Abstract:
Disclosed herein are orthopedic trialing systems including a stem, an adaptor and a trial member. The stem may be a trial or implant stem. The trial member may be a cup or head. The adaptor is used to account for the difference in the coupling of the trial member and stem and an implant member and stem. The stem has a first coupling feature and a shaft portion adapted to be received in a canal of a bone of a patient. The adaptor has planar top and bottom surfaces and at least one aperture therethrough. The trial member has a second coupling feature, wherein one of the first and second coupling features of either the trial member or stem extends through the aperture of the adaptor and at least partially into the other of the first and second coupling features for coupling together the trial member, the adaptor and the stem.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an orthopedic trial adaptor for use with both standard and reverse shoulder arthroplasty systems in a cemented, fracture or any similar setting where the final seating height of the head or cup implant is not readily available. The thickness of the orthopedic trial adaptor takes into account the difference in coupling between a trial which sits flush on a humeral stem and an implant which sits proudly on the humeral stem. 
       BACKGROUND OF THE INVENTION 
       [0002]    Over time and through repeated use, bones and joints can become damaged or worn. For example, repetitive strain on bones and joints (e.g., through athletic activity), traumatic events, and certain diseases (e.g., arthritis) can cause cartilage in joint areas, for example, which normally provides a cushioning effect, to wear down. When the cartilage wears down, fluid can accumulate in the joint areas, resulting in pain, stiffness, and decreased mobility. The same can happen in the case where tendons in a joint become lax or soft tissues in or adjacent the joint tear becomes damaged or worn. 
         [0003]    Arthroplasty procedures can be used to repair damaged joints. During a typical arthroplasty procedure, an arthritic or otherwise dysfunctional joint can be remodeled or realigned, or an implant or implants can be implanted into the damaged region. Arthroplasty procedures may take place in any of a number of different regions of the body, such as a knee, a hip, a shoulder, or an elbow. 
         [0004]    One type of arthroplasty procedure is a shoulder arthroplasty, in which a damaged shoulder joint is replaced with prosthetic implants. The shoulder joint may have been damaged by, for example, arthritis (e.g., severe osteoarthritis or degenerative arthritis), trauma, or a rare destructive joint disease. 
         [0005]    Implants that are implanted into a damaged region may provide support and structure to the damaged region, and may help to restore the damaged region, thereby enhancing its functionality. Prior to implantation of an implant in a damaged region, the damaged region may be prepared to receive the implant. In the case of a shoulder arthroplasty procedure, one or more of the bones in the shoulder area, such as the humerus and/or glenoid, may be treated (e.g., cut, drilled, reamed, and/or resurfaced) to provide one or more surfaces that can align with the implant and thereby accommodate the implant. Standard alignment instrumentation may be used for locating a position and orientation to resect the humeral head for proper humeral stem placement in the humerus. 
         [0006]    Accuracy in implant alignment is an important factor to the success of the procedure. A one to two millimeter translational misalignment, or a few degrees of rotational misalignment, may result in imbalanced ligaments, and may thereby significantly affect the outcome of the procedure. For example, implant misalignment may result in intolerable post-surgery pain, and also may prevent the patient from having proper deltoid tension or range of motion. 
         [0007]    To achieve accurate implant alignment, prior to treating (e.g., cutting, drilling, reaming, and/or resurfacing) any regions of a bone, it is important to correctly determine the location at which the treatment will take place and how the treatment will be oriented. Accordingly, instruments such as trials have been developed to be used in this part of the procedure. Generally, trials are affixed to the bone during joint kinematic evaluation and removed therefrom after a proper position and orientation for the implant has been determined. 
