A APPARATUS FOR m AMD DELIVERING BO CEMENT
FIELD OF THE INVENTION
The present invention relates to an apparatus for mixing and
delivering bo cement or the like.
BACKGROUND OF THE E l Q
Orthopaedic bone cement is used throughout the world to secure
hip, knee and other metallic prostheses in an appropnate medica! position. Also,
bone cement ca be used to replace and/or repair damaged bone, such as a bone
void filling and spina! column with degenerative intervertebral discs by permanently
stabilising adjacent vertabrae by fusion.
Bone cement for both Joint surgery and bone void filling is generally
provided as two or more components, often a powder and a liquid, that, when
thoroughly mixed together, form a paste or cement. Thorough mixing of the
components is necessary to avoid brittle or ho spots. After mixing, the ce en
generally has to be used quickly before it sets hard.
Bone void filling is used i the repair of osteoporotic bone, typically
after fracture, by stabilising the bone and allowing bone growth. In some cases
bone growth stimulants are added to the materials to hasten healing. Calcium
based sulphates and phosphates materials are typically used. The principles of
mixing apply equally to both bone cement and bone void filling cements.
Bone cement is produced by thoroughly mixing together two
components, usually ei y ethacry!a monomer liquid and
polymethylmethacrylate (P A powder. This type of material s typically used In
Joint surgery including hips, knees and small joints such as the shoulder, hand and
wrist, and foot and ankle.
The mixing Is usually carried out using a simple bowl and spatula.
The liquid and powder components are put nto the bowl and the surgeon or
assistant uses a pestle or spatula to thoroughly ix the components. The surgeon
then removes the required amount of cement and manipulates it by hand before
inserting t in o a preformed cavity or applying it to a resected bony surface where
the prosthesis is to be positioned. Cement may be applied by hand or may be put
into a syringe and applied separately. However, this simple mixing has two major
drawbacks.
Firstly, free methylmethacryiate fu es are emitted fro the mixture
ft is desirable to remove these fumes, or prevent them from escaping into the
atmosphere, since they have an unpleasant odour and may be harmful to operating
room personnel The fumes are known to cause nausea and giddiness and are
generally objectionable, particularly to the nurses who carry out the mixing. There
has also been concern that long term exposure to these fumes results in a more
serious health risk. Current employment law relating to occupational health mean
medical staff must now be protected against the exposure to hazardous
substances.
Secondly, a very high mixing efficiency is required to produce a
homogenous cement materi al During the mixing process, air is naturally
introduced into the mixture since a r is inherently existent within the powder and
also in and around the mixing vessel. Air bubbles are also produced by the "boiling
off' of monomer which occurs during the mixing process. The introduction of air
produces a weak cement and, since the joint must usually support a heavy load, it
is important to reduce the amount of air in the mixture as much as possible in order
to improve the mechanical strength of the cement material.
n order to eliminate as much air as possible from the mixture,
desirable for most types of cement, mixing is now preferably carried out in a closed
vessel, most preferably under vacuum. Th s considerably reduces the amount of
air in the mixture. Mixing in a conventions! bowi and spatula system can produce a
product with a porosity value of 20% o 25% n a vacuum mix, the porosity value is
often reduced to levels below 5%
As mentioned above, calcium phosphates and sulphates can be
used as another type of bone cement material, which does not necessarily need to
be mixed in a vacuum. Co.nventiona.Uy, th s type of bone growth stimulant is
prepared paste form and is delivered to an application site.
Several devices for mixing the cement are available. Some of these
are n the form of hand-held mixing bowls as mentioned above, WO 93/ 0892
describes an improved bow mixer. The substances to be mixed are placed by
means of a rotating paddle extending nfo the bowl to which a vacuum s applied.
The substances are mixed by means of a rotating paddle extending in o the bowl
which is rotated manuaily by means of a handle extending through the lid of the
bowl. n some applications, an example of which is disclosed in WO 93/1 0892,
bow mixing is favoured. Many surgeons prefer to "hand pack" the cement. Bowl
mixing tends to be preferred by nurses who are used to the convenience of mixing
in this vessel; a bow! is easier to use and it is important that nurses feel confident
since timing is very crucial and the mixture must be "right first time". Many
surgeons also tend to prefer owl mixers because they can easily take samples of
the cement from the bowi a any time to determine the progress of polymerization
as if Is crucial that the mixture does not begin to set before it is applied.
