Bone cement preparation kit having a breakable mixing shaft forming an output port

A disposable telescoping mixing cartridge for mixing and delivering a quantity of bone cement. The cartridge cap includes a break-away agitator which opens an outlet port for the flow of cement. Therefore, the single opening serves as both an outlet port for the cement and the opening through which the agitator is reciprocated.

This invention relates to a disposable preassembled collection of 
preparation apparatus and various cement components used in the 
preparation of bone cement. The collection of disposable apparatus and 
constituent components being packaged as a single sterile kit for 
convenience and includes a telescoping mixing cartridge with a vacuum 
release mechanism and a break-away agitator. The break-away agitator forms 
an output for the ejection of the bone cement. 
BACKGROUND OF THE INVENTION 
In many orthopaedic surgical procedures, bone cements are used to fix 
implants to the bone. Conventional bone cements are generally polymeric 
materials, which are prepared by copolymerization of its components as 
needed. Bone cement is prepared by copolymerizing a liquid monomer and a 
powdered copolymer, such as methyl methacrylate and polymethyl 
methacrylate or methyl methacrylate-styrene. During mixing of the 
constituent components of the cement, air bubbles may be formed within the 
cement. It is thought that to improve the resultant strength of the 
cement, the air bubbles must be evacuated from the mixture to ensure a 
uniform reaction product. Consequently, the mixing of the constituent 
components is ideally performed in a vacuum. 
The separate constituent components may be mixed within a mixing cartridge 
as is well known in the art. The mixing cartridge, when fully extended, 
provides a larger volume for mixing the constituent components to ensure 
that the constituent components are adequately mixed. Such mixing 
cartridges are generally enclosed by removable caps, which include a 
valved port for connection to a vacuum pump. Vacuum pumps draw a vacuum 
within the cartridges during the mixing process to reduce the occurrences 
of air bubbles within the cement. The caps have an off-set outlet port 
through which the mixed cement compound is expelled and a central opening 
through which an agitator is reciprocally disposed. The agitator has an 
elongated shaft and a mixing paddle for mixing the constituent components. 
The agitator shaft is broken off after mixing and the offset outlet port 
is opened to expel the cement. In a prior art vacuum cartridge mixing 
device, an end plunger is released after mixing yet while the cartridge is 
still under a vacuum. The vacuum pressure within the cartridge causes the 
plunger to be drawn into the cartridge to collect the cement. The plunger 
stops moving within the cartridge when the force exerted by the vacuum 
equalizes. After the cement is throughly mixed, the agitator shaft is 
broken off and the cartridge is inserted into a conventional cement 
applicator gun. Cement applicator guns are well known in the art. 
Generally, a variety of cement nozzles are affixed to the outlet port to 
aid in the application of the cement within the bone cavity. Because the 
outlet port is off center, a certain amount of cement cannot be expelled 
from the cartridge, and is discarded with the disposal of the cartridge. 
Heretofore, the various cement constituent components and mixing apparatus 
have been individually packaged and provided to the user. Since the cement 
sets rapidly, the preparation and application of bone cement is time 
critical. Preparation of bone cement is generally performed in the sterile 
field of the operating room. Consequently, each piece of apparatus must be 
provided in a sterile package. Providing all of the various mixing 
apparatus and cement constituent components as a single preassembled 
collection or kit would be more convenient for the users in the operating 
room. 
SUMMARY OF THE INVENTION 
This invention provides a preassembled collection of disposable mixing 
apparatus and various cement constituent components needed for the 
preparation of bone cement in a convenient disposable kit. The kit 
includes a contoured storage tray, ampules of liquid cement monomer, 
packets of powder cement copolymer, a vacuum pump, connecting tubing with 
a vacuum indicator, a mixing cartridge, a cartridge cap and agitator, an 
assortment of connectable cement nozzles, and a funnel attachment. The kit 
can be packaged as a single unit for convenient and efficient use in the 
sterile environment of an operating room. In addition the contoured tray 
holds the various items in convenient positions to assist the user during 
the preparation of the bone cement. For example, the tray holds the mixing 
cartridge in a stable upright position so that the user does not have to 
hold the cartridge, leaving his hands free to operate the agitator or the 
vacuum pump. 
