Abstract:
A reamer for reaming a portion of a long bone cavity for use in implanting a joint prosthesis. The reamer is used in cooperation with a portion of an orthopaedic implant component and includes an expandable body that is adapted to adjust between a plurality of diameters. A plurality of cutting edges are also included and extend outwardly from the body, the edges adapted for cooperation with bone, and the cutting edges expanding as the expandable body expands.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to the field of orthopaedics, and more particularly, to an implant for use in arthroplasty. 
       BACKGROUND OF THE INVENTION 
       [0002]    Patients who suffer from the pain and immobility caused by osteoarthritis and rheumatoid arthritis have an option of joint replacement surgery. Joint replacement surgery is quite common and enables many individuals to function properly when it would not be otherwise possible to do so. Artificial joints are usually comprised of metal, ceramic and/or plastic components that are fixed to existing bone. 
         [0003]    Such joint replacement surgery is otherwise known as joint arthroplasty. Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged joint is replaced with a prosthetic joint. In a typical total joint arthroplasty, the ends or distal portions of the bones adjacent to the joint are resected or a portion of the distal part of the bone is removed and the artificial joint is secured thereto. 
         [0004]    There are known to exist many designs and methods for manufacturing implantable articles, such as bone prostheses. Such bone prostheses include components of artificial joints such as elbows, hips, knees and shoulders. 
         [0005]    Currently in total hip arthroplasty, a major critical concern is the instability of the joint. Instability is associated with dislocation. Dislocation is particularly a problem in total hip arthroplasty. 
         [0006]    Factors related to dislocation include surgical technique, implant design, implant positioning and patient related factors. In total hip arthroplasty, implant systems address this concern by offering a series of products with a range of lateral offsets, neck offsets, head offsets and leg lengths. The combination of these four factors affects the laxity of the soft tissue. By optimizing the biomechanics, the surgeon can provide a patient a stable hip that is more resistant to dislocation. 
         [0007]    In order to accommodate the range of patient arthropathy metrics, a wide range of hip implant geometries are currently manufactured by DePuy Orthopaedics, Inc., the assignee of the current application, and by other companies. In particular, the S-ROM® total hip systems offered by DePuy Orthopaedics, Inc. may include up to six neck offsets per stem diameter, six head lengths and one leg length adjustment. The combination of all these biomechanic options is rather complex. 
         [0008]    Anteversion of a total hip system is closely linked to the stability of the joint. Improper anteversion can lead to dislocation and patient dissatisfaction. Anteversion control is important in all hip stems. However, it is a more challenging issue with the advent of stems with additional modularity. 
         [0009]    The prior art has provided for some addressing of the anteversion problem. For example, the current S-ROM® stems have laser markings on the medial stem and the proximal sleeve. This marking enables the surgeon to measure relative alignment between these components. Since the sleeve has infinite anteversion, it is not necessarily oriented relative to a bony landmark that can be used to define anteversion. In fact, the current sleeves are sometimes oriented with the spout pointing directly laterally into the remaining available bone. 
         [0010]    When a primary or index total joint arthroplasty fails, a revision procedure is performed in which the index devices (some or all) are removed. Quite often the remaining bone is significantly compromised compared to a primary hip procedure. Significant bone loss is observed, often with a lack of bone landmarks typically used for alignment. 
         [0011]    In a common step in the surgical procedure known as total hip arthroplasty, a trial or substitute stem is first implanted into the patient. The trial is utilized to verify the selected size and shape of the implant in situ on the patient and the patient is subjected to what is known as a trial reduction. This trial reduction represents moving the joint, including the trial implant through selected typical motions for that joint. Current hip instruments provide a series of trials of different sizes to help the surgeon assess the fit and position of the implant. Trials, which are also known as provisionals, allow the surgeon to perform a trial reduction to assess the suitability of the implant and the implant&#39;s stability prior to final implant selection. In order to reduce inventory costs and complexity, many trialing systems are modular. For example, in the Excel™ Instrument System, a product of DePuy Orthopaedics, Inc., there is a series of broaches and a series of neck trials that can be mixed and matched to represent the full range of implants. There is a single fixed relationship between a broach and a neck trial, because these trials represent a system of monolithic stem implants. 
