Bone graft delivery system

Abstract: A surgical technique for the delivery of bone graft to a medullary canal and implantation of a prosthetic device (35) includes placing bone graft into an elongate hollow tube (10) and arranging a plunger (20) having an elongate rod portion (21) into the hollow tube (10). The hollow tube (10), bone graft and plunger (20) assembly are inserted into the medullary canal which has been prepared for the assembly by reaming the medullary canal with a reamer corresponding in size to the hollow tube (10). The hollow tube (10) is withdrawn from the medullary canal while the plunger (20) is pushed into the canal, resulting in bone graft exiting the hollow tube (10) and being packed by the plunger (20). A trial prosthesis (30) is used to shape the bone graft within the canal for the prosthesis (35). Space for a cement mantle can be left through the use of an appropriately sized trial prosthesis (30).

Description: The present invention relates generally to a method of preparing instruments for bone graft for insertion into a graft receiving area, as well as to an instrument suitable for use in said method. It is known to use bone graft to prepare a seat for a prosthesis, either with or without a cement mantle. A bone grafting procedure is often used where there is an appreciable loss of strong bone stock, as is often the case in revision surgery (in which a previously implanted prosthesis is replaced with a new prosthesis). The seat prepared with bone graft may be made up entirely of bone graft to substantially surround a prosthesis, or the seat may be made up of bone graft and the natural bone at the implantation site (for instance, where bone graft is used to fill a relatively small void in the natural bone where the bone is otherwise intact). Bone graft typically includes crushed bone (cancellous and cortical), or a combination of these (and/or other natural materials) and synthetic biocompatible materials. Bone graft of this type is intended to stimulate growth of healthy bone. As used herein, "bone graft" shall mean materials made up entirely of natural materials, entirely of synthetic biocompatible materials, or any combination of these materials. U.S. Patent No. 5,015,256 to Bruce discloses a surgical technique by which the medullary canal is reamed and filled with bone graft, the bone graft being compacted by driving the stem of the prosthesis into the medullary canal. Also, U.S. Patent No. 4,800,875 to Ray discloses a method of inserting bone graft into a bone and tamping the bone graft. European Patent Publication No. 0 179 626 A discloses the use of bone graft to enhance implant/bone contact, whereby the stem of a hip implant is intended to subside within an implant sleeve. Also, an article entitled "Histology Of Cancellous Impaction Grafting In The Femur," by Ling et al., Journal of Bone and Joint Surgery [Br], Vol. 75-B, No. 5, September 1993, reports a 1988 revision of a hip implant in which allograft chips were impacted within the medullary canal with an oversized stem, followed by use of cement and implantation of a polished-surface stem. In addition, Complications of Total Hip Arthoplasty , by Richard H. Rothman and William J. Hozack, W.B. Saunders Co., 1988, teaches a technique of bone grafting in the femoral canal in a revision surgery, using uncemented components. Of course, it is desirable to properly prepare the medullary canal adjacent a joint for receiving bone graft so that a prosthesis can be properly positioned during implantation. Thus, the preparation of the medullary canal and the positioning of the prosthesis or trial prosthesis in the prepared medullary canal are often critical steps in properly implanting a prosthesis. To this end, rasps having a configuration similar to the prosthesis are well-known, as shown, for example, in U.S. Patent No. 3,874,003 to Moser (FIG. 8), U.S. Patent No. 4,306,550 to Forte and U.S. Patent No. 4,552,136 to Kenna. These devices facilitate the proper shaping of the femoral medullary canal in a configuration which is similar to their respective hip prostheses or trial hip prostheses. Centering devices (rods and guidewires) are also known for controlling the machining or other preparation of the medullary canal, as well as for centering a trial prosthesis during trial reduction or centering a prosthesis during implantation. U.S. Patent No. 4,919,673 to Willert, U.S. Patent No. 4,994,085 to Sawai and U.S. Patent No. 5,078,746 to Garner each disclose the use of centering rods in the distal femoral canal to center hip joint prostheses and/or trial hip joint prostheses during trial reduction and final implantation. The hip joint prostheses and trial hip joint prostheses each have longitudinal passageways which receive the centering rods or guidewires already in the canal. Centering rods or guidewires are also used in connection with machining and shaping instruments so that the preparation of the canal is controlled about the centering rod or guidewire and so that the preparation is consistent from instrument to instrument. U.S. Patent No. 4,341,206 to Perrett, U.S. Patent No. 4,751,922 to DiPietropolo, U.S. Patent No. 5,192,283 to Ling, U.S. Patent No. 5,122,134 to Borzone and U.S. Patent No. 5,190,548 to Davis disclose cannulated reamers and drills which are used with centering rods or guidewires for centering or positioning the shaping tools during preparation of a medullary canal or bone. U.S. Patent No. 5,192,283 to Ling also discloses the use of a trial hip prosthesis having a longitudinal passageway for receiving the very guidewire which facilitated the reaming and rasping of the canal. Bone graft is inserted into the canal around the guidewire, and the cannulated trial prosthesis is used to simultaneously compact and form or shape a prosthesis-receiving cavity larger than and similar in shape to the new prosthesis. Bone graft is continuously placed into the canal during the use of the cannulated trial prosthesis in order to build up the bone graft in the canal. A series of successively larger cannulated trial prostheses could be used to compact the bone graft. The technique described in Ling is a somewhat time-consuming surgical procedure. Factors which add to the time-consuming nature of this technique include the steps which must be repeated to complete the insertion of bone graft into the canal and the requirement that all steps take place in the medullary canal. In addition, the technique described in Ling relies on a guidewire which could shift during preparation of the canal. EP-A-0 470 393 relates to an injection device for injecting granulated bone cement soaked in the blood of the patient. The device includes a housing in which the bone cement is provided and a porous cover on the housing. The housing is dipped into the blood of the patient and a piston in the housing is withdrawn to suck the blood into the housing to soak the cement granulate. US-A-3 740 769 is entitled a