Surgical reaming instrument for shaping a bone cavity

Abstract

Disclosed herein are systems and methods for shaping bone voids during revision procedures of total knee replacements. The systems disclosed herein generally include a cannulated reamer assembly, a reaming guide assembly, a guide tube assembly, a trial stem assembly, and an optional insertion/removal tool. Metaphyseal reconstruction devices can be used to fill the bone voids in conjunction with the systems and methods disclosed herein.

Description

CROSS-REFERENCE TO RELATED or tibial void filler 800. The tibial MRD 800 is placed within the one or more reaming voids 710, 712 and 714 in the bone 700. The tibial MRD 800 includes a central body 810 and lateral and medial members 812, 814. Tibial MRD 800 also includes a central opening 802 that extends through central body 810 to allow insertion of a trial stem 400, in this case a tibial stem. The central opening 802 also allows for insertion of the stem boss of a tibial baseplate (not shown), the tibial baseplate being engaged to the proximal side of the tibial MRD 800. The tibial MRD 800 can also include fin clearances 804 to permit rotation and position adjustment of the tibial baseplate. Lateral member or lateral offset member 812 is connected to central body 810 at a lateral side thereof while medial member or medial offset member 814 is connected to central body 810 at a medial side thereof. Central body 810 and lateral and medial members 812, 814 are each conically shaped and each define a longitudinal axis depicted respectively as axes A, B, and C which are offset from each other in a lateral-medial direction, as shown in FIG. 12C. The outer surfaces 806 of the tibial MRD 800 are configured to match the dimensions of surfaces of the bone 700 created by a particular cannulated reamer assembly 600. In this illustrative embodiment, outer surfaces 806 include three blended tapered conical surfaces that match the surface in the bone 700 created by the three reaming steps described above. In this regard, outer surfaces 806 are curved surfaces that each extend/curve about longitudinal axis A, B, or C of the respective central body 810, lateral member 812, and medial member 814 and taper inwardly from a proximal end to a distal end of MRD 800. However, since axes B and C are angled inwardly toward axis A, as shown, curved outer surfaces 806 of lateral and medial members 812, 814 have a greater taper or slope than curved surface 806 of central body 810. Longitudinal axes A, B, and C correspond to the axes 720, 722 and 724 of the void formed by pockets 710, 712, and 714 shown in FIGS. 11D and 11E such that when MRD 800 is implanted into such void, axes A, B, and C align with axes 720, 722, and 724, respectively. Lateral and medial members 812, 814 are integrated into central body 810 such that the curved outer surfaces 806 of lateral and medial members 812, 814 respectively meet with outer surface 806 of central body 810 at an interfaces between the central body 810 and members 812 and 814. Such interfaces form indentations 808 that each appear as a longitudinally extending indented groove that extends in a proximal-distal direction along the entire length of the particular interface. As shown, lateral and medial members 812, 814 each interface with central body 810 at two locations such that MRD 800 has four of such indentations 808, as best shown in FIG. 12A.

FIG. 13A shows the tibial MRD 800 prior to insertion into the void in the bone 700 consisting of the central pocket 710, the medial reaming void 712 and the lateral reaming void 714. FIG. 13B shows a side view of the bone 700 with the tibial MRD 800 inserted, along with section origin 13C. FIG. 13C shows a cross section along section origin 13C of the bone 700 with tibial MRD 800 inserted.

FIGS. 14A-D show, respectively, superior, isometric, anterior, and lateral views of an MRD. In this illustrative embodiment, the MRD is a femoral MRD 900. The femoral MRD 900 is generally similar to the tibial MRD 800, with the main difference being that the femoral MRD 900 is inserted into the bone void created by a reaming process on the distal end of the femur. The femoral MRD 900 includes a central opening 902 to allow for passage of a femoral stem. The femoral MRD 900 also can include tapered conical surfaces 904 to correspond to the particular shape of the bone voids created in the reaming process. Additionally, the femoral MRD 900 can include a first clearance space 906 for a femoral cam box, if needed, and a second clearance space 908 for the anterior chamfer of a femoral implant. FIGS. 14E and 14F show the femoral MRD 900 before and after attachment to the femoral implant 910, respectively. In this illustration, the femoral stem is omitted from the femoral stem attachment site 912 for clarity. The present invention can be used for multiple types of MRD implantation. For example, cemented MRDs can be used within the scope of this invention, in which there is a gap between the MRD and the balance of the implant construct, which is filled with bone cement during the procedure. Additionally, locked MRDs can be used within the scope of this invention, in which a mechanical connection, such as a taper lock, is made between the MRD and the balance of the implant construct.

