AU2013389955A1

AU2013389955A1 - Implant for extra-cortical fracture stabilisation

Info

Publication number: AU2013389955A1
Application number: AU2013389955A
Authority: AU
Inventors: Hubert Pius NOETZLI
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-05-15
Filing date: 2013-05-15
Publication date: 2015-12-03
Also published as: CA2911348A1; CN105228540A; EP2996593A1; BR112015028601A2; JP2016517783A; WO2014183223A1

Abstract

The invention relates to an implant (1) for osteosynthesis, which is pressed against the bone by means of one or more encircling wires, cables or bands and, in the contact zones (11) specifically provided for the purpose on the underside of the implant, bonds to the bone under the contact pressure such that a displacement of the bone relative to the implant is prevented.

Description

IV English translation of the specification of the International Patent.Aplication No. PCT/CH2013/000084 "Implant for extracortical fracture stabilization" in the name of NOTZLI Hubert Pius Implant for extracortical Fracture Stabilization The invention relates to an implant for osteosynthesis - particularly in humans - which is pressed onto the bone by means of a wire, cable or band and interacts with the bone surface in the specially formed contact zones on the underside of the implant in such a way that a displacement of the bone relative to the implant is prevented due to the imposed contact force. Implants for osteosynthesis have been used for quite some time and in a variety of construction and fixation methods in human and veterinary medicine. A very commonly used design is the plate with holes that are required to fix it with screws to the bone. For fractures in the area of or close to an implant inserted into the intramedullary canal of a long bone - a joint prosthesis for example - the fixation with screws close to such an implant can be severely limited. Osteoporosis and thin cortex in conjunction with such an implant in the intramedullary canal pose the greatest challenge in periprosthetic fracture fixation. The fixation with screws can be well-nigh impossible in thinner cortex close to an implant placed into the intramedullary canal. This is especially true for implants with locking screw fixation as commonly employed and recommended in osteoporotic bone, because the screw alignment specified by the locking features offers only limited range of alignment. Therefore, as is known from various publications, screws interfering with an implant in the intramedullary canal can lead to premature failure of the osteosynthesis. Furthermore, it is apparent from other publications that the implant/bone interface can be damaged by screw insertion close to this interface and that in the case of cemented prostheses the cement may partially be destroyed, which leads to premature loosening of the implant. Because of all these findings, a plate fixation, which is purely extracortical would be desirable, especially in consideration of fractures close or in the area of implants placed into the intramedullary canal with or without cemented interface. A known solution for this is the use of cerclage by means of wires, cables or bands to attach the plate to the bone instead of the plate fixation with screws. Experience shows, however, that such 2 fixation with conventional plate systems lacks in rotational stability which leads to high failure rates. To improve the stability of this kind of fixation, different plate inserts were developed for improved connection with the wires, Nevertheless, such inserts without direct contact to the bone will not improve rotational stability. Inserts that require a unicortical bone fixation in a short hole would improve the rotational stability, but are at least partially affected by the above-mentioned disadvantages of screw fixation. In thinner cortex these unicortical inserts cannot be placed sufficiently deep into the bone, which affects their stability. The present disclosure provides a rotationally and axially stable fixation with extracortical cerclage by wires, cables or bands. Most important for the rotationally and axially stable fixation of the implant by means of cerclage is the implant/bone interface on the underside of the implant that faces the bone, which is imposed by the contact force between the implant and the bone produced by the cerclage, in particular by the tension in the cerclage. An obvious assumption would be that this implant/bone interface has to be made as large as possible, It is known from various publications, however, that extensive implant/bone interfaces have the disadvantage of impairing the blood flow to the periosteum and the underlying bone and thus may lead to bone necrosis. From EP 0 355 035 B1 an implant is known that has specific points of contact between the implant and the bone which provide contact areas that are as small as possible when the implant is compressed onto the bone by its fixation. The aim of these defined points of contact is to keep the entire contact area of the implant to the bone as small as possible in order to allow a largely uninhibited blood flow in the periosteum and hence in the bone. The disadvantage of this concept is that only very few of these points of contact actually come into contact with the bone and that these points have no defined surface to engage with the bone surface, which could impede movement of the implant along the bone surface. The disclosed implant provides a variety of contact teeth enlarged in their individual contact zones and formed by a special surface so that the individual contact zones can apply forces under compression into the bone itself through the periosteum and thus prevent a displacement of the implant along the bone surface in all directions. From US 2010/0094294 Al and WO 2006/039900 Al implants with spikes in the contact area between the implant and the bone are known, which anchor themselves 3 into the bone under the tension of a cerclage. Such spikes have the disadvantage that they pierce the periosteum and injure the bone substantially, even though they still provide little resistance against any movement along the bone surface. Especially with very thin bone walls - as increasingly observed in osteoporotic bone - such spikes can destroy the bone wall in a way that leaves the holding force and hence stability severely compromised. The disclosed implant solves this problem by providing at least one flattened contact zone which has a special surface that interlocks with the bone surface through the engagement of multiple spikes andior teeth upon the surface of this contact zone in the periosteum and the underlying bone, thereby providing the desired rotationally and axially stable implant/bone interface. Brief description of the figures: Fig. 1 is a schematic representation of an embodiment of the inventive implant in the form of a plate with an underside comprising the special contact zones to engage as interfaces with the bone. Fig. 2 is a view of the underside of such an inventive implant to illustrate the groove structures on the surface of the contact zones. Fig. 3 is a view of the upper side of such an inventive implant, which can be connected to a plate by means of its cylindrical protrusion. The embodiment of the implant (1) shown in Fig. I is one possible variant of many. This implant (1) provides both the common means of fixation by receiving one or more bone screws (4) in through holes (40) as well as the fixation means for cerclage (2) embracing the implant (1) and the bone (3). On the underside (10) of the illustrated implant (1), the contact zones (11) comprise a number of grooves (12) oriented in different directions forming spikes and/or teeth (13) with aligned elongated sharp contact edges (131). The upper side (20) of the implant (1) may provide grooves (21) as connection means for the cerclage (2), holding it in stable position relative to the implant when the cerclage (2) is engaged in one of these grooves (21). The view onto a contact zone (11) on the underside (10) of the inventive implant (1) shown in Fig. 2 illustrates how the teeth (13) are formed by the shape (120) of the grooves (12), their directions (121) and their distances (122a-n) between the grooves (12) of the same orientation (121a-n). Preferably, the teeth (13) in the contact zones 4 (11) have no sharp points, but elongated sharp edges (131) facing different directions (131a-n), which increases the contact area of the individual teeth and improves the rotational and axial stability of the implant/bone interface. The embodiment of the implant (1) shown in Fig. 3 additionally comprises a cylindrical protrusion (51) as fixation means (50) on the upper side (20) to fix at least one of the inventive implants in at least one hole of a commercially available osteosynthesis plate. The inventive implant (1) may comprise fixation means (50) of any shape for the outer or inner fixation of other implants (5) of any form, provided that they do not interfere with the contact zones (11) on the underside (10) of the implant (1) or otherwise compromise the interface between the contact zones (11) and the bone (3). Such fixation means (50) can be provided by the outer shape of the implant (1) itself or by specially provided internal intrusions or external protrusions (51) on the upper side (20), on one or more side surfaces (30), or in either one or a plurality of through holes (40).

