WO2006119885A1

WO2006119885A1 - Reinforcing element for sternal closure

Info

Publication number: WO2006119885A1
Application number: PCT/EP2006/004064
Authority: WO
Inventors: Heinz Robert ZURBRÜGG
Original assignee: Alpha Research Deutschland Gmbh
Priority date: 2005-05-09
Filing date: 2006-05-02
Publication date: 2006-11-16
Also published as: DE102005021236A1

Abstract

The present invention consists of a reinforcement of the osteosynthesis following surgical splitting of the sternum (1) using sternal wires (2). The reinforcement is realized using a flexible reinforcing element, e. g. a spring (5). The spring (5) is applied with the aid of the sternal punch from posterior to anterior into the halves of the sternum (1) and the spring (5) penetrates the halves of the sternum (1) completely. The spring (5) acts as a counter bearing and enlarges the contact surface of the sternal wires (2) in the sternum (1). The spring (5) avoids cutting of the sternal wires (2) in the sternum (1) and bleeding from the spongiosa (12).

Description

REINFORCING ELEMENT FOR STERNAL CLOSURE

Field of Invention The invention relates to a reinforcing element for surgical use, specifically for closing the chest after the sternum (1) has been longitudinally split during open heart surgery.

Background of the Invention

Open heart surgery, including for instance aortocoronary bypass surgery and the replacement of cardiac valves, is among the most frequently performed major surgery. In this procedure, as shown in Fig. 1 , the sternum (1) is split longitudinally and the chest is forced apart along the opening using a spreader in order to gain access to the heart. When the intervention has been completed both halves of the sternum are brought together and an osteosynthesis is performed with the aid of transsternal sternum wires (2) using the binding principle.

Fig. 1 shows a diagram of the conventional method of closing the chest using transsternal wires. The two halves of the sternum (1) are realigned with a series of sternum wires (2).

In cases of poor quality bones due to osteoporosis or for other reasons the sternum wire (2) may cut into the sternum (1) as the chest is being closed when the sternum wires (2) are twisted and the loops tightened.

As shown in Fig. 2, as a result of forces (e.g. a cough) after surgery, the wires (2) can also cut (3) into the sternum. Fig. 2 shows the resulting gap, i.e. the sternum dehiscence (4), between the two halves of the sternum (1) in the perspective view and Fig. 3 shows the cross-section. The sternum dehiscence (4) can lead to serious complications, including infections.

The problem of sternum dehiscence (4) following osteosynthesis with the aid of sternum wires (2) is known and various solutions to the problem have been suggested. Among the reinforcements suggested is a surgical technique whereby additional longitudinal wires are placed laterally along the sternum (1), around the ribs and through the space between the ribs, in other words through the intercostal space. The sternum wires (2) are than placed laterally around these longitudinal wires. This suggested solution causes increased soft tissue damage and can injure the blood vessels. Summary of the Invention

The present invention consists of a reinforcement of the osteosynthesis following surgical splitting of the sternum (1) using sternum wires (2). The problem is solved using a tubular reinforcing element, preferably a spring (5), for osteosynthesis with the aid of sternum wires (2) through which the sternum wires (2) can be passed and which increases the contact surface area of the wires (2) on or in the sternum (1) and the spongiosa (12), characterized by the fact that the reinforcing element is flexible and is being bent during surgery. The spring (5) is applied with the aid of a sternum punch from posterior to anterior into the halves of the sternum (1) and the spring (5) penetrates the halves of the sternum (1) completely.

The spring (5) avoids cutting of the sternum wires (2) into the sternum (1) and bleeding from the spongiosa (12). The invention reduces the risk of sternal dehiscence and makes it simpler for the surgeon to pass the sternal wires (2) through the halves of the sternum (1 ).

The invention enhances the stability of chest closure with minimum of damage to the soft tissue and shortens the surgery time.

Another aim of the invention is to provide the surgeon with a set of implants which facilitate an improved chest closure technique, which stabilize the sternum (1) following sternotomy.

It is also intended to achieve a standardized penetration of the sternum (1) with a sternum punch.

Drawing: Fig. 9

Brief Description of the Drawings

Fig. 1 is a perspective view of a conventional sternum closure using sternum wires (2) following longitudinal splitting of the sternum (1) Fig. 2 shows the gap (4) between the two halves of the sternum (1) in perspective view following conventional sternum closure.

Fig. 3 shows the gap (4) between the two halves of the sternum (1) from fig. 2 in cross-section following conventional sternum closure.

Fig. 4 shows a perspective view of the spring (5) in the preferred form as a conical tension spring with the internal diameter (6), the outer diameter (7), the diameter of the spring wire (8) and the length (9).

Fig. 5 shows the sternum punch (10).

