Bone cement mixing and delivery device for injection

Field of the Invention

0001The present invention relates generally to a bone cement delivery assembly, one that is particularly suited for mixing a powdered copolymer and a liquid monomer to form a bone cement and delivering the bone cement.

Background of the Invention

0002In many surgical procedures, particularly orthopedic procedures, it is common practice to affix a prosthesis to a bone or joint structure for improving the strength, rigidity and movement of the bone/joint structure. Such prosthetic devices have been widely used, hip joints and knee joints are the most common examples of areas where prosthetic devices are used to reduce or eliminate pain and suffering that exists from typical leg movements.

0003As part of these surgical procedures, it has become common practice to secure the prosthesis to the bone or joint using a cement formed by mixing a polymer powder and a liquid monomer. The two components must be thoroughly blended together to achieve the required consistency for the fully mixed cement. The fully mixed cement is then loaded into a separate dispensing apparatus for placement in the desired area and affixing of the prosthesis to the desired site.

0004Other uses of bone cement include repairing or mending bone fractures or shattered bone occurring from extreme trauma. Bone cement may also be used during cosmetic or dental surgery. Moreover, bone cement may be used as a drug delivery or release system, whereby the bone cement is mixed with antibiotics or other desired drugs and applied to a specific surgical site such that the drugs leach out and are delivered directly to the surgical site. Some bone cements are also designed to be absorbed by the body over time.

0005Because of the necessity for a fairly quick setting material, the cement is almost universally prepared by a surgical assistant during the course of the operation in the sterile operating room. Conventional bone cements are generally polymeric materials which are prepared by copolymerization of the components as needed. Bone cement is prepared by copolymerizng the liquid monomer and the powdered copolymer, such as methyl methacrylate and polymethyl methacrylate or methyl methacrylate styrene. In order to provide a bone cement having the desired properties, the compounds must be uniformly and thoroughly mixed so that a homogeneous reaction product is produced.

0006During the mixing and subsequent chemical reaction various vapors are produced. Due to the noxious and toxic nature of such vapors, it is highly undesirable to be exposed to them, particularly for extended periods of time in the course of multiple preparations. Since it is necessary that the mixing be carried out for extended periods of time to ensure a uniform reaction product and a minimum of concentration of volatile reactants, the period of exposure to harmful vapors can be substantial. Moreover, during the mixing of the constituent components of the cement, air bubbles may be formed within the cement.

0007Most often, the two components forming the cement are mixed in a mixing vessel and, once fully mixed, the cement is manually transferred from the mixing vessel to a dispensing member of a dispensing device. Typically, devices similar to caulking guns are employed for dispensing the fully mixed cement to the desired location in the patient. These devices have a piston which allows the bone cement to remain in the dispensing member.

0008In some other prior art systems, the cement is mixed in one vessel which is then directly connected to a feeding system that enables the mixed cement to be added to a holding tube for use with the dispensing device. The dispensing system, however, is separate and exposes the mixed cement to the surrounding personnel. Furthermore, care must be exercised during the transfer of the mixed cement to the dispenser to avoid introducing air into the cement or to avoid dropping, spilling, or contaminating the cement.

0009Other prior art systems utilize a handle that operates mixing paddles in a closed cylinder for combining the cement constituents. Upon mixing the bone cement, the handle must be removed. Conventional systems incorporate frangible handles that when broken may produce fragments that could contaminate the bone cement.

0010One such device is disclosed in United States Patent <patcit id="pcit0001" dnum="US5551778A"><text>5,551,778 to Hauke et al.</text></patcit> The '778 patent discloses a device having a mixing cylinder and a mixing plunger extending therethrough. The standard powder and liquid components are introduced into the chamber to form a bone cement and the mixing plunger mixes the two components. The mixing plunger has a predetermined break point for breaking the mixing plunger and allowing for its removal from the mixing cylinder. A discharge nozzle is then connected to the mixing cylinder and the mixing chamber is connected to a drive mechanism. The drive mechanism includes a discharge plunger that is passed through the mixing cylinder forcing the bone cement from the mixing cylinder out the nozzle. A portion of the bone cement remains in the discharge nozzle and thus the system does not ensure complete delivery of the bone cement into the patient.