Claims

1. An implant (1) for fixation to a bone (3) by compression with a) an underside (10) with one or more protruding contact zones (11); b) an upper side (20); and c) one or more side surfaces (30); d) characterized in that the one or more contact zones (11) are provided with teeth (13) formed by a plurality of grooves (12) arranged in two or more different directions (121a-n).

2. The implant according to claim 1, characterized in that the teeth (13) have sharp contact points or contact edges (131) facing a bone (3).

3. The implant according to claim 2, characterized in that the contact edges (131) are arranged in two or more different directions (131a-n).

4. The implant according to one of claims 2 to 3, characterized in that the grooves (12) arranged in one or more directions (121a-m) are bent, so that the resulting contact edges (131) are bent as well.

5. The implant according to one of claims 1 to 4, characterized in that the implant (1) is pressable onto a bone (3) by one or more embracing cerclages (2).

6. The implant according to one of claims 1 to 5, characterized in that the upper side (20) comprises one or more grooves (21).

7. The implant according to the claims 5 and 6, characterized in that each of the one or more grooves (21) is configured: a) to receive one cerclage (2); and b) to fix said cerclage (2) under tension immovably relative to the implant (1).

8. The implant according to one of claims 1 to 7, characterized in that the implant (1) comprises one or more through holes (40). 6

9. The implant according to claim 8, characterized in that at least one of the through holes (40) is configured to receive a bone screw (2) to fix the implant (1) to a bone (3).

10. The implant according to one of claims 1 to 9, characterized in that the implant (1) comprises one or more fixation means (50).

11. The implant according to claim 10, characterized in that at least one of the fixation means (50) is configured in such a way that: a) the implant (1) is receivable in an osteosynthesis plate (5); and b) the implant (1) is fixable in an osteosynthesis plate (5) immovably relative to the same.

12. The implant according to claim 10, characterized in that at least one of the fixation means (50) is configured: a) to receive a supporting means (5); and b) to fix the supporting means (5) immovably relative to the implant (1).

13. The supporting means (5) according to claim 12, characterized in that the supporting means (5) is configured: a) to connect several implants (1) according to one of the claims 1 to 13 with each other; and b) to fix these implants (1) immovably relative to each other.

14. The implant according to one of claims 1 to 13, characterized in that the implant (1) is shapeable by compression in such a way that at least at the underside (10) the implant (1) fits to the shape of a bone (3).