Patent Publication Number: US-11660213-B2

Title: Hip arthroplasty trial systems and associated medical devices, methods, and kits

Description:
RELATED APPLICATION 
     This application claims benefit of U.S. Nonprovisional patent application Ser. No. 16/565,890, filed on Sep. 10, 2019, which in turn claims the benefit of U.S. Provisional Application No. 62/841,700, filed on May 1, 2019. The disclosures of these related applications are hereby incorporated into this disclosure in their entirety. 
    
    
     FIELD 
     The disclosure relates to the field of medical devices. More particularly, the disclosure relates to hip arthroplasty trial systems and associated medical devices, methods, and kits. 
     BACKGROUND 
     When implanting a femoral head during a hip arthroplasty, surgeons currently utilize multiple head length options, which must be individually trialed, to determine the desired offset between the femoral head and a femoral stem. Each trial requires assembly and disassembly of the different head lengths to determine whether a desired offset has been achieved, which results in the hip being dislocated and relocated numerous times during the trial procedure. This multiple trial approach for determining a desired offset between a femoral head implant and a femoral stem in which the hip must be relocated numerous times has significant drawbacks, such as being complex, time consuming, and disrupting tissue. 
     A need exists, therefore, for new and improved hip arthroplasty trial systems and associated medical devices, kits, and methods. 
     SUMMARY OF SELECTED EXAMPLE EMBODIMENTS 
     Various hip arthroplasty trials systems, medical devices, methods, and kits are described herein. 
     An example hip arthroplasty trial system includes a head member, a spacer, a shaft, and a femoral stem. The head member has a head member first end, a head member second end, a head member first lengthwise axis, and a head member main body that defines a head member articulating surface and a head member first recess. The head member first recess extends into the head member main body along the head member first lengthwise axis and from the head member first end toward the head member second end. The spacer is disposed within the head member first recess and is moveable between a spacer first position and a spacer second position. The shaft is moveable between a shaft first position and a shaft second position. Movement of the shaft from its shaft first position to its shaft second position moves the spacer from its spacer first position to its spacer second position. The femoral stem has a femoral stem first end and a femoral stem second end. The femoral stem second end is disposed a first distance from the head member first end when the shaft is in the shaft first position and disposed a second distance from the head member first end when the shaft is in the shaft second position. The second distance is different than the first distance. 
     An example medical device has a head member, a spacer, a shaft, and a locking member. The head member has a head member first end, a head member second end, a head member first lengthwise axis, a head member second lengthwise axis, and a head member main body that defines a head member articulating surface, a head member first recess, a head member second recess, and a head member third recess. The head member first recess extends into the head member main body along the head member first lengthwise axis from the head member first end toward the head member second end. The head member second lengthwise axis extends through the head member second recess and intersects the head member first lengthwise axis. The head member second recess extends into the head member main body along the head member second lengthwise axis and is in communication with the head member first recess. The head member third recess extends into the head member main body and is in communication with the head member second recess. The spacer is disposed within the head member first recess and is moveable between a spacer first position and a spacer second position. The spacer has a spacer first end, a spacer second end, and a spacer length that extends from the spacer first end to the spacer second end. A first portion of the spacer length is disposed within the head member first recess when the spacer is in the spacer first position. A second portion of the spacer length is disposed within the head member first recess when the spacer is in the spacer second position. The first portion of the spacer length is greater than the second portion of the spacer length. The shaft is moveably disposed within the head member second recess and the shaft is moveable between a shaft first position and a shaft second position. Movement of the shaft from its shaft first position to its shaft second position moves the spacer from its spacer first position to its spacer second position. The locking member is disposed within the head member third recess and contacts the shaft. The locking member is adapted to releasably fix the shaft in its shaft first position and in its shaft second position. 
     An example method of completing a hip arthroplasty trial on a femur comprises: obtaining a medical device for use in a hip arthroplasty trial, the medical device comprises a head member, a shaft, and a locking member; implanting a femoral stem into a femur; positioning the head member on the femoral stem; moving the shaft in situ in a first direction such that the head member moves away from the femoral stem until a desired offset between the head member and the femoral stem has been achieved; moving the shaft in situ in a second direction such that the head member moves toward the femoral stem; obtaining a femoral head implant that corresponds to the desired offset between the head member and the femoral stem; removing head member from the femoral stem; and positioning the femoral head implant on the femoral stem. 
     Additional understanding of the example hip arthroplasty trial systems, medical devices, methods, and kits can be obtained by review of the detailed description, below, and the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a conventional femoral head trial system for use in a hip arthroplasty. 
         FIG.  1 A  illustrates another conventional femoral head trial system for use in a hip arthroplasty. 
         FIG.  2    is a perspective view of an example hip arthroplasty trial system that includes a medical device and a femoral stem. 
         FIG.  3    is an exploded view of the hip arthroplasty trial system illustrated in  FIG.  2   . 
         FIG.  4    is an exploded view of the medical device of the hip arthroplasty trial system illustrated in  FIG.  2   . 
         FIG.  5    is a perspective view of the medical device of the hip arthroplasty trial system illustrated in  FIG.  2   . 
         FIG.  6    is a perspective view of the head member of the medical device illustrated in  FIG.  2   . 
         FIG.  7    is a side view of the medical device illustrated in  FIG.  2   . 
         FIG.  8    is another side view of the medical device illustrated in  FIG.  2   . 
         FIG.  9   . is a partial exploded view of the head member and the locking member of the medical device illustrated in  FIG.  2   . 
         FIG.  10    is a partial perspective view of the head member and the locking member of the medical device illustrated in  FIG.  2   . 
         FIG.  11    is an exploded view of the hip arthroplasty trial system illustrated in  FIG.  2   . 
         FIG.  12    is a perspective view of the spacer of the medical device illustrated in  FIG.  2   . 
         FIG.  13    is a cross-sectional view of the spacer of the medical device illustrated in  FIG.  2    taken along the lengthwise axis of the spacer. 
         FIG.  14    is a perspective view of the head member of the medical device illustrated in  FIG.  2   . 
         FIG.  15    is another perspective view of the head member of the medical device illustrated in  FIG.  2   . 
         FIG.  16    is a cross-sectional view of the head member of the medical device illustrated in  FIG.  2    taken along the first lengthwise axis of the head member. 
         FIG.  17    is a perspective view of the shaft of the medical device illustrated in  FIG.  2   . 
         FIG.  18    is a cross-sectional view of the shaft of the medical device illustrated in  FIG.  2    taken along an axis orthogonal to the lengthwise axis of the shaft. 
         FIG.  19    is another perspective view of the shaft of the medical device illustrated in  FIG.  2   . 
         FIG.  20    is a perspective view of the locking member of the medical device illustrated in  FIG.  2   . 
         FIG.  21    is a top view of the locking member of the medical device illustrated in  FIG.  2   . The locking member is shown in the first position. 
         FIG.  22    is a top view of the locking member of the medical device illustrated in  FIG.  2   . The locking member is shown in the second position. 
         FIG.  23    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  2   . The hip arthroplasty trial system is shown in the first position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  23   . 
         FIG.  24    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  2   . The hip arthroplasty trial system is shown in the second position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  24   . 
         FIG.  25    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  2   . The hip arthroplasty trial system is shown in the third position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  25   . 
         FIG.  26    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  2   . The hip arthroplasty trial system is shown in the fourth position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  26   . 
         FIG.  27    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  2    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the first position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  27   . 
         FIG.  28    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  2    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the second position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  28   . 
         FIG.  29    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  2    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the third position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  29   . 
         FIG.  30    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  2    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the fourth position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  30   . 
         FIG.  31    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  2   . The hip arthroplasty trial system is shown in the second position. 
         FIG.  32    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  2   . The locking member is shown in the second position. 
         FIG.  33    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  2   . The locking member is shown in the first position. 
         FIG.  34    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  2   . The locking member is shown in the second position. 
         FIG.  35    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  2   . The locking member is shown in the first position. 
         FIG.  36    is a partial sectional view of the hip arthroplasty trial system illustrated in  FIG.  2   . The locking member is shown in the first position. 
         FIG.  37    is a partial sectional view of the hip arthroplasty trial system illustrated in  FIG.  2   . The locking member is shown in the second position. 
         FIG.  38    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  2   . The hip arthroplasty trial system is shown in the second position. 
         FIG.  39    illustrates a portion of a conventional femoral head trial system attached to a femoral stem. 
         FIG.  40    is a perspective view of another example hip arthroplasty trial system that includes a medical device and a femoral stem. 
         FIG.  41    is another perspective view of the hip arthroplasty trial system illustrated in  FIG.  40   . 
         FIG.  42    is an exploded view of the hip arthroplasty trial system illustrated in  FIG.  40   . 
         FIG.  43    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  40   . 
         FIG.  44    is a perspective view of the head member of the medical device illustrated in  FIG.  40   . 
         FIG.  45    is a cross-sectional view of the head member of the medical device illustrated in  FIG.  40    taken along the first lengthwise axis of the head member. 
         FIG.  46    is a perspective view of the head member of the medical device illustrated in  FIG.  40   . 
         FIG.  47    is an exploded view of the medical device illustrated in  FIG.  40   . 
         FIG.  48    is a side view of the medical device illustrated in  FIG.  40   . 
         FIG.  49    is another side view of the medical device illustrated in  FIG.  40   . 
         FIG.  50    is an exploded view of the medical device illustrated in  FIG.  40   . 
         FIG.  51    is a perspective view of the spacer of the medical device illustrated in  FIG.  40   . 
         FIG.  52    is a cross-sectional view of the spacer of the medical device illustrated in  FIG.  40    taken along the lengthwise axis of the spacer. 
         FIG.  53    is a perspective view of the o-ring of the medical device illustrated in  FIG.  40   . 
         FIG.  54    is a cross-sectional view of the shaft of the medical device illustrated in  FIG.  40    taken along an axis orthogonal to the lengthwise axis of the shaft. 
         FIG.  55    is a perspective view of the shaft of the medical device illustrated in  FIG.  40   . 