0011Another such device is disclosed in United States Patent <patcit id="pcit0002" dnum="US5879116A"><text>5,879,116 to Barker et al.</text></patcit> The'116 patent discloses a device having a mixing chamber integral with a delivery chamber. The bone cement components are introduced into the mixing chamber and a paddle having a handle extending from the mixing chamber is utilized to mix the components and form the bone cement. Once the components are adequately mixed, a passage way is opened between the mixing chamber and the delivery chamber. The handle is actuated causing rotation of the paddle and of an auger disposed within the delivery chamber. The paddle transfers the bone cement from the mixing chamber to the auger. The auger has threads, which taper away from the mixing chamber for pulling the bone cement from the mixing chamber into the delivery chamber. One disadvantage of this system is that the bone cement must have a relatively low viscosity to be pulled by the auger into the delivery chamber. Additionally, the bone cement may remain on the walls of the mixing chamber where the paddle is unable to reach it. Further prior art can be found in <patcit id="pcit0003" dnum="WO8200457A"><text>WO 82/00457</text></patcit>, which constitutes the basis for the preamble portion of claim 1, and <patcit id="pcit0004" dnum="US5729865A"><text>US 5,729,865</text></patcit>.

0012Accordingly, it would be advantageous to provide a bone cement mixing and delivery assembly that includes a mechanism to transfer all of the bone cement from a mixing chamber to an delivery cartridge and to deliver all of the bone cement from the delivery cartridge into the patient.

SUMMARY OF THE INVENTION AND ADVANTAGES

0013A bone cement mixing and delivery assembly according to claim 1 is provided. The bone cement mixing and delivery assembly may be adapted for mixing a powdered copolymer and a liquid monomer to form a bone cement and delivering the bone cement, and include a cartridge having a distal end and a proximal end defining a mixing chamber between the distal end and the proximal end. A lid may be connected to the proximal end and may have an aperture. A transfer mechanism may be connected to the distal end and in sealing engagement with the cartridge. A piston may be connected to the transfer mechanism such that movement of the transfer mechanism extends the piston through the mixing chamber for transferring the bone cement from the mixing chamber to the proximal end. The device may comprise a plunger extending from the piston for forcing the bone cement through the aperture and delivering the bone cement to the patent.

0014A A corresponding method may comprise the steps of filling a chamber having a proximal end with the bone cement, advancing a piston and a plunger in unison within the chamber for transferring the bone cement out of an aperture in the proximal end of the chamber, and advancing the plunger independently of the piston to extend the plunger beyond the piston and into the aperture.

0015The subject invention provides many advantages over conventional systems. First, the bone cement is mixed and dispensed from the same container, thus eliminating the need to manually transfer the bone cement from a mixing vessel to a dispensing device. In addition, the removable handle is released rather than broken off. Thus, cost is reduced, handling is minimized and the introduction of contaminants into the mixture is minimized or eliminated. Furthermore, the compound is not exposed to air, thereby reducing or eliminating exposure of noxious and toxic vapors to surrounding personnel during the surgical operation. Another advantage of the subject invention is that the compound is mixed in an environment evacuated by a vacuum. Thus, the formation of air bubbles is minimized, providing a uniform reaction product and, in turn, producing a stronger bone cement compound.

0016Additionally, the device of the subject invention provides a mechanism for transferring all of the bone cement from the mixing chamber to the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

0017Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

0018<figref idref="f0001">Figure 1</figref> is a perspective view of a first embodiment of a cement mixing and delivery assembly having a transfer mechanism and a removable handle designed according to the present invention;

0019<figref idref="f0002">Figure 2</figref> is an exploded perspective view of the embodiment of <figref idref="f0001">Figure 1</figref>;

0020<figref idref="f0003">Figure 3</figref> is a cross-sectional view of a lid with an aperture having the removable handle extending therethrough designed according to the present invention;

0021<figref idref="f0004">Figure 4</figref> is a cross-sectional view of the embodiment of <figref idref="f0001">Figure 1</figref> shown in a mixing phase;

0022<figref idref="f0005">Figure 5</figref> is an exploded perspective view of the embodiment of <figref idref="f0001">Figure 1</figref> shown in a delivery phase;

0023<figref idref="f0006">Figure 6</figref> is a cross-sectional view of the embodiment of <figref idref="f0001">Figure 1</figref> shown at the start of the transfer stage;

0024<figref idref="f0006">Figure 7</figref> is a cross-sectional view of the embodiment of <figref idref="f0001">Figure 1</figref> shown after complete delivery of the bone cement;

0025<figref idref="f0003">Figure 8</figref> is a perspective view of the lid;

0026<figref idref="f0003">Figure 9</figref> is a perspective view of the transfer mechanism;

0027<figref idref="f0007">Figure 10</figref> is a perspective view of a mixing blade designed according to the present invention;

0028<figref idref="f0007">Figure 11</figref> is a bottom-side perspective view of a piston designed according to the present invention;

0029<figref idref="f0007">Figure 12</figref> is a top-side perspective view of the piston designed according to the present invention;

0030<figref idref="f0007">Figure 13</figref> is a perspective view of a cartridge designed according to the present invention;

0031<figref idref="f0008">Figure 14</figref> is a perspective view of a plunger designed according to the present invention;

