Patent Publication Number: US-2023157832-A1

Title: Humeral Implant and Method

Description:
FIELD OF THE INVENTION 
     The present invention relates in general to humeral implants. 
     BACKGROUND OF THE INVENTION 
     Orthopaedic surgeons often perform joint replacement surgery on patients who suffer pain and physical limitations caused by joint surfaces which have degenerative, traumatic, or other pathologic damage. The success of replacement surgery is related to the degree of morbidity associated with the surgical technique and also to the ability of the surgery to restore the natural anatomy and biomechanics of the joint. The present inventor recognized the need for improved rates of surgical success through an improved implant and method. 
     BRIEF SUMMARY OF THE INVENTION 
     A new humeral implant is disclosed. The implant has a humeral surface component and a stem. The humeral surface component has an articular surface and is configured for fixation to an articular portion of a proximal humerus. The stem is configured for post-surgery axial movement within the humerus. The stem is connected to the humeral surface component opposite of the articular surface. 
     Accordingly, one aspect of the present invention is to provide a novel humeral implant for shoulder replacement surgery that can be implemented with conventional, minimally invasive, or novel surgical techniques. 
     Another aspect of the present invention is to provide a humeral implant which includes an articular surface component with anatomic geometry with different radii of curvature in the axial and coronal planes. 
     Another aspect of the present invention is to provide a humeral implant which includes a stem that resides along a central axis of the proximal humerus rather than in the intramedullary canal. 
     Another aspect of the present invention is to provide a humeral implant that partially resurfaces the humeral head. 
     Another aspect of the present invention is to provide a humeral implant which obtains durable fixation on the subchondral bone of an anatomic head. 
     Another aspect of the present invention is to provide a humeral implant which obtains durable fixation with the non-articular lateral humeral cortex. 
     Another aspect of the present invention is to provide a humeral implant which obtains slidable engagement with a tunnel along a central axis of the humerus. 
     Another aspect of the present invention is to provide a humeral implant which obtains slidable engagement with the non-articular lateral humeral cortex. 
     Another aspect of the present invention is to provide a humeral implant which preserves humeral bone stock and allows increased physiologic load transmission from the joint surface in a patient&#39;s shoulder along the bone of the proximal humerus. 
     Another aspect of the present invention is to provide a humeral implant which has an interchangeable articular component and allows conversion between an anatomic shoulder arthroplasty and a reverse shoulder arthroplasty. 
     Another aspect of the present invention is to provide a modular bone reamer-which can be used with traditional open and transhumeral minimally invasive techniques for shoulder arthroplasty. 
     Another aspect of the present invention is to provide a modular bone reamer which can be used to prepare a humerus and a glenoid process in a shoulder joint without transecting their rotator cuff tendon and without dislocating their shoulder joint. 
     Another aspect of the present invention is to provide a modular bone reamer which can be used to prepare a humerus and a glenoid process in a shoulder joint perpendicularly to the shaft of the reamer. 
     A method of implanting a humeral implant is disclosed, comprising: fixing an articular humeral component comprising an articular surface to a prepared articular portion of a proximal humerus, placing a stem in a tunnel in the proximal humerus without fixing the stem within the tunnel against post-surgery longitudinal movement; and, connecting the stem to the articular humeral component. 
     Other features and advantages of this invention will be apparent to orthopaedic surgeons and other persons who are skilled in the art of shoulder repair and reconstruction, particularly after reviewing the following detailed description of the invention and the embodiments thereof, from the claims, and from the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a perspective view of a portion of a humerus bone with a common arthritic deformity of the humeral head. 
         FIG.  1 B  is a perspective view of a portion of a scapula bone with a glenoid process. 
         FIG.  2 A  is a side, partially transparent, view of a humeral implant of the invention utilizing a stem as described herein in position on a prepared humerus bone. 
         FIG.  2 B  is a side section view of a traditional humeral implant positioned in a prepared humerus bone. 
         FIG.  2 C  is a side, partially transparent, view of another common humeral implant utilizing fins in a metaphyseal position of a prepared humerus bone. 