There are many benefits of performing a revision procedure with the surgical reaming instrument of the present invention. For example, all bone removal steps may be fully guided without the need for any freehand bone removal. Additionally, the present invention provides a surgeon with the option of performing a guided ream of the bone either by hand or by using a powered source, such as a drill. Further, the instruments generally anatomically match typical bone voids observed in surgery. For example, the prepared cavity can be wider in the medial/lateral direction than in the anterior/posterior direction. Another related benefit is that the instrument has the capability to prepare asymmetric cavities, such as larger cavities on the medial side than the lateral side, which is often seen in cases of tibial bone voids. Importantly, because of the precision of control allowed when using this instrument, the shape of the cavity can be precisely controlled which allows for stock MRDs to accurately fit into the bone void without dependence on the technique of the particular surgeon performing the surgery. Related to this is that the symmetric, geometrically defined shape of the MRD simplifies the setup and machining of void fillers. Yet another benefit of an embodiment of this invention is that it allows a cannulated reamer set to consist of differently sized modular reaming heads and a single shaft to fit all reaming head sizes. This results in a reduced cost and size of the instrument set. The MRDs described herein can be made of any biocompatible material such as polymer and stainless steel, for example.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention.

Claims

1. A surgical system for preparing bone comprising:

a reaming guide assembly including:

a trial stem having a proximal end and a longitudinal axis, the trial stem configured to fit into an intramedullary canal in the bone, and

a guide tube assembly having a guide tube coupled to the proximal end of the trial stem such that a longitudinal axis of the guide tube is angled with respect to the longitudinal axis of the trial stem; and

a cannulated reamer assembly for shaping a bone cavity, the cannulated reamer assembly having a proximal end, a reaming head coupled at a distal end and a cannulation extending through the reaming head and distal end thereof,

wherein a longitudinal axis of the cannulated reamer assembly is angled with respect to the longitudinal axis of the trial stem when at least a portion of the guide tube is housed within the cannulation of the cannulated reamer assembly, and

wherein the cannulated reamer assembly is both rotatable about and slidable along the guide tube during operation.

2. The surgical system of claim 1, wherein the proximal end of the cannulated reamer assembly is configured to engage a torque applying device.

3. The surgical system of claim 1, wherein the cannulated reamer assembly further comprises a quick connect mechanism having a ball detent engaged to a distal end of a reamer shaft, the ball detent selectively engaging a notch in a proximally protruding extension of the reaming head in order to couple the reamer shaft to the reamer head.

4. The surgical system of claim 1, wherein the reaming guide assembly further comprises a handle assembly for manipulating the reaming guide assembly, the handle assembly coupled to the proximal end of the trial stem such that a surgeon can manipulate the reaming guide assembly while the trial stem is located in the intramedullary canal.

5. The surgical system of claim 4, further comprising an insertion/removal tool for efficient removal of the reaming guide assembly from the bone canal, the insertion/removal tool having a distal end configured for selective engagement to the proximal end of the trial stem.

6. The surgical system of claim 4, wherein the guide tube assembly and the handle assembly are fixed with respect to each other and are rotatably mounted to the proximal end of the trial stem such that a surgeon may rotate the guide tube assembly and the handle assembly about the longitudinal axis of the trial stem while the guide tube assembly and the handle assembly partially reside within a central pocket in the bone.

7. The surgical system of claim 6, further comprising a tibial implant for implantation into the bone cavity prepared by the reaming guide and cannulated reamer assemblies, the tibial implant being shaped to match contours of the bone cavity and having a central opening defined therethrough, wherein the central opening is configured to permit the passage of the trial stem or a stem boss of a tibial baseplate into the intramedullary canal.

8. The surgical system of claim 7, wherein the shape of the tibial implant includes at least two outer surfaces being blended tapered conical surfaces that substantially match the contours of the bone cavity.

9. The surgical system of claim 8, wherein the tibial implant further comprises a proximal surface, a lateral wall, a medial wall and a fin clearance for positional adjustment of the tibial baseplate, the fin clearance defines a groove that extends from the lateral wall through the medial wall and extends through the proximal surface.

10. The surgical system of claim 6, further comprising a femoral implant for implantation into the bone cavity, the femoral implant being shaped to match contours of the bone cavity and having a central opening defined therethrough, wherein the central opening is configured to permit the passage of a femoral stem into the intramedullary canal.

11. The surgical system of claim 10, wherein the shape of the femoral implant includes at least two outer surfaces being tapered conical surfaces that substantially match the contours of the bone cavity.

12. The surgical system of claim 11, wherein the femoral implant further comprises a posterior wall, an anterior wall and a first and second clearance space, wherein the first clearance space defines a recess in the posterior wall shaped to accommodate a femoral cam box, wherein the second clearance space defines a cut in anterior wall shaped to accommodate an anterior chamfer of a femoral implant.

13. A surgical method for preparing bone comprising the steps of:

placing a reaming guide assembly at least partially into an already formed intramedullary canal and central pocket that is in fluid communication with the intramedullary canal, the reaming guide assembly comprising a trial stem and guide tube assembly, the trial stem having a proximal end configured to be received in the intramedullary canal, the guide tube assembly having a guide tube coupled to the proximal end of the trial stem such that a longitudinal axis of the guide tube is angled with respect to a longitudinal axis of the trial stem;

coupling a cannulated reamer assembly to the guide tube assembly such that the proximal end of the guide tube assembly is housed within a cannulation of the cannulated reamer assembly and the reaming head contacts bone at a first position; and

driving the cannulated reamer along the guide tube to a predetermined depth into the bone, thereby forming a first reamed bone cavity adjacent to the central pocket.

14. The method of claim 13, wherein the reaming guide assembly further comprises a handle assembly, the handle assembly being fixed at the proximal end of the trial stem such that the handle assembly at least partially resides in the central pocket when the trial stem is fully seated in the intramedullary canal.

15. The method of claim 13, wherein the guide tube assembly is rotatably mounted to the proximal end of the trial stem such that the guide tube assembly can be rotated about the trial stem from the first position to a second position.

16. The method of claim 15, further comprising the step of rotating the handle assembly and guide tube assembly to the second position while partially residing within the central pocket.

17. The method of claim 16, further comprising the step of reaming bone at the second position with the cannulated reamer assembly placed over the guide tube assembly, thereby forming a second reamed bone cavity adjacent to the central pocket.

18. A method for preparing bone to receive a revision prosthesis comprising the steps of:

reaming the bone generally along an intramedullary canal with an intramedullary reamer having a proximal end;

placing a cannulated reamer assembly having a reaming head over the proximal end of the intramedullary reamer such that the reaming head contacts the bone;

driving the cannulated reamer into bone to a predetermined depth, thereby forming a central bone pocket;

removing the intramedullary reamer and cannulated reamer assembly from the intramedullary canal and central bone pocket;

placing a reaming guide assembly at least partially into the intramedullary canal and central bone pocket; wherein the reaming guide assembly comprises a trial stem, a guide tube assembly, and a handle assembly, the trial stem having a proximal end and being configured to fit into the intramedullary canal, the guide tube assembly having a proximal end and distal end that is rotatably fixed to the proximal end of the trial stem at an oblique angle such that the guide tube assembly at least partially resides in the central bone pocket when the trial stem is fully seated in the intramedullary canal, the handle assembly being fixed at the proximal end of the trial stem such that the handle assembly at least partially resides in the central bone pocket when the trial stem is fully seated in the intramedullary canal;

placing the cannulated reamer assembly over the proximal end of the guide tube assembly such that the reaming head contacts bone at a first position; and

driving the cannulated reamer into bone to a predetermined depth, thereby forming a first bone cavity adjacent to the central bone pocket.

19. The method of claim 18, further comprising the step of rotating the handle assembly and guide tube assembly with respect to the trial stem while partially residing within the central pocket to a second position.