prosthesis for hip joints. The hip joint may be held in position by the use of bone chips packed around the stem of the prosthesis when the prosthesis is inserted in the medullary canal. The present invention provides an easily implemented and efficient technique for preparing instruments for delivering bone graft for use in the delivery of bone graft to a medullary canal or elsewhere in the body. One embodiment relates specifically to bone grafting within the medullary canal adjacent a joint to prepare the canal for receiving a prosthesis. The present invention is directed to the preparation of instruments for delivery of bone graft materials to any area of the body and in particular to the medullary canal of any bone. The invention can be used in the repair of a bone or in connection with the implantation of prosthetic devices at any bone in the body, including without limitation the hip, knee and spinal joints. Further, the present invention can be used in primary surgery, in which a prosthesis is being used to reconstruct a joint for the first time, as well as in revision surgery, in which a previously-implanted prosthesis is being replaced with another prosthesis. Press fit, cement or other fixation techniques can be employed in conjunction with the present invention. The technique in accordance with the present invention is suitable for use in the delivery of bone graft into the medullary canal to fully or partially line the medullary canal. It is an object of the present invention to provide a bone graft delivery system for delivering bone graft, in a partially formed, fully formed or unformed condition to a graft receiving area in a body. The graft receiving area can be any area, but is often the medullary canal of a bone. The bone graft can be delivered in a partially formed manner. It is another object of the present invention to provide a method and apparatus by which a hollow tube and a plunger associated with the hollow tube are provided to facilitate delivery of the bone graft to a bone graft receiving area. In the preferred embodiment, positioning structure is provided on the plunger to maintain the plunger in a desirable position with respect to the hollow tube. Adjunct positioning means may also be provided to ensure that the plunger remains in the desirable position during the packing of bone graft into the hollow tube. It is another object of the present invention to provide a method and apparatus by which a plunger and hollow tube assembly can be packed with bone graft, and then together inserted into the medullary canal or adjacent to another bone graft receiving area. Subsequently, the hollow tube can be withdrawn to leave the plunger in place in order to form in the bone graft a cavity in the shape of the plunger. The plunger can then be removed, and a series of sequentially larger trials can be used to shape the bone graft within the medullary canal. It is another object of the present invention to provide a bone graft delivery system, by which bone graft can be selectively and controllably delivered to a specific area. For instance, bone graft may be delivered to one portion of the wall in the medullary canal, as opposed all of the walls in the medullary canal. It is another object of the present invention to provide a hollow tube and plunger assembly, in which the hollow tube is disposable. It is another object of the present invention to provide a bone graft delivery system, by which a hollow tube and possibly a hollow tube/plunger assembly can be prepared prior to even opening a patient, thus minimizing the overall impact of the grafting aspect of a surgical implantation or other procedure. The method and apparatus of the present invention may be used in a method whereby access is provided to a graft receiving area in a body, bone graft is placed into a hollow tube having a first end and a second end, the hollow tube, together with the bone graft, is arranged so that the first end of the hollow tube is at least adjacent to the graft receiving area, and the hollow tube is moved away from the graft receiving area, in a direction from the first end to the second end of the hollow tube, such that the bone graft exits the first end of the hollow tube and remains at the graft receiving area. A graft retaining structure may also be provided to block an end of the hollow tube, so as to facilitate the exit of the bone graft from the hollow tube. The graft retaining structure may also be used in such a way that it is maintained in one position while the tube is moved away from the graft receiving area. Alternatively, the graft retaining structure can be used by forcing it toward the graft receiving area, while the hollow tube is being moved away from the graft receiving area. The instruments of the present invention may also be used in a method involving exposing the medullary canal of a bone, placing bone graft into a hollow tube having a first end and a second end, inserting the first end of the hollow tube into the medullary canal, and withdrawing the hollow tube from the medullary canal, such that bone graft exits the first end of the hollow tube into the medullary canal. Again, the bone graft can be forced from the hollow tube by blocking an end of the hollow tube. The above technique may also include arranging a plunger having an elongate rod portion at least partially in the hollow tube and removing the plunger from the medullary canal to leave a cavity formed at least partially in the bone graft. The hollow tube can be inserted into the medullary canal together with the plunger and bone graft, and upon withdrawal of the hollow tube from the medullary canal, the plunger remains at least partially in the canal. Pressure can be applied to the plunger during withdrawal of the hollow tube to at least maintain the plunger at least partially in the medullary canal. Further pressure may also be applied to the plunger to force the plunger further into the medullary canal, either while withdrawing the hollow tube from the medullary canal or subsequent to the withdrawal of the hollow tube, whereby the bone graft deposited in the medullary canal would be further packed by the plunger. The bone graft deposited in the medullary canal by the tube/plunger assembly can be shaped, if not already shaped, with a prosthesis or a trial prosthesis having a configuration similar to the prosthesis to be implanted. The bone graft material in the medullary canal can be compacted with successively larger trial prostheses to progressively shape the bone graft. If the prosthesis to be implanted is to be cemented in place in the canal, the final trial prosthesis used to shape the bone graft can be of a size larger than the prosthesis to be implanted, so as to leave a cement mantle. The plunger used in connection with the hollow tube can be modular in nature, such that different portions of the plunger can be matched according to preoperative or intraoperative indications. Also, any