Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-01-27
2001-02-13
Philogene, Pedro (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S067000
Reexamination Certificate
active
06187007
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a device for internal fixation of a bone fracture, and in particular to a device for fixation of a fractured femoral head.
BACKGROUND OF THE INVENTION
Such devices are generally known as “hip screws”. One such device is disclosed in German Patent Application No. A 41 06 876. The anchor screw disclosed in this application has only a single thread. U.S. Pat. No. 5,269,686 discloses a dental implant with a four-thread screw. However, the use of this dental implant for internal fixation of long bones is not taught or suggested. Finally, a femoral nail with a rotationally stable femoral neck screw is known from European Patent Application A 0 257 118. However, the nail only has a single thread.
All known prior art designs of hip screws suffer from the same disadvantage. Specifically, implantation causes substantial bone loss. As a result, any required revision surgery or subsequent second intervention is very difficult due to loss of bone. Thus, there exists a need for an improved hip screw.
SUMMARY OF THE INVENTION
The device according to the present invention has a body portion with a bone plate for attachment to the femur and a sleeve connected at an angle to the bone plate. The bone plate has screw holes for securing the bone plate to the femur. The device also includes an anchor screw having a shaft configured and dimensioned for sliding axial movement within the bore of the sleeve and a threaded coaxial section attached at an end of the shaft for securing the anchor screw in bone. The shaft may have a channel for receiving a guide wire to facilitate proper implantation of the anchor screw. The threaded section of the anchor screw has multiple threads, preferably at least four threads, and the shaft of the anchor screw has surface features which engage corresponding surface features of the sleeve to prevent rotation between the body portion and the anchor screw while allowing axial movement between the two.
The surface features of the shaft of the anchor screw may be ridges running longitudinally on the shaft and the surface features of the sleeve may be corresponding grooves in the bore of the sleeve.
In preferred embodiments, the outside diameter of the thread is between 10 mm and 14 mm. The threads may have a pitch of at least 50 mm and the cross-sectional area of the threaded section is between 10 mm
2
and 55 mm
2
. The threaded section may be configured as a core with wings forming a spiral around the core. The wings preferably have a thickness between 0.5 mm and 2.0 mm.
REFERENCES:
patent: 2121193 (1938-06-01), Hanicke
patent: 2627855 (1953-02-01), Price
patent: 3996931 (1976-12-01), Callender, Jr.
patent: 4103683 (1978-08-01), Neufeld
patent: 4441492 (1984-04-01), Rydell et al.
patent: 4494535 (1985-01-01), Haig
patent: 5116336 (1992-05-01), Frigg
patent: 5269686 (1993-12-01), James
patent: 5300074 (1994-04-01), Frigg
patent: 5324292 (1994-06-01), Meyers
patent: 5908422 (1999-06-01), Bresina
patent: 587317 (1933-10-01), None
patent: 757951C (1953-11-01), None
patent: 41 06876 A1 (1991-09-01), None
patent: 0257118 A1 (1986-08-01), None
patent: 0411273 A1 (1991-06-01), None
patent: 491 138 A1 (1992-06-01), None
patent: WO 91/09572 (1991-11-01), None
Frigg Robert
Schwyn Ronald
Pennie & Edmonds LLP
Philogene Pedro
Synthes (USA)
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