Method and injection system for bone tissue implant

Abstract

An implant injection system and method for introducing a bone implant material into a patient's bone to serve as an anchor or to fill a void in the bone. The system and method provide a quantity of meltable material which is melted in situ so that the melted material can flow and diffuse into, and be anchored to, the cancellous bone portion beneath the cortical bone layer. The flowing of the bone implant material can be accomplished by a heater located at the distal end of the implant injection system. The implant material may be provided in multiple layers with an inner layer having a lower flowing temperature than the outer layers. There can also be a looped suture that passes though the meltable material, with the free ends of the suture extending outwardly to be tied to soft tissue to affix the soft tissue to the bone.

Claims

1. An implant injection system for implanting an implant material into bone, the implant injection system comprising: a shaft having a distal end and a proximal end; an implant material having a non-flowable state and a flowable state, wherein the implant material forms the distal end of the shaft when the implant material is in the non-flowable state; a suture extending through the implant material when the implant material is in the non-flowable state; and a heater disposed proximate to the implant material for heating the implant material to its flowable state, whereby the implant material separates from the distal end of the shaft and flows into the bone.

2. The implant injection system of claim 1 wherein the bone is a bone of a mammal.

3. The implant injection system of claim 1 wherein the heater is an electrical resistance heater.

4. The implant injection system of claim 3 wherein the implant injection system further comprises a source of electricity for activating the electrical resistance heater.

5. The implant injection system of claim 4 wherein the source of electricity is a battery located within the shaft.

6. The implant injection system of claim 1 wherein the heater employs a quantity of heated fluid.

7. The implant injection system of claim 6 wherein the heated fluid is heated water.

8. The implant injection system of claim 6 wherein the heated fluid is heated air.

9. The implant injection system of claim 1 wherein the implant material has a flowing temperature of about 60 degrees Centigrade.

10. The implant injection system of claim 1 wherein the implant material is polycaprolactone.

11. The implant injection system of claim 1 wherein the implant material is a polymer.

12. The implant injection system of claim 1 wherein the suture comprises a distal portion and a proximal portion, wherein the distal portion of the suture is passed through the implant material and the proximal portion of the suture comprises two free ends of suture.

13. The implant injection system of claim 12 wherein the two free ends of suture are configured to attach soft tissue to bone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A-1C are schematic views illustrating an implant injection system formed in accordance with the present invention and showing a method for implanting implant material into the cancellous bone tissue of a patient;

(2) FIGS. 2A-2E are further schematic views illustrating the distal end of the implant injection system of FIGS. 1A-1C and showing the method of implanting implant material into the cancellous bone tissue of a patient;

(3) FIGS. 3A and 3B are schematic views showing an alternative exemplary embodiment of an implant injection system formed in accordance with the present invention and showing a method of use for implanting an implant material into the cancellous bone tissue of a patient;

(4) FIG. 4 is an exploded schematic view of another implant injection system of the present invention that can be used to melt and introduce a polymer into the bone of a patient;

(5) FIG. 5 is a perspective view of the assembled implant injection system of FIG. 4;

(6) FIG. 6 is a perspective view of the implant injection system of FIG. 4 and illustrating its use in injecting a flowable melted polymer material into the bone of a patient;

(7) FIGS. 7A and 7B are schematic views of an electrical circuit usable with the embodiment of FIG. 4;

(8) FIGS. 8A-8G are schematic views illustrating a method of loading an applicator tip with a material, such as a bone cement, to ready the applicator for injecting the material into the bone of a patient; and

(9) FIG. 8H is a schematic view showing an additional construction formed in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) Referring now to FIGS. 1A-1C, there is shown schematic views illustrating an implant injection system 10 formed in accordance with the present invention and showing the steps taken to carry out a method of the present invention. As can be seen in FIG. 1A, the implant injection system 10 is positioned in close proximity to a bone 12 of a patient, and the implant injection system 10 includes a handle 14 and a shaft 16 extending therefrom. In this exemplary embodiment, a small resistance heater 18 is located at the distal end of the shaft 16.

(11) Bone implant material 20 is positioned at the distal end of the implant injection system 10 and a suture 22 is looped through that bone implant material 20 and the free ends 24 of the suture 22 extend from that bone implant material 20 proximally towards the handle 14.

(12) Moving on to the step shown in FIG. 1B, the shaft 16 has pierced the cortical bone layer 26 of the bone 12 and the distal end of the shaft 16 is located in the cancellous bone 28.

