Threaded pin

Details Threaded pin Threaded pin

2000-02-02

2001-07-17

Philogene, Pedro (Department: 3732)

Surgery

Instruments

Orthopedic instrumentation

C606S075000, C411S307000, C411S415000

Reexamination Certificate

active

06261292

ABSTRACT:

SUMMARY OF TIE INVENTION
The present invention relates to a threaded pin for holding together pieces of a bone that have been separated by a fracture, and more particularly the invention relates to a pin enabling compression to be applied to two bone fragments regardless of the level at which cutting takes place in a case of osteotomy.
In order to heal a bone fracture, it is desirable to compress the fracture in such a manner as to press together the surfaces of the fracture.
A screw with a threaded head is already known for the osteosynthesis of bone fragments. For example, French patent application FR-A-2 760 628 describes a threaded-head screw for the osteosynthesis of bone fragments, where the screw comprises a distal portion provided with a cylindrical thread and a proximal portion or head provided with a conical thread of diameter that increases towards the proximal end of said screw. The pitch P of the conical thread of the proximal portion is smaller than the pitch P′ of the cylindrical thread on the distal portion. The distal portion and the proximal portion are spaced apart by a smooth portion. The pitches P and P′ are constant.
U.S. Pat. No. 5,562,672 describes a screw for holding together pieces of a bone that have been separated by a fracture, the screw comprising a distal or control portion and a proximal or rear portion. The screw has a thread which extends from the distal end to the proximal end, a crest being formed on said thread. The radius of the crest is greater close to the proximal end and smaller close to the distal end. The pitch measured between corresponding points on consecutive thread crests decreases continuously from a greater value close to the distal end towards a smaller value close to the proximal end.
Prior art pins (smooth, unthreaded and cylindrical) suffer from several drawbacks. They do not ensure that there is no skidding on the piece of bone while the pin is being inserted. Nor do they make it possible to compress the two pieces of bone sufficiently on either side of the fracture. Finally, they do not make it possible to avoid the pin breaking under normal conditions of use.
An object of the invention is thus to mitigate the drawbacks of prior art pins.
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.
To this end, the invention provides a pin comprising a body with a distal end and a proximal end, wherein the distal end has a first thread presenting crests, the proximal end has a second thread presenting crests, the first thread and the second thread being spaced apart by a smooth portion, and the first and second threads being such that the pitch X of the first thread and the pitch Y of the second thread both decrease from the distal end (X
1
, X
2
; Y
1
, Y
2
) towards the proximal end (X
n
, X
n−1
; Y
n
, Y
n−1
), and wherein the diameter d of the crests of the first thread and the diameter D of the crest of the second thread both increase from the distal end (d
1
, d
2
; D
1
, D
2
) towards the proximal end (d
n
, d
n−1
; D
n
, D
n−1
), with the values being such that X
1
>X
2
>X
n−1
>X
n
>Y
1
>Y
2
>Y
n−1
>Y
n
and D
n
>D
n−1
>D
2
>D
1
>d
n
>d
n−1
>d
2
>d
1
.
In addition, the pin of the invention is such that preferably:
the distal portion has a sharp tip at its end;
the diameter di has a value lying in the range 1 mm to 20 mm, i.e., 1 mm≦d
1
≦20 mm;
the length from the distal end to the proximal end lies in the range 5 mm to 50 mm;
the proximal portion is terminated by a cylindrical body; or
the proximal portion is terminated by a cylindrical body having a significant decrease in diameter.


REFERENCES:
patent: 3466748 (1969-09-01), Christensen
patent: 4175555 (1979-11-01), Herbert
patent: 4463753 (1984-08-01), Gustilo
patent: 4978350 (1990-12-01), Wagenknecht
patent: 5019079 (1991-05-01), Ross
patent: 5562672 (1996-10-01), Huebner et al.
patent: 6001101 (1999-12-01), Augagneur et al.
patent: 2760628 (1998-09-01), None
patent: WO95/15727 (1995-06-01), None
patent: WO 97/10767 (1997-03-01), None
D.M. Belloli et al., Abstract presented at the 9th Annual Conference of the Engineering in Medicine and Biology Society/IEEE Meeting, Nov. 13-16, 1987, entitled “a Biomechanical Comparison Between Herbert and 4.0 Cancellous Screws.”

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