Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-04-28
2001-02-13
Buiz, Michael (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C623S022290
Reexamination Certificate
active
06187006
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to surgical instruments used by orthopedic surgeons to prepare a femur for implantation of a prosthesis, and more particularly to a surgical rasp tool which is securely locked during contouring operations, readily manipulated by the surgeon and easy to clean.
BACKGROUND OF THE INVENTION
Before the stem of a hip prosthesis can be inserted into the medullary cavity of the proximal femur, the medullary cavity has to be opened, after resection of the head
eck, and then reamed out and shaped to accommodate the stem that is to be inserted. This is done using a rasp, the stem of which is identical to the configuration of the prosthesis stem. The upper end of the rasp corresponds to the resection plane. Extending from the top of this upper end there is a peg whose direction follows that of the head
eck. This configuration permits a rasp instrument to be applied for the purpose of finishing the resection surface (EP-B-166,085); alternatively, a trial joint head can be placed thereon. The same applies to a trial stem. The rasp can also function as a trial stem.
To insert and release the stem, a grip part is provided which can be connected releasably to the stem via coupling parts. The grip part extends generally parallel to the direction of the stem (DE-U-94 07 621) so that hammer blows on its anvil-shaped end drive the stem home or remove it in substantially the longitudinal direction of the stem.
The coupling parts for connecting the stem to the grip part comprise the peg (described above) located at the upper end of the stem, and a bore located on the grip part which receives this peg. Since the peg extends in the head
eck direction, it protrudes obliquely to the side and away from the stem (in relation to the central longitudinal axis of the stem). To ensure that the lower end of the grip part can receive the stem, the grip part is generally angled off in relation to the direction of the rest of the grip part. Thus, most of the grip part extends with a slight lateral offset in relation to the stem, albeit essentially parallel to the longitudinal axis of the stem.
The coupling parts provided in known instruments of this type also comprise means for arresting the peg in the bore to secure the connection between the stem and the grip part. These arresting means are releasable so that the grip part can be detached from the peg. The known arresting means leave something to be desired. Arresting means designed as a screw connection have the disadvantage that the tightening and releasing of the screw takes some time. Also, such screw connections can come loose under the effect of the blows when the stem is being driven home or withdrawn. In arresting means designed as quick-action connectors, the activation means are typically provided in the immediate vicinity of the coupling arrangements. The disadvantage of such arrangements is that they have to be located and activated deep in the wound. This difficulty also arises in the case of a known instrument (DE-C 196 31 984) in which, in order to couple the stem with the grip part, S-shaped members on these coupling parts have to be brought into engagement before their engagement can be secured by means of a sleeve pushed over them. In yet another coupling arrangement (disclosed in a brochure entitled “Das PCA-Hüft-Total-System” from the company Howmedica Kiel), a lever engaging the coupling arrangements can be moved from outside the operating wound. Unfortunately, lever movement is very long, creating a substantial disadvantage given the confined space of the operating field. Finally, most of the known instruments of the type described have the disadvantage that their coupling arrangements are complicated and they are therefore difficult to clean.
Needs exist for surgical rasp tools that address the limitations of the existing instruments.
SUMMARY OF THE INVENTION
In view of the foregoing limitations and shortcomings of the prior art, as well as other disadvantages not specifically mentioned above, there still exists a need in the art for improved rasp tools. It is therefore a primary object of the present invention to fulfill that need by providing an orthopedic instrument that functions reliably, can be readily controlled from outside the immediate wound area, and is easy to clean.
More particularly, the present invention is a surgical instrument that includes a stem to be inserted into the medullary cavity of a proximal femur and a grip part slightly offset from and extending approximately parallel to the direction of the stem. The grip part is releasably connected to the upper end of the stem by mutual coupling parts including a peg protruding obliquely from the upper end of the stem and a bore located in the lower end of the grip part. Releasable means for arresting the peg in the bore are formed by the end of a rod which is guided movably in the longitudinal direction of the grip part and by a recess in the peg for receiving this end. The recess in the peg is a continuous bore, and the rod, in its arrested position, extends completely through the bore. The upper end of the rod is connected to a handle located in the middle to upper region of the grip part. The rod or the handle is provided with a catch mechanism for securing the rod in the arrested position.
One advantageous feature of the present invention is the releasable arresting means. As noted above, the releasable means for arresting the peg in the bore preferably includes a rod which is guided movably in the longitudinal direction of the grip part and whose end engages a corresponding recess of the peg. Known arresting means found in existing instruments include locking arrangements which engage the peg perpendicular to the peg direction. Since this peg direction is at an angle of approximately 45° to the longitudinal direction of the stem and of the grip part, the locking movement direction also extends obliquely, the result of which is that the activation of this lock arrangement must take place directly at the coupling arrangements or must be transmitted via relatively complicated transmission means. A significant difference between the present invention and previously known arresting arrangements lies in the fact that the present invention eliminates perpendicular lock movement. Specifically, in the present invention the lock lies in the longitudinal direction of the grip part, that is to say obliquely in relation to the peg, and is also moved in this direction. The recess provided in the peg for receiving the lock part is also oblique and is expediently designed as a continuous bore. This configuration is relatively straightforward. The parts interact in an uncomplicated manner and can be easily dismantled for cleaning. A particular advantage is that as a result of the parallel relationship between the rod and the grip part, the handle for moving the rod can be arranged at any desired point on the grip part, that is to say, at any desired distance from the operating wound at the end of the grip part remote from the stem, without detracting from the simplicity of construction or increasing space requirements.
The rod is expediently guided in a bore of the coupling part that is open at the bottom, so that it can be easily taken out for cleaning. For example, access to the indented end of the rod is provided through the open bottom of the bore, thereby allowing a screwdriver or other tool to be inserted for unscrewing and releasing the rod from its handle. Above the coupling part, the rod lies in an open groove, further expediting the cleaning operation. Preferably, essentially the entire cross section of the rod is received by the groove, with the groove being open toward one side of the grip part. This configuration allows the user to hold and manipulate the grip part without having to take the location of the rod into consideration.
To ensure that the rod does not inadvertently leave its arrested or stopped position, a catch mechanism is provided. Preferably, the catch mechanism includes a release mechanism connected
Buiz Michael
Morrison & Foerster / LLP
Ngo Lien
Waldemar Link (GmbH & Co.)
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