WO1999004734A1

WO1999004734A1 - Drilling part for eliminating surgical cement

Info

Publication number: WO1999004734A1
Application number: PCT/FR1998/001635
Authority: WO
Inventors: Bertrand Bergue
Original assignee: Bertrand Bergue
Priority date: 1997-07-23
Filing date: 1998-07-23
Publication date: 1999-02-04
Also published as: FR2766358B3; FR2766358A1

Abstract

The invention concerns a drilling part (10) comprising at least two mutually axially spaced zones, shaped to be urged to rest against the cement sheath (5) wall; the conduit axis (11, 31) forms a non-null angle with the part (10, 30), corresponding to the angle formed by longitudinal axis of the cavity delimited by the cement sheath (5) with the corporeal cavity (4) longitudinal axis; and said zones and said conduit (11, 31) are mutually positioned such that the conduit (11, 31) axis coincides with the corporeal cavity (4) axis when said zones are resting against the cement sheath (5) wall.

Description

DRILLING PIECE FOR THE REMOVAL OF SURGICAL CEMENT

The present invention relates to a piercing part intended to be used in the context of an operation for removing a sheath of surgical cement, this sheath having been used for sealing a prosthesis of elongated shape in an elongated body cavity. The invention also relates to several methods of manufacturing this piercing part.

The invention is in particular usable in the context of an operation for removing the cement sheath used for fixing a femoral stem of a hip prosthesis in the medullary canal of a femur.

It is sometimes necessary to remove a bone prosthesis to replace it with another more suitable, especially in the event of loosening of this prosthesis or bone degradation. The cement sheath used to seal the original prosthesis must be removed in order to allow proper placement of the new prosthesis. US Patent No. 5,047,035 describes a piercing part allowing such elimination. This part has a shape and dimensions corresponding generally to those of a femoral stem, and comprises a conduit arranged in it, parallel to its longitudinal axis. This conduit allows the drilling of a coaxial hole in the bone for the establishment of a spindle, this spindle being used to guide cannula reamers of increasing diameter, used to carry out the elimination of the sheath. The piercing part according to this prior document has the major drawback of making it possible to bore or perforate the femoral cortex. Indeed, it is very frequent that the longitudinal axis of the prosthesis, and therefore of the cement sheath, is oriented obliquely with respect to the axis of the femoral shaft. This oblique orientation leads to a corresponding orientation of said piercing part, and therefore of the duct, when this part is placed in the medullary canal of the bone, so that this duct directs the piercing tool in the direction of the cortex. This problem is particularly important in the case of a femur since the weakening of the bone resulting from the reaming or perforation of the cortex occurs at a level of the bone where significant stresses are exerted. In addition, the femoral stems of hip prostheses have very variable shapes from one manufacturer to another, to which the piercing part according to this prior document does not correspond perfectly. This results in a risk of defective positioning or mobility of this part during drilling.

These essential problems have not been satisfactorily resolved to date, so that in practice, in most cases, the removal of a cement sheath is carried out manually, using various conventional instruments. (long scissors, gouge, pliers, hooks, reamers, wicks ...). This elimination is long and difficult to carry out, and also creates a risk of perforation or fracturing of the femoral shaft, particularly in the case of a bone which has become fragile.

The invention aims to remedy these problems. The piercing part which it relates has, in a manner known per se, a shape such that it can be engaged in the cavity delimited by the cement sheath after removal of the prosthesis, and comprises a conduit arranged in it, this conduit allowing the drilling of a hole for guiding or passing tools used to carry out the elimination of the sheath. According to the invention, - Said part comprises at least two mutually axially distant zones, shaped to bear tightly against the wall of the cement sheath;

The axis of the conduit forms a non-zero angle with the longitudinal axis of the part, corresponding to the angle formed by the longitudinal axis of the cavity which the cement sheath delimits with the longitudinal axis of the body cavity, and

- Said zones and said conduit are mutually positioned so that the axis of the conduit coincides with one longitudinal axis of the body cavity when said zones are in abutment against the wall of the cement sheath.

