Injectable fastener system and method

Abstract

Methods and devices are shown for forming polymer fasteners into bone by expelling the polymer from a cannula. Devices and methods shown allow a user to form multiple fasteners of various sizes without re-loading a device. Devices and methods shown further provide temperature profiles during fastener formation that reduce or eliminate thermal necrosis. Devices and methods shown further provide fasteners with increased strength.

What is claimed is: 
     
       1. A bone support attachment device, comprising:
 an injection cannula sized to hold an amount of polymer to form a single fastener; 
 a polymer supply inlet coupled to a side of the injection cannula; 
 a plunger having a tip disposed at a first end of the injection cannula such that, when actuated, the plunger expels the amount of polymer from a second end of the injection cannula upon the plunger reaching the second end of the injection cannula; and 
 a chamber sized to house a block of polymer sufficient to form a plurality of fasteners, the chamber having a first end having a chamber polymer supply inlet and a second end distal the first end and connected to the polymer supply inlet to sequentially provide the amount of polymer to form a single fastener from the chamber,; and,  
 the chamber including an actively regulateda chamber heater, adjacent the chamber and configured to actively regulate the chamber so as to maintain a temperature profile from a first end of the chamber to the second end of the chamber, wherein the temperature profile comprises a temperature gradient from the first end of the chamber to the second end of the chamber and wherein the temperature gradient is warmer at the second end of the chamber than at the first end of the chamber. 
 
     
     
       2. The bone support attachment device of  claim 1 , wherein the actively regulated chamber heater comprises multiple heating elements. 
     
     
       3. The bone support attachment device of  claim 1 , wherein the actively regulated chamber heater comprises multiple thermal control circuits. 
     
     
       4. A bone support attachment device of  claim 1 , further comprising an actively regulated a cannula heater disposed at a tip region of the device configured to actively regulate the injection cannula so as to maintain a consistent temperature profile from the first end of the injection cannula to the second end of the injection cannula, wherein the temperature profile comprises a temperature gradient from the first end of the injection cannula to the second end of the injection cannula and wherein the temperature gradient is warmer at the first end of the injection cannula than at the second end of the injection cannula. 
     
     
       5. The bone support attachment device of  claim 4 , wherein the actively regulated cannula heater comprises multiple heating elements. 
     
     
       6. The bone support attachment device of  claim 4 , wherein the actively regulated cannula heater comprises multiple thermal control circuits. 
     
     
       7. The bone support attachment device of  claim 4 , wherein the actively regulated cannula heater is configured to raise a temperature of the polymer within the injection cannula to a melting point of the polymer and is configured to actively control the temperature of the polymer at the second end of the injection cannula to a temperature that is low enough to not cause necrosis when the polymer is discharged from the injection cannula to contact tissue. 
     
     
       8. The bone support attachment device of  claim 4 , wherein the actively regulated cannula heater is configured to raise a temperature of the polymer within the injection cannula to between 50° C. and 250° C. 
     
     
       9. The bone support attachment device of  claim 8 , wherein the actively regulated cannula heater is configured to raise the temperature of the polymer within the injection cannula to between 130° C. and 180° C. 
     
     
       10. The bone support attachment device of  claim 1 , further comprising a depth gauge proximate the second end of the injection cannula, the depth gauge configured to move relative to the second end of the injection cannula once a predetermined volume of polymer is expelled from the second end of the injection cannula. 
     
     
       11. The bone support attachment device of  claim 10 , wherein the depth gauge is positionable configured as a static shelf and positioned at a selectable proximal distance from the second end of the injection cannula. 
     
     
       12. The bone support attachment device of  claim 10 , wherein the second end of the injection cannula is configured to extend a selectable distance from the depth gauge. 
     
     
       13. The bone support attachment device of claim  12  11, wherein the selectable proximal distance is greater than a thickness of a bone support such that when the bone support is engaged with a static shelf of the depth gauge, the second end of the injection cannula extends completely through the bone support. 
     
     
       14. The bone support attachment device of  claim 1 , wherein the actively regulated chamber heater is configured to raise a temperature of the polymer within the chamber to a melting point of the polymer and is configured to actively control the temperature of the polymer at the second end of the chamber to a temperature that is low enough to not cause necrosis when the polymer is discharged from the injection cannula to contact tissue permits the polymer to flow into the polymer supply inlet. 
     
     
       15. The bone support attachment device of  claim 1 , wherein the actively regulated chamber heater is configured to raise a temperature of a portion of the polymer within the chamber to between 50° C. and 250° C. 
     
     
       16. The bone support attachment device of  claim 15 , wherein the actively regulated chamber heater is configured to raise a temperature of a portion of the polymer within the chamber to between 130° C. and 180° C. 
     
     
       17. The bone support attachment device of  claim 1 , wherein a temperature at the second end of the injection cannula is controlled in a range within approximately 37° C. to 55° C. 
     
     
       18. The bone support attachment device of  claim 1 , wherein a starting plunger location is variable to provide a variable volume in the injection cannula that corresponds to a selectable amount of polymer to form fasteners of various sizes. 
     