Fig. 6 shows a perforation thorn (11) for the sternum punch (10). Fig. 7 shows an invention-relevant part of the sternum punch (10) with the spring (5) over the perforation thorn (1 1) before application (in the left of the drawing) as well as a spring (5) in place in the sternum (1).

Fig. 8 shows the invention-relevant part of the sternum punch (10) with the spring (5) over the perforation thorn (11) during application as well as a spring (5) in place in the sternum (1). Fig. 9 shows a perspective view of an element set as stipulated in the invention consisting of sternum wire (2) and spring (5) in position following sternotomy. The trabecula in the marrow of the sternum (1) form the so-called spongiosa (12).

Detailed description of the preferred embodiments

The present invention consists of a reinforcement of the osteosynthesis by means of binding following, for instance, but not exclusively surgical splitting of the sternum (1) using a tubular reinforcement element, preferably a spring (5). A preferred method of implementation of the invention is characterized by the fact that the spring (5) consists of a conical tension spring.

Preferably, the spring (5) is applied with the aid of a sternum punch (10) from posterior to anterior in the two halves of the sternum (1).

The springs (5) are applied preferably orthograd in the sternum (1) so that they enlarge the contact surface of the sternum wire (2) enlarge in the sternum (1) and thus prevent the sternum wires (2) cutting (3) into the sternum (1).

It is intended that the sternum punch (10) or parts of the same, for instance the perforation thorn (1 1), be part of a kit which also contains the springs (5) and the sternum wire (2), preferably without a needle. Fig. 4 shows the spring (5) in its preferred form, i.e. as a conical tension spring with the internal diameter (6), the outer diameter (7), the diameter of the spring wire (8) and the length (9).

Fig. 5 shows the sternum punch (10), Fig. 6 shows the perforation thorn (1 1). The thorn (1 1 ) and spring (5) taper upwards which enables easier application of the spring in the sternum (1).

The application of the spring (5) with the aid of the sternum punch (10) is shown in Fig. 7 and Fig. 8. The perforation thorn (1 1) is screwed into the relevant part of the sternum punch (10). The instrument is then opened and the spring (5) is drawn over the thorn (1 1) by hand. The sternum punch (10) is put into position at right angles to the midline of the sternotomy and at right angles to the posterior surface of the sternum (1). The sternum punch (10) is closed and the spring (5) is pressed into the sternum (1). The thorn (1 1) with the applied spring (5) penetrates the sternum (1) completely.

The punching procedure is repeated in each sternum half six to eight times. The sternum wire (2) is pushed though the opening of the spring (5) from posterior to anterior preferably without using a needle. The procedure is repeated in each positioned spring (5) in both halves of the sternum. The closure of the sternum is completed with the conventional step of twisting the two free ends of the sternum wire (2).

Fig. 9 illustrates the sternum closure system following optimal tightening of the twists of the sternum wire (2). The spring (5), preferably the tension spring, results in an enlargement of the contact surface area of the sternum wire (2) in the sternum (1). Due to the presence of the spring (5) the punching channel in the sternum (1) is filled completely so that bleeding from the spongiosa (12) of the sternum (1) is avoided. This is a marked advantage over the procedure without a spring (5), i.e. the conventional procedure, since the channel in that case is always larger than the diameter of the sternum wire (2). In the conventional method of introducing the sternum wire (2), the sternum (1) is punctured through with the aid of a needle to the end of which is attached the sternum wire (2). Naturally, the needle is always thicker than the sternum wire (2) which is introduced.

By allowing the spring (5) to extend slightly beyond the posterior and anterior sides of the sternum (1) both exit points from the bone are also reinforced though the enlargement of the contact surface area of the sternum wire (2). It is thus ensured that the sternum wires (2) do not cut into the sternum (1), but are rather fixed exactly when tightened.

The preferred form of the reinforcing element as a spring (5) enables the reinforcing element to be bent without altering the internal diameter (6) at the turning points of the sternum wire (2). When the sternum wire (2) is tightened, the spring (5) fixes at the turning points so that if there is friction between the sternum wire (2) and the spring (5) there will be no dislocalization of the spring (5).

Through variations in the outer diameter (7) of the reinforcing element along a longitudinal distance of at least 1 mm of at least 1% and maximum 80%, a self-wedging effect of the reinforcing element in the sternum (1 ) is achieved. This is preferably achieved by the reinforcing element being in the form of a spring (5) through the individual loops. The variations in the internal diameter (6) of the reinforcing element along a longitudinal distance of at least 1 mm by at least 1% and maximum 80% ensure that the sternum wire (2) is only in contact with a small area when being tightened and thus glides easily. The risk of the dislocalization of the spring (5) when tightening the sternum wire (2) is thus minimized. The spring (5) and sternum wire (2) should be made of biocompatible materials. To avoid electro corrosion following implantation it is desirable that the spring (5) and the sternum wire (2) be made from electrically compatible materials, preferably from the same material. In a preferred form of the invention electro compatibility is ensured by selecting the same material for the sternum wire (2) and springs (5), preferably stainless steel of specification 316 LVM or DIN 1.4441.