positioning devices or graft retaining structures used in connection with the plunger can also be modular and selectable from a group of different devices to fit the particular application and hollow tube. The present invention may also be carried out by providing a hollow tube having a first end and a second end, and being constructed so that it can receive bone graft, and so that the first end can be arranged at least adjacent to a bone graft receiving area, and so that bone graft can be delivered from the first end of the hollow tube to the bone graft receiving area upon movement of the hollow tube in a direction from the first end to the second end. A graft retaining structure can also be provided for use in connection with the hollow tube, as can a graft packer. In addition, a plunger can be provided with the hollow tube. Another aspect of the present invention can be carried out by providing an extractor to facilitate the controlled movement of a tube which surrounds a rod, while leaving the rod substantially in position, the extractor including a housing, a connector for connecting the housing to the tube, a stem movable within the housing for applying pressure to a rod in its arranged position, and actuating means for applying pressure to such a rod. The stem may have a rod-engaging portion sized to engage a rod in a tube and to permit the tube to be withdrawn from around the rod so that the tube is disposed around the stem. The extractor is constructed and arranged so that upon actuation thereof, the stem applies pressure against the rod, and the housing, with a connected tube, is moved away from the arranged position, while leaving the rod in the arranged position. The foregoing and other objects of the present invention will become apparent, as will a better understanding of the concepts underlying the present invention, by reference to the description which follows and refers to the accompanying drawings in which: FIG. 1 is an elevational view of a hollow intramedullary tube and an associated extraction cap in accordance with an embodiment of the present invention; FIG. 2 is an elevational view of a plunger rod in accordance with an embodiment of the present invention; FIG. 3. is an elevational view of a modular plunger rod and associated modular centering devices, in accordance with another embodiment of the present invention; FIG. 4 is an elevational view of a hollow bone graft packer in accordance with the present invention; FIG. 5 is an elevational view of a plunger rod assembled within a hollow intramedullary tube (with extraction cap), illustrating in particular the packing of the tube/plunger assembly with bone graft through the use of a hollow bone graft packer; FIGS. 6A-6F are elevational views, in partial cross-section of an implant technique, illustrating in particular the delivery of bone graft to the proximal femoral medullary canal and the formation of the implant-receiving cavity within the graft-lined medullary canal; FIG. 7A is a top plan view of a tube extractor (a modified cement injector) in accordance with the present invention; FIG. 7B is an elevation view in partial cross-section of the bone graft delivery technique, illustrating in particular the use of a tube extractor (associated with the extraction cap) to remove the hollow intramedullary tube from the medullary canal while leaving the plunger rod with the packed bone graft in place; FIG. 8 is an elevational view of a plunger rod assembled within a hollow intramedullary tube, illustrating in particular adjunct centering means in the form of diametrically opposed centralizing screws; FIG. 9 is an elevational view of a plunger rod assembled within a hollow intramedullary tube, illustrating in particular adjunct centering means in the form of a slideable centralizing washer held on the rod by an interference fit; and FIG. 10 is an elevational view, in partial cross-section, showing the selective delivery of bone graft to a specific area of the medullary canal through the use of a specifically structured plunger rod. FIGS. 1-4 illustrate some of the instruments which may be used to facilitate the delivery of bone graft . The instruments illustrated are for the delivery of bone graft to the femoral medullary canal, but the concepts underlying the present surgical technique may be applied to the delivery of bone graft to the medullary canal of any bone, adjacent to or remote from any joint. FIG. 1 shows a hollow intramedullary tube 10 and an extraction cap 12 in accordance with the present invention. The tube is preferably hollow from one end to the other, but may be partially hollow depending upon the application and structure of the instruments used with it. (The word "hollow" will thus be used in this sense.) The tube 10 is preferably made of metal and preferably includes a thin-wall 10A (see FIG. 5) in at least the portion which will be inserted into a medullary canal. The tube 10 includes a tube flange 14 and male threads adapted to receive the female threads of the extraction cap 12 (see FIG. 5). The extraction cap 12 includes a groove 16 and retaining flange 18 for cooperation with the slotted retaining sleeve of a tube extractor (to be discussed later in connection with FIGS. 7A and 7B). The extraction cap 12 can be made of any suitable material, such as plastic or metal. The hollow tube 10 and extraction cup 12 may also be made of a disposable material, such as a disposable plastic, so that these instruments can be disposed of after they are used once. If made of a disposable material, the extractor cap 12 can be made integrally with the hollow tube 10. Moreover, the hollow tube 10 can be made to be stored with bone graft in it for a period of time, whether the tube 10 is made of plastic, metal or any other material. In this regard, depending upon the surgical application, it may be desirable to only partially fill the tube for storage or at least not pack it tightly, so that a plunger can be inserted at the time of a surgery. The tube may also be made of a biocompatible material which can stay in the canal without impairing the final implantation. Alternatively, it may thus be a material that is resorbable, such as a resorbable polymer, in the canal after implantation, so as not to interfere with the growth of the bone or stability of the implant. The hollow tube 10 can be of any suitable shape for insertion into the medullary canal of a bone (or any other area of the body) depending upon the application, but is preferably cylindrical in shape. In this regard, as used herein, "tube" shall be construed broadly to encompass structures of any suitable shape for retaining graft material prior to delivery to a medullary canal or any other area of the body. The tube 10 is preferably made in several different diameters, for example 16mm, 18mm, 20mm and 22mm. The selection of the appropriate tube 10 will depend upon preoperative and intraoperative indications. In this regard, the