         [0008]    Typically, trials are designed to correspond to an implant in size and shape. In a shoulder arthroplasty procedure, for example, a trial stem may be designed to be temporarily inserted into a prepared medullary canal of the humerus in a manner similar to that of an implant. Known trials may take many forms. For example, an expanding trial stem, such as that described in U.S. Pat. No. 8,216,320, the entire contents of which are hereby incorporated by reference herein, includes a trial stem that may be expanded after insertion into the medullary canal. When using such trial stems, particularly in shoulder replacements, it may be difficult to establish the proper position and orientation for the implant in the humerus. Further, trial cups and heads may be coupled to the trial stem during the trialing procedure. In order to achieve proper deltoid tension in a shoulder arthroplasty procedure, any differences in positioning between the trials and the corresponding implants should be taken into account. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    Humeral trial cups and heads of the present invention have connector or shaft portions for coupling the trial cups and heads to a corresponding humeral stem. While the trials are configured to sit flush with the stem, the implant head or cup sits proudly on the stem to ensure their tapered connection features are always properly engaged. A trial adaptor of the present invention is used to take into account the planar distance by which the implant head or cup sits proudly on the stem. The planar distance is defined by the distance between a base surface of the implant head or cup and a neck or contact surface of the stem. 
         [0010]    A first aspect of the present invention is an orthopedic trialing system comprising a stem, an adaptor and a cup. The stem has a first coupling feature and a shaft portion adapted to be received in a canal of a bone of a patient. The adaptor has top and bottom surfaces and an aperture through the top and bottom surfaces. The cup has a second coupling feature, wherein one of the first and second coupling features extends through the aperture of the adaptor and at least partially into the other of the first and second coupling features for coupling together the cup, the adaptor and the stem. 
         [0011]    In one embodiment of the first aspect, the bottom surface of the adaptor contacts and lies adjacent to a contact surface of the stem when the cup, the adaptor and the stem are coupled together. In another embodiment, when the top surface of the adaptor contacts and lies adjacent to a contact surface of the cup, the adaptor and the stem are coupled together. 
         [0012]    According to the first aspect of the present invention, each of the top and bottom surfaces of the adaptor and the contact surfaces of the cup and stem are planar. In one embodiment, the first coupling feature of the stem is a recess, the stem having a contact surface with the recess therein. The second coupling feature of the cup is a protrusion that extends through the aperture of the adaptor and at least partially into the recess of the stem when the cup, the adaptor and the stem are coupled together. 
         [0013]    In another embodiment, the first coupling feature is a protrusion, the stem having a contact surface with the protrusion extending outwardly therefrom. The second coupling feature of the cup is a recess and the protrusion of the stem extends through the aperture of the adaptor and at least partially into the recess of the cup when the cup, the adaptor and the stem are coupled together. 
         [0014]    In yet another embodiment, the adaptor includes an engagement feature adapted to couple the adaptor to the stem. 
         [0015]    In still yet another embodiment, the stem is selected from the group consisting of a broach, a trial stem or a prosthesis stem. 
         [0016]    A second aspect of the present invention is an orthopedic trialing system comprising a stem, an adaptor and a cup. The stem has a planar surface and a shaft portion adapted to be received in a canal of a bone of a patient. The adaptor has a thickness defined by a linear distance between top and bottom surfaces thereof. The cup has a planar surface, wherein the planar surface of the stem and the planar surface of the cup are separated by the thickness of the adaptor when the cup, the adaptor and the stem are coupled together. 
         [0017]    A third aspect of the present invention is an orthopedic trialing system comprising a stem, an adaptor and a cup. The stem having a shaft portion adapted to be received in a canal of a bone of a patient. The adaptor having top and bottom surfaces and an aperture through the top and bottom surfaces. The cup having a coupling feature for coupling together the cup, the adaptor and the stem. 
         [0018]    In each of the above described aspects of the invention, the orthopedic trial system comprises a stem, an adaptor and a cup. However, in other aspects of the present invention, the cup that is used in reverse shoulder cases can be replaced with a head that is used in a total arthroplasty procedure. In other words, the orthopedic trial system in total arthroplasty cases includes a stem, an adaptor and a head. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1A  shows the general shoulder joint anatomy of a patient. 
           [0020]      FIG. 1B  is a view of a glenoid cavity of the shoulder joint. 
           [0021]      FIG. 2  is a posterior view of a proximal portion of a humerus of the shoulder joint showing a resection line adjacent the anatomical neck of a humerus. 
           [0022]      FIG. 3  is a schematic view of an exemplary proximal humerus broken into a plurality of bone fragments. 
