Surgery – Instruments – Orthopedic instrumentation
Patent
1998-01-22
1999-10-19
Tucker, Guy V.
Surgery
Instruments
Orthopedic instrumentation
A61B 1756
Patent
active
059680482
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a reaming tool for boring out bone channels.
Especially before inserting implants in long tubular bones, the bone channels are first bored out so the implant can be inserted or driven into the channel. In most cases, this boring is done with a twist drill head having a relatively short shank that can be connected to a flexible drive shaft and is driven to rotate by a suitable drive mechanism. The flexible drive shaft and the drill head have a continuous bone. It accommodates a guide spike that has previously been tapped into the bone. This provides guidance for the drill head and prevents it from penetrating through the bone wall at the side.
In boring out bone channels, there is the danger of unnecessary injury. Especially when the pressure and temperature in the medullary space rise sharply, there is also the danger of a fat embolism, which must be prevented in any case.
A reaming tool is known from EP-A-0 440 371, the drill head of which comprises a row of twisted teeth which from chip chambers in between. The teeth are rounded concerning their outer contour, by which only the middle area between the ends effects cutting. The drill head is joined with a flexible shank which works as a flexible shank. From the same document reaming tool is known which comprises a row of teeth at the drill head which run off in a first cutting section and form the main cutting edges in this area. The secondary cutting edges are straight and are lying on a cylinder, the axis of which coincides with the axis of the drill head.
A reaming tool of the above mentioned kind is known from the EPA 0 508 710. It comprises four teeth arranged as 90.degree. intervals on the periphery having a starting cut in which the main cutting edges are formed. The secondary cutting edges are lying on a cylinder the axis of which coincides with the bore. The length of the secondary cutting edges is smaller than the diameter of the cylinder. The known drill head is joined with a solid shank and above all serves for boring out small lengths in the bone.
The object of the invention is to create a reaming tool for boring out bone channels such that it will permit a relatively rapid advance, plus good chip flow, and a low pressure at the same time.
This object is achieved according to this invention through the features of claim 1.
The drill head according to this invention has four spiral teeth, each having a small angle of twist, arranged with 90.degree. intervals between them around the circumference. For example, the angle of twist may be in the range of 15.degree.. The starting cut has an angle of approximately 45.degree. (angle of point 90.degree.). It has been found that such a starting cut is especially advantageous.
The secondary cutting edges are located on the outside of the teeth approximately on a cylinder the axis of which coincides with the axis of the bore. The secondary cutting edges thus run approximately on a straight line that is approximately the same distance from the axis along its entire length. Such a design of the teeth permits good guidance in the bone canal independently of the guide spike. This eliminates the danger of the drill head cutting too far into the bone wall on the side.
Another feature of this invention is that the base of the chimp chamber between the teeth or chip groove is very close to the bore. Only enough material is left for the drill head to have sufficient stability. For example, the base of the chip chamber may be located at a radial distance from the axis of the bore which corresponds approximately to the outside radius of the shank of the drill head. However, it is also conceivable for the base to the shank is created so there is no congestion of chips. The relatively larger chip chambers created in this way permit excellent chip removal.
Finally, a ground surface is created according to this invention on the faces adjacent to the chip chambers in the area of the starting cut such that a relatively sharp edge is formed, extending from the ends of the teeth and the chip chambers
REFERENCES:
patent: 3554192 (1971-01-01), Isberner
patent: 5122134 (1992-06-01), Borzone et al.
patent: 5180384 (1993-01-01), Mikhail
patent: 5190548 (1993-03-01), Davis
patent: 5514141 (1996-05-01), Prizzi, Jr.
patent: 5720749 (1998-02-01), Rupp
Howmedica GmbH
Tucker Guy V.
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