Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-02-04
2001-05-22
Smith, Jeffrey A. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
Reexamination Certificate
active
06235031
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an intramedullary fracture fixation device. More specifically, the present invention relates to such a device for fixation of fractures of the proximal femur, including intertrochanteric and subtrochanteric fractures.
2. Description of the Related Art
A variety of fracture fixation devices are known for treatment of femoral fractures. In particular, intramedullary devices are known which provide distinct advantages over known nail-plate combination devices, especially for subtrochanteric and femoral shaft fractures. A good background discussion of such an intramedullary (IM) rod and cross-nail (lag screw) assembly is provided by U.S. Pat. No. 3,433,220 issued to Zickel, which is herein incorporated by reference in its entirety.
Known intramedullary devices have also been designed for treatment of intertrochanteric and femoral neck fractures. For example, U.S. Pat. No. 4,827,917 issued to Brumfield and U.S. Pat. No. 5,032,125 issued to Durham et al., which are herein incorporated by reference in their entirety, each disclose an intramedullary device having an IM rod, a lag screw, a set screw. Additionally, the device of Durham et al. includes a sleeve and a compression screw.
A further excellent description of an intramedullary device similar to that of the present application is set forth in the published United Kingdom Patent Application 2 209 947 A, which again is herein incorporated by reference in its entirety. This reference discloses a basic assembly of an IM rod, a lag screw and a set screw.
The disclosures of all three of the above references are considered to establish the state of the art. Each of the devices disclosed thereby address the desirability of compression in the treatment of femoral fractures and particularly emphasize sliding compression.
Brumfield teaches a lag screw which has a threaded portion and a smooth portion. The threaded portion is at a distal end to be screwed into the femoral head. The smooth portion is provided intermediate the threaded distal end and a head portion. The lag screw is installed into an angled/inclined bore in the IM rod and screwed into the femoral head. The smooth portion of the screw slides within the bore such that the head portion abuts an outer cortex of the bone to provide the desired sliding compression.
Durham et al. teaches a lag screw, sleeve and compression screw combination for achieving sliding compression. The sleeve is designed to fit within the angled bore of the IM rod with a proximal end of the lag screw extending into the sleeve. Both the sleeve and the lag screw are “keyed” to prevent the lag screw from rotating within the sleeve while permitting the lag screw to slide within the sleeve. The proximal end of the lag screw has an internally threaded bore for receiving the compression screw, which is correspondingly threaded. The compression screw is screwed into the proximal end of the lag screw so as to slide the lag screw relative to the sleeve to provide the desired sliding compression.
UK 2 209 947 A teaches the use of a tool which puts a traction force on the lag screw in a direction away from the femoral head. Although not explained in detail, the tool abuts a sleeve which is placed temporarily on the outer cortex of the femoral shaft.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an intramedullary fracture fixation device for fixation of fractures of the proximal femur which overcomes certain disadvantages of the prior art devices while maintaining their advantages. The present invention aims to simplify and improve the manner of achieving desired compression. The invention also aims to provide increased flexibility in surgical applications of the device while reduce manufacturing costs thereof. In order to meet this object, the present invention has been developed with various unique and patentable features as described hereinafter.
According to one embodiment of the present invention, the intramedullary fracture fixation device comprises an intramedullary rod, a lag screw and a lag screw collar. The rod has a proximal end with a transverse bore extending therethrough. The lag screw has a distal end with having course bone engaging thread elements and a proximal end with screw threads. When in use, the lag screw is substantially axially aligned with the transverse bore of the rod. The lag screw collar has an outer diameter sized to rotatably fit within the transverse bore of the rod. The collar also has an inner diameter and internal screw threads adapted to cooperate with the screw threads of the proximal end of the lag screw.
According to a second embodiment, the intramedullary fracture fixation device also comprises an intramedullary rod, a lag screw and a lag screw collar. The rod has a proximal end with a transverse bore extending therethrough. The lag screw has a distal end with having coarse bone-engaging thread elements and a proximal end with screw threads. When in use, the lag screw is substantially axially aligned with the transverse bore of the rod. The lag screw collar has an outer diameter over at least a portion thereof which is sized to rotatably fit within the transverse bore of the rod and an increased outer diameter at one end thereof which is at least slightly larger than a diameter of the transverse bore of the rod. The collar also has an inner diameter and internal screw threads adapted to cooperate with the screw threads of the proximal end of the lag screw.
According to a variant of the above embodiments, the outer diameter of the collar is preferably sized to substantially abut an inner wall of the transverse bore of the rod such that the collar acts as a centering device for the lag screw relative to the transverse bore.
Further, the collar preferably includes at least one flattened outer engagement surface or at least one engagement groove formed on an outer surface thereof.
Still further, the above embodiments may further comprise a longitudinal bore which extends through the proximal end of the rod so as to open into the transverse bore. The longitudinal bore is preferably angularly offset with respect to a longitudinal axis of the proximal end of the rod.
According to a third embodiment, the intramedullary fracture fixation device comprises an intramedullary rod with both transverse and longitudinal bores. The transverse bore extends through a proximal end of the rod. The longitudinal bore extends through the proximal end of the rod so as to open into the transverse bore. The longitudinal bore is angularly offset with respect to a longitudinal axis of the proximal end of the rod.
According to a variant of the third embodiment, the device further comprises a collar and a set screw. The collar preferably has an outer diameter sized to fit within the transverse bore of the rod. The set screw is preferably adapted to be secured within the longitudinal bore of the rod with a distal end thereof extending at least partially into the transverse bore of the rod so as to engage the collar when the collar is disposed within the transverse bore.
Further, the collar preferably includes at least one flattened outer engagement surface or at least one engagement groove formed on an outer surface thereof. In such case, the set screw is adapted to engage the engagement surface or groove so as to prevent rotation of the collar within the transverse bore of the rod.
REFERENCES:
patent: 3433220 (1969-03-01), Zickel
patent: 4432358 (1984-02-01), Fixel
patent: 4438762 (1984-03-01), Kyle
patent: 4621629 (1986-11-01), Koeneman
patent: 4622959 (1986-11-01), Marcus
patent: 4657001 (1987-04-01), Fixel
patent: 4667664 (1987-05-01), Taylor et al.
patent: 4697585 (1987-10-01), Williams
patent: 4733654 (1988-03-01), Marino
patent: 4733664 (1988-03-01), Kirsch et al.
patent: 4776330 (1988-10-01), Chapman et al.
patent: 4805607 (1989-02-01), Engelhardt et al.
patent: 4827917 (1989-05-01), Brumfield
patent: 5032125 (1991-07-01), Durham et al.
patent: 5176681 (1993-01-01), Lawes et al.
pa
Hodgeman John D.
Roy Stephen C.
Bacon & Thomas PLLC
Encore Medical Corporation
Smith Jeffrey A.
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