Thanks to said zones, the part can bear tightly against the wall of the cement sheath and allows precise positioning of the conduit relative to the body cavity.

The conduit makes it possible to guide a drill intended to pierce the distal part of the cement in such a way that the drilling carried out coincides substantially with the longitudinal axis of the body cavity. This hole can then be used as a guide means for cement drilling operations.

Preferably, the entire part has a shape which corresponds to the shape of at least one elongated portion of the implanted prosthesis, to ensure perfect support of this piece against the wall of the cement sheath.

According to one possibility, the part is made of a block of rigid material, in particular of synthetic material, and the conduit is delimited by a tube of a material capable of withstanding the drill bit, in particular of metal.

The entire piercing part can also be made of a material capable of resisting the piercing drill. A method of producing the piercing part according to the invention comprises the steps consisting in:

- To determine the dimensions of the prosthesis according to at least two planes, in at least two mutually distant locations in the longitudinal direction of this prosthesis, and to determine the orientation of the longitudinal axis of the prosthesis relative to the longitudinal axis the body cavity in which this prosthesis is implanted; - using a tube to delimit said conduit;

to orient this tube along a reference axis and to maintain this tube in this position relative to this axis, and to arrange said bearing zones with respect to this tube according to the dimensions and orientation mentioned above, in particular by molding of these areas around the tube or by machining at least one block of material having standard dimensions, previously arranged around said tube.

The determination of these dimensions can be done by reading dimensions on images obtained by radiography or scanner, or simply by knowing the type and size of the implanted prosthesis. The determination of said orientation is done, for its part, from said images.

Another method of producing the piercing part according to the invention comprises the steps consisting in:

- note the position of the prosthesis in space with respect to a reference axis, by measuring the distance from different points on the wall of this prosthesis with respect to this axis;

- placing the prosthesis removed from the patient in a support which includes means for the precise positioning of this prosthesis in space relative to said reference axis and means for mounting a tube coaxial to this reference axis;

- To adjust the position of the prosthesis in said support using one of said means; - placing the prosthesis and the support in a container;

- Pouring into this container a material capable of hardening, so as to take the imprint of the prosthesis thus positioned; - wait for the hardening of said material, or carry out this hardening;

- to remove the prosthesis;

- Place the tube in the impression of the prosthesis thus obtained, coaxially with said reference axis, and - pour into this impression a product capable of hardening, to obtain a molding of the prosthesis around the tube.

This process can be used during surgery when the type of prosthesis implanted remains unknown.

A third method of producing the piercing part according to the invention comprises the steps consisting:

- to arrange, in particular by molding or machining, a plurality of piercing parts, the side wall of each of which has a shape corresponding to the particular shape of an existing prosthesis;

- to determine the type and size of the prosthesis concerned as well as the orientation of the longitudinal axis of this prosthesis relative to one longitudinal axis of the body cavity;

- Orient the part corresponding to the prosthesis concerned along a reference axis and maintain this part in this position relative to this axis;

orienting a drilling tool with respect to this part as a function of said orientation, and - to arrange said conduit through this room.

In the case where the material of the part is not capable of withstanding the drilling drill, this method further comprises the step consisting in placing, in the drilled conduit, a tube made of a material capable of withstanding the drill , especially in metal.

For a good understanding, the invention is again described below with reference to the appended schematic drawing representing, by way of nonlimiting examples, two preferred embodiments of the piercing part that it relates to, as well as various means of implementing a method of manufacturing this part. Figure 1 is a partial sectional view of the piercing part according to a first embodiment; Figure 2 is a view of the upper end of a femur, in longitudinal section, with a medullary rod implanted therein; Figure 3 is a view of the piercing part in use in this end; Figure 4 is a view of a boring tool in use in this end; Figure 5 is a view of the piercing part according to a second embodiment; Figure 6 is a front view of a support for implementing a method of producing this piercing part, in which is placed a femoral hip prosthesis rod; FIG. 7 is a side view of this support and of a container, during one phase of the process, and FIGS. 8 and 9 are views of this support during two subsequent phases of this process.