         FIG.  56    is another perspective view of the shaft of the medical device illustrated in  FIG.  40   . 
         FIG.  57    is a perspective view of the locking member of the medical device illustrated in  FIG.  40   . 
         FIG.  58    is a top view of the locking member of the medical device illustrated in  FIG.  40   . The locking member is shown in the first position. 
         FIG.  59    is a top view of the locking member of the medical device illustrated in  FIG.  40   . The locking member is shown in the second position. 
         FIG.  60    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  40   . The hip arthroplasty trial system is shown in the first position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  60   . 
         FIG.  61    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  40   . The hip arthroplasty trial system is shown in the second position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  61   . 
         FIG.  62    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  40   . The hip arthroplasty trial system is shown in the third position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  62   . 
         FIG.  63    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  40   . The hip arthroplasty trial system is shown in the fourth position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  63   . 
         FIG.  64    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  40    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the first position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  64   . 
         FIG.  65    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  40    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the second position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  65   . 
         FIG.  66    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  40    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the third position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  66   . 
         FIG.  67    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  40    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the fourth position. The position of a conventional modular trial system is shown in phantom for illustrative purposes in  FIG.  67   . 
         FIG.  68    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  40   . The hip arthroplasty trial system is shown in the first position. 
         FIG.  69    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  40   . The hip arthroplasty trial system is shown in the third position. 
         FIG.  70    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  40   . The locking member is shown in the second position. 
         FIG.  70 A  is a partial exploded view of the hip arthroplasty trial system illustrated in  FIG.  40   . The locking member is shown in the second position. 
         FIG.  71    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  40   . The locking member is shown in the first position. 
         FIG.  71 A  is a partial exploded view of the hip arthroplasty trial system illustrated in  FIG.  40   . The locking member is shown in the first position. 
         FIG.  72    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  40   . The hip arthroplasty trial system is shown in the second position. 
         FIG.  72 A  is a partial exploded view of the hip arthroplasty trial system illustrated in  FIG.  40   . 
         FIG.  73    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  40   . The locking member is shown in the second position. 
         FIG.  74    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  40   . The locking member is shown in the first position. 
         FIG.  75    is a partial sectional view of the hip arthroplasty trial system illustrated in  FIG.  40   . The locking member is shown in the second position. 
         FIG.  76    is a partial sectional view of the hip arthroplasty trial system illustrated in  FIG.  40   . The locking member is shown in the first position. 
         FIG.  77    is a schematic illustration of an exemplary method of completing a hip arthroplasty trial on a femur. 
         FIG.  78    is a perspective view of another example hip arthroplasty trial system that includes a medical device and a femoral stem. 
         FIG.  79    is an exploded view of the hip arthroplasty trial system illustrated in  FIG.  78   . 
         FIG.  80    is a perspective view of the head member of the medical device illustrated in  FIG.  78   . 
         FIG.  81    is a cross-sectional view of the head member of the medical device illustrated in  FIG.  78    taken along the first lengthwise axis of the head member. 
         FIG.  82    is a perspective view of the spacer of the medical device illustrated in  FIG.  78   . 
         FIG.  83    is a cross-sectional view of the spacer of the medical device illustrated in  FIG.  78    taken along the lengthwise axis of the spacer. 
         FIG.  84    is a perspective view of the shaft of the hip arthroplasty trial system illustrated in  FIG.  78   . 
         FIG.  85    is another perspective view of the shaft of the hip arthroplasty trial system illustrated in  FIG.  78   . 
         FIG.  86    is perspective view of the femoral stem illustrated in  FIG.  78   . 
         FIG.  87    is a partial perspective view of the femoral stem illustrated in  FIG.  78   . 
         FIG.  88    is another partial perspective view of the femoral stem illustrated in  FIG.  78   . 
         FIG.  89    is a partial cross-sectional view of the femoral stem illustrated in  FIG.  78    taken along the second lengthwise axis of the femoral stem. 
         FIG.  90    is a partial cross-sectional view of the femoral stem illustrated in  FIG.  78    taken along the second lengthwise axis of the femoral stem. 
         FIG.  91    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  78   . 
         FIG.  92    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  78    taken along the second lengthwise axis of the femoral stem. 
         FIG.  93    is a partial top view of the hip arthroplasty trial system illustrated in  FIG.  78   . The hip arthroplasty trial system is shown in the first position. 
         FIG.  94    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  78    taken along the second lengthwise axis of the femoral stem. The hip arthroplasty trial system is shown in the first position. 
         FIG.  95    is a partial top view of the hip arthroplasty trial system illustrated in  FIG.  78   . The hip arthroplasty trial system is shown in the second position. 
         FIG.  96    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  78    taken along the second lengthwise axis of the femoral stem. The hip arthroplasty trial system is shown in the second position. 
         FIG.  97    is a partial top view of the hip arthroplasty trial system illustrated in  FIG.  78   . The hip arthroplasty trial system is shown in the third position. 
         FIG.  98    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  78    taken along the second lengthwise axis of the femoral stem. The hip arthroplasty trial system is shown in the third position. 
         FIG.  99    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  78   . The hip arthroplasty trial system is shown in the fourth position. 
         FIG.  100    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  78    taken along the second lengthwise axis of the femoral stem. The hip arthroplasty trial system is shown in the fourth position. 
         FIG.  101    is a perspective view of another example hip arthroplasty trial system that includes a medical device and a femoral stem. 
         FIG.  102    is an exploded view of the hip arthroplasty trial system illustrated in  FIG.  101   . 
         FIG.  103    is a perspective view of the femoral stem illustrated in  FIG.  101   . 
         FIG.  104    is a partial perspective view of the femoral stem illustrated in  FIG.  101   . 
         FIG.  105    is another partial perspective view of the femoral stem illustrated in  FIG.  101   . 
         FIG.  106    is a partial perspective view of the hip arthroplasty trial system illustrated in  FIG.  101   . 
         FIG.  107    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  101    taken along the first lengthwise axis of the head member. 
         FIG.  108    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  101   . The hip arthroplasty trial system is shown in the first position. 
         FIG.  109    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  101    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the first position. 
         FIG.  110    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  101   . The hip arthroplasty trial system is shown in the second position. 
         FIG.  111    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  101    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the second position. 
         FIG.  112    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  101   . The hip arthroplasty trial system is shown in the third position. 
         FIG.  113    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  101    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the third position. 
         FIG.  114    is a partial side view of the hip arthroplasty trial system illustrated in  FIG.  101   . The hip arthroplasty trial system is shown in the fourth position. 
         FIG.  115    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  101    taken along the first lengthwise axis of the head member. The hip arthroplasty trial system is shown in the fourth position. 
         FIG.  116    is a perspective view of another example hip arthroplasty trial system that includes a medical device and a femoral stem. 
         FIG.  117    is an exploded view of the hip arthroplasty trial system illustrated in  FIG.  116   . 
         FIG.  118    is an exploded view of an alternative femoral stem for inclusion in a hip arthroplasty trial system. 
         FIG.  119    is a perspective view of the head member of the medical device illustrated in  FIG.  116   . 
         FIG.  120    is a cross-sectional view of head member of the medical device illustrated in  FIG.  116    taken along the first lengthwise axis of the head member. 
         FIG.  121    is a partial top view of the hip arthroplasty trial system illustrated in  FIG.  116   . The hip arthroplasty trial system is shown in the first position. 
         FIG.  122    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  116    taken along the second lengthwise axis of the femoral stem. The hip arthroplasty trial system is shown in the first position. 
         FIG.  123    is a partial top view of the hip arthroplasty trial system illustrated in  FIG.  116   . The hip arthroplasty trial system is shown in the second position. 
         FIG.  124    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  116    taken along the second lengthwise axis of the femoral stem. The hip arthroplasty trial system is shown in the second position. 
         FIG.  125    is a partial top view of the hip arthroplasty trial system illustrated in  FIG.  116   . The hip arthroplasty trial system is shown in the third position. 
         FIG.  126    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  116    taken along the second lengthwise axis of the femoral stem. The hip arthroplasty trial system is shown in the third position. 
         FIG.  127    is a partial top view of the hip arthroplasty trial system illustrated in  FIG.  116   . The hip arthroplasty trial system is shown in the fourth position. 
         FIG.  128    is a partial cross-sectional view of the hip arthroplasty trial system illustrated in  FIG.  116    taken along the second lengthwise axis of the femoral stem. The hip arthroplasty trial system is shown in the fourth position. 
         FIG.  129    is a schematic illustration of another exemplary method of completing a hip arthroplasty trial on a femur. 
         FIG.  130    is a schematic illustration of another exemplary method of completing a hip arthroplasty trial on a femur. 
         FIG.  131    illustrates an example kit that includes a hip arthroplasty trial system. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description and the appended drawings describe and illustrate various embodiments of hip arthroplasty trial systems, medical devices for hip arthroplasty, methods of using a hip arthroplasty trial system, and kits. The description and illustration of these examples are provided to enable one skilled in the art to make and use a hip arthroplasty trial system, a medical device, a kit that includes a hip arthroplasty trial system, and to practice a method of using a hip arthroplasty trial system and/or a medical device. They are not intended to limit the scope of the claims in any manner. 
       FIGS.  2  through  38    illustrate a first example hip arthroplasty trial system  1  that includes a medical device  10  and a femoral stem  20 . The medical device  10  has a head member  12 , a spacer  14 , a shaft  16 , and a locking member  18 . Some figures illustrate the medical device  10  releasably attached to a femoral stem  20 , such as  FIG.  2   . 