0032<figref idref="f0008">Figure 15</figref> is a perspective view of a shaft designed according to the present invention;

0033<figref idref="f0008">Figure 16</figref> is a perspective view of a delivery cartridge designed according to the present invention;

0034<figref idref="f0009">Figure 17</figref> is a cross-sectional view of a second embodiment of a cement mixing and delivery assembly designed according to the present invention;

0035<figref idref="f0009">Figure 18</figref> is a cross-sectional view of a third embodiment of a cement mixing and delivery assembly designed according to the present invention;

0036<figref idref="f0010">Figure 19</figref> is a cross-sectional view of a fourth embodiment of a cement mixing and delivery assembly having multiple plungers and designed according to the present invention;

0037<figref idref="f0011">Figure 20A</figref> is a perspective view of a fifth embodiment of a cement mixing and delivery device designed according to the present invention;

0038<figref idref="f0011">Figure 20B</figref> is a cross-sectional view of the cement mixing and delivery device of <figref idref="f0011">Figure 20</figref> A;

0039<figref idref="f0012">Figure 21A</figref> is a perspective view of a sixth embodiment of a cement mixing and delivery device designed according to the present invention;

0040<figref idref="f0012">Figure 21B</figref> is a cross-sectional view of the cement mixing and delivery device of <figref idref="f0012">Figure 21</figref> A;

0041<figref idref="f0013">Figure 22</figref> is a cross-section view of a seventh embodiment of a cement mixing and delivery device designed according to the present invention; and

0042<figref idref="f0013">Figure 23</figref> is a perspective view of an illustrative example, not forming_part of the present invention, for a removable handle.

DETAILED DESCRIPTION OF THE INVENTION

0043Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a bone cement mixing and delivery assembly for mixing a powdered copolymer and a liquid monomer to form a bone cement and delivering the bone cement is shown generally at 30. In one embodiment, delivery of the bone cement is performed percutaneously. Percutaneous, as used in the medical field, relates to passing or effectuating the bone cement through the skin. The mixing and delivery assembly 30 functions in three phases comprising a mixing phase, a transfer phase, and a delivery phase . All phases are described in detail below with the transfer and delivery phases described first, followed by the mixing phase. Specifically, <figref idref="f0005 f0006">Figures 5-7</figref> and <figref idref="f0009 f0010 f0011 f0012">Figures 17-21</figref> show the assembly 30 during the transfer and delivery phases. <figref idref="f0001 f0002 f0003 f0004">Figures 1-4</figref> illustrate the assembly 30 during the mixing phase.

0044The mixing and delivery assembly 30 includes a cartridge 32 (shown separately in <figref idref="f0007">Figure 13</figref>) having a distal end 34 and a proximal end 36 and defining a chamber 38 between the distal end 34 and the proximal end 36, as shown in <figref idref="f0004">Figures 4</figref>, <figref idref="f0006">6</figref>, and <figref idref="f0007">13</figref>. An external portion of the cartridge 32 adjacent the distal end 34 further includes male threads 42. In the preferred embodiment, the chamber 38 is a mixing chamber 40 for receiving the liquid monomer and the powdered copolymer to form the bone cement. The chamber 38 may, however, receive premixed bone cement, in which case the assembly 30 is used only to deliver the premixed bone cement to the patient.

0045Alternatively, the chamber <b>38</b> may be packaged with the powdered copolymer. Thus, prior to use, only the liquid monomer is added.

0046A lid <b>44</b> is connected to the proximal end <b>36</b> and it has a first aperture <b>46.</b> The lid <b>44</b> sealingly engages the proximal end <b>36.</b> In the preferred embodiment, the lid <b>44</b> has threads for engaging corresponding threads on the proximal end <b>36</b> as shown in <figref idref="f0002 f0003 f0004 f0005 f0006">Figures 2-7</figref>. The lid <b>44</b> also has a vent <b>48</b> connected to the lid <b>44</b> for allowing a vacuum (not shown) to be attached to the vent <b>48</b> with a vacuum attachment <b>76</b> for removing gas particles from the chamber <b>38.</b> The vacuum may be any device capable of applying a pressure differential, as is known in the art, for removing gas particles from the mixing chamber <b>40.</b> Removal of the gas creates a stronger cement. Also the vacuum assists in the removal of obnoxious and potentially harmful gases produced during mixing. A filter <b>50</b> may also be disposed within the vent <b>48</b> for filtering the gas particles.

