Patent Application
20100191246
1. Field of the Invention
The present invention relates to orthopaedic implants. More particularly, the present invention relates to a tool and method for implanting an acetabular cup of the type used in a hip arthroplasty procedure, for example.
2. Description of the Related Art
Orthopaedic implants are commonly used to replace some or all of a patient's hip joint to restore or increase use of the hip joint following a traumatic injury or deterioration due to aging or illness, for example. During a hip replacement procedure, a prosthetic femoral component may be used to replace a portion of the patient's femur and a prosthetic acetabular component may be used to replace a portion of the patient's pelvis. The femoral component may include a stem portion, a neck portion, and a head portion. The stem portion may be positioned within the prepared femoral canal of the patient's femur and secured via bone cement or by a press-fit. The neck portion extends between the stem portion and the head portion. The head portion articulates within the prosthetic acetabular component, and may be constructed of metal or ceramic, for example.
Known prosthetic acetabular components generally include a cup portion and a liner portion, each having a substantially hemispherical shape. The cup portion may be constructed of metal and may be implanted by inserting one or more screws through holes in the hemispherical inner surface of the cup and into the surrounding bone of the patient's pelvis. After the cup portion is implanted, the liner portion, which may be constructed of a polymer, is fitted in place within the metal cup portion by suitable mechanical fasteners or by a snap-fit engagement, for example. The polymer liner portion then receives the metal head portion of the prosthetic femoral component, to provide “metal-on-poly” articulation.
Other known prosthetic acetabular components generally include a “monoblock” cup, which is constructed substantially entirely of metal. Such cups include metallic articulating surfaces for receiving the metal or ceramic head portion of the prosthetic femoral component, to provide “metal-on-metal” or “ceramic-on-metal” articulation.
The present invention provides a tool and method for implanting an acetabular cup having external screw retention features.
According to an embodiment of the present invention, an orthopaedic tool is provided for implanting a prosthetic socket. The prosthetic socket includes a substantially hemispherical body having a convex exterior surface defining an outer periphery of the prosthetic socket, a concave interior articulating surface, and a rim extending between the convex exterior surface and the concave interior articulating surface near a top portion of the prosthetic socket. The orthopaedic tool includes a shaft configured to couple to the prosthetic socket and a first pin having an end. The first pin is coupled to the shaft for movement relative to the shaft above the rim of the prosthetic socket from a first position in which the end of the first pin is located within the outer periphery of the prosthetic socket to a second position in which the end of the first pin is located beyond the outer periphery of the prosthetic socket.
According to another embodiment of the present invention, an orthopaedic system is provided including a prosthetic socket and a tool. The prosthetic socket includes a substantially hemispherical body that defines a polar region and an equatorial region located above the polar region. The body of the prosthetic socket includes a convex exterior surface that defines an outer periphery of the prosthetic socket, a concave interior articulating surface, and a longitudinal axis. The tool includes a shaft configured to couple to the prosthetic socket and a first pin having an end. The first pin is coupled to the shaft for movement relative to the shaft above the equatorial region of the prosthetic socket from a first position in which the end of the first pin is located within the outer periphery of the prosthetic socket to a second position in which the end of the first pin is located beyond the outer periphery of the prosthetic socket.
According to yet another embodiment of the present invention, a method is provided for implanting a prosthetic socket. The prosthetic socket includes a substantially hemispherical body that defines a polar region and an equatorial region located above the polar region, and the body includes a convex exterior surface, a concave interior articulating surface, and at least one screw retention element. The method includes the steps of positioning the convex exterior surface of the prosthetic socket against a bone, and inserting a first pin of a tool into a first location of the bone above the equatorial region of the prosthetic socket and adjacent to the prosthetic socket.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Orthopaedic implants of the type used in hip arthroplasty procedures, such as prosthetic femoral hip stems and acetabular cups, may be implanted according to surgical techniques described in U.S. Pat. No. 6,676,706, issued Jan. 13, 2004; U.S. Pat. No. 6,860,903, issued Mar. 1, 2005; U.S. Pat. No. 6,953,480, issued Oct. 11, 2005; U.S. Pat. No. 6,991,656, issued Jan. 31, 2006; abandoned U.S. patent application Ser. No. 10/929,736, filed Aug. 30, 2004; abandoned U.S. patent application Ser. No. 10/952,301, filed Sep. 28, 2004; currently pending U.S. patent application Ser. No. 11/235,286, filed Sep. 26, 2005; and currently pending U.S. patent application Ser. No. 11/105,080, filed Apr. 13, 2005, all titled METHOD AND APPARATUS FOR PERFORMING A MINIMALLY INVASIVE TOTAL HIP ARTHROPLASTY and all assigned to the assignee of the present application, the disclosures of which are hereby expressly incorporated herein by reference.
