Medullary canal plug

A medullary canal plug for use for example, when inserting the stem of a bone joint replacement into a bone canal. The plug comprising a substantially hemispherical center and a plurality of individual leaves radiating from the flat face of the center with the adjacent edges of the leaves angularly inclined relative to the faces to facilitate the partial overlapping of the leaves, when moved from a planar disposition to a frusto conical position during insertion into the bone canal.

This invention concerns a plug for use when inserting the stem of a bone 
joint replacement, for example, a femoral endoprosthesis into a bone 
canal. 
It is known to provide a plug in the medullary canal. In the past such a 
plug has been formed of polyethylene and has been of rigid construction, 
comprising a base and a cylindrical sidewall extending therefrom. The 
sidewall has, in one form of plug, been provided with annular ribs 
extending angularly downwardly from the sidewall, that is to say, towards 
the base of the plug. Such a plug is used, when inserted into the 
medullary canal, to confine the bone cement to the region of the canal in 
which the stem of the joint replacement is located thus to ensure 
efficient fixation of the joint replacement. The plug also serves, by 
blocking the canal to prevent blood and tissue debris moving down the 
canal when bone cleaning is carried out prior to insertion of the stem of 
the joint replacement. 
One of the disadvantages of such plugs lies in the fact that, being 
substantially rigid they can, from time to time, become jammed in the 
canal before they are located in the correct position to enable the stem 
of the joint replacement to be fully inserted. In such cases withdrawal of 
the plug is often difficult and in some cases impossible and in the latter 
case the plug must be broken in order to enable it to be moved to allow 
the correct insertion of a new plug. 
Another disadvantage of the known plug is that, again due to its rigidity 
it is essential that a range of sizes of plugs must be made. 
It is therefore an object of the present invention to provide a plug which 
does not suffer from the above outlined disadvantages. 
Thus according to the present invention a medullary canal plug is 
characterized in that it comprises a relatively rigid center and a 
plurality of individual leaves radiating therefrom, the said leaves being 
so connected to the center that they can pivot from a substantially flat 
disc configuration to a condition in which they take up a frusto conical 
configuration in which the individual leaves lie in partially overlapping 
condition.

As can be seen the plug comprises a center 10 which is conveniently 
hemi-spherical in form. 
From the planar face of the center 10 radiate a plurality of leaves 11 
which, when the plug is not in use, lie in a common plane. It will be 
noted that the longitudinal edges 12 of the leaves 11 are inclined (see 
FIG. 2 in particular) relative to the faces of the leaves and that in the 
region of the periphery 13 of the leaves the longitudinal edges 12 are 
angularly contoured (as shown at 14) relative to the edges 12 so that, as 
will be explained below, the leaves 11 can be caused to overlap. 
When the plug is being used it is placed over the end of the medullary 
canal 15 of a bone 16 and is pushed down the canal 15 by applying pressure 
to the center 10. Pressure on the center 10 by an inserting tool (not 
shown) causes the leaves 11 to pivot about a joint line 17 with the center 
10 and take up a frusto conical configuration in which the leaves 11 
overlap as shown in FIG. 3. Overlapping of the leaves 11 is assisted and 
ensured by virtue of the angular disposition, relative to the faces, of 
the longitudinal edges 12 of the leaves 11 and also by the contouring of 
the peripheral region 14 of the ends of the leaves. Since the plug leaves 
11 are capable of independent movement relative to each other irregularity 
or change in the size of the medullary canal 15 can be compensated for by 
such relative movement of the leaves 11 and thus the plug can be moved to 
its requisite position in the canal 15 relatively easily. 
It is envisaged that the plug will be moulded from rigid polyethylene and 
that for all uses a single size of plug can be produced, and that an X-Ray 
telltale will be incorporated into the plug.