The upper end of the femur 2 comprises a femoral stem 3 of hip prosthesis fixed in the medullary canal 4 by means of a sheath of surgical cement 5. According to a conventional technique, a spinal plug 6 of flexible material was placed in the channel 4 before placing the cement.

This rod 3 must be replaced by another, more suitable rod, which implies the elimination of the sheath 5.

In the example shown, the rod 3 is placed in varus, so that its longitudinal axis, and therefore the longitudinal axis of the sheath 5, is oriented obliquely relative to the axis of the femoral shaft 2a.

The piercing part 10 shown in FIG. 1 comprises a metal tube 11, on a portion of which is molded an elongated cylindrical block 12 made of rigid material but easy to machine, in particular polyethylene.

A determination is made of the dimensions of the rod 3 along at least two orthogonal planes parallel to the longitudinal axis of the rod 3, at a large portion of the diaphyseal part 3a thereof, and a determination the orientation of the longitudinal axis of the rod 3 relative to the longitudinal axis of the shaft 2a. This determination of the dimensions of the rod 3 is made by reading dimensions on images obtained by radiography or scanner, or simply by knowing the type and size of the implanted rod 3, while the determination of said orientation is made from said images.

The tube 11 is then oriented along a reference axis and is held in this position relative to this axis, and the block 12 is machined, depending on the dimensions and orientation of the prosthesis, to form the part 10 proper, capable of 'be used for the elimination of the sheath 5. The shape of this part 10 corresponds to said portion of the diaphyseal part 3a of the rod 3, and its orientation relative to the axis of the tube 11 corresponds to the orientation of the longitudinal axis of the sheath 5 relative to the axis of the diaphysis 2a.

After removal of the rod 3, the piercing part 10 is engaged in the cavity of the sheath 5 so that its machined part 12 comes closely into contact with the cement. As shown in FIG. 3, the axis of the tube 11 is then placed precisely coaxially with the axis of the diaphysis 2a and makes it possible to guide a drill 15 for drilling the distal part 5a of the sheath 5 and of the plug 6.

The bore 16 produced (FIG. 4) is thus substantially coaxial with the longitudinal axis of the diaphysis 2a.

The tool 20 shown in Figure 4 is then used. This tool 20 comprises a rod 21 connected to a rotational drive means, a cutting head 22, for the bore of the cement, and, beyond this head 22, on the distal side, a cylindrical pin 23 intended to be engaged and to rotate in the hole 16. This tool 20 is part of a series of tools which are similar to each other, comprising cutting heads 22 whose diameter increases from one tool to another, to allow progressive boring. sheath 5, and pins 23 of suitable lengths. The cutting head 22 of a tool 20 may only include a cutting zone 22a on its distal part, its proximal part 22b being smooth, as shown in FIG. 4. This part 22b therefore does not attack the distal cement and keeps an axial guide to the head 22 by this cement when the zone 22a of this head reaches the plug 6.

FIG. 5 shows a piercing part 30 which can be used in place of the part 10. This part 30 consists of an elongated block 32 of material molded or machined according to the shape of said diaphyseal portion 3a of the rod 3. After determination of type and size of the implanted rod 3, as well as of the orientation of the longitudinal axis of the rod 3 relative to the longitudinal axis of the diaphysis 2a, this block 32 is drilled as a function of said orientation. Depending on the hardness of the material used for the block 32, this hole itself constitutes the conduit 31 for guiding the drill 15 or receives a tube made of a material capable of resisting the drill, in particular made of metal.

Several pieces 30 are arranged in shapes corresponding substantially to those of the different types and sizes of existing rods, and are drilled as required.

