The present invention relates to an apparatus for fixing a ligament in surgery and a method for the surgical repair of a ligament. It furthermore relates to a tool for use with the apparatus according to the invention.
Ligaments are extendable, fibrous connective tissue strands which flexibly connect the moveable parts of the skeleton but limit mobility to a functionally reasonable degree and stabilize it with regard to non-physiological movements. If ligaments are extended beyond their natural length, stretching of ligaments and tearing of ligaments may occur. In particular, tearing of the cruciate ligament in the knee joint is very frequent. The customary method for replacing the torn cruciate ligament is the use of a ligament transplant, in particular of an autologous transplant from the patella tendon or the semitendinosus tendon. In a known technique, the implant is taken from the tendon in such a way that a small bone block from the patella and the tibial bone remain at each of the ends. The transplant is then anchored in the knee joint so that the bone blocks can intergrow in each case tibially and femorally with the bone. After the transplant has been drawn in, it is fixed to the bone. Below, the terms fixed or fixation/fixing always mean the connection between two interfaces with high tensile and shear strength. What is important is that the implant is drawn in and fixed so that it is under a certain tension which is required for functioning of the joint but on the other hand the tension at each joint position is not so great that mobility is limited.
For drawing in, the ligament transplant is usually connected at both ends to filaments which are then led through bone canals so that the ligament is drawn in with the aid of the filaments. There are various approaches for fixing the ligament. Firstly, it is usual to fix the ligament itself and secondly it is also known that the ligament can be fixed by a looped-on filament. This means that, instead of fixing the ligament itself, the filaments connected to the ligament are fixed. The latter is customary, for example, in the fixing of cruciate ligament transplants which carry bone blocks at their ends.
For direct fixing, it is known, for example, that the ligament can be clamped or can be fixed with the aid of screws. Fixing filaments can be fixed by knotting to screws or other retaining apparatuses. Finally, many types of auxiliary apparatuses are known, by means of which the ligaments and/or retaining filaments are fixed, cf. for example WO98/33455, U.S. Pat. No. 6,099,568 and U.S. Pat. No. 6,336,940 B1. Furthermore, so-called interference screws are known for fixing a ligament and/or filament. U.S. Pat. No. 6,660,023 B2 discloses a screw where the filament is likewise fixed by a so-called interference fit. However, the screw has a channel in which the filament is guided. In the channel, the filament can be drawn in the longitudinal direction by application of a comparatively strong force. Nevertheless, compression is sufficiently strong to press the filament against the anchor element. Finally, U.S. Pat. No. 6,517,579 B1 discloses an anchor apparatus by means of which a ligament can be directly fixed. The apparatus has a plurality of parts. The ligament is led between a sleeve and the drilled channel in the bone. An element to be introduced into the interior of the sleeve in the manner of a screw presses the sleeve with the ligament against the drilled channel, with the result that the ligament is fixed. Additional fixing is furthermore achieved by a clamp-like covering which presses the ligament into the bone in the manner of a drawing pin.
US 2004/037094 describes a bone anchoring element which is provided with eyes and is screwed into the bone by means of a screwdriver-like tool. The length of the filament drawn through the eyes has to be adjusted in a relatively complicated procedure with the aid of an adjustable, clasp-like slide. US 2004/0098050 discloses an approximately can-shaped element which can be anchored in the bone and in which the adjustable length of the associated filament can be fixed by locking of the lid and associated transformation of an elastic material contained in the can.
However, the apparatuses known in the prior art have the disadvantage that the ligament is very frequently punctured for fixing, with the result that it may tear. Furthermore, it is generally not possible to adjust the tension of the ligament exactly since, as a result of fixing with the known aids and apparatuses, a change in length very frequently occurs. The theoretical requirement to be implemented in practice is that the fixing of the ligament must take place so that neither the ligament is further tensioned by the fixing nor the tension of the ligament declines. This is not ensured in the case of most known apparatuses. Thus, the ligament length is automatically changed on screwing in an interference screw. The same applies if the filaments are knotted under tension and fixed.
It is therefore an object of the invention to provide an apparatus for fixing a ligament which makes it possible to fix the ligament without uncontrolled effects on the length and hence the tension of the ligament. Furthermore, damage to the ligament during fixing is to be avoided.