The disposable telescoping mixing cartridge of the kit employs a vacuum 
release mechanism which releases the vacuum within the cement cartridge as 
the telescoping tubes are being compressed. The cartridge includes two 
telescoping tubular cylinders. The inner cylinder is shiftably received 
within the outer cylinder. The inner cylinder has an L-shaped longitudinal 
channel, and the outer cylinder includes a protrusion or key which is 
seated within the channel to provide for the lock and release of the inner 
cartridge relative to the outer cartridge. Alternatively, the channel may 
be stepped thereby allowing the inner cylinder to be rotated and axially 
moved within the outer cylinder between three selective positions: a fully 
extended mixing position, an intermediate vacuum release position, and a 
retracted applicator position. 
The cartridge cap includes a break-away agitator which also serves as an 
outlet port after breaking. Therefore, the cap has a single opening to 
serve as both an outlet port for the cement and the opening through which 
the agitator is reciprocated. The agitator includes a handle and an 
elongated shaft reciprocally disposed within the outlet port of the cap. 
The shaft includes a tubular outer sleeve and an inner rod axially 
disposed within the sleeve. The sleeve has a frangible hollow distal end. 
Agitator paddles extend radially from the distal end of the sleeve for 
assisting in the mixing of the constituent components of the bone cement. 
The distal end of the rod terminates in an integral dumbbell shaped end 
plug. The small diameter of the middle segment of the dumbbell shaped end 
plug is positioned approximate to an annular notch formed in the sleeve. 
The distal end of the sleeve can be detached from the shaft so that the 
mixed cement compound can be expelled therethrough. The configuration of 
the dumbbell shaped end plug allows the rod to be bent at the middle 
section of the end plug while the sleeve is fractured at the notch. The 
hollow distal end of the sleeve remains seated within the outlet port of 
the cap to provide a passage for the mixed cement compound to be expelled. 
Accordingly, an advantage of this invention is to provide a collection of 
disposable mixing apparatus and cement constituent components for vacuum 
mixing and cartridge delivery in a single sterile kit for convenient use. 
Another advantage of this invention is that the tray included in the kit 
holds the mixing cartridge while the constituent components are mixed so 
that the cartridge does not have to be manually supported during the 
preparation of the cement compound. 
Another advantage of this invention is that the telescoping mixing 
cartridge has a vacuum release mechanism which releases the vacuum during 
collapsing of the telescoping cartridge. 
Another advantage of this invention is that the cap includes a single 
outlet port through which the agitator is reciprocated during the mixing 
process and cement is expelled during cement application. 
Other advantages will become apparent upon a reading of the following 
description.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The preferred embodiments herein described are not intended to be 
exhaustive or to limit the invention to the precise forms disclosed. 
Rather, they are chosen and described to best explain the invention so 
that others skilled in the art might utilize their teachings. 
FIG. 1 shows the collection of disposable items of kit 2 of this invention 
for use in the preparation of bone cement. Kit 2 consists of the following 
items: a contoured storage tray 10, ampules 12 of liquid cement monomer, 
packets 14 of powdered cement polymer, vacuum pump 20, connecting tubing 
26 having a vacuum indicator 28, a mixing cartridge 30, a cartridge cap 60 
and break-away agitator 70, an assortment of connectable cement nozzles 
80, and a funnel attachment 90. Preferably, tray 10 is constructed from a 
molded plastic, which has a plurality of contoured recesses 11 (FIGS. 1, 8 
and 9) within which the various mixing apparatus and constituent 
components 4 of the cements are stored. As shown in FIG. 1, tray 10 allows 
all of the kit items to be stored and packaged in a single sterile 
covering (not shown). Each of the kit items are held in their individual 
contoured recesses 11 formed in tray 10. In addition, tray 10 holds the 
various items at a convenient position to assist the user in preparing the 
bone cement. For example, tray 10 holds mixing cartridge 30 in a stable 
upright position so that the user does not have to hold the cartridge, 
leaving his hands free to pour in the constituent components, operate 
vacuum pump 20, or agitator 70. 