(13) In the step of FIG. 1C, the implant injection system 10 has been withdrawn from the bone 12 of the patient and the bone implant material 20 separated therefrom such that the bone implant material 20 remains in the cancellous bone 28. To reach the step of FIG. 1C, the bone implant material 20 has been heated by the resistance heater 18 to melt the bone implant material 20 and allow the implant injection system 10 to be pulled clear of the bone implant material 20. The bone implant material 20 itself has melted and spread through the interstices of the cancellous bone 28 so that the bone implant material 20 is firmly affixed to the cancellous bone 28, with the free ends 24 of the suture 22 available for use in securing soft tissue to the cortical bone layer 26.

(14) It should be appreciated that in one form of the invention, the bone implant material 20 is secured to the distal end of shaft 16, adjacent to the resistance heater 18 disposed at the distal end of shaft 16, so that bone implant material 20 essentially forms, in its pre-heated state, the distal end of shaft 16; and so that bone implant material 20 is carried into cancellous bone 28 by shaft 16, whereupon activation of resistance heater 18 causes bone implant material 20 to flow off the distal end of shaft 16 and into the interstices of cancellous bone 28. Thus, in one form of the invention, the heated bone implant material 20 is set at the distal end of shaft 16 and, when heated by resistance heater 18, simply flows off the shaft and into the interstices of the cancellous bone 28, whereafter it sets when cooled to body temperature. In another form of the invention, the bone implant material 20 may be positioned within a syringe chamber (not shown) disposed at the distal end of shaft 16, and the heated bone implant material may be ejected, under force, out of the syringe chamber and into the interstices of cancellous bone 28, whereafter it will set when cooled to body temperature.

(15) In the method shown in FIGS. 1A-1C, the heater 18 has been described in the exemplary embodiment to be an electrical resistance heater, however, it may be seen that other types of heaters can be used instead of a resistance heater in any of the embodiments described herein, including a heater employing a heated fluid, such as heated water or heated air.

(16) In addition, in this embodiment and in subsequent applicable embodiments, the meltable implant material is one having a low flowing temperature such as polycaprolactone (PCL) which has a flowing point of about 60 degrees Centigrade so that necrotic damage to the bone is prevented. When that material is thereafter cooled, it hardens within the bone at the desired location and becomes an effective anchor for a suture or fills a void in the bone.

(17) Accordingly, as an alternative to the use of a resistance heater, the implant bone material 20, located in one embodiment at the distal end of an implant instrument, can be placed into a heated chamber or bath so that the implant bone material softens to a moldable state and then can be emplaced into the cancellous bone.

(18) Turning now to FIGS. 2A-2E, there is shown a series of steps further illustrating the use of the present implant injection system 10 in carrying out the present method of emplacing the bone implant material 20. As can be seen, in the step of FIG. 2A, a hole 30 has been made in the bone 12 of the patient that passes through the cortical bone layer 26 and extends into the cancellous bone 28. As with the embodiment of FIGS. 1A-1C, at the end of the shaft 16, there is affixed the bone implant material 20 and which has the suture 22 passing through the bone implant material 20, with the free ends 24 of the suture 22 extending outwardly therefrom. The resistance heater 18 is also located at the distal end of the shaft 16 so that the resistance heater 18 can heat the bone implant material 20 to its melt point to cause it to be flowable.

(19) In the step of FIG. 2B, the distal end of the shaft 16 has been introduced into the hole 30 so that the bone implant material 20 passes through the cortical bone layer 26 and into the cancellous bone 28.

(20) In the step of FIG. 2C, the resistance heater 18 has been activated and the bone implant material 20 has melted and spread into the cancellous bone 28, thereby forming a mass having a larger diameter than the diameter of the hole 30. In the step of FIG. 2D, the shaft 16 has been retracted, leaving the melted bone implant material 20 to re-solidify at body temperature within the cancellous bone 28, with the suture 22 passing through the bone implant material 20 so that the suture 22 is anchored within the bone 12.

(21) Finally, in the step of FIG. 2E, there can be seen the re-hardened bone implant material 20 positioned within the cancellous bone 28, with the free ends 24 of the suture 22 tied together, encircling soft tissue 32, so that the soft tissue 32 is affixed to the cortical bone layer 26.