However, in some applications, it is preferable or necessary to apply
the mixed cement to the bone by means of a syringe. Indeed some surgeons,
particularly in Europe, prefer syringe-type application to "hand packing". If the
cement is mixed in a bowl, it must then be transferred to a dispensing syringe which
can be messy and time consuming and may expose the mixture to more air
entrapment. This problem has been overcome by combining a mixing chamber
with a syringe. Although advantages can be obtained with a simple closed mixing
chamber/syringe combination, creating a vacuum can provide additional
advantages. For example, EP 0 8658 discloses a device for mixing bo e cement
comprising a mixing container connected to a feed device. A vacuum source may
be connected to the feed device for mixing the substances under vacuum. This
device has proved to be a very efficient mixing and transfer system and eliminates
the need to transfe the mixed cement from the mixing bowl to a syringe.
However, the mixing paddle of EP 0 1 8658 is rotated by a rotary
electric drive motor. This makes the device costly and space consuming and
requires specialist and time-consuming installation. The device is not easilyportable
and its use s, therefore, not particularly flexible,
US 4,758,096 and US 3,606,094 a so disclose bone cement mixers
in which the cement s mixed in the dispensing vessel, n US 4,758,096, the mixing
is effected manually by means of a "masher" plate-type agitator. The masher plate
is attached to a shaft attached to a handle. The agitator is movable in the chamber
hoth axially and rotatably to permit mixing of the cement by the user moving the
handle vertically and rotatably,
In the device of US 3,608,094, the mixing element comprises an
elongate conduit having paddle projections. The paddles are rotated by a rotating
motor or by hand.
EP 0744991 discloses a bone cement mixer in which the mixing
chamber forms the body of a dispensing sy nge wherein a nozzle can be attached
to o e end of the mixing chamber so as to dispense the bone cement
GB 241 1849 discloses an apparatus for mixing bone cement and
discharging the ixed bone cement from a mixing container to a discharging
device such as a syringe or syringes.
Another product on the market that provides a mixing and dispensing
device is the H ac T ) 7 (provided by Summit: Medical Ltd., see
http;//www.summit-medicaLco,uk/product hivac7,hf This device allows for
mixing, e.g. biologies, in a mixing chamber. The HiVac(TM) 7 provides a mixing rod
having a diameter of 8 mm, Once the mixing phase is complete, a cap can be lifted
from one end to reveal a " er" connection to which a nozzle can be attached. The
mixing chamber then also acts as a dispensing chamber and the bone cement can
be dispensed through the nozzle.
The bone cement mixing and dispensing devices discussed above
have the advantage of providing an apparatus that both mixes and dispenses bone
cement material.
Generally, these mixing apparatuses discussed are made to hold a
standard volume of cement of 40cc or mo e i the mixing and dispensing
chambers. Sometimes, however, there is a need for only a small amount (e.g.
cc) of cement, for example for smaller joints such as ankles etc, where a volume of
.5-20CC, fo example, is needed; or for a combination of calcium based sulphates
and phosphates. The bulky nature of chambers having, say, o volume is not
easily manoeuvred in a smaller target site (for example, ankle joints etc.). Also, the
cement components are expensive and use of a greater volume than needed is
wasteful and costly. Simply reducing the size of the apparatuses discussed above
causes the components therein to become weak and to easily break. For example,
simply reducing the size of the components shown in the Vac(T ) 7, and
particularly the rod, makes these components weak and prone to breaking. There
is therefore a need for a device that can cope and assist in treatment at smaller
target sites.
Further, optimum mixing occurs in the above devices when the
chambers are mostly full - e.g. -80% full. When a chamber is ~80% full, this allows
for a mixer paddle or disc to push through the mate al and have the resistance
from the bone cement material, caused by the material being compressed against
the chamber bottom to push the material through the paddle or disc. As the paddle
or disc is then returned through the chamber, the material is again pushed through
the paddle or disc by resistance. However, if the devices discussed above were to
be used for treatment in smaller target sites, if would be necessary to use a smaller
amount of bone cement material that would be less than the volume of the
chambers discussed above. Simply providing a smaller amount of bone cement
material into a chamber with, say, 40cc volume, or more, has disadvantages. For
example, if the chamber were only ~40% full, the material simply clings to the
paddle or disc until the paddle or disc hits the bottom o the chamber where if would
be pushed through the paddle. Before mixing the material again, the paddle or disc
has to travel 60% of the chamber, which does not provide efficient and optimum
mixing, Therefore, there is a need for a device that provides adjustable volumes n
the chamber to allow for a range of volume of bon cement material.
The present invention aims to overcome the above-mentioned
problems. Of course, several types of bone cement material have been discussed
above, but the present invention is not so limited to these types of bone cement
material The present invention aims to provide a device for known types of bone
cement materia! a d bone cement material that may be developed in the future.