Figures 6 to 9 illustrate different phases of implementation of a method of manufacturing the piercing part 10 comprising a tube 11, during surgical intervention and from the femoral stem 3 just removed from the 'bone.

The method is implemented by means of a support 40 comprising a main plate 41, in the upper end of which is arranged a vertical notch 42, and two parallel lower plates 43. These plates 43 are arranged opposite one on the other and located at a mutual distance such that the rod 3 can be placed between them. Plate 41 includes three transverse lights

44, one of which is arranged so as to be placed at the level of the distal part of the rod 3 and the other two of which are arranged in two stage locations, situated substantially at the level of the metaphyseal part of this rod 3.

One of the two plates 43 comprises two slots 45 arranged at heights similar, but slightly different, from that of the slots 44, respectively.

Rods 50 protruding between the plates 41 and 43 are engaged and can slide through these lights 44 and 45 and can be immobilized in a determined position of these lights 44 and 45.

Each rod 50 comprises for this purpose a fixed flange 51, by which it bears against the internal face of the plate 41 or 43, a threaded portion 52 projecting beyond the external face of this plate 41 or 43, this portion 52 being intended to receive a mounting nut 53, and a portion of square cross section at the height of the plate 41 or 43, for its setting in rotation during the tightening or loosening of the nut 53.

The plates 41, 43 include graduations 55 along the edges of the openings 44, 45, taking as their point of origin a vertical reference axis, passing substantially through the middle of the plates 41 and 43.

It appears in FIG. 9 that the tube 11 can be mounted on the support 40 coaxially with said reference axis, by means of a plate 56 in which this tube 11 is held by engagement with gentle friction, this plate 56 comprising two screws 57 intended to be received in the notch 42.

In practice, the distance of different points of the wall of the rod 3 relative to the diaphyseal axis is noted on radiographs, these points corresponding substantially to the heights of the rods 50 in the support 40. The rods 50 are then adjusted in their respective lights 44, 45 as a function of these positions, then the rod 3 extracted from the patient is placed in the support 40.

The support 40 and the rod 3 are placed in a container 60 (FIG. 7) into which is poured a product capable of hardening, in particular a silicone product. Once this product has been taken (FIG. 8), the rod 3 is removed then the plate 56 is put in place, the tube 11, the distal end of which has been temporarily plugged, having come down until it comes into contact with the wall of the imprint 61 delimited by the block 62 of cast material (FIG. 9).

Finally, a liquid material capable of hardening is poured into the cavity to constitute the piercing part 10. After hardening, the block made up of this material is removed using the tube 11.

It goes without saying that the invention is not limited to the embodiment described above by way of example but that it embraces, on the contrary, all the variant embodiments. Thus, the tool 20 could comprise a guide rod which can be engaged in the hole 16 and a tubular rod connected to its cutting head, this tubular rod being able to be engaged on this guide rod and to rotate relative to that -this.

Claims

1 - Piercing part (10, 30) intended to be used in the context of an operation to remove a sheath of surgical cement, this sheath (5) having been used for sealing a prosthesis (3) of form lying in an elongated body cavity (4); this part (10, 30) has a shape such that it can be engaged in the cavity which delimits the cement sheath (5) after removal of the prosthesis (3), and comprises a conduit (11, 31) arranged in it , allowing the drilling of a hole (16) for guiding or passing tools (15, 20) used to effect the elimination of the sheath (5); this part (10, 30) is characterized

- In that it comprises at least two mutually axially distant zones, shaped to bear tightly against the wall of the sheath (5) of cement;

- in that the axis of the duct (11, 31) forms a non-zero angle with the longitudinal axis of the part (10, 30), corresponding to the angle formed by the longitudinal axis of the cavity which delimits the cement sheath (5) with the longitudinal axis of the body cavity (4), and

- in that said zones and said conduit (11, 31) are mutually positioned so that the axis of the conduit (11, 31) coincides with the longitudinal axis of the body cavity (4) when said zones are supported against the wall of the cement sheath (5).

