Abstract:
A kit for use in implanting a stem into a long bone. The kit includes a universal handle including a locking mechanism, and a plurality of shafts. Each of the plurality of shafts is adapted to couple with the universal handle such that the locking mechanism of the universal handle locks each of the plurality of shafts to the handle.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to the field of orthopaedics, and more particularly, to an instrument used to insert 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]    Numerous instruments are required in performing a hip arthroplasty. The surgeon must use various reamers and broaches for cutting and shaping the bone. Additionally, when implanting the stem into the long bone, the surgeon must use a stem inserter. 
         [0006]    In hip arthroplasty, there are currently many different approaches, or surgical techniques in implanting the bone prostheses. The posterior approach accesses the joint through the back, gives straightforward access to the acetabulum, provides good visualization of the femoral shaft, and allows the surgeon to preserve the hip abductors. The anterolateral approach exploits the intermuscular plane between the tensor fasciae latae and the gluteus medius, involves partial or complete detachment of the abductor mechanism, and combines good exposure of the acetabulum with safety during preparation of the femoral shaft. The anterior approach utilizes the internervous plane between the sartorius and the tensor fasciae latae, exposes the hip without detachment of muscle from the bone, and takes advantage of the fact that the hip is an anterior joint, closer to the skin anteriorly than posteriorly. 
         [0007]    Because femoral access is different with each of the aforementioned approaches, it is desirable to use different stem inserters for each approach. Depending on how the surgeon approaches the femur, or long bone, an inserter with different angular or curved configurations may be preferred so as to best reach the stem/implant without impinging the bone or surrounding soft tissue. Surgeons may also choose different angled/curved/offset inserters depending on the anatomy of the individual patients and the selected implants. Some surgeons also prefer to use multiple stem inserters at the varying stages of stem insertion during a single surgery. Like other surgical instruments, these stem inserters are housed in instrument cases that must conform to weight and size requirements. Unfortunately, the stem inserters&#39; handles are quite bulky and can greatly reduce the available case weight and free space for other required hip arthroplasty instrumentation. The transportation, set-up, and sterilization of multiple heavy stem inserters can also become a burden to the surgical staff. Therefore, there is a need for a reduction in the size and weight of surgical instruments used in joint replacement surgeries. 
         [0008]    The present invention is directed to alleviate at least some of the problems with the prior art. 
       SUMMARY OF THE INVENTION 
       [0009]    According to one embodiment of the present invention, a kit for use in implanting a stem into a long bone is provided. The kit includes a universal handle including a locking mechanism and a plurality of shafts. Each of the plurality of shafts is adapted to couple with the universal handle such that the locking mechanism of the universal handle locks each of the plurality of shafts to the handle. 
         [0010]    According to another embodiment of the present invention, a kit for use in implanting a stem in a long bone is provided. The kit includes a handle and a removable shaft. The removable shaft includes an end portion for extending into the aperture to lock the removable shaft to the handle. 
         [0011]    According to yet another embodiment of the present invention, a method for inserting a stem into a long bone is provided. The method includes providing a handle and a plurality of shafts. Each of the plurality of shafts including a handle-attachment end and a stem-attachment end. One of the plurality of shafts is selected and the handle-attachment end of the selected shaft is inserted into the handle. The stem-attachment end of the shaft is inserted into the stem and the stem is seated into the long bone. 
         [0012]    Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    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: 
           [0014]      FIG. 1  is a plan view of a modular stem inserter according to one embodiment of the present invention; 
           [0015]      FIG. 2  is a top view of the modular stem inserter of  FIG. 1 ; 
           [0016]      FIG. 3  is a side view of the modular stem inserter of  FIG. 1 ; 
           [0017]      FIG. 4  is an internal, assembled view of a locking mechanism of the handle of the stem inserter according to one embodiment of the present invention; 
           [0018]      FIG. 5  is an exploded view of the locking mechanism of the stem inserter handle of  FIG. 4  and the stem inserter shaft of  FIG. 1 . 
           [0019]      FIG. 6  is an internal, assembled view of the stem inserter handle of  FIG. 4  and stem inserter shaft of  FIG. 1   
           [0020]      FIG. 7  is a plan view of a modular stem inserter kit according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    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. 
