Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-01-17
2001-10-23
Philogene, Pedro (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S075000
Reexamination Certificate
active
06306140
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to implants for providing compression between different regions of a material. In particular, the invention relates to a compression bone screw suitable for stabilizing a fractured bone.
BACKGROUND OF THE INVENTION
Treatment of many bone disorders involves stabilizing the bone, such as by providing compression between different regions of bone thereby bringing the regions together to facilitate healing. Typically, bone screws, such as the screw device described in U.S. Pat. No. 6,001,101 to Augagneur and published application No. EP0,856,293 to Diebold et al., have utilized threaded portions having different pitches or leads to establish compression. For example, the compression effect of the Augagneur screw device arises because the travel of the distal portion is higher than the proximal portion, such that the proximal part is driven by the integral distal portion providing compression. Removal of known compression screws, however, tends to generate forces or bias generally opposing the compression achieved during insertion, which can destabilize regions of bone. Another disadvantage of known compression screws is that the threads provide insufficient surface area or purchase at large lead lengths to prevent pullout or damage to the bone.
There is a need, therefore, for an improved bone screw.
SUMMARY OF THE INVENTION
The present invention relates to an implant for insertion in a material. The implant preferably includes a longitudinal axis, a proximal portion, and a distal portion. The proximal and distal portions preferably have proximal and distal threads, respectively. The proximal and distal threads are preferably configured to threadably engage first and second spaced regions of the material, respectively, when the shaft is rotated in one direction about its longitudinal axis to bias the first and second regions of material with respect to one another to provide compression therebetween. When the shaft is rotated in an opposite direction about its longitudinal axis, the proximal thread is preferably configured to substantially inhibit biasing the first region to substantially prevent tension between the first and second regions.
At least a portion of the proximal thread is preferably tapered. For example, the tapered portion of the proximal thread preferably defines an angle of at least about twenty degrees with respect to the longitudinal axis of the shaft. In a preferred embodiment, the tapered portion of the proximal thread disengages the proximal thread from the first region of material in less than about one-half rotation of the longitudinal axis of the shaft in the opposite direction.
In a preferred embodiment, the implant is a compression bone screw and the first and second regions of material are first and second regions of bone, respectively. In the this embodiment, the implant is preferably configured to stabilize the regions of bone by providing compression therebetween and, upon removal of the implant, the implant is configured to inhibit destabilization or distraction of the regions of bone.
In another embodiment, the proximal and distal threads define proximal and distal leads, respectively, the distal lead being larger than the proximal thread. The proximal and distal portions are substantially fixed with respect to one another and preferably spaced apart by a medial portion.
A proximal portion of the implant preferably includes a proximal face defining a depressed region, which includes a drive mechanism therein to receive a drive tool.
Preferably, the distal threads define a proximal face and a distal face to engage the surrounding material. The proximal face and distal faces define first and second angles, respectively, with respect to the longitudinal axis. Preferably, the second angle is smaller than the first angle.
In another embodiment, the present invention relates to an implant including a proximal portion having at least one thread configured to be accommodated within a first region of material and a distal portion having at least three thread starts and configured to be accommodated within the second region of material. Upon insertion of the implant, the proximal and distal threads preferably threadably engage the first and second regions, respectively, providing compression therebetween. Preferably, the distal threads provide sufficient purchase to substantially prevent damaging the second region of material. In a preferred embodiment, the proximal portion includes at least two thread starts, more preferably at least three thread starts. In another preferred embodiment, the distal portion preferably includes at least four thread starts.
REFERENCES:
patent: 2382019 (1945-08-01), Stern
patent: 4175555 (1979-11-01), Herbert
patent: 4463753 (1984-08-01), Gustillo
patent: 4858601 (1989-08-01), Glisson
patent: 5019079 (1991-05-01), Ross
patent: 6001101 (1999-12-01), Augagneur et al.
patent: 603 330 (1934-09-01), None
patent: 0 669 110 A2 (1995-12-01), None
Pennie & Edmonds LLP
Philogene Pedro
Synthes (USA)
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