SURGICAL INSTRUMENTS FOR CUTTING CAVITIES IN INTRAMEDULLARY CANALS

• US 20120179161A1
• Filed: 07/23/2010
• Published: 07/12/2012
• Est. Priority Date: 07/24/2009
• Status: Active Grant

• Current Assignee: Smith & Nephew Incorporated (Smith & Nephew PLC)
• Original Assignee: Smith & Nephew Incorporated (Smith & Nephew PLC)
• Inventors: Rains, James K., Black, Brian L.
• Granted Patent: US 9,381,031 B2
• Time in Patent Office: Days
• US Class Current: 606/80
• CPC Class Codes: A61B 17/1617 with mobile or detachable parts
• CPC Class Codes: A61B 17/1631 Special drive shafts, e.g. flexible shafts A61B17/1642, A61B17/164 take precedence
• CPC Class Codes: A61B 17/164 intramedullary
• CPC Class Codes: A61B 17/32002 with continuously rotating, oscillating or reciprocating cutting instruments
• CPC Class Codes: A61B 17/320725 with radially expandable cutting or abrading elements A61B17/32075 takes precedence
• CPC Class Codes: A61B 2017/00526 Methods of manufacturing
• CPC Class Codes: A61B 2017/320032 Details of the rotating or oscillating shaft, e.g. using a flexible shaft
• CPC Class Codes: A61B 2217/005 with suction drainage system
• CPC Class Codes: A61B 2217/007 with irrigation system

Abstract

Surgical instruments and procedures are disclosed that enable the injection of an optimal amount of curable resin and/or the placement of an internal fixation device in an intramedullary canal of a fractured bone. The disclosed instruments and procedures enable a surgeon to clear a portion of the canal of cancellous bone and marrow across the fracture site without damaging the cortical wall.

Claims

1. A surgical instrument for cutting a cavity in an intramedullary canal of a bone, the instrument comprising:

a shaft having a proximal end and a plurality of flexible cutting arms, and a distal nose section,

the flexible cutting arms being formed from a shape memory material and defining a relaxed effective outer diameter that is greater than effective outer diameters of the shaft and the distal nose section, the flexible cutting arms being compressible radially to a compressed effective outer diameter about equal to or less than the effective outer diameters of the shaft and distal nose section.

2. The instrument of claim 1, wherein the distal nose section includes a drill tip.

3. The instrument of claim 1, wherein the shape memory material is a shape memory alloy.

4. The instrument of claim 1, wherein the flexible cutting arms have a width, a thickness, and are characterized by a ratio of width to thickness ranging from about 5:

1 to about 2;

1.

5. The instrument of claim 4, wherein the flexible cutting arms are configured to cut cancellous bone and are configured to substantially not cut cortical bone.

6. The instrument of claim 1, wherein an expansion force exerted by the cutting arms when the cutting arms are released from the compressed effective outer diameter to the relaxed effective outer diameter ranges from about 1.0 lbf to about 8.0 lbf.

7. The instrument of claim 6, wherein the flexible cutting arms are configured to cut cancellous bone and are configured to substantially not cut cortical bone.

8. The instrument of claim 6, wherein the flexible cutting arms have a width, a thickness, and are characterized by a ratio of width to thickness ranging from about 5:

1 to about 2;

1.

9. The instrument of claim 1, wherein each flexible cutting arm is helical and rotates at an angle from between about negative 60 degrees to about 60 degrees from a longitudinal axis of the instrument.

10. The instrument of claim 9, wherein an expansion force exerted by the flexible cutting arms when the flexible cutting arms are released from the compressed effective outer diameter to the relaxed effective outer diameter ranges from about 1.0 lbf to about 8.0 lbf.

11. The instrument of claim 9, wherein the flexible cutting arms have a width, a thickness and are characterized by a ratio of width to thickness ranging from about 5:

1 to about 2;

1.

12. The instrument of claim 9, wherein the flexible cutting arms are configured to cut cancellous bone and are configured to substantially not cut cortical bone.

13. The instrument of claim 9, wherein the shape memory material is a shape memory alloy.

14. The instrument of claim 1, wherein the flexible cutting arms are left-hand helical.

15. The instrument of claim 1, wherein the shaft comprises at least one of a biocompatible polymer, a steel cable and a twisted wire.

