Title
Connector for organic tissue, and method for repairing a fracture in organic tissue.
Technical field The present invention pertains to the field of orthopaedic surgery, and relates to a connector (or anchor) for organic tissue, such as skeletal bone or cartilage. The invention further relates to a method for repairing a fracture in organic tissue, using the connector according to the invention.
The invention can particularly advantageously be implemented in connection with fractured skeletal bones in which the bone or cartilage structure has been weakened due to osteoporosis or fragility of the bones, other degenerative diseases, or trauma. However, the invention can also be implemented in cases where the organic tissue surrounding a fracture is sound, or for fixating ruptured ligaments, tendons, or muscles to the skeleton.
Background of the invention
Within the field of orthopaedic surgery, a number of different devices for stabilisation of fractures, anchoring bone fragments or other organic tissue, or for correcting different malpositions, are previously lαiown. Amongst the previously known devices, bone nails, bone screws and tissue anchors can be mentioned.
Accordingly, US-A-5, 662,683 discloses a tissue anchor for use in fastening bone to bone, orthopaedic plates to bone, or cartilage to bone. The disclosed tissue anchor comprises a rigid, bio-compatible, elongate member having a diameter of from about 0.4 millimetres to about 3 millimetres comprising surgical-grade titanium or stainless steel wire or a bio- absorbable material which forms an open helical structure. The helical structure has a length from about 3 millimetres to about 75 millimetres, an outer diameter of a constant dimension of from about 1.5 millimetres to about 15 millimetres and a slope from about
0.5 to about 10 turns per centimetre. Furthermore, the tissue anchor has at a first end an insertion tip, and at a second end an attachment head which is capable of connecting organic tissue to the anchor and which comprises an eyelet for receiving a suture. The disclosed tissue anchor is reported to allow a method of holding together organic tissue with inimal disruption to the biological environment. According to US-A-5,662,683, the disclosed tissue anchor can be utilised in cases where the quality of bone may be questionable due to trauma or degenerative disease.
However, particularly in cases where the bone quality has degraded severely due to e.g. osteoporosis or trauma, the previously known devices can still be associated with a number of problems.
Accordingly, many previously known devices require a comparatively large cavity within the damaged organic tissue structure for accommodating the device during the healing process. Such a large cavity can weaken an already weak structure even further, particularly in case e.g. a tissue anchor has to be removed when the healing process is completed.
Furthermore, the previously lαiown devices will provide only poor or no anchorage in bone structures which are weakened by osteoporosis, other degenerative diseases, or trauma.
Insufficient anchorage can cause problems with to much play of the anchor in the organic tissue structure and, in the worst possible case, lead to an undesired malposition of e.g. a bone fragment after healing.
Summary of the invention
Accordingly, a first object of the present invention is to provide a connector for organic tissue, which connector requires only a minimal cavity within the organic tissue for accomodation during the healing process, and which connector provides an excellent anchorage and a high resistance towards axial loads also when the organic tissue structure is weakened due to a degenerative disease, trauma, or other reasons.
In accordance with claim 1, this first object of the invention is achieved by means of the connector comprising at least first and second rigid, helical members of a bio-compatible material, the helical members each having a first end with an insertion tip and an opposite, second end. According to the invention, the second ends are rigidly connected to each other and to a head for interaction with a tool for insertion of the connector 1 in the organic tissue, wherein the helical members together form an open helical structure.
A second object of the present invention is to provide a method for repairing a fracture in organic tissue, using such a connector.
In accordance with claim 9, this second object of the invention is achieved by means of the metliod comprising to make an incision and to insert a connector, using a tool, through a first organic tissue portion across a fracture into a second organic tissue portion. Thereby, the connector comprises at least first and second rigid, helical members of a biocompatible material, each member having a first end with an insertion tip and an opposite, second end.
According to the invention, the second ends are rigidly connected to each other and to a head, wherein the helical members together form an open helical structure which, during insertion and starting with the insertion tips, gradually is accommodated within the organic tissue portions as a result of the head interacting with the tool. The method according to the invention further comprises to close the incision, and to allow the fracture to heal with the organic tissue portions fixated in relation to each other by the connector.
In this context, the expression "organic tissue" should be understood as skeletal bone, cartilage, marrow, ligaments, tendons, muscles or other organic tissue in the vicinity of a fracture or another defect which is to be treated or repaired.
Further objects of the present invention will become evident from the following description, whereas the technical features which enables the further objects to be reached are evident from the dependent claims.
Brief description of the drawings
In the following, the invention will be described in greater detail with reference to the attached drawings, in which
Fig. 1 schematically shows a perspective view of a connector according to a preferred embodiment of the invention, and
Fig. 2 schematically shows the connector in Fig. 1 inserted in a distal end of femur.
Detailed description of preferred embodiment
In the following, a preferred embodiment of the connector according to the invention will be described with reference to the attached Fig. 1.
The connector 1 comprises at least first 2 and second 3 rigid, helical members of a bio- compatible material, which preferably is titanium. However, the bio-compatible material might as well be stainless steel, another bio-compatible metal alloy, or a bio-absorbable material.
The helical members 2, 3 each has a first end with an insertion tip 4, 5 and an opposite, second end 6, 7. Thereby, the insertion tips 4, 5 are preferably sharpened in a way which is suitable for the purpose.
