Surgery – Instruments – Surgical mesh – connector – clip – clamp or band
Reexamination Certificate
1999-07-29
2001-03-06
Hirsch, Paul J. (Department: 3732)
Surgery
Instruments
Surgical mesh, connector, clip, clamp or band
C606S075000
Reexamination Certificate
active
06197037
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a surgical fastener for joining two adjacent portions of bone, for example, when replacing a portion of the cranial vault removed during a craniotomy, and a related method of using the surgical fastener.
BACKGROUND OF THE INVENTION
In most neurosurgical and cranial operations, it is necessary to open a large access hole in the skull by forming a segment of the skull, called a bone flap, which is then bent out of the way or broken out from the surrounding skull. To form the bone flap, several holes are typically drilled through the skull, commonly referred to as burr holes. The burr holes are then connected by one or more osteotomy cuts, for example by using a Gigli flexible saw which is passed internally between the burr holes. The saw is then oscillated back and forth to cut the skull along a path connecting adjoining burr holes. The position, number, and size of the burr holes drilled through the skull, as well as the number of connecting osteotomies, is determined by the size, location and geometrical form of the desired bone flap and corresponding access hole. For example, if the bone flap to be removed is a triangular skull cap segment, three holes are preferably drilled at the corner points of the bone flap, connecting osteotomies are made along the sides of the curved triangle delineated by burr holes, resulting in a triangular segment bone flap. The bone flap is subsequently lifted off the underlying dura matter to expose the brain for the further steps of the operation. The bone flap may either be completely removed from the surgical site, or folded back along an uncut edge.
At the end of the procedure, the previously removed bone flap or flaps are repositioned into their original locations, or in different desired locations, relative to the surrounding bone portions. This is typically accomplished in the prior art by drilling pairs of small holes in the surrounding skull bone in several places around the edge of the bone flap. Wire is then carefully threaded through the holes, taking care not to tear the dural tissue covering the brain, then twisted together to secure the edges, the ends tucked into the osteotomy cut opening so that they do not puncture the skin, and the skin then stitched into place over the skull flap. The procedure is complex and time consuming, and there always is the possibility of injuring the dura either by using the high speed drills that are necessary to form the small holes or by the sharp points of the wire engaging the dura.
Other known methods for providing fixation between adjacent bone portions have included the use of metallic plates of varying configurations which are secured across osteotomies or fracture sites by metallic bone screws. Other devices, such as intramedullary nails, have also been used to reduce bone fracture mobility and to improve the relative position of adjacent segments. See for instance U.S. Pat. No. 5,669,912 to Spetzler, U.S. Pat. No. 5,549,620 to Bremer, and U.S. Pat. No. 5,916,217 to Manthrop. The aim of fixation of adjacent bone portions is to immobilize the fracture or osteotomy sites in order to promote localized bone growth in the natural repair of the separation.
A brief survey of prior art methods may be found by looking at patents previously issued on the subject. For instance, U.S. Pat. No. 5,201,737 discloses a flexible plate having a plurality of vanes with holes for receiving bone screws. The plate is placed over a cranial burr hole and adjoining osteotomy lines to provide external fixation of the bone flap to the surrounding cranium. Other external bone plates are shown in U.S. Pat. Nos. 4,651,724; 4,923,471; 5,139,497; 5,372,498; and 5,578,036. All of these plates are designed for external application to fractured bones and require placement of a plurality of screws through the plates and into the bone. Placement of multiple screws through the plates is time consuming, induces additional trauma in drilling the pilot holes for the screws, and may predispose the site to infection.
In spite of the use of a variety of fasteners in surgical procedures, improved techniques are still being sought to secure adjacent portions of bone for healing, particularly for securing bone flaps to the surrounding cranium following a craniotomy.
SUMMARY OF THE INVENTION
The present invention utilizes a surgical fastener, frequently referred to herein as a bone clamp, to join adjacent bone portions. The bone clamp typically includes a top flange and a bottom flange joined by a rib, or rib assembly, that together help define two bone receiving cavities. The edge of each of the adjacent bone portions is inserted into the respective bone receiving cavity and gripped by the compressive action between the top flange and the bottom flange. In the installed state, the top flange is disposed on one side of the bone portions while the bottom flange is disposed on the opposite side of the bone portions, with the rib disposed between the bone edges.
In one preferred embodiment, the bone clamp is a unitary device that is made from a flexible bioresorbable material. Due to its configuration, the bone clamp may be installed without the use of any tools. Further, the bone clamp acts as a temporary fastener in that it dissolves over time, thereby allowing for the bone edges to knit, even in the vicinity of the bone clamp. In addition, due to their flexibility the bone clamps transfer a portion of the radial stress exerted on the bone flap to the bone itself. As the bone clamp dissolves, a greater and greater portion of the radial load is transferred to the bone. It is believed that this stress transferring approach promotes better bone healing than approaches that rely primarily on supporting the stress via a rigid fastener.
Thus, in the preferred embodiments, the bone clamp provides a safe, simple, easy to use fastener for temporarily joining adjacent portions of bone. The bone clamp does not require the use of a drill or screws to install. When installed, the bone clamp has a low profile initially and no long term profile, thereby lessening cosmetic abnormalities.
REFERENCES:
patent: 4050184 (1977-09-01), Chiari
patent: 4058909 (1977-11-01), Poleri
patent: 4122583 (1978-10-01), Grittner et al.
patent: 4176428 (1979-12-01), Kimura
patent: 5456714 (1995-10-01), Owen
patent: 5885284 (1999-03-01), Erico et al.
patent: 6022351 (2000-02-01), Bremer et al.
patent: 6068631 (2000-05-01), Lerch
Coats & Bennett PLLC
Hirsch Paul J.
Priddy Michael B.
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