SUMMARY OF THE INVENTION
n one aspect of the present Invention, there is provided a device for
mixing bone cement material, the device comprising:
a mixing body having a chamber, and wherein the mixing bod has an open
end;
a lid arranged to be fitted to the open end;
means f mixing bone cement material in the chamber, the means for
mixing comprising a rod extending through the lid and info the chamber, wherein
the rod has a frangible portion;
said lid comprising a cap moveable to a first position covering the frangible
portion of the rod, and to a second position revealing the frangible portion.
n a preferred embodiment, the mixing rod can be moved vertically
and/or ro a ab y n the chamber to assist n mixing the bone cement material. n a
preferred form, the means for mixing the bone cement material comprises a
'mashing or paddle portion to assist in the mixing of the bone cement, in the
chamber. The 'mashing' or paddle portion can take the form of a 'masher' paddle or
a flat-type paddle, a d, most preferably, a paddle portion extending radially from the
rod.
n a preferred embodiment, a lid is provided at an open end of the
mixing body. The lid preferably has a moveable cap that can move to a first
position to cover a frangible portion of the rod When the cap is cove ng the
frangible portion of the rod, the rod is advantageously reinforced against snapping
whilst the user is mixing the bone cement in the chamber.
In a further embodiment of the present Invention, there is provided
means for securing the cap in the first position. This allows for the cap to be
secured In a position that covers the frangible portion of the rod so as to reinforce
he rod during the ixi g phase. n a preferred embodiment, the means for
securing the cap in a first position is a removable clip.
In preferred embodiments of the present invention, the mixing body
chamber and piunger are preferably cylindrical, and most preferably circular
cylindrical.
n a preferred fo m of the present invention, the lid comprises an
inner cap and a movable outer cap. in a preferred embodiment, the inner cap is
attached to the open end of the chamber and the outer cap is movable relative to
the inner cap This allows for the open end of the chamber to remain closed during
the mixing phase, but to also allow for the rod to be reinforced by the outer cap
when this is moved i to the first position,
In a preferred form, the frangible portion is a weakened or snap
portion, preferably formed by a slight indent or notch provided in the rod. This
allows for the user to snap the rod after the mixing phase.
The device is preferably used for mixing and dispensing bone
cement material. In a further embodiment of the present application, the mixing
body preferably has a second open end. n a preferred form, th mixing body has
means for dispensing the cement located at the second open end to assist in
dispensing the bone cement material after the mixing phase. Preferably, the means
for dispensing the bone cement material is a plunger movable by the application of
force through the chamber.
Preferably, the Inner cap has a delivery port that allows for bone
cement material to be dispensed after the bone cement material has been mixed.
In a preferred embodiment, the outer cap has a protrusion extending towards the
delivery port of the inner cap so that it can be Introduced into the delivery port.
Advantageously, the protrusion blocks the delivery port such that no bone cement
material can escape. In a preferred form, the delivery port of the inner cap includes
a uer port so as to receive a nozzle for dispensing the bone cement material.
Preferably, he mixing or padd e portion of the rod is a so as to
be engaged b the protrusion of the outer cap such that, when ihe outer cap is
moved down to fi over the inner cap, the protrusion pushes the paddle portion to
the side of the chamber. Advantageously, this ensures that the paddle portion is
not occluding the delivery port of the Inner cap.
In another aspect of the present invention, there is provided a device
for mixing bone cement material., the device comprising;
a mixing body having a chamber, and wherein the mixing body has a first
end and a second end;
a lid arranged to be fitted to the first end
means for mixing bone cement materia! in the chamber, the means for
mixing comprising a rod extending through the lid and info the chamber;
means for dispensing bone cement material from said mixing body attached
to a second end of the mixing body, wherein the means for dispensing the bone
cement material is a plunger movable by the application of force through the
chamber, said plunger provided to set an adjustable volume in the chamber prior to
mixing;
said device further comprising:
means for positioning the plunger between the first and the second end of
the mixing body to define a volume of the chamber; and
means for maintaining the position of the plunger so as to maintain the volume of
the chamber during mixing.
The means for positioning the plunger between the first and the
second end of the mixing body advantageously allows the user to define a volume
of the chamber of the mixing body. Therefore, in this embodiment of the present
invention, the user can adjust the volume of the chamber for an amount of bone
cement material that is necessary for a particular type of surgery.
There is also provided means fo maintaining the position of the
plunger so as to maintain the vo ume of the chamber du ng mixing.
Advantageously, this allows the user to first adjust the amount of volume n the
chamber and to then set the volume within the chamber so that the user can then
mix the b ne cement material for a particular volume.