0047The mixing and delivery assembly <b>30</b> may further include a cooling chamber <b>52</b> positioned adjacent the mixing chamber <b>40</b> for receiving a cooling fluid (not shown) to cool the mixing chamber <b>40.</b> The cooling chamber <b>52</b> is capable of receiving any cooling fluid as is known in the art. As the liquid monomer and powder copolymer are mixed, an exothermic chemical reaction occurs. Illustrative examples of such a cooling fluid include ice inserted into the cooling chamber <b>52</b> or chemicals which produce an endothermic reaction for cooling the chamber <b>38.</b> Alternately, the cooling chamber <b>52</b> could be annular and connected to a cold air or water supply for passing cold air or water through the cooling chamber <b>52.</b> The bone cement remains useable for a longer period of time if the heat from the exothermic reaction is dissipated.

0048A transfer mechanism <b>54</b> threads onto the distal end <b>34,</b> as shown in <figref idref="f0001">Figures 1</figref>,<figref idref="f0002">2</figref>, <figref idref="f0004 f0005 f0006">4-7</figref>, and <figref idref="f0009 f0010 f0011 f0012">17-21</figref>. The transfer mechanism <b>54</b> includes a cap <b>56.</b> The cap <b>56</b> has female threads <b>58</b> for engaging the male threads <b>42</b> of the distal end <b>34.</b> The cap <b>56,</b> as shown in <figref idref="f0003">Figure 9</figref>, further includes a stem <b>62</b> extending from the cap <b>56.</b> A piston <b>64</b> is rotatably supported by the stem <b>62</b> and housed within the cartridge <b>32.</b> The piston <b>64</b> has a perimeter which extends to an inner wall of the chamber <b>38.</b> The piston <b>64</b> is shown separately in <figref idref="f0007">Figures 11 and 12</figref>. The piston <b>64</b> also has a piston seal <b>65</b> between the piston <b>64</b> and the chamber <b>38</b> for preventing bone cement from flowing therebetween. Preferably, the piston seal <b>65</b> comprises an O-ring.

0049The transfer mechanism <b>54</b> has a first advancement mechanism <b>68</b> and a second advancement mechanism <b>70.</b> The first advancement mechanism <b>54</b> is for use in the transfer phase to advance the piston <b>64</b> through the chamber <b>38</b> and transfer the bone cement from the chamber <b>38</b> and out the aperture <b>46.</b> The first advancement mechanism <b>68</b> includes a pin system <b>72</b> interconnecting the piston <b>64</b> and the stem <b>62</b> for preventing rotation of the piston <b>64</b> relative to the stem <b>62</b> until the piston <b>64</b> reaches a stop position <b>74,</b> shown in <figref idref="f0006">Figure 6</figref>. The stop position <b>74</b> is defined by a channel <b>66</b> in the chamber <b>38</b> being adjacent the piston <b>64.</b> The first advancement mechanism <b>68</b> further includes a disconnect system <b>78</b> disconnecting the female threads <b>58</b> from the male threads <b>42,</b> as shown in <figref idref="f0006">Figure 7</figref>. After the female threads <b>58</b> and the male threads <b>42</b> are disconnected, the cap <b>56</b> can be rotated relative to the cartridge <b>32</b> without moving or rotating the piston <b>64.</b>

0050In the preferred embodiment, the female threads <b>58</b> are formed as a plurality of circumferential segments <b>60.</b> The plurality of circumferential segments <b>60</b> are connected to the transfer mechanism <b>54</b> to move axially along the male threads <b>42</b> thereby advancing the piston <b>64.</b> The cartridge <b>32</b> includes an annular recess <b>82</b> adjacent the male threads <b>42.</b> A first biasing device <b>84</b> moves the segments, into the annular recess <b>82</b> once the piston <b>64</b> reaches the stop position <b>74.</b> Preferably, the circumferential segments <b>60</b> are divided into sections and each section has a nipple <b>86</b> for engaging the first biasing device <b>84,</b> as shown in <figref idref="f0002">Figure 2</figref>. Additionally, the plurality of circumferential segments <b>60</b> may only encircle a portion of the threaded portion <b>40.</b> Preferably, the first biasing device <b>84</b> is a metal spring band which collapses the plurality of circumferential segments <b>60</b> into the annular recess <b>82.</b> As the circumferential segments <b>60</b> reach the end of the male threads <b>42,</b> the first biasing device <b>84</b> forces the plurality of circumferential segments <b>60</b> into the annular recess <b>82.</b> As the circumferential segments <b>60</b> are forced into the annular recess <b>82,</b> the circumferential segments <b>60</b> disengage from the transfer mechanism <b>54</b> which disconnects from the piston <b>64.</b> When the circumferential segments <b>60</b> have entered the annular recess <b>82,</b> the transfer stage is completed and the bone cement has been transferred from the chamber <b>38</b> and out the aperture <b>46.</b> The first biasing device <b>84</b> and the annular recess <b>82</b> prevent the first advancement mechanism <b>68</b> from being able to back down the threaded portion <b>42.</b> In other words, the first biasing device <b>84</b> allows the mixing and delivery assembly <b>30</b> to be used for a single application.

