Fixation screw

Details Fixation screw Fixation screw

1992-08-03

1994-08-02

Hafer, Robert A.

Surgery

Instruments

Orthopedic instrumentation

606 79, A61B 1756

Patent

active

053342046

ABSTRACT:
A fixation screw for attaching to a bone has at least one flute which traverses the proximal portion of the thread to form reverse cutting faces on the thread at the proximal portion. The cutting faces are arranged to cut the bone when the screw is rotated in a reverse rotational direction to ease in withdrawal of the screw. The flute forms a first plane containing the cutting faces on the thread and the axis of rotation of the screw. A base surface is formed by the flute forwardly of the cutting faces when the screw is rotated in a reverse direction. The base surface includes a rotational portion at the root diameter of the thread and a planar portion in a plane tangential to the rotational portion and arranged so that a substantial portion of the cutting face is axially offset from the leading thread to thereby engage the bone. Additionally or optionally, the thread is tapered at the proximal end to form a reverse self-tapping thread.

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Smith & Nephew Richards, 1992 Orthopaedic Catalog, pp. H2 and H5.
Zimmer Inc., MAGNA-Fx Cannulated Screw Fixation System Catlog. Aug. 1989.
Howmedica, 1991 Product Catalog, p. H8.
Synthes (U.S.A.), The Large Cannulated Screw System, 1989.
Synthes (U.S.A.), 1987 Catalog with 1990 Supplement, pp. 2-595, 1990.
1 sheet illustrating screws from Synthes, Howmedica, Zimmer and Richards.

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