Preferably, the means for positioning the plunger and the means for
maintaining the position of the plunger comprises a screw thread arranged on
outer surface of the plunger, and a nut having a screw thread to be received by the
screw thread arranged on the outer surface of the plunger, the nut further having a
recess having a screw thread to be received by a screw thread located at the
second end of the mixing body. This allows for the user to first position the plunger
within the chamber and then to securely screw a nut to the mixing chamber such
that the plunger is maintained in a position between the first end and the second
end of the mixing body during the filling and mixing phases. This then
advantageously allows for the user to adjust the volume for a particular amount of
bone cement material that is necessary for a particular type of surgery.
The features of the second aspect, relating to the adjustable mixing
volume, are also advantageous for the first aspect of the invention.
In a preferred embodiment, for both aspects, there is also provided a
base that is adapted o receive the plunger to stabilise the device during a mixing or
filling phase.
Preferably, the mixing rod has a handle or knob located on the end
so that the user can easily move the rod vertically and/or rotatabiy.
In a preferred embodiment of the present invention, the volume of
the chamber is between 0 cc.
Preferably, the outer cap can be lifted a distance away from the inner
cap of between 2 3 mm.
In a preferred form, the diameter of the rod is 4 mm
In a further embodiment of the present invention, there may be
provided a vacuum port located on the lid so as to receive a vacuum pump in the
chamber. The vacuum pump advantageously creates a vacuum in the chamber.
I another aspect of he present invention, there is provided a
method of mixing bone cement material, said method having the steps of:
providing bone cement components in a mixing chamber of a mixing device;
fitting a lid to an open end of the mixing chamber to close the chamber;
mixing bone cement material using a rod extending through the lid and in o
the chamber of the mixing device, wherein the od has a frangible portion; said
method characterised by
positioning the lid in a first position so as to reinforce the frangible portion
from breakage during mixing;
positioning the lid in a second position so as to reveal the frangible portion;
and
snapping the rod at the frangible portion.
In this embodiment, he method of mixing the bone cement mate al
allows the user o mix the bone cement material and a so allows for the frangible
portion of the rod to be reinforced during mixing.
In a preferred form, the steps of positioning the fid to reinforce the
frangible portion comprises providing an outer cap and an inner cap on the lid and
preferably moving the outer cap away from the inner cap to a first position. This
advantageously allows for the outer cap to cover the frangible portion during mixin
Preferably, the outer cap can be removed after the mixing phase to
reveai a delivery port located on the inner cap so that the user can dispense the
bone cement material In a preferred embodiment, the delivery port includes a luer
port that can receive a nozzle so as to assist in the dispensing of the bone cement
material.
In a further aspect of the present invention, there Is provided a
method of mixing bone cement material, said method having the steps o :
selling a volume of a chamber of a mixing device with a plunger, said
plunger movable through the chamber with the application of force between a first
and a second end of the mixing device;
maintaining the position of the plunger so as to maintain ihe volume of the
chamber during mixing;
mixing the bone cement materia! in the chamber of the mixing devi ce
in this embodiment, the method allows the use to adjust the volume
of the chamber of the mixing body. This advantageous when an amount of bo e
cement mate al different to the total volume of the chamber is needed for a
particular type of surgery, The volume ca then be adjusted by the user and
maintained for use during the filling and mixing phase.
In a preferred form, the steps of setting the volume and maintaining
the set volume comprises providing a screw thread arranged on an outer surface of
the plunger and providing a ut having a screw thread to be received by the screw
thread arranged on the outer surface of the plunger, the nut further having a recess
having a screw thread to be received by a screw thread located at the second end
of the mixing body. This advantageously allows the user to screw the ut o to the
second end of the mixing body.
In one embodiment of the present invention, and when the bone
cement material is ready to be dispensed, the user can unscrew the nut from the
second end of the mixing body and the plunger can be axsaliy moved through the
chamber to push the bone cement material out through a delivery port located on
the lid.
n an alternative embodiment o the present invention, and when
bone cement material is ready to be dispensed, the user can rotate a second end of
the plunger through the scre thread provided on the nut to axially move th
plunger through the chamber. This advantageously provides a greater force when
dispensing the bone cement material through a delivery port and is particularly
advantageous for viscous bone cement material.
In another embodiment of the present invention, a vacuum can be
created in the chamber by attaching a vacuum pump to a vacuum port on the lid.
Exemplary embodiments of the present invention will now be
described, by way of example only, with reference to the figures.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a bone cement mixing and dispensing device in
accordance with embodiment of the present invention.
Figure 2 shows an enlarged portion of the bone cement mixing and
dispensing device shown in Figure 1 prior to delivery of the materia! to be mixed
Figure 3 shows an enlarged portion of the bone cement mixing and
dispensing device shown in Figure 1, in use, prior to delivery of the material to be
mixed.
