A PROSTHETIC LIGAMENT

Abstract: A prosthetic ligament, particularly for replacing the medial collateral ligament and the lateral collateral ligament comprising a strip of fabric (10) preferably of non-uniform width which is twisted (18) through 180 DEG about a longitudinal axis. The ligament is fixed in position at or adjacent its ends (13, 14).

Description: A PROSTHETIC LIGAMENT This invention relates to a prosthetic ligament, particularly but not exclusively for replacement of the medial collateral ligament and lateral collateral ligament of a knee. It is often the case that when a knee is injured, the ligaments of a knee joint such as the anterior cruciate ligament, the medial collateral ligament and the lateral collateral ligament are damaged or ruptured. The prior art provides a structure for replacing a damaged anterior cruciate ligament in European Patent Application No.0126520. Prior art proposals have failed to provide a satisfactory artificial structure for replacing a damaged medial collateral ligament or a lateral collateral ligament and such methods that currently exist usually involve concurrently replacing the anterior cruciate ligament or the posterior cruciate ligament. The present invention has been made from a consideration of this problem. According to the invention there is provided a prosthetic ligament comprising a length of fabric characterised in that the fabric is twisted through at least substantially 180° about a generally longitudinal axis, attachment means being provided adjacent the ends of the fabric for mounting the prosthetic ligament in position. In a preferred embodiment of the invention the fabric is preferably of non-uniform width and preferably woven. In its untwisted condition the fabric preferably has the shape of a trapezium. The position of the twist is a matter of choice, but preferably it is nearer one end than the other. The fabric is twisted such that there is an even distribution of fabric about the axis of rotation. The fabric is preferably of an open weave construction. The transverse ends of the fabric are preferably considerably denser than the remainder of the fabric. For example with a greater number of picks per unit length. The attachment means may comprise mechanical fastening such as a washer and screw, or alternatively may comprise screws, staples, toggles and similar devices which pass through apertures provided in denser woven parts of the fabric and into the bone to which the ligament is to be attached. A specific embodiment of the invention will now be described with reference to the accompanying diagrams, in which:- Fig.l shows one embodiment of the invention; and Fig.2 shows diagrammatically the use of the embodiment of Fig.l for the repair of knee ligaments. Referring to the drawings, the prosthetic ligament 10 comprises a length of fabric 12 such as an open weave fabric or lace. The fabric 12 is of a trapezium shape. In this embodiment the length of the short side 13 of the trapezium is 15 mm and the length of the opposite side 14 is 30 mm. The lower portion 15 of the fabric 10 is twisted about the longitudinal axis of the fabric 10 such that the lower portion 15 is disposed at at least one 180° interval relative to the upper portion 16 of the fabric 10. The twisting of the fabric causes the warp yarns 17 to be collected at a single location 18 and each of the upper and lower portions 15, 16 of the fabric form triangles. This arrangement of warp yarns provides an even distribution of warp yarns on either side of the axis of rotation and thereby when the prosthetic ligament is attached across a joint such as a knee joint, will provide an even transmission of the load across the joint comparable to that occurring in nature. More twists may be provided at intervals along the central warp yarn. Additional weft yarns 19 are provided in the region 20 of the sides 13, 14 of the fabric 10. These additional yarns provide increased fabric density in these regions 20, 21 for improved anchorage to the bone. In use the arrangement as previously described is attached across the knee joint as shown in Fig.2 to replace either the medial collateral ligament or the lateral collateral ligament. Washers (not shown) with projections extending from the perimeter thereof are pushed into the bone 23, 24 through locations 22 in the regions 20, 21 of the fabric adjacent sides 13, 14. The projections thereby extend into the bone 23, 24 and maintains the fabric 10 in position. A screw is then passed through the open central portion of the washer and into the bone. Both the washer and screw are made from suitable material such as surgical stainless steel. Flexing of the knee joint causes longitudinal elongation of the fabric. As previously stated, the arrangement of the fabric as described provides an appropriate transmission of the load across the knee joint. Also, the open weave of the fabric allows tissue regeneration around the fabric. The fabric, therefore, acts as a scaffold for tissue regeneration. The invention is not restricted to the described specific embodiment and many modifications and variations can be made.

Claims: CLAIMS 1. A prosthetic ligament comprising a length of fabric characterised in that the fabric is twisted through at least substantially 180° about a generally longitudinal axis, attachment means being provided adjacent the ends of the fabric for mounting the prosthetic ligament in position. 2. A prosthetic ligament as claimed in Claim 1, wherein the fabric is of non-uniform width. 3. A prosthetic ligament as claimed in Claim 1 or Claim 2 wherein the fabric is woven, preferably of open weave construction. 4. A prosthetic ligament as claimed in any preceding claim, wherein the width of the fabric at one end is less than the width of the fabric at the other end. 5. A prosthetic ligament as claimed in any preceding claim, wherein the twist is formed at a location spaced from the mid point of the fabric. 6. A prosthetic ligament as claimed in Claim 4 and Claim 5, wherein the twist is formed nearer said one end than the other end. 7. A prosthetic ligament as claimed in any preceding claim, wherein the fabric is of substantially trapezoidal shape in the untwisted condition. 8. A prosthetic ligament as claimed in any preceding claim, wherein the ends of the fabric are more dense. 9. A prosthetic ligament as claimed in any preceding claim, wherein the attachment means comprises a mechanical fastening.

Inventors: ELLIS JULIAN GARTH, ELLIS, JULIAN, GARTH
Applicants: ELLIS DEV LTD, ELLIS DEVELOPMENTS LIMITED
Application year: 1990
Main classification: A61F2
IPC codes: A61F2