           [0023]      FIG. 4  is a cross-sectional view of one embodiment of a trial stem for use during a shoulder replacement procedure. 
           [0024]      FIG. 5A  is a perspective view of one embodiment of a stem implant according to aspects of the disclosure. 
           [0025]      FIG. 5B  is a perspective view of a proximal portion of the stem implant of  FIG. 5A . 
           [0026]      FIG. 5C  is a top view of the stem implant of  FIG. 5A . 
           [0027]      FIG. 5D  is a side view of a proximal portion of the stem implant of  FIG. 5A . 
           [0028]      FIG. 6A  is a front view of one embodiment of a humeral head trial coupled to a stem implant of  FIG. 5A  inserted into a resected humeral bone. 
           [0029]      FIG. 6B  is a front view of one embodiment of a humeral head implant coupled to a stem implant of  FIG. 5A  inserted into a resected humeral bone. 
           [0030]      FIG. 7A  is a front view of one embodiment of a humeral cup trial coupled to a stem implant of  FIG. 5A  inserted into a resected humeral bone. 
           [0031]      FIG. 7B  is a front view of one embodiment of a humeral cup implant coupled to a stem implant of  FIG. 5A  inserted into a resected humeral bone. 
           [0032]      FIG. 8A  is a front view of one embodiment of a humeral head trial coupled to a stem implant of  FIG. 5A  inserted into a fractured humeral bone. 
           [0033]      FIG. 8B  is a front view of one embodiment of a humeral head implant coupled to a stem implant of  FIG. 5A  inserted into a fractured humeral bone. 
           [0034]      FIG. 9A  is a perspective view of one embodiment of a humeral trial adaptor of the present invention. 
           [0035]      FIG. 9B  is another perspective view of the humeral trial adaptor of  FIG. 9A . 
           [0036]      FIG. 10A  is a perspective view of a trial assembly including the humeral trial adaptor of  FIG. 9A  coupled to one embodiment of a humeral trial cup coupled to a humeral trial insert. 
           [0037]      FIG. 10B  is a front view of the trial assembly of  FIG. 10A  coupled to an exemplary trial or implant stem. 
           [0038]      FIG. 11A  is a front cross-sectional view of one embodiment of a humeral cup trial, humeral trial adaptor and stem implant coupled to one another. 
           [0039]      FIG. 11B  is a front cross-sectional view of one embodiment of a humeral head trial, humeral trial adaptor and stem implant coupled to one another. 
           [0040]      FIG. 12A  is a perspective view of another embodiment of a humeral trial adaptor of the present invention. 
           [0041]      FIG. 12B  is a perspective view of the humeral trial adaptor of  FIG. 12A  coupled to one embodiment of a humeral trial cup. 
           [0042]      FIG. 13A  is a perspective view of another embodiment of a humeral trial adaptor of the present invention. 
           [0043]      FIG. 13B  is a perspective view of the humeral trial adaptor of  FIG. 13A  coupled to one embodiment of a humeral head trial. 
       
    
    
     DETAILED DESCRIPTION 
       [0044]    In describing preferred embodiments of the disclosure, reference will be made to the directional nomenclature used in describing the human body. It is noted that this nomenclature is used only for convenience and that it is not intended to be limiting with respect to the scope of the invention. When referring to specific directions in relation to a device, the device is understood to be described only with respect to its orientation and position during an exemplary application to the human body. As used herein when referring to bones or other parts of the body, the term “proximal” means closer to the heart and the term “distal” means more distant from the heart. The term “inferior” means toward the feet and the term “superior” means toward the head. The term “anterior” means toward the front part or the face and the term “posterior” means toward the back of the body. The term “medial” means toward the midline of the body and the term “lateral” means away from the midline of the body. Further, although the devices and methods described herein are generally described in relation to human shoulder replacements, it should be understood that the devices and methods are not intended to be so limited and could be used with other joints, such as other ball and socket joints, including the hip, for example. 