extraction cap 12 is preferably a "universal" extraction cap in the sense that only one extraction cap will be needed for an entire set of differently sized hollow intramedullary tubes. Thus, an instrument kit for a particular joint might include several differently-sized hollow intramedullary tubes to accommodate surgical needs. As will be discussed in more detail below, reamers may be used to clean material (e.g., residual cement from previous implant, marrow, cancellous or cortical bone) out of the medullary canal prior to the insertion of the tube 10. An instrument kit might thus include a set of reamers corresponding in size to the hollow intramedullary tubes in that instrument kit. Once a medullary canal has been prepared with the appropriately sized reamer, the corresponding tube will properly fit in the canal. FIG. 2 shows a plunger of an elongate construction having a centralizing cap or flange 22 at one end (the proximal end) and a centralizing collar 24. The centralizing cap 22 and the centralizing collar 24 are present to position--in this case, center--the plunger 20 within the tube 10. At least the centralizing collar 24 also serves a graft retaining function during the delivery of the bone graft to the medullary canal. This ensures that the bone graft is not withdrawn from the medullary canal as the tube 10 is being withdrawn from the canal. This may occur by maintaining the collar 24 in one position while withdrawing the tube 10, or by pushing it toward the bone graft exit of the tube to push bone graft out of the tube. The centralizing collar 24 may also facilitate the packing of the bone graft within the hollow tube 10 and within the medullary canal. In the tube 10, bone graft can be packed against the centralizing collar 24. In the medullary canal, after the tube 10 is withdrawn, additional bone graft may be placed into the proximal femoral medullary canal by the surgeon's fingers, and the plunger 20 can be used to facilitate the packing of the additional bone graft. By alternately lifting the plunger 20 out of the canal and inserting it back into the canal to impact the bone graft, the collar 24 further packs the additional bone graft in the proximal area. Of course, various structures or devices could be used to center or otherwise position the plunger 20 or to ensure that the bone graft is transferred to the canal upon the withdrawal of the hollow tube 10. See, for example, the plunger shown in FIGS. 6A-6C and 10, which show positioning structures only at the proximal end of the plungers. However, the use of a centralizing cap 22 and a centralizing collar 24, separately situated, may be effective in reducing any toggle of the plunger 20 within the tube 10 and thus to maintain the plunger 20 within the desired position. The centralizing cap 22 and the centralizing collar 24 include grooves 22a and 24a, respectively, for the release of air during the surgical procedure. This will facilitate the use of the plunger 20 while packing the tube/plunger assembly outside of the bone and while impacting the plunger 20 to further pack the bone graft material within the medullary canal. The plunger 20 includes a rod portion 21 below the centralizing collar 24, which is to be inserted into the medullary canal. Rod portion 21 can be of any suitable size (length or thickness) and shape. In the preferred embodiment, the rod portion 21 is cylindrical in shape for more than half of the rod portion 21, the lower approximately one third being slightly tapered, as shown in FIG. 2. In fact, the rod portion 21 of the plunger 20 could emulate at least the distal portion of the implant stem which will finally be implanted in the canal, or it could emulate the entire stem of an implant. The degree of similarity between the rod portion 21 and the implant might depend on the joint being replaced, surgeon preference and other factors. In the preferred embodiment, the centralizing cap 22 and collar 24 "bear" against the interior surface of the hollow tube in that these structures were undersized with regard to the interior diameter of the hollow tube 10. Any tolerance between the outer diameter of a positioning device and the inner diameter of the hollow tube 10 that facilitates the desired positioning function (and graft retaining function, if desirable) is acceptable. However, free sliding movement of such a positioning or graft retaining device within the hollow tube is preferable. Of course, the above relates to the preferred embodiment of the present invention in which the positioning and/or graft retaining device is inside the hollow tube 10. Also, since the centralizing cap 22 and collar 24 in the preferred embodiment are sized to fit within the hollow tube 10, an instrument kit which includes several differently sized tubes 10 must also include a number of plungers 20 which correspond in size to the tubes 10. FIG. 3 illustrates a modular plunger, generally designated as 120 and having a rod portion 121, which is separate from an upper portion 121a. (Alternatively, the rod portion 121 can be integral with the upper portion 121a to form yet a different modular plunger.) The rod portion 121 and upper portion 121a can be of different sizes, and an instrument kit may include several different sizes (widths and lengths) and shapes so that the rod portion 121 and upper portion 121a can be matched preoperatively or intraoperatively. The plunger 120 is adapted to receive, via a threaded connection or otherwise, any one of a plurality of centralizing caps 122 and centralizing collars 124. The centralizing caps 122 and centralizing collars 124 would be of different sizes to accommodate the differently sized tubes 10 within an instrument kit. Thus, one modular plunger 120 and several caps 122 and collars 124 would be required within a set of instruments. The appropriately sized centralizing caps 122 and centralizing collars 124 would be selected based on the selection of the tube 10. Of course, this type of modularity is not limited to centralizing caps and collars, but positioning devices of any type which might be used in connection with a plunger. FIG. 4 shows a hollow bone graft packer 26 which is adapted to be telescopically inserted into the hollow intramedullary tube 10 while the plunger 20 is in place within the hollow intramedullary tube 10. The bone graft packer 26 also includes grooves 26a for permitting air to escape during use, and further includes a knurled handle 26b at one end. As shown in FIG. 5, the bone graft packer 26 facilitates the packing of bone graft within the tube/plunger assembly. The bone graft packer 26 may also include a device (not shown) arranged at the packing end to enlarge the end of the packer 26 and thus facilitate packing. Such a device might be removably attached to the end of the packer 26, perhaps by threads. The device would provide a greater packing area to pack the bone graft in the donut-shaped area around the plunger 20 and within the tube 10. As