Surgery – Instruments – Orthopedic instrumentation
Patent
1999-05-05
2000-04-04
Buiz, Michael
Surgery
Instruments
Orthopedic instrumentation
606 79, A61B 1716
Patent
active
06045556&
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a broach for shaping a medullary cavity in a bone and to a method of shaping the cavity.
An artificial joint component can be connected to the resected end of a bone by means of a tapered portion which can be received in the medullary cavity of the bone. In order to obtain a strong connection between the component and the internal surface of the cavity, it is important to ensure that the surfaces of the component and the cavity match so that there is contact between the surfaces over large proportions of their areas, over substantially the entire area of the prosthesis in some cases or over selected portions of its area in other cases. The connection between the bone and the prosthesis can then be created by ingrowth of bone tissue or by means of a bone cement.
Preparation of the bone cavity can be achieved using tools such as reamers and broaches. A reamer is a rotating tool which can be used to create a cavity with a circular cross-section, which will frequently be constant along its length. A broach is generally manipulated in an axial direction. It can be used to create a cavity with a non-circular cross-section. It is suitable for creation of the portion of a medullary cavity that is to receive the tapered portion of a prosthesis, in particular to ensure that the tapered shape of the prosthesis, which can be a complicated irregular shape, is properly matched by the shape of the internal surface of the bone cavity.
A difficulty with use of a broach to shape a bone cavity can lie in ensuring that the broach is properly aligned with the axis of the cavity. Misalignment of the broach can result in the shape of the proximal portion of the cavity matching the shape of the broach but with the axis in the proximal portion being misaligned with the axis in the remainder of the cavity. A result of this can be that the actual degree of matching between the cavity and the prosthesis is reduced in the proximal portion of the cavity, when the prosthesis bercomes aligned with the distal portion.
The present invention provides a broach with a proximal cutting portion having a broadened cross-section and a plug portion, spaced apart from the cutting portion and connected to it by means of a reduced cross-section connecting portion.
Accordingly, in one aspect, the invention provides a broach for shaping a medullary cavity in a bone to receive an orthopaedic prosthesis which is tapered inwardly in a direction from its proximal end towards its distal end, the broach having (a) a proximal portion on which a plurality of cutting teeth are arranged to cut the internal surface of the cavity to receive the broadened proximal portion of the prosthesis, (b) a plug portion at or towards the distal end of the broach, and (c) an elongate connecting portion by which the plug portion is connected to the proximal portion, in which the transverse dimension of the connecting portion being less than that of the plug portion and the proximal portion, and the width of the plug portion being greater at a point between its ends than at any other point along its length, the surface at the point of greatest width being convex when the broach is viewed from the side.
The broach of the invention can be inserted into a bone cavity which has been reamed to a diameter in which the plug portion at the distal end of the broach is a sliding fit with the internal cavity surface. The sliding fit then helps to define the axis of the cavity for the subsequent shaping of the proximal portion of the cavity by means of the cutting teeth on the broach. The broach of the invention therefore facilitates more accurate shaping of a bone cavity, particularly in the proximal region where the cavity has its largest cross-section. This can be especially important when the connection between the prosthesis and natural bone tissue is made only in the proximal region (whether the connection is made by means of bone ingrowth or using bone cement).
The connecting portion of the broach will generally be distinguishable from the proximal portion b
REFERENCES:
patent: 5006121 (1991-04-01), Hafeli
patent: 5089004 (1992-02-01), Averill et al.
patent: 5441501 (1995-08-01), Kenyon
Buiz Michael
Depuy International Ltd.
Shai Daphnn
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