         FIG.  3 A  is a top view of the articular humeral component of the humeral implant of  FIG.  2 A  disclosing the implant&#39;s elliptical shape which incorporates varying radii of curvature. 
         FIG.  3 B  is a bottom view of the articular humeral component of the humeral implant of  FIG.  3 A  disclosing its bone ingrowth surface and disposition of a coupling device for engaging an associated stem for the implant. 
         FIG.  3 C  is a side view of a side of the articular humeral component of the humeral implant of  FIG.  3 A . 
         FIG.  3 D  is a side view of a first embodiment stem for the humeral implant of  FIG.  3 A  configured for fixed engagement of the implant with the humeral bone. 
         FIG.  3 E  is a side view of a second embodiment stem for the humeral implant of  FIG.  3 A  configured for slidable engagement in the humeral bone. 
         FIG.  4    is a bottom view of a second embodiment of the articular humeral component of a second embodiment humeral implant of the invention having an offset coupling device for a stem. 
         FIG.  5    is side, partially transparent, view a third embodiment of a new humeral implant of the invention having a partial articular component shown in position on a prepared humerus bone. 
         FIG.  6 A  is a side view of a humeral implant of  FIG.  3 A  with an associated lateral buttress plate secured to the bone with screws engaging the implant with a stem. 
         FIG.  6 B  is a second view of the humeral implant of  FIG.  6 A  with an associated lateral buttress plate secured to the bone with screws and/or screws engaging the implant and the lateral buttress plate. 
         FIG.  7    is a side perspective view of a fourth embodiment humeral implant with a concave articular portion for reverse shoulder arthroplasty. 
         FIG.  8    is a side perspective view the humeral implant of  FIG.  7    with a convex humeral articular component for anatomic shoulder arthroplasty. 
         FIG.  9 A  is an exploded side perspective view of the assembly of the convertible humeral implant of  FIG.  7   . 
         FIG.  9 B  is an exploded side perspective view of the assembly of the convertible humeral implant of  FIG.  8   . 
         FIG.  9 C  is a side perspective view of the shell of the convertible humeral implant of  FIGS.  7  and  8    with a peripheral rim and fin(s) to resist subsidence and rotation respectively. 
         FIG.  10 A  is a perspective view of an ingrowth shell of the convertible humeral implant of  FIG.  7    positioned in a prepared humerus bone with an associated lateral buttress washer-plate secured to the bone with screws engaging the implant with a stem. 
         FIG.  10 B  is a second perspective view of the ingrowth shell of  FIG.  10 A . 
         FIG.  11 A  is a perspective view of a handle arranged to hold the head of a new humeral reamer. 
         FIG.  11 B  is a top view of the head of the new humeral reamer that interacts with the handle of  FIG.  11 A . 
         FIG.  11 C  is an elevational view of the head of the new humeral reamer that interacts with the handle of  FIG.  11 A . 
         FIG.  11 D  is a bottom view of the head of the new humeral reamer and of  FIGS.  11 B  and C. 
         FIG.  11 E  is a side view of a portion of the shaft with engagement tip of the shaft and centering handle sleeve to interact with the head of the new humeral reamer of  FIGS.  11 B,  11 C , and  11 D. 
         FIG.  12 A  is a side view of the humeral reamer and shaft preliminarily arranged to be reversibly engaged to each other. 
         FIG.  12 B  is a side view of the humeral reamer and shaft of  FIG.  12 A  reversibly engaged to each other. 
         FIG.  13 A  is a perspective view of the humeral reamer and shaft of  FIG.  12 A  arranged through a transhumeral passage in the humerus to prepare a humerus for the installation of the new humeral implant. 
         FIG.  13 B  is a perspective view of the humeral reamer and shaft of  FIG.  13 A  arranged through a transhumeral passage in the humerus for a second step to prepare a humerus for the installation of the new humeral implant. 
         FIG.  13 C  is a perspective view of the humeral reamer and shaft of  13 A arranged through a transhumeral passage in the humerus for a third step to prepare a humerus for the installation of the new humeral implant. 
         FIG.  13 D  is a perspective view of the prepared humerus and transhumeral sheath after a fourth step to prepare the humerus for the installation of the new humeral implant where the reamer shaft and head of  FIG.  13 A  are disengaged and removed. 
