Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2001-09-17
2004-06-29
Reip, David O. (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S075000, C606S104000
Reexamination Certificate
active
06755834
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a fastener for securing a bone flap to surrounding bone and, more particularly, to a fastener for securing a bone flap to the cranium.
2. Description of Related Art
A craniotomy is a procedure wherein a portion of the cranial vault is surgically removed to provide access by the surgeon to the inside of the head and brain. Generally, to perform the craniotomy several burr holes are drilled through the skull and then the holes are connected using an osteotomy saw to cut the skull along a line of separation connecting the adjoining burr holes. Typically, the number and position of the burr holes will vary depending on the size and shape of the bone flap to be removed. For example, if one desired to remove a triangularly shaped bone flap then it may be practical to drill three burr holes to form a triangle and then use the osteotomy saw to connect the corners of the triangle for removal of the bone flap. Once the cuts have been made, the bone flap can be lifted from the underlying dura matter to expose the brain or other portion of the head. The bone flap may be removed entirely or folded back in a flap along one uncut or partially cut edge.
Once the operation has been completed, the surgeon will typically replace the bone flap to protect the underlying brain. An approach for reattaching the bone flap to the cranium may comprise drilling holes into the bone flap and surrounding cranium near the osteotomy and, subsequently, using stainless steel wire or silk sutures to reattach the bone flap to the holes. However, this procedure may be time consuming in that numerous holes must be drilled and, additionally, the drilling procedure may increases a risk of infection. At the same time, sutures have been known to become unstable and even to break which can also lead to dangerous movements of the bone flap against the brain. Furthermore, suture materials may leave irregularities in the skin surface and may fail to align the bone plate in a substantially planar fashion relative to the surface of the cranium.
Bone flap fastening devices that do not utilize sutures have been known in the prior art. One such device is described in U.S. Pat. No. 5,707,373 to Sevrain et al. This patent discloses the use of two interlocking pieces that form a cap and base structure to attach the bone flap to the cranium. The cap and base structure described therein extends from the burr hole over the cranium to secure the bone flap. Such a device may still be prone to movement of the fixation device such as “backing out” or loosening of the cap and the base. Accordingly, the need for a relatively safe, secure and easy to place cranium fixation device that is also aesthetically pleasing remains.
SUMMARY OF THE INVENTION
The cranial flap fixation device of the present invention utilizes a two or three piece design for attachment of a bone flap or bone plate to a cranium. The two piece design comprises in one embodiment an inner member and an outer member. The inner member comprises a head and a shaft and the outer member comprises a nut for attachment onto the shaft. A driving tool may be engaged with the outer member for manipulation of the outer member to thereby provide a secure engagement of the outer member with the inner member.
In a further embodiment, the inner member comprises a bolt, and the outer member comprises a nut and a lock washer. When utilized, the lock washer of the present invention is engaged and biased between the nut and an edge of the burr hole. The nut imparts a downward force onto a generally radially-inwardly located portion of the lock washer, and the edge of the burr hole imparts an upward force onto a radially intermediate portion of the lock washer. In accordance with one aspect of the present invention, the lock washer is constructed of a plastic or other semi-rigid material. The downward and upward forces exerted by the nut and the burr hole edge, respectively, place a bind on the lock washer and help to prevent the lock washer and nut from loosening or backing out. The fixation device of the present invention can further utilize a driving tool for engagement with the nut and for optional engagement with the lock washer. The fixation device of the present invention may further reduce a potential of over torquing the nut, thereby attenuating a possibility that the nut or bolt will be stripped or otherwise damaged.
These and other aspects and advantages of the present invention are set forth in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.
REFERENCES:
patent: 5707373 (1998-01-01), Sevrain et al.
patent: 5800436 (1998-09-01), Lerch
patent: 6068631 (2000-05-01), Lerch
patent: 6146384 (2000-11-01), Lee et al.
patent: 6179839 (2001-01-01), Weiss et al.
patent: 6258091 (2001-07-01), Sevrain et al.
patent: 6270500 (2001-08-01), Lerch
patent: 6328743 (2001-12-01), Lerch
patent: 6379363 (2002-04-01), Herrington et al.
patent: 2002/0016593 (2002-02-01), Hearn et al.
Reip David O.
Shumaker & Sieffert P.A.
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