Referring to
Acetabular cup 10 may be constructed entirely or substantially entirely of a suitable metal, such as titanium, a titanium alloy, or a cobalt-chromium-molybdenum alloy, for example. As shown in
Acetabular cup 10 also includes a convex, dome-shaped exterior bone-contacting surface 16, and a concave, hemispherical interior articulating surface 18, and rim 17 that extends between bone-contacting surface 16 and articulating surface 18. Articulating surface 18 may be constructed entirely or substantially entirely of a suitable metal. The concave articulating surface 18 defines socket 19 that may be configured to receive the head portion of a prosthetic femoral component (not shown) or a polymeric bearing liner (not shown), for example. As shown in
Acetabular cup 10 further includes a plurality of external screw retention elements 20, 22, disposed about the periphery of acetabular cup 10 and radially offset from longitudinal axis 15. As used herein, “screw retention elements” are elements against which a bone fixation screw, such as screw 30, can act to secure acetabular cup 10 to pelvis P. The bone fixation screw may be a self-tapping screw, or alternatively, a non-self tapping screw inserted through pilot holes formed by a suitable tap. Also, as used herein, “external” refers to a location outside the concave, interior articulating surface 18 of acetabular cup 10, against which a bearing liner or femoral head may be positioned. Thus, as shown in
Screw retention elements 20, 22, may be configured to receive various types of bone fixation screws 30. For example, the shaft of bone fixation screw 30 may extend between fins 24 of screw retention elements 20a, 20b, 20c, 20d, with the head of screw 30 resting against fins 24. Screw retention elements 20a, 20b, 20c, 20d, may be used to orient bone fixation screw 30 at a desired angular orientation with respect to acetabular cup 10. As another example, screw retention elements 22a, 22b, 22c, may extend through flange 26 that projects from equatorial region 14 of acetabular cup 10. Screw retention elements 22a, 22b, 22c, may be threaded to engage a threaded head of bone fixation screw 30, for example. Screw retention elements 22a, 22b, 22c, may be used to locate bone fixation screw 30 in a fixed angular orientation with respect to acetabular cup 10.
The location of the screw retention elements 20, 22, may be selected to correspond with desired areas of pelvis P. According to an exemplary embodiment of the present invention, bone fixation screws 30 may be inserted through screw retention elements 20, 22, and screwed into desired areas of pelvis P that have adequate bone stock for anchoring acetabular cup 10 to pelvis P. For example, in the illustrated embodiment of
In use, the acetabulum of pelvis P is prepared, such as by reaming. Then, acetabular cup 10 is placed within the prepared acetabulum to align screw retention elements 20, 22, with the desired anatomical landmarks of pelvis P, as described above. For example, acetabular cup 10 may be positioned within the prepared acetabulum such that screw retention elements 20a, 20b, 20c, 20d, are aligned with ischium Is and pubis Pb of pelvis P, and screw retention elements 22a, 22b, 22c, of flange 26 are aligned with ilium Il of pelvis P. After acetabular cup 10 is properly aligned, a surgeon may press-fit the prosthesis into the prepared acetabulum of pelvis P, such as by using an impaction tool or a ball pusher, for example. Acetabular cup 10 may then be secured to pelvis P, such as by inserting bone fixation screw 30 into pelvis P.
The present invention provides a method of stabilizing acetabular cup 10 in pelvis P during securement, such as during insertion of bone fixation screw 30. In general, the method involves inserting at least one pin, such as a Kirschner wire or another suitable pin, into a location of pelvis P that is above acetabular cup 10 and radially opposite from a force applied during screw insertion. This method may prevent acetabular cup 10 from lifting away from pelvis P during screw insertion. The pins may be driven into pelvis P with a mallet, for example. Also, a suitable orthopaedic tool, such as tool 40 or tool 40′ described below, may be used to stabilize acetabular cup 10 in pelvis P during securement.