     As shown in  FIGS.  4  through  10 ,  36 , and  37   , the head member  12  (e.g., trial head member) has a head member first end  24 , a head member second end  26 , a head member first lengthwise axis  25 , a head member second lengthwise axis  27 , and a head member main body  28  that defines a head member articulating surface  30 , a head member first recess  32 , a head member second recess  34 , a head member third recess  36 , a head member first passageway  38 , a head member second passageway  40 , and a head member third passageway  42 . The head member first lengthwise axis  25  extends through the head member first recess  32  and the head member second end  26 . The head member second lengthwise axis  27  extends through the head member second recess  34  and intersects the head member first lengthwise axis  25  at an angle  29 . The head member first recess  32  extends into the head member main body  28  along the head member first lengthwise axis  25  and from the head member first end  24  toward the head member second end  26 . The head member second recess  34  extends into the head member main body  28  along the head member second lengthwise axis  27  and is in communication with the head member first recess  32 . The head member second recess  34  is positioned a first distance  35  from the head member first end  24  and a second distance  37  from the head member second end  26  that is less than the first distance  35  to accommodate the geometry of the shaft  16 , as described in more detail herein. The head member third recess  36  extends into the head member main body  28  along the second lengthwise axis  27  and is in communication with the head member second passageway  34 . However, in alternative embodiments, a head member third recess could extend into a head member main body along an axis that is parallel, or disposed at an angle, to an axis on which a head member second recess is defined. Each of the head member first passageway  38  and the head member second passageway  40  extends from the head member second recess  34  to the head member third recess  36 . The head member third passageway  42  extends from the head member second recess  34  to the head member articulating surface  30 . 
     In the illustrated embodiment, the head member first recess  32  has an inside diameter  33  that tapers from the head member first end  24  towards the head member second end  26  and the head member second recess  34  has a second recess first portion  44  and a second recess second portion  46 . However, alternative embodiments could define a head member first recess that has a constant inside diameter. The second recess first portion  44  is adapted to receive a portion of the cam projection  72  and the cam first boss  70 , as described in more detail herein, and has a first cross-sectional configuration at the head member articulating surface  30 . The second recess second portion  46  is adapted to receive the cam projection  72 , as described in more detail herein, and to allow the cam projection  72  to rotate about the second lengthwise axis  27  within the second recess second portion  46 . The second recess second portion  46  has a second, different, cross-sectional configuration at the intersection between the head member first lengthwise axis  25  and the head member second lengthwise axis  27 . The first cross-sectional configuration is taken along a first hypothetical plane  45  orthogonal to the second lengthwise axis  27  and the second cross-sectional configuration is taken along a second hypothetical plane  47  orthogonal to the second lengthwise axis  27 . 
     A head member second lengthwise axis can be disposed at any suitable angle relative to a head member first lengthwise axis and selection of a suitable angle to position a head member second lengthwise axis relative to a head member first lengthwise axis can be based on various considerations, including the structural arrangement of a shaft intended to be used in a medical device. Examples of angles considered suitable to position a head member second lengthwise axis relative to a head member first lengthwise axis include angles equal to, greater than, less than, or about 45 degrees, 90 degrees, 135 degrees, angles between about 10 degrees and about 170 degrees, angles between about 45 degrees and about 135 degrees, and any other angle considered suitable for a particular embodiment. In the illustrated embodiment, the angle  29  is equal to about 90 degrees. A head member can have any suitable outside diameter that extends from a first end of a head member to a second end of a head member. Examples of outside diameters considered suitable for a head member include outside diameters equal to, greater than, less than, or about 28 millimeters, 32 millimeters, 36 millimeters, outside diameters between about 20 millimeters and about 45 millimeters, and any other outside diameter considered suitable for a particular embodiment. 
     In the illustrated embodiment, the head member first end  24  is disposed a first distance from second end of the femoral stem  20  when the head member  24  is in the first position, as shown in  FIGS.  23  and  27   . The head member first end  24  is disposed a second distance from the second end of the femoral stem  20  when the head member  12  is in the second position, as shown in  FIGS.  24  and  28   . The head member first end  24  is disposed a third distance from the second end of the femoral stem  20  when the head member  12  is in the third position, as shown in  FIGS.  25  and  29   . The head member first end  24  is disposed a fourth distance from the second end of the femoral stem  20  when the head member  12  is in the fourth position, as shown in  FIGS.  26  and  30   . The first distance is greater than the second distance. The second distance is greater than the third distance. The third distance is greater than the fourth distance. 
     In the illustrated embodiment, the spacer  14  is disposed within the head member first recess  32  and is moveable between a spacer first position, a spacer second position, a spacer third position, and a spacer fourth position relative to the head member  12 . As shown in  FIGS.  12  and  13   , the spacer  14  has a spacer first end  50 , a spacer second end  52 , a spacer lengthwise axis  51 , a spacer length  53  that extends from the spacer first end  50  to the spacer second end  52 , and a spacer main body  54  that defines a spacer passageway  56  and a plurality of spacer grooves  57 . The spacer passageway  56  extends from the spacer first end  50  to the spacer second end  52  and tapers from the spacer second end  52  to the spacer first end  50 . Each groove of the plurality of spacer grooves  57  extends into the spacer main body  54  and is located a distance from the spacer first end  50 . A first spacer groove  59  is located a first distance  61  from the spacer first end  50 . A second spacer groove  63  is located a second distance  65  from the first spacer groove  59 . A third spacer groove  67  is located a third distance  69  from the second spacer groove  63 . The plurality of spacer grooves  57  is considered advantageous at least because the plurality of spacer grooves  57  provides a mechanism for measuring the distance the spacer  14  has traveled relative to the head member  12 . While a plurality of spacer grooves  57  have been illustrated, alternative embodiments can include any suitable marker or other structure to assist with measuring the distance a spacer has traveled relative to a head member. 
     A first portion  58  of the spacer length  53  is disposed within the head member first recess  32  when the spacer  14  is in the spacer first position, as shown in  FIGS.  23  and  27   . A second portion  60  of the spacer length  53  is disposed within the head member first recess  32  when the spacer  14  is in the spacer second position, as shown in  FIGS.  24  and  28   . A third portion  62  of the spacer length  53  is disposed within the head member first recess  32  when the spacer  14  is in the spacer third position, as shown in  FIGS.  25  and  29   . A fourth portion  64  of the spacer length  53  is disposed within the head member first recess  32  when the spacer  14  is in the spacer fourth position, as shown in  FIGS.  26  and  30   . The first portion  58  of the spacer length  53  is greater than the second portion  60  of the spacer length  53 . The second portion  60  of the spacer length  53  is greater than the third portion  62  of the spacer length  53 . The third portion  62  of the spacer length  53  is greater than the fourth portion  64  of the spacer length  53 . The location of a conventional modular neck trial system is shown in phantom for illustrative purposes in  FIGS.  23  through  30   . 
     While the spacer  14  has been illustrated as separate from the head member  12 , a spacer can be integrated into a head member such that each of the spacer and the head member forms a single, unitary component of a medical device. This alternative configuration of a head member and a spacer allows the spacer to be moveably disposed within a femoral stem such that the spacer can transition from a spacer first position, a spacer second position, a spacer third position, and/or a spacer fourth position relative to the femoral stem, as described in more detail herein. This alternative configuration decreases the number of components included in a medical device and/or a hip arthroplasty trial system. 
     While the spacer  14  has been illustrated as separate from the femoral stem  20 , a spacer can be integrated into a femoral stem such that each of the spacer and the femoral stem forms a single, unitary component of a medical device. This alternative configuration of a spacer and a femoral stem allows the spacer to be moveably disposed within a head member such that the spacer can transition from a spacer first position, a spacer second position, a spacer third position, and/or a spacer fourth position relative to the head member. This alternative configuration decreases the number of components included in a medical device and/or a hip arthroplasty trial system. 
     The shaft is moveably disposed within the head member second recess  34  and contacts the second end of a femoral head when the head is releasably attached to a femoral stem. Alternatively, a spacer can contact both a second end of a femoral stem and a spacer or just a spacer, depending on the structural arrangement of the components. Any suitable shaft can be included in a medical device and selection of a suitable shaft can be based on various considerations, including the structural arrangement of a head member and/or spacer. For example, the shaft  16  included in the illustrated medical device  10  is a cam  68  rotatably disposed within the head member second recess  34 . Alternative embodiments, however, can include any suitable shaft and/or spacer capable of accomplishing translation of a spacer and/or femoral stem as described herein. For example, a shaft can comprise a threaded member that interacts with a threaded spacer and/or femoral stem to achieve translation of the spacer, as described herein. Alternatively, a spacer can be a telescoping member that interacts with a shaft to achieve translation of the spacer, as described herein. 
     As shown in  FIGS.  17  through  19  and  23  through  30   , the cam  68  is rotatable about the head member second lengthwise  27  axis and has a cam first boss  70 , a cam projection  72  attached to the cam first boss  70 , a cam second boss  74  attached to the cam projection  72 , and a cam main body  76  that defines a cam groove  78 , a plurality of cam detents  80 , a cam recess  82 , a cam indicator  84 , and a cam projection first end  88 . The cam projection  72  is disposed between the cam first boss  70  and the cam second boss  74  and contacts the second end of the femoral stem  20 , as shown in  FIGS.  27 ,  28 ,  29 , and  30   , and/or the second end of a spacer when the spacer is releasably attached to a femoral stem. The cam groove  78  is defined on the cam second boss  74  and extends to a cam groove base  86 . The cam groove  78  is adapted to receive a locking member first projection  96  and a locking member second projection  98 , as described in more detail herein. Each detent of the plurality of cam detents  80  extends from the cam groove base  86 , into the cam main body  76 , and is adapted to receive a locking member first projection  96  or a locking member second projection  98 , as described in more detail herein. The cam recess  82  extends into the cam first boss  70  and has a hexagonal cross-sectional configuration taken along a hypothetical plane orthogonal to the second lengthwise axis  27 . However, alternative embodiments can include a cam recess that defines any suitable cross-sectional configuration capable of receiving a tool to move a cam between its various positions. The cam indicator  84  is disposed on the cam first boss  70  and has a lengthwise axis  85  that orthogonally intersects a plane  87  that contains the cam projection first end  88 . The cam indicator  84  provides a mechanism for illustrating to a user of the medical device  10  the position of the cam projection first end  88  relative to the spacer  14 . 
