Device for removing cancellous bone

A device (10) for removing cancellous bone during machining of a long bone canal includes a brush mechanism for scraping cancellous bone from cortical bone while deflecting off the cortical bone and a center post (14) operatively connected to the brush mechanism (12) for centering the brush mechanism (12) relative to the long bone canal. An adapter mechanism (16) is connected to the center post (14) for connecting the center post (14) to a motion actuator to move the brush mechanism (12) relative to the long bone canal and scrape off cancellous bone therefrom.

TECHNICAL FIELD 
The present invention relates to a device used during the preparation of a 
long bone, such as a femur, for the implantation of a prosthesis device. 
More specifically, the present invention provides a device for removing 
cancellous bone during the machining of a long bone canal, such as the 
femoral canal. 
BACKGROUND OF THE INVENTION 
During the preparation of the femur during standard cemented hip 
arthroplasty, the femoral canal is machined or broached to provide an 
oversized hole for the implant to rest in. This process is accomplished by 
hand-operated machining or broaching tools. After a bone plug is inserted 
and the canal cleaned by irrigation, cement is introduced into the canal 
and the hip stem is pushed into the cement and held in place until the 
cement mantel hardens. In order to achieve success during the process, the 
cement must reach and interdigitate with the hard cortical bone to 
guarantee good cement-bone interface strength. A difficulty arises when 
the cancellous bone is not sufficiently removed from the canal. Since the 
cancellous bone is weak, the cancellous bone provides an obstacle in 
achieving the interface strength. That is, although the cement may 
penetrate the cancellous bone, the cancellous bone does not provide a 
strong substrate for attachment to the prosthesis, thereby resulting in 
failure of the interface between the cement and bone. 
Although the machining or broaching is done to remove cancellous bone and 
to prepare the cortical bone for hip stem implantation, the variations in 
bone shapes and sizes often require that the surgeon either leave the 
cancellous bone in place or remove it by curette and other hand 
techniques. These hand operated techniques are inaccurate, time consuming 
and rarely remove all of the cancellous bone. Therefore, it is desirable 
to have an instrument that will automatically remove the cancellous bone 
accurately and completely. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a device for 
removing cancellous bone during machining of a long bone canal, the device 
including brush means for scraping cancellous bone from the cortical bone 
while deflecting off of the cortical bone and guide means operatively 
connected to the brush means for centering the brush means relative to the 
long bone canal. Adapter means are connected to the guide means for 
connecting the guide means to a motion actuator to move the brush means 
relative to the lone bone canal and scrape cancellous bone therefrom.

DETAILED DESCRIPTION 
A device for removing cancellous bone during machining of a long bone canal 
is generally shown at 10 in the Figures. Like numerals preceded by the 
numerical suffix "1", "2" or "3" are used to show like structure between 
the several embodiments. 
Generally, the device 10 includes a brush mechanism, generally shown at 12, 
for scraping cancellous bone from cortical bone while deflecting off of 
cortical bone. The brush mechanism 12 is operatively mounted upon a center 
post generally shown at 14. The center post provides a guiding mechanism 
for centering the brush mechanism 12 relative to the lone bone canal. An 
adapter mechanism, such as a Hutson reamer end 16, is connected to the 
center post 14 for connecting the center post 14 to a motion actuator to 
move the brush mechanism 12 relative to the long bone canal and scrape off 
cancellous bone therefrom. The Hutson reamer end 16 is an adapter well 
known in the art for connection to a reamer device for rotational movement 
of the center post 14. However, other adapters well known in the art, such 
as a bayonet, screw or other readily interchangeable adapter may be used 
with equal success. Such actuation can be for rotational movement of the 
center post 14 about its longitudinal axis (the axis defined by the length 
of the tool) indicated by broken line 18 in FIG. 1. The actuation can also 
be an axial reciprocating action along axis 18 as well. 
In each embodiment of the invention, the center post 14 has a first and 
second end 20, 22, respectively. The adapter 16 is operatively connected 
to the first end 20, by means well known in the art. For example, the 
adapter 16 can be integrally mounted on the first end 20, the adapter 16 
being an integral portion of the center post 14, or the adapter 16 can be 
removably mounted on the center post 20 for replacement to adapt the 
device to various types of reaming or piston actuated machining devices. 
The second end 22 of the center post 14 is rod-shaped and has a rounded end 
surface for seating in the long bone canal. Thusly, the second end 22 of 
the device provides orientation of the center post 14 and thereby the 
brush mechanism 12 relative to the long bone canal during the operation of 
the device 10. 
