Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2001-04-23
2003-07-08
Reip, David O. (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S075000, C606S104000, C606S213000, C411S338000
Reexamination Certificate
active
06589244
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fastener for securing a bone plate to surrounding bone, for example when replacing a portion of the cranial vault removed during a craniotomy for a neurosurgical procedure. The invention also relates to an instrument for securing two threaded members to each other. The instrument may be used during neurosurgical procedures, or as a mechanical tool in many other contexts.
2. General Discussion of the Background
A craniotomy is a surgical procedure in which a portion of the cranial vault is removed or folded back in a flap to permit surgical access to the cranial contents (such as the brain). To perform the craniotomy, several burr holes are drilled through the skull. The number and position of these holes varies depending on the shape of bone to be removed. For example, three burr holes are drilled at corner points if a triangular bone flap is desired. The burr holes are then connected by osteotomy cuts, for example 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 line of separation (defined by the connecting osteotomies) connecting adjoining burr holes. The bone cover is subsequently lifted off the underlying dura mater to expose the brain. The bone cover may either be completely removed from the surgical site, or folded back in a flap along an uncut edge of the flap.
After completion of the operation, the bone cover must again be fixed in its original position to protect the underlying brain. Conventional craniotomy closure requires that holes be drilled in the bone plate and surrounding cranium along the osteotomy lines, and stainless steel wire or silk sutures are then passed through the holes to retain the plate in place. Unfortunately, drilling the holes is time consuming and potentially dangerous, because of the risk of introducing infection. The sutures are also unstable and prone to breakage. Suture instability or breakage can lead to dangerous movements of the cranial plate against the brain, with pathologic sequelae similar to a depressed skull fracture. The sutures closing the osteotomy lines are not aesthetically pleasing, because they can leave irregularities in the overlying surface of the face or scalp. This irregularity is particularly unsightly if the surface of the bone plate is not held substantially co-planar with the surrounding bone.
Various fixtures have previously been proposed for securing the bone cover to the surrounding cranium. 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 cover to the surrounding cranium.
Other external bone plates are shown in U.S. Pat. No. 4,651,724; U.S. Pat. No. 4,923,471; U.S. Pat. No. 5,139,497 and U.S. Pat. No. 5,372,498. All of these plates are designed for external application to fractured bones, and require placement of a plurality of screws through the plates. As with the plate in U.S. Pat. No. 5,201,737 discussed above, placement of multiple screws through the plates is time consuming, predisposes to catastrophic infection, and is difficult to remove once in place.
A variety of fixation devices are also known for fusing fractured bones. An example of such a device is U.S. Pat. No. 2,511,051, in which an externally threaded stud screws into an internally threaded shank. Movement of the stud into the shank is guided by an hexagonal wrench that is inserted through the shank into a countersunk receptacle on the tip of the threaded stud.
U.S. Pat. No. 3,875,936 shows an attachment for replacing a trochanteric head to the femur by providing a barbed shear washer between the femur and trochanteric head. U.S. Pat. No. 5,098,433 uses a winged compression bolt for fusing fractured bones. U.S. Pat. No. 5,196,016 and U.S. Pat. No. 5,433,719 discloses fixation pins or screws for retaining bone fragments against one another.
In spite of the use of a variety of fasteners in orthopedic and neurosurgical procedures, improved techniques are still being sought to secure a cranial cover to the surrounding cranium following a craniotomy. Improved methods and devices for securing the fasteners to the skull are also disclosed.
Accordingly, it is an object of the present invention to provide a fastener that is especially suitable for closure of craniotomies.
Yet another object is to provide such a fastener that can be quickly and efficiently installed, and which is capable of easy removal in the event that subsequent intracranial access is required for another neurosurgical procedure.
Yet another object of the invention is to provide such a fastener that avoids the aesthetic drawbacks of prior fasteners, such as large indentations in skin overlying the craniotomy.
It is another object of the invention to provide such a fastener, and an instrument for manipulating the fastener, that allows it to be easily inserted and removed, yet which provides a potentially permanent and reliable fixation of the cranial cover, thereby avoiding the potentially catastrophic neurological consequences that can result from dislodgement or depression of the cranial cover.
Finally, it is an object of the invention to provide an instrument that is useful for engaging first and second members to each other, particularly when the engagement must occur on opposite surfaces, and one of the surfaces is not easily accessible.
SUMMARY OF THE INVENTION
These and other objects are achieved by the bone cover fastener of the present invention, which has internal and external fastening members. At least one of the fastening members has a conforming surface that conforms to a curved surface, such as the inside surface of the cranial vault. In other embodiments, both the internal and external fastening members have conforming surfaces, such that a surface of the internal fastener conforms to the internal surface of the cranium, while the external fastener also has a surface that conforms to the external surface of the cranium.
In one embodiment, there is a connector on the internal fastening member and a connector on the external fastening member, and the connectors cooperatively hold the internal and external fastening members in a fixed relationship that fixes the bone cover in a defect from which the bone plate has been removed. The conforming surface may be a curved surface of the internal fastening member that seats against the inner face of the cranium. In particularly disclosed embodiments, the internal and external fastening members are curved plates that respectively conform to the internal and external curvature of the skull. Alternatively, the conforming surface may be provided by flexible struts that deform into a curved configuration as the fastener is tightened.
In other embodiments, a tab is provided on one of the fastening members to prevent relative rotation between the fastening member and the cranium. In particular, the tab is a relatively flat member that extends away from the internal fastening member a sufficient distance to be retained between the bone plate and the remaining cranium. The tab is sufficiently thin that it fits within the gap between the bone plate and surrounding cranium. When the external fastening member is rotated relative to the internal fastening members to interconnect threaded connectors, rotation of the internal fastening member is opposed by the tab which is retained within the gap formed by the cranial osteotomy incision.
One of the connectors may be an elongated, externally threaded stud that projects from the first fastening member, while the second connector may be an elongated internally threaded collar that projects from the second fastening member. The stud is rotationally threaded into the collar, with the collar extending between the fastening members. The collar fits through the burr hole of a craniotomy incision, and each fastening member is wider than the collar
Sevrain Christophe J. P.
Sevrain Lionel C.
Shearin Alan
Harness & Dickey & Pierce P.L.C.
Reip David O.
Walter Lorenz Surgical Inc.
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