         FIG.  14 A  is a side view of the humeral reamer and handle to prepare a humerus for the installation of a new convertible humeral implant. 
         FIG.  14 B  is a bottom view of the humeral reamer of  FIG.  14 A . 
         FIG.  14 C  is a perspective view of the humeral reamer of  FIG.  14 A  and shaft of  FIG.  11 E  arranged through a transhumeral passage in the humerus for a step to prepare a humerus for the installation of the new convertible humeral implant. 
         FIG.  14 D  is a perspective view of the prepared humerus and transhumeral sheath after steps to prepare the humerus for the installation of the new convertible humeral implant where the reamer shaft and head of  FIG.  14 C  are disengaged and removed. 
         FIG.  15 A  is an elevational view of the new modular glenoid reamer and handle. 
         FIG.  15 B  is a second elevational view of the new modular glenoid reamer of  FIG.  15 A . 
         FIG.  15 C  is a side perspective view of a handle arranged to hold the head of the new glenoid reamer of  FIG.  15 A . 
         FIG.  16 A  is a perspective view of the glenoid reamer of  FIG.  15 A  and shaft of  FIG.  11 E  arranged through a transhumeral passage in a humerus to prepare the glenoid for a glenoid implant. 
         FIG.  16 B  is a second perspective view of the glenoid reamer and shaft of  FIG.  16 A  arranged through a transhumeral passage in a humerus to prepare the glenoid for a glenoid implant. 
         FIG.  16 C  is a third perspective view of the humerus and glenoid of  16 A after the glenoid and humerus have been prepared by humeral and glenoid reamers of  FIGS.  13 A and  16 A  through a transhumeral passage in the humerus. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Shoulder arthroplasty surgery traditionally requires transection of the subscapularis tendon, dislocation of the shoulder joint and resection of the head  2  of the humerus bone  1  at the level of plane  6  of the anatomic neck ( FIG.  1 A ) to gain sufficient access to prepare and resurface the glenoid  40  ( FIG.  1 B ). Using a novel transhumeral method allows for proper access to the glenoid  40  while sparing the subscapularis tendon and avoiding dislocation and aggressive resection of humeral head bone  2 . Novel humeral implants  10 ,  13 ,  17  ( FIGS.  2 A,  5 ,  6 A,  6 B,  7 ,  8 ,  9 A,  9 B,  10 A ,  10 B) are usable with this novel transhumeral method, which provides a minimally invasive technique, but can also be used with traditional surgical techniques. 
     In the novel transhumeral method, the components of the new humeral implants  10 ,  13 ,  17  can be inserted without cutting the rotator cuff nor dislocating the shoulder joint through non-bony soft-tissue passageways with or without the assistance of transhumeral tunnel  7  to the shoulder. The novel humeral implants  10 ,  13 , 17  avoid the limitations associated with traditional humeral implants  35  having round, not oval shaped, articular components  36  with offset intramedullary canal stems  37  designed to be fit in the intramedullary canal  38  of the humerus  1  ( FIG.  2 B ). Limitations associated with traditional humeral implants  35  include but are not limited to aggressive humeral bone resection, complicated implant removal, and difficulty in obtaining anatomic parameters of humeral version, height, depth, inclination, and radius of curvature. 
     The novel humeral implant  10  also has improvements over other humeral implants  39  fixed in the humeral metaphysis bone  5  ( FIG.  2 C ). The humeral implant  39  has a round articular surfaces  36   a  and intersecting elongated fins  39   a ,  39   b  extending from the component comprising the surface  36   a . The novel humeral implant  10  is improved over implant  39 , at least in that the novel implant utilizes the native dense articular surface  3  and its subchondral bone  64  and non-articular lateral bony cortex  4  of the humerus for improved bony fixation and support of the implant ( FIG.  2 A ). The dense articular surface  3  comprises a thickness. Therefore, even when the humeral head bone  2  is prepared, such as shown in  FIGS.  2 A and  13 D , to receive the novel implant at least a portion of the articular surface  3  is often retained after such preparation and thereby provides support for the implant. 