Figure 4 shows the bone c menl mixing and dispensing device of
Figure 1 pre-mixing or du ng the mixing phase.
Figure 5 shows the bone cement mixing and dispensing device of
Figure 1 prior the mixing phase.
Figure 6 shows a bone cement mixing and dispensing apparatus in
accordance with another embodiment of the present invention.
Figure 7 shows a cross-sectional view of a cap in n open position in
accordance with an embodiment of the present invention
Figure 7a shows a cross-sectional v ew of a cap in a closed position
in accordance with an embodiment of the present invention.
Figure 7b shows a cross-sectional view of the cap as shown In
Figure 6a.
Figure 8 shows a plan view of the cap shown in Figures 6a and 6b
Figure 9 shows a cap In accordance with another embodiment of the
present invention.
Figure 10 shows the bone cement mixing and dispensing device of
Figure 1 with a nozzle attached thereto.
Figure shows the bone cement mixing and dispensing device of
Figure 1 during the dispensing phase.
Figure a shows an alternative embodiment of the bone ceme t
mixing and dispensing device of Figure 1 du ng the dispensing phase.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 shows a complete assembly of a bone cement mixing and
delivery device 1 in accordance with an embodiment of the present invention. The
bone cement and delivery device 1 can be used to mix and deliver bo e cement.
As can be seen in Figure , there is provided a mixing/dispensing body 2 having a
chamber 23 for receiving bone cement material (not shown). The
mixing/dispensing body 2 has a first open end 2 1 and a second open end 22. The
mixing/dispensing body 2 is preferably cylindrical, a d more preferably circular
cylindrical However, the mixing/dispensing body 2 may take other forms.
As shown n Figure , there may also be provided an inner cap 4
and an outer cap 4 1 (described in more detail below) iocated at, and releasably
fastened to, the first open end of the mixing/dispensing body 2.
Also, there may be provided a plunger 3 having a first end 3 1 and a
second end 32, as shown in Figure 1 The first end 3 1 of the plunger 3 may Include
a piston 35 that can be introduced into the mixing/dispensing body 2 at the second
open end 22, The piston 35 is preferably flush with an inner surface of the
mixing/dispensing body 2 The plunger 3 may have a handle or knob on the
second end 32 to assist the user in using the plunger 3 The plunger 3 Is preferably
cylindrical and more preferably circular cylindrical. However, the plunger 3 may
take other forms.
As shown In Figure 1, there may also be provided a rod 42 to assist
in mixing the bo cement material The rod 42 may ovably extend through
openings not shown) of the inner cap 4 and outer cap 4 1, The rod 42 has a first
end 43 and a second end 44 At the second end 44 of the rod 42, in the
mixing/dispensing chamber 23, is provided a 'mashing 1or paddle portion 44 to
assist in mixing the bone cement material n a preferred embodiment, the diameter
of the rod is between 2-5 , and is preferably 4 mm in diameter,
A base 34 may be provided, as shown Figure . The base 34 may
be adapted to receive the second end 32 of the plunger 3 to stabilise the
mixing/dispensing device 1 du ng a mixing or filling phase.
As can he seen in Figures 1, 2 and 3, the first end 3 1 of the plunger
3 can be received by the second open end 22 of the mixing/dispensing body 2, in
this arrangement:, the piston 35 is, therefore, introduced in o the mixing/dispensing
body 2 and is flush with an inner surface of the mixing/dispensing body 2, The
plunger 3 has, on its outer surface, a screw thread extending from the firs end 3 1
to the second end 32, A nut 33 is located on the screw thread of the plunger 3,
The nut 33 includes a recess 331 having a screw thread to fasten to a screw thread
located on the outer surface of the second end 22 of the mixing/dispensing body 2.
n this arrangement, the piston 35 can be Introduced ink? the second open end 22
of the mixing/dispensing body 2 and can be moved,, in a longitudinal direction
(shown by the arro in Figure 3 , through the mixing/dispensing body 2 to provide a
specific volume required in a mixing/dispensing chamber 23, The piston 35 can
then be held in place by screwing the nut 33 on to the screw thread located on the
outer surface of the second end 22 of the mixing/dispensing body 2. This then
provides a volume within the mixing/dispensing chamber 23. In a preferred
embodiment, the volume of the chamber can be between - 1 cc
Once the volume has oeen set by the user with the technique
discussed above, bone cement material is introduced into the first open end 2 1 of
the mixing/dispensing body 2, e.g. through a funnel (not shown),
Either before or after the bone cement material has been introduced
info the mixing/dispensing chamber 23, the second end 32 of the plunger may be
positioned, and held, in a recess of a base 34. The base 34 assists in keeping the
bone cement mixing and delivery device 1 still during the filling and/or mixing
phase.