0051The assembly <b>30</b> also includes a plunger <b>88</b> movable relative to the piston <b>64</b> for extending from the piston <b>64</b> and into the aperture <b>46</b> for forcing the bone cement through the aperture <b>46.</b> The extending of the plunger <b>88</b> from the piston <b>64</b> through the aperture <b>46</b> is the beginning of the delivery phase. The plunger <b>88</b> has a groove <b>90</b> and the stem <b>62</b> has a tongue <b>92</b> for interconnecting the plunger <b>88</b> to the stem <b>62.</b> The interconnection of the tongue <b>92</b> and the groove <b>90</b> allows the plunger <b>88</b> to rotate with the stem <b>62</b> and to move axially relative to the stem <b>62</b> in the delivery phase via threaded interaction between the plunger <b>88</b> and the piston <b>64.</b>

0052The pin system <b>72</b> includes a pin <b>94</b> disposed radially to interconnect the stem <b>62</b> and the piston <b>64.</b> The pin <b>94</b> has a head <b>95</b> and a tail <b>97</b> and the head <b>95</b> is larger than the tail <b>97.</b> A second biasing device <b>96,</b> comprising a spring around the tail <b>97,</b> urges the pin <b>94</b> radially outwardly against the cartridge <b>32.</b> The cartridge <b>32</b> has the channel <b>66</b> adjacent the proximal end <b>36</b> for receiving the head <b>95.</b> As the first advancement mechanism <b>68</b> moves the piston <b>64</b> through the chamber <b>38,</b> the spring is compressed due to the head <b>95</b> engaging the inner wall of the chamber <b>38.</b> When the piston <b>64</b> reaches the stop position <b>74,</b> the pin <b>94</b> is received by the channel <b>66</b> and the spring forces the pin <b>94</b> outward. Once this happens, the pin <b>94</b> no longer engages the stem <b>65</b> and only engages the chamber <b>38</b> and the piston <b>64.</b>

0053The second advancement mechanism <b>70</b> includes threads <b>100</b> on the plunger <b>88</b> that engage threads <b>101</b> inside the piston <b>64.</b> The second advancement mechanism <b>70</b> advances the plunger <b>88</b> from the piston <b>64</b> during the delivery phase. A plunger seal <b>103</b> is disposed between the plunger <b>88</b> and the piston <b>64</b> to prevent bone cement from flowing therebetween during the mixing and transfer phases. The tongue <b>92</b> and the groove <b>90</b> impart the continued rotation of the cap <b>56</b> to the plunger <b>88.</b> The plunger <b>88</b> thereafter threadably engages the piston <b>64</b> such that the plunger <b>88</b> extends from the piston <b>64.</b> Once the piston <b>64</b> has reached the stop position <b>74,</b> the plunger <b>88</b> moves independently of the piston <b>64</b> and the piston <b>64</b> acts as a nut as the cap <b>56</b> is rotated.

0054Alternately, and as shown in <figref idref="f0009">Figures 17 and 18</figref>, the second advancement mechanism <b>70</b> may include a rack <b>102</b> connected to the plunger <b>88</b> and a gear <b>104</b> engaging the rack <b>102</b> to advance the plunger <b>88</b> during the delivery phase. The gear <b>104</b> may be either a pinion gear <b>106</b> (<figref idref="f0009">Figure 17</figref>) or a worm gear <b>108</b> (<figref idref="f0009">Figure 18</figref>). A rod <b>110</b> is connected to the gear <b>104</b> and extends through the transfer mechanism <b>54</b> for actuating the gear <b>104</b> manually or by a drive (not shown). The rod <b>110</b> is rotated causing the gear <b>104</b> to rotate causing the rack <b>102</b> to move linearly. Movement of the rack <b>102</b> extends the plunger <b>88</b> from the piston <b>64</b> and continues to deliver the bone cement through the aperture <b>46.</b>

0055The assembly <b>30</b> further includes a delivery cartridge <b>112</b> having a cartridge end <b>114</b> connected to the aperture <b>46</b> of the lid <b>44</b> and extending to an open end <b>116.</b> The delivery cartridge <b>112</b> (shown separately in <figref idref="f0008">Figure 16</figref>) has a smaller diameter than the mixing chamber <b>40</b> and the plunger <b>88</b> has a smaller cross-section which allows the plunger <b>88</b> to extend through the aperture <b>46</b> and into the delivery cartridge <b>112.</b> As the delivery cartridge <b>112</b> receives the plunger <b>88,</b> the bone cement is forced through the delivery cartridge <b>112.</b> The delivery cartridge <b>112</b> may also include cooling chambers <b>52</b> as discussed above for surrounding the mixing chamber <b>40.</b> For example, a water-based gel may be inserted into the cooling chamber <b>52</b> around the delivery cartridge <b>112</b> and cooled. The cooled delivery cartridge <b>112</b> allows the bone cement to be available for use for longer periods of time. The delivery cartridge <b>112</b> may be permanently or removably connected to the lid <b>44.</b> Alternate embodiments may have the delivery cartridge <b>112</b> connected to the opposite end of a removable handle <b>120.</b>