     The cam  68  is moveable between a cam first position, as shown in  FIGS.  23  and  27   , a cam second position, as shown in  FIGS.  24  and  28   , a cam third position, as shown in  FIGS.  25  and  29   , and a cam fourth position, as shown in  FIGS.  26  and  30   . Movement of the cam  68  from its cam first position to its cam second position moves the spacer  14  from its spacer first position to its spacer second position and the femoral stem  20  from its first position to its second position, and vice versa, as shown in  FIGS.  23 ,  24 ,  27 , and  28   . Movement of the cam  68  from its cam second position to its cam third position moves the spacer  14  from its spacer second position to its spacer third position and the femoral stem  20  from its second position to its third position, and vice versa, as shown in  FIGS.  24 ,  25 ,  28 , and  29   . Movement of the cam  68  from its cam third position to its cam fourth position moves the spacer  14  from its spacer third position to its spacer fourth position and the femoral stem  20  from its third position to its fourth position, and vice versa, as shown in  FIGS.  25 ,  26 ,  29 , and  30   . 
     In the illustrated embodiment, the locking member  18  is disposed within the head member third recess  36 , contacts the shaft  16 , as shown in  FIGS.  32 ,  33 ,  36 , and  37   , is adapted to releasably attach the shaft  16  to the head member  12 , and releasably fix the shaft  16  in its shaft first position, shaft second position, shaft third position, and shaft fourth position. As shown in  FIGS.  20  through  22   , the locking member  16  has a first end  90 , a second end  92 , and a main body  94  that defines a locking member first projection  96  and a locking member second projection  98 . As shown in  FIGS.  36  and  37   , the locking member first projection  96  extends through the head member first passageway  38  and the locking member second projection  98  extends through the head member second passageway  40 . 
     The locking member  18  is moveable between a locking member first position, as shown in  FIGS.  21  and  36   , and a locking member second position, as shown in  FIGS.  22  and  37   . The locking member  18  is biased to the locking member first position. When the locking member  18  is in the first position, the locking member first projection  96  is disposed within a first detent of the plurality of cam detents  80 , the locking member second projection  98  is disposed within a second detent of the plurality of cam detents  80 , and the locking member first projection  96  and the locking member second projection  98  are separated by a first length  97 . When the locking member  18  is in the second position, the locking member first projection  96  is disposed within the cam groove  78 , the locking member second projection  98  is disposed within the cam groove  78 , and the locking member first projection  96  and the locking member second projection  98  are separated by a second length  99 . The second length  99  is greater than the first length  97 . 
     In use, the interaction between the shaft  16  and the locking member  18  allows a user, such as a surgeon, to move the shaft  16  such that the spacer  14  and/or femoral stem  20  is/are disposed at predetermined first, second, third, and/or a fourth positions relative to the head member  12  in situ. For example, the interaction between the locking member first and second projections  96 ,  98  and the plurality of cam detents  80  allow the user to releasably fix the spacer  14  in a predetermined position. Since the user moves the shaft  16  in situ, movement of the shaft  16  between the first, second, third and fourth positions does not require a user to remove the head member  12  or the spacer  14  when the user is determining a desired offset for a patient&#39;s femoral head implant. Rather, the user can determine a desired offset for a femoral head implant more efficiently during the hip arthroplasty trial since the head member  12  and the spacer  14  remain in the patient during the entire hip trial process. 
     In use, the femoral stem  20  is releasably attached to the medical device  10  (e.g., head member  12 , spacer  14 ) during a hip arthroplasty trial and is used with a selected femoral head implant. The compatibility of the femoral stem  20  with the medical device  10  is considered advantageous at least because a user does not need to remove the medical device  10  or the femoral stem  20  during the hip arthroplasty trial procedure and the femoral stem  20  is ultimately used with, and interacts with, both the trial head member  10  and the final femoral head implant. The compatibility between the femoral stem  20  and the medical device  10  allows the user to perform the trial and implantation processes quicker and more efficiently as compared to conventional devices used in hip arthroplasty trials since the hip does not need to be displaced or relocated between each adjustment of the shaft between its first, second, third, and forth positions. For example, a user is able to perform an initial trial by adjusting the medical device  10  (e.g., shaft, spacer) in situ by applying a rotational force on the shaft  16  (e.g., cam  68 ) causing the spacer  14  to advance out of the head member  12 , as described herein, to perform an initial trial. Subsequently, a user is able to perform a final trial by implanting a femoral stem (e.g., femoral stem  20 ), attaching the head member  12  to the femoral stem, and adjusting the medical device  10  (e.g., shaft, spacer) in situ by applying a rotational force on the shaft  16  (e.g., cam  68 ) causing the spacer  14  and femoral stem  20  to advance away from, or toward, the head member  12 , as described herein. This allows a user, for example, to start with the shortest total length of the trial system (e.g., the shaft  16  is in the first position) and adjust up (e.g., move the shaft  16  to send position) to achieve proper tension and then adjust down (e.g., move the shaft  16  to the first position) to remove the medical device  10  and implant the final head implant. Thus, a user is able to accomplish both an initial trial and a final trial using the head member  12 . 
       FIGS.  40  through  76    illustrate a second example hip arthroplasty trial system  100  that includes a medical device  110  and a femoral stem  120 . Medical device  110  is similar to the medical device  10  illustrated in  FIGS.  2  through  38    and described above, except as detailed below. The medical device  110  has a head member  112 , a spacer  114 , a shaft  116 , and a locking member  118 . Some figures illustrate the medical device  110  releasably attached to a femoral stem  120 . 
     In the illustrated embodiment, the head member first passageway  138  has a first inside diameter  139 , a head member second inside diameter  141 , and the head member main body  128  defines a head member fourth recess  143  that extends from the head member third recess  136  and toward the head member second lengthwise axis  127 . However, in alternative embodiments, a head member fourth recess can extend from a head member third recess and toward any of feature of a head member. The head member first inside diameter  139  is defined at the head member first end  124  and the head member second inside diameter  141  is defined between the head member first end  124  and the head member second passageway  140 . The head member second inside diameter  141  is less than the head member first inside diameter  139 . The locking member  118  defines a locking member third projection  195  disposed within the head member fourth recess  143 . 
     In the illustrated embodiment, the spacer  114  has a spacer first outside diameter  171  at the spacer first end  150 , a spacer second outside diameter  173  at the spacer second end  152  that is less than the spacer first outside diameter  171 , and the cam main body  176  defines a cam recess  175  that extends into the cam projection  172 . 
     In the illustrated embodiment, the medical device comprises an o-ring  191  that is disposed within a groove  179  of the plurality of spacer grooves  157 . The o-ring  191  is considered advantage at least because the o-ring  191  provides a mechanism to maintain the position of the spacer  114  relative to the head member  112  during use. 
     While the head members, the spacers, the shafts, the cams, the locking mechanisms, and the femoral stems have been illustrated as having a particular structural arrangement, a head member, a spacer, a shaft, a cam, a locking mechanism, and a femoral stem can have any suitable structural arrangement. Selection of a suitable structural arrangement for a head member, a spacer, a shaft, a cam, a locking mechanism, and a femoral stem can be based on various considerations, including the material that forms a head member, a spacer, a shaft, a cam, a locking mechanism, and/or a femoral stem. 
     A head member, a spacer, a shaft, a cam, a locking mechanism, an o-ring, and a femoral stem can be formed of any suitable material and selection of a suitable material can be based on various considerations, including the material forming a hip intended to be used with a hip arthroplasty trial system and/or medical device. Examples of materials considered suitable to form a head member, a spacer, a shaft, a cam, a locking mechanism, and/or a femoral stem include biocompatible materials, materials that can be made biocompatible, ceramics, polymers, polyethylene, ultra-high-molecular-weight polyethylene (UHMWPE), metals, tantalum, titanium (Ti), cobalt alloys (e.g., cobalt-chromium (CoCr), cobalt-chromium-molybdenum (CoCrMo)), combinations of the materials described herein, and any other material considered suitable for a particular embodiment. Examples of materials considered suitable to form an o-ring include silicone, the materials described herein, and any other material considered suitable for a particular embodiment. 
     Various methods of completing a hip arthroplasty trial (e.g., using a medical device for a hip arthroplasty trial) are described herein. While the methods described herein are shown and described as a series of acts, it is to be understood and appreciated that the methods are not limited by the order of acts, as some acts may in accordance with these methods, occur in the order shown and/or described, in different orders, and/or concurrently with other acts described herein. 
       FIG.  77    is a schematic illustration of an exemplary method  200  of completing a hip arthroplasty trial on a femur using a medical device. 
     A step  202  comprises obtaining a medical device for use in a hip arthroplasty trial. Another step  204  comprises positioning a shaft within a head member second recess. Another step  206  comprises positioning a locking member within a head member third recess such that the shaft is releasably attached to the head member. Another step  208  comprises positioning the shaft in a first position. Another step  210  comprises positioning a spacer on an end of a femoral stem. Another step  212  comprises positioning the spacer within the head member first recess. Another step  214  comprises determining whether a desired offset between the head member and the femoral stem has been achieved. Another step  216  comprises moving the shaft such that the spacer translates relative to the head member. Another step  218  comprises determining whether a desired offset between the head member and the femoral stem has been achieved. Another step  220  comprises documenting the desired offset. Another step  222  comprises removing the head member from the femoral stem. Another step  224  comprises obtaining a femoral head implant that corresponds to the desired offset between the head member and the femoral stem. Another step  226  comprises implanting the femoral head implant. 
     Step  202  can be accomplished using any medical device considered suitable for a particular embodiment. Examples of medical devices considered suitable to complete step  202  include medical device  10 , medical device  110 , medical device  310 , medical device  510 , medical device  710 , variations of the medical devices described herein, and any other medical device considered suitable for a particular embodiment. 
     Step  204  can be accomplished by applying a force on a shaft directed toward a head member second recess until the shaft is disposed within the head member second recess. 
