# Patent

## Title
Method for placing a malleolar implant

## Abstract

A method for implanting a malleolar implant in an ankle joint. A spacer block is positioned between a lower portion of a tibia and an upper portion of an astragalus in the ankle joint. A guide attached to the spacer block is positioned opposite an outer surface of a fibular malleolus. A bore aligned with the guide is formed through the fibular malleolus. The spacer block is removed from between the tibia and the astragalus. A shank of the malleolar implant is engaged with the bore from an inner surface of the fibular malleolus. The shank is advanced into the bore so an inner surface of a head of the malleolar implant engages the inner surface of the fibular malleolus.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a divisional of Ser. No. 10/254,984, filed Sep. 26, 2002, entitled Tool for Placing a Malleolar Implant for Partial or Total Ankle Prosthesis, which is a divisional of Ser. No. 09/631,938, filed Aug. 3, 2000, now U.S. Pat. No. 6,488,712, entitled Malleolar Implant for Partial or Total Ankle Prosthesis and Ancillary Tool for Placing Such an Implant, which claims priority to French application No. 99 10340, filed Aug. 5, 1999, the disclosures of which are all hereby incorporated by reference.


BACKGROUND OF THE INVENTION
The present invention relates to a method for implanting a malleolar implant in an ankle joint, a malleolar implant for a partial or total prosthesis of the ankle, and an ancillary tool for placing such an implant.
DESCRIPTION OF THE RELATED ART
It is known, for example from EP-A-0 864 304, to fit an ankle prosthesis with a malleolar implant that bears against an articular surface of the astragalus, whether it be a natural surface or of a surface of a prosthetic component. During an operation on an ankle, access to the internal articular surfaces is limited by the ligamentary system that does not necessarily allow a sufficient dislocation of the joint. In particular, access to the internal surface of the fibular malleolus may be insufficient, which induces difficulties in positioning the implant, particularly by impaction.
With reference to the embodiments of FIGS. 4 and 5, it is disclosed in EP-A-0 864 304 to introduce an implant from the outer face of the fibula. However, this necessarily limits the surface of the head of this implant, which must be less than or equal to the surface of the orifice provided in the bone, so that it is necessarily of relatively small dimensions with the result that the malleolus is fragile.
For the foregoing reasons, the positioning of the malleolar implants in the known prostheses is not entirely satisfactory.
BRIEF SUMMARY OF THE INVENTION
It is a particular object of the present invention to overcome these drawbacks by proposing a novel method for implanting a malleolar implant in an ankle joint and a malleolar implant which may be positioned precisely, even though access to the internal surface of the fibular malleolus may be limited and whereas its articular head presents dimensions allowing it to perform its function efficiently.
One embodiment is directed to a method for implanting a malleolar implant in an ankle joint. A spacer block is positioned between a lower portion of a tibia and an upper portion of an astragalus in the ankle joint. A guide attached to the spacer block is positioned opposite an outer surface of a fibular malleolus. A bore aligned with the guide is formed through the fibular malleolus. The spacer block is removed from between the tibia and the astragalus. A shank of the malleolar implant is engaged with the bore from an inner surface of the fibular malleolus. The shank is advanced into the bore so an inner surface of a head of the malleolar implant engages the inner surface of the fibular malleolus.
In one embodiment, the spacer block is engaged with natural articular surfaces on one or more of the tibia or the astragalus. In another embodiment, the lower portion of the tibia is resected and the spacer block is engaged with the resected surface. In another embodiment, the upper portion of the astragalus is resected and the spacer block is engaged with the resected surface. In another embodiment, the bore is located so that the head of the malleolar implant is positioned to engage with a prosthetic element in the lower portion of the tibia and/or the upper portion of the astragalus.
In another embodiment, the lower portion of the tibia is resected. At least one shim is releasably attached to the spacer block. The spacer block and the shim are engaged with the resected surface on the lower portion of the tibia. The shim is preferably selected to have a thickness generally corresponding to a thickness of a prosthetic element for the lower portion of the tibia.
In another embodiment, the spacer block and the shim are engaged with the resected surface on the upper portion of the astragalus. The shim is preferably selected to have a thickness generally corresponding to a thickness of a prosthetic element for the upper portion of the astragalus.
The present method optionally includes rotating the guide relative to the spacer block to adjust the position of the bore relative to the fibular malleolus. In one embodiment, the spacer block has surfaces adapted to cooperate with natural articular surfaces or the resected surfaces of at least one of the lower portion of the tibia or the upper portion of the astragalus. The guide is optionally clamped to the inner and outer surfaces of the fibular malleolus.