Having the sternum wire (2) and spring (5) together in a single application kit facilitates optimal electrical compatibility of both components which each other.

The springs (5) and the sternum wires (2) are preferably so dimensioned in the kit that as a result the mechanical properties of both parts match with each other and that the diameter of the spring wire (8) being at least 10% and at the most 100% of the diameter of the sternum wire (2). This invention will be offered as a ready-to-use application kit containing all the materials for the sternum closure. The application kit consists of several sternum wires (2) with two springs (5) per sternum wire (2) as well as a non-implantable perforation thorn (11) for the sternum punch (10). The preferred form of the sternum wire (2) is soft, annealed stainless steel wire with a diameter of between 0.4 and 2.0 mm, preferably 0.8 mm.

The preferred form of the spring (5), preferably a tension spring, consists of hard tempered stainless steel wire.

Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.

Claims

We claim as our invention:

1. Tubular reinforcing element for osteosynthesis with the aid of binding fibers, through which the binding fibers can be passed and which increases the contact surface area of the binding fibers on or in the bone, characterized by the fact that the reinforcing element is flexible and that when it is being bent during surgery, the internal diameter (6) reduces by less than 66% of its original diameter.

2. A tubular reinforcing element for osteosynthesis as per claim 1 , characterized by the fact that the reinforcing element is made of at least one spiral-shaped monofiber fiber wound around the vertical axis whereby the winding may be conical or straight and the springs are tension springs or pressure springs or a combination of both.

3. A reinforcing element for the osteosynthesis as per claim 1 characterized by the fact that the outer diameter (7) of the reinforcing element varies along a longitudinal distance of at least 1 mm by at least 1% and no more than 80% .

4. A tubular reinforcing element for the osteosynthesis as per claim 1 characterized by the fact that the inner diameter (6) of the reinforcing element varies along a longitudinal distance of at least 1 mm by at least 1% and no more than 80% .

5. A tubular reinforcing element for the osteosynthesis as per claim 1 , characterized by the fact that the cross-section of the reinforcing element is in the form of a polygon, consisting of at least three corners, and an ellipsis or a circle.

6. A tubular reinforcing element for the osteosynthesis as per claim 1 , characterized by the fact that the reinforcing element is conical in shape along the vertical axis.

7. A tubular reinforcing element for the osteosynthesis as per claim 1 , characterized by the fact that the reinforcing element is cylindrical in shape along the vertical axis.

8. A tubular reinforcing element for the osteosynthesis as per claim 1 , characterized by the fact that the reinforcing element exists in at least one part.

9. A tubular reinforcing element for the osteosynthesis as per claim 1 , characterized by the fact that the reinforcing element has at least a length (9) of 3 mm.

10. A tubular reinforcing element for the osteosynthesis as per patent claim 1 , characterized by the fact that the diameter of the fiber of the reinforcing element is at least 10% and at the most 100% of the diameter of the binding fiber.

1 1. A tubular reinforcing element for the osteosynthesis as per patent claim 1 , characterized by the fact that the binding fiber is a sternum wire (2).

12. A tubular reinforcing element for the osteosynthesis as per claim 1 , characterized by the fact that the reinforcing element and the binding fiber are of implantable material of stainless steel, plastic, platinum, gold, titanium or a combination of these.

13. A tubular reinforcing element for the osteosynthesis as per claim 1 , characterized by the fact that the reinforcing element and binding fiber are made of identical material.

14. A tubular reinforcing element for the osteosynthesis as per patent claim 1 , characterized by the fact that the smallest diameter of the reinforcing element is at least 10 % and at the most 800 % bigger as the diameter of the binding fiber.

15. A tubular reinforcing element for the osteosynthesis as per patent claim 1 , characterized by the fact that the reinforcing element is no longer than the perforation thorn (11) of the sternum punch (10).

16. A tubular reinforcing element for the osteosynthesis as per patent claim 1 , characterized by the fact that the reinforcing element has a tolerance of at least +0.01 mm when compared with the perforation thorn (11) of the sternum punch (10).

17. A tubular reinforcing element for the osteosynthesis as per patent claim 1 , characterized by the fact that it is part of a set which in combination contains at least one reinforcing element and at least one binding fiber.

18. A tubular reinforcing element for the osteosynthesis as per patent claim 1 , characterized by the fact that the reinforcing element lines the inner surface of the channel in the spongiosa (12) of the bone by at least 30%.

9 sheets of drawings follow.