         [0012]    Likewise, in the current S-ROM® instrument systems provided by DePuy Orthopaedics, Inc., there are neck trials, proximal body trials, distal stem trials, head trials and sleeve trials. By combining all of these components, the implant is represented. Since the S-ROM® stem is modular and includes a stem and a sleeve, the angular relationship or relative anteversion between the neck and the sleeve is independent and represented by teeth mating between the neck and the proximal body trial. The proximal body trial has fixed transverse bolts that are keyed to the sleeve in the trialing for straight, primary stems. The long stem trials do not have the transverse bolts and are thus not rotationally stable during trial reduction and therefore are not always used by the surgeon. 
         [0013]    With the introduction of additional implant modularity, the need for independent positioning of the distal stem, proximal body and any sleeve that comprise the implants is required. Currently, modular stems for one replacement may come with up to thirty four different sleeve geometries, requiring up to seven different reamer attachments and corresponding pilot shafts to prepare the cone region of the sleeve. 
         [0014]    While the prior art has attempted to reduce the steps in surgical techniques and improve the ability to precisely remove bone to prepare the bone for receiving a proximal component, the need remains for a system and apparatus to reduce the number of components required to perform hip arthoplasty. 
         [0015]    The present invention is directed to alleviate at least some of the problems with the prior art. 
       SUMMARY OF THE INVENTION 
       [0016]    According to one embodiment of the present invention, a reamer for reaming a portion of a long bone cavity for use in implanting a joint prosthesis is provided. The reamer is for cooperation with a portion of an orthopaedic implant component and includes an expandable body that is adapted to adjust between a plurality of diameters. A plurality of cutting edges extending outwardly from the body is also included. The edges are adapted for cooperation with bone, such that the cutting edges expand as the expandable body expands. 
         [0017]    According to another embodiment of the present invention, a method for reaming a portion of a long bone cavity for use in implanting a joint prosthesis is provided. The reamer is used in cooperation with a portion of an orthopaedic implant component. The method includes reaming a distal portion of the long bone using a distal reamer as well as reaming a proximal portion of the long bone using a proximal reamer. At least one of the distal reamer and proximal reamer is an expandable reamer, such that one of the distal reamer and proximal reamer includes an expandable body adapted to adjust between a plurality of diameters. 
         [0018]    According to yet another embodiment of the present invention, a kit for reaming a portion of a long bone cavity for use in implanting a joint prosthesis is provided. The reamers are used in cooperation with portions of an orthopaedic implant component. The kit includes a distal reamer for reaming a distal portion of the long bone, a proximal reamer for reaming a proximal portion of the long bone, and a pilot shaft for insertion into a reamed distal portion and attachment to the proximal reamer during the reaming of the proximal portion. At least one of the distal reamer, proximal reamer, and pilot shaft is expandable, such that one of the distal reamer, proximal reamer, and pilot shaft includes an expandable body adapted to adjust between a plurality of diameters. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in connection with the accompanying drawings, in which: 
           [0020]      FIG. 1  is a plan view of a distal reamer in position in a long bone for preparing a bone canal for receiving a long bone prosthetic stem; 
           [0021]      FIG. 2  is a plan view of an expandable distal reamer according to one embodiment of the present invention; 
           [0022]      FIG. 2   a  is a plan view of the expandable distal reamer of  FIG. 2  in an expanded position, including a view of the internal components of the reamer; 
           [0023]      FIG. 3  is a plan view of a proximal reamer in position in a long bone for preparing a bone canal for receiving a long bone prosthetic stem; 
           [0024]      FIG. 4  is a plan view of an expandable proximal reamer according to one embodiment of the present invention; 
           [0025]      FIG. 4   a  is a plan view of the expandable proximal reamer of  FIG. 4  in an expanded position, including a view of the internal components of the reamer; 
           [0026]      FIG. 5  is a plan view of an expandable pilot shaft according to another embodiment of the present invention. 
           [0027]      FIG. 5   a  is a plan view of the expandable pilot shaft of  FIG. 5 , including a view of the internal components of the shaft. 