2 - piercing part according to claim 1, characterized in that it has a shape which corresponds to the shape of at least one elongated portion (3a) of the implanted prosthesis (3).

3 - drilling part according to claim 1 or claim 2, characterized in that it is made of a block (12) of rigid material, in particular synthetic material, and in that the conduit is delimited by a tube (11) made of a material capable of withstanding the drill bit, in particular metal.

4 - Method for producing the piercing part according to one of claims 1 to 3, characterized in that it comprises the steps consisting:

- determining the dimensions of the prosthesis (3) along at least two planes, at least two mutually distant locations in the longitudinal direction of this prosthesis (3), and determining the orientation of the longitudinal axis of the prosthesis ( 3) relative to the longitudinal axis of the body cavity (4) in which this prosthesis (3) is implanted;

- using a tube (11) to delimit said conduit; - orienting this tube (11) along a reference axis and maintaining this tube in this position relative to this axis, and

- Arranging said support zones relative to this tube (11) according to the dimensions and orientation thus determined, in particular by molding these zones around the tube or by machining at least one block (12) of standard dimensions beforehand arranged around said tube (11).

5 - Method for producing the piercing part according to one of claims 1 to 3, characterized in that it comprises the steps consisting:

- noting the position of the prosthesis (3) in space relative to a reference axis, by measuring the distance from different points of the wall of this prosthesis (3) relative to this axis;

- placing the prosthesis (3) removed from the patient in a support (40) which comprises means (44 to 55) for the precise positioning of this prosthesis (3) in space relative to said reference axis and means ( 42, 56, 57) for mounting a tube (11) coaxial with this reference axis; - adjusting the position of the prosthesis (3) in said support (40);

- placing the prosthesis (3) and the support (40) in a container (60); - Pouring into this container a material capable of hardening, so as to take the impression of the prosthesis (3) thus positioned;

- wait for the hardening of said material, or carry out this hardening; - to remove the prosthesis (3);

- placing the tube (11) in the impression of the prosthesis (3) thus obtained, coaxially with said reference axis, and

- To pour into this impression a product capable of hardening, to obtain a molding of the prosthesis around the tube (11).

6 - Method for producing the piercing part according to one of claims 1 to 3, characterized in that it comprises the steps consisting: - in arranging, in particular by molding or machining, a plurality of piercing parts (30) the side wall of each of which has a shape corresponding to the particular shape of an existing prosthesis;

- to determine the type and size of the prosthesis (3) concerned as well as the orientation of the longitudinal axis of this prosthesis relative to one longitudinal axis of the body cavity (4);

- Orienting the part (30) corresponding to the prosthesis (3) concerned along a reference axis and maintaining this part in this position relative to this axis;

- orienting a drilling tool relative to this part (30) as a function of said orientation, and

- to arrange said conduit (31) through this part (30). 7 - A method according to claim 6, characterized in that it further comprises the step of placing in the drilled conduit (31) a tube of a material capable of withstanding the drill, in particular metal. 8 - set of instruments comprising the piercing part according to one of claims 1 to 3, characterized in that it further includes at least one rotary tool (20) for boring the cement comprising, beyond its cutting head (22), distal side, an axial guide means (23) intended to be engaged in the hole (16) drilled by means of the drill (15) to guide the tool (20).

9 - assembly according to claim 8, characterized in that the tool (20) comprises, beyond its cutting head (22), distal side, a cylindrical pin (23) intended to be engaged and to rotate in the hole (16) drilled using the drill (15).

10 - assembly according to claim 8, characterized in that the tool (20) comprises a guide rod which can be engaged in the hole (16) drilled by means of the drill (15) and a tubular rod connected to its cutting head , this tubular rod being adapted to be engaged on this guide rod and to rotate relative to the latter.

11 - assembly according to one of claims 7 to 10, characterized in that the cutting head (22) of the tool

(20) comprises a cutting zone (22a) on its distal part, its proximal part (22b) being smooth.