0056The subject invention may also be utilized with more than one delivery cartridge <b>112,</b> as shown in <figref idref="f0010">Figure 19</figref>. Multiple delivery cartridges <b>112</b> require a plurality of plungers <b>88</b> corresponding to each of the delivery cartridges <b>112.</b> For instance, two plungers <b>88</b> may extend from the piston <b>64.</b> The plungers <b>88</b> would be configured as described above with each plunger <b>88</b> engaging the second advancement mechanism <b>70.</b> Therefore, actuation of the second advancement mechanism <b>70</b> advances, both plungers <b>88.</b> Alternately, the plungers <b>88</b> could have individual second advancement mechanisms such as the worm gear <b>108</b> or pinion gear <b>106</b> type of second advancement mechanisms <b>70.</b> For percutaneous delivery, a flexible extension tube (not shown) is removable coupled to the open end <b>116.</b> A needle having a handle (not shown) is coupled to the extension tube for injection through the skin and into the patient.

0057In one embodiment, the mixing and delivery assembly <b>30</b> also includes at least one indicator <b>118</b> disposed on the transfer mechanism <b>54</b> or rod <b>110</b> indicating an amount of the bone cement to be delivered into the patient upon rotation of the transfer mechanism <b>54</b> and the second advancement mechanism <b>70.</b> For instance, the indicator <b>118</b> on the transfer mechanism <b>54</b> may represent a quarter of a turn. The quarter of a turn may further represent two cubic centimeters of bone cement to be delivered into the patient. The indicators allow medical personnel to easily and efficiently deliver predetermined amounts of the bone cement to the patient. In another embodiment, the delivery cartridge <b>112</b> includes markings indicative of the amount of bone cement delivered.

0058The assembly <b>30</b> of the subject invention can be used with a method of delivering the bone cement. The method includes the steps of filling the chamber <b>38</b> with the bone cement and sealing the chamber <b>38</b> by connecting the lid <b>44</b> to the proximal end <b>36.</b> The preferred method includes disposing the liquid monomer and the powdered copolymer into the chamber and agitating the liquid monomer and the powdered copolymer to form the bone cement as described below. However, the subject invention is particularly useful with premixed bone cement. Once the mixed bone cement is in chamber <b>38,</b> the next step is actuating the transfer mechanism <b>54</b> to advance the first advancement mechanism <b>68.</b> Advancing the first advancement mechanism <b>68</b> includes advancing the piston <b>64</b> and the plunger <b>88</b> in unison for transferring the bone cement from the chamber <b>38</b> to the proximal end <b>36.</b> In the preferred embodiment, actuation of the first advancement mechanism <b>68</b> begins by rotating the transfer mechanism <b>54.</b> Rotation of the cap <b>56</b> causes the plurality of circumferential segments <b>60</b> to move along male threads <b>42.</b> When the plurality of circumferential segments <b>60</b> reaches the annular recess <b>82,</b> the first biasing device <b>84</b> forces the plurality of circumferential segments <b>60</b> radially inward and into the annular recess <b>82</b> thereby separating the plurality of circumferential segments <b>60</b> from the cap <b>56.</b>

0059The method is then characterized by actuating the second advancement mechanism <b>70</b> and advancing the plunger <b>88</b> independently of the piston <b>64</b> to extend the plunger <b>88</b> beyond the piston <b>64</b> thereby delivering the bone cement into the patient. Specifically, in a preferred embodiment, once the plurality of circumferential segments <b>60</b> is recessed, the pin <b>94</b> engages the channel <b>66</b> in the mixing chamber <b>40</b> which fixes the position of the piston <b>64.</b> Continued rotation of the cap <b>56</b> causes the plunger <b>88</b> to rotate within the piston <b>64</b> and extend therefrom. The cap <b>56</b> is rotated until the plunger <b>88</b> has moved into the delivery cartridge <b>112</b> to force the bone cement completely from the mixing chamber <b>40.</b>