     Step  206  can be accomplished by applying a force on a locking member directed toward a head member third recess until the locking member is disposed within the head member third recess and the shaft is releasably attached to the head member. This can be accomplished, for example, by positioning a first projection and a second projection within a groove defined by the shaft or within a detent defined by the shaft. 
     Step  208  can be accomplished by applying a rotational force on the shaft (e.g., using a hex head driver) about a head member second lengthwise axis until the shaft is disposed in its first position, as shown in  FIGS.  23 ,  27 ,  60 , and  64   . Optionally, step  208  can be omitted in embodiments in which a shaft is pre-disposed in a first position. 
     Step  210  can be accomplished by applying a force on a spacer directed toward a femoral stem until the femoral stem is positioned within the spacer passageway and the second end of the femoral stem is disposed adjacent to, or planar with, the spacer second end, as shown in  FIGS.  27 ,  28 ,  29 ,  30 ,  31 ,  64 ,  65 ,  66 ,  67 ,  71 , and  72   . Optionally, step  210  can be omitted in embodiments in which a spacer is pre-assembled with a femoral stem. 
     Step  212  can be accomplished by applying a force on a head member directed toward a spacer until the spacer and a portion of the femoral stem is disposed within the head member first recess and the spacer and/or femoral stem contacts the shaft, as shown in  FIGS.  27  and  64   . Alternatively, step  212  can be completed prior to step  210  such that the spacer is disposed within the head member first recess. Optional steps can be accomplished subsequent to step  212  and prior to step  210  to complete an initial trial. For example, an optional step that can be completed subsequent to step  212  comprises positioning the head member adjacent an acetabular component. Another optional step comprises determining whether the initial offset between the head member and the femur is desired. Another optional step comprises moving the shaft such that the spacer translates relative to the head member. Another step comprises determining whether a desired offset between the head member and the femur has been achieved. Another optional step comprises documenting the desired offset. Another optional step comprises removing the head member from adjacent to the acetabular component. Subsequently, step  210  and the remainder of method  200  can be completed to accomplish a final trial and the implantation of a femoral head implant. 
     In embodiments in which the medical device utilized in the method  200  is pre-assembled, step  204 , step  206 , step  208 , and/or step  212  can be omitted from method  200 . 
     Step  214  can be accomplished by reviewing the position of the head member relative to the femoral stem and determining whether a desired offset between the head member and the femoral stem has been achieved. If it is determined that a desired offset between a head member and a femoral stem has been achieved when the shaft is in the first position, step  216  and step  218  can be omitted from method  200 . 
     If it is determined that a desired offset between a head member and a femoral stem has not been achieved when the shaft is in the first position, step  216  can be accomplished by applying a rotational force on the shaft (e.g., using a hex head driver) about a head member second lengthwise axis until the shaft is disposed in its second position, as shown in  FIGS.  24 ,  28 ,  61 , and  65   , and the spacer has translated relative to the head member. Movement of the shaft is accomplished in situ and allows for the hip arthroplasty trial to be completed without having to displace the hip during the trial procedure. 
     Step  218  can be accomplished as described with respect to step  214 . If it is determined that a desired offset between a head member and a femoral stem has been achieved when the shaft is in the second position, the method continues to step  220 . If it is determined that a desired offset between a head member and a femoral stem has not been achieved when the shaft is in the second position, step  216  is repeated such that the shaft is disposed in its third position, as shown in  FIGS.  25 ,  29 ,  62 , and  66   , and the spacer has translated relative to the head member and then step  218  is repeated. If it is determined that a desired offset between a head member and a femoral stem has been achieved when the shaft is in the third position, the method continues to step  220 . If it is determined that a desired offset between a head member and a femoral stem has not been achieved when the shaft is in the third position, step  216  is repeated such that the shaft is disposed in its fourth position, as shown in  FIGS.  26   ,  30 ,  63 , and  67 , and the spacer has translated relative to the head member and then step  218  is repeated. If it is determined that a desired offset between a head member and a femoral stem has been achieved when the shaft is in the fourth position, the method continues to step  220 . 
     Step  220  can be accomplished by using any suitable technique for documenting a desired offset between the medical device and the femoral stem once the desired offset has been achieved. 
     Step  222  can be accomplished by applying a force on a head member directed away from a femoral stem until the head member and spacer are removed from the femoral stem. In methods in which the head member is removed from the femoral stem but the spacer remains disposed on the femoral stem, an optional step comprises removing the spacer from the femoral stem and can be accomplished by applying a force on the spacer directed away from a femoral stem until the spacer is removed from the femoral stem. Alternatively, a spacer can remain on a femoral stem and be utilized with a femoral head implant. 
     Step  224  can be accomplished using any femoral head implant considered suitable for a particular embodiment. 
     Step  226  can be accomplished using any suitable technique or method of implanting a femoral head implant within a body of a patient. For example, step  226  can be accomplished by applying a force on a head member implant directed toward a femoral stem until the femoral stem is disposed within a recess defined by the head member implant. 
       FIGS.  78  through  100    illustrate a third example hip arthroplasty trial system  300  that includes a medical device  310  and a femoral stem  320 . The hip arthroplasty trial system  300  is similar to the hip arthroplasty trial system  1  illustrated in  FIGS.  2  through  38    and described above, except as detailed below. 
     As shown in  FIGS.  80  and  81   , the head member  312  has a head member first end  324 , a head member second end  326 , a head member first lengthwise axis  325 , a head member second lengthwise axis  327 , and a head member main body  328  that defines a head member articulating surface  330  and a head member first recess  332 . The head member first lengthwise axis  325  extends through the head member first recess  332  and through the head member second end  326 . The head member second lengthwise axis  327  extends through the head member  312  and intersects the head member first lengthwise axis  327  at an angle  329  (e.g., 90 degrees). The head member first recess  332  extends into the head member main body  328  along the head member first lengthwise axis  325  and from the head member first end  324  toward the head member second end  326 . As illustrated in  FIG.  81   , the entire head member first recess  332  has a constant inside diameter  333  that extends from the head member first end  324  toward the head member second end  326 . 
     In the illustrated embodiment, the head member first end  324  is disposed a first distance from a femoral stem second end  394  when the head member  312  is in the head member first position, as shown in  FIGS.  93  and  94   . The head member first end  324  is disposed a second distance from the femoral stem second end  394  when the head member  312  is in the head member second position, as shown in  FIGS.  95  and  96   . The head member first end  324  is disposed a third distance from the femoral stem second end  394  when the head member  312  is in the head member third position, as shown in  FIGS.  97  and  98   . The head member first end  324  is disposed a fourth distance from the femoral stem second end  394  when the head member  312  is in the head member fourth position, as shown in  FIGS.  99  and  100   . The first distance is greater than the second distance. The second distance is greater than the third distance. The third distance is greater than the fourth distance. 
     As shown in  FIGS.  91  through  98   , the spacer  314  is disposed within the head member first recess  332  and is moveable between a spacer first position, a spacer second position, a spacer third position, and a spacer fourth position. As shown in  FIGS.  82  and  83   , the spacer  314  has a spacer first end  350 , a spacer second end  352 , a spacer lengthwise axis  351 , a spacer length  353  that extends from the spacer first end  350  to the spacer second end  352 , and a spacer main body  354  that defines a spacer recess  356 , a spacer recess base  358 , and a peg  360 . The spacer recess  356  extends from the spacer first end  350  to the spacer recess base  358  and has a spacer recess length  359 . The peg  360  extends from the spacer recess base  358  beyond the spacer first end  350  along the spacer lengthwise axis  351 , has a peg length  361  and a peg diameter  363 , and is adapted to be received by the femoral stem fourth passageway  406 , as described in more detail below. The peg length  361  is greater than the spacer length  353  and the spacer length  353  is greater than the spacer recess length  359 . The peg diameter  363  is constant between the spacer recess base  358  and a spacer leading end  362 . However, a peg diameter could vary along its length in alternative embodiments. 
     As shown in  FIGS.  84  and  85  and  91  through  98   , in the illustrated embodiment, the shaft  316  is a cam  368  that is rotatable within the femoral stem first, second, and third passageways  400 ,  402 ,  404 , as described in more detail below. The cam  368  has a cam first boss  370 , a cam projection  372  attached to the cam first boss  370 , a cam second boss  374  attached to the cam projection  372 , and a cam main body  376  that defines a cam recess  382 , a cam indicator  384 , and a cam projection first end  388 . The cam projection  372  is disposed between the cam first boss  370  and the cam second boss  374  and contacts the second end  392  of the femoral step  320  as shown in  FIGS.  91  through  98   . The cam recess  382  extends into the cam first boss  370  and has a hexagonal cross-sectional configuration. The cam indicator  384  is disposed on the cam first boss  370  and has a lengthwise axis  385  that orthogonally intersects a plane  387  that contains the cam projection first end  388 . The cam indicator  384  provides a mechanism for illustrating to a user of the hip arthroplasty hip trial  300  that the position of the cam projection first end  388  is relative to the spacer  314 . 
     The cam  368  is moveable between a cam first position, as shown in  FIGS.  93  and  94   , a cam second position, as shown in  FIGS.  95  and  96   , a cam third position, as shown in  FIGS.  97  and  98   , and a cam fourth position, as shown in  FIGS.  99  and  100   . Movement of the cam  368  from its cam first position to its cam second position moves the spacer  314  from its spacer first position to its spacer second position, as shown in  FIGS.  93  through  96   . Movement of the cam  368  from its cam second position to its cam third position moves the spacer  314  from its spacer second position to its spacer third position, as shown in  FIGS.  95  through  98   . Movement of the cam  368  from its cam third position to its cam fourth position moves the spacer  314  from its spacer third position to its spacer fourth position, as shown in  FIGS.  97  through  100   . 
