide block 20.1 defines a number of additional surgical tool guiding formations in the form of drilling guides 40, 42 and 44 and cutting guide slots 34, 36 and 38. The drilling guides 40, 44 are configured for guiding a surgical drilling tool for guiding the drilling of holes into the tibia 12. The drilling guides 42 are configured for guiding a surgical drilling tool for guiding the cutting of holes into the tibia, from which holes, the pair of key hole cuts 9, as shown in Figure 3A of the drawings, can be cut, in use. The cutting guide slot 34 is configured for guiding a blade of a surgical bone cutting saw (now shown) for guiding the cutting of parts of the tibia 12 between the holes drilled into the tibia 12 which were guided by the drilling guides 40, 44. The cutting slots 36, 38 are configured for guiding the cutting of parts of the tibia 12 between the holes drilled into the tibia 12 which were guided by the drilling guides 40, 44 and the end of the tibia 12, thereby to achieve the tibia box cut 8, as illustrated in Figure 3A of the drawings.

In use, in order to guide the cutting of the patient's bones, the moulding 16 of the guide 10 is securely fitted to the tibia 12 and the tongue formation 18 is inserted into the joint space 26, as illustrated in Figure 8 of the drawings. In use, the patient's foot is then moved into its neutral flexion position (which position is shown in Figure 3B of the drawings) wherein dorsiflexion is 0° and plantarflexion is 90° between the longitudinal axis "y" of the tibia and the plantar aspect "z" of the foot. It will be appreciated that as the guide blocks 20.1 , 20.2 have predetermined spatial positions and orientations relative to the moulding 16, so also the cutting slots 34, 36, 38, 46 and the drilling guides 40, 42, 44 each have a predetermined spatial position and orientation relative to the moulding 16. It will also be appreciated that the positions of the pair of guide blocks 20 are preselected such that after fitment of the moulding 16 of the guide 10 to the tibia and after the patient's foot is displaced into its neutral flexion position, the orientation and configuration of the tibia box cut 8, the pair of key hole cuts 9 and the talar cut 1 1 , will be located in optimal positions and configurations, so as to provide for optimal alignment of the prosthetic ankle joint 2 relative to the tibia 12 and talus 14. It will also be appreciated that the cutting guide slots 34 and 46 will be configured to ensure that cuts made to the patient's bones are guided so as to define cut faces which are particularly parallel with respect to one another when the foot is in its neutral flexion position. Furthermore, the tongue formation 18 ensures that the tibia 12 and talus 14 are correctly spaced relative to 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 1 , as described hereinabove and as illustrated in Figure 3B of the drawings. As such, it will be appreciated that the guide 10 thus does away with the need for estimation of the longitudinal axis of the tibia, 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 of the tibia 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 will also allow a surgeon the possibility of deviating, to some degree, from a pre-operative surgical plan. More specifically, the applicant envisages that the guide 10 will allow a surgeon, prior to cutting the bones, to move the foot out of the neutral flexion position, by altering one or both of the dorsiflexion and plantarflexion, by a predetermined degree of rotation. The applicant envisages that this will allow a surgeon prior to surgery, or during surgery, to devise a "backup plan" whereby the surgeon plans to deviate from the normal fitment position of the prosthetic ankle joint 2. If during surgery, the surgeon determines that the patient's anatomy, such as, for example, the patient's soft tissue anatomy, will be better suited to the backup plan, it will be understood that the guide 10 allows the surgeon to move the foot out of the neutral flexion position by altering one or both of dorsiflexion and plantarflexion, prior to cutting the bone. More particularly, when the patient's foot is moved by the surgeon during surgery, the flat face 32 defined on the second major side 30 of the tongue formation 18 permits the unobstructed articulation of the talus 14 which articulates against the flat face 32 of the tongue formation 18 of the guide 10.

Furthermore, the applicant envisages that further 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 tabular 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.

The applicant has found that the guide 10 is particularly advantageous because it is useful to utilise the moulding 16 to align the guide 10 with respect to the tibia 12, in order to orientate the talar guide block 20.2 with respect to the talus 14. More specifically, the applicant has found that the talus 14 is particularly difficult to access during surgery. Furthermore, the surgeon has only a limited view of the talus 14 during surgery. As such, it is difficult to orientate a guide with respect to the talus during surgery due to the limited access to the talus and the limited visibility of the talus 14 during surgery. 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, whereas in the case of the guide 10, the tibia constitutes the first joint bone and the talus constitutes the second joint bone, in another embodiment (not shown) the talus may constitute the first joint bone and the tibia may constitute the second joint bone. It will also be appreciated that other surgical tool guides other than the surgical tool guides described hereinabove, may be provided. For example marking guides (not shown) may be provided for guiding marking of the patient's bone with a marking implement. The markings may then serve as a reference to guide cutting of the patient's bone. Alternatively or additionally, one or more pin placement guides (not shown) may be provided for guiding insertion of surgical reference pins into one of the joint bones. The applicant envisages that the reference pins can then provide guides for locating a bone cutting guide relative to one or both of the joint bones.