     The novel humeral implant  10  also allows for easier removal and bone preservation during revision surgery. New humeral implants  13 ,  17  ( FIGS.  7 ,  8   ) also allow convertibility not afforded by prior art implants, such as implant  39 . In some embodiments, the novel humeral implant  10  has a smaller articular humeral component  26 , having a smaller humeral articulating surface  20   a , and only partially resurfaces the worn and damaged humeral articular surface  3  ( FIG.  5   ), as compared to the articular humeral component  11  and articulating surface  20  of  FIG.  2 A . 
     The novel humeral implant  10  preserves the dense quality bone of the anatomic head  2  and comprises a removeably attached stem  12   a ,  12   b  which does not reside in nor rely on the intramedullary canal  38  for fixation ( FIGS.  2 A,  3 D,  3 E,  5   ). In some embodiment, the implant  10  is modular at least in that the stem is connectable to the articular humeral component  11 . The implant  10  obtains stability from contact with good quality bone from the anatomic head  2  and non-articular lateral bony cortex  4  of the humerus  1 . The stem  12   a ,  12   b  is positioned in a transhumeral tunnel  7  along a central axis of the humeral metaphysis  5  allowing for the use of articular humeral components  11 ,  26  each with a smooth articulating surface  20 . In some embodiments, the articulating surface comprises variable more anatomic anterior-to-posterior and superior-to-inferior radii of curvature ( FIGS.  3 A,  3 B,  3 C,  3 D,  3 E,  4   ). 
     In some embodiments, the underside of the articular humeral components  11 ,  26  has a bony ingrowth surface  21  and/or other bone adherent features. In some embodiments, the articular humeral component  11  can also have a central coupling site  22  or off-center coupling site  22   a  for the stem  12   a ,  12   b  ( FIGS.  3 B and  4   ). 
     In some embodiments, the novel humeral implants  10 ,  13 ,  17  comprise a stem  12   a ,  12   b ,  16  that provides slidable engagement with the bone of the humeral metaphysis  5  and/or non-articular lateral bony cortex  4  of the humerus  1  which allows for more physiologic loading of the humeral bone  1 ,  2 ,  3 ,  5  than with traditional humeral implants  35  and humeral implants  39 . Additionally, in the case of a periprosthetic humeral fracture complication, the design of the new humeral implants  10 ,  13 ,  17  will provide for a pattern of proximal humeral fracture at the end of the unfixed stem, more easily managed than those predicted to occur with traditional humeral implants  35  and humeral implants  39  and which does not compromise implant fixation. 
     The worn articular surface  3  of the humerus  1  can be prepared with a modular transhumeral reamer  50 ,  80  ( FIGS.  11 A,  11 B,  11 C,  11 D,  11 E,  12 A,  12 B,  13 A,  13 B,  13 C,  13 D,  14 A,  14 B,  14 C,  14 D ). The modular transhumeral reamer  50 ,  80  has a transhumeral reamer shaft  75  and modular cutting reamer head  65 ,  81  with an attached handle  51  that still allows the reamer head  65 ,  81  to spin around its central axle  55  in the ring end  52  while it is held in position by the handle  51 . In one embodiment of the reamer  50 , head  65  preserves a portion of the anatomic head  2 ,  64  of the humerus to provide a sufficient bony support and fixation for the humeral implant  10 . In another embodiment of the reamer  80 , the reamer head  81  which reams into the vault of the humeral metaphysis  5  to allow for new convertible humeral implants  13 ,  17  ( FIGS.  14 A,  14 B,  14 C,  14 D ). 
     Each convertible implant  13 ,  17  comprises an articular humeral component  13   a ,  17   a  and a stem  16 . The articular humeral component  13   a  comprises a shell  15  and an articular surface component  18 . The articular surface component  18  comprises a convex articulating surface  20  and a coupling surface  29 . The articular humeral component  15   a  comprises the shell  15  and an articular surface component  14 . The articular surface component  14  comprises a concave articulating surface  25  and a coupling surface  29 . The stem  16  is the same as stem  12   a ,  12   b , except that stem  16  may have a shorter longitudinal length as compared to stem  12   a ,  12   b  to account for the space occupied by the shell and portions of the articular humeral component  13   a ,  17   a.    