0060In alternate embodiments, the second advancement mechanism <b>70</b> has the rod <b>110</b> extending from the cartridge <b>32</b> and engaging the gear <b>104.</b> After the piston <b>64</b> is locked in place, the rod <b>110</b> is rotated causing the plunger <b>88</b> to extend from the piston <b>64.</b> Alternate aspects of the assembly <b>30,</b> as described above, further include the steps of venting the chamber <b>38,</b> removing gas particles from the chamber <b>38,</b> and filtering the gas particles as the gas particles are removed from the chamber <b>38.</b>

0061The assembly <b>30</b> preferably is further used to mix the liquid monomer and powder copolymer in the mixing chamber <b>40,</b> as shown in <figref idref="f0001 f0002 f0003 f0004">Figures 1-4</figref>. In the mixing phase, the assembly <b>30</b> includes a removable handle <b>120</b> extending through the aperture <b>46</b> and having a first end <b>122</b> and a second end <b>124</b> defining a hollow cavity <b>126</b> therebetween. Other embodiments may include the removable handle <b>120</b> extending through the cap <b>56.</b> The removable handle <b>120</b> may also be used to move the plunger <b>88</b> through the aperture <b>46.</b> One such removable handle <b>120</b> is illustrated in <figref idref="f0013">Figure 22</figref>. The removable handle <b>120</b> includes a pivot <b>121</b> for engaging a cap stop <b>123.</b> While in the transfer phase, the removable handle <b>120</b> pivots and is at a right angle with the plunger <b>88.</b> The removable handle <b>120</b> can be used to rotate the cap <b>56</b> during this stage. During the delivery phase, the removable handle <b>120</b> is pivoted and coextensive with said plunger <b>88.</b> Rotation of the removable handle <b>120</b> extends the plunger <b>88</b> from the piston <b>64.</b>

0062A mixing blade <b>128</b> (shown separately in <figref idref="f0007">Figure 10</figref>) has a bore <b>130</b> for receiving the first end <b>122</b> of the removable handle <b>120.</b> The second end <b>124</b> of the removable handle <b>120</b> allows a knob <b>132</b> to be attached for rotating and moving the mixing blade <b>128</b> through the mixing chamber <b>40.</b> The mixing blade <b>128</b> may be any blade used for mixing, but is preferably a circular blade or a circular disc that is able to slide within the mixing chamber <b>40.</b> The mixing blade <b>128</b> has a circumference which extends to the inner wall of the mixing chamber <b>40,</b> while still allowing for movement of the mixing blade <b>128.</b> The mixing blade <b>128</b> may further include slots <b>134</b> for increasing the efficiency of the mixing. A shaft <b>136</b> (shown separately in <figref idref="f0008">Figure 15</figref>) is disposed within the hollow cavity <b>126</b> and has a blade attachment end <b>138</b> with projections <b>140</b> extending from the first end <b>122.</b> A shaft seal <b>141</b> is disposed between the shaft <b>136</b> and the removable handle <b>120</b> for preventing cement from flowing therebetween.

0063A quick-release bayonet-type connector <b>142</b> is located between the mixing blade <b>128</b> and the shaft <b>136</b> such that the mixing blade <b>128</b> is releasably connected to the removable handle <b>120.</b> A release button <b>144</b> engages the shaft <b>136</b> and is movable between a locked position and an unlocked position. The quick-release connector <b>142</b> further includes flanges <b>146</b> extending inward from the bore <b>130</b> of the mixing blade <b>128</b> and a pair of flange recesses <b>148</b> disposed within the first end <b>122</b> of the removable handle <b>120.</b> In the unlocked position, the projections <b>140</b> are offset from the flange recesses <b>148</b> such that the flange <b>146</b> can be received by the flange recess <b>148.</b> Movement of the release button <b>144</b> causes the shaft <b>136</b> to rotate while the removable handle <b>120</b> remains still. The shaft <b>136</b> rotates causing the projections <b>140</b> to engage the flanges <b>146</b> and force the flanges <b>146</b> into the flange recess <b>148.</b> Once the release button <b>144</b> is in the locked position, the mixing blade <b>54</b> is locked to the removable handle <b>120</b>. The removable handle <b>120</b> is manipulated manually or by a motor (not shown) to move the mixing blade <b>54</b> through the mixing chamber <b>40</b> and mix the cement components. The removable handle <b>120</b> is of sufficient length to extend the mixing blade <b>128</b> through the entire length of the mixing chamber <b>40</b> and rotate the mixing blade <b>128</b> to ensure complete mixing.

0064An illustrative example, not forming part of the present invention, quick-release connector <b>142</b> is shown in <figref idref="f0013">Figure 23</figref>. A collapsible ball <b>143</b> is connected to the first end <b>122</b> of the removable handle <b>120</b>. When the release button <b>144</b> is in the unlocked position, the collapsible ball <b>143</b> is collapsed and can be inserted into the bore <b>130.</b> The release button <b>143</b> is moved to the locked position and the collapsible ball <b>143</b> engages the bore <b>130</b> thereby locking the mixing blade <b>128</b> to the removable handle <b>120</b>.