Referring now to Figures 1 and 4, the lid 4 s now described. After
the bone cement material has been introduced into the mixing/dispensing chamber
23, the lid 4 is fitted over the first open end of the mixing/dispensing body 2, The lid
has an outer cap 4 1 and a inner cap 4 1 . The inner cap 4 1 may have a recess
having a screw thread thereon which can mate with a screw thread located on the
outer surface of the first open end 2 1 of the mixing/dispensing body 2. The outer
cap 4 1 can fit over the inner cap 4 1 and is axialiy movable relative to the inner cap
4 11. The lid 4 can be attached to the mixing/dispensing body 2 by mating the
screw thread of the inner cap 4 1 with a screw thread located the outer surface
of the first end 2 1 of the mixing/dispensing body 2. Other eans could be provided
to fasten the l d to the chamber
The outer cap 4 1 and the inner cap 4 11 include an opening (not
shown) through which a rod 42 moveably extends. At the second end of the rod 42,
in the chamber, is provided a 'mashing' or paddle portion 44 to assist in mixing the
bone cement material i the mixing/dispensing chamber 23. The rod 42 extends
from the padd e portion 44 and through the opening of the outer cap 4 1 and inner
cap 4 11 to a first end 43. The 'mashing' or paddle portion 44 could be radially
extending arms (not shown) from the rod 42 or a asher paddle, or a fiat-type
padd e portion. Other types of "mashing' or paddle portions could be used,
In use, the oute cap 4 1 is lifted a distance away from the inner cap
4 1 and the first end 2 1 of the mixing/dispensing body 2 In a preferred
embodiment, the outer cap 4 1 lifted awa by a distance of between 2-3 . In
order to maintain the distance between the outer cap 4 1 and the Inner cap 411, a
clip 50 may be attached around the circumference of the inner cap 4 1 and/or the
outer cap 4 1. The clip 50 therefore holds the outer cap 4 1 in place during the
mixing phase. The outer cap 4 1 may also include a reinforcing portion 46 that
protrudes from the hole in which the rod 42 extends through. The reinforcing
portion 46 provides support to the rod 42 during the mixing phase so that the rod 42
does not snap or break.
The mixing phase is achieved by a user axially and/or roiatably
moving the rod 42 so thai the paddle portion 44 ixes the bone cement material
the mixing/dispensing chamber 23. The first end 43 of the rod 42 may be provided
with a handle or knob 43 to assist the user in mixing the bone cement material
As is shown in Figure 5, when the clip 50 is removed from the outer
cap 4 and/or inner ca 4 11, the outer cap 4 1 is axiai moveable relative to the
inner cap 4 11 and the mixing/dispensing body 2
Figure 6 shows a complete assembl of a mixing device 1 in
accordance with another embodiment of the present invention. The mixing device 1
of Figure 6 is similar to that of Figure 1 except that a vacuum port 400 may be
included n the outer cap 4 1 and inner cap 1 so as to be in communication with
the chamber 23. A vacuum pump (not shown) may then be received by the
vacuum port 400 so as to create a vacuum in the chamber 23
Figures 7, 7a and 7b show the inner cap 4 11, outer cap 4 1 and rod
42 in more detail As can be seen in these figures, the inner cap 4 1 has a side
wall 8 1 extending from an upper wall 63. On the inner surface of the side wall 1,
there is provided a screw thread to engage and mate with a screw thread located
on the outer surface of the first end 2 1 of the mixing/dispensing body 2. The upper
wall 63 of the inner cap 4 1 also may include a delivery port 82 extending therefrom
towards the outer cap 4 1 and a circumferential wall 5 located around the delivery
port 62 providing a gap 66 therebetween.
The outer cap 4 1 has a side wall 7 1 to fit over the side wall 1 of the
Inner cap 4 11, The outer cap 4 1 has an upper wall 73 and a circumferential wall 74
extending therefrom so as to ill over the delivery port 62 and circumferential wall
65 of the inner cap 4 1. The circumferential wall 74 of the outer cap 4 1 is closed by
an upper surface 77 A protrusion 72 extends from the upper surface 77 towards
the delivery port 62 of the inner cap 4 1 so that the protrusion 72 can be introduced
into the delivery port 62. A circumferential wall 75 also extends fro the upper
surface 77 towards the gap 6 provided between the circumferential wall 65 and the
delivery port 62 of the inner cap 4 1. The circumferential wall 65 includes, on its
surface, a uer thread for connection to a uer fitting during the delivery phase.