shown in FIG. 5, the bone graft material, generally designated as 50, is packed within the tube 10 by the bone graft packer 26 such that the bone graft material 50 surrounds the rod portion 21 of plunger 20. Here, the bone graft material 50 is preferably packed as tightly as possible within the tube 10. The initial packing step may include inverting the tube/plunger assembly and pushing it into a container of bone graft to begin filling the tube with bone graft. While FIG. 5 illustrates the packing of the bone graft within the tube 10 while the plunger 20 is within the tube 10, the tube 10 could be partially or fully packed prior to insertion of the plunger 20. Once the plunger 20 is inserted into the tube 10, further compaction of the bone graft material 50 could be accomplished through the use of the bone graft packer 26. FIGS. 6A-6F illustrate the delivery of the bone graft material 50 to the femoral medullary canal. However, prior to the steps shown in FIG. 6A, the tube/plunger assembly must be prepared (e.g., as described above with respect to FIG. 5), and the medullary canal of the distal femur must be prepared. A particular advantage of the preferred embodiment of the present invention resides in the fact that the tube/plunger assembly can be packed and prepared for use prior to even exposing the patient's bone. The preparation of the distal femoral medullary canal may include the revision or removal of a previously implanted hip implant, distal plug (if any) and any associated cements or other materials. An appropriately sized reamer, selected preoperatively and/or intraoperatively, may be used (if necessary) to clean the medullary canal to a size corresponding to the selected hollow intramedullary tube 10. The material cleaned out may include cement, marrow and/or bone, depending upon surgeon preference, the application, etc. A distal plug 40 may then be inserted into the medullary canal at a location which is selected preoperatively and/or intraoperatively. The next preferable step in the bone graft delivery technique is to pack an appropriate amount, e.g., 1-2 inches, of bone graft material 50 against the distal plug 40 (which can be of any suitable material or structure). This can be accomplished with any suitable instrument which fits into the medullary canal. The medullary canal is now prepared for receiving the tube/plunger assembly. As shown in FIG. 6A, the tube/plunger assembly is inserted into the prepared femoral medullary canal against the distal plug 40 and/or any bone graft material which was previously packed against the distal plug 40. It is noted that the plunger 20 illustrated in FIG. 6A has a rod portion 21 which is conical in shape as opposed to cylindrical with a distal taper (as in FIGS. 2 & 3). Also, the plunger 20 in FIG. 6A includes a cap or thin flange 22 at its proximal end to facilitate the positioning, in this case centering, of the plunger 20 within the tube 10. FIG. 6B illustrates the delivery of the bone graft material 50 to the medullary canal by reason of the withdrawal of the tube 10 from the medullary canal, simultaneously with the application of pressure, from the proximal towards the distal end, of the plunger 20. The plunger 20 may be held in one place (by such pressure) while the tube 10 is being withdrawn from the medullary canal, or further pressure can be applied to push the plunger 20 into the medullary canal at the same time the tube 10 is being withdrawn. Pressure can be applied against the plunger 20 by the rod 39 of the extractor 36 (shown in FIG. 7B and described below), or with a rod driver (not shown), which may be held against the plunger 20 by the surgeon while withdrawing the tube 10. In some cases, there may be some incidental proximal movement of the plunger, but this is not preferable (even though the application of further pressure to the plunger will move the plunger into the desired position). During withdrawal of the tube 10, the centralizing collar 24 (shown in FIG. 2) prevents at least any appreciable amount of bone graft 50 from moving out of the canal with the tube 10, and forces the bone graft 50 distally so that it is transferred into the canal. As the tube 10 is withdrawn from the medullary canal, the space occupied by its thin walls 10A is filled with the bone graft material 50. Preferably, it is then packed more tightly by the plunger 20. Following the withdrawal of the tube 10, the plunger 20 is preferably forced further into the medullary canal to further compact the bone graft material 50. This can be accomplished in any suitable manner, including the impaction of the top of the plunger 20. FIG. 6C shows the further compaction of the bone graft material. Once the desired degree of bone graft compaction has been attained, the plunger 20 is removed from the medullary canal. The length of the plunger 20 between the centralizing collar 24 and cap 22, and the cap 22 itself, facilitate the removal of the plunger 20. This leaves a plunger cavity 28 within the packed bone graft material, as shown in FIG. 6D. The medullary canal is now prepared for trial packing and reduction. Preferably, the packing is accomplished through the sequential use of a set of trial implants, ranging from small to larger. As is well known in the field, trial implants often have a shape which is the same or similar to the final implant. FIG. 6E shows a trial hip implant 30, which represents any trial of a set of differently sized trial hip implants. While the bone graft 50 has been well compacted through the use of the plunger 20, trial implant 30 and subsequent trial implants are used within the plunger cavity 28 to shape the bone graft 50 and thus form a cavity which matches the final implant, as shown in FIG. 6E. The sequential use of successively larger trial implants facilitates the efficient shaping of the bone graft 50. The last trial implant used may match the size, as well as the shape, of the final implant, or if the final implant is to be cemented, the last trial implant used may be of a size larger than the size of the final implant. This will leave sufficient room for a cement mantle 32 within the cavity formed in the bone graft 50. During the use of the trial implants 30 to shape the plunger cavity 28, it is preferable to finger-pack or otherwise pack bone graft 50 in the proximal area of the femoral medullary canal so that the shape of the proximal portion of the trial implant 30, and thus the final implant 35, is adequately formed in the canal. FIG. 6F shows the implantation of the final implant 35. As is shown in FIG. 6F, a cement mantle space 32 is provided between the bone graft 50 and the implant 35. The present invention relates not only to preparing instruments for delivery of bone graft material to the medullary canal of a bone, but also relates to preparing instruments for delivery of bone graft material to any portion of a bone which requires bone graft material. Thus, for example, the technique