         [0045]      FIGS. 1A-B  show the general anatomy of shoulder joint  10  of a patient. As shown in  FIG. 1A , humerus  12  of joint  10  includes a neck portion  13 , a head portion  14  and a shaft portion  17  having a greater tuberosity  16  and a lesser tuberosity  18 . Between greater and lesser tuberosities  16 ,  18  is bicipital groove  15 . As shown in  FIG. 1B , scapula  22  terminates at glenoid  20  having a cavity  21  in which an outer surface  11  of head portion  14  rotates within. Along with humerus  12  and scapula  22 , the acromion  24 , rotator cuff  26  and clavicle  28  all provide support to the range of motion of the shoulder joint  10  of the patient. 
         [0046]      FIG. 2  is a posterior view of a proximal portion of humerus  12  of shoulder joint  10 . Head portion  14  includes outer surface  11 . Also shown is bicipital groove  15 , a substantially straight surgical neck line  25  and a curvy anatomical neck line  27 . Outer surface  11 , biciptal groove  15 , substantially straight surgical neck line  25  and curvy anatomical neck line  27  are all anatomical features of humerus  12  that can be used to aid in determining the proper neck resection line. 
         [0047]    Prior to a total shoulder arthroplasty procedure being conducted, shoulder joint  10  is generally compromised through injury or general wear and tear. A compromised joint generally leads to range of motion difficulty and pain for the patient. In a joint  10  that is compromised, head portion  14  and/or glenoid cavity  21  may be degenerated such that the axis of rotation of the shoulder joint is not in the same location as it was prior to joint  10  being compromised. 
         [0048]    The axis of rotation of the shoulder joint varies based upon the type of motion. For flexion and extension, the axis of rotation is a transverse axis though the center of the humeral head. For abduction and adduction, the axis of rotation is a sagittal axis thought the center of the humeral head. For internal and external rotation, the axis of rotation is a vertical axis though the center of the humeral head. 
         [0049]    During a total shoulder arthroplasty procedure, the humerus is resected in order to receive a humeral stem component. In such a procedure, the humeral head is generally resected and the shaft of the humerus is reamed to receive the humeral stem component prosthesis. It is important that the humeral stem component be positioned in the correct location and orientation in order to restore the axis of rotation of joint  10 . Some humeral stem components may include a flange that is adapted to contact a flat portion of resected bone of the humerus in order to correctly position and stabilize the humeral stem component within shaft  17  of humerus  12  such that the axis of rotation of joint  10  may be restored. 
         [0050]    Also during a total shoulder arthroplasty procedure, the glenoid is resected in order to receive a glenoid component. In a shoulder arthroplasty procedure for implanting a reverse shoulder prosthesis, a cavity of the glenoid may be reamed and a guide hole may be drilled in order to receive a central screw extending outwardly from an outer contact surface of the glenoid component. The location and orientation of the guide hole may be based on the shape of the glenoid component, for example, such that the glenoid component can be implanted in the resected glenoid cavity and the axis of rotation of the joint may be restored. It is important that the glenoid component be positioned in the correct location and orientation in order to restore the axis of rotation of joint  10 . The glenoid component preferably has an articular surface corresponding to an outer surface of a humeral head component which is engaged to the humeral stem component implanted at least partially within the shaft of the humerus. Generally, the glenoid component has a diameter that is approximately 6 mm in diameter larger than the humeral head component. 
         [0051]    As discussed above, humerus  12  must be resected at the correct location and orientation in order for a corresponding humeral stem prosthesis to be accurately implanted in shaft  17  of humerus  12  such that the axis of rotation of the shoulder joint may be restored. Thus, the location and orientation of resection line  30 , as shown in  FIG. 2 , is either preoperatively or intraoperatively planned according to a desired result of the arthroplasty procedure. 
