Joints and connections – Articulated members – Including limit means
Reexamination Certificate
1999-01-04
2001-05-29
Browne, Lynne H. (Department: 3629)
Joints and connections
Articulated members
Including limit means
C403S122000, C606S065000, C606S066000, C606S067000, C606S068000
Reexamination Certificate
active
06238126
ABSTRACT:
This invention relates to two-dimensional joints and their use in compression screw assemblies, particularly for use in surgical operations and in the treatment of proximal femur fracture.
In the treatment of proximal femur fracture the typical orthopaedic surgical process is to secure the fractured bone using a compression screw consisting of a lag screw and an angle plate secured thereto at a fixed angle. Such screws are available with different angles between the lag screw and plate, typically increasing at 5° intervals from 120° to 150°. The angle plates are coupled to the lag screw by a system which allows axial movement of the plate relative to the screw. Because the location of the lag screw in the treatment of a fracture of this kind is critical, the limitation on the angular relationship between the lag screw and the angle plate means that it is difficult in almost every case to fit the compression screw at the ideal position.
The present invention addresses the above problem, and provides an adjustable two-dimensional joint for use in compression screw assemblies, and which allows for relative alignment of the angle plate of such an assembly with the lag screw, even when these components are effectively fitted to the respective bone sections. A joint according to the invention, adjustable in two dimensions, comprises first and second elements formed with complementary male and female cylindrical surfaces defining the plane of adjustment, the first element defining a hinge point at the axis of the male cylindrical surface, and the second element including a fulcrum extending to the axis of the female cylindrical surface. A setting device extends between pivot points on the first and second elements which is adjustable in length between the pivot points to alter the angle between the elements. In a hip compression screw assembly, the first element will constitute or be effectively part of the angle plate and the second element constitute or be part of the lag screw.
The setting device can be located within the overall construction of a joint according to the invention, and extend along a path traversing the complementary cylindrical surfaces on the respective elements. Such a device is received in slots extending across the cylindrical surfaces in the plane of adjustment of a joint, but even with this discontinuance, there is still ample cylindrical surface on each element to allow for smooth and accurate adjustment. The preferred setting device comprises a locking screw extending from the pivot point in one of the elements, and received in a threaded sleeve extending from a pivot point on the other of the elements. One of the screw or sleeve is rotatably mounted at its respective pivot points to enable its rotation relative to the other to adjust its overall length. In this orientation, the setting device must be extended to reduce the obtuse angle between the elements, and shortened to increase the angle. As noted above, a typical range of angles in a hip compression screw assembly is 120° to 150°, and a joint of the present invention can be made infinitely adjustable within a chosen range. However, to provide for maximum flexibility in adjustment, the respective pivot points must be fixed relative to their respective elements, and for this purpose, spherical joints are typically used. Movement is normally restricted to two dimensions at one end, but rotational movement allowed at the other to enable the spacing therebetween to be varied.
A joint according to the invention is typically formed with the second element comprising a block defining the female cylindrical surface, and a sleeve surrounding the block and defining the fulcrum. This construction is particularly suited to use of the joint in a hip compression screw assembly, as the sleeve can be located in the caput, and the block fitted to the sleeve thereafter, and after coupling thereto of the setting device component or components. Provision is made for securing the block in the sleeve to ensure that the fulcrum is properly located at the axis of the cylindrical surface, and suitable locating and securing mechanisms are provided for this purpose.
REFERENCES:
patent: 1789060 (1931-01-01), Weisenbach
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patent: 3437059 (1969-04-01), Stonier et al.
patent: 3550668 (1970-12-01), Coyle
patent: 4652166 (1987-03-01), Gautron
patent: 5167664 (1992-12-01), Hodorek
patent: 5514138 (1996-05-01), McCarthy
patent: 5642956 (1997-07-01), Hale
patent: 5807010 (1998-09-01), Parker et al.
patent: WO 93/22982 (1993-11-01), None
patent: WO 95/11632 (1995-05-01), None
patent: WO 95/33931 (1995-12-01), None
Browne Lynne H.
Cottingham John R.
Wallenstein & Wagner Ltd.
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