contemplates delivery to a window cut in a bone, where access to such window for bone grafting is difficult to obtain because of muscle tissue, etc. In other words, the window in the bone may not be fully exposed, such that the hollow tube may be helpful in selectively and controllably placing bone graft material in or adjacent to such window. FIG. 7A shows a tube extractor 36, which is quite similar to a caulk gun used to dispel adhesive from an adhesive tube. Specifically, for purposes of this invention, modifications were made to a cement injector sold by Stryker Corporation of Kalamazoo, Michigan under catalog #206-600. The modified cement injector or tube extractor 36 can be used to facilitate the withdrawal of the tube 10 during the delivery of the bone graft 50 into the medullary canal. The tube extractor 36 includes a slotted retaining sleeve 38 which has a slot 38A for receiving the retaining flange 18 of the extraction cap 12 (shown in FIG. 7B), thereby connecting the extractor 36 to the extraction cap 12 and thus the tube 10. The slot 38A and the slotted retaining sleeve 38 have been in other instances used to hold the flange of a container of cement or other material. The extractor 36 includes a rod 39 and a rod collar 39a which will bear against the centralizing cap 22 or other structure at the end of the plunger 20. This is shown in the cutaway portion in FIG. 7B. As with many caulk guns, the rod 39 includes ratchet teeth 39b which facilitate the advancement of the rod 39 when the extractor handle 37 is actuated. However, any other suitable means for advancing the rod 39 can be used. FIG. 7B shows the extractor 36 connected to the extraction cap 12 via the slotted retaining sleeve 38 of the extractor 36 and the groove 16 and retaining flange 18 of the extraction cap 12. In FIG. 7B, the extraction cap 12 is connected to the tube 10 against the tube flange 14. The plunger 20 is assembled within the tube 10 and is surrounded by the bone graft 50. The rod collar 39a is shown in the cut-away portion bearing against the centralizing cap 22. In practice, upon the actuation of the extractor handle 37, the rod 39 of extractor 36 will be forced downwardly against the plunger 20. Because the plunger 20 is bearing against either the distal plug 40 or compacted bone graft 50 which is against the distal plug 40, the tube 10 will move distally out of the medullary canal, leaving the plunger 20 in place (or forcing it further downwardly). While the tube 10 can be withdrawn in any suitable manner, the use of the extractor 36 may be quite helpful in controllably removing the tube 10. While centralizing cap 22 and collar 24 serve the purpose, among others, of centralizing the rod portion 21 of plunger 20 during initial assembly of the tube 10 and plunger 20, it is possible that the centralized position might be moved after that initial assembly. This may occur during the insertion and packing of the bone graft material 50 around the rod portion 21 within the tube 10. To ensure that the packing of the bone graft material 50 within the tube/plunger assembly does not shift the rod portion 21 from its centralized position, adjunct centralizing means can be employed. FIG. 8 illustrates the use of two centralizing screws 52a and 52b, which threadedly engage diametrically opposed holes in the tube 10 and engage the rod portion 21. Together these centralizing screws help ensure that the rod portion 21 remains in the centralized position. The structure of these centralizing screws 52a and 52b may be changed to accommodate any position (other than central) of the rod portion 21 within the tube 10. In addition, while the centralizing screws 52a and 52b are disclosed as adjunct positioning means, they can be used (as shown or in additional pairs) as primary positioning means in lieu of cap 22 and collar 24, or just in lieu of collar 24 (so that they would work with cap 22). FIG. 9 illustrates yet another technique for ensuring that the rod portion 21 remain in the centralized position (or any other desirable position). Here, a centralizing washer 54 (or multiple such washers) may be used. This washer 54, preferably made out of a plastic material, is inserted over the rod portion 21, and remains in place by an interference fit. In the preferred embodiment of these washers, radial relief cuts are made from the central hole, so that the washer can be slid over a tapering rod. Thus, the washer 54 can be further forced onto the cylindrical portion of the rod portion 21 during the packing of the tube/plunger assembly. The washer 54 will finally rest against the centralizing collar 24, but in the meantime will have helped ensure that the position of the rod portion 21 remains as it was originally set. The possibility of the washer 54 being left behind after removal of the tube 10 and the plunger 20 has been recognized. Thus, the washer 54 is preferably biocompatible and detectable by X-ray. It might be such that the washer 54 can be left in place with no harm to the subsequent implantation, or the washer 54 can be extracted prior to finally preparing the canal. As with the centralizing screws 52a and 52b, the washer 54 or multiple washers may be useable as the primary positioning means, alone or with one or both of cap 22 or collar 24. FIG. 10 illustrates a particular specialized application using the present invention. In FIG. 10, the distal femoral bone includes a void 42 on the lateral side of the medullary canal. In this particular application, it may be desirable to clean only the area which has been damaged, while maintaining the strong bone stock in other areas of the medullary canal. Thus, the objective is to selectively place bone graft 50 only in void 42. Once the selected area has been cleaned, the selective delivery of bone graft can be accomplished through the use of a tube 10 and a plunger 20, wherein the plunger 20 has a particular shape and/or orientation with regard to the tube 10 to facilitate selective delivery of the bone graft 50 to the void 42. One way of accomplishing this is shown in FIG. 10. In FIG. 10, the bone graft 50 is only provided on the lateral side of the plunger 20. It is also noted that the plunger 20 includes flattened areas at least at the top of proximal portion to facilitate the positioning of the plunger 20 within the tube 10. Upon withdrawal of the tube 10, and the further compaction of the bone graft 50, the void 42 is filled or at least partially filled with the bone graft 50. A further procedure, such as implantation of a prosthetic device, can now be undertaken. While the foregoing description of figures illustrate the preferred embodiments of the bone graft delivery technique and associated instruments in accordance with the present invention, it should be appreciated that certain modifications can be made and are encouraged to be made without departing from the scope of the present invention which is defined by the claims set forth immediately below.

