Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Ligament or tendon
Patent
1989-08-16
1992-01-07
Isabella, David J.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Ligament or tendon
A61F 208
Patent
active
050787454
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a new type of synthetic ligament particularly designed for replacing the anterior cruciate ligament of the knee.
The anterior cruciate ligament of the knee joins the intercondylar area of the tibia to the intercondylar fossa of the femur. Its principal role is to check the forward slipping of the tibia, that is to say, to reduce the anterior drawer movements.
Orthopedic surgery of the knee has progressed greatly in recent years and there is an increasing tendency to offer ligament replacement prostheses.
Replacement prostheses for the anterior cruciate ligament in the knee proposed heretofore consist of a single bundle of synthetic fibers or groups of synthetic fibers which all terminate at one and the same site at each of the ends of the bundle. This prosthesis makes it possible to replace the anterior cruciate ligament and to limit the anterior displacement of the tibia under the femur created by the connection of the ligament to be replaced.
However, this system with a single bundle of fibers or groups of fibers limits this drawer movement only at certain degrees of flexion. In effect, a single bundle of fibers does not provide isometric tension of the synthetic ligament at every degree of flexion, i.e., tension without shortening the ligament. Such a ligament is described in one of the embodiments of a surgical instrument designed for placement on the joints of such ligaments in French Patent Application A 2 2598 311. This ligament is single-stranded and, when placed in the joint, goes through a simple back-and-forth movement from the anterointerior surface of the tibia around a point of anchorage in the femur. In this way, as a result of the independence of the forward-moving strand in relation to the return strand, stresses are never transmitted from one strand to the other, which reduces the resistance of the strand under stress and hence its useful life. In addition, this ligament, such as described, in no way prevents the anterior drawer movements of the tibia under the femur.
In point of fact, the inability of a single-stranded ligament to limit the anterior drawer movements of the tibia under the femur is inherent in the variation of the radii of curvature of the femoral condyles at the lower end of the femur, the condyles being in contact with the tibia in the glenoid cavity. These radii vary from front to back, also producing a front-to-back displacement of the instant flexion-rotation centers of the knee during flexion. Put differently, because of the presence of the femoral condyles with variable curvature radii and also because of the nonphysiological elasticity of these synthetic ligaments, continuous isometric tension of such a single-stranded ligament cannot be achieved.
It was then proposed to resort to two single-stranded ligaments to overcome this overwhelming drawback. U.S. Pat. No. 4,411,027 describes a patellar suture material made from two individual strands. Actually, it uses not one, but two, suture materials. These two materials are placed ahead of the knee joint by the classic "bracing" technique, which means that one of the suture materials simply goes around two points of support placed, respectively, on the quadriceps tendon (at the lower end of the anterior muscle of the thigh also known as the quadriceps) and on the tibia, and describes an oval, and the other one, also attached through the two points of support mentioned above, describes an 8. To this day, this technique is well known in connection with patellar tendon repair. However, it has some considerable disadvantages. First of all, the fact that several suture materials are used means that, when the joint is working, one of the strands slides in relation to the other, and as a result produces friction. This is certainly favorable for the healing of the patellar tendon, but causes premature and redhibitory wear of the strands as they pass through the tendon and the tibia, and in no way permits them to act as a prosthetic device. Next, as in the previous case, because the two strands
REFERENCES:
patent: 4411027 (1983-10-01), Alexander et al.
patent: 4863471 (1989-09-01), Mansat
Collomb Jean
Rhenter Jean-Luc
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