     In the illustrated embodiment, the femoral stem  320  has a femoral stem first end  390 , a femoral stem second end  392 , a femoral stem first lengthwise axis  391 , a femoral stem second lengthwise axis  393 , a femoral stem main body  394  that includes a femoral stem first portion  396 , a femoral stem second portion  398 , a femoral stem first passageway  400 , a femoral stem second passageway  402 , a femoral stem third passageway  404 , and a femoral stem fourth passageway  406 . As best illustrated in  FIG.  86   , the femoral stem first lengthwise axis  391  extends from the femoral stem first end  390  toward a curve defined by the femoral stem  320  and the femoral stem second lengthwise axis  393  extends from the femoral stem second end  392  toward the curve defined by the femoral stem  320 . The femoral stem first portion  396  extends from the femoral stem first end  390  toward the curve defined by the femoral stem  320  along the femoral stem first lengthwise axis  391 . The femoral stem second portion  398  extends from the femoral stem second end  392  toward the curve defined by the femoral stem  320  along the femoral stem second lengthwise axis  393 . Each of the first, second, third, and fourth passageways  400 ,  402 ,  404 ,  406  is defined on the femoral stem second portion  398 . 
     Each of the femoral stem first, second, third, and fourth passageways is best illustrated in  FIGS.  86  through  90   . The femoral stem first and second passageways  400 ,  402  are coaxial with each other and extend into the femoral stem main body  394  along an axis that is perpendicular to the femoral stem second lengthwise axis  393 . The femoral stem first passageway  400  has a femoral stem first diameter  401  that is constant and the femoral stem second passageway  402  has a femoral stem second diameter  403  that is constant. As best illustrated in  FIGS.  91  and  92   , each of the femoral stem first and second diameters  401 ,  403  is sized and configured to receive a portion of the shaft  314  such that the femoral stem first passageway  400  is adapted to receive the cam first boss  370  and the femoral stem second passageway  402  is adapted to receive the cam second boss  374 . The femoral stem first and second passageways  400 ,  402  provide a mechanism to allow the shaft  314  to rotate within the femoral stem  320  in order to change the position of the spacer  314  and head member  312 . 
     Each of the femoral stem first and second passageways  400 ,  402  can have any suitable size, shape, and configuration, and selection of a suitable size, shape and configuration for a femoral stem passageway can be based on various considerations, include the size of the shaft intended to be disposed within the passageway. In the illustrated embodiment, each of the femoral stem first and second passageways has a circular cross-sectional shape. Furthermore, each of the femoral stem first and second passageways  400 ,  402  can be positioned along the femoral stem second portion  396  at any angle relative to the femoral stem second lengthwise axis  393 . Examples of angles considered suitable to position a femoral stem passageways relative to a femoral stem lengthwise axis include angles equal to, greater than, less than, or about 45 degrees, 90 degrees, 135 degrees, angles between about 10 degrees and about 170 degrees, angles between about 45 degrees and about 135 degrees, and any other angle considered suitable for a particular embodiment. 
     The femoral stem third passageway  404  extends through the femoral stem main body  394 , through the femoral stem second lengthwise axis  393 , and is in communication with each of the femoral stem first and second passageways  400 ,  402 . As illustrated in  FIG.  88   , the femoral stem third passageway  404  has a femoral stem third passageway length  405  that extends along the femoral stem second lengthwise axis  393  between the femoral stem second end  392  and the curve defined by the femoral stem  320 . The femoral stem third passageway  404  is adapted to receive a portion of the shaft  314  (e.g., the cam projection  372 ) and is sized and configured such that the shaft  314  (e.g., cam projection  372 ) can rotate within the femoral stem third passageway  404  during use. As best illustrated in  FIGS.  89  and  90   , the femoral stem fourth passageway  406  extends from the femoral stem second end  392  to the femoral stem third passageway  404  along the femoral stem second lengthwise axis  393  and has a femoral stem fourth passageway length  409 . The femoral stem fourth passageway  406  is in communication with the femoral stem third passageway  404  and has a femoral stem fourth passageway diameter  408  that is sized and configured to receive the peg  360  such that the peg  360  can be moved within the femoral stem fourth passageway  406  shown in  FIGS.  93  through  100   . The communication between the femoral stem third and fourth passageways  404 ,  406  provides a mechanism for the cam projection  372  to contact the peg  360  such that when the cam  368  is moved from a first cam position to a second cam position, the spacer  314  moves from a first spacer position to a second spacer position to adjust the head member  312  to a desired length relative to the femoral stem  320 . 
       FIGS.  93  and  94    illustrate the hip arthroplasty trial system  300  in a first position in which each of the head member  312 , the spacer  314 , and the shaft  316  is in a first position. Additionally, a first portion of the peg first length  364  is disposed in the femoral stem third and fourth passageways  404 ,  406 . In the hip arthroplasty trial system first position, each of the head member  312  and the spacer  314  is disposed a first distance  335  from the end of the femoral head third passageway  404 . 
       FIGS.  95  and  96    illustrate the hip arthroplasty trial system  300  in a second position. Movement from the first position to the second position can be accomplished by a user, such as a surgeon, exerting a force on the shaft  316  (e.g., by placing a tool inside of the cam recess  382 ) and rotating the shaft  316  90 degrees clockwise about an axis that is perpendicular to the femoral stem second lengthwise axis  393 . As best illustrated in  FIG.  96   , the rotation of the shaft  316  from the shaft first position to the shaft second position causes the cam projection  372  to interface with the peg  360  such that the spacer  314  moves from a spacer first position to a spacer second position. Once the spacer  314  is positioned in a spacer second position, a second portion of the peg length  365  is disposed in the femoral stem third and fourth passageways  404 ,  406 . The second portion of the peg length  365  is less than the first portion of the peg length  364 . In the hip arthroplasty trial system second position, each of the head member  312  and the spacer  314  is disposed a second distance  337  from the end of the femoral head third passageway  404  to the femoral stem  320  which is less than the first distance  335 . 
       FIGS.  97  and  98    illustrate the hip arthroplasty trial system  300  in a third position. Movement from the second position to the third position can be accomplished by a user, such as a surgeon, exerting a force on the shaft  316  (e.g., by placing a tool inside of the cam recess  382 ) and rotating the shaft  316  90 degrees clockwise about an axis that is perpendicular to the femoral stem second lengthwise axis  393 . As best illustrated in  FIG.  98   , the rotation of the shaft  316  from the shaft second position to the shaft third position causes the cam projection  372  to interface with the peg  360  such that the spacer  314  moves from a spacer second position to a spacer third position. Once the spacer  314  is positioned in a spacer third position, a third portion of the peg length  366  is disposed in the femoral stem third and fourth passageways  404 ,  406 . The third portion of the peg length  366  is less than the second portion of the peg length  364 . In the hip arthroplasty trial system third position, each of the head member  312  and the spacer  314  is disposed a third distance  339  from the end of the femoral head third passageway  404 , which is greater than the second distance  337 . 
       FIGS.  99  and  100    illustrate the hip arthroplasty trial system  300  in a fourth position. Movement from the third position to the fourth position can be accomplished by a user, such as a surgeon, exerting a force on the shaft  316  (e.g., by placing a tool inside of the cam recess  382 ) and rotating the shaft  316  90 degrees clockwise about an axis that is perpendicular to the femoral stem second lengthwise axis  393 . As best illustrated in  FIG.  100   , the rotation of the shaft  316  from the shaft third position to the shaft fourth position causes the cam projection  372  to interface with the peg  360  such that the spacer  314  moves from a spacer third position to a spacer fourth position. Once the spacer  314  is positioned in a spacer fourth position, a fourth portion of the peg length  367  is disposed in the femoral stem fourth passageway  406 . The fourth portion of the peg length  367  is less than the third portion of the peg length  364 . In the hip arthroplasty trial system fourth position, each of the head member  312  and the spacer  314  is disposed a fourth distance  341  from the end of the femoral head third passageway  404 , which is greater than the third distance  339 . 
       FIGS.  101  through  115    illustrate a fourth example hip arthroplasty trial system  500  that includes a medical device  510  and a femoral stem  520 . The hip arthroplasty trial system  500  is similar to the hip arthroplasty trial system  310  illustrated in  FIGS.  78  through  100    and described above, except as detailed below. 
     As shown in  FIGS.  103  through  105   , the femoral stem  520  has a femoral stem first end  590 , a femoral stem second end  592 , a femoral stem first lengthwise axis  591 , a femoral stem second lengthwise axis  593 , a femoral stem main body  594  that includes a femoral stem first portion  596 , a femoral stem second portion  598 , a femoral stem first passageway  600 , a femoral stem second passageway  602 , a femoral stem third passageway  604 , and a femoral stem fourth passageway  606 . In the illustrated embodiment, each of the first, second, third, and fourth passageways  600 ,  602 ,  604 ,  606  is defined on the femoral stem second portion  596 . In the illustrated embodiment, the femoral stem first, second, and third passageways  600 ,  602 ,  604  have been positioned at a location that is offset 90 degrees relative to the position illustrated in hip arthroplasty trial system  300 . 
       FIGS.  108  and  109    illustrate the hip arthroplasty trial system  500  in a first position in which each of the head member  512 , the spacer  514 , and the shaft  516  is in a first position. Additionally, a first portion of the peg length  564  is disposed in the femoral stem third and fourth passageways  604 ,  606 . In the hip arthroplasty trial system first position, each of the head member  512  and the spacer  514  is disposed a first distance  535  from the end of the femoral stem third passageway  604 . 
       FIGS.  110  and  111    illustrate the hip arthroplasty trial system  500  in a second position. Movement from the first position to the second position can be accomplished by a user, such as a surgeon, exerting a force on the shaft  516  (e.g., by placing a tool inside of the cam recess  582 ) and rotating the shaft  516  90 degrees clockwise about an axis that is perpendicular to the femoral stem second lengthwise axis  593 . As best illustrated in  FIG.  111   , the rotation of the shaft  516  from the shaft first position to the shaft second position causes the cam projection  572  to interface with the peg  560  such that the spacer  514  moves from a spacer first position to a spacer second position. Once the spacer  514  is positioned in a spacer second position, a second portion of the peg length  565  is disposed in the femoral stem third and fourth passageways  604 ,  606 . The second portion of the peg length  565  is less than the first portion of the peg length  564 . In the hip arthroplasty trial system second position, each of the head member  512  and the spacer  514  is disposed a second distance  537  from the end of the femoral head third passageway  604 , which is greater than the first distance  535 . 