         [0052]    Generally, the replacement of a humeral head with a prosthetic implant during shoulder arthroplasty involves gaining access to the shoulder joint through a retracted incision and removing the damaged humeral head. An exemplary damaged proximal humerus  10 ′ is illustrated in  FIG. 3 . Although such breaks giving rise to a plurality of bone fragments may occur in any number of ways, this particular humerus  10 ′ is broken such that a first segment  20 ′, a second segment  30 ′, and a third segment  40 ′ including a substantial portion of the humeral head are each detached from the proximal end  12 ′ of the humerus. After removal of the humeral head, the proximal end of the humeral medullary canal may be shaped in order to accept an implant according to known methods. In one exemplary method, a hand reamer, for example, may be used at a proximal humeral bearing surface  14 ′ to remove bone material until an appropriately-shaped opening is formed in the proximal end  12 ′ of humerus  10 ′ for receiving an implant. Typically, successive reamers of increasing size are used in order to form an opening of the desired size. In many cases, bearing surface  14 ′ may not be as flat as shown. Most surfaces at a fracture site are irregularly shaped unless there is a clean break between adjacent fragments. Such a surface may be resected into a generally flat shape to receive a corresponding bearing surface of a trial and/or implant stem as shown in  FIG. 3 . 
         [0053]    Once an appropriate bearing surface  14  and opening is formed for receiving an implant, trialing is conducted to determine the proper size and location for the implant prior to implantation thereof. According to one example of the present disclosure, trialing includes inserting a trial stem  100 , as illustrated in  FIG. 4 , into the opening in the proximal end  12  of humerus  10 . Trial stem  100  may include a proximal portion  110  connected to a distal portion  120 , for example by welding, with an expansion bolt  130  positioned within the trial stem. Generally, proximal portion  110  is adapted for insertion into the proximal end  12  of a prepared humerus  10 . Proximal portion  110  may include a first catch aperture  112 , a trial recess  114 , two second catch apertures  116  (both not visible in  FIG. 4 ) and a driver recess  118 . Catch aperture  112  and driver recess  118  may be configured to mate with a trial cup, for example, as shown in  FIG. 7A  or as shown in greater detail with respect to the reverse cup humeral trial show in  FIG. 11A  and described in U.S. Pat. No. 8,545,511, the entire contents of which are hereby incorporated by reference herein. Trial recess  114  may be shaped to receive a corresponding portion of a trial humeral head, for example, as shown in  FIG. 11B . Trial recess  114  may have a longitudinal axis that is angled with respect to a longitudinal axis of distal portion  120  so as to substantially replicate the typical geometry of a shaft and neck of the native bone prior to a fracture situation as shown in  FIG. 3 . 
         [0054]    The distal portion  120  of trial stem  100  may be structured to fit within a prepared bone canal, preferably the medullary canal of the humerus  10 . Distal portion  120  projects along a longitudinal axis thereof from proximal portion  110  generally in the proximal-to-distal direction. Distal portion  120  may include a first arm  122  and a second arm  124  configured to move away from each other in cooperation with expansion bolt  130 , such as that described in U.S. Pat. No. 8,216,320, the entire contents of which are hereby incorporated by reference herein. Distal portion  120 , or a portion thereof, may define a cavity or configured to accept expansion bolt  130 , the cavity including a mating surface such as threads. 
         [0055]    Expansion bolt  130  may generally include a shaft  132  with a pointed distal tip  134 . A proximal end of expansion bolt  130  may include a head  136 , which may include a recess, such as a hex recess, to cooperate with a correspondingly shaped driving tool (not shown). A proximal end of shaft  132  may include a mating surface, such as threads  138 , configured to mate with a corresponding surface in the cavity of distal portion  120 . Although proximal portion  110 , distal portion  120 , and expansion bolt  130  may each be separate pieces prior to assembly, trial stem  100  is preferably provided to the end user as a single piece with the proximal and distal portions permanently connected, for example by welding, with the expansion bolt contained therein. 