As shown in the several embodiments of FIGS. 1-3, the second end 22 of the 
center post 14 can include either an integral end portion, as shown in 
FIG. 1, or a sleeve 24 mounted on a sleeve mounting mechanism 26 defining 
an end of the center post 14. The sleeve member 24 can be constructed in 
various cross-sectional diameters allowing for sizing of the second end 22 
of the center post 14 to various sized long bone canals. 
For example, as shown in FIG. 2, the second end 122 of the center post 114 
can include a sleeve member 24 having a threaded female portion 28 for 
engagement with the threaded male portion 26. Alternatively, the sleeve 24 
could include a threaded male projection for engagement with a threaded 
female portion in the center post 114. 
An alternative mounting mechanism is shown in FIG. 3. In this embodiment, 
the center post 114 includes a bayonet projection 126 which is seated in a 
recess 128. This embodiment allows for sliding movement of the bayonet 
projection 126 into and out of the recess 128 thereby allowing axial 
movement of the brush mechanism 112 relative to the long bone canal. 
Additionally, the cross-section of the recess 128 and projection 126 can 
be annular allowing for relative rotational movement between the bayonet 
projection 126 and recess 128. Alternatively, the bayonet projection can 
have a cross-sectional form which engages the recess 128 thereby requiring 
rotational movement of the sleeve 124 during actuated rotation of the 
center post 114. 
The center post 14 can optionally include a stop mechanism extending 
radially therefrom for limiting the extent to which the center post 14 can 
enter the long bone canal. The stop mechanism can be in the form of an 
annular flange 30, 130, 230 shown in FIGS. 1, 3 and 6. The stop mechanism 
is operative by engaging the distal surface of the bone adjacent the canal 
thereof thereby limiting further insertion of the end portion 22 into the 
long bone canal. The annular flange 30 is disposed between the end portion 
22 of the center post 14 and the brush mechanism 12. 
The brush mechanism 12 can include a plurality of bristles 32 extending 
radially outwardly from the center post 14, as shown in cross-section in 
FIG. 4, and being disposed between the first and second ends 20, 22 of the 
center post 14, as shown in the Figures. More specifically, the bristles 
32 can be connected directly to the center post 14 by means well known in 
the art, as shown in FIG. 4. For example, the wire bristles 32 can be 
attached by soldering or welding, or by crimping between two surfaces. 
Alternatively, if thicker and stiffer bristle 32 wires are desired, such 
bristles 32 may be pinned to the center post 14 to permit independent 
pivotal movement of each bristle 32 relative to the center post 14, not 
unlike the manner in which keys are retained on a standard key ring. 
As shown in FIG. 4, the bristles 32 are mounted in an annular formation 
extending radially outwardly from the center post 14 thereby defining a 
wheel-type structure. The bristles can be made from wire, fibers, or other 
materials which can be constructed so as to be stiff enough to remove the 
cancellous bone yet deflect off of the cortical bone. 
An alternative method of mounting the bristles 32 on the center post 14 is 
shown in FIG. 5. In this embodiment, the bristles 32 are mounted on an 
adapter wheel 34. The adapter wheel 34 includes an annular outer surface 
36 upon which the bristles 32 are mounted by means well known in the art. 
The adapter wheel 34 includes a center slot opening 38 extending 
therethrough. The center post 14 includes a seating surface shown as a 
square-shaped surface 40, in cross-section, for seating the adapted member 
thereon whereby the flat surfaces of the opening 38 engage the flat 
surfaces of the seating surface 40 of the center post 14. The seating 
surface 40 of the center post 14 can be formed so as to substantially fill 
the opening 38 during mating thereof thereby allowing for no relative 
movement therebetween. Alternatively, as shown in FIG. 5, the seating 
surface 40 can allow for lateral i.e., side-to-side, movement of the 
adapter wheel 34 relative thereto thereby allowing for slight play between 
the adapter wheel 34 and center post 14. This allows the adapter wheel 34 
movement to remove cancellous bone in a non-circular region of the canal. 
As the adapter wheel 34 turns at relatively low speeds, reaction forces 
applied to the adapter wheel 34 from cortical bone contact will force the 
adapter wheel 34 away, thus creating an ellipsoid for better cancellous 
bone removal. 