         [0022]    Referring now to  FIGS. 1-3 , a stem inserter  10  according to one embodiment of the present invention is shown. The stem inserter  10  includes a handle  12  and a shaft  14 . In the embodiment illustrated in  FIG. 1 , the shaft  14  is a curved anterior shaft used during the anterior approach. However, it should be understood that any type of shaft may be used, and the curved anterior shaft is for illustrative purposes only. 
         [0023]    As shown in  FIG. 1 , the handle  12  is separable from the shaft  14 . The handle  12  includes a shaft-attachment end  16  and an opposing end  18 . The shaft  14  includes a handle-attachment end  20  and a stem attachment end  22 . The stem attachment end  22  is designed to fit on to the end of a stem (not shown) for insertion into the long bone. The stem attachment end  22  of the shaft  14  may vary depending on the stem&#39;s insertion feature. The shaft-attachment end  16  of the handle  12  includes an aperture  24  designed to receive the handle-attachment end  20  of the shaft  14 . In the illustrated embodiment, the aperture  24  includes a flat end  26  that corresponds to a flat end  28  on the handle-attachment end  20 . The flat ends  26 ,  28  ensure proper alignment of the shaft  14  and the handle  12  while also minimizing rotational toggle. The opposing end  18  of the handle  12  serves as an impaction surface for the surgeon during stem insertion. 
         [0024]    Turning now to  FIG. 4 , an internal, assembled view of the shaft-attachment end  16  of the handle  12  is illustrated. The shaft-attachment end  16  of the handle  12  includes a locking mechanism for securing the handle  12  to the shaft  14 . As shown in  FIG. 4 , the locking mechanism includes a spring-loaded button  30 . The spring-loaded button  30  includes a spring  32  to lock the shaft  14  to the handle  12 . 
         [0025]      FIG. 5  illustrates an exploded view of the handle  12  and the shaft  14 . As illustrated, the handle-attachment end  20  of the shaft  14  includes a shaft tip chamfer  34 . The angle on the chamfer  34  allows the shaft  14  to be inserted into the aperture  24  of the handle  12  without depressing the button  30 . The chamfer  34  presses against a corresponding edge  36  of the button  30 , which causes the button  30  to compress the spring  32 , thus allowing the shaft  14  to be inserted. 
         [0026]    The shaft  14  also includes a shaft-locking slot  38  and a shaft-locking ramp  40 . When the shaft  14  is inserted into the handle  12 , the shaft-locking slot  38  and the shaft-locking ramp  40  engage with the internal button base  42  of the button  30  in order to lock the shaft  14  into the handle  12 . Specifically, once the shaft  14  is inserted into the handle  12 , the spring  32  decompresses causing the button  30  to apply force to the shaft-locking ramp  40 . This motion forces the shaft  14  up and into the handle  12  to minimize toggle and ensure a secure lock. Once the shaft  14  is inserted into the handle  12 , the shaft-locking slot  38  receives pressure from the button  30  to lock the shaft  14  to the handle  12 . The shaft-locking slot  38  also prevents the shaft  14  from being pulled out of the handle  12  without first depressing the button  30 . 
         [0027]    A stop pin  44  is included on the handle  12  and engages a slot  46  on the button  30 . The stop pin  44  prevents the button  30  from falling out of the handle  12 . Also, the slot  46 , along with the stop pin  44 , limits the travel of the button  30  in order to ensure that the locking mechanism of the handle  12  always functions properly. 
         [0028]    Also as shown in  FIG. 5 , the shaft  14  includes a flat impaction surface  48 . The flat impaction surface  48  allows the surgeon&#39;s impaction force to transfer from the handle  12  to the shaft  14 . The flat-impaction surface  48  ensures that excessive load is not applied to the various features of the locking mechanism (e.g., the spring-loaded button  30 , the shaft-locking slot  38 , etc . . . ). 