           [0028]      FIG. 6  is a plan view of an expandable proximal reamer according to another embodiment of the present invention. 
           [0029]      FIG. 7  is a plan view of an expandable proximal reamer according to yet another embodiment of the present invention. 
           [0030]      FIG. 7   a  is a plan view of the expandable proximal reamer of  FIG. 7  in an expanded state. 
           [0031]      FIG. 8  is a flow chart illustrating a method of using an expandable reamer according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    Embodiments of the present invention and the advantages thereof are best understood by referring to the following descriptions and drawings, wherein like numerals are used for like and corresponding parts of the drawings. 
         [0033]    Referring now to  FIG. 1  a long bone or femur  2  for use with the present invention is shown. The femur  2  includes an intermedullary canal  4  into which the prosthesis of the present invention may be inserted. The femur  2  is resected along resection line  6  by, for example, a power tool, for example, a saw. The resecting of the long bone or femur  2  exposes the intermedullary canal  4  of femur  2 . A distal or cylindrical reamer  8  that may be a standard commercially available reamer is positioned in the intermedullary canal  4  of the long bone  2  to form cavity  10  for receiving an orthopedic joint implant. The distal reamer  8  includes a plurality of longitudinally extending channels, or flutes  12  which are used to remove bone and other biological matter from the intermedullary canal  4  to form the cavity  10 . The distal reamer  8  may be rotated by use of a connector  14  positioned on the distal reamer  8 . The connector  14  may be any standard connector for example a Hudson or an A-O connector. The connector  14  is used to connect to a power tool  15  for rotating the distal reamer  8 . The power tool  15  may be any standard power tool. It should be appreciated that the distal reamer  8  may be rotated through the use of the connector  14  by a hand tool for example a “T” shaped handle. 
         [0034]    The diameter “D” of the distal reamer  8  is determined by the size of the distal stem (not shown) that is to be implanted into the femur  2 . Because of variances in human anatomy, there are numerous sizes of distal stems that can be implanted. Therefore, there are numerous sizes of reamers  8  that can also be used. The large number of reamers  8  can increase production and manufacturing costs, as well as create problems during the surgery should the doctor select the wrong size distal reamer  8  to be used. 
         [0035]    Turning now to  FIG. 2 , an embodiment of an expandable distal reamer  8   a  is shown. Because the distal reamer  8   a  is expandable, the diameter D a  of the distal reamer  8   a  is variable, unlike the fixed diameters of the prior art distal reamers. 
         [0036]    As shown in  FIG. 2 , the expandable distal reamer  8   a  includes a proximal portion  16  and a distal cutting portion  17 . The proximal portion  16  includes at least two gears  18 ,  20  that are in contact with each other such that when the gear  18  is rotated, the gear  20  also rotates. Similar to the distal reamer  8  of  FIG. 1 , the expandable distal reamer  8   a  includes flutes  12   a . The flutes  12   a  expand outwardly from the reamer  8   a  when the gears  18 ,  20  are activated. The reamer  8   a  also includes a plurality of slits, or cuts,  22   a ,  22   b  around its circumference. Such slits  22   a ,  22   b  allow the diameter D a  of the expandable distal reamer  8   a  to enlarge when the gears  18 ,  20  are rotated. 
         [0037]    The gear  18  may be activated by inserting a chuck (not shown) into a hole  24  of the proximal portion  16  and then rotating the chuck. Alternatively, a gauge  25  ( FIG. 2   a ) may be inserted into the hole  24  until it engages the gear  18  and rotated a desired amount. The gauge  25  may include markers  27  ( FIG. 2   a ) to allow the user to know when to stop rotating the gauge. Any other known method for activating a gear may also be utilized. 
         [0038]    Once the gears  18 ,  20  are activated, the gear  20  forces a cone  26  down through the proximal portion  16  into the distal cutting portion  17 . As the cone  26  moves downwardly, the cone&#39;s increasing diameter forces the distal cutting portion  17  to become enlarged. As stated above, the reamer  8   a  includes slits  22   a ,  22   b . These slits  22   a ,  22   b  allow the distal portion  17  to expand as the cone  26  pushes further into the distal portion  17 . Therefore, the diameter D a  of the reamer  8   a  also increases. 
