There are a variety of anchors used to fix the ends of an ACL prosthesis into bones. Most commonly, they are so-called interference screws, designed to be inserted along the prosthesis (transplanted tendon or ligament, or an artificial ligament) within an anchor hole, or tunnel, drilled in the bone. The interference screw jams the prosthetic tissue against the bone within the anchor hole. Another common technique is so-called cross-pin used to anchor a loop of the prosthetic tissue within a hole drilled in the femoral condyle. In all cases, prosthetic tissue exits the tunnel by bending over the edge of the bone; healing/remodeling of the bone is expected to fill the gaps and to result in a natural-like anchorage of the ligament in the bone. Neither of these techniques is suitable for a permanent anchorage of an artificial ACL replacement. Bending of the prosthesis over the edge of the hole will lead to both, bone loss due to contact resorption and mechanical damage—ultimately failure—of the prosthesis due to bending and wear at the edge of the hole.
The present inventor has an improved apparatus and method for fixing the ends of an ACL prosthesis. The bone anchor is disclosed in U.S. patent application Ser. No. 12/107,070 filed on Apr. 21, 2008. The bone anchor includes a central hole through which the ACL prosthesis is passed. A knot is tied in the end of the ACL prosthesis to retain it within the central hole. The central hole is sized to prevent the knot from pulling through. However, sometimes the knot may pass through the central hole causing the ACL prosthesis to loosen or fail. Additionally, tying the knot can be difficult while retaining the ACL prosthesis taut. Accordingly, an improved method for retaining the ACL prosthesis within the central hole would be advantageous.
Additionally, a bone screw may be used for attaching a suture to bone for other purposes. A lateral suture screw for attaching a suture is disclosed in U.S. patent application Ser. No. 12/107,071 filed on Apr. 21, 2008 by the present inventor. The lateral suture screw includes a post extending above the screw. An attachment hole is formed in the head of the post for attaching the suture. The suture is connected to the attachment hole with a knot. As with the bone anchor the knot may pull through the attachment hole. Therefore, a need exists for an improved suture screw and mechanism for attaching the suture to the screw.