Many drill guide assemblies are known by which a wire may be inserted into a bone at a predetermined position, which wire, after insertion, will provide a guide for a cannulated drill driven by a drill motor by which a passageway can then be formed in the bone to afford such procedures as ligament replacement. Typical examples of such drill guide assemblies are The Nisonson Wire and Drill System sold by Stryker, Kalamazoo, MI; The Richards Arthroscopic Ligament Drill Guide Set sold by Richards Medical Company, Memphis, TN; the Techmedica Ligament Installation System sold by Techmedica, Camarillo, CA; The Vector Guide to the Knee System, sold by Dyonics, Inc. Andover, ME; The Bow and Arrow sold by Instrument Maker, Inc., Okemos, MI; The Arthroscopic Drill Guide Set sold by Arthrex Arthroscopy Instruments, Inc., Norwalk, CT; and the Variable Radius Drill Guide System sold by Arthrex Arthroscopy Instruments, Norwalk, CT.
Of these assemblies, the last three have the closest structures to the structure of the present invention in that they both include (1) a probe having a target end and an opposite threaded end portion, (2) a cannular elongate cylindrical wire guide having a central through opening adapted to receive and guide a wire, (3) a body generally arcuate about a predetermined point, having a first end portion with a through bore adapted to closely receive the wire guide for longitudinal sliding action with the axis of the wire guide aligned with the predetermined point, and having a second end portion adapted to receive the threaded end portion of the probe with the target end at the predetermined position and a part of the threaded end portion accessible from the side of the body opposite the predetermined point on which an attaching member is engaged to secure the probe on the body, and (4) means for preventing longitudinal movement of the wire guide through the bore away from the predetermined point.
These last three prior art drill guides have several structural deficiencies, however, which are as follows:
(1) The body of each has a cross section that is elongate in a direction at a right angle to the axes of the probe and wire guide. Thus, the portion of the body available to accurately anchor and align the probe and wire guide is relatively thin, and forces tending to deflect the distal ends of the probe and wire guide can more easily bend the body than might otherwise be the case.
Also, in the last two of these prior art drill guide assemblies, the second end portion of the body in which the probe is fixed is slotted, which, while providing a wide range of adjustments for the angle of the probe with respect to the drill guide, does not provide sufficiently precise support for the threaded end portion of the probe so that the target end of the probe will always be positioned with the accuracy that is desired.
(2) The end surfaces of the wire guides that are intended to contact a bone into which the wire is to be inserted are disposed generally at right angles to the axes of the wire guides. Thus, when a wire is inserted into a bone at an angle to the surface of the bone (which is quite often done, typically at an angle of about 45 degrees or less between the surface of the bone and the axis of the wire guide), only an edge (which edge may be toothed to help retain its position on the bone) of the wire guide contacts the bone and when the wire is inserted into the bone the tip of the wire is not supported between the end surface of the wire guide and the surface of the bone on the side of the wire guide toward which the end of the wire can be deflected by contact with the relatively hard surface of the bone. This unsupported distance is significant because of the angle of about 45 degrees or more that also typically exists between the end surface of the wire guide and the surface of the bone. If the thus unsupported end of the wire strikes and is deflected by the outer surface of the bone, it will enter the bone at the wrong place and thus will not be inserted along its intended path. In some drill guide assemblies this unsupported space is minimized in that the end of the drill guide adapted to contact the bone is tapered to a thin edge. Such thin edges tend to bend or dull with use, however, so that accurate positioning of that end becomes difficult. Other drill guide assemblies have wider and thus stronger end surfaces, however, the width of such an end surface increases the unsupported distance described above.
(3) The means for preventing longitudinal movement of the wire guide through the bore away from the predetermined point is a manually operated set screw which can be difficult to tighten during an operation while maintaining a desired relative position between the body and wire guide.