       FIGS.  112  and  113    illustrate the hip arthroplasty trial system  500  in a third position. Movement from the second position to the third position can be accomplished by a user, such as a surgeon, exerting a force on the shaft  516  (e.g., by placing a tool inside of the cam recess  582 ) and rotating the shaft  516  90 degrees clockwise about an axis that is perpendicular to the femoral stem second lengthwise axis  593 . As best illustrated in  FIG.  113   , the rotation of the shaft  516  from the shaft second position to the shaft third position causes the cam projection  572  to interface with the peg  560  such that the spacer  514  moves from a spacer second position to a spacer third position. Once the spacer  514  is positioned in a spacer third position, a third portion of the peg length  566  is disposed in the femoral stem third and fourth passageways  604 ,  606 . The third portion of the peg length  566  is less than the second portion of the peg length  565 . In the hip arthroplasty trial system third position, each of the head member  512  and the spacer  514  is disposed a third distance  539  from the end of the femoral head third passageway  604 , which is greater than the second distance  537 . 
       FIGS.  114  and  115    illustrates the hip arthroplasty trial system  500  in a fourth position. Movement from the third position to the fourth position can be accomplished by a user, such as a surgeon, exerting a force on the shaft  516  (e.g., by placing a tool inside of the cam recess  582 ) and rotating the shaft  516  90 degrees clockwise about an axis that is perpendicular to the femoral stem second lengthwise axis  593 . As best illustrated in  FIG.  115   , the rotation of the shaft  516  from the shaft third position to the shaft fourth position causes the cam projection  572  to interface with the peg  560  such that the spacer  514  moves from a spacer third position to a spacer fourth position. Once the spacer  514  is positioned in a spacer fourth position, a fourth portion of the peg length  567  is disposed in the femoral stem fourth passageway  606 . The fourth portion of the peg length  567  is less than the third portion of the peg length  566 . In the hip arthroplasty trial system fourth position, each of the head member  512  and the spacer  514  is disposed a fourth distance  541  from the end of the femoral head third passageway  604 , which is greater than the third distance  539 . 
       FIGS.  116 ,  117 , and  119  through  128    illustrate a fifth example hip arthroplasty trial system  700  that includes a medical device  710  and a femoral stem  720 . The hip arthroplasty trial system  700  is similar to the hip arthroplasty trial system  310  illustrated in  FIGS.  78  through  100    and described above, except as detailed below. 
     In the illustrated embodiment, the head member  712  has a head member first end  724 , a head member second end  726 , a head member first lengthwise axis  725 , a head member second lengthwise axis  727 , and a head member main body  728  that defines a head member articulating surface  730  and a head member recess  732 . The head member first lengthwise axis  725  extends through the head member recess  732  and the head member second end  726 . The head member recess  732  extends into the head member main body  728  along the head member first lengthwise axis  725  from the head member first end  724  toward the head member second end  726  and has a head member first recess length  731 . The head member recess  732  has a constant inside diameter  733  that extends from the head member first end  724  toward the head member second end  726 . As illustrated in  FIGS.  119  and  120   , the head member  712  and the spacer  314  are a single, unitary component such that the head member main body  728  defines a peg  760  that is disposed within the head member recess  732 . The peg  760  extends from a head member recess base  734  beyond the head member first end  724  along the head member first lengthwise axis  725  and has a peg length  761  and a peg diameter  763 . While hip arthroplasty trial system  700  has been illustrated as including a medical device  710  and a femoral stem  720 , a hip arthroplasty trial system can include a femoral stem that has any suitable structural arrangement. For example,  FIG.  118    illustrates an alternative hip arthroplasty trial system  700 ′ that is similar to the hip arthroplasty trial system  700 , but includes a femoral stem  720 ′ that has a structural arrangement that is different than femoral stem  720 . 
       FIGS.  121  and  122    illustrates the hip arthroplasty trial system  700  in a first position in which each of the head member  712  and shaft  716  is in a first position. Additionally, a first portion of the peg length  764  is disposed in the femoral stem third and fourth passageways  804 ,  806 . In the hip arthroplasty trial system first position, the head member  712  is disposed a first distance  735  from the end of the femoral stem third passageway  804 . 
       FIGS.  123  and  124    illustrates the hip arthroplasty trial system  700  in a second position. Movement from the first position to the second position can be accomplished by a user, such as a surgeon, exerting a force on the shaft  716  (e.g., by placing a tool inside of the cam recess  782 ) and rotating the shaft  716  90 degrees clockwise about an axis that is perpendicular to the femoral stem second lengthwise axis  793 . As best illustrated in  FIG.  124   , the rotation of the shaft  716  from the shaft first position to the shaft second position causes the cam projection  772  to interface with the peg  760  such that the head member  712  moves from a head member first position to a head member second position. Once the head member  714  is positioned in a head member second position, a second portion of the peg length  765  is disposed in the femoral stem third and fourth passageways  804 ,  806 . The second portion of the peg length  765  is less than the first portion of the peg length  764 . In the hip arthroplasty trial system second position, the head member  512  is disposed a second distance  737  from the end of the femoral head third passageway  804 , which is less than the first distance  735 . 
       FIGS.  125  and  126    illustrates the hip arthroplasty trial system  700  in a third position. Movement from the second position to the third position can be accomplished by a user, such as a surgeon, exerting a force on the shaft  716  (e.g., by placing a tool inside of the cam recess  782 ) and rotating the shaft  716  90 degrees clockwise about an axis that is perpendicular to the femoral stem second lengthwise axis  793 . As best illustrated in  FIG.  126   , the rotation of the shaft  716  from the shaft second position to the shaft third position causes the cam projection  772  to interface with the peg  760  such that the head member  712  moves from a head member second position to a head member third position. Once the head member  712  is positioned in a head member third position, a third portion of the peg length  766  is disposed in the femoral stem third and fourth passageways  804 ,  806 . The third portion of the peg length  766  is less than the second portion of the peg length  765 . In the hip arthroplasty trial system third position, the head member  512  is disposed a third distance  739  from the end of the femoral head third passageway  804 , which is greater than the second distance  737 . 
       FIGS.  127  and  128    illustrates the hip arthroplasty trial system  700  in a fourth position. Movement from the third position to the fourth position can be accomplished by a user, such as a surgeon, exerting a force on the shaft  716  (e.g., by placing a tool inside of the cam recess  782 ) and rotating the shaft  716  90 degrees clockwise about an axis that is perpendicular to the femoral stem second lengthwise axis  793 . As best illustrated in  FIG.  127   , the rotation of the shaft  716  from the shaft third position to the shaft fourth position causes the cam projection  772  to interface with the peg  760  such that the head member  712  moves from a head member third position to a head member fourth position. Once the head member  712  is positioned in a head member fourth position, a fourth portion of the peg length  767  is disposed in the femoral stem fourth passageway  806 . The fourth portion of the peg length  767  is less than the third portion of the peg length  766 . In the hip arthroplasty trial system fourth position, the head member  712  is disposed a fourth distance  741  from the end of the femoral head third passageway  804 , which is greater than the third distance. 
       FIG.  129    is a schematic illustration of an exemplary method  900  of completing a hip arthroplasty trial on a femur. 
     A step  902  comprises obtaining a medical device for use in a hip arthroplasty trial. The medical device comprises a head member, a shaft, and a locking member. Another step  904  comprises implanting a femoral stem into a femur of a patient. Another step  906  comprises positioning the head member on the femoral stem. Another step  908  comprises moving the shaft in situ in a first direction such that the shaft moves to the second position and the head member moves away from the femoral stem. Another step  910  comprising moving the shaft in situ in a second direction such that the shaft moves to the first position and the head member moves toward the femoral stem. Another  912  comprises obtaining a femoral head implant that corresponds to the desired offset between the head member and the femoral stem. Another step  914  comprises removing head member from the femoral stem. Another step  916  comprises positioning a femoral head implant on the femoral stem. 
     Step  902  can be accomplished using any medical device considered suitable for a particular embodiment. Examples of medical devices considered suitable to complete step  902  include medical device  10 , medical device  110 , medical device  310 , medical device  510 , medical device  710 , variations of the medical devices described herein, and any other medical device considered suitable for a particular embodiment. Alternatively, step  902  can comprise obtaining a hip arthroplasty trial system for use in a hip arthroplasty trial. The hip arthroplasty trial system comprises a medical device and a femoral stem. In this alternative embodiment, step  904  comprises implanting the femoral stem into a femur of a patient. 
     Step  904  can be accomplished using any suitable technique or method of implanting a femoral stem within a patient&#39;s body and by applying a force on the femoral stem directed toward the patient&#39;s femur such that the femoral stem is advanced into a bore defined in the patient&#39;s femur. Examples of femoral stems considered suitable to complete step  904  include femoral stem  20 , femoral stem  120 , femoral stem  320 , femoral stem  520 , femoral stem  720 , variations of the femoral stem described herein, and any other femoral stem considered suitable for a particular embodiment. 
     Step  906  can be accomplished by applying a force on a head member directed toward the femoral stem second end until the head member is disposed on the femoral stem second end. Examples of head members that can be used to accomplish step  906  include head member  12 , head member  112 , head member  312 , head member  512 , head member  712 , variations of the head members described herein, and any other head members considered suitable for a particular embodiment. Optionally, a spacer can be positioned within the head member or on the femoral stem prior to step  906 , as described herein. Optional steps can be accomplished prior to step  904  and step  906  to complete an initial trial. For example, an optional step that can be completed prior to step  904  and step  906  comprises positioning the head member adjacent an acetabular component. Another optional step comprises determining whether the initial offset between the head member and the femur is desired. Another optional step comprises moving the shaft such that the spacer translates relative to the head member. Another step comprises determining whether a desired offset between the head member and the femur has been achieved. Another optional step comprises documenting the desired offset. Another optional step comprises removing the head member from adjacent to the acetabular component. Subsequently, step  904  and step  906  and the remainder of method  900  can be completed to accomplish a final trial and the implantation of a femoral head implant. 