Preferably, the constituent components 4 of the cements are individually 
packaged in premetered portions. The liquid monomer components are 
provided in ampules 12 and the powder copolymers are provided in sealed 
packets 14, although any suitable packaging for the components may be 
provided with the kit of this invention. Ampules 12 of the liquid monomer 
and packets 14 of powder copolymer are well known in the art and are 
commercially available from a variety of sources. Vacuum pump 20 uses a 
reciprocated piston design, although any suitable vacuum pump may be 
included as part of kit 2. Vacuum pump 20 includes a cylindrical body 22 
and reciprocating shaft 24, which drives an internal piston (not shown). 
Vacuum pump 20 also includes a check valve (not shown) to permit air flow 
in one direction only through the pump orifice. The length of tubing 26 is 
used to connect pump 20 to cap 60 when connected to mixing cartridge 30. 
Preferably tubing 26 includes vacuum indicator 28. Vacuum indicator 28 is 
a plastic or rubber bulb, which collapses under the negative pressure of 
the vacuum drawn by pump 20. 
Mixing cartridge 30 is preferably constructed of a disposable 
semi-transparent plastic, which allows the admixture of the constituent 
components 4 to be viewed. Cartridge 30 includes two telescoping tubular 
cylinders 40, 50. Both cylinders 40, 50 have open proximal and distal 
ends. Outer cylinder 40 axially receives inner cylinder 50 in a 
telescoping configuration. The outer diameter of inner cylinder 50 is 
concentrically seated against the inner diameter of outer cylinder 40. The 
outer peripheral surface of inner cylinder 50 is in a tight but not 
hermetically sealed engagement with the inner peripheral surface of outer 
cylinder 50 in a piston like manner. An air impermeable piston plug 32 is 
disposed within inner cylinder 50 approximate its distal end, so as to 
close the distal end of inner cylinder 50. Plug 32 is axially slidable 
within inner cylinder 50 for expelling the mixed cement compound 6 from 
cartridge 30 when the cartridge is connected to a cement gun. 
Outer cylinder 40 includes a threaded outer rim 42 adjacent its open 
proximal end. Threaded rim 42 allows connection of cap 60 and funnel 
attachment 90 to cartridge 30. While outer cylinder 40 is shown herein as 
including an outer thread rim, any suitable connection structure can be 
employed to provide the connection to funnel attachment and cap 60. Outer 
cylinder 40 also includes an annular end flange 44, which extends 
outwardly approximate its open distal end, and a block protrusion or key 
46, which protrudes inwardly. As shown in FIGS. 2 and 5, the inner surface 
of outer cylinder 40 has a plurality of pressure evacuation grooves 41, 
which extend longitudinally from its proximal end. 
Inner cylinder 50 includes a pair of O-rings 52, which are seated within 
annular grooves 51 formed approximate its proximal end. O-rings 52 provide 
a hermetic seal between cylinders 40, 50. As shown in FIG. 3, inner 
cylinder 50 has an L-shaped longitudinal channel 53. Channel 53 includes a 
short lateral section 57 which connects to a major longitudinal section 
54. The L-shaped channel allows the inner cylinder 50 to be rotationally 
and axially movable between two positions: a fully extended mixing 
position wherein key 46 is seated within lateral section 57, and a vacuum 
release and retracted position wherein the key is accommodated within the 
major longitudinal section. As shown in FIGS. 3, 10 and 11, key 46 of 
outer cylinder 40 is seated within channel 53 of inner cylinder 50. In an 
alternative embodiment, illustrated in FIG. 3A, the channel 53' is formed 
in a stepped configuration and includes a short intermediate lateral 
section 55', which connects the major longitudinal section 54' to the 
minor longitudinal section 56 and a short lateral end section 57'. Stepped 
channel 53' and key 46 provide a two stage vacuum release mechanism for 
cartridge 30. Stepped channel 53' allows inner cylinder 50 to be 
rotationally and axially moved between three positions: a fully extended 
mixing position, an intermediate vacuum release position, and a retracted 
applicator position. 