0065The assembly <b>30</b>, as utilized in the mixing phase, includes a method of mixing the powdered copolymer and the liquid monomer to form the bone cement. The method includes the steps of disposing the powdered copolymer and the liquid monomer into the mixing chamber <b>40</b> and connecting the lid <b>44</b> to the proximal end <b>36</b> to seal the mixing chamber <b>40</b> having the mixing blade <b>128</b> disposed within the mixing chamber <b>40.</b> Preferably, the removable handle <b>120</b> is inserted through the aperture <b>46</b> of the lid <b>44</b> while the lid <b>44</b> is not connected to the cartridge <b>32</b>. However, the quick-release connector <b>142</b> allows for the mixing blade <b>128</b> to be initially within the mixing chamber <b>40</b> and the lid <b>44</b> attached when inserting the removable handle <b>120</b> through the aperture <b>46</b>. Additionally, the two components may be added with the lid <b>44</b> already connected and the mixing blade <b>128</b> disposed within the mixing chamber <b>40.</b> The removable handle <b>120</b> is manipulated moving the mixing blade <b>128</b> and agitating the powdered copolymer and the liquid monomer to form the bone cement. As the components are mixed together, a chemical reaction ensues, producing a gas that may be harmful if inhaled by the medical personnel. The vacuum is applied to the vent <b>48</b> to remove gas particles from the mixing chamber <b>40</b> preventing the gas from being inhaled. The removal of the gas also ensures that the bone cement will be formed without gas bubbles providing a stronger cement. Additionally, the filter <b>50</b> may be utilized for filtering the gas particles as the gas particles are being removed from the mixing chamber <b>40.</b>

0066Once mixing is complete, the release button <b>144</b> is moved to the unlocked position thereby releasing the mixing blade <b>128</b> from the quick-release connector <b>142</b> such that the removable handle <b>120</b> is removable through the aperture <b>46</b> and the mixing blade <b>128</b> remains in the mixing chamber <b>40.</b> When the release button <b>144</b> is moved to the unlocked position, the shaft <b>136</b> is rotated causing the projections <b>140</b> of the blade attachment end <b>138</b> to be offset from the flanges <b>146</b> of the bore <b>130.</b> The removable handle <b>120</b> is then removed from the bore <b>130</b> of the mixing blade <b>128</b> and through the aperture <b>46.</b> Since the mixing blade <b>128</b> is released without having to break the removable handle <b>120,</b> the bone cement does not become contaminated with fragments.

0067<figref idref="f0011">Figures 20A &amp; B</figref> illustrate another embodiment of the cement mixing and delivery assembly <b>30.</b> The first advancement mechanism <b>54</b> is actuated by rotating the cap <b>56</b> to move the piston <b>64</b> through the mixing chamber <b>40</b> along the male threads <b>42.</b> The assembly <b>30</b> allows the removable handle <b>120</b> to remain in the mixing chamber <b>40</b> while the second advancement mechanism <b>70</b> is operated. The second advancement mechanism <b>70</b> includes the plunger <b>88</b> extending through the removable handle <b>120</b> and through the mixing blade <b>128.</b> The delivery cartridge <b>112</b> extends from the lid <b>44</b> while the plunger <b>88</b> and the removable handle <b>120</b> extend through the cap <b>56.</b> The second advancement mechanism <b>70</b> is actuated by forcing the plunger <b>88</b> through the delivery cartridge <b>112</b> to deliver the bone cement by applying a force to the knob <b>132</b> of the removable handle <b>120.</b> In this embodiment, the mixing blade <b>128</b> has tapered slots <b>134</b> to ensure better mixing and to assist in transferring the bone cement.

0068<figref idref="f0012">Figures 21A &amp; B</figref> illustrate yet another embodiment of the cement mixing and delivery assembly <b>30.</b> The mixing handle <b>120</b> and the delivery cartridge <b>112</b> both extend from the lid <b>44.</b> The first advancement mechanism <b>54</b> is actuated by rotating the cap <b>56</b> to move the piston <b>64</b> through the mixing chamber <b>40</b> along the male threads <b>42.</b> The second advancement mechanism <b>70</b> includes the rod <b>110</b> extending from the cartridge <b>32</b> and the gear <b>104</b> engaging the plunger <b>88.</b> When the rod <b>110</b> is rotated, the plunger <b>88</b> moves linearly through the mixing blade <b>128</b> and through the delivery cartridge <b>112</b> to deliver the bone cement.

0069Obviously, many modifications and variations of the present invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims.