US20100168752A1 - Orthopaedic cutting tool having a chemically etched metal insert and method of manufacturing - Google Patents

Abstract

An orthopaedic surgical instrument comprising an orthopaedic cutting tool includes a metallic cutting insert configured to remove portions of a patient's bone and a body molded to the cutting insert. The cutting insert includes a plurality of chemically etched holes, and the body is molded to the cutting insert such that each of the plurality of chemically etched holes is at least partially filled by a portion of the body. The cutting insert may include a plurality of cutting teeth configured to remove portions of the patient's bone. A method of manufacturing an orthopaedic surgical instrument is also disclosed.

Description

CROSS-REFERENCE TO RELATED U.S. PATENT APPLICATIONS
• Cross-reference is made to co-pending U.S. Utility patent application Ser. No. ______ entitled “Orthopaedic Cutting Block Having a Chemically Etched Metal Insert and Method of Manufacturing” by Jon Edwards et al. (Attorney Docket No. 265280-207638, DEP-6185), which is assigned to the same assignee as the present application, filed concurrently herewith, and hereby incorporated by reference.
TECHNICAL FIELD
• The present disclosure relates generally to orthopaedic surgical instruments, and more particularly to an orthopaedic cutting tool having a metallic cutting insert with chemically etched holes.
BACKGROUND
• Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged natural joint is replaced by a prosthetic joint. Typical artificial joints include knee prostheses, hip prostheses, shoulder prostheses, ankle prostheses, and wrist prostheses, among others. To facilitate the replacement of the natural joint with the prosthesis, orthopaedic surgeons use a variety of orthopaedic surgical instruments such as, for example, saws, drills, reamers, rasps, broaches, cutting blocks, drill guides, milling guides, and other surgical instruments. Typically, orthopaedic surgical instruments are fabricated from metal using traditional manufacturing processes, such as machining, turning, and drilling, and require sterilization between surgical procedures.
SUMMARY
• According to one aspect, an orthopaedic cutting tool may include a metallic cutting insert and a body molded to the cutting insert. The cutting insert may have a plurality of chemically etched holes and may be configured to remove portions of a patient's bone. The body may be molded to the cutting insert such that each of the plurality of chemically etched holes is at least partially filled by a portion of the body.
• In some embodiments, the cutting insert may have an interface surface which contacts the body and a work surface opposite the interface surface. The work surface of the cutting insert may be configured to remove portions of the patient's bone. Each of the plurality of chemically etched holes in the cutting insert may extend from the interface surface to the work surface of the cutting insert. The portion of the body which at least partially fills each chemically etched hole may fill at least half the volume of the hole.
• The cutting insert may include a plurality of cutting teeth configured to remove portions of the patient's bone, a relief surface between the plurality of cutting teeth, and an interface surface opposite the plurality of cutting teeth and the relief surface. The interface surface may contact the body of the orthopaedic cutting tool. Each of the plurality of chemically etched holes may extend from the interface surface to the relief surface of the cutting insert. The portion of the body which at least partially fills each chemically etched hole may fill at least half the volume of the hole. The body may be formed of an injection-molded polymer. The body may further include an integrally formed coupling feature. The body may further include an integrally formed handle portion.
• In another aspect, an orthopaedic surgical instrument may be embodied as an orthopaedic cutting tool. The orthopaedic surgical instrument may include a plurality of metallic cutting inserts, and a body molded to the plurality of cutting inserts. Each cutting insert may have a plurality of chemically etched holes and may be configured to remove portions of a patient's bone. The body may be molded to the cutting inserts such that each of the plurality of chemically etched holes is at least partially filled by a portion of the body.
• In some embodiments, each of the plurality of cutting inserts may have an interface surface which contacts the body, and a work surface opposite the interface surface. The work surface may be configured to remove portions of the patient's bone. Each of the plurality of chemically etched holes may extend from the interface surface to the work surface of the respective cutting insert.
• The body of the orthopaedic surgical instrument may further include a plurality of cutting flutes. The plurality of cutting flutes may be arranged radially around a longitudinal axis of the orthopaedic cutting tool. Each of the plurality of cutting inserts may be disposed on one of the plurality of cutting flutes. Each of the plurality of cutting inserts may also be aligned with a leading edge of one of the plurality of cutting flutes to allow a surgeon to remove portions of the patient's bone by rotating the orthopaedic cutting tool about the longitudinal axis.
• According to another aspect, a method for manufacturing an orthopaedic surgical instrument is disclosed. The method may include chemically etching a plurality of holes into a metallic cutting insert. The method may also include molding a body to the cutting insert to form an orthopaedic cutting tool. The method may include chemically etching each of the plurality of holes through the entire thickness of the cutting insert. The method may also include chemically etching a plurality of cutting teeth into the cutting insert. The plurality of holes and the plurality of cutting teeth may be chemically etched simultaneously.
• In some embodiments, the method may include forming a mask on the cutting insert. The mask may define a plurality of exposed areas on the cutting insert. The method may include placing the cutting insert having the mask in a chemical bath whereby the plurality of exposed areas are chemically etched into the plurality of holes. The method may also include removing the cutting insert having the mask from the chemical bath and removing the mask from the cutting insert. The method may include applying a photoresist material to the cutting insert, selectively exposing portions of the photoresist material to a light source using a patterned photomask, and selectively removing portions of the photoresist material using a developer to define the plurality of exposed areas on the cutting insert.
• In some embodiments, the method may include loading the cutting insert into a mold. The cutting insert may contact a wall of the mold. The method may also include injecting a polymer into the mold. The cutting insert may be pressed against the wall of the mold by the polymer. The polymer may at least partially fill the plurality of holes.
BRIEF DESCRIPTION OF THE DRAWINGS
• The detailed description particularly refers to the following figures, in which:
• FIG. 1 is a perspective view of one embodiment of an orthopaedic cutting block;
• FIG. 2 is a partially exploded, perspective view of the orthopaedic cutting block ofFIG. 1;
• FIG. 3A is a cross sectional view of a portion of a metallic bearing insert prior to chemical etching;
• FIG. 3B is a cross sectional view of the portion of the metallic bearing insert ofFIG. 3A after chemical etching;
• FIG. 3C is a cross sectional view of a portion of a metallic bearing insert after molding with the body, according to one embodiment.
• FIG. 3D is a cross sectional view of a portion of a metallic bearing insert after molding with the body, according to another embodiment.
• FIG. 4 is a perspective view of the orthopaedic cutting block ofFIG. 1 coupled to a bone of a patient;
• FIG. 5 is a partially exploded, perspective view of another embodiment of an orthopaedic cutting block;
• FIG. 6 is a perspective view of the orthopaedic cutting block ofFIG. 5 coupled to a bone of a patient;
• FIG. 7 is a perspective view of one embodiment of an orthopaedic cutting tool;
• FIG. 8 is a perspective view of the orthopaedic cutting tool ofFIG. 7;
• FIG. 9 is a perspective view of another embodiment of an orthopaedic cutting tool;
• FIG. 10 is a perspective view of a portion of the orthopaedic cutting tool ofFIG. 9;
• FIG. 11 is a simplified flow diagram of a method for manufacturing an orthopaedic surgical instrument;
• FIG. 12 is a simplified flow diagram of a method for chemically etching a metallic insert; and
• FIG. 13 is a simplified flow diagram of a method for forming a mask on a metallic insert.
DETAILED DESCRIPTION OF THE DRAWINGS
• While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
• Terms representing anatomical references, such as anterior, posterior, medial, lateral, superior, inferior, etcetera, may be used throughout this disclosure in reference to both the orthopaedic surgical instruments described herein and a patient's natural anatomy. Such terms have well-understood meanings in both the study of anatomy and the field of orthopaedics. Use of such anatomical reference terms in the specification and claims is intended to be consistent with their well-understood meanings unless noted otherwise.
• The present disclosure relates generally to orthopaedic surgical instruments which include one or more metallic inserts and a body molded to the metallic inserts. The metallic inserts may be positioned at or near areas of the orthopaedic surgical instrument which are subjected to the greatest forces during use. In some embodiments, the body may be an injection-molded polymer. The metallic inserts include a plurality of chemically etched holes. The chemically etched holes have distinctive structural characteristics and create adhesion between the metallic inserts and the body. The concepts of the present disclosure are applicable both to orthopaedic cutting blocks, which employ metallic bearing inserts, and to orthopaedic cutting tools, which employ metallic cutting inserts.
• Referring generally toFIGS. 1-4, one illustrative embodiment of an orthopaedic surgical instrument according to the present disclosure is anorthopaedic cutting block100 designed to function as a notch guide for use by a surgeon with a surgical bone saw. Similar components are labeled using similar reference numerals in these and all other figures. Theorthopaedic cutting block100 includes several metallic bearing inserts118,120 and abody102 molded to the bearing inserts118,120.
• As shown inFIGS. 1 and 2, thebody102 oforthopaedic cutting block100 includes ananterior plate104 and twodistal plates106, generally giving thebody102 the shape of an inverted “L” when viewed from the side and an inverted “U” when viewed from the top. Thebody102 further includes acentral notch opening108 defined by a medially-facingwall110, a distally-facingwall112, and a laterally-facingwall114. Theanterior plate104 includes a bone-facingsurface142 which is adapted to contact a resected anterior surface of a patient'sfemur10. Each of the twodistal plates106 includes a bone-facingsurface144 adapted to contact a resected distal surface of the patient'sfemur10. Thebody102 also includes six guide holes116 (four of which can be seen in each ofFIGS. 1 and 2). The number and placement of the guide holes116 may be varied, and not everyguide hole116 may require abearing insert118.
• Thebody102 may be formed of any material which may be molded to the bearing inserts118,120, including, but not limited to, polymers and resins. In some embodiments, thebody102 may be formed of a material which is less capable than the bearing inserts118,120 of withstanding external forces, but which is less expensive, lighter, and/or more easily fabricated into complex shapes. Thebody102 may be heterogeneous in nature or may be a composite material. In one illustrative embodiment, thebody102 is formed of an injection-molded polymer.
• The metallic bearing inserts118,120 are generally positioned at or near areas of theorthopaedic cutting block100 which are subjected to the greatest forces during use. The bearing inserts may be formed of a metal or metallic alloy; in one illustrative embodiment, the bearing inserts118,120 be formed ofType 316 or Type 17-4 grade stainless steel. Each bearing insert includes aninterface surface122, which contacts the body (visible in partially exploded view ofFIG. 2). Opposite theinterface surface122, each bearing insert also includes aguide surface124,126, which is configured to support a bone cutting tool. Each bearing insert118 functions as a bushing for one of the guide holes116. Thus, a drill bit or pin passing through one of the guide holes116 will only, or at least mostly, contact theguide surface124 of thebearing insert118 and not thebody102. The bearing insert120 functions as a non-captured cutting guide for thecentral notch opening108. Theguide surface126 includes a medially-facingsection128, a distally-facingsection130, and a laterally-facingsection132, which correspond, respectively, to the medially-facingwall110, the distally-facingwall112, and the laterally-facingwall114 of thebody102. Thus, a bone saw blade12 (shown inFIG. 4) cutting along thecentral notch opening108 will only, or at least mostly, contact theguide surface126 of thebearing insert120 and not thebody102. In another embodiment, two or more separate bearing inserts may be used in place of the single,multi-sectioned bearing insert120.
• Each bearinginsert118,120 includes a plurality of chemically etchedholes134. In one illustrative embodiment, each of the plurality of chemically etchedholes134 extends from theinterface surface122 to theguide surface124,126 of thebearing insert118,120. The chemically etchedholes134 have distinctive structural characteristics, which will be further described below with reference toFIGS. 3A-D, and create adhesion between the bearing inserts118,120 and thebody102. It is contemplated that the chemically etchedholes134 may consist of a variety of shapes and may be arranged in numerous patterns on the surface of the bearing inserts118,120. The chemically etchedholes134, in one illustrative embodiment, are circular in shape and approximately 1/50 of an inch in diameter. The bearing inserts118,120 may also include other chemically etched features in addition to the chemically etchedholes134. In one illustrative embodiment, bearinginsert120 may further include one or more chemically etchedgrooves136 and/or chemically etchedindicia138, such as reference markings, trade names, and product names or numbers, among others.
• As will be discussed in more detail below, chemically etchedholes134, as well as chemically etchedgrooves136, chemically etchedindicia138, and other features, may be formed by placing the metallic bearing inserts118,120 in a chemical bath which dissolves exposed metal. The bearing inserts118,120 may be selectively etched to form features, such as the plurality of chemically etchedholes134, by forming amask14, including a plurality of exposedareas18, around the bearing inserts118,120 prior to placement in the chemical bath, as shown inFIG. 3A. Themask14 may be formed of any material which is not substantially dissolved by the chemical bath.
• In one illustrative embodiment, themask14 is a polymeric photoresist material which is formed around thebearing insert120, but includes a plurality of exposed areas18 (seeFIG. 3A). A cross-section of thebearing insert120 ofFIG. 3A after removal from the chemical bath but prior to removal of thepolymeric photoresist mask14 is depicted inFIG. 3B. In areas which were exposed to the chemical bath on both sides of thebearing insert120, the resulting structure is a chemically etchedhole134. The distinctive structural characteristics of the chemically etchedhole134 are due in part to the isotropic nature of the wet, or liquid, chemical etch. As can be seen inFIG. 3B, as the chemical bath dissolves the metal of thebearing insert120 in a vertical direction, it also dissolves the metal in horizontal directions at approximately 20-25% the rate of the vertical direction. In areas which were exposed to the chemical bath on only one side of thebearing insert120, the resulting structure is a chemically etchedgroove136. Thegroove136 may run the entire width of theguide surface126 of thebearing insert120. As will be discussed in more detail below, thegroove136 allows for bending of the bearing insert120-between the medially-facingsection128 and the distally-facingsection130 and between the distally-facingsection130 and the laterally-facingsection132 of the guide surface126-prior to molding of thebody102 to thebearing insert120.
• The chemically etchedholes134 create adhesion between the bearinginsert120 and thebody102, as shown inFIG. 3C. As thebody102 is molded to thebearing insert120, a portion of thebody102 at least partially fills each of the plurality of chemically etchedholes134. After molding, thebody102 contacts thebearing insert120 at theinterface surface122 and the sidewalls of the chemically etchedholes134, but generally does not contact theguide surface126, providing a substantially allmetallic guide surface126 configured to support an orthopaedic cutting tool. In one illustrative embodiment, the portion of thebody102 which at least partially fills each chemically etchedhole134 may fill at least half the volume of eachhole134. In another illustrative embodiment, the portion of thebody102 which at least partially fills each chemically etchedhole134 may fill between 70-80% of the volume of eachhole134.
• In another illustrative embodiment, shown inFIG. 3D, the chemically etchedholes134 of bearinginsert120 may also be formed by exposing areas on only one side of thebearing insert120, but allowing thebearing insert120 to remain in the chemical bath for a longer period of time. This results in a chemically etchedhole134 with its own distinctive structural characteristics, including a taperedsidewall140. Again, a portion of thebody102 at least partially fills each chemically etchedhole134, but generally does not contact theguide surface126, providing a substantially allmetallic guide surface126 configured to support an orthopaedic cutting tool. It should be noted that each of the features described with respect to bearinginsert120 andFIGS. 3A-D, may apply equally to the bearing inserts118 and the chemically etchedholes134 thereof. Furthermore, for these and all other embodiments hereinafter disclosed, while a plurality of the chemically etchedholes134 are at least partially filled by portions of thebody102, it is contemplated that some of the chemically etchedholes134 may not be filled at all.
• Placement and use of theorthopaedic cutting block100 on the distal end of the patient'sfemur10 during surgery can be best seen inFIG. 4. Typically, the surgeon will have performed anterior and distal cuts or resections on the patient'sfemur10 prior to using theorthopaedic cutting block100 to perform a notch cut. Theorthopaedic cutting block100 is positioned such that the bone-facingsurface142 of theanterior plate104 contacts the resected anterior surface of the patient'sfemur10 and the bone-facingsurfaces144 of the twodistal plates106 contact the resected distal surface of the patient'sfemur10. Theorthopaedic cutting block100 is secured to the patient'sfemur10 by the placement of one or more (typically, three or more)surgical pins16 through the guide holes116. Once theorthopaedic cutting block100 is secured, the surgeon may use a typical bone saw having a bone sawblade12 to perform the notch cut using thebearing insert120 to support the bone sawblade12.
• Referring generally now toFIGS. 5 and 6, another illustrative embodiment of an orthopaedic surgical instrument according to the present disclosure is anorthopaedic cutting block200 designed to function as an anterior/posterior/chamfer cutting guide, also known in the art as a 4-in-1 cutting block, for use by a surgeon with a surgical bone saw. Theorthopaedic cutting block200 includes several metallic bearing inserts218-226 and abody202 molded to the bearing inserts218-226.
• Thebody202 oforthopaedic cutting block200 may be formed of any material which may be molded to the bearing inserts218-226, such as the materials discussed above with respect toorthopaedic cutting block100. As shown inFIG. 5, thebody202 includes a pair ofbody components204,206, which when combined give the orthopaedic cutting block200 a generally cuboid, or rectangular parallelepiped, outer shape. Both thebody component204 and thebody component206 include bone-facingsurfaces238 which are adapted to contact a resected distal surface of a patient'sfemur10. Thebody component204 further includes anelongated opening208, generally parallel to an imaginary line drawn between the medial and lateral sides of thebody component204. Theelongated opening208 is defined by a first pair of taperedwalls210 which open toward the distal side of thebody component204 and by a second pair of tapered walls (not shown) which open toward the proximal side of thebody component204. The second pair of tapered walls are designed to receive thebody component206, as indicated inFIG. 5. Thebody202 may also include guide holes216, on both thebody component204 and thebody component206. The number and placement of the guide holes216 may be varied, and not everyguide hole216 may require abearing insert218.
• Similar to the bearing inserts118,120 oforthopaedic cutting block100, the bearing inserts218-226 may be formed of a metal or metallic alloy and are generally positioned at or near areas of theorthopaedic cutting block200 which are subjected to the greatest forces during use. Each bearing insert includes aninterface surface236, which contacts thebody202. Opposite theinterface surface236, each bearing insert also includes a guide surface228-232 (and others not shown), which is configured to support a bone cutting tool. Each bearing insert218 functions as a bushing for one of the guide holes216. A drill bit or pin passing through one of the guide holes216 will only, or at least mostly, contact the guide surface of thebearing insert218 and not thebody202. The bearing insert220 functions as a non-captured cutting guide for performing an anterior cut on the patient'sfemur10. A bone sawblade12 cutting along the anterior side of theorthopaedic cutting block200 will only, or at least mostly, contact theguide surface232 of thebearing insert220 and not thebody202. Similarly, the bearing insert222 functions as a non-captured cutting guide for performing a posterior cut on the patient'sfemur10. A bone sawblade12 cutting along the posterior side of theorthopaedic cutting block200 will only, or at least mostly, contact the guide surface (not shown) of thebearing insert222 and not thebody202. In another illustrative embodiment, the anterior and posterior cutting guides oforthopaedic cutting block200 may alternatively be captured cutting slots, similar to those described below, rather than non-captured cutting guides.
• Theorthopaedic cutting block200 also includes two captured cutting slots which may support a bone sawblade12 when performing a pair of chamfer cuts on the patient'sfemur10. As discussed above, thebody component204 includes anelongated opening208, which is in part defined by a second pair of tapered walls which open toward the proximal side of thebody component204. A metallic bearing insert is disposed on each of the second pair of tapered walls: bearing insert224 on the lower tapered wall, and another bearing insert (not shown) on the upper tapered wall. Thebody component206 also has abearing insert226. The guide surface of thebearing insert226 includes a downwardly-facingsection228 and an upwardly-facingsection230. When thebody component204 and thebody component206 are assembled, these bearing inserts form two captured cutting slots. The downwardly-facingsection228 of bearinginsert226 opposes thebearing insert224 with a gap therebetween to form a downwardly-angled, captured cutting slot. The upwardly-facingsection230 of bearinginsert226 opposes the other bearing insert (not shown) with a gap therebetween to form a upwardly-angled, captured cutting slot. A bone saw blade12 (shown inFIG. 6) cutting along theelongated opening108 through one of the captured cutting slots will only, or at least mostly, contact the guide surfaces of the bearing inserts224,226 and not thebody202. In another embodiment, two or more separate bearing inserts may be used in place of themulti-sectioned bearing insert226. In yet another embodiment, any of the captured cutting slots may be formed by a single bearing insert functioning as an elongated bushing, rather than by a pair of opposed bearing inserts.
• Each bearing insert218-226 includes a plurality of chemically etchedholes234 which create adhesion between the bearing inserts218-226 and thebody202. The chemically etchedholes234 have the same distinctive structural characteristics as the chemically etchedholes134, described above with respect to theorthopaedic cutting block100 and shown inFIGS. 3A-D. As thebody202 is molded to the bearing inserts218-226, a portion of thebody202 at least partially fills the chemically etchedholes234. After molding, thebody202 contacts the bearing inserts218-226 at the interface surfaces236 and the sidewalls of the chemically etchedholes234, but generally does not contact the guide surfaces, providing substantially all metallic guide surfaces configured to support an orthopaedic cutting tool.
• The bearing inserts218-216 may also include other chemically etched features in addition to the chemically etchedholes234, such as chemically etched grooves or indicia. In one illustrative embodiment, a chemically etched groove may run the entire width of theinterface surface236 of thebearing insert226. This chemically etched groove would allow for bending of thebearing insert226 between the downwardly-facingsection228 and the upwardly-facingsection230 prior to molding of thebody202 to thebearing insert226.
• Placement and use of theorthopaedic cutting block200 on the distal end of the patient'sfemur10 during surgery can be best seen inFIG. 6. Typically, the surgeon will have performed a distal cut or resection on the patient'sfemur10 prior to using theorthopaedic cutting block200 to perform one or more of an anterior cut, a posterior cut, or a chamfer cut. Theorthopaedic cutting block200 is positioned such that the bone-facingsurfaces238 of thebody component204 and of thebody component206 rest on the resected distal surface of the patient'sfemur10. Theorthopaedic cutting block200 is secured to the patient'sfemur10 by the placement of one or more (typically, two)surgical pins16 through the guide holes216 of thebody component204 and thebody component206. Once theorthopaedic cutting block200 is secured, the surgeon may use a typical bone saw having a bone sawblade12 to perform an anterior resection using thebearing insert220 for support (shown completed), to perform a posterior resection using thebearing insert222 for support (also shown completed), or to perform two chamfer resections using the captured cutting slots, as shown inFIG. 6. When the surgeon uses one of the captured cutting slots, the bone sawblade12 is guided by the bearing inserts224,226, and avoids contact with thebody202, including the first pair of taperedwalls210.
• It should be noted that an orthopaedic surgical instrument according to the present disclosure may be embodied as additional or different orthopaedic cutting blocks, other than those discussed above. By way of illustrative example, a distal femoral cutting block might include an injection-molded body and a metallic bearing insert having a plurality of chemically etched holes and positioned to allow a surgeon to perform a distal cut on a patient's femur using the bearing insert for support. As a further illustrative example, a proximal tibial cutting block might include an injection-molded body and a metallic bearing insert having a plurality of chemically etched holes and positioned to allow a surgeon to perform a proximal cut on a patient's tibia using the bearing insert for support. Indeed, it is believed that there are few, if any, orthopaedic cutting blocks to which the principles of the present disclosure would not be applicable.
• Referring generally now toFIGS. 7-8, another illustrative embodiment of an orthopaedic surgical instrument according to the present disclosure is anorthopaedic cutting tool300 designed to function as drill bit for use by a surgeon with a surgical bone drill. Theorthopaedic cutting tool300 includes a plurality of metallic cutting inserts322 and abody302 molded to the plurality of cutting inserts322.
• Thebody302 oforthopaedic cutting tool300 may be formed of any material which may be molded to the plurality of cuttinginserts322, such as the materials discussed above with respect toorthopaedic cutting block100. In one illustrative embodiment, thebody302 of theorthopaedic cutting tool300 is formed of an injection-molded polymer. As shown inFIG. 7, thebody302 is generally cylindrical in shape, having a longitudinal axis L. Thebody302 may be a generally solid cylinder or may optionally includevoids312, such as those shown inFIG. 7, in order to decrease the amount of material used to create thebody302. Thebody302 includes acutting segment314, on which the plurality of cuttinginserts322 are disposed. Thebody302 may also include an integrally formedcoupling feature304, at the end opposite thecutting segment314 along the longitudinal axis L. Thecoupling feature304 may includenarrower sections306,wider sections308, and/or non-cylindrically-shapedsections310 to allow a typical surgical bone drill (not shown) to couple to theorthopaedic cutting tool300.
• The cuttingsegment314 of thebody302 oforthopaedic cutting tool300, which is shown in detail inFIG. 8, includes a plurality of cuttingflutes316. The plurality of cuttingflutes316 are arranged radially outward around the longitudinal axis L of theorthopaedic cutting tool300. Achannel318 is situated between each pair of adjacent cuttingflutes316 to allow bone fragments removed by theorthopaedic cutting tool300 to exit the patient's bone. In operation, a surgeon may couple theorthopaedic cutting tool300 to the surgical bone drill to cause rotation of thecutting segment314 about the longitudinal axis L in the direction of arrow R indicated inFIG. 8. The cuttingsegment314 of thebody302 may also include apointed tip320 to assist in guiding theorthopaedic cutting tool300.
• Similar to the bearing inserts118,120 oforthopaedic cutting block100, the cutting inserts322 of theorthopaedic cutting tool300 may be formed of a metal or metallic alloy. Each of the plurality of cuttinginserts322 is disposed on one of the plurality of cuttingflutes316 and is generally aligned with a leading edge of the cuttingflute316 on which it is disposed. It is also contemplated that some, but not all, of the plurality of cuttingflutes316 may have acutting insert322 disposed thereon. Each cuttinginsert322 includes aninterface surface328, which contacts thebody302. Opposite theinterface surface328, each cuttinginsert322 also includes awork surface324 which is configured to contact and remove portions of the patient's bone during rotation of theorthopaedic cutting tool300 in the direction of the arrow R.
• Each cuttinginsert322 includes a plurality of chemically etchedholes326 which create adhesion between the plurality of cuttinginserts322 and thebody302. The chemically etchedholes326 have the same distinctive structural characteristics as the chemically etchedholes134, described above with respect toorthopaedic cutting block100 and shown inFIGS. 3A-D. As thebody302 is molded to the cutting inserts322, a portion of thebody302 at least partially fills each of the plurality of chemically etchedholes326. After molding, thebody302 contacts the plurality of cuttinginserts322 at the interface surfaces328 and the sidewalls of the chemically etchedholes326, but generally does not contact the work surfaces324, providing substantially allmetallic work surfaces324 configured to remove portions of a patient's bone.
• Referring generally now toFIGS. 9-10, another illustrative embodiment of an orthopaedic surgical instrument according to the present disclosure is anorthopaedic cutting tool400 designed to function as a rasp for use by a surgeon in manually removing portions of a patient's bone. Theorthopaedic cutting tool400 includes ametallic cutting insert412 and abody402 molded to the cuttinginsert412.
• Thebody402 oforthopaedic cutting tool400 may be formed of any material which may be molded to themetallic cutting insert412, such as the materials discussed above with respect toorthopaedic cutting block100. In one illustrative embodiment, thebody402 of theorthopaedic cutting tool400 is formed of an injection-molded polymer. As shown inFIG. 9, thebody402 includes acutting segment404, on which thecutting insert412 is disposed. Thebody402 also includes an integrally formedhandle406, at the end opposite thecutting segment404, which may be gripped by the surgeon during use. Thehandle404 may be ergonomically shaped and thebody402 may also includebulges408 near the ends of thehandle406 so that theorthopaedic cutting tool400 may be more easily grasped by the surgeon. Thebody402 may be generally solid or may optionally includevoids410, such as those shown inFIG. 9, in order to decrease the amount of material used to create thebody402.
• The cuttingsegment404 of thebody402 oforthopaedic cutting tool400, which is shown in detail inFIG. 10, is molded to the cuttinginsert412. Similar to the bearing inserts118,120 oforthopaedic cutting block100, the cuttinginsert412 of theorthopaedic cutting tool400 may be formed of a metal or metallic alloy. The cuttinginsert412 includes aninterface surface422, which contacts thebody402. Opposite theinterface surface422, the cuttinginsert412 also includes awork surface414, which is configured to remove portions of the patient's bone during motion of theorthopaedic cutting tool400 in the direction of the arrow M indicated inFIG. 10. In operation, a surgeon may grip theorthopaedic cutting tool400 at thehandle406, place thework surface414 in contact with the patient's bone, and move to theorthopaedic cutting tool400 reciprocally in the direction of arrow M.
• The cuttinginsert412 includes a plurality of chemically etchedholes416 which create adhesion between the cuttinginsert412 and thebody402. The chemically etchedholes416 have the same distinctive structural characteristics as the chemically etchedholes134, described above with respect toorthopaedic cutting block100 and shown inFIGS. 3A-D. As thebody402 is molded to the cuttinginsert412, a portion of thebody402 at least partially fills each of the plurality of chemically etchedholes416. After molding, thebody402 contacts the cuttinginsert412 at theinterface surface422 and the sidewalls of the chemically etchedholes416, but generally does not contact thework surface414, providing substantially allmetallic work surface414 configured to remove portions of a patient's bone.
• To assist in the removal of portions of the patient's bone, thework surface414 of the cuttinginsert412 includes a plurality of chemically etched cuttingteeth418. In one illustrative embodiment, shown inFIG. 10, the plurality of chemically etched cuttingteeth418 are etched into thework surface414 of the cuttinginsert412 to have a cross-section consisting of two steps with sharp, generally right-angled edges configured to remove portions of the patient's bone. The chemically etched cuttingteeth418 span the entire width of the cuttinginsert412 and are arranged perpendicularly to the length of the cuttinginsert412. Thework surface414 also includes arelief surface420 situated between each pair of adjacent cuttingteeth412. In this embodiment, the plurality of chemically etchedholes416 extend from theinterface surface422 to the relief surfaces420 of the cuttinginsert412. It is contemplated that thework surface414 may take other forms, such as asingle relief surface420 with a plurality of chemically etched cuttingteeth418 raised above therelief surface420 and arranged in various patterns. Various configurations of thework surface414 may be formed by selectively exposing areas on one or both sides of the cuttinginsert412 to the chemical bath in a single or multi-step etching process, as discussed below.
• It should be noted that an orthopaedic surgical instrument according to the present disclosure may be embodied as additional or different orthopaedic cutting tools, in addition to those discussed above. By way of illustrative example, an orthopaedic surgical reamer might include an injection-molded body and a plurality of metallic cutting inserts having chemically etched holes and disposed at the cutting edges of the instrument to allow a surgeon to ream an intramedullary canal of a long bone using the cutting inserts. As a further illustrative example, an orthopaedic surgical broach might include an injection-molded body and a metallic cutting insert having chemically etched holes and cutting teeth to allow a surgeon to prepare a femur for placement of a femoral component during a hip arthroplasty. Indeed, it is believed that there are few, if any, orthopaedic cutting tools to which the principles of the present disclosure would not be applicable.
• Referring generally now toFIGS. 11-13, an illustrative embodiment of a method for manufacturing an orthopaedic surgical instrument according to the present disclosure is illustrated as a series of simplified flow diagrams. Themanufacturing process500 may be used to fabricate an orthopaedic cutting block, in which case one or more metallic bearing inserts would be used, or may be used to fabricate an orthopaedic cutting tool, in which case one or more metallic cutting inserts would be used. In describing the illustrative embodiments of this method, the term “insert(s),” without a modifier, shall be used to signify either one or more metallic bearing inserts or one or more metallic cutting inserts. Themanufacturing process500 includes a number of process steps502-512, as shown inFIG. 11.
• Themanufacturing process500 begins withprocess step502, in which the insert or inserts to be used in forming the orthopaedic surgical instrument are chemically etched to include a plurality of holes and any other desired features. The chemical etching may be performed with any chemical which dissolves metal, including, but not limited to, hydrochloric acid, ammonium persulfate, and ferric chloride. As will be described in more detail below with respect toFIG. 12,process step502 will include chemically etching a plurality of holes into the insert in every embodiment, but may also include etching additional features, including grooves, indicia, cutting teeth, and/or relief surfaces, in some illustrative embodiments.Process step502 may involve a single chemical etch or may involve multiple chemical etches, as needed.
• Afterprocess step502, themanufacturing process500 optionally proceeds to processstep504, in which the insert or inserts may be bent into the approximate shape needed for the orthopaedic surgical instrument, if necessary.Process step504 may be used when a single insert will occupy multiple planes in the finished surgical instrument. For instance, bearinginsert120 in orthopaedicsurgical block100 and bearinginsert226 in orthopaedicsurgical block200 is bent prior toprocess step506. Bending of the insert may be facilitated by one or more chemically etched grooves, such as thegroove136 described above and shown inFIG. 3B. The insert need only be bent to its approximate shape, asprocess step508 will further form the insert to the correct shape, as discussed below.
• Afterprocess step502, oroptional process step504, themanufacturing process500 proceeds to processstep506, in which the insert or inserts are loaded into a mold. In one illustrative embodiment, the insert is loaded into the mold such that a guide surface (if a bearing insert) or a work surface (if a cutting insert) contacts a wall or walls of the mold. The inserts may be held in place in the mold in a number of ways, including gravitational, magnetic, or other forces.
• Afterprocess step506, themanufacturing process500 proceeds to processstep508, in which the body material is injected into the mold. As discussed above, the body material may be any substance which may be molded to the inserts, including, but not limited to, polymers and resins. In some illustrative embodiments, the body material may be a substance which is less expensive, lighter, and/or more easily fabricated into complex shapes than the metallic inserts.Process step508 may include heating the body material to make the material suitable for injecting into the mold. Inprocess step508, the force of the body material injected into the mold presses the inserts to the walls of the mold, further shaping inserts which were bent duringoptional process step504 into the proper shape. A portion of the body material may at least partially fill the plurality of holes in the insert which were chemically etched inprocess step502. In some embodiments, the body material will substantially fill all of the holes in the insert. In other embodiments, many or most of the holes will be filled, while others will be left unfilled.
• Afterprocess step508, themanufacturing process500 proceeds to processstep510, in which the body material is allowed to set into its final, rigid form.Process step510 may involve allowing the heated body material to cool to a temperature lower than its temperature when injected into the mold. In some illustrative embodiments, the body material will reach the wall of the mold during injection inprocess step508 and be flush with the guide surface (if a bearing insert) or the work surface (if a cutting insert). Duringprocess step510, the body material may retract slightly while setting, resulting in the portion of the body only partially filling the hole, as shown in the cross-sections ofFIGS. 3C and 3D.
• Afterprocess step510, themanufacturing process500 proceeds to processstep512, in which a formed body and insert(s) are removed from the mold. At this point, another insert or set of inserts, which have been chemically etched according toprocess step502, may be loaded into the mold according toprocess step506 and the process may be repeated. It is also contemplated that themanufacturing process500 may include additional process steps. For instance, in some embodiments, after the formed body and insert(s) are removed from the mold inprocess step512, additional assembly of the orthopaedic surgical instrument may be required.
• One illustrative embodiment ofprocess step502 of themanufacturing process500 is shown in detail inFIG. 12 as a chemical etching sub-process consisting of process steps520-526. In every embodiment, thechemical etching sub-process502 will include chemically etching a plurality of holes into an insert. In some illustrative embodiments, thechemical etching sub-process502 may also include etching additional features, including grooves, indicia, cutting teeth, and/or relief surfaces into the insert. These features may be chemically etched into the insert along with the holes simultaneously, that is during a single iteration of thechemical etching sub-process502. Alternatively, the process steps520-526 may be repeated, as needed, to form the appropriate chemically etched features before returning tomanufacturing process500.
• Thechemical etching sub-process502 begins withprocess step520, in which a mask is formed on the insert or inserts. As shown in the cross-section ofFIG. 3A, themask14 is formed around the metal to be chemically etched into the inserts, but includes a plurality of exposedareas18. The mask may be formed from any material which is not substantially dissolved by the chemical bath ofprocess step522. As will be described in more detail below with respect toFIG. 13, one illustrative embodiment ofprocess step520 may include forming a layer of polymeric photoresist around the inserts to act as a mask during etching. The mask may be formed on one side, both sides, or neither side of the insert at various positions, depending on the desired feature at that position.
• Afterprocess step520, thechemical etching sub-process502 proceeds to processstep522, in which the insert or inserts having the mask or masks are placed in a chemical bath. The chemical bath may include any chemicals which dissolve the metal of the inserts, but do not substantially dissolve the mask material, including, but not limited to, hydrochloric acid, ammonium persulfate, and ferric chloride. Duringprocess step522, the chemical bath selectively attacks and dissolves the metal of the inserts at the plurality of exposed areas18 (FIG. 3A). As a wet, or liquid, chemical etch is isotropic in nature, the chemical bath dissolves the metal of the inserts in horizontal directions, as well as the vertical direction, resulting in the structures shown inFIG. 3B-D. Etching occurs in the horizontal directions at approximately 20-25% the rate of the vertical direction.
• Afterprocess step522, thechemical etching sub-process502 proceeds to processstep524, in which the insert or inserts having the mask or masks are removed from the chemical bath after a predetermined amount of time. In addition to the pattern of the mask applied inprocess step520, the form of the inserts will also be determined by the amount of time elapsed between process steps522 and524. If the chemical etch is allowed to proceed for approximately the time required to dissolve half the thickness of an insert, areas which were exposed to the chemical bath on both sides of the insert will result in a hole which extends through the entire thickness of the insert, while areas which were exposed to the chemical bath on only one side of the insert will result in a groove, as shown inFIG. 3B. If the chemical etch is allowed to proceed for approximately the time required to dissolve the entire thickness of an insert, areas which were exposed to the chemical bath on only one side of the insert will result in a hole with a tapered sidewall, similar in structure to that shown inFIG. 3D. It is contemplated that holes and other features of various other cross-sections may formed by chemically etching a particular distance into the insert from one side using a first mask, then repeating thechemical etching sub-process502 using a second mask and chemically etching the remainder of the thickness of the insert from the opposite side.
• Afterprocess step524, thechemical etching sub-process502 proceeds to processstep526, in which the mask applied inprocess step520 is removed from the insert or inserts. At this point, the chemically etchingsub-process502 may be repeated, if necessary, or themanufacturing process500 may proceed to one ofprocess step504 orprocess step506. It should also be noted that thechemical etching sub-process502 may be applied to one insert at a time, or multiple inserts may be chemically etched in parallel. In one illustrative embodiment, a large metallic sheet of appropriate thickness, containing multiple rows and columns of inserts, may proceed through thechemical etching sub-process502. The mask formed inprocess step520 may include an outline around all or substantially all of each insert, such that the inserts either fall out of the sheet during chemical etching or may be easily removed afterward.
• One illustrative embodiment of theprocess step520 of thechemical etching sub-process502 is shown in detail inFIG. 13 as a mask forming sub-process consisting of process steps530-536. Themask forming sub-process520 is a photolithography process in which one or more patterned photomasks are used to form a light-sensitive material into a mask having a plurality of exposed areas on the insert or inserts.
• Themask forming sub-process520 begins withprocess step530, in which a photoresist material is applied to substantially cover the exterior of the insert or inserts. The photoresist material is a polymeric substance which changes its structure in response to exposure to an ultraviolet (“UV”) light source. The coating of photoresist material may be a positive photoresist, which becomes more soluble when exposed to UV light. Alternatively, the coating of photoresist material may be a negative photoresist, which becomes polymerized and less soluble when exposed to UV light. The coating of photoresist material may be applied in numerous ways, including high-velocity spin coating. The photoresist material may also need to be heated slightly before becoming light-sensitive.
• Afterprocess step530, the mask forming sub-process520 proceeds to processstep532, in which a first patterned photomask is positioned between a UV light source and a first side of the insert covered in photoresist material. The first patterned photomask includes both translucent and opaque portions. If a positive photoresist is used inprocess step530, the translucent portions of the photomask will correspond to the plurality of exposedareas18 in the mask14 (FIG. 3A). If a negative photoresist is used inprocess step530, the opaque portions of the photomask will correspond to the plurality of exposedareas18 in the mask14 (FIG. 3A).
• Afterprocess step532, the mask forming sub-process520 proceeds to processstep534, in which the UV light source is turned on and areas of the photoresist material are selectively exposed to the light source through the translucent portions of the first patterned photomask. In response, the chemical structure of the exposed areas of photoresist will change, becoming more or less soluble depending on the type of photoresist used. Process steps530 and532 may be repeated using a second photomask and a second side of the insert, if needed. Alternatively, the first and second photomasks may be positioned at the same time, each with its own light source, and the first and second sides of the insert may be exposed simultaneously.
• Afterprocess step534, the mask forming sub-process520 proceeds to processstep536, in which a developer is applied to the insert to selectively remove areas of the photoresist material to define the plurality of exposed areas on the insert. The developer is a chemical solution which dissolves the more soluble areas of the photoresist material, but not the less soluble areas. The developer may be applied in numerous ways, including high-velocity spin coating. After developing, the remaining photoresist material may again need to be heated to harden into a mask that can withstand the chemical bath. At this point, themask forming sub-process520 is complete, and the chemically etchingsub-process502 may proceed to processstep522.
• While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.
• There are a plurality of advantages of the present disclosure arising from the various features of the apparatus and method described herein. It will be noted that alternative embodiments of the apparatus and methods of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of the apparatus and methods that incorporate one or more of the features of the present invention and fall within the spirit and scope of the present disclosure as defined by the appended claims.

Claims (20)

1. An orthopaedic cutting tool, comprising:

a metallic cutting insert having a plurality of chemically etched holes, the cutting insert being configured to remove portions of a patient's bone; and

a body molded to the cutting insert such that each of the plurality of chemically etched holes is at least partially filled by a portion of the body.

2. The orthopaedic cutting tool ofclaim 1, wherein:

the cutting insert has (i) an interface surface which contacts the body, and (ii) a work surface opposite the interface surface, the work surface configured to remove portions of the patient's bone; and

each of the plurality of chemically etched holes extends from the interface surface to the work surface of the cutting insert.

3. The orthopaedic cutting tool ofclaim 2, wherein the portion of the body which at least partially fills each chemically etched hole fills at least half the volume of the hole.

4. The orthopaedic cutting tool ofclaim 1, wherein the cutting insert has (i) a plurality of cutting teeth configured to remove portions of the patient's bone, (ii) at least one relief surface between the plurality of cutting teeth, and (iii) an interface surface opposite the plurality of cutting teeth and the at least one relief surface, the interface surface contacting the body.

5. The orthopaedic cutting tool ofclaim 4, wherein each of the plurality of chemically etched holes extends from the interface surface to the at least one relief surface of the cutting insert.

6. The orthopaedic cutting tool ofclaim 5, wherein the portion of the body which at least partially fills each chemically etched hole fills at least half the volume of the hole.

7. The orthopaedic cutting tool ofclaim 1, wherein the body includes an integrally formed coupling feature.

8. The orthopaedic cutting tool ofclaim 1, wherein in the body includes an integrally formed handle portion.

9. The orthopaedic cutting tool ofclaim 1, wherein the body comprises an injection-molded polymer.

10. An orthopaedic surgical instrument, comprising:

an orthopaedic cutting tool having (i) a plurality of metallic cutting inserts, each cutting insert having a plurality of chemically etched holes and being configured to remove portions of a patient's bone, and (ii) a body molded to the plurality of cutting inserts such that each of the plurality of chemically etched holes is at least partially filled by a portion of the body.

11. The orthopaedic surgical instrument ofclaim 10, wherein:

each of the plurality of cutting inserts has (i) an interface surface which contacts the body, and (ii) a work surface opposite the interface surface, the work surface configured to remove portions of the patient's bone; and

each of the plurality of chemically etched holes extends from the interface surface to the work surface of the respective cutting insert.

12. The orthopaedic surgical instrument ofclaim 10, wherein:

the body includes a plurality of cutting flutes, the plurality of cutting flutes arranged radially outward around a longitudinal axis of the orthopaedic cutting tool; and

each of the plurality of cutting inserts is disposed on one of the plurality of cutting flutes.

13. The orthopaedic surgical instrument ofclaim 12, wherein each of the plurality of cutting inserts is aligned with a leading edge of one of the plurality of cutting flutes to allow a surgeon to remove portions of the patient's bone by rotating the orthopaedic cutting tool about the longitudinal axis.

14. A method for manufacturing an orthopaedic surgical instrument, the method comprising:

chemically etching a plurality of holes into a metallic cutting insert; and

molding a body to the cutting insert to form an orthopaedic cutting tool.

15. The method for manufacturing an orthopaedic surgical instrument ofclaim 14, wherein chemically etching the plurality of holes into the cutting insert comprises chemically etching each of the plurality of holes through the entire thickness of the cutting insert.

16. The method for manufacturing an orthopaedic surgical instrument ofclaim 14, wherein chemically etching the plurality of holes into the cutting insert comprises:

forming a mask on the cutting insert, the mask defining a plurality of exposed areas;

placing the cutting insert having the mask in a chemical bath whereby the plurality of exposed areas are chemically etched into the plurality of holes;

removing the cutting insert having the mask from the chemical bath; and

removing the mask from the cutting insert.

17. The method for manufacturing an orthopaedic surgical instrument ofclaim 16, wherein forming the mask on the cutting insert comprises:

applying a photoresist material to the cutting insert;

selectively exposing portions of the photoresist material to a light source using a patterned photomask; and

selectively removing portions of the photoresist material using a developer to define the plurality of exposed areas on the cutting insert.

18. The method for manufacturing an orthopaedic surgical instrument ofclaim 14, wherein molding the body to the cutting insert comprises:

loading the cutting insert into a mold, the cutting insert contacting a wall of the mold; and

injecting a polymer into the mold such that the cutting insert is pressed against the wall of the mold by the polymer and the polymer at least partially fills the plurality of holes.

19. The method for manufacturing an orthopaedic surgical instrument ofclaim 14, further comprising chemically etching a plurality of cutting teeth into the cutting insert.

20. The method for manufacturing an orthopaedic surgical instrument ofclaim 19, wherein the plurality of holes and the plurality of cutting teeth are chemically etched simultaneously.

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