         [0039]    In  FIG. 2   a , the gauge  25  is shown inserted into the top of the expandable distal reamer  8   a  and the distal reamer  8   a  is shown in an expanded position, having a radius D b . When the gauge  25  is inserted, it engages the gear  18 . The gauge  25  may include markings  27  that correlate to the size of the diameter D a  of the expandable distal reamer  8   a . In other words, if the surgeon or other healthcare professional rotates the gauge  25  a particular amount, the marking  27  indicates that the rotation correlates to a particular diameter D a  of the expandable distal reamer  8   a . Furthermore, as the gauge  25  is rotated, the slits  22   a ,  22   b  enlarge as shown in  FIG. 2   a , creating the larger diameter D b . 
         [0040]    As shown in  FIGS. 2 and 2   a , the diameter D a  of the expandable distal reamer  8   a  may be enlarged through mechanical means such as gears  18 ,  20 . However, other devices, such as pneumatic or hydraulic mechanisms could also be used to adjust the diameter D a  of the expandable distal reamer  8   a . In addition, other mechanical devices, such as cross-bars and/or levers could be used to increase the diameter D a  of the expandable distal reamer  8   a.    
         [0041]    After the distal region of the femur  2  is reamed, the proximal portion must then be reamed. As shown in  FIG. 3 , a conical or proximal reamer  30  is used to form cavity  10  for receiving an orthopedic joint implant. The proximal reamer  30  includes a plurality of longitudinally extending channels or flutes  32  which are used to remove bone and other biological matter from the femur  2  to form a cavity  33  having a cone-shape, with a diameter varying between a diameter d 1  to d 2 , which is the same shape and diameter range of the cone-shaped proximal reamer  30 . The proximal reamer  30  may be rotated by use of a connector  34  positioned on the proximal reamer  30 . The connector  34  may be any standard connector for example a Hudson or an A-O connector. The connector  34  is used to connect to a power tool  35  for rotating the proximal reamer  30 . The power tool  35  may be any standard power tool. It should be appreciated that the proximal reamer  30  may be rotated through the use of the connector  34  by a hand tool for example a “T” shaped handle. The proximal reamer  30  is coupled to a pilot shaft  36  that fits into the reamed cavity  10 . The pilot shaft  36  ensures that the proximal reamer  30  goes into the canal and reams straight. 
         [0042]    Turning now to  FIG. 4 , an expandable proximal reamer  30   a  according to one embodiment of the present invention is illustrated. Because the proximal reamer  30   a  is expandable, the diameters d a1 -d a2  of the proximal reamer  30   a  are variable, unlike the fixed diameters of the prior art proximal reamers. 
         [0043]    Similar to the distal reamer  8   a  shown in  FIGS. 2 and 2   a  above, the proximal reamer includes a proximal portion  37  and a distal cutting portion  38 . The proximal portion  37  includes at least two gears  39 ,  40  that are in contact with each other such that when the gear  39  is rotated, the gear  40  also rotates. Similar to the proximal reamer  30  of  FIG. 3 , the expandable proximal reamer  30   a  includes flutes  32   a . The flutes  32   a  expand outwardly from the reamer  30   a  when the gears  39 ,  40  are activated. The reamer  30   a  also includes a plurality of slits, or cuts,  42   a ,  42   b , around its circumference. Such slits  42   a ,  42   b , allow the diameters d a1  and d a2  of the expandable proximal reamer  30   a  to enlarge when the gears  39 ,  40  are rotated. 
         [0044]    The gear  18  may be activated by inserting a chuck (not shown) into a hole  43  of the proximal portion  16  and then rotating the chuck. Alternatively, a gauge  44  ( FIG. 4   a ) may be inserted into the hole  43  until it engages the gear  39  and rotated a desired amount. The gauge  44  may include markers  46  ( FIG. 4   a ) to allow the user to know when to stop rotating the gauge. Any other known method for activating a gear may also be utilized. 