As shown in Figure 7, the rod 42 extends through holes 64 and 80 of
the inner cap 4 and outer cap 4 1 respectively. The rod includes a weakened or
snap portion 80, which can be formed for example by a slight indent or notch the
material of the rod 42. The outer cap 4 1 also includes a reinforcing portion 46
which extends from the upper surface 73 of the outer cap 4 .
A method of using the outer cap 4 1 during and after mixing is now
described with reference to Figures 7, 7a and 7b.
During mixing, the outer cap 4 1 is raised from the inner cap 4 11 so
as to cover the snap portion 80 The outer cap 4 1 may then be held in position by a
clip 50 as shown in Figure 4). The rod 42 can then be moved verf ca!y and/or
rotatabiy by the user to mix the bone cement material in the mixing/dispensing
chamber 23 (as shown in Figure 1). The snap portion is protected against
breakage by the outer cap 4 1. Other means for holding the outer cap 4 1 in position
may also be used.
After the mixing phase, the outer cap 4 1 is then moved down
toward/over the inner cap 4 1 . The protrusion 72 of the outer cap 4 1 naturally also
moves down and engages the paddle portion 44 of the rod 42 and pushes this to
the side of the mixing/dispensing chamber 23 to ensure that the padd e portion 44
is not occluding the delivery port 62. n a preferred embodiment, the protrusion 72
is in the form of a spike. The padd e portion 44 may be shaped so as to be
engaged by the protrusion 72 to assist i moving the paddle portion 44 to the side
of the mixing/dispensing chamber 23,
As can be seen in Figure 7b, the padd e portion 44 of the rod 42 is
moved to ihe side of the mixing/dispensing chamber 23 such that the paddle portion
44 does not occlude the delivery port 62.
Figure 8 shows the outer cap 4 1 when it is moved down towards,
and Is fitted over, the inner cap 4 11. The reinforcing portion 46 has a gap G
through which the snap portion 80 is revealed. The user can then "s ap" the rod 42
at the snap portion 80 to remove a portion of the rod 42. The paddle portion 44
then remains i ho e 64 of the inner cap 4 1. Due to the paddle portion 44 of rod
42 remaining in hole 64 of the inner cap 4 , the padd e portion 44 blocks hole 64
of the inner cap 4 11 to maintain a closed chamber (as shown n Figures 9 and 10),
Figure 9 shows that he outer cap 4 1 can be removed from the inner
cap 4 1 entirety, after the rod 42 has been snapped. As can be seen in this figure,
paddle portion 44 remains in hole 64 of the Inner cap 4 1. The outer cap 4 1 is
removed to reveal the delivery port 82.
Figure shows that a uer fitting or nozzle 1 0 can then be
connected to the luer thread located on the surface of the circumferential wail 65 of
the inner cap 4 1 , The nozzle 0 is then in fluid communication with the
mixing/dispensing chamber 23, As mentioned above, paddle portion 44 remains in
hole 64 of the inner cap 4 11
Figures 1 and 11a show the mixing/dispensing device 1 during the
dispensing phase. Once the outer cap 4 1 has been removed and a nozzle 100
connected so as to be in fluid communication with the mixing/dispensing chamber
23, the bone cement is ready to be delivered to a target site of a patient.
Figure 11 shows the mixing/dispensing device 1 in one embodiment
of the present invention. When the bone cement is ready to be deployed from the
mixing/dispensing chamber 23, the user can unscrew the nut 33 from the second
end 22 of the mixing/dispensing body 2 The nut 33 can be moved along the screw
thread provided on the plunger 3 After unscrewing the nut 33, the plunger 3 can
then be axialiy moved so as to ax!aliy move the piston 35. The piston 35 then
delivers bone cement through the delivery port 62 and, for example, through
n s 1 0 to the target site.
Figure 11a shows the mixing/dispensing device 1 in an alternative
embodiment of the present invention. When the bone cement is ready to be
deployed from the mixing/dispensing chamber 23, the user can rotate the second
end 32 of the plunger 3 The second end 32 of the plunger 3 can have a handle or
knob 321 attached thereto to assist the user in rotating the plunger 3 through the
screw thread provided on the nut 33 to axla!iy move the piston 35. Th s is
particularly useful for viscous bone cement material. Rotating the plunger 3 through
the screw thread provided on the nut 33 causes the bone cement to be deployed
through the delivery port 62 and, for example, through a nozzle 0 attached
thereto.
Although the invention has been described in terms of preferred
embodiments as set forth above, it should be understood that these embodiments
are illustrative only and that the claims are not limited to those embodiments.
Those skilled n the art will be able to make modifications and alternatives in view of
the disclosure which are contemplated as falling within the scope of the appended

claims.