     
       19. The bone support attachment device of  claim 1 , further comprising a chamber plunger configured to expel polymer from the chamber into the injection cannula when actuated. 
     
     
       20. The bone support attachment device of  claim 1 , wherein at least a portion of the plunger is configured to reduce adhesion of polymer to the plunger. 
     
     
       21. The bone support attachment device of  claim 1 , further comprising an actuator configured to advance the plunger at a rate sufficient for at least a portion of the polymer expelled from the injection cannula to interdigitate within a bone into which the injection cannula is extended. 
     
     
       22. The bone support attachment device of  claim 1 , further comprising an actuator configured to advance the plunger at a rate sufficient to form a bulbous polymer tip proximate a point distal to the second end of the injection cannula, the point distal to the second end of the injection cannula being defined by an inner cortical bone surface that is opposite a cortical bone surface upon which a bone support is positioned when the injection cannula is extended through the bone support during operation of the bone support attachment device. 
     
     
       23. The bone support attachment device of  claim 1 , wherein the plunger, when actuated, cuts off the supply inlet. 
     
     
       24. A bone support attachment device, comprising:
 an injection cannula sized to hold a first amount of polymer to form a single fastener;   a polymer supply inlet coupled to a side of the injection cannula;   a plunger having a tip disposed at a first end of the injection cannula such that, when activated, the plunger expels the first amount of polymer from a second end of the injection cannula upon the plunger reaching the second end of the injection cannula;   a chamber sized to house a second amount of polymer sufficient to form a plurality of fasteners, the chamber having a first end having a chamber polymer supply inlet and a second end distal the first end and connected to the polymer supply inlet to sequentially provide the first amount of polymer to form a single fastener from the chamber; and,   a chamber heater, adjacent the chamber and configured to actively regulate the chamber so as to maintain a temperature profile from a first end of the chamber to the second end of the chamber, wherein the temperature profile comprises a temperature gradient from the first end of the chamber to a the second end of the chamber and wherein the temperature gradient is warmer at the second end of the chamber than at the first end of the chamber.   
     
     
       25. A bone support attachment device, comprising:
 an injection cannula sized to hold an amount of polymer to form a single fastener;   a polymer supply inlet in fluid communication with a side of the injection cannula;   a plunger having a tip disposed at a first end of the injection cannula such that, when activated, the plunger expels the amount of polymer from a second end of the injection cannula upon the plunger reaching the second end of the injection cannula;   a chamber sized to house a supply of polymer sufficient to form a plurality of fasteners, the chamber having a first end having a chamber polymer supply inlet and a second end distal the first end and in fluid communication with the polymer supply inlet to sequentially provide the amount of polymer to form a single fastener from the chamber; and,   a chamber heater, adjacent the chamber and configured to actively regulate the chamber so as to maintain a temperature profile from a first end of the chamber to the second end of the chamber, wherein the temperature profile comprises a temperature gradient from the first end of the chamber to a the second end of the chamber and wherein the temperature gradient is such that the polymer is warmer at the second end of the chamber than at the first end of the chamber.   
     
     
       26. A bone support attachment device for forming fasteners from a polymer composition, the bone support attachment device comprising:
 an outer device body having a proximal portion, a distal end, and a distal tip portion located proximally from and adjacent to the distal end, the outer device body having a bore located at the distal end;   an injection cannula extending through the bore and having a first end located within the outer device body and a second end located distally from the bore of the device body, the injection cannula also having a polymer supply inlet through a side of the injection cannula;   a polymer supply chamber having an inlet end and a discharge end in fluid communication with the inlet end and with the injection cannula through the polymer supply inlet;   a plunger having a plunger tip configured to be disposed within the injection cannula and to be movable within the injection cannula from the first end to the second end; and   a chamber heater adjacent the polymer supply chamber configured to actively maintain a rising temperature gradient for a polymer composition within the polymer supply chamber, wherein the rising temperature gradient is such that a temperature of the polymer composition at the inlet end is less than a temperature of the polymer composition at the discharge end of the polymer supply chamber.   
     
     
       27. The bone support attachment device of claim 26 wherein the injection cannula has a proximal portion adjacent the first end and wherein a maximum outer dimension of the plunger tip is from 2 to 200 μm less than a minimum inner dimension of inner walls of the injection cannula at the proximal portion of the injection cannula. 
     
     
       28. The bone support attachment device of claim 27, wherein the injection cannula has a distal portion adjacent the second end and wherein the plunger tip forms an interference fit with inner walls of the injection cannula at the distal portion of the injection cannula. 
     
     
       29. The bone support attachment device of claim 26 further comprising a quantity of a thermoplastic polymer composition that is non-flowable at room temperature located within the polymer supply chamber. 
     
     
       30. The bone support attachment device of claim 29 wherein the thermoplastic polymer composition comprises an aliphatic polyester. 
     
     
       31. The bone support attachment device of claim 30 wherein the aliphatic polyester comprises a homo- or co-polymer of polylactic acid, polyglycolic acid, or polycaprolactone. 
     
