Importance

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Abstract

A fastener for anchoring in a bore in a bone has a screw extending along an axis and having a substantially cylindrical outer surface formed with a helical screwthread. The screw has at the screwthread a thread diameter and between the turns of the thread at the surface a root diameter smaller than the thread diameter. An anchor sleeve normally fitted in the bore and of an outside diameter corresponding generally to the diameter of the bore has an outer end formed with a laterally projecting rim normally lying against the bone around the bore, an outer end portion of an inside diameter greater than the root diameter but smaller than the thread diameter, and an inner end portion of an inside diameter smaller than the root diameter. Thus when the screw is threaded into the sleeve its thread cuts into the outer portion without substantially deforming and spreading same and into the inner portion with substantial outward deformation and spreading of same.

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First Claim