INTERCONDYLAR NOTCH CUTTER FOR POSTERIOR STABILIZED FEMORAL KNEE PROSTHESIS

Abstract: An intercondylar notch cutter using a plunge milling bit and bit guide which engages parallel tracks in a trial prosthesis. The intercondylar notch cutter comprises a cutting bit and a guide sleeve. The cutting bit can be thrust into the femur and then translated through the femur cutting a notch without removing the trial prosthesis. The bit is supported by a guide or housing with a guide platform which extends medially and laterally from the guide. Two condyle articulating surfaces on the platform slidingly engage a condyle surface on a trial prosthesis. Along the condyle surfaces on the trial prosthesis are two parallel grooves. Posts on the notch cutter are slidingly received within the grooves. A surgeon first places the trial implant on the femur without cutting an intercondylar notch. The surgeon can proceed immediately to cut an intercondylar notch without removing the femoral trial prosthesis.

Description: INTERCONDYLAR NOTCH CUTTER FOR POSTERIOR STABILIZED FEMORAL KNEE PROSTHESIS Technical Field This invention relates generally to orthopedic surgical devices and in particular to instrumentation used to prepare the distal surface of a femoral bone to receive a posterior stabilized knee prosthesis. Background Information Many kinds of prosthetic implantable knee prostheses are known to those skilled in this art. One type of knee prosthesis is a posterior stabilized prosthesis, such as those shown in U.S. patents 4,213,209 and 4,298,992. In the posterior-stabilized prosthesis, the tibial component has a central keel or post which extends upwardly from an articulating surface, and is adapted to extend between the condyles of the mating femoral prosthesis. This keel may be captured in a box structure or there may be a transverse post or bar which extends between the posterior portions of the condyles of the femoral prosthesis. As the knee articulates the keel engages sides of the femoral prosthesis located adjacent the condyles, thereby stabilizing the action of the knee. As the knee approaches full flexion, the keel commonly encounters a back wall of the box or the aforementioned transverse bar. The interaction of the keel and bar operate to force the femoral component to roll slightly posteriorly along the tibial component. In order to employ such a prosthesis, it is necessary to cut away a portion of the femur which will lie between the condyles of the femoral prosthesis. Such a removal of bone material is necessary so that the keel may slide between the condyles without obstruction. Various jigs and apparatus have been proposed for the removal of the bone material between the condyles. An example is U.S. patent 5,176,684 to Ferrante, et al. and related U.S. patents 5,100,409 to Coates, et al. and 5,098,436 to Ferrante, et al. Disclosure of the Invention We have invented an intercondylar notch cutter using a plunge milling bit and a bit guide which engages parallel tracks in a posterior stabilized femoral trial prosthesis. The intercondylar notch cutter comprises a cutting bit and a guide sleeve. The cutting bit can be thrust into the femur and then translated through the femur cutting a notch. A bit is supported by a guide or housing which comprises a hollow cylindrical shaft and a guide platform which extends medially and laterally from the cylinder. Two condyle articulating surfaces are provided on the platform. These surfaces slidingly engage a condyle surface on a trial prosthesis. Along the condyle surfaces on the trial prosthesis are two parallel grooves. Posts on the notch cutter are slidingly received within the grooves. A surgeon will be able to place the posterior stabilized femoral trial on the femur without first cutting an intercondylar notch. The anterior-posterior motion of the notch cutter is limited by the length of the parallel grooves. Thus, a minimum amount of bone is removed, allowing clearance for a keel of an articulating surface of a posterior stabilized tibial prosthesis, but conserving as much bone as possible. It is a principle object of the invention to provide an intercondylar notch cutter which utilizes the trial femoral prosthesis. Another object of the invention is to provide a notch cutter which can be used after a femoral trial prosthesis has been implanted and without removing the trial prosthesis. It is a further object of the invention to provide a notch cutter which removes a minimal amount of bone. Yet another object of the invention is to provide a notch cutter which is limited in anterior-posterior motion. A further object is to provide a notch cutter having a cutting implement which is limited to following a proposed path for a keel of a posterior stabilized tibial component. These and other objects and features of the invention will be apparent from the following detailed description, taken with respect to the accompanying drawings. Brief Description of the Drawings FIG. 1 is a perspective view of an intercondylar notch cutter according to the invention. FIG. 2 is an exploded perspective view of the notch cutter of FIG. 1. FIG. 3 is a side view of a femoral trial implant suitable for use with the notch cutter of FIG. 1 FIG. 4 is a front view of the femoral trial prosthesis of FIG.3. FIG. 5 is a cross-sectional view of the intercondylar notch cutter of FIG. 1 , taken along line 5-5 of FIG. 1. Best Mode for Carrying Out the Invention The invention is described below with reference to the accompanying drawings. Referring to FIGS. 1 , 2 and 5, the intercondylar notch cutter 10 comprises a cutting bit 12 and a guide sleeve or bushing 14. The cutting bit 12 has a milling head 16 at a distal end thereof. The milling bit 16 comprises four cutting blades 18 which allow the bit to be thrust into the femur and then translated through the femur, cutting a notch. Proximal from the blades 18 there is a bushing surface 20 which engages an inner surface of a cylindrical bore 22 in the guide 14. Proximal from the bushing surface is a shaft 26 and a gripping surface 28. Proximal from the gripping surface 28 there is a drive connector 30 which is adapted to engage a source of rotary motion, such as is commonly available in an operating theater. The bit 12 is supported by the guide sleeve 14 which comprises a hollow cylindrical shaft 32 which serves both as a handle for the apparatus and as support for the bit 12. Distally on the cylindrical shaft 32 there is a guide platform 34 which extends medially and laterally from the cylinder 32. Two condyle articulating surfaces 36, 38 are provided. These surfaces 36, 38 are configured to slidingly engage a condyle surface on a trial prosthesis, to be described below. Each articulating surface 36, 38 has a guide pin 40, 42 or guide rail which is adapted to engage slots in the femoral trial prosthesis. A through bore 44 fits the bit 12. Referring to FIGS. 3 and 4, a complementary posterior stabilized femoral trial prosthesis 50 is shown. It is known in this art to resect the distal surface of a femur and to place a trial prosthesis thereon to check the geometry of the knee. The invention can be used with the trial prosthesis in position. Without removing the femoral trial prosthesis 50, the surgeon will be able to cut an intercondylar notch, replace the tibial articulating surface with a surface having a central keel or post and recheck the knee for proper functioning. To this end, the femoral trial prosthesis 50 has an internal box geometry 52 which will mate with the resected distal surface of the femur. Two condyle articulating surfaces 54, 56 are provided. A bridge 58 connects these two surfaces. A permanent or removable posterior stabilizing bar 60 may also be provided. Along the condyle articulating surfaces are two parallel grooves 62, 64. The guide pins 40, 42 on the notch cutter 10 are adapted to be slidingly received within the grooves 62, 64. Ends of the grooves, such as ends 66, 68, act as stops to limit the anterior-posterior range of motion of the notch cutter. The stops allow the proper range of resection necessary to duplicate the path of the keel of the posterior stabilized tibial prosthesis. Using the invention, the surgeon will be able to place the trial implant on the femur without first cutting an intercondylar notch. Then the surgeon can proceed immediately to cut the intercondylar notch without removing the femoral condyle trial prosthesis. The invention may be embodied in other specific forms by those skilled in the art without departing from the spirit or essential teachings thereof. The foregoing description, therefore, is intended in all respects to be illustrative, and the invention is to be defined by the appended claims.

Claims: CLAIMS 1. A surgical apparatus for cutting an intercondylar notch in a distal end of a patient's femur for receiving a posterior stabilized knee prosthesis, said apparatus comprising a distal femoral trial prosthesis having a medial condyle part adapted to fit onto a resected distal part of the femur in place of the patient's medial condyle, the medial condyle part having a first distal convex articulating surface with a first groove extending in an anterior-posterior direction along said first surface, a lateral condyle part adapted to fit onto the resected distal part of the femur in place of the patient's lateral condyle, the lateral condyle part having a second distal convex articulating surface with a second groove extending in an anterior-posterior direction along said second surface, parallel to said first groove, said medial and lateral condyle parts being spaced apart from each other a distance sufficient to allow cutting of said intercondylar notch therebetween, and an intercondylar notch cutter having a medial concave guide surface fitted to slide on said medial convex articulating surface, said medial guide surface having a first pin adapted to be slidingly received in said first groove, a lateral concave guide surface fitted to slide on said lateral convex articulating surface, said lateral guide surface having a second pin adapted to be slidingly received in said first groove, a sleeve mounted between said medial and lateral guide surfaces, and a milling bit rotatably received in said sleeve, said milling bit being adapted to fit between said medial and lateral condyle parts of said distal femoral trial prosthesis. 2. The surgical apparatus according to claim 1 wherein each of said first and second grooves have end stops to limit the anterior-posterior range of motion of said intercondylar notch cutter. 3. A surgical apparatus for cutting an intercondylar notch in a distal end of a patient's femur for receiving a posterior stabilized knee prosthesis, said apparatus comprising: a distal femoral trial prosthesis, a notch cutter, and means for guiding said notch cutter with respect to said trial prosthesis, said distal femoral trial prosthesis providing access to an area of the patient's femur between the medial and lateral condyles and having means for replicating at least one condylar articulating surface of a permanent prosthesis, and said notch cutter having means for slidingly stabilizing said notch cutter on said condylar replicating means, and means connected to said stabilizing means for milling a notch in said area between said medial and lateral condyles. 4. The surgical apparatus according to claim 3 wherein said means for slidingly stabilizing said notch cutter further comprises means for limiting the anterior-posterior motion of said notch cutter means. 5. The surgical apparatus according to claim 4 wherein the means for guiding comprise at least one slot and means for tracking said slot. 6. The surgical apparatus according to claim 5 wherein the at least one slot is in said trial prosthesis. 7. The surgical apparatus according to claim 6 wherein said means for limiting the anterior-posterior motion of said notch cutter comprises end stops on said at least one slot. 8. The surgical apparatus according to claim 5 wherein the at least one slot comprises two parallel slots. 9. The surgical apparatus according to claim 8 wherein said means for limiting the anterior-posterior motion of said notch cutter comprise end stops on said slots. 10. The surgical apparatus according to claim 3 wherein said means for replicating at least one condylar articulating surface comprise means for replicating a medial articulating surface and means for replicating a lateral articulating surface, said medial and lateral articulating surface replicating means being spaced apart from one another to provide access to said area of the patient's femur between the medial and lateral condyles. 11. The surgical apparatus according to claim 10 wherein the means for guiding comprise at least one slot and means for tracking said slot. 12. The surgical apparatus according to claim 11 wherein said means for limiting the anterior-posterior motion of said notch cutter means comprise end stops on said at least one slot. 13. The surgical apparatus according to claim 12 wherein the at least one slot is in said trial prosthesis means. 14. The surgical apparatus according to claim 13 wherein the at least one slot comprises two parallel slots. 15. The surgical apparatus according to claim 12 wherein said means for limiting the anterior-posterior motion of said notch cutter means comprise end stops on said slots. 16. The surgical apparatus according to claim 15 wherein said slots are in said trial prosthesis. 17. The surgical apparatus according to claim 16 wherein one of said slots is in said means for replicating said medial articulating surface and the other of said slots is in said lateral articulating surface and wherein said means for stabilizing comprise first guide means for sliding on said medial articulating surface and second guide means for sliding on said lateral articulating surface and said milling means are mounted between said first and second guide means. 18. The surgical apparatus according to claim 17 wherein said means for tracking said slots comprise a first pin on said first guide means and a second pin on said second guide means. 19. A method for preparing a distal end of a patient's femur for receiving a femoral component of a knee prosthesis, comprising the steps of resecting the distal end of the femur, placing a posterior stabilized femoral trial prosthesis on said femur, said trial prosthesis having a medial condyle part adapted to fit onto said resected distal end of the femur in place of the patient's medial condyle, said medial condyle part having a first distal convex articulating surface, and a lateral condyle part adapted to fit onto the resected distal end of the femur in place of the patient's lateral condyle, said lateral condyle part having a second distal convex articulating surface, said medial and lateral condyle parts being spaced apart from each other, cutting an intercondylar notch between said medial and lateral condylar parts, and articulating said femoral trial prosthesis against a posterior stabilized tibial trial prosthesis. 20. The method according to claim 19 wherein the step of cutting an intercondylar notch further comprises placing an intercondylar notch cutter on said trial prosthesis, said notch cutter having a medial concave guide surface fitted to slide on said medial convex articulating surface, a lateral concave guide surface fitted to slide on said lateral convex articulating surface, a sleeve mounted between said medial and lateral guide surfaces, and a milling bit rotatably received in said sleeve, said milling bit being adapted to fit between said medial and lateral condyle parts of said distal femoral trial prosthesis, and milling a notch between said medial and lateral articulating surfaces. 21. The method according to claim 20 wherein said step of placing said intercondylar notch cutter comprises fitting pins on each of said medial and lateral guide surfaces into parallel slots on each of said medial and lateral articulating surfaces respectively and wherein the step of milling said notch comprises rotating a milling bit and moving said notch cutter by sliding said pins along said slots. 22. An intercondylar notch cutter having a medial concave guide surface fitted to slide on a medial convex articulating surface of a trial femoral knee prosthesis, said medial guide surface having first means for guiding said notch cutter along a predetermined path with respect to said trial prosthesis, a lateral concave guide surface fitted to slide on a lateral convex articulating surface of said trial femoral knee prosthesis, said lateral guide surface having second means for guiding said notch cutter along a predetermined path with respect to said trial prosthesis, a sleeve mounted between said medial and lateral guide surfaces, and a milling bit rotatably received in said sleeve. 23. The intercondylar notch cutter according to claim 22 wherein said first means for guiding said notch cutter comprise a first pin and wherein said second means for guiding said notch cutter comprise a second pin.

Inventors: HIGGINS JEFFERY C, MUMME CHARLES W, PERRONE CHARLES H JR, VINCIGUERRA JOHN D, HIGGINS, JEFFERY, C., MUMME, CHARLES, W., PERRONE, CHARLES, H., JR., VINCIGUERRA, JOHN, D.
Applicants: INTERMEDICS ORTHOPEDICS INC, INTERMEDICS ORTHOPEDICS, INC.
Application year: 1995
Main classification: A61B17
IPC codes: A61B17