         [0045]    Once the gears  39 ,  40  are activated, the gear  40  forces a cone  48  down through the proximal portion  37  into the distal cutting portion  38 . As the cone  48  moves downwardly, the cone&#39;s increasing diameter forces the distal cutting portion  38  to become enlarged. As stated above, the reamer  30   a  includes slits  42   a ,  42   b . These slits  42   a ,  42   b  allow the distal portion  38  to expand as the cone  48  pushes further into the distal portion  38 . Therefore, the diameters d 1a  and d 1b  of the proximal reamer  30   a  also increase. 
         [0046]    In  FIG. 4   a , the gauge  44  is shown inserted into the top of the expandable proximal reamer  30   a  and the reamer is shown in an expanded position having diameters d b1  and d b2  that are greater than the diameters d a1  and d 3   2 . The gauge  44  may include markings  46  that correlate to the size of the diameters d a1  and d a2  of the expandable proximal reamer  30   a . In other words, if the surgeon or other healthcare professional rotates the gauge  44  a particular amount, the marking  46  indicates that the rotation correlates to particular diameters d a1  and d a2  of the expandable proximal reamer  30   a . Furthermore, as the gauge  44  is rotated, the slits  42   a ,  42   b  enlarge as shown in  FIG. 4   a , creating the larger diameters d b1  and d b2 . In this embodiment, because of the conical shape of the reamer  30   a , as the gears  39 ,  40  are rotated, the diameter d a1  increases more relative to the diameter d a2 . In other words, proximal portion  37  is expanded more relative to the distal portion  38 . 
         [0047]    As shown in  FIGS. 4 and 4   a , the diameters d a1  and d a2  of the expandable proximal reamer  30   a  may be enlarged through mechanical means such as gears  39 ,  40 . However, other devices, such as pneumatic or hydraulic mechanisms could also be used to adjust the diameters d a1  and d a2  of the expandable proximal reamer  30   a . In addition, other mechanical devices, such as cross-bars and/or levers could be used to increase the diameters d a1  and d a2  of the expandable proximal reamer  30   a.    
         [0048]    Turning now to  FIGS. 5 and 5   a , an alternative embodiment of a pilot shaft  50  is shown. As discussed above, a pilot shaft is attached to the proximal reamer to ensure that the reamer properly extends downwardly into the canal. Also as discussed above, because the distal reamer  8  may come in various sizes, the pilot shaft must also come in a variety of sizes. Therefore, to cut-down on manufacturing costs and to reduce the possibility of confusion in the operating, in one embodiment of the present invention, the pilot shaft  50  is also adjustable. As shown in  FIG. 5 , the pilot shaft  50  includes a proximal portion  52 , a distal portion  54  and a central portion  56 . The central portion  56  includes a sleeve  58  that engages two threaded screws  60 ,  62 . As the sleeve  58  is rotated, the threaded screws  60 ,  62  are pushed into openings  64 ,  66  in the proximal and distal portions  52 ,  54 . The proximal and distal portions  52 ,  54  each include slits  68 ,  70  that open as the threaded screws  60 ,  62  are pushed into the openings  64 ,  66  (as shown in  FIG. 5b ). Thus, the operator is able to adjust the diameter of the pilot shaft  50  to match the diameter of the reamed canal  10 . In the embodiments illustrated in  FIGS. 5 and 5   a , the pilot shaft  50  is adjusted from having a diameter of D c  to D d . As shown in  FIGS. 5 and 5   a , the pilot shaft  50  also includes a connectable mechanism such as a threaded portion  72  for attachment to the expandable proximal reamer  30   a . Alternatively, the threaded portion  72  may also attach to a miller shell or a proximal body trial (not shown). 
         [0049]    Turning now to  FIG. 6 , an alternative embodiment of an expandable proximal reamer  80  is illustrated. In this embodiment, the expandable proximal reamer  80  includes an upper conical recess  82 . A threaded expansion rod  84  has a threaded end  86  and is inserted into the upper conical recess  82 . As the threaded expansion rod  84  is advanced through the upper conical recess  82 , the expandable reamer  80  is widened through the use of a slit  88 . The user may thus adjust the diameters of the expandable reamer  80 . 