     Implants  13 ,  17  allow interchangeability of articular surface component  14 ,  18  with either the convex or concave articulating surface  20 ,  25  to allow easy conversion between reverse shoulder arthroplasty and anatomic shoulder arthroplasty ( FIGS.  7  and  8   ). The novel convertible humeral implants  13 ,  17  each use the stem  16  and the shell  15  ( 9 A,  9 B,  9 C). The articular surface components  14 ,  18  comprise coupling surfaces  27 ,  29  that reversibly connect to the coupling surface  28  of the shell  15  ( FIGS.  7 ,  8 ,  9 A,  9 B,  9 C ). The coupling surfaces  27 ,  29  of the articular portions  14 ,  18  may possess variable geometry and one of a variety of reversible coupling mechanisms, such as threads. The articular portions  14 ,  18  may be modular and possess structural voids to reduce weight. The shell  15  may comprise variable protruding geometry with a bony ingrowth surface  21 , a peripheral rim  19  to rest upon the prepared cortical rim  9  of the proximal humerus and fins or other prominences  45  extending from the protruding side of the shell  15  ( FIGS.  7 ,  8 ,  9 A,  9 B,  9 C,  10 A,  14 D ). 
     The stem  12   a ,  12   b ,  16  is positioned to reside in the transhumeral tunnel  7  along a central axis of the humeral metaphysis  5  transverse to the plane  6  of the humeral anatomic neck, such as shown in  FIGS.  2 A,  5  and  7   . In some embodiments, the stem  12   a ,  12   b ,  16  and the transhumeral tunnel  7  are perpendicular to the plane  6  of the humeral anatomic neck. The stem  12   a ,  12   b ,  16  can possess a first end  23  with a coupling feature  23   a  to engage the opposite coupling feature  22 ,  22   a  of the humeral implants  10 ,  13 ,  17 . In some embodiments, the coupling features  22 ,  22   a ,  23   a , comprise threads, a press fit, or a morse taper, or other suitable coupling mechanism to join the stem to the articular component  11 ,  13   a ,  17   a ,  26 . It is possible for the male or female counterpart to be on either the stem  12   a ,  12   b ,  16  or the articular component  11 ,  13   a ,  17   a ,  26  with the opposite counterpart on the other of the stem  12   a ,  12   b ,  16  or the articular component  11 ,  13   a ,  17   a . In some embodiments, in the case of the coupling feature  22  comprising threads, the coupling feature  22  is a receiver having a peripheral wall surrounding an opening for receiving the stem  12   a ,  12   b ,  16 , the peripheral wall comprises interior threads for engaging the threads at the first end  23  of the stem. In some embodiments, the stem  12   a ,  16  comprises a second coupling feature, such as threads or a press-fit, at a second end  24  of the stem opposite the first end as shown for stem  12   a  in  FIG.  3 D  (not shown for stem  16 ). 
     In some embodiments, the second end of the stem  12   b ,  16  does not comprise a second coupling feature but instead may be smooth, such as shown in  FIGS.  3 E and  9 A . The second end of the stem  12   a ,  12   b ,  16 , whether comprising a second coupling feature or not, obtains contact and stability against the bone of non-articular lateral bony cortex  4  and/or the bone of the humeral metaphysis  5  ( FIGS.  2 A,  5 ,  7 ,  8   ), when implanted. In various embodiments, the stem may comprise different lengths. In some embodiments, the stem comprises a length such that the stem engages only the bone of the metaphysis  5 . In some embodiments, the stem comprises a length such that the stem extends beyond the metaphysis  5  to also engage the non-articular lateral bony cortex  4 , and the stem may or may not extend past the lateral end of the lateral bony cortex  4 . Therefore, the stem can be contained within the transhumeral tunnel or may extend out of the transhumeral tunnel at the lateral end of the lateral bony cortex  4 . In some embodiments, the stem  12   a ,  12   b  comprises a length in the range of 1 centimeter (cm) and 12 cm, inclusive. In some embodiments, the stem  16  comprises a length in the range of 1 cm and 6 cm, inclusive. In some embodiments, the stem  12   a ,  12   b ,  16  comprises a length that is configured to engage sufficient structural bone of the humerus to resist non-longitudinal displacement of the stem. 