         [0029]    Turning now to  FIG. 6 , the modular stem inserter  10  is shown with the handle  12  and the shaft  14  in an engaged position. As shown, the spring-loaded button  30  has engaged the shaft-locking slot  38  ( FIG. 5 ) of the shaft  14 . The spring  32  ( FIG. 5 ) is in a compressed position pushing the button  30  out, causing the internal button base  42  ( FIG. 5 ) of the button  30  to contact shaft-locking ramp  40  ( FIG. 5 ), locking the shaft  14  to the handle  12 . As identified in  FIG. 6 , the handle  12  and the shaft  14  have each been etched with an alignment triangle  49 . The alignment triangles  49  indicate alignment of the flat end  26  ( FIG. 1 ) of the handle  12  and the flat end  28  ( FIG. 1 ) of the shaft  14 , thus acting as a visual for easy insertion. This feature allows the user to insert the handle-attachment end  20  of the shaft  14  into the aperture  24  of the handle  12  in any rotational orientation and then simply rotate the shaft  14  until the two alignment triangles  49  are aligned. The shaft  14  then snaps into the handle  12 . 
         [0030]    Although in the illustrated embodiment the alignment triangles  49  are triangular, it should be understood that other shapes or indicators could be used. Also, other known marking methods instead of etching may also be used to create these features. In some embodiments, the etchings  49  may not be included and instead, the user may assemble the handle  12  and the shaft  14  by feel. 
         [0031]    Turning now to  FIG. 7 , a kit  50  according to one embodiment of the present invention is shown. In this embodiment, the kit  50  includes a handle  52  and four shafts  54   a ,  54   b ,  54   c ,  54   d . Each of the shafts  54   a ,  54   b ,  54   c ,  54   d  includes a handle-attachment end  56   a ,  56   b ,  56   c ,  56   d  that is configured the same as the handle-attachment end  20  illustrated in  FIGS. 1-6  above. In these embodiments, because each of the handle-attachment ends  56   a ,  56   b ,  56   c ,  56   d  is of the same design, each shaft can be locked into the handle depending on the type of surgery or the surgeon preference. The illustrated kit includes the standard straight shaft  54   a , the curved anterior shaft  54   b , the posterior shaft  54   c , and the bullet tip shaft  54   d.    
         [0032]    During surgery, the surgeon will select the appropriate shaft based upon the surgical approach, the surgeon&#39;s personal preference, and patient anatomy, as well as the type of stem being implanted. The surgeon will attach the selected shaft  54  to the handle  52  by pushing the two together, making sure the two alignment arrows  49  ( FIG. 6 ) of the handle  12  and the shaft  14  are aligned. After introducing the stem by hand into the femoral canal, the surgeon then aligns the stem attachment end  22  ( FIGS. 1-6 ) of shaft  14  with the stem&#39;s driver platform and continues the insertion process until the stem is properly seated. In some embodiments, the stem-attachment end  22  of the shaft  14  may be threaded to correspond to threads in the stem. In such a case, the surgeon could then thread the stem-attachment end  22  of the shaft  14  onto the stem and use the stem inserter  10  to introduce the stem into the femoral canal. 
         [0033]    In one embodiment, the handle  12  and the shaft  14  will be manufactured of a metal material. This metal could be a stainless steel including, but not limited to, precipitation hardening stainless steels such as 17-4, 13-8Mo, XM-13, 455, XM-25, and 465 or martensitic stainless steels such as 410, 416, 420, 431, 440A, 440B, and 440C. The instruments could also be manufactured out of a cobalt-based alloy such as wrought CoCrMo (F1537), a hardened condition of Co—Cr—W—Ni (F90), cold worked MP35N (ASTM F562), or another metal material suitable for a medical application. In other embodiments, the handle  12  may be made of re-usable stainless steel while the shaft  14  is a disposable device made of a plastic material. This plastic may or may not contain reinforcement and could be ABS, polypropylene, polyurethane, polyesters, Acetals, or Polyimide. This is a representative list and does not exclude other plastics or polymer systems that are used for medical applications. 
         [0034]    Although the above-shown embodiments depict four different types of shafts, any number of shafts may be included. The shafts may be shaped to relate to a particular surgical technique, a different type of stem, a surgeon&#39;s preference, or even a particular stage of the impaction process. The shafts may also have a threaded stem attachment end  22  in order to provide the surgeon greater version and insertion control. 
         [0035]    Also, although the locking mechanism has been described as a spring-loaded button cooperating with a shaft-locking slot, it should be understood that other types of known locking mechanisms may be utilized such as a ball plunger, interlocking teeth, Hudson end, prongs and/or circular springs. 
         [0036]    In other embodiments, the shaft-tip chamfer may not be utilized, and the user may have to activate the locking mechanism by depressing the button  30  in order to insert the shaft into the handle. 
         [0037]    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.