The outer surface of the bristle 32 can be formed in various shapes which 
can be utilized for various canal configurations. More specifically, the 
bristles 32 are mounted along the length of the center post 14 as defined 
by the center axis 18 shown in FIG. 1. Preferably, as discussed above, the 
bristles 32 have ends radially distal from the center post 14. As shown in 
FIG. 1, these end portions can form a wheel-shape member 12 having a flat 
distal surface. As shown in FIG. 2, the assembly can include several 
wheel-shape members 112 each having a decreasing outer diameter in a 
step-wise manner. A further alternative embodiment, not shown in the 
Figures, would be a brush mechanism having a substantially frusto-conical 
shape, which is not step-wise as shown in FIG. 2. The configuration shown 
in FIG. 2 where the brushes 112 have step-wise decreasing outer surfaces, 
can be either formed by the bristles 132 being directly connected to the 
center post 114, as discussed above, or they can be separately mounted as 
individual wheels, also as discussed above with relation to the adapter 
wheel 34. By utilizing the adapter wheel 34, a single center post 14 can 
be used to either support a single wheel, as shown in FIG. 1, or multiple 
wheels as shown in FIG. 2, depending upon the situation encountered by the 
practitioner vis-a-vis the shape of the femoral canal being operated upon. 
An alternative construction of the center post 214 of the present invention 
is shown in FIG. 6. The center post 214 includes a female portion 42 
defining a guide track extending along a length of the center post 214 and 
a male portion 44 for seating in the female portion 42 while allowing for 
reciprocating axial motion relative therebetween. The reciprocating or 
piston-like motion provides axial reciprocating motion between the 
bristles 232 and the long bone canal. Thusly, similar to the embodiment 
shown in FIG. 3, the device 210 can provide combined rotational movement 
of the bristles 232 in addition to axial movement relative to the long 
axis 218 of the center post 214. 
The device 210 shown in FIG. 6 can include a solid male portion 44 
including a first end portion 45 for seating in the female portion 42 and 
a second end portion 222 as discussed above which is integral with the 
male portion 44. Alternatively, as shown in FIG. 6, the male portion 44 
can include a second end 46 including threads thereon for connecting to a 
sleeve member 48. The sleeve member 48 includes a threaded female portion 
50 for mounting on the threaded end portion 46, the sleeve member 48 
providing a pilot stem proceeding within a long bone canal, as discussed 
above. The sleeve member 48 allows for sizing of the second end portion 
122 of the male portion 44 to various sized long bone canals. That is, as 
discussed above, different sleeve members 48 having different 
cross-sectional diameters can be connected to a single male portion 44 
thereby providing for adaptation of a single device to various sized and 
shaped long bone canals. 
A further embodiment of the present invention is shown at 310 in FIG. 7. In 
this embodiment, the center post 314 includes a pivot mechanism 52 between 
the bristles 32 and the second end 322 of the center post 314 for allowing 
pivotal movement of the bristles 332 relative to the second end portion 
322 and thereby relative to the long bone canal into which the second end 
322 is seated. The pivot mechanism 52 can be in the form of a universal 
joint, ball joint, or the like, such joints being well known in the art. 
The pivot mechanism 52 allows a practitioner to move the bristles 32 in 
any direction desired relative to the femoral canal. Again, such a pivot 
mechanism 52 can be connected to a solid center post 14 by a sleeve member 
48 including the pivot mechanism 52, as discussed above. 
In operation, generally, an end portion 22 would be seated in the femoral 
canal. The center post 14, connected to a reamer device or the like by the 
adapter member 16, would be actuated to either rotate the center post 14 
and attached bristles 32, to make the center post 14 move in piston-like 
manner, utilizing the device 210 shown in FIG. 6 or the bayonet sleeve 
connection shown in FIG. 3, or causing both a piston-like and rotational 
movement of the bristles 32. The operation would continue until the 
bristles 32 removed substantially all of the cancellous bone from the long 
bone canal. During the procedure, various end sleeve members, such as 
those shown in FIGS. 2 and 3 as well as a pivoting member 52, such as 
shown in FIG. 7, can be utilized. Thusly, the present invention provides 
an automatic device utilizing flexible wires or fibers attached to a 
center core, having varying dimensions depending on size requirements to 
remove cancellous bone during a standard cemented hip arthroplasty 
procedure. 
The invention has been described in an illustrative manner, and it is to be 
understood that the terminology which has been used is intended to be in 
the nature of words of description rather than of limitation. 
Obviously many modifications and variations of the present invention are 
possible in light of the above teachings. It is, therefore, to be 
understood that within the scope of the appended claims wherein reference 
numerals are merely for convenience and are not to be in any way limiting, 
the invention may be practiced otherwise than as specifically described.