Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-04-21
2001-11-20
Reip, David O. (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S104000
Reexamination Certificate
active
06319254
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the technical field of bone surgery, and in particular to osteosynthesis appliances for bringing fractured bone fragments together, for putting them under compression, and then for uniting them, by means of screws, bolts, nails, metal plates, etc.
The present invention relates to a compression osteosynthesis screw for putting fractured bone fragments under compression, said screw comprising both a screw shank having a thread with a distal zone and a proximal zone, and also a screw head for threading on said screw shank and for co-operating with its proximal zone via internal tapping complementary to the thread of said screw shank, said screw head also having an outside thread at a pitch that is smaller than the pitch of the screw shank.
The present invention also relates to an ancillary device for use with a compression osteosynthesis screw.
BACKGROUND OF THE INVENTION
It is thus already known to unite bone fragments by means of a screw whose shank is pierced over its entire length and which has an outside thread over its entire length. The screw is associated with a separate screw head that has a through internal well so as to be capable of being threaded onto the screw shank. The internal well is provided with tapping complementary to the thread of the screw shank so as to be capable of co-operating therewith and of moving along the entire length of the thread so as to come into abutment in the proximal zone of the screw shank. The screw head also has an outside thread at a smaller pitch than the thread of the screw shank.
In general, such a device gives results that are satisfactory in terms of osteosynthesis treatment since, by screwing the screw shank through the bone fragments, it enables the bone fragments to be brought together, enabling the various bone fragments to be united by jointing at the line of fracture. That device also makes it possible to put the bone fragments under a small amount of compression because of the existence of a pitch differential between the outside screw thread on the screw head and the thread on the screw shank. The existence of a screw pitch differential at the outside thread of the screw head makes it possible, when the head begins to penetrate into a portion of bone, to urge the bone fragments towards one another, which implies putting them into compression. Such compression can also be increased slightly by rotating the head of the screw on its own, thereby making it possible to control or perceptibly increase the amount of compression.
Nevertheless, such a device suffers from drawbacks that put a limit on the amount of compression that can be applied to bone fragments because of the existence of the thread on the screw shank which opposes the application of compression because it is anchored directly in the bone fragments. In addition, the presence of the thread on the screw shank can give rise to bone trauma that is harmful for proper resorption of the fracture.
Other types of dual-pitch compression osteosynthesis screw also exist in the prior art, such screws not having an independent screw head and consequently enabling only a moderate amount of compression to be applied to the bone fragments that are to be united.
OBJECTS AND SUMMARY OF THE INVENTION
Consequently, the present invention provides a remedy to the various drawbacks mentioned above by providing a novel compression osteosynthesis screw that is easier to install and has the ability to apply increased compression to the bone fragments to be united.
Another object of the invention is to provide a novel compression osteosynthesis screw that is simple to manufacture, low in cost, and for which the risks of bone trauma are under control.
Another object of the invention is to provide a novel compression osteosynthesis screw having good mechanical strength while reducing the risks of resorption phenomena appearing.
Another object of the invention is to provide a novel ancillary device for use with a compression osteosynthesis screw which makes it possible during an operation, in reliable manner and in complete safety, to prevent the screw head from losing contact with its thread for engagement on the screw shank.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.
The objects of the invention are achieved by means of an osteosynthesis screw for applying compression to bone fragments, the screw comprising both a screw shank having a thread with a distal zone and a proximal zone, and also a screw head for threading on said screw shank and for co-operating with its proximal zone via internal tapping complementary to the thread of said shank, said screw head also having an outside thread at a pitch that is smaller than the pitch of the screw shank, wherein the distal zone and the proximal zone are separated by a central zone shaped to be inactive during screwing so as to form a sliding zone for the bone fragments to be put into compression.
The objects of the invention are also achieved by means of an ancillary device for use with the osteosynthesis screw of the invention, the device comprising a first screwdriver designed for turning the screw shank and a second screwdriver designed for turning the screw head, the first screwdriver being engaged axially inside the second screwdriver so as to enable the screw shank and the screw head to be turned simultaneously, and being separable therefrom so as to enable the screw head to be turned individually, wherein the second screwdriver is provided at its working end portion with an internal setback designed to receive the collar of the screw shank in an abutment position against the end of the setback, said setback being of a depth such that when the collar comes into abutment against its end while the screw head is being turned, further turning thereof is automatically blocked before the last turn of the proximal thread has been reached so as to prevent the screw head from escaping from said proximal thread.
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Fourcault Eric Stéphane
Giet Jean-Christophe Alain
Knevels Theo Jan Maria
Millen White Zelano & Branigan
Newdeal
Reip David O.
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