Device For Blocking A Tendon Graft

Abstract

A device serves for blocking a tendon graft in a drilled hole. An element is connected to said tendon graft which can be expanded radially. The element has a cylindrical body which is divided by an oblique cut into two wedge-shaped bodies initially connected to one another via a predetermined break point.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described and explained in more detail below on the basis of a number of selected illustrative embodiments and with reference to the attached drawings, in which:

FIG. 1 shows a perspective view of a first illustrative embodiment of an element according to the invention for blocking a tendon graft, composed of two wedge-shaped bodies, specifically before expansion,

FIG. 2 shows a perspective view, comparable to FIG. 1, after the radial expansion of the element caused by axial displacement of the wedge-shaped bodies relative to one another,

FIG. 3 shows a plan view of the element from FIG. 1, in the non-expanded state,

FIG. 4 shows a plan view of the element from FIG. 2, in the expanded state,

FIG. 5 shows a partially sectioned view of a device for blocking a tendon graft, with the element depicted in FIG. 1, the assembly made up of tendon graft element and pulling threads having just been inserted into a drilled hole, prior to its radial expansion,

FIG. 6 shows a cross section corresponding to the representation in FIG. 5, after radial expansion of the element in accordance with the change from FIG. 1 to FIG. 2, and

FIG. 7 shows a greatly enlarged cross-sectional representation of a configuration of the wedge surfaces that slide along one another, with a catch arrangement.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

A radially expandable element shown in FIGS. 1 to 4 is designated generally by reference number 10.

The element 10 is composed of a cylindrical body 12 with a continuous bore 14 extending centrally through it.

The body 12 is divided by a diagonal oblique cut 16 into two wedge-shaped bodies 18 and 20. The surface of the cut at the same time defines the two mutually facing wedge surfaces 19 and 21 of the wedge-shaped bodies 18 and 20.

The oblique cut 16 is not entirely continuous, and instead the two wedge-shaped bodies 18 and 20 are still connected to one another via a more or less punctiform predetermined break point 22, so that the body 12 is held in the position shown in FIG. 1, i.e. the two wedge-shaped bodies 18 and 20 do not come apart from one another. On its outside, the body 12 is provided with projections in the form of claws 13 that protrude radially from it. It will be seen from the plan view in FIG. 3 that the body has a diameter d.

When a force is exerted on the wedge-shaped body 18 in the direction of an arrow 23 and when the second wedge-shaped body 20 rests on an abutment, the wedge-shaped body 18 moves in the direction of the arrow 23, after the predetermined break point 22 has been broken.

This force in the direction of the arrow 23 can be exerted by a pulling force, as will be explained in more detail below, for example by a draw-thread connected to the wedge-shaped body 18. The connection can be established via an eyelet 26 provided on the body 18.

In this way, the body 12 is expanded in the radial direction, as can be seen in particular from FIG. 4. This means the radial extent d has increased by the amount Δx, which is dependent on how far the two wedge-shaped bodies 18 and 20 are displaced relative to one another.

FIGS. 5 and 6 now show how this displacement of the two wedge-shaped bodies 18 and 20 can be achieved.

It will be seen that a drilled hole 32 has been formed in a bone 30, for example in the femur, this drilled hole 32 having a first portion 34 with a first diameter that merges into a second portion 36 with a smaller diameter, the second portion 36 extending as far as the outer face of the femur. A shoulder 38 is formed at the transition between the first portion 34 and the second portion 36.

The clear internal diameter of the first portion 34 corresponds approximately to the external diameter d of the element 10 from FIG. 1, including its claws 13 protruding from the outside face.

A tendon graft 40, which is to be anchored and blocked in the drilled hole 32, is usually formed as a U-shaped loop at its insertion end 45.

The tendon graft 40 can be an artificial graft or, alternatively, a natural tendon that has been taken form another part of the patient's body, for example the semitendinosus tendon.

The insertion end 45 of the tendon graft 40 is knotted with pulling threads 42, and the element 10 is threaded onto the insertion end 45 by the pulling threads 42 being threaded through the central continuous bore 14 in the body 12, and by the element 10 being pushed over the pulling threads 42 as far as the insertion end 45.

If desired, the element 10 can be connected to the tendon graft 40 by an additional knot. In a further embodiment, a separate draw-thread can be provided that is connected only to the upper wedge-shaped body 18, e.g. is knotted to the latter, for which purpose a corresponding eyelet 26 (see FIG. 1) is provided thereon. The expansion of the wedge-shaped bodies 18 and 20 can then be achieved simply via this draw-thread.