     
       32. The bone support attachment device of claim 29 wherein the thermoplastic polymer composition comprises polylactide/polyglycolide. 
     
     
       33. The bone support attachment device of claim 32 wherein the rising temperature gradient is sufficient to transition the thermoplastic polymer composition from a non-flowable state to a temperature up to or above the melting point of the thermoplastic polymer composition. 
     
     
       34. The bone support attachment device of claim 29, wherein the thermoplastic polymer composition includes a therapeutic agent. 
     
     
       35. The bone support attachment device of claim 34, wherein the therapeutic agent comprises an antibiotic. 
     
     
       36. A bone support attachment device for forming fasteners from a polymer composition, the bone support attachment device comprising:
 an outer device body having a proximal portion, a distal end, and a distal tip portion located proximally from and adjacent to the distal end, the outer device body having a bore located at the distal end;   an injection cannula extending through the bore and having a first end located within the outer device body and a second end located distally from the bore of the device body, the injection cannula also having a polymer supply inlet through a side of the injection cannula;   a polymer supply chamber having an inlet end and a discharge end in fluid communication with the inlet end and with the injection cannula through the polymer supply inlet;   a plunger having a plunger tip configured to be disposed within the injection cannula and to be movable within the injection cannula from the first end to the second end;   a cannula heater disposed at the distal tip portion configured to actively maintain a decreasing temperature gradient for a polymer composition within the injection cannula, wherein the decreasing temperature gradient is such that a first temperature of the polymer composition at a first position of the second end of the injection cannula is lower than a second temperature of the polymer composition at a second position located proximally from the first position within the injection cannula; and,   means for dissipating heat from a distal portion of the injection cannula.   
     
     
       37. The bone support attachment device of claim 36 wherein the injection cannula has a proximal portion adjacent the first end and wherein a maximum outer dimension of the plunger tip is from 2 to 200 μm less than a minimum inner dimension of inner walls of the injection cannula at the proximal portion of the injection cannula. 
     
     
       38. The bone support attachment device of claim 37, wherein the injection cannula has a distal portion adjacent the second end and wherein the plunger tip forms an interference fit with inner walls of the injection cannula at the distal portion of the injection cannula. 
     
     
       39. The bone support attachment device of claim 36 further comprising a quantity of a thermoplastic polymer composition that is non-flowable at room temperature located within the polymer supply chamber. 
     
     
       40. The bone support attachment device of claim 39 wherein the thermoplastic polymer composition comprises an aliphatic polyester. 
     
     
       41. The bone support attachment device of claim 40 wherein the aliphatic polyester comprises a homo- or co-polymer of polylactic acid, polyglycolic acid, or polycaprolactone. 
     
     
       42. The bone support attachment device of claim 39 wherein the thermoplastic polymer composition comprises a polylactide/polyglycolide polymer. 
     
     
       43. The bone support attachment device of claim 42 wherein the decreasing temperature gradient is sufficient to maintain the thermoplastic polymer composition in a flowable state. 
     
     
       44. The bone support attachment device of claim 39, wherein the thermoplastic polymer composition includes a therapeutic agent. 
     
     
       45. The bone support attachment device of claim 44, wherein the therapeutic agent comprises an antibiotic. 
     
     
       46. A bone support attachment device for forming fasteners from a polymer composition, the bone support attachment device comprising:
 an outer device body having a proximal portion, a distal end, and a distal tip portion located proximally from and adjacent to the distal end, the outer device body having a bore located at the distal end;   an injection cannula extending through the bore and having a first end located within the outer device body and a second end located distally from the bore of the device body, the injection cannula also having a polymer supply inlet through a side of the injection cannula;   a plunger having a plunger tip configured to be disposed within the injection cannula and to be movable within the injection cannula from the first end to the second end;   a polymer supply cartridge containing an amount of thermoplastic bioresorbable polymer, the polymer supply cartridge being removably attached to the outer device body and having a distal discharge opening in fluid communication with the injection cannula;   a heater located proximate the distal tip portion of the outer device body, wherein the heater is configured to actively regulate the temperature of the thermoplastic bioresorbable polymer in the injection cannula so as to maintain a temperature profile within the injection cannula;   wherein the temperature profile comprises a decreasing temperature gradient such that a first temperature of the thermoplastic bioresorbable polymer at a first position at the second end of the injection cannula is lower than a second temperature of the thermoplastic bioresorbable polymer at a second position located proximally from the first position within the injection cannula.   
     
     
       47. The bone support attachment device of claim 46, wherein the thermoplastic bioresorbable polymer comprises an aliphatic polyester. 
     
     
       48. The bone support attachment device of claim 47, wherein the aliphatic polyester comprises a homo- or co-polymer of polylactic acid, polyglycolic acid, or polycaprolactone. 
     
     
       49. The bone support attachment device of claim 48, wherein the co-polymer is polylactide/polyglycolide. 
     
     
       50. The bone support attachment device of claim 46, wherein the thermoplastic bioresorbable polymer includes a therapeutic agent. 
     
     
       51. The bone support attachment device of claim 50, wherein the therapeutic agent comprises an antibiotic.