     In some embodiments and applications, the stem  12   a ,  12   b ,  16  also engages a coupling site  31  of the washer-plate  30  on the non-articular lateral bony cortex  4  of the humerus to improve implant stability ( FIGS.  6 A,  6 B,  10 A,  10 B ). In some embodiments, the coupling site  31  comprises threads on a wall of the aperture where the stem is received. Therefore, when the second end  24  of the stem comprise threads, the thread the stem engage the thread of the coupling site  31 . 
     In some embodiment and applications, the stems  12   a ,  12   b ,  16  are configured for slidable engagement with the non-articular lateral bony cortex  4  of the humerus, the washer-plate  30 , and/or the bone of the humeral metaphysis  5  to allow more physiologic load transmission of joint compressive forces to the remainder of the bone of the humerus  1  through the humeral implants  10 ,  13 ,  17 . The stem  12   a ,  12   b    16  is configured not to be axially fixed within the transhumeral tunnel, but instead to slide within the transhumeral tunnel  7 , including after implantation surgery is complete, i.e. post-surgery. The stem can slide longitudinally within the transhumeral tunnel  7  and axially along a longitudinal axis  12   c ,  16   a  of the stem, in the directions A and B of  FIG.  2 A  and directions C and D of  FIG.  7   . The stem  12   a ,  12   b    16  can be limited in its sliding range of motion in the first direction B, D, at the first end  23  by the articular component  11 ,  13   a ,  17   a  engagement with the humeral head. The stem does not axially shelter the load born by the articular component from the surrounding proximal humeral bone in direction B, D. This non-load-sheltering aspect of the stem contributes to more physiologic load transmission of joint compressive forces to the remainder of the bone of the humerus  1  through the humeral implants  10 ,  13 ,  17 . In some embodiments, the width or diameter of the stem  12   a ,  12   b ,  16  less than the width or diameter of the transhumeral tunnel  7  and therefore stem does not friction fit against the wall(s) of the transhumeral tunnel  7  and therefore the stem is slidable within the transhumeral tunnel  7 , including post-surgery. In some embodiments, the stem  12   a ,  12   b ,  16  can be provided with a smooth exterior, such as a smooth exterior surface below the coupling feature  23   a  at the first end  23  of the stems shown in  FIGS.  3 E and  9 A . And, at least the second end  24  may be smooth, such as shown in  FIGS.  3 E and  9 A . In some embodiments, the stem has a uniform width and cross-section along the longitudinal length of the stem or a portion thereof. 
     In some embodiments, the second end  24  of the stem  12   a ,  12   b ,  16  is enlarged to prevent movement toward the articular component in the direction A, C, where the enlarged portion engages with a portion of the tunnel  7 , which is narrower than the enlarged portion, at least in part, to prevent further movement in the direction A, C. In some embodiments, the stem  12   a ,  12   b ,  16  comprises ridges, fins, and/or unidirectional ridges and these features of the stem do not limit movement of the stem away from the articular component along its axis, such as in the direction B, D. In some embodiments, the stem  12   a ,  12   b ,  16  may be considered nonadherent within the tunnel  7  in that they allow movement away from the articular component, such as in the direction B, D. The range of movement in a first direction of the stem within the tunnel may be limited by the articular components&#39; engagement with the prepared portion of a proximal humerus via the connection between the stem and the articular components. In some embodiments, the range of movement of the stem in a second direction, opposite the first direction, in the tunnel  7  may be limited by an enlarged second end  24  of the stem and its engagement with the tunnel or another fixture. 