         [0056]    An exemplary embodiment of stem implant  200  is illustrated in  FIG. 5A  and may be structurally similar to trial stem  100  in certain respects. Stem implant  200  may be monolithic with a proximal portion  210  and a distal portion  220 . Proximal portion  210  of stem implant  200 , shown in greater detail in  FIGS. 5B-D , may include a first contact surface  208  having a first catch aperture  212  and an implant recess  214  and a second contact surface  215  having two locking pin apertures  216  and a second catch aperture  218 . The apertures  212  and  218  similar to corresponding features on trial stem  100 , facilitate the connection between features of a trial cup with stem implant  300 . Implant recess  214  may be configured to accept a humeral head trial or implant, reverse cup humeral implant, or other compatible implant. Proximal portion  210  may also include a number of features to facilitate securing portions of humerus  10 , such as first segment  20  and second segment  30 , to stem implant  200 . For example, a first pair of suture holes  217   a  may be formed on a lateral-anterior side of proximal portion  210  and a second pair of suture holes  217   b  may be formed on a lateral-posterior side of the proximal portion. A third pair of suture holes  217   c  may be formed on a medial side of proximal portion  210 . The suture holes  217   a - c  may facilitate securing one or more bone fragments to stem implant  200  via sutures (not illustrated). One suture pocket  219   a  may be formed on the lateral-anterior side of proximal portion  210 , and may be connected to suture holes  217   a . Another suture pocket (not visible in  FIGS. 5A-D ) may be formed on the lateral-posterior side of proximal portion  210 , and may be connected to suture holes  217   b . The suture pockets may, for example, facilitate the insertion of a suture needle. 
         [0057]      FIGS. 6A-B  are exemplary embodiments of trial head and implant head assemblies  350 ,  350 ′. In  FIG. 6A , a trial head  325  is coupled to a stem implant  300  inserted into a resected humeral bone  310 , while in  FIG. 6B , an implant head  325 ′ is coupled to stem implant  300 . A base surface  328 ,  328 ′ of the respective trial head  325  and implant head  325 ′ lie on resection or neck line  330  of resected humerus  310 . As shown in  FIG. 6A , base surface  328  of trial head  325  sits flush against a corresponding first contact surface  308  when trial head  325  is securely coupled to stem implant  300 . In contrast, as shown in  FIG. 6B , when implant head  325 ′ is securely coupled to stem implant  300 , base surface  328 ′ of implant head  325 ′ is separated from first contact surface  308  such that implant head  325 ′ sits proudly on stem implant  300 . The gap between base surface  328 ′ and first contact surface  308  ensures that the tapers between the engagement portions of the implant head  325 ′ and stem implant  300  always engage. The gap between generally parallel base surface  328 ′ and first contact surface  308  may be defined as a linear distance D 1 . D 1  is generally 1-2 mm in length. The range of D 1  generally occurs due to the tolerances on the tapers of the implant head  325 ′ and the stem implant  300 . In a total or reverse shoulder case where you have a defined resection line  330 , this gap does not affect the final position of implant head  325 ′ because stem implant  300  will generally subside such that base surface  328 ′ of implant head  325 ′ lies adjacent resection line  330  and articulating surface  327 ′ of implant head  325 ′ will match the position of an articulating surface  327  of trial head  325  that was located during trialing. Implant head  325 ′ may also be impacted until base surface  328 ′ comes in contact with both resection line  330  and first contact surface  308  of stem implant  300 . 
         [0058]      FIGS. 7A-B  are exemplary embodiments of humeral cup trial and head assemblies  450 ,  450 ′. In  FIG. 7A , a trial cup  425  is coupled to a stem implant  400  inserted into a resected humeral bone  410 , while in  FIG. 7B , an implant cup  425 ′ is coupled to stem implant  400 . A base surface  428 ,  428 ′ of the respective trial cup  425  and implant cup  425 ′ lie on resection or neck line  430  of resected humerus  410 . As shown in  FIG. 7A , base surface  428  of trial cup  425  sits flush against a corresponding first contact surface  408  when trial cup  425  is securely coupled to stem implant  400 . In contrast, as shown in  FIG. 7B , when implant cup  425 ′ is securely coupled to stem implant  400 , base surface  428 ′ of implant cup  425 ′ is separated from first contact surface  408  such that implant cup  425 ′ sits proudly on stem implant  400 . The gap between base surface  428 ′ and first contact surface  408  ensures that the tapers between the engagement portions of the implant cup  425 ′ and stem implant  400  always engage. The gap between generally parallel base surface  428 ′ and first contact surface  408  may be defined by linear distance D 1  as shown in corresponding  FIG. 6B . D 1  therefore does not affect the final position of implant cup  425 ′ because stem implant  400  will generally subside such that base surface  428 ′ of implant cup  425 ′ lies adjacent resection line  430  and articulating surface  427 ′ of implant cup  425 ′ will match the position of an articulating surface  427  of trial cup  425  that was located during trialing. 
