Drill guide with angle verification

Abstract

A method and instrument is used for inserting a bone screw into a hole in a bone plate and into bone at a maximum angulation of a bone screw central longitudinal axis with respect to a central axis of the hole. The maximum angulation is that which places the head of the bone screw at or below an outwardly facing surface of the bone plate. The instrument has a distal end including a gauge element, spaced proximally from an end surface of the distal end when in contact with a counterbore surrounding the plate hole. The space is less than or equal to a distance from the counterbore surface to the outwardly facing surface of the bone plate. The instrument is tilted with respect to a central axis of the bone plate hole to an angle wherein the gauge element remains at or below the outwardly facing surface of the bone plate adjacent the counterbore. A hole is drilled in the bone through a guide bore in the instrument.

Description

BACKGROUND OF THE INVENTION[0001]The invention relates to an angle guide for orienting a bone screw in a bone plate. More particularly, the invention relates to an instrument for insuring the position of the head of a bone screw located within a bone plate hole.[0002]It is often necessary when utilizing bone plates either for fracture fixation or such as tibial base plates to couple the bone plates to bone via a screw extending through a hole in the plate. When the screw is angled, surgeons have had to eye the correct angle specified by the device manufacturer indicated by the surgical situation. If the bone screw is put in at too great an angle the bone screw head would sit proud of the bone plate which in some situations is undesirable. The surgeon would then either continue to torque the bone screw until the bone screw's cutting flutes soften the bone in the area and allowed it to sit properly or the bone screw would be backed out and the surgeon would attempt to reinsert the bon...

AI Technical Summary

Benefits of technology

[0007]The visual reference may be a reduction in diameter, a protrusion, an etched line or a laser marked line. Also color and surface finish could be used as visual indicators. Additionally, two or three visual references could be used indicating different angle markings i.e. 5°, 10° or 15°. Thus two or three lines could be used at different levels with the lower line corresponding to the greater angle. The visual reference may be observed by the surgeon and indicates to him that the pilot hole angle he or she is about to drill through the device is compatible with the orthopedic implant, such as a bone plate, and the bone screw securing it. The instrument allows the proper pilot hole angle to be drilled through the device and the implant and allows a bone screw to have the proper angulation and therefore seat properly within the recess hole in the device so that the bone screw head sits correctly in reference to the plate, or in the case of a tibial baseplate below the surface of the plate.

Problems solved by technology

If the bone screw is put in at too great an angle the bone screw head would sit proud of the bone plate which in some situations is undesirable.

The surgeon often had difficulty eyeing the correct angle especially where there was a plurality of bone screws to be inserted, since the correct angle is relatively small i.e. zero to ten degrees.

Normally, the surgeon drills a pilot hole in the bone prior to inserting the bone screw and it has been difficult to drill the pilot hole at the correct angle so that the bone screw would seat properly.

Consequently, if the pilot hole and subsequent bone screw are inserted at an incorrect angle the head of the bone screw could impinge on the distal surface of the polyethylene bearing implant which is undesirable.

Such. an impingement could lead to metal or polyethylene debris which has been known to cause osteolysis.

However, since most bone screws include cutting flutes at the leading ends thereof continued rotation of the cutting flutes causes the bone to degrade and allows more play in the screws positioning.

While this may allow the bone screw to seat properly, it reduces the compressive forces holding the plate to the bone by decreasing the holding ability of the screw.

This method may not always be successfully since the drill and screw will have a tendency to follow the original drilled hole.

Even if the surgeon is capable of resetting the new desired angle, there is still damage to the bone in the originally drilled area which may cause fracture propagation.

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