Claims: A method of preparing instruments for delivering bone graft, characterized by the steps of: a. providing a hollow tube (10) having a first end and a second end; b. placing bone graft (50) into the hollow tube (10), c. arranging a plunger (20) at least partially in the hollow tube so as to form a cavity in the bone graft and such that when the hollow tube is moved in a direction from the first end to the second end, the bone graft can be delivered with the same cavity formed in the bone graft within the hollow tube. The method in claim 1, wherein the plunger (20) includes a graft retaining structure (22, 24), and the method is further characterized by the step of using the graft retaining structure to substantially block an end of the hollow tube (10) to facilitate the exit of bone graft (50) from the hollow tube (10). The method in claim 2, characterized in that the graft retaining structure (22, 24) is used by maintaining it in one position while moving the tube (10) away from the graft retaining area. The method in claim 1, further characterized by the step of packing the bone graft (50) in the hollow tube (10) about the plunger (20) so as to facilitate the formation of the cavity in the bone graft. The method in claim 4, wherein the plunger (20) is arranged at least partially in the hollow tube (10) prior to placement of any bone graft (50) into the hollow tube (10). The method of claim 1, for insertion into a medullary canal of a bone, the hollow tube (10) being adapted for insertion into a medullary canal and for being used to deliver the bone graft to the medullary canal. The method in claim 6, wherein the plunger has an elongate rod portion (21) and whereby the movement of the hollow tube in the direction from the first end to the second end together with the application of pressure to the plunger in the direction from the second end to the first end of the hollow tube facilitates the exit of the bone graft from the hollow tube. The method in claim 7, characterized in that the plunger (20) includes a graft retaining portion (22, 24) so that when the plunger (20) is arranged in the hollow tube (10), the graft retaining portion (22, 24) of the plunger (20) will substantially block the second end of the hollow tube (10), thereby facilitating the exit of the bone graft from the first end of the hollow (10) tube into the medullary canal during withdrawal of the hollow tube (10). The method in claim 8, characterized in that the graft retaining portion (22, 24) is a flange which is larger in cross-section than the elongate rod portion (21). The method in claim 8, characterized in that the graft retaining portion (22, 24) is a flange which bears against the interior surface of the hollow tube (10). The method in claim 9, characterized in that the flange (22, 24) is so constructed and arranged that the rod portion (21) of the plunger (20) is substantially maintained in a desirable position with respect to the hollow tube (10). The method in claim 11, characterized in that the plunger (20) has first and second ends corresponding to the first and second ends of the hollow tube (10), and characterized in that the flange (22, 24) is a cap (22) on the second end of the plunger (20). The method in claim 8, characterized in that the graft retaining portion (24) is also a positioning device for maintaining the rod portion (21) of the plunger (20) in a desirable position with respect to the hollow tube (10). The method in claim 13, further characterized by a cap (22) on an end of the plunger (20), the cap (122) having an outer surface which bears against the interior surface of the hollow tube (10), the cap (22) together with the positioning device (24) maintains the rod portion (21) in a desirable position with respect to the hollow tube (10). The method in claim 14, characterized in that the graft retaining portion (24) includes a collar (24) positioned medially on the plunger (20) above the elongate rod portion (21), the collar having an outer surface which bears against the interior surface of the hollow tube (10). The method in claim 15, characterized in that the cap (122) and the collar (124) are removable from the plunger (20) and are selectable from a plurality of differently sized caps and collars. The method in claim 16, further characterized by the step of providing an additional positioning device (52, 54) below the collar (24). The method in claim 17, characterized in that the additional positioning device (52, 54) comprises screws (52a, 52b) adapted to be threaded through the hollow tube (10) to engage the rod portion (21). The method in claim 17, characterized in that the additional positioning device (52, 54) is a washer (54) disposed around the rod portion (21) by an interference fit and slideable along the rod portion (21) during the insertion of the bone graft into the tube (10). The method in claim 7, characterized in that the plunger (20) includes a positioning (24, 52, 54) device associated with the hollow tube (10) for maintaining the rod portion of the plunger (20) in a desirable position with respect to the hollow tube (10). The method in claim 7, characterized in that the bone graft is placed into the elongate hollow tube (10) after the plunger (20) is arranged therein. The method in claim 21, further characterized by the step of packing bone graft into the hollow tube (10) around the rod portion (21) of the plunger (20) with an at least partially hollow bone graft packer (26) by arranging the bone graft packer (26) around the plunger (20) and inside of the hollow tube (10) and forcing the bone graft into the hollow tube (10). The method in claim 7, characterized in that the rod portion (21) of plunger (20) is at least partially tapered from large to small from the second end to the first end of the hollow tube (10). The method in claim 7, characterized in that the rod portion (21) of the plunger (20) has a configuration which is similar to at least a portion of the prosthesis configuration. The method in claim 7, characterized by the step of selecting an appropriately sized reamer from a set of differently sized reamers, the selected reamer to correspond in size with the hollow tube (10). The method in claim 7, characterized in that the bone graft is disposed in only a portion of the hollow tube (10) such that upon the withdrawal of the hollow tube (10) from the medullary canal, the bone graft can be delivered to a selected area of the medullary canal. Surgical instrument for bone graft (50) delivery, characterized by a hollow tube (10) constructed so that it can receive bone graft (50) and a plunger (20), said hollow tube (10) having a first end and a second end, said plunger (20) being adapted for insertion at least partially within the hollow tube (10), whereby the plunger (20) is constructed and arranged with respect to the hollow tube so as to form a cavity in the bone graft when the bone graft and the plunger are within the hollow tube, and the plunger is further constructed and arranged so that when the hollow tube is moved in a direction from the first end to the second end, the bone graft can be delivered with the same cavity as that formed within the hollow tube. The instrument in claim 27, wherein the plunger (20) has a graft retaining structure (24, 52, 54) which substantially blocks an end of the hollow tube (10) to facilitate the exit of bone graft from the hollow tube (10) during movement of the hollow tube (10) in a direction from the first end to the second end. The instrument in claim 27, characterized in that said hollow tube (10) is adapted to be inserted into a medullary canal, and the plunger (20) has an elongate rod portion (21) adapted to be removably inserted into to said hollow tube (10), at least a portion of said elongate rod portion (21) being spaced from said hollow tube (10) to create a space for bone graft, said hollow tube (10) and plunger (20) being so constructed and arranged as to facilitate the withdrawal of said hollow tube (10) from a medullary canal while leaving in the medullary canal the plunger (20) and bone graft, said plunger (20) being constructed to pack the bone graft within the medullary canal. The instrument in claim 29, wherein the said plunger (20) includes a graft retaining portion (24, 52, 54) which substantially blocks an end of the hollow tube (10) to facilitate the exit of bone graft from the hollow tube (10) into the medullary canal during withdrawal of the hollow tube (10). The instrument in claim 30, characterized in that the graft retaining portion (24) is also a positioning device for maintaining the rod portion (21) of the plunger (20) in a desirable position with respect to the hollow tube (10). The instrument in claim 31, further characterized by a cap (22) on an end of the plunger (20), the cap (22) having an outer surface which bears against the interior surface of the hollow tube (10), the cap (22) together with the graft retaining portion (24) substantially maintain the rod portion in a desirable position with respect to the hollow tube (10). The instrument in claim 31, characterized in that the graft retaining portion (24) includes a collar (24) positioned medially on the plunger (20) above the elongate rod portion (21), the collar (24) having an outer surface which bears against the interior surface of the hollow tube (10). The instrument in claim 33, characterized in that the cap (22) and the collar (24) are removable from the plunger (20) and are selectable from a plurality of differently sized caps and collars. The instrument in claim 29, characterized in that said plunger (20) includes a positioning device (22, 24, 52, 54) associated with said hollow tube (10) for maintaining the rod portion of the plunger in a desirable position with respect to the hollow tube (10). The instrument in claim 35, further characterized by an additional positioning device (52, 54) below the collar (24). The instrument in claim 36, characterized in that the additional positioning device (52, 54) comprises screws (52a, 52b) adapted to be threaded through the hollow tube (10) to engage the rod portion (21). The instrument in claim 36, characterized in that the additional positioning device (52, 54) is a washer (54) disposed around the rod portion (21) by an interference fit and slideable along the rod portion (21) during the insertion of the bone graft into the tube (10). The instrument in claim 35, characterized in that said positioning device (22, 24) is a cap (22) on an end of said plunger and a collar located medially on said plunger. The instrument in claim 35, characterized in that at least a portion of said elongate rod portion (21) of said plunger (20) is tapered. The instrument in claim 29, characterized in that at least a portion of said elongate rod portion (21) of said plunger (20) is tapered. The instrument in claim 41, characterized in that said tapered portion of said elongate rod portion (21) matches at least a portion of a prosthetic device to be implanted in the medullary canal. The instrument in claim 29, characterized in that at least a portion of said elongate rod portion (21) of said plunger (20) is of a shape which is similar to the shape of a prosthetic device to be implanted in the medullary canal. The instrument in claim 27, further characterized by a bone graft packer (26), at least a portion of said bone graft packer (26) being hollow, said bone graft packer (26) being sized to fit telescopically within said hollow tube (10) to pack bone graft into the hollow tube (10). The instrument in claim 29, further characterized by a bone graft packer (26), at least a portion of said bone graft packer (26) being hollow, said bone graft packer (26) being sized to fit telescopically within said hollow tube (10) about said plunger (10) to pack bone graft into the hollow tube (10) prior to the insertion of the hollow tube/plunger assembly into a medullary canal. The instrument in claim 45, further characterized by an extraction cap (12) attached to an end of said hollow tube (10) to facilitate the withdrawal of the hollow tube (10) from the medullary canal. The instrument in claim 46, further characterized by an extractor (36) to facilitate the withdrawal of the hollow tube (10) from a medullary canal, said extractor (36) including a housing, means (38) for connecting said housing to said extraction cap (12), a rod (39) moveable within said housing for applying pressure to said plunger (20) upon actuation of the extractor (36), and actuating means for applying pressure to said plunger (20), said extractor (36) being constructed and arranged so that upon the actuation of said extractor (36), said rod (39) applies pressure against said plunger (20), and said housing, together with said extraction cap (12) and hollow tube (10), move away from said plunger (20) to thereby withdraw the hollow tube (10) from the medullary canal. The instrument in claim 27, characterized in that the hollow tube (10) is made of a disposable material, such that it can be disposed of after a single use. The instrument in claim 27, further characterized by bone graft (50) within the hollow tube (10), the hollow tube (10) and bone graft (50) being capable of being stored for a period of time for use in a surgery. Surgical instrument for use with the instrument of any one of claims 27 to 49, characterized by an extractor (36) to facilitate the controlled movement of a tube (10) which surrounds a rod (20) in an arranged position, while leaving the rod (20) substantially in the arranged position, said extractor (36) including a housing, a connector (38) for connecting the housing to the tube (10), a stem (39) movable within said housing for applying pressure to a rod (20) in its arranged position upon actuation of the extractor (36), and actuating means for applying pressure to such a rod (20), said stem (39) having a rod-engaging portion (39a) sized to engage a rod (20) in a tube (10) and to permit the tube (10) to be withdrawn from around the rod (20) so that the tube (10) is disposed around the stem (39), said extractor (36) being constructed and arranged so that upon actuation of said extractor (36), said stem (39) applies pressure against the rod (20), and said housing, together with a connected tube (10), move the tube (10) away from the arranged position and the rod (20), thereby leaving the rod (20) in the arranged position. The instrument in claim 50, characterized in that said extractor (36) is a modified cement injector gun.

Inventors: CUSICK MICHAEL JOSEPH, SMITH MARGARET ELIZABETH, CUSICK, MICHAEL JOSEPH, SMITH, MARGARET ELIZABETH
Applicants: HOWMEDICA OSTEONICS CORP, HOWMEDICA OSTEONICS CORP.
Application year: 1995
Main classification: A61F2
IPC codes: A61F2, A61M5, A61B17