         [0059]      FIGS. 8A-B  are exemplary embodiments of trial head and implant head assemblies  450 ,  450 ′. However, in  FIGS. 8A-8B , as opposed to  FIGS. 6A-6B , the stem implants are inserted into fractured humeral bone rather than resected humeral bone. In most fracture situations a defined resection line cannot be produced. Therefore, separate instrumentation such as that described in U.S. Pat. Pub. No. 2015/0328015 titled “Guides for Fracture System” which is incorporated by reference herein in its entirety and/or skill of a surgeon is generally used to determine proper stem placement to achieve a desired location and orientation of an implant head. In  FIG. 8A , a trial head  525  is coupled to a stem implant  500  inserted into a fractured humeral bone  510 , while in  FIG. 8B , an implant head  525 ′ is coupled to stem implant  500 . A base surface  528  of trial head  525  lies on an anatomical neck line  530  as shown in  FIG. 8A . In contrast, as shown in  FIG. 8B , anatomical neck line  530  lies on first contact surface  508  and is separated from a base surface  528 ′ by linear distance D 1 . With a fracture setting, there is no resection plane to act as a reference for the seating of trial head  525  or implant head  525 ′. Further, subsiding of stem implant  500  is generally not possible due to lack of reference plane and the fact that the stem is typically cemented into the fractured humerus prior to impaction of head implant. Because of the gap between implant head  525 ′ and stem implant  500 , the implant head  525 ′ will generally sit approximately 1.5 mm higher than the trial head  525 . In other words, base surface  528 ′ or implant head  525 ′ sits approximately 1.5 mm from the anatomical neck line  530  when implant head  525 ′ is coupled to stem implant  500 . Such a situation would also occur in non-fracture settings where a reference resection plane is not available to determine the final head implant seating height or the stem is cemented prior to impaction of the head implant. 
         [0060]    In order to account for the gap between implant head  525 ′ and stem implant  500 , for example, a humeral trial adaptor  640  as shown for example in  FIGS. 9A and 9B  is utilized. Trial adaptor  640  has a superior surface  641  and an inferior surface  642 . Superior surface  641  and inferior surface  642  are preferably planar surfaces separated by linear distance D 1 . An engagement portion  643  protrudes inferiorly from inferior surface  642 . Engagement portion  643  has a contact surface  644  in which a protrusion  645  protrudes outwardly from. Trial adaptor includes a first aperture  646 , a second aperture  647  and a third aperture  648 . Trial adaptor  640  further includes first and second flexible retaining portions  649   a ,  649   b  that extend along a length of both first and second apertures  646 ,  647 . 
         [0061]      FIG. 10A  is a perspective view of a trial assembly  750  including trial adaptor  640  coupled to one embodiment of a trial cup  725  coupled to a trial insert  735 . Trial cup  725  includes a base surface  728  in which a first engagement portion  732  and a second engagement portion  734  extending outwardly therefrom. When trial adaptor  640  is coupled to trial cup  725 , first engagement portion  732  of trial cup  725  extends through first aperture  646  while second engagement portion  734  of trial cup  725  extends through third aperture  648 . First and second flexible retaining portions  649   a ,  649   b  come in contact with an outer surface of first engagement portion  732  of trial cup  725  and help to retain the coupling between trial adaptor  640  and trial cup  725 . As shown in  FIG. 10B , trial assembly  750  is coupled to an exemplary trial or implant stem  700 . In this embodiment, contact surface  644  of trial adaptor  640  is in contact with a second contact surface  715  of trial stem while inferior surface  642  is in contact with a first contact surface  708 . Base surface  728  is separated from first contact surface  708  by linear distance D 1 . 