An outer convex spherical surface of the head articulates against one or more of the lower portion of the tibia, the upper portion of the astragalus, or prosthetic elements located in the lower portion of the tibia or the upper portion of the astragalus.
The invention also relates to a malleolar implant comprising a head, that bears against the astragalus or an astragalian prosthetic component and a shank provided to be introduced in a bore in the fibula, characterized in that the shank is provided with means for hooking a traction member adapted to be manipulated from the outer side of the fibula, in order to position the shank in the bore.
Thanks to the invention, the implant may be pre-positioned towards the inner face of the fibular malleolus and pulled through the through bore provided in the malleolus, with the result that the surgeon does not have to manipulate the implant with precision inside the joint, i.e. between the fibula and the tibia or between the fibula and the astragalus. The surgeon may exert an efficient effort on the traction member, which may be a flexible tie such as a suture thread, without being hindered by the surrounding bones. As a result, the positioning of the shank of the implant in the bore in the fibula may be precise, in particular due to the fact that the outer diameter of the shank may be substantially equal to the inner diameter of this bore, as the effort of traction which may be exerted from the outside of the fibula may be intense.
According to an advantageous aspect of the invention, the shank is provided with at least one orifice for passage of a flexible tie adapted to be engaged through the bore. In particular, the shank may comprise a plurality of orifices for passage of a flexible tie, such orifices being distributed over the length of this shank.
According to another advantageous aspect of the invention, the shank is provided with means for axial hold inside the bore. These means, which may be formed by outer radial flanges distributed over the length of the shank, make it possible efficiently to immobilize the shank inside the bore after it has been introduced therein by traction on the flexible member or tie.
The invention also relates to an ancillary tool for placing a malleolar implant as described hereinabove and, more specifically, a tool which comprises a spacer block adapted to be inserted between the tibia and the astragalus of an ankle, and a lug extending from one end connected to this spacer block to an opposite end that is oriented in a vicinity of the lateral surface of the fibular malleolus when the spacer block is in place between the tibia and the astragalus, this lug supporting a guide for boring the fibular malleolus in a medio-lateral direction.
Thanks to the invention, the bore of the fibular malleolus may be effected from its outer surface and in the direction of its inner surface, with a determined relative positioning with respect to the tibia and the astragalus, with the result that the position of the malleolar implant in place in this bore is determined with precision with respect to the respective articular surfaces of the astragalus or of the tibia or of corresponding prosthetic components. The spacer block may be provided to cooperate with natural articular surfaces of the tibia and/or of the astragalus or with surfaces created by resection of these bones, in the case of placing a total ankle prosthesis.
According to an advantageous aspect of the invention, the spacer block is provided with a housing for receiving a shim of thickness adapted to the distance between the lower surface of the tibia and upper surface of the astragalus. This aspect of the invention makes it possible to maintain a distance corresponding to that which will be subsequently created by the prosthetic elements mounted in the lower part of the tibia and in the upper part of the astragalus, when the position of the malleolar implant is determined.
According to another advantageous aspect of the invention, the lug is articulated on the spacer block, with a limited possibility of pivoting. This makes it possible to adjust the position of the malleolus bore guide about the pivot axis of the lug with respect to the spacer block. In that case the spacer block and the lug are advantageously provided with orifices for passage of a common pivot pin.
It is also possible for the bore guide to be associated with a device for clamping the malleolus against a bearing surface formed on the lug or the spacer block. This allows a firm immobilization of the fibular malleolus during boring and thus ensures precision of the boring operation.



BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
The invention will be more readily understood on reading the following description of an embodiment of a malleolar implant and its ancillary tool according to the invention, given solely by way of example and with reference to the accompanying drawings, in which:
FIG. 1 is a view in perspective of an implant according to the invention.
FIG. 2 is a view in perspective of the implant of FIG. 1 during positioning in a fibular malleolus, shown with parts torn away.
FIG. 3 schematically shows, with parts torn away, an ancillary tool for placing the implant of FIG. 1, in the course of use.
FIG. 4 is a view in perspective of the tool of FIG. 3, from underneath.



DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, the implant 1 shown in FIGS. 1 and 2 is intended to be introduced in a bore 2 made in the lateral or fibular malleolus 3. The implant 1 comprises a convex head 4, substantially in the form of a spherical cap and of which the radius of curvature is substantially equal to that of the outer cheek of the astragalus of the ankle in question. The shank 5 of the implant 1 is provided with outer radial flanges 6 of which the outer diameter d6 is substantially equal to the inner diameter d2 of the bore 2.
According to the invention, two orifices 7 are provided in the shank 5 and are capable of receiving a suture thread 8 or other flexible tie. When such a thread is engaged in one of the orifices 7, it is possible to exert on the thread 8 an effort of traction T which is transmitted by the thread 8 to the shank 5 as represented by arrow T′ in FIG. 2. In this way, by pulling on the thread 8, the surgeon introduces the shank 5 in the bore 2 without having to exert an effort of thrust on the head 4 which may be difficult to access due to the surrounding ligamentary system.
In other words, it suffices for the surgeon to place a thread in one of the orifices 7, to pass the two strands of the thread 8 in the bore 2 via the inner face of the malleolus, then to pull the strands via the outer side of the malleolus. The traction on the thread 8 has the effect of introducing the shank 5 of the implant 1 in the bore 2 and of applying the head 4 on the bone. The effort of traction T exerted on the thread 8 may be intense and directed parallel to the longitudinal axis X2 of the bore 2, with the result that the shank is efficiently drawn towards the inside of the bore 2. In particular, taking into account the direction and intensity of the effort of traction T, the diameters d2 and d6 can be provided to be substantially equal, with the result that the shank 5 is firmly maintained in place after having been positioned.
The shank 5 is provided with two bores 7 distributed along its axis X5, the bore 7 nearest the end 5a of the shank 5 being used. The fact that the shank 5 comprises a plurality of orifices 7 makes it possible to use an orifice 7 relatively close to the end 5a of the shank 5 and to avail of such an orifice including when the shank 5 is cut in order to adapt its length to the thickness e of the malleolus 3. The number of bores 7 may, of course, be increased if necessary.
The bore 2 is made via the outer face 3a of the malleolus 3 with the aid of the ancillary tool shown in FIGS. 3 and 4. This tool 10 comprises a spacer block 11 provided to be disposed between the tibia T and the astragalus A of an ankle to be fitted with the implant 1. The block 11 comprises a substantially planar upper surface 12 intended to cooperate with a planar surface created by resection of the distal end of the tibia. The lower surface 13 of the block 11 is formed by two planar surfaces 13a and 13b inclined with respect to each other by an angle α, the surfaces 13a and 13b being provided to bear respectively on corresponding surfaces created by resection of the upper face of the astragalus A.
The surface 12 of the block 11 comprises a C-shaped housing 14 intended to receive a shim 15 of which the upper surface 16 is in contact with the lower surface of the tibia T. The thickness E of the shim 15 shown in FIG. 3 is such that its upper surface 16 is flush with the upper surface 12 of the block 11.
However, thicker shims may be used when the distance E′ between the lower surface of the tibia and upper surface of the astragalus is greater than in the configuration shown in FIG. 3.
The block 11 defines a housing 17 for receiving the end 20 of a substantially C-shaped lug 21. The end 20 is provided with a bore (not shown) which, in the configuration of FIGS. 3 and 4, is aligned with a bore 18 made in the block 11 and passing downwardly through this block, i.e. connecting the surfaces 12 and 13. A screw 19 may be introduced in this bore which is at least partially tapped, this making it possible to immobilize the end 20 of the lug 21 inside the housing 17. In practice, the clearance made when the screw 19 is tightened allows a limited pivoting about axis X18 of the bore 18.
At its end 22 opposite the end 20, the lug 21 supports a clamping system 23 adapted to be manipulated because of a knurl 24 and making it possible to apply the malleolus 3 of the fibula P against a stop 25 formed on an extension 26 of the end 20 of the lug 21. A longitudinal axis of these clamping means is shown at X23. The clamping means 23 are hollow, with the result that a drill 30 may be introduced at the outer face 3a of the malleolus 3 in order to make the bore 2 from the outside towards the inside of the malleolus 3. In this way, the surgeon may easily aim at the suitable part of the malleolus 3 because of the clamping means 23 which also constitute a bore guide for the drill 30.
As the lug 21 is capable of pivoting about axis X18, the position of axis X23 is variable in pivoting about this axis X18, which makes it possible optimally to adjust the orientation of the bore 2 as a function of the exact geometry of the malleolus 3. β denotes the maximum angle of pivoting of the axis X23 about axis X18. In practice, the angle β is of the order of 10°.
Thanks to the tool 10, a bore 2 may therefore be formed from the outside, allowing a rapid and efficient implantation of the implant 1.
When shims 15 of thickness greater than those shown in FIG. 2 are used, they can be provided to overlap the bore 18, as the screw 19 is placed in position before positioning of the shim 15 which is effected during operation as a function of the distance E′.
The invention has been shown with a total ankle prosthesis, which corresponds to the geometry of the surfaces 12 and 13 of the block 11.
However, it is also applicable to a partial ankle prosthesis, without modification of the implant 1, the ancillary tool in that case being adapted to the geometry of the anatomical articulation surfaces between the tibia and the astragalus.