Referring to
Tool 40 further includes at least one pin 46 coupled to shaft 42. In the illustrated embodiment, tool 40 includes two pins 46 extending in parallel. As pins 46 are moved into a locking position, pins 46 extend substantially transversely, or non-parallel, to shaft 42. Each pin 46 may include a sharp, pointed end 47, that is configured to be driven into bone. For example, end 47 of each pin 46 may include a pointed Kirschner wire or another suitable device that is configured to be driven into bone.
As shown in
In use, tool 40 may be pressed against acetabular cup 10. As shown in
Next, the surgeon may align ends 47 of pins 46 with bone surrounding acetabular cup 10. Ends 47 of pins 46 may be aligned with bone that is located radially opposite from a desired screw retention element 20, 22. As shown in phantom in
After pins 46 are properly aligned with the bone of pelvis P, the surgeon may force arm 48 downward relative to shaft 42 toward projection 45 of tool 40 and toward equatorial plane 11 of acetabular cup 10, as shown in solid in
With pins 46 secured in the bone, bone fixation screws 30 may be driven through screw retention elements 20, 22, and into the bone of pelvis P. For example, as shown in
Tool 40 is provided to stabilize acetabular cup 10 in pelvis P during screw insertion. As discussed above, screw retention elements 20, 22, may be radially offset from longitudinal axis 15 of acetabular cup 10, which is assumed to generally coincide with the center of gravity of acetabular cup 10. Therefore, applying a force to screw retention elements 20, 22, such as when tightening bone fixation screw 30 in place, may cause acetabular cup 10 to lift out of the prepared acetabulum of pelvis P. The force F applied to acetabular cup 10 when tightening bone fixation screw 30 in screw retention element 22b is illustrated schematically in
After inserting bone fixation screw 30 through acetabular cup 10 and into pelvis P, pins 46 of tool 40 may be removed from pelvis P and rotated in preparation for inserting another screw. According to an exemplary embodiment of the present invention, pins 46 of tool 40 may be rotated toward the bone of pelvis P that is located radially opposite from the next screw retention element 20, 22. In one embodiment, with projection 45 of tool 40 secured in bore 52 of acetabular cup 10, arm 48 of tool 40 may be rotated relative to shaft 42 to rotate pins 46. In another embodiment, projection 45 of tool 40 may be removed from bore 52 of acetabular cup 10, and handle 44 of tool 40 may be rotated to rotate pins 46.
Referring next to
Tool 40′ further includes at least one pin 46′ coupled to shaft 42′. In the illustrated embodiment, tool 40′ includes two pins 46′ extending in parallel. Pins 46′ extend essentially perpendicular to shaft 42′. Each pin 46′ may include a sharp, pointed end 47′, that is configured to be driven into bone. For example, end 47′ of each pin 46′ may include a Kirschner wire or another suitable device that is configured to be driven into bone.
As shown in
In use, tool 40′ may be pressed against acetabular cup 10. As shown in
Next, the surgeon may align ends 47′ of pins 46′ with bone surrounding acetabular cup 10. Ends 47′ of pins 46′ may be aligned with bone that is located radially opposite from a desired screw retention element 20, 22. As shown in phantom in
After pins 46′ are properly aligned with the bone of pelvis P, the surgeon may drive ends 47′ of pins 46′ beyond the outer periphery of acetabular cup 10 defined by exterior bone-contacting surface 16 and into the bone of pelvis P, as shown in solid in
With pins 46′ secured in the bone, bone fixation screws 30 may be driven through screw retention elements 20, 22, and into the bone of pelvis P. For example, as shown in
Like tool 40, tool 40′ is provided to stabilize acetabular cup 10 in pelvis P during screw insertion. The force F applied to acetabular cup 10 when tightening bone fixation screw 30 in screw retention element 22b is illustrated schematically in
After inserting a bone fixation screw 30 through acetabular cup 10 and into pelvis P, pins 46′ of tool 40′ may be removed from pelvis P and rotated in preparation for inserting another screw. According to an exemplary embodiment of the present invention, pins 46′ of tool 40′ may be rotated toward the bone of pelvis P that is located radially opposite from the next screw retention element 20, 22. In one embodiment, with projection 45′ of tool 40′ secured in bore 52 of acetabular cup 10, arm 48′ of tool 40′ may be rotated relative to shaft 42′ to rotate pins 46′. In another embodiment, projection 45′ of tool 40′ may be removed from bore 52 of acetabular cup 10, and handle 44′ of tool 40′ may be rotated to rotate pins 46′.
While this invention has been described as having exemplary designs, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