16. A surgical instrument for cutting a cavity in an intramedullary canal of a bone, the instrument comprising:

a shaft comprising a proximal end and a distal end, the distal end of the shaft being coupled to a plurality of flexible helical cutting arms, the plurality of flexible helical cutting arms coupling the shaft to a distal nose section,

the flexible helical cutting arms being formed from a shape memory material and defining a relaxed effective outer diameter that is greater than effective outer diameters of the shaft and the distal nose section, the flexible helical cutting arms being compressible radially to a compressed effective outer diameter about equal to or less than effective outer diameters of the shaft and distal nose section.

17. The instrument of claim 16, wherein the distal nose section includes a drill tip.

18. The instrument of claim 16, wherein the shape memory material is a shape memory alloy.

19. The instrument of claim 16, wherein the flexible helical cutting arms have a width and a thickness, and are characterized by a ratio of width to thickness ranging from about 5:

1 to about 2;

1.

20. The instrument of claim 16, wherein an expansion force exerted by the flexible helical cutting arms when the flexible helical cutting arms are released from the compressed effective outer diameter to the relaxed effective outer diameter ranges from about 1.0 lbf to about 8.0 lbf.

21. The instrument of claim 16, wherein the flexible helical cutting arms are configured to cut cancellous bone and are configured to substantially not cut cortical bone.

22. The instrument of claim 16, wherein the flexible cutting arms are left-hand helical.

23. The instrument of claim 16, wherein the shaft comprises at least one of a biocompatible polymer, a steel cable and a twisted wire.

24. A surgical instrument for cutting a cavity in an intramedullary canal of a bone, the instrument comprising:

a shaft; and

a plurality of flexible and helical cutting arms, the flexible and helical cutting arms being formed from a shape memory alloy and defining a relaxed effective outer diameter that is greater than an effective outer diameter of the shaft, the flexible cutting arms being compressible radially to a compressed effective outer diameter about equal to or less than the effective outer diameter of the shaft,

wherein an expansion force exerted by the flexible and helical cutting arms is from about 1.0 lbf to about 8.0 lbf.

25. A method of repairing a bone fracture, the bone comprising a cortical wall, an intramedullary canal and a fracture site, the method comprising:

drilling an entry port in the bone that is spaced apart from a fracture site, the entry port providing access to an intramedullary canal of the fractured bone, the entry port having a diameter greater than effective outer diameters of a shaft and a distal nose section of a surgical instrument for forming a cavity in the intramedullary canal;

compressing flexible cutting arms of the surgical instrument;

inserting at least a portion of the surgical instrument into the intramedullary canal through the entry port; and

forming a cavity in the intramedullary canal proximate the fracture site.

26. The method of claim 25, wherein the distal nose section comprises a drill tip and wherein drilling the entry port in the bone comprises rotating the surgical instrument while the drill tip engages the bone.

27. The method of claim 25, wherein forming the cavity comprises rotating the surgical instrument so that the flexible cutting arms cut cancellous bone, the flexible cutting arms being configured to substantially not cut cortical bone.

28. The method of claim 25, further comprising allowing the flexible cutting arms to expand towards a relaxed effective outer diameter within the intramedullary canal due to an expansion force applied, at least in part, by a spring effect of the material of the flexible cutting arms, the expansion force being from about 1.0 lbf to about 8.0 lbf.

29. The method of claim 28, wherein the expansion force is insufficient to allow the flexible cutting arms to substantially cut cortical bone.

30. The method of claim 25, further comprising removing material from the intramedullary canal through a lumen disposed in the shaft of the surgical instrument.

31. The method of claim 25, further comprising irrigating the intramedullary canal by dispensing irrigation fluid through a lumen disposed in the shaft of the surgical instrument.

32. The method of claim 25, further comprising withdrawing the surgical instrument through the entry port, injecting a curable resin through the entry port into the cavity, and allowing the resin to cure.

33. The method of claim 25, wherein the entry port is drilled in a non-articular surface of the bone, and wherein inserting at least a portion of the surgical instrument comprises bending the shaft of the surgical instrument.

34. A method of forming a cavity in a bone, the bone having cortical wall, cancellous bone, an intramedullary canal, and a fracture site, the method comprising:

drilling an entry port in the bone that is spaced apart from the fracture site, the entry port providing access to the intramedullary canal of the fractured bone;

inserting a surgical instrument through the entry port to the intramedullary canal by compressing flexible cutting arms of the surgical instrument;

rotating the surgical instrument to remove cancellous bone without substantially damaging the cortical wall; and

moving the surgical instrument within the intramedullary canal to create a cavity.

35. The method of claim 34, wherein the cavity substantially follows the shape of the cortical wall.