This device composed of tendon graft 40, pulling threads 42 and element 10 is now pushed into the drilled hole 32, specifically with the pulling threads 42 toward the front, these pulling threads 42 being threaded through the second portion 36 and reaching as far as the outer face. By pulling on the pulling threads 42, the assembly is pulled into the drilled hole 32 until the leading face of the element 10 comes to lie on the shoulder 38, as is shown in FIG. 5. In this position, the operating surgeon can check for the correct fit.

In order to achieve the blocking effect, the pulling threads 42 are now firmly pulled in the direction of the arrow 43 in FIG. 5. A force is thus exerted on the wedge-shaped body 18. Since the other wedge-shaped body 20 lies on the shoulder 38 as its abutment, the wedge-shaped body 18 slides downward a little along the wedge surfaces 19 and 21, and, as has been described above concerning the change from FIG. 3 to FIG. 4, the element 10 is radially expanded.

This situation after the expansion is shown in FIG. 6. During the relative displacement of the wedge-shaped bodies 18 and 20, the element 10 is blocked in the first portion 34 of the drilled hole 32, and this blocking can be permanently maintained by the pulling threads 42 being secured in this tensioned state. This is done by knotting the pulling threads 42 on the outside onto what is called a fixation button, so that, by subsequently turning this fixation button, it is possible to further adjust this tensioning. The same applies to the embodiment with the separate draw-thread.

During the expansion of the element 10 by means of the relative movement of the wedge-shaped bodies 18 and 20, the claws 13 provided on the outside of the element 10 also eat their way into the inner wall 35 of the drilled hole 32, that is to say into the spongy substance of the bone 30. This provides an additional safeguard against the element 10 being dislodged. The aforementioned tensile force is sufficient to rupture the predetermined break point 22 that connects the two wedge-shaped bodies 18 and 20 to one another, thereby permitting the displacement.

In the design of the element 10 shown in FIGS. 1 to 6, the mutually facing wedge surfaces 19 and 21 are smooth, so that, when the tensioning force on the pulling threads 22 is cancelled, the two wedge-shaped bodies 18 and 20 could in theory be moved back into the position shown in FIG. 5. This design may be desirable if it is found, after insertion and blocking, that the tendon graft is damaged and has to be immediately replaced by another one at the operating site.

FIG. 7 shows another embodiment in which it will be seen that a catch arrangement 50 is provided on the mutually facing wedge surfaces 19′ and 21′ of two wedge-shaped bodies 18′ and 20′ which in other respects are identical to those described above. The respective teeth 51 and 52 on the mutually facing wedge-shaped bodies 18′ and 20′ are designed in such a way that, as has been described above, a relative displacement is possible during expansion of the body 12, by means of the teeth 51, 52 sliding across one another, whereas this movement is prohibited in the opposite direction.

In this embodiment, the displacement is therefore irreversible, and this results in a secure and irreversible blocking effect.

Claims

1. A device for blocking a tendon graft in a drilled hole in a bone, said drilled hole having a first portion with a first diameter for receiving said tendon graft, said first portion being adjoined by a second portion of smaller diameter through which pulling threads connected to said tendon graft extend as far as an outer surface of said bone, comprising an element which can be applied to an insertion end of said tendon graft, which element comes to bear on a shoulder between said first portion and said second portion of said drilled hole, whereinsaid element is designed to be radially expandable, a radial expandability can be achieved by pulling on at least one draw-thread,said element has an approximately cylindrical body,said cylindrical body is divided by an oblique cut into two wedge-shaped bodies,said two wedge-shaped bodies can be displaced relative to one another in an axial direction of said drilled hole, and whereinsaid two wedge-shaped bodies are connected to one another via a pre-determined break point.

2. The device of claim 1, wherein at least one catch arrangement is provided on wedge surfaces of said wedge-shaped bodies that slide along one another.

3. The device of claim 1, wherein said cylindrical body has, on its outer face, claws which engage with an inner wall of said first portion of said drilled hole, when said cylindrical element is in an expanded state.

4. The device of claim 1, wherein said cylindrical body has a continuous bore through which said draw-threads can be guided.

5. The device of claim 1, wherein said at least one draw-thread for said radial expansion of said cylindrical element is formed by said pulling threads of said tendon graft.

6. The device of claim 1, wherein said cylindrical body is made of metal.

7. The device of claim 6, wherein said metal is titanium.

8. The device of claim 1, wherein said cylindrical body is made of an absorbable material.

9. The device of claim 8, wherein said absorbable material is an absorbable polymer.