A device for mixing bone cement material, the device comprising:
a mixing body having a chamber, and wherein the mixing body has an open
end;
a lid arranged to be fitted to the open end;
means for mixing bone cement material in the chamber, the means for
mixing comprising a od extending through the l d and into the chamber, wherein
the rod has a frangible portion;
said lid comprising a cap moveable to a first position covering the frangible
portion of the rod, and to a second position revealing the frangible portion.
2 The device of claim 1, wherein the mixing body has a second open end, and
wherein a means for dispensing cement from the chamber is provided at the
second open end,
3, The device of claim 2, wherein the means for dispensing cement is a
plunger movable by the application o force through the chamber.
4. The device of any preceding claim wherein the eans for mixing the bone
cement comprises a paddle portion located in the chamber radially extending from
the rod
5 The device of any preceding claim, said device further comprising means for
securing the cap in the first position.
6 The device of claim 5 wherein the means for securing the cap In the first
position is a removable clip.
7 The device of claim 3, wherein said device further comprising:
means for positioning the plunger between the first and the second end of
the mixing body to define a volume of the chamber: and
eans fo maintaining the position of the plunger so as to maintain the
volume of the chamber during mixing
8 . A device for mixing bone cement material, the device comprising:
a mixing body having a chamber, and wherein the mixing body has a first
end and a second end;
a id arranged to be fitted to the first end;
means for mixing bone cement materia! in the chamber, the means for
mixing comprising a rod extending through the fid and into the chamber;
means for dispensing bone cement material from said mixing bod attached
to a second end of the mixing body, wherein the means for dispensing the bone
cement material is a plunger movable b the application of force through the
chamber, said piunger provided to set an adjustable volume in the chamber prior to
mixing;
said device further comprising:
means for positioning the plunger between the first and the second end of
the mixing body o define a volume of the chamber; and
means for maintaining the position of the plunger so as to maintain the
volume of the chamber during mixing.
9. The device of claims 7 or 8, wherein the means for positioning the piunger
and means for maintaining the position of the plunger comprises:
a screw thread arranged on an outer surface of the piunger; and
a nut having a screw thread to be received by the screw thread arranged
the outer surface of the plunger, the nut further having a recess having a screw
thread to be received by a screw thread located at the second end of the mixing
body.
. The device of any preceding claim wherein the lid comprises:
an inner cap and an outer cap fitted over the inner cap, and wherein the
outer cap is movable relative to the inner cap such that, when the outer cap is
moved away from the inner cap to the first position, the outer cap covers the
frangible portion; and wherein, when the outer cap is moved to the second portion
to fit over the inner cap, the frangible portion of the rod is revealed.
. The device of claim 13, wherein the outer cap has a protrusion that extends
through the chamber to engage with the paddle portion when the outer cap is in the
second position.
2. A method of mixing bone cement material, said method having the steps of:
providing bone cement components n a mixing chamber of a mixing device;
fitting a id to an open end of the mixing chamber to !ose the chamber;
mixing bone cement material using a rod extending through the l d and into
the chamber of the mixing device, wherein the rod has a frangible portion; said
method characterised bypositioning
the lid in a first position so as to reinforce the frangible portion
from breakage du ng mixing;
positioning the lid n a second position so as to reveal the frangible portion;
and
snapping the rod at the frangible portion.
3, The method of claim 2»wherein the steps of positioning the id to reinforce
the frangible portion comprises;
providing an outer cap and an Inner cap on the lid;
moving an outer cap away from an inner cap o a first position.
14, The method of claim 12 wherein the steps of positioning the lid to reveal the
frangible portion comprises;
providing a outer cap and an inner cap on the lid
ving an outer cap to cover the inner cap to a second position.
1 The method of any of claims 1 - , wherein the method further comprises:
positioning a plunger between a first and a second end of the mixing and/or
dispensing body; arid
maintaining the position of the plunger so as to maintain the volume of the
chamber during mixing.
. A method of mixing b e cement material, said method having the steps of;
setting a volume o a chamber of a mixing device with a plunger, sa d
plunger movable through the chamber with the application of force between a first
and a second end of the mixing device;
maintaining the position of the plunger so as to maintain the volume of the
chamber during mixing;
mixing the bone ce ent material In the chamber of the mixing device.
7. The method of claims 1 or 16, wherein the step o setting the volume and
maintaining ihe set volume comprises:
providing screw thread arranged on an outer surface of the plunger; and
providing a nut having a screw thread to be received by the screw thread
arranged on the outer surface of the plunger, the n t further having a recess having
a screw thread to be received by a screw thread located at the second end of the
mixing body; and
screwing said nut onto the second e d of the mixing body.
18. The method o claims 1 or 16 wherein the method further comprises:
dispensing bone cement from the chamber.