         [0062]    In fracture or similar settings, trial adaptor  640  can therefore be used to account for the differences between the coupling of a trial cup or head with a trial or implant stem and an implant cup or head with an implant stem. During trialing, the surgeon or other operating room personal will use trial adaptor  640  along with a trial cup or head and a trial or implant stem which corresponds to a selected implant cup or head and the implant stem.  FIGS. 11A-B  are exemplary embodiments of humeral cup trial and head assemblies  850 ,  850 ′.  FIG. 11A  shows cup trial  825 , trial adaptor  840  and stem implant  800  coupled to one another. A first engagement portion  832  of cup trial  825  extends through trial adaptor  840  and into a first catch aperture  812  while a second engagement portion  834  of cup trial  825  extends through trial adaptor  840  and into a second catch aperture  818 . A base surface  828  of cup trial  825  is separated from a first contact surface  808  of stem implant by linear distance D 1 .  FIG. 11B  shows head trial  825 ′, trial adaptor  840  and stem implant  800  coupled to one another. An engagement portion  833 ′ of head trial  825 ′ extends through trial adaptor  840  and into a trial recess  814  of stem implant. A base surface  828 ′ of cup trial  825 ′ is separated from a first contact surface  808  of stem implant by linear distance D 1 . 
         [0063]      FIG. 12A  is a perspective view of another embodiment of a humeral trial adaptor  940  of the present invention. Trial adaptor  940  has a superior surface  941  and an inferior surface  942 . Superior surface  941  and inferior surface  942  are preferably planar surfaces separated by linear distance D 1 . An engagement portion  933  protrudes inferiorly from inferior surface  942 . Engagement portion  933  is adapted to be received, for example, in trial recess  814  of stem implant  800 . Trial adaptor  940  includes a first aperture  946  and a third aperture  948 . Trial adaptor  940  further includes first and second retaining portions  949   a ,  949   b  that extend along a length of first aperture  946 . 
         [0064]      FIG. 12B  is a perspective view of a trial assembly  1150  including the humeral trial adaptor  940  of  FIG. 12A  coupled to one embodiment of a humeral trial cup  1125 . Trial cup  1125  includes a base surface  1128  in which a first engagement portion  1132  and a second engagement portion  1134  extending outwardly therefrom. When trial adaptor  940  is coupled to trial cup  1125 , first engagement portion  1132  of trial cup  1125  extends through first aperture  946  while second engagement portion  1134  of trial cup  1125  extends through third aperture  1148 . First and second retaining portions  949   a ,  949   b  come in contact with an outer surface of first engagement portion  1132  of trial cup  1125  and help to retain the coupling between trial adaptor  940  and trial cup  1125 . 
         [0065]      FIG. 13A  is a perspective view of another embodiment of a humeral trial adaptor  1040  of the present invention. Trial adaptor  1040  has a superior surface  1041  and an inferior surface  1042 . Superior surface  1041  and inferior surface  1042  are preferably planar surfaces separated by linear distance D 1 . An engagement portion  1043  protrudes inferiorly from inferior surface  1042 . Engagement portion  1043  has a contact surface  1044  adapted to come in contact with a corresponding surface of a trial stem. Trial adaptor  1040  includes a second aperture  1047  surrounded by first and second retaining portions  1049   a ,  1049   b  that extend along a length of second aperture  1047 . 
         [0066]      FIG. 13B  is a perspective view of a trial assembly  1150 ′ including the humeral trial adaptor  1040  of  FIG. 13A  coupled to one embodiment of a humeral head trial  1125 ′. Head trial  1125 ′ includes a base surface  1128 ′ in which an engagement portion  1133 ′ extends outwardly therefrom. Engagement portion  1133 ′ of head trial  1125 ′ extends through second aperture  1047  of trial adaptor  1040  and is adapted to be received, for example, into trial recess  814  of stem implant  800 . First and second retaining portions  1049   a ,  1049   b  come in contact with an outer surface of engagement portion  1133 ′ of head trial  1125 ′ and help to retain the coupling between trial adaptor  1040  and head trial  1125 ′. A base surface  1128 ′ of head trial  1125 ′ is separated from a first contact surface  808  of stem implant  800  (not shown in  FIG. 13B ), for example, by linear distance D 1 . Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.