Bone anchor locking device
View Patent ↗A bone anchor locking device for receiving a bone anchor having a shank and an enlarged head, the device has a bone anchor, a dome and a conical split washer. The receiving portion has a base extending radially outward and inwardly to a wall. The dome has a center aperture sized to pass a bone anchor. The split washer has an inner conical surface sloped to slide and expand against at least a portion of the base on insertion of a bone anchor to allow a maximum diameter of a head of a bone anchor to pass and thereafter the split washer retracts overlying the maximum diameter of the head to prevent a bone anchor from backing out.
1. A method of releasing a bone anchor that has been fully inserted and locked in a bone anchor locking device comprising;
placing a tubular tool with a chamfered end against an inner diameter surface or edge of a conical split washer;
pressing the tool inwardly expanding the washer as the inner surface or edge of the washer slides at least partially along a base of the locking device to a diameter larger than a screw head to unlock the bone anchor;
increasing an inside diameter of the tool; and
removing the bone anchor by unthreading the bone anchor and passing it through the tool.
2. The method of claim 1 wherein the step of increasing the tool diameter includes removing an inner sleeve leaving a larger diameter outer sleeve.
3. The method of claim 1 wherein the base is conically sloped.
4. A method of releasing a bone anchor that has been fully inserted and locked in a bone anchor locking device comprising;
placing a tubular tool with a chamfered end against an inner diameter surface or edge of a conical split washer;
pressing the tool inwardly expanding the washer as it slides at least partially along a base of the locking device to a diameter larger than a screw head to unlock the bone anchor;
expanding the split washer to a diameter larger than a rim or lip diameter;
pushing the washer against a wall of a rim or lip;
increasing an inside diameter of the tool; and
removing the bone anchor by unthreading the bone anchor and passing it through the tool.
5. The method of claim 4 further comprises increasing the inside diameter of the tool prior to unthreading the unlocked bone anchor.
6. The method of claim 4 wherein the base is conically sloped.