Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Ligament or tendon
Reexamination Certificate
1997-11-21
2003-09-09
Prebilic, Paul B. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Ligament or tendon
C623S013150, C623S023520, C606S066000, C606S075000
Reexamination Certificate
active
06616694
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention pertains to surgical systems and, more particularly, apparatus and methods for attaching autologous or artificial tendon grafts to bone. The invention has application in, for example, repair of the anterior cruciate ligament (ACL) of the knee. It may also be used, for example, for repair of other ligaments, such as of the elbow or ankle.
It is not uncommon for ligaments and other soft tissue to tear or detach from bone. Athletes, for example, often suffer tears or other injuries to the anterior cruciate ligament, one of the ligaments connecting the femur (thigh bone) and the tibia (shin bone) at the center of the knee joint. The ACL, which limits hyperextension of the knee and prevents the backward sliding of the femur on the tibial plateau, may be injured when the knee is twisted beyond the normal range of motion, e.g., when the knee is twisted while bending and weaving during skiing and other sports activities. ACL injuries may take the form of total or partial tears.
Reconstruction is the most common form of surgery for injuries to the ACL and involves replacing the ACL with a graft of autologous or artificial tendon. An autologous tendon graft may be “harvested” from the patient's patellar ligament, which is part of the common tendon of the quadriceps femoris, connecting the patella to the tibia. An alternative autologous tendon graft may be harvested from the semitendinosus tendon, which runs posteriorly and medially along the thigh and which connects the upper femur to the tibia.
Traditionally, patellar grafts are harvested with attached bone plugs that can be securely fixed at the ends of a bone tunnel drilled through the tibia and femur using a metallic interference screw, a metal screw and washer, or buttons. Drawbacks associated with the use of the patellar tendon include difficulties in harvesting the tendon and postoperative complications.
More recent success has been achieved using one or more strands of the triple-stranded semitendinosus tendon, which can be harvested with minimal post-operative complications. The strands can be used alone or in combination with the gracilis tendon, which anatomically runs parallel along the thigh to the semitendinosus tendon. Although semitendinosus tendons are increasingly used in ACL repair, they are difficult to attach to bone, due in part to the absence of associated bone plugs.
The art suggests several techniques for attaching the semitendinosus tendon to bone in ACL repair. One such technique involves suturing the tendon to a button or staple on the exterior of the bone. Drawbacks associated with this method include stretching or failure of the suture, which may be subjected to tensile forces ranging from 30-50 pounds.
Another technique involves attaching a tendon graft to bone using metallic screws. Although such metal screws demonstrate stable fixation and good tensile strength, they have a number of drawbacks. These include distortion of post-operative radiological studies, an allergic or rejection reaction resulting from metal sensitivity associated with permanently implanted metal screws, and the potential need for additional operations for removal or replacement.
Another technique involves attaching a tendon graft to an anchor affixed within a tunnel drilled in the bone. One anchor intended for this use is the Mitek Ligament Anchor available from Mitek Surgical Products, Inc. That anchor includes prongs that lodge into the bone after the anchor has been pulled into position by a suture. A drawback of that anchor is that it must be lodged in the cortical layer near the surface of the femur and therefore necessitates the use of long tendon segments. In addition, the anchor's design necessitates that it be fabricated from metal to ensure sufficient holding strength.
An object of this invention is to provide improved surgical systems, and more particularly, improved methods and apparatus for attaching autologous or artificial tendon grafts to bone.
Another object of this invention is to provide improved methods and apparatus for attachment of autologous or artificial tendon grafts (e.g., for ACL repair) that are in which the attachment means can be fabricated from polymers or bioabsorbable materials, without the use of metals.
A related object of this invention is to provide methods and apparatus for attachment of autologous and artificial tendons that minimize or eliminate the risk of graft pullout normally associated with ACL or other reconstructive orthopedic surgery.
SUMMARY OF THE INVENTION
The above objects are among those met by the invention, which provides improved methods and apparatus for attaching autologous or artificial tendon grafts to bone, e.g., during ligament and other reconstructive surgery, including ACL reconstruction. These allow anchoring the tendon graft in the bone, without metal and without placing undue load on sutures.
In one aspect, an assembly according to the invention comprises an insertion element and a stabilizing element. The stabilizing element has an outer surface adapted for interference fit with a bone hole. The insertion element includes an aperture through which a graft may be threaded or attached, and a stem adapted to be inserted into and retained in a cavity in the stabilizing element, e.g., by an interference fit. Additionally, the insertion element may comprise an aperture, slot, or barb, preferably at its distal end, to facilitate its insertion into the stabilizing element.
According to one aspect of the invention, the stabilizing element has a threaded outer surface that can be securely turned into the bone. In addition, the stabilizing element can have an inner bore that is smaller than the outer diameter of the insertion element, such that placement of the latter into the former causes the stabilizing element to deformably expand or otherwise obtain a still stronger pressure fit with the bone hole.
In another aspect, the invention provides a stabilizing element that has a flanged head that rests on the surface of the bone, outside of the bone hole, and that prevents the element from entering the bone hole beyond a certain point.
In further aspects of the invention, the insertion and stabilizing elements comprise bio-compatible materials. These avoid adverse biological reactions to the elements, as well as the need for a second surgical procedure to remove the elements.
A related aspect of the invention comprises a system comprising two or more anchoring assemblies as described above. Such a system can be used with one or more natural or artificial grafts to repair or strengthen a skeletal bone or joint. In ACL repair, for example, one stabilizing element can be placed at one end of a bone hole drilled into the femur, and the other stabilizing element can be placed in an aligned tunnel drilled into the tibia. The first and second insertion elements can then be joined by the graft and inserted into their respective stabilizing elements. The stabilization element placed in the femur can be of the type having a threaded outer surface, while that emplaced in the tibia can be of the type having a flanged head. Such a configuration exploits the strong cancellous matter in the femur, which is well adapted to holding screw threads, and relies on the surface of the tibia to ensure a hold there.
Another aspect of the invention comprises a method for anchoring a graft in bone, for example for the replacement of a torn ligament. In this method, a tunnel or opening is drilled into the bone, and a stabilization element of the type described above is placed therein. A graft is looped through the head of an insertion element which, in turn, is inserted into the stabilization element. The insertion and stabilization elements may incorporate various structures designed to more effectively dispose and/or secure them in the bone tunnel, as described above. For example, the stabilization element may comprise a flanged head which prevents it from being pulled into the bone tunnel when tension is applied to the tissue graft after insertion o
Ethicon Inc.
Nutter & McClennen & Fish LLP
Prebilic Paul B.
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