20. The method of claim 19, further comprising the step of reaming bone at the second position with the cannulated reamer assembly placed over the guide tube assembly, thereby forming a second bone cavity adjacent to the central pocket.

21. The method of claim 13, further comprising:

disengaging a pin located at a distal end of the guide tube assembly from a first notch disposed at a first location about the trial stem;

rotating the guide tube assembly about the trial stem; and

engaging the pin with a second notch disposed at a second location about the trial stem.

22. A method of implanting a tibial prosthesis in a total knee revision arthroplasty, comprising:

removing a previously implanted tibial prosthesis from a proximal end of a tibia; and

implanting a void filler into the proximal end of the tibia, the proximal end of the tibia having a bone void previously formed by a surgical instrument so as to form a central pocket and lateral and medial pockets blended into the central pocket, the central pocket and lateral and medial pockets having been formed to correspond to a geometry of the void filler so that when the void filler is implanted, a central body of the void filler is received in the central pocket, lateral and medial members of the void filler are respectively received in the lateral and medial pockets, and an opening extending entirely through the central body of the void filler communicates with an intramedullary canal of the tibia, wherein the central body and lateral and medial members each have a curved outer surface that extends about a respective longitudinal axis, the curved outer surface of each of the lateral and medial members tapering inwardly from a proximal end of the void filler to a distal end thereof, the lateral member being integrated into the central body such that the curved outer surfaces of the lateral member and the central body meet at an interface between the lateral member and central body, the interface forms an indented groove that extends in a proximal-distal direction along an entire length of the interface.

23. The method of claim 22, further comprising connecting the void filler to a baseplate component, wherein the void filler is constructed separately from the baseplate component.

24. The method of claim 23, wherein connecting the void filler to the baseplate component includes inserting a stem boss of the baseplate component into the opening extending through the central body of the void filler.

25. The method of claim 23, wherein connecting the void filler to the baseplate component includes inserting a tibial stem through the opening of the central body of the void filler.

26. The method of claim 25, further comprises implanting the baseplate component onto the proximal end of the tibia such that the tibial stem extends from the opening of the central body and into the intramedullary canal and such that the baseplate component engages a proximal end of the void filler.

27. A method of implanting a tibial prosthesis in a total knee revision arthroplasty, comprising:

removing a previously implanted tibial prosthesis from a tibia;

forming a bone void in the tibia at a proximal end thereof so as to form a central portion and adjacent offset portions of the bone void, the offset portions joining the central portion and tapering inwardly from the proximal end of the tibia toward a distal end thereof, wherein forming at least one of the offset portions of the void includes moving a cutting tool axially along a longitudinal axis into the bone and removing the cutting tool from the bone by moving the cutting tool along the same longitudinal axis, the cutting tool being constrained to movement along the longitudinal axis; and

implanting a void filler and a revision tibial prosthesis onto the proximal end of the tibia such that a central body and adjacent offset members of the void filler are respectively and conformingly disposed in the central and offset portions of the bone void, and such that a stem of the revision tibial prosthesis extends through an opening of the central body and a baseplate component of the revision tibial prosthesis is positioned adjacent a proximal end of the void filler and the proximal end of the tibia, wherein the offset members of the void filler and the central body each define a longitudinal axis about which a respective curved exterior surface thereof extends, the longitudinal axes of the offset members and void filler being offset in a lateral-medial direction.

28. The method of claim 27, further comprising mechanically locking the void filler to the revision tibial prosthesis.

29. The method of claim 27, further comprising inserting bone cement into a gap between the void filler and the tibial prosthesis so as to connect the void filler to the tibial prosthesis.

30. The method of claim 27, further comprising:

inserting a stem boss of the baseplate component of the tibial prosthesis into the opening of the central body, and

engaging a proximal end of the void filler with the tibial baseplate.

31. The method of claim 27, wherein forming the bone void is performed by an instrument having bone cutting surfaces that correspond to the central body and offset members of the void filler so that a peripheral geometry of the void filler matches surfaces in the tibia created by the instrument.

32. The method of claim 31, wherein the instrument is a reamer assembly.

33. The method of claim 27, wherein the offset members are conically tapered and have a taper greater than a taper of the central portion.