(22) Turning next to FIGS. 3A and 3B, there is shown steps of an alternative embodiment of an implant injection system 34 of the present invention, wherein the distal end of the shaft 36 is in position proximate to the bone 38 of the patient. In this embodiment, again a hole 40 has been drilled in the bone 38 and passes through the cortical bone layer 42 and enters into the cancellous bone 44.

(23) In this exemplary embodiment, however, at the distal end of the shaft 36 there is a multi-layer bone implant material 46. As can be seen in FIGS. 3A and 3B, the bone implant material 46 comprises a distal region 48, an intermediate region 50 and a proximal region 52. The distal region 48 and proximal region 52 comprise a high melt temperature polymer while the intermediate region 50 comprises a lower melt temperature polymer. In the exemplary embodiment, the polymer used in the distal region 48 and the proximal region 52 can be the same material.

(24) Again, a resistance heater 54 is provided to carry out the melt step of the present invention. The suture 56 passes through the distal region 48 of the bone implant material and has its free ends 58 external of the bone 38 of the patient.

(25) As such, turning now to FIG. 3B, again, as described with respect to FIGS. 1A-1C and 2A-2E, the resistance heater 54 has heated the bone implant material 46 and has been retracted from the cortical bone layer 42, leaving the bone implant material 46 in the cancellous bone 44 of the patient.

(26) In this embodiment, however, the intermediate region 50, being formed out of a polymer having a lower melt temperature than the polymers of the distal region 48 and the proximal region 52, has melted and infused into the cancellous bone 44 of the patient. The polymer or polymers of the distal region 48 and proximal region 52, being of a higher melt point, have not melted and remain intact in situ within the cancellous bone 44 of the patient.

(27) In this form of the invention, proximal region 52 can make a simple friction fit with the distal end of shaft 16, such that bone implant material 46 can disconnect from the distal end of shaft 16 after bone implant material 46 has been positioned within bone 38.

(28) The suture 56 is firmly anchored to the distal region 48 and has its free ends 58 extending outwardly from the bone 38 of the patient for attachment of an object (such as soft tissue) to the bone 38 of the patient.

(29) Alternatively, if desired, proximal region 52 of bone implant material 46 may be omitted and intermediate region 50 may be connected to the distal end of shaft 16, whereupon bone implant material 46 will detach from the shaft when the bone implant material is heated to a flowable state.

(30) Turning now to FIG. 4, there is shown an exploded, schematic view of a still further implant injection system 60 of the present invention that can be used to melt and introduce a polymer bone implant material into the bone of a patient. As can be seen in FIG. 4, the implant injection system 60 comprises an insulated container 62 having a cylindrical opening 64 extending therethrough, and the implant injection system 60 has a distal end 66 and a proximal end 68. A heater 70 is provided proximate the distal end 66 of the container 62 and, in the exemplary embodiment, the heater 70 may be an electrical resistor. A nozzle 72 is also located at the distal end 66 of the container 62 (and the implant injection system 60 itself). A flange 74 is provided at the proximal end 68 of the container 62 and the purpose of the flange 74 will be later explained.

(31) Within the cylindrical opening 64 of container 62, there is located a meltable polymer capsule (which may also be referred to as a cartridge or block or plug, etc.) 76. A plunger 78 interfits into the cylindrical opening 64 and is axially movable within the cylindrical opening 64. The plunger 78 also has a recessed opening 80 and a closed proximal end flange 82, and a battery 84 is interfitted into the recessed opening 80 that is used to power the heater 70. At the distal end 86 of the plunger 78, there is provided an insulator 88 that closes the distal end 86 of the plunger 78 and can serve to retain and insulate the battery 84 within the recessed opening 80 of the plunger 78.

(32) As is conventional, there is suitable wiring to electrically connect the battery 84 to the heater 70 and a switch, not shown, that can be used to complete the circuit between the battery 84 and the heater 70 to activate the heater 70 at the will of the user. Typical switches that can be used include manual switches or pressure-actuated switches that complete the electrical circuit when the plunger 78 is pushed inwardly toward the distal end 66 of the container 62.

(33) In FIG. 5, there is a perspective view of the complete implant injection system 60 assembled from the components of FIG. 4. Accordingly, the user can hold the implant injection system 60 by holding the flange 74 and then depressing the plunger 78 inwardly to operate the implant injection system 60.

(34) In FIG. 6, taken along with FIGS. 4 and 5, it can be seen that the polymer capsule 76 of FIG. 4 has been melted by the activated heater 70 such that the polymer emerges as a flowable, melted polymer material 90 out of the nozzle 72 that may be used to form an anchor in, and/or to fill a void in, a bony structure.