         [0050]    As shown in  FIG. 6 , the threaded expansion rod  84  may include a gauge  90 , allowing the user to determine the diameter of the reamer  80 . Also, the rod  84  may include upper and lower support rods  92 ,  94  that extend into the reamer  80  to keep the reamer  80  and the rod  84  rigid during use. Either or both of the support rods may also be used in connection with any of the embodiments discussed above. 
         [0051]    In all of the embodiments discussed above, whether for distal reamers, proximal reamers, or pilot shafts, the various gauges and/or markings may also include preset stops that correspond to certain sizes. Such preset stops would make it easier for a user to accurately stop adjusting at the correct diameter. The preset stops may be fashioned out of notches in a thread or any other known mechanism. 
         [0052]    Turning now to  FIG. 7 , another embodiment of an expandable proximal reamer  100  is illustrated. In this embodiment, the proximal reamer  100  includes a screw  102  that extends outwardly from the proximal reamer  100 . The screw  102  has a threaded portion  104   a  that is threadably engaged with threaded portions  104   b ,  104   c  of supports  105 . The supports  105  provide the reamer  100  with support during cutting, enabling the reamer  100  to expand, yet still maintain its strength and rigidity. 
         [0053]    As a user rotates the screw  102 , the threads  104   a  cause the threaded portions  140   b ,  104   c  to also rotate. The threaded portions  104   b ,  104   c  are also threadably engaged with a thread  104   d , such that when the threaded portions  104   b ,  104   c  are rotated, the threaded portion  104   d  also rotates. The threaded portion  104   d  is coupled to a cone  106 , such that as the threaded portion  104   d  rotates, the cone  106  moves in a downward direction  112  ( FIG. 7   a ), causing the proximal reamer  100  to expand outwardly in the direction indicated by arrows  114 . This also causes the supports  105  to move outwardly in directions  110  as shown in  FIG. 7   a.    
         [0054]    As shown in  FIGS. 7 and 7   a , the proximal reamer  100  is coupled to a pilot shaft  108 , such that as the cone  106  moves downwardly, the pilot shaft  108  may also expand in an outward direction as indicated by arrows  114  ( FIG. 7   a ). 
         [0055]    Turning now to  FIG. 8 , a method for utilizing the expandable reamers is shown. At step s 200 , the femur is resected. Next, the user selects the distal reamer to be used at step s 202 . If an expandable distal reamer is to be used, then at step s 202 , the user then adjusts the diameter of the distal reamer as described above. At step s 204 , the distal reamer is inserted and the distal portion of the long bone is reamed (step s 206 ). Next, at step s 208 , the proximal reamer is selected. If the proximal reamer is an adjustable reamer, the user will adjust the proximal reamer to the appropriate diameter. If the proximal reamer is not adjustable, then the user must select a proximal reamer with an appropriate diameter from a set of reamers. Next, at step s 210 , the pilot shaft is selected or adjusted as necessary. At steps  212 , the proximal reamer is attached to a pilot shaft. The proximal reamer and shaft are inserted into the proximal portion of the long bone and the reamed distal portion, respectively at step  214 . The proximal portion is then reamed at step s 216 . The rest of the reaming and implantation process is then completed in any of the ways customary and known in the prior art. It should be noted that although in this example, both the proximal reamer and the distal reamer were expandable, that in some embodiments, only one of the reamers may be expandable. Also, while some embodiments refer to an adjustable pilot shaft, in other embodiments, the pilot shafts of the prior art may be attached to the proximal reamers. 
         [0056]    In some embodiments of the present invention, a kit for reaming the long bone is provided, including distal reamers, proximal reamers, and pilot shafts. The kit includes at least one reamer that is an expandable reamer. In some embodiments, both the distal reamer and the proximal reamers will be expandable. In other embodiments, only one of the types of reamer will be expandable. In some embodiments, the pilot shaft may also be expandable. 
         [0057]    According to some embodiments of the present invention, the expandable reamers may be able to expand to all sizes required for that type of reamer. In other embodiments, the expandable reamers may only expand through a range, and a plurality of reamers may still be required. For example, if the expandable reamer is a proximal reamer, a kit may include three expandable proximal reamers. Each expandable proximal reamer in such a kit has a diameter that is variable within a range. 
         [0058]    Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.