     Step  908  can be accomplished by applying a rotational force on the shaft (e.g., using a hex head driver) until each of the shaft and the head member moves from a first position to a second position. Step  908  can be omitted from method  900  if it is determined that a desired offset between a head member and a femoral stem has been achieved prior to step  908  being completed. If after the completion of step  908  it is determined that a desired offset between a head member and a femoral stem has been achieved when the shaft is in the second position, the method continues to step  910 . If it is determined that a desired offset between a head member and a femoral stem has not been achieved when the shaft is in the second position, step  908  is repeated such that the shaft is disposed in its third position. If it is determined that a desired offset between a head member and a femoral stem has been achieved when the shaft is in the third position, the method continues to step  910 . If it is determined that a desired offset between a head member and a femoral stem has not been achieved when the shaft is in the third position, step  908  is repeated such that the shaft is disposed in its fourth position. If it is determined that a desired offset between a head member and a femoral stem has been achieved when the shaft is in the fourth position, the method continues to step  910 . 
     Step  910  can be accomplished by applying a rotational force on the shaft (e.g., using a hex head driver) until each of the shaft and the head member moves from a second position to a first position. Step  910  can be omitted from method  900  if it is determined that a desired offset between a head member and a femoral stem has been achieved prior to step  908  being completed. Optionally, step  910  can be repeated multiple times until each of the shaft and the head member is in a first position. 
     Step  912  can be accomplished by using any femoral head implant considered suitable for a particular embodiment. For example, step  912  can be accomplished by selecting a femoral head implant that correlates with the desired offset between a head member and a femoral stem. 
     Step  914  can be accomplished by applying a force on a head member directed away from a femoral stem until the head member is removed from the femoral stem. In methods where the head member is removed from the femoral stem but a spacer remains disposed on the femoral stem, an optional step comprises removing the spacer from the femoral stem and can be accomplished by applying a force on the spacer directed away from a femoral stem until the spacer is removed from the femoral stem. 
     Step  916  can be accomplished by using any suitable technique or method of implanting a femoral head implant within a body of a patient. For example, step  916  can be accomplished by applying a force on the femoral head implant directed toward the femoral stem second end until the femoral head implant is disposed on the femoral stem second end. 
       FIG.  130    is a schematic illustration of an exemplary method  1000  of completing a hip arthroplasty trial on a femur. 
     A step  1002  comprises obtaining a medical device for use in a hip arthroplasty trial. Another step  1004  comprises implanting a femoral stem first portion into a femur. Another step  1006  positioning a spacer within a head member. Another step  1008  comprises positioning the head member and the spacer on a femoral stem second portion. Another step  1010  comprises moving a shaft in situ in a first direction such that the spacer and head member moves in a first direction. Another step  1012  comprises determining whether a desired offset between the head member and the femoral stem has been achieved. Another step  1014  comprises documenting the desired offset. Another step  1016  comprises moving the shaft in situ in a second direction such that spacer and the head member moves in a second direction. Another step  1018  comprises obtaining a femoral head implant that corresponds to the desired offset between the head member and the femoral stem. Another step  2020  comprises removing the head member and spacer from the femoral stem. Another step  1022  comprises positioning the femoral head implant on the femoral stem second portion. 
     Step  1002  can be accomplished as described herein with respect to step  202  and step  902 . 
     Step  1004  can be accomplished as described with respect to step  904 . 
     Step  1006  can be accomplished as described with respect to step  212 . Optionally, step  1006  can be omitted if a head member and a spacer are pre-assembled in a medical device, Optionally, step  1006  can be omitted if a user utilizes medical device  710 . 
     Step  1008  can be accomplished as described with respect to step  906 , step  210 , and step  212 . 
     Step  1010  can be accomplished as described with respect to step  908 . 
     Step  1012  can be accomplished by reviewing the position of the head member relative to the femoral stem and determining whether a desired offset between the head member and the femoral stem has been achieved. If it is determined that a desired offset between a head member and a femoral stem has been achieved when the shaft is in the first position, the method continues to step  1014 . If it is determined that a desired offset between a head member and a femoral stem has not been achieved when the shaft is in the first position, step  1010  is repeated. 
     Step  1014  can be accomplished by using any suitable technique for documenting a desired offset between the medical device and the femoral stem. 
     Step  1016  can be accomplished as described with respect to step  910 . 
     Step  1018  can be accomplished as described with respect to step  912 . 
     Step  1020  can be accomplished as described with respect to step  222  and step  914 . 
     Step  1022  can be accomplished as described with respect to step  916 . 
       FIG.  131    illustrates an example kit  1100  that includes a first head member  1112  according to an embodiment; a second head member  1212  according to an embodiment; a third head member  1312  according to an embodiment; a first spacer  1114  according to an embodiment; a second spacer  1214  according to an embodiment; a first shaft  1116  according to an embodiment; a second shaft  1216  according to an embodiment; a locking member  1118  according to an embodiment; an o-ring  1191  according to an embodiment; a first femoral stem  1120  according to an embodiment; a second femoral stem  1220  according to an embodiment; and a third femoral stem  1320  according to an embodiment. While not illustrated, a kit can optionally include instructions for use. 
     Any suitable head member, spacer, shaft, locking member, o-ring, and femoral stem can be included in a kit and selection of a suitable head member, spacer, shaft, locking member, o-ring, and femoral stem to include in a kit can be based on various considerations, including the desired offset intended to be achieved during a trial procedure. Examples of head members considered suitable to include in a kit include head member  12 , head member  112 , head member  312 , head member  512 , head member  712 , head member  712 ′, variations of the head member described herein, and any other head member according to an embodiment. Examples of spacers considered suitable to include in a kit include spacer  14 , spacer  114 , spacer  314 , spacer  514 , variations of the spacer described herein, and any other spacer according to an embodiment. Examples of shafts considered suitable to include in a kit include shaft  16 , shaft  116 , shaft  316 , shaft  516 , shaft  716 , shaft  716 ′, variations of the shaft described herein, and any other shaft according to an embodiment. Examples of locking members considered suitable to include in a kit include locking member  18 , locking member  118 , variations of the locking member herein, and any other locking member according to an embodiment. Examples of o-rings considered suitable to include in a kit include o-ring  191 , variations of the o-rings described herein, and any other o-ring according to an embodiment. Examples of femoral stems considered suitable to include in a kit include femoral stem  20 , femoral stem  120 , femoral stem  320 , femoral stem  520 , femoral stem  720 , femoral stem  720 ′, variations of the femoral stem described herein, and any other femoral stem according to an embodiment. In the illustrated embodiment, the kit  1100  includes head member  12 , as shown in  FIG.  2   , head member  312 , as shown in  FIG.  78   , head member  712 , as shown in  FIG.  119   , spacer  114 , as shown in  FIG.  51   , spacer  314 , as shown in  FIG.  82   , shaft  116 , as shown in  FIG.  55   , shaft  716 , as shown in  FIG.  84   , locking member  118 , as shown in  FIG.  57   , o-ring  191 , as shown in  FIG.  53   , femoral stem  20 , as shown in  FIG.  2   , femoral stem  320 , as shown in  FIG.  78   , and femoral stem  520 , as shown in  FIG.  101   . 
     While the kit  1100  has been illustrated as including head members  1112 ,  1212 ,  1312 , spacers  1114 ,  1214 , shafts  1116 ,  1216 , locking member  1118 , an o-ring  1191 , and femoral stems  1120 ,  1220 ,  1320 , any suitable number, and type, of head members, spacers, shafts, locking members, o-rings, and/or femoral stems can be included in a kit, such as those described herein. Selection of a suitable number of head members, spacers, shafts, locking members, o-rings, and/or femoral stems to include in a kit according to a particular embodiment can be based on various considerations, such as the procedure intended to be completed using the components included in the kit. Examples of suitable numbers of head members, spacers, shafts, locking members, O-rings, and/or femoral stems to include in a kit include one, at least one, two, a plurality, three, four, and any other number considered suitable for a particular embodiment. 
     While the kit  1100  has been illustrated an including only head members  1112 ,  1212 ,  1312 , spacers  1114 ,  1214 , shafts  1116 ,  1216 , locking member  1118 , O-ring  1191 , and femoral stems  1120 ,  1220 ,  1320 , a kit can include any suitable number of optional components. Examples of numbers of optional components considered suitable to include in a kit, such as a head member implant, include one, at least one, two, a plurality, three, four, five, more than five, and any other number considered suitable for a particular embodiment. Examples of optional components and/or devices considered suitable to include in a kit include containers, boring devices, hex head drivers, head member implants of various sizes, and/or any other component and/or device considered suitable for a particular embodiment. 
     While the hip arthroplasty trials systems, medical devices, methods, and kits described herein have been described with respect to use in a hip arthroplasty trial, the hip arthroplasty trial systems, medical devices, methods, and/or kits described herein can be utilized in any suitable procedure and selection of a suitable procedure to utilize a hip arthroplasty trial system, a medical device, a method, or a kit described herein can be based on various considerations, including the treatment intended to be performed. 
     Furthermore, the hip arthroplasty trial systems, medical devices, methods, and kits described herein are considered advantageous at least because they provide a mechanism for performing a femoral head trial in situ (e.g., adjusting head length in situ). This reduces the impact on surrounding tissue, the time required to complete the procedure, and the overall complexity of the procedure. This is contrary to current practice, as shown in  FIGS.  1  and  1 A , in which multiple modular femoral necks, or head length options, must be trialed to determine the desired offset between a head and a femoral stem. Current practice requires multiple assemblies and disassembles of the components, and multiple dislocation and relocations of the hip, to determine the desired offset, which disrupts tissue, is time consuming, and complex. This is true of both initial trialing with trial components, as well as final trialing with an implanted femoral stem. 
     Those with ordinary skill in the art will appreciate that various modifications and alternatives for the described and illustrated embodiments can be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are intended to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.