The apparatus according to the invention for fixing a ligament has a bone-anchoring element and a clamping sleeve. The bone-anchoring element has a proximal end, i.e. an end located closer to the patient's body and a distal end, i.e. an end remote from the body of the patient, and has a bore running in the longitudinal direction. The clamping sleeve has a proximal and a distal end. It can be accommodated in the bore and is radially expandable. As a result of this radial expansion of the clamping sleeve, the ligament can be fixed between the clamping sleeve and the bore of the bone-anchoring element.
The method according to the invention for the surgical repair of a ligament comprises the following steps, after a replacement for the ligament to be repaired had been drawn in via at least one drilled channel: a) introduction of a bone-anchoring element (1) into the drilled channel and anchoring therein, the ligament or at least a filament (50) connected to it for fixing being led in a bore (4) of the bone-anchoring element, b) radial expansion of a clamping sleeve (10) accommodated in the bore, with the result that the ligament can be fixed between the clamping sleeve and the bore of the bone-anchoring element.
As is known, the ligament is drawn into the joint by means of holes drilled in the bone. The bone-anchoring element is introduced into this bone bore, the ligament or the filament or the filaments which is/are connected to the ligament being accommodated in the bore of the bone-anchoring element and being led through. The clamping sleeve is now introduced into the bore, this being designed so that the ligament or filament has sufficient play. This means that there is a sufficient distance between the clamping sleeve and the bone-anchoring element so that the filament or filaments or the ligament can be moved between these two elements. The necessary tension is now applied to the ligament, for example with the aid of a spring balance, and the ligament or the filaments are fixed. For this purpose, the clamping sleeve is radially expanded so that the ligament or the filament is clamped between clamping sleeve and bone-anchoring element and fixed thereby. With the aid of the apparatus according to the invention, both the ligament itself and at least one filament connected to the ligament can be fixed. The number of filaments is not decisive, so that the expressions “a filament” and “a plurality of filaments” can be used interchangeably below.
In particular, a spindle which is connected to the clamping sleeve is provided for expanding the clamping sleeve. The spindle in turn has a proximal and a distal end. It is led through the clamping sleeve. The diameter of the proximal end is greater than the internal diameter of the clamping sleeve. The radial expansion of the clamping sleeve is effected by drawing the spindle out of the clamping sleeve, with the result that the clamping sleeve is extended owing to the size difference of the proximal end of the spindle and of the internal diameter of the clamping sleeve. An advantage of this design is that the expansion of the clamping sleeve takes place from the proximal end to the distal end. This means that the filament or the ligament is first fixed in the vicinity of the body and only thereafter is the further part of the filament or of the ligament subsequently fixed by the continuing expansion. This has the advantage that the tension is fixed with the first fixing at the first point of the bone-anchoring element. It can no longer change as a result of the further fixing of the ligament or of the filament between clamping sleeve and bone-anchoring element.
According to an alternative embodiment, however, the radial expansion can also be effected by means of grub screws or similar elements. The introduction of a rivet would also be an alternative embodiment.
The bone-anchoring element is preferably designed in the manner of a bone screw with a hollow bore. It is preferably produced from metal with suitable roughening (e.g. coarsely blasted) but can also be produced from bovine or human bone material which has been appropriately pretreated for implantation. The roughening can be effected, for example, by coarse corundum blasting. What is advantageous about the roughening of the surface on the bone side is that the secondary fixation, i.e. the bone growth, is improved. The bone-anchoring element can also be produced from resorbable material, such as polylactide or the same type of resorbable materials as used for the so-called resorbable interference screws. It is introduced into the bone channel by screwing in. A screwdriver of our own design which is preferably cannulated so that the tension filaments can be led through it is provided for screwing in. The filaments serve as a guide during introduction of the bone-anchoring element into the drilled channel. This is extremely advantageous since the position of the bone-anchoring element is predetermined by the exit point of the drawn-through fixation filaments out of the bone bore. The bone-anchoring element can thereby also be mounted outside the body on the screwdriver and only thereafter be guided through the soft tissue channel to the drilled channel by the filaments in an accurate manner.
The clamping sleeve is preferably profiled, in particular ribbed, knurled or dimpled, on the outside, with the result that the ligament is particularly well fixed. The profiling may be transverse, oblique, rhombus-shaped, helical or in a comparable pattern with periodical change of depths and elevations. The outside of the clamping sleeve thus readily engages the filament or the ligament without damaging it. The clamping sleeve is preferably made of metal.