(35) Note that with the construction of FIGS. 4-6, the polymer is melted by heater 70 at the distal end of implant injection system 60, adjacent to exit nozzle 72. Thus, the melted polymer only needs to travel a short distance to its implant site, whereupon it re-hardens within the bone.

(36) Turning next to FIGS. 7A and 7B, there is shown a schematic view of a typical electrical circuit that can be used with the embodiment of FIG. 4. In FIG. 7A, the circuit is open since the manual switch 92 is in its open position. As such, the battery 84 is not connected to the heater 70 so the polymer capsule 76 remains intact (i.e., in solid form). An arrow F indicates the force exerted on the polymer capsule 76 as the plunger 78 (FIG. 4) is pushed forward by the user.

(37) In FIG. 7B, the circuit has been closed since the manual switch 92 has been moved to its closed position and therefore the electrical energy of the battery 84 passes to the heater 70 that heats the polymer to a temperature exceeding its flowing temperature. The force F can now be exerted on the plunger 78 (FIG. 4) and the flowable, melted polymer 90 emerges from the implant device 60 (for subsequent re-hardening at the implant site).

(38) Next, with reference to FIGS. 8A-8G, there are shown schematic views illustrating a method of filling an implant injection system 94 with polymethyl methacrylate (PMMA) bone cement. As can be seen in FIG. 8A, a cement loading syringe 96 is shown in position proximate to the delivery tip 98 of the implant injection system 94. The cement loading syringe 96 contains a predetermined quantity of a bone cement, such as PMMA (not shown), therein and the cement loading syringe 96 has an open, distal end 100 and a movable plunger 102 at the opposite end thereof.

(39) In FIG. 8B, the cement loading syringe 96 is in position proximate to the delivery tip 98 of the implant injection system 94. In FIG. 8C, the movable plunger 102 has been depressed to load the PMMA into the delivery tip 98 of the implant injection system 94. As such, in FIG. 8D, the cement loading syringe of FIG. 8C has been removed and a PMMA bolus 104 is present in the open, delivery tip 98 of the implant injection system 94, ready for injection into the bone of a patient.

(40) The PMMA material is specifically located at the distal end of the syringe 96 since PMMA is rheopectic and is difficult to push down a tube. A rheopectic material has a fluid flow behavior wherein time and stress affect the viscositythe longer a rheopectic material undergoes a shearing force, the higher its viscosity and the lower its flowability. Accordingly, rather than trying to push the material down the full length of the barrel of the syringe, the PMMA material is positioned at the distal end of the implant injection system 94, which then requires a short travel to the implant site.

(41) Turning next to FIG. 8E, the implant injection system 94 is shown in position to deliver the PMMA into the bone 106 of a patient. As can be seen in FIG. 8E, a hole 108 has been drilled into the bone 106 that passes through the cortical bone layer 108 and into the cancellous bone 110. The implant injection system 94 is shown in FIGS. 8E-8G to be a syringe with a plunger 112. Next, in FIG. 8F, the delivery tip 98 of the implant injection system 94 is placed into the hole 108 and is positioned proximate to the cancellous bone 110.

(42) Finally, in FIG. 8G, the plunger 112 has been depressed so as to force the PMMA bolus 104 into the cancellous bone 110, where it is allowed to expand into the cancellous bone 110 to act as an anchor or reinforcement.

(43) A suture could also be added to this embodiment to retain soft tissue to a bone surface.

(44) Furthermore, if desired, cooling can be provided to the distal end of implant injection system 94 to retard polymerization of the PMMA cement and allow for improved flowability and increased working time. By way of example but not limitation, implant injection system 94 may be configured to circulate a cooling fluid through the distal end of implant injection system 94 so as to provide cooling to PMMA bolus 104 prior to the injection of the PMMA bolus into cancellous bone 110. See, for example, FIG. 8H, which shows passageways 200 for circulating a cooling fluid through the distal end of implant injection system 94 so as to provide cooling to PMMA bolus 104 prior to the injection of the PMMA bolus into cancellous bone 110.

Modifications of the Preferred Embodiments

(45) While the present invention has been set forth in terms of a specific embodiment or embodiments, it will be understood that the present implant device and the method of using the same herein disclosed may be modified or altered by those skilled in the art to other configurations. Accordingly, the invention is to be broadly construed and limited only by the scope and spirit of the claims appended hereto.