As shown in FIGS. 2, 6 and 7, cartridge cap 60 includes an annular rim 62. 
The inner surface (not shown) of rim 62 is threaded to mate with the 
threaded rim 42 of outer cylinder 40 to provide a hermetically sealed 
connection over the proximal end of outer cylinder 40. Cap 60 includes a 
one way valve port 64, which is connectable to vacuum pump 20. Cap 60 
includes a centered cement outlet port 66. The outer surface of cement 
port 66 is threaded to allow connection of cement nozzles 80 to cap 60. 
As shown in FIGS. 6 and 7, agitator 70 includes a handle 71 and an 
elongated shaft 72 reciprocally disposed within outlet port 66 of cap 60. 
Shaft 72 includes a tubular outer sleeve 74 and an inner rod 76 axially 
disposed within sleeve 74. Shaft sleeve 74 is frangible and has a 
detachable distal end 75. Agitator paddles 79 extend radially from distal 
end 75 of shaft sleeve 74 for assisting in the mixing of the constituent 
components 4 of the bone cement. The distal end of inner rod 76 terminates 
in an integral dumbbell shaped end plug 78. The small diameter of the 
middle segment 77 of dumbbell shaped end plug 78 is positioned approximate 
to an annular notch 73 formed in shaft sleeve 74. As shown in FIGS. 6 and 
7, distal end 75 of sleeve 74 can be detached from shaft 72 so that the 
mixed cement compound 6 can be expelled therethrough. When shaft 72 is 
withdrawn to its outer extreme from cartridge 30, paddles 79 abut against 
the inner wall of cap 60 and distal end 75 of sleeve 74 is fitted within 
outlet port 66 of cap 60. The configuration of dumbbell shaped end plug 78 
allows rod 76 to be bent at middle section 77 of end plug 78 while sleeve 
74 is fractured at notch 73. The hollow distal end 75 of sleeve 74 remains 
within outlet port 66 of cap 60 to provide a passage for the mixed cement 
compound 6 to be expelled. 
An alternative embodiment of the break away sleeve 74 and dumbbell shaped 
distal plug is illustrated in FIG. 7A. As illustrated in FIG. 7A, 
elongated shaft 72' includes a tubular outer sleeve 74' and an inner rod 
76' axially disposed within the sleeve. Shaft sleeve 74' is frangible and 
has a detachable distal end 75'. In the embodiment of FIG. 7A, the inner 
rod 76' is formed from a flexible polymer such as is commonly used in 
medical tubing and is of a constant inner and outer diameter. A plug 78' 
is secured within the distal end of inner rod 76' adjacent the detachable 
distal end 75' of the outer sleeve 74'. Mixing paddle 79 is connected to 
the distal end 75' of sleeve 74' and functions in a similar manner as 
described earlier. In use, after the constituent components of the bone 
cement are throughly mixed as discussed earlier, the mixing paddle is 
drawn to a position adjacent the cap 60. The outer sleeve is bent 
sufficiently to cause it to break at the score line or notch 73'. During 
bending of the outer sleeve, the inner rod 76' (made of the flexible 
polymer tubing) flexes or compresses an amount sufficient to allow the 
outer sleeve to break. Once the outer rod is broken, the user pulls on 
handle 71' which is connected to inner rod 76' by an adapter as 
illustrated. As the handle, inner rod and the remaining outer sleeve are 
pulled away, the distal plug 78' is pulled from the center of mixing 
paddle 79 to allow cement to exit therethrough. 
As shown in FIGS. 1, 10 and 11, cement nozzles 80 are of conventional 
design and include an elongated neck 82 and a coupling part 84, which is 
adapted to be fitted to outlet port 66 of cap 60. As shown in FIGS. 1 and 
8, funnel attachment 90 includes a conical flange 92 and an annular neck 
94. Neck 94 has a threaded inner surface (not shown), which allows the 
funnel to be connected to the proximal end of cartridge 30. 
FIGS. 8-11 demonstrate the use of kit 2 in the preparation of bone cement. 
Kit 2 is packaged in an external packaging (not shown) with funnel 
attachment 90 connected to cartridge 30. One will notice that cartridge 30 
is packaged in tray 10 in its extended mixing position for the convenience 
of the user. As shown in FIG. 8, the cement constituent components 4 of 
the cement are poured into mixing cylinder 30 through funnel 90. Once the 
proper volumes of the various constituent components 4 of the cement have 
been poured into the cartridge, funnel attachment 90 is removed and 
discarded. Cap 60 is then removed from tray 10 and attached to cartridge 
30. Vacuum pump 20, tubing 26, and vacuum indicator 28 are also removed 
from tray 10 and connected to valve port 64 of cap 60. Once cap 60 and 
vacuum pump 20 are connected to cartridge 30 as shown in FIG. 9, a vacuum 
is drawn within cartridge 30 by manually reciprocating shaft 24 of vacuum 
pump 20. Vacuum indicator 28 collapses to indicate that the cartridge is 
at the desired vacuum pressure. The vacuum pump may then be removed and 
the vacuum is maintained by a one-way check valve (not shown) within cap 
60. The constituent components 4 of the cement are then mixed by manually 
reciprocating agitator 70 in a manner well known in the art. When the 
constituent components 4 of the cement have been thoroughly mixed, 
agitator part 70 is pulled to its outer limit so that agitator paddies 79 
abut against cap 60. 
As shown in FIGS. 10 and 11, the vacuum pressure within cartridge 30 is 
then released and cartridge 30 is compressed for use in a cement injector 
gun (not shown). To release the vacuum pressure within cartridge 30, inner 
cylinder 50 is rotated and axially compressed within outer cylinder 40 
from its extended position to its intermediate vacuum release position. 
Inner cylinder 50 is rotated within outer cylinder 40 to move key 46 
through lateral end section 57 into longitudinal section 54 so that the 
inner cylinder can be compressed. With key 46 aligned with section 57, the 
inner cartridge is in its vacuum release and collapsing position. In the 
vacuum release position, the position of inner cylinder 50 within outer 
cylinder 40 locates O-rings 52, which provide the hermetic seal between 
the inner and outer cylinder 40, 50, between the opposed ends of grooves 
41 formed in the outer cylinder 40. Grooves 41 provide an air passage into 
the interior of cartridge 30 around O-rings 52 through channels 41. 
To release the vacuum pressure within cartridge 30 in the alternative 
embodiment of FIG. 3A, inner cylinder 50 is rotated and axially compressed 
within outer cylinder 40 from its extended position to its intermediate 
vacuum release position. Inner cylinder 50 is rotated within outer 
cylinder 40 to move key 46 through lateral end section 57' into 
longitudinal section 56 so that the inner cylinder can be compressed. The 
axial compression of inner cylinder 50 within outer cylinder 40 is 
arrested at its intermediate vacuum release position when key 46 reaches 
intermediate lateral section 55'. In the vacuum release position, the 
position of inner cylinder 50 within outer cylinder 40 locates O-rings 52, 
which provide the hermetic seal between the inner and outer cylinder 40, 
50, between the opposed ends of grooves 41 formed in the outer cylinder 
40. Grooves 41 provide an air passage into the interior of cartridge 30 
around O-rings 52 through channels 41. Once the pressure within cartridge 
30 has been equalized, inner cylinder 40 is rotated again to move key 46 
along lateral intermediate section 55 into longitudinal section 54'. Now 
inner cylinder 50 can be completely compressed into outer cylinder 40 to 
its retracted position. 
Once cartridge 30 is compressed into its retracted position, distal end 75 
of sleeve 74 of the agitator is broken off and discarded as shown in FIGS. 
6 and 7. When agitator 70 is broken off, plug 78 is pulled from the cap 
and outlet port 66 is opened. The suitable cement nozzle 80 can now be 
affixed to outlet port 66, and cartridge 30 inserted into the applicator 
gun (not shown). 
It is understood that the above description does not limit the invention to 
the details given, but may be modified within the scope of the following 
claims.