## Claims

1. A method for implanting a malleolar implant in an ankle joint, the method comprising the steps of:
positioning the spacer block between a lower portion of a tibia and an upper portion of an astragalus in the ankle joint;
positioning a guide attached to the spacer block opposite an outer surface of a fibular malleolus;
forming a bore aligned with the guide through the fibular malleolus;
removing the spacer block from between the tibia and the astragalus;
engaging a shank of the malleolar implant with the bore from an inner surface of the fibular malleolus; and
advancing the shank into the bore so an inner surface of a head of the malleolar implant engages the inner surface of the fibular malleolus.

2. The method of claim 1 comprising engaging the spacer block with natural articular surfaces on one or more of the tibia or the astragalus.

3. The method of claim 1 comprising the steps of:
resecting the lower portion of the tibia; and
engaging the spacer block with the resected surface on the lower portion of the tibia.

4. The method of claim 1 comprising the steps of:
resecting the upper portion of the astragalus; and
engaging the spacer block with the resected surface on the upper portion of the astragalus.

5. The method of claim 1 comprising the steps of:
resecting the lower portion of the tibia;
locating the bore so that the head of the malleolar implant is positioned to engage with a prosthetic element in the lower portion of the tibia.

6. The method of claim 1 comprising the steps of:
resecting the upper portion of the astragalus; and
locating the bore so that the head of the malleolar implant is positioned to engage with a prosthetic element in the upper portion of the astragalus.

7. The method of claim 1 comprising the steps of:
resecting the lower portion of the tibia;
releasably attaching at least one shim to the spacer block; and
engaging the spacer block and the shim with the resected surface on the lower portion of the tibia.

8. The method of claim 7 comprising the step of selecting the shim to have a thickness generally corresponding to a thickness of a prosthetic element for the lower portion of the tibia.

9. The method of claim 1 comprising the steps of:
resecting the upper portion of the astragalus;
releasably attaching at least one shim to the spacer block, the shim having a thickness generally corresponding to a thickness of a prosthetic element for the upper portion of the astragalus; and
engaging the spacer block and the shim with the resected surface on the upper portion of the astragalus.

10. The method of claim 9 comprising the step of selecting the shim to have a thickness generally corresponding to a thickness of a prosthetic element for the upper portion of the astragalus.

11. The method of claim 1 comprising rotating the guide relative to the spacer block to adjust the position of the bore relative to the fibular malleolus.

12. The method of claim 1 comprising adjusting a distance between the lower portion of the tibia and the upper portion of the astragalus by releasably attaching at least one shim to the spacer block.

13. The method of claim 1 comprising selecting a spacer block with at least two lower planar surfaces.

14. The method of claim 1 comprising selecting a spacer block with surfaces adapted to cooperate with natural articular surfaces of at least one of the lower portion of the tibia or the upper portion of the astragalus.

15. The method of claim 1 comprising selecting a spacer block with surfaces adapted to cooperate with surfaces created by resection of at least one of the lower portion of the tibia or the upper portion of the astragalus.

16. The method of claim 1 comprising clamping the guide to the inner and outer surfaces of the fibular malleolus.

17. The method of claim 1 comprising articulating an outer convex spherical surface of the head against one or more of the lower portion of the tibia or the upper portion of the astragalus.

18. The method of claim 1 comprising articulating an outer convex spherical surface of the head against one or more prosthetic elements located in the lower portion of the tibia or the upper portion of the astragalus.