It is intended that the clamping sleeve and/or the bone-anchoring element be produced from a shape memory alloy which is also known by the name “memory metal”. This has the advantage that, for example, the radial expansion of the clamping sleeve takes place simply by virtue of the fact that it expands owing to the body temperature which is higher in comparison with room temperature, which the clamping sleeve assumes before it is introduced into the body. A manual expansion process, for example by means of a spindle, would thus be superfluous.
For the withdrawal of the spindle from the clamping sleeve and hence the radial expansion thereof, pliers of a particular design are provided. They are similar to pop rivet pliers. They moreover enable the filaments to be tensioned with the aid of additionally mounted tensioning devices with a defined, optionally also measurable tensile force and hence the ligament transplant to be pressed into the bone.
After insertion of the bone-anchoring element with the special screwdriver, the guide sleeve of the screwdriver remains on the top of the bone-anchoring element and thus forms a fixed working channel through the so-called soft tissue covering. The spindle of the pop rivet pliers is then introduced with the mounted clamping sleeve (10) through the working channel and, after expansion of the clamping sleeve is complete, the filaments are cut off using a customary filament cutter.
Preferred developments of the invention are shown in the figures, and the list of reference numerals is part of the disclosure. The invention is explained in more detail figuratively and by way of example with reference to these figures.
The figures are described in relation to one another and as a whole. Identical reference numerals denote identical components, and reference numerals with different indices indicate functionally identical or similar components.
As is evident from
As is further evident from
The ligament is fixed by radially expanding the clamping sleeve 10, as indicated by the arrows 13 in
The withdrawal of the spindle 20 for fixing the filament 50 can be effected, for example, by means of a tool in the manner of pop rivet pliers. Such pliers 30 are shown schematically and in section in
According to the invention, the surgeon proceeds as follows after drawing in the ligament: First, the bone-anchoring element 1 is introduced into the bore or into the drilled channel in the bone. The screwdriver 40 which engages the bone-anchoring element 1 is used for this purpose. The filament 50 is first led through the bore 4 of the bone-anchoring element 1 and is then led further through the channel 43 of the cannulated screwdriver 40 with the aid of a filament introduction aid not shown. During introduction and screwing in to the bone, the surgeon now has adequate guidance which is provided for him by the filament 50. Furthermore, the cannulated screwdriver 40 and the bore 4 of the bone-anchoring element 1 ensure that the filament 50 of the ligament is not damaged while the bone-anchoring element 1 is being screwed in and is also not jammed between screw and drilled channel. After mounting of the bone-anchoring element 1, the screwdriver 40 is withdrawn. However, the guide sleeve 60, which has been introduced together with the screwdriver 40, remains on the bone-anchoring element 1. The filament now runs in the bone-anchoring element 1 and is led to the outside through the guide sleeve 60. Thereafter, the surgeon leads the clamping sleeve 10 of the bone-anchoring element together with the spindle 20 through the guide sleeve 60 into the bone-anchoring element 1 so that the filament 50 is led correctly between the inner surface 9 of the bone-anchoring element 1 and the wall 14 of the clamping sleeve 10, as shown in
1 Bone-anchoring element
2 Proximal end
3 Distal end
4 Bore
5 Axis
6 Thread
7 Engagement opening
8 Stop
9 Inner surface
10 Clamping sleeve
11 Proximal end
12 Distal end
13 Arrow
14 Wall
15 Profiling
16 Cylindrical guide section
20 Spindle
21 Proximal end
22 Distal end
30 Pliers
31 Front end
33 Engagement apparatus
34 Arrow
40 Screwdriver
41 Handle
42 Shaft
43 Channel
44 Engagement region
50 Filament
60 Guide sleeve
D1 Internal diameter of the bore
D2 External diameter of the clamping sleeve 10
D3 Head diameter of the spindle
D4 Shaft diameter of the spindle
D5 Internal diameter of the clamping sleeve 10
Number | Date | Country | Kind |
---|---|---|---|
00570/05 | Mar 2005 | CH | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/IB2006/050881 | 3/22/2006 | WO | 00 | 8/4/2009 |