According to the invention, the second ends 6,7 are rigidly connected to each other and to a head 8 for interaction with a tool (not shown in the drawings) for insertion of the connector 1 in the organic tissue. The rigid connection between the second ends 6, 7 and between the head 8 and the second ends 6, 7 can be accomplished e.g. by means of welds, or by means of a suitable connecting member 8' (which can be a portion of the head 8 as shown in Fig. 1), or in another suitable way. The tool for interaction with the head 8 can be any suitable screwing tool, e.g. a screw driver, a wrench, or a T-handle provided with a suitable screw holder.
According to the invention, the helical members 2, 3 together form an open helical structure 9. This geometrical shape allows the connector 1 according to the invention to be inserted without inflicting unnecessary damage to surrounding organic tissue, while still achieving an excellent anchorage.
In a parti cularly preferred embodiment of the connector 1 according to the invention, as shown in Fig. 1, the first 2 and second 3 helical members are arranged symmetrically in relation to a longitudinal axis A of the open helical structure 9. Such an arrangement improves the anchorage in the organic tissue, and gives a more uniform force distribution when the organic tissue and the inserted connector 1 are subjected to a load.
In another advantageous embodiment, the connector 1 , in addition to the first 2 and second 3 helical members, comprises one or two additional rigid, helical members (not shown) of a bio-compatible material which also are part of the open helical structure 9. This embodiment can advantageously be implemented for skeletal bone or cartilage of a very poor quality, e.g. as a result of osteoporosis, in which a conventional device provides only a very poor anchorage. In this embodiment, the design with three or four helical members provides an improved anchorage, particularly when the skeletal bone into which the connector according to the invention has been inserted is subjected to axial loads, e.g. forces in the longitudinal direction of a femur.
In the particularly preferred embodiment, the connector 1 comprises a notch 10 or the like for enabling the head 8 to be separated from the rigidly connected helical members 2, 3 after insertion of the connector 1. In this context, the term "notch" should be understood as a weakened portion, between the helical members 2, 3 and the head, or in the head 8, which is designed in order to crack if a force of a certain magnitude or in a certain direction is applied.
Furthermore, in the particularly preferred embodiment, guide means 11 are provided for facilitating insertion of the connector 1. The guide means are preferably constituted of a guide wire 11 extending through the screw head 11 and the open helical structure 9, but
also other types of guide means which during insertion can guide the connector 1 in the desired direction are conceivable.
The above-mentioned helical members 2,3 are preferably dimensioned so that the open helical structure 9 obtains an overall diameter between 4 and 15 mm, and a length between
10 and 105 mm. However, it is also conceivable with embodiments with other dimensions.
In the following, a preferred embodiment of a method for repairing a fracture in organic tissue will be described with reference to the attached Figs. 1 and 2.
The metliod according to the invention comprises to make an incision and to insert a connector 1, using a tool (not shown), through a first organic tissue portion 12 across a fracture 13 into a second organic tissue portion 14. Thereby, the connector 1 comprises at least first 2 and second 3 rigid, helical members of a bio-compatible material, wherein each helical member 2, 3 has a first end with an insertion tip 4, 5 and an opposite, second end
6, 7,
In the method according to the invention, the second ends 6,7 are rigidly connected to each other and to a head 8. Thereby, the helical members 2, 3 together form an open helical structure 9 which, during insertion and starting with the insertion tips 4, 5, gradually is accommodated within the organic tissue portions 12, 14 as a result of the head 8 interacting with the tool.
The method according to the invention further comprises to close the incision, and to allow the fracture 13 to heal with the organic tissue portions 12, 14 fixated in relation to each other by the connector 1 ; 1'.
In the preferred embodiment of the method according to the invention, the head 8 is separated from the helical members 2, 3 at a notch 10 or the like, and said head 8 is removed from the connector 1 ' after insertion.
Furthermore, in the preferred embodiment, guide means 11 (e.g. a guide wire) guide the connector 1 during insertion, and are removed from the connector 1' after insertion.
In the preferred embodiment, the tool generates a rotary motion of said helical structure 9 around a longitudinal axis A of said helical structure 9 during insertion.
In a particularly advantageous embodiment of the method according to the invention, after having been inserted, the connector passes through portions of the organic tissue being of several of the following types: bone fragments, cartilage, bone marrow, tendons, ligaments or muscles. In this embodiment, the excellent anchorage properties of the connector, also in completely different organic tissue types, are utilised to their full extent.
The present invention should by no means be regarded as being limited to what has been described in the foregoing in connection with the different embodiments, or to what is shown in the attached drawings, but the scope of the invention is defined by the following claims.
Accordingly, within the scope of the invention, it is also conceivable with embodiments in which the head 8 is allowed to remain also after insertion of the connector 1 into the organic tissue, or embodiments in which no guide means 11 are utilised.
The physical properties of the organic tissue in question decide which diameter and slope (numbers of turns per unit length) the helix members 2, 3 according to the invention should have.
Furthermore, after the insertion of the connector according to the invention into an organic tissue structure, bone transplants or compounds which stimulate bone-growth can advantageously be implanted/inserted into the porous organic tissue structure or possible cavities which is/are enclosed by the open helical structure.