     In some embodiments, the washer-plate  30  does not have a coupling site and instead a nut (not shown) is fixed to the threaded second end  24  of the stem  12   a ,  12   b ,  16  after the plate (e.g. to the left of the plate in  FIG.  6 A ). In such embodiments, the stem, by not being fixed to the plate, the non-articular lateral bony cortex  4 , or the perimeter of the transhumeral tunnel  7 , the stem is allowed movement along the axis of the stem within a range bounded by the nut. The nut limits the range of movement, in the second direction, away from the non-articular lateral bony cortex  4  and toward articular humeral component  11  or shell  15 , but not towards the non-articular lateral bony cortex  4 . 
     Alternatively, the stems  12   a ,  12   b ,  16  can capture either the non-articular lateral bony cortex  4  of the humerus or an optional washer-plate  30  and the articular humeral component  11  or the shell  15  of the humeral implants  10 ,  13 ,  17 , serving to compress them together against the intervening elements of humeral bone  3 ,  4 ,  5  ( FIGS.  3 D,  6 A,  6 B,  10 A,  10 B ). In some embodiments, screws  33  can be used through cannulations  32  to help secure the washer-plate  30  to the non-articular lateral bony cortex  4  of the humerus ( FIGS.  6 A,  10 A ). The screws  33  can be used to compress the washer-plate  30  against lateral bony cortex  4  of the humerus  1  or can be fixed angle and locking to achieve rigid fixation to the humerus bone  1 . Additional screws  33  can also bridge between cannulations  32  in the washer-plate  30  and screw optional coupling sites  34  of the humeral implants  10 , 13 , 17 . 
     The portions of the shell  15  and the articular humeral components  11 ,  26  that interface with the bone may have a suitable protruding bony ingrowth surface(s)  21  to allow long-lasting adhesion to the humeral head  2  and metaphysis bone  5 . Each stem  12   a ,  12   b ,  16  has two ends  23 ,  24  ( FIGS.  3 D and  3 E ). One end  23  removeably attaches to the coupling device  22  of the shell  15  or the articular humeral components  11 ,  26  and another end  24  which engages the non-articular lateral bony cortex  4  of the humerus or the coupling site  31  of an optional washer-plate  30  fixed to the non-articular lateral bony cortex  4  of the humerus, or a nut, as explained above. In some embodiments, the remainder of the stem  12   a ,  12   b ,  16  may possess a bone ingrowth surface but ideally would not to facilitate slidable engagement and removal as necessary. Alternatively, the end  24  of the stem  12   a ,  12   b , 16  may be smooth and allow slidable contact with the lateral washer-plate  30 , the non-articular lateral bony cortex  4  and/or transhumeral tunnel  7  along a central axis in the metaphysis  5  of the humerus  1 , as more fully explained above. 
     In some embodiments, modular transhumeral reamers  50 ,  80 ,  90  are utilized to prepare the humeral and glenoid surfaces  3 ,  42  for novel implant application ( FIGS.  12 A,  14 A,  15 A ). Reamer  50 ,  80 ,  90  comprises a cutting reamer head  65 ,  81 ,  91  with an axle  55 , a central cannulation  56 ,  93 , and a handle  51  ( FIGS.  11 A,  11 B,  11 C,  11 D,  11 E,  14 A,  14 B,  15 A,  15 ,  15 B,  15 C ). The handle  51  has a ring end  52  which captures the axle  55  and allows the axle  55  and the reamer head  65 ,  81 ,  91  to spin freely in the ring end  52 . The reamer head  65 ,  81 ,  91  has a surface configured for bone drilling or cutting  66 ,  67 ,  83 ,  92 ,  96  and a slot  57 ,  98 , opposite the cutting or drilling surface configured for temporary engagement with the tip  76  of the transhumeral reamer shaft  75 . The shaft  75  of the reamers  50 ,  80 ,  90  can be driven by hand or a power drill  77 . 
     The reamers  50 ,  80 ,  90  are modular and may be used through open surgical approaches used for traditional open shoulder arthroplasty surgery or they can be used for minimally invasive rotator cuff sparing shoulder arthroplasty surgery through a transhumeral tunnel  7  approach which spares the rotator cuff, preserves humeral bone, and avoids dislocation of the shoulder joint associated with traditional approaches. For the transhumeral approach, the reamers  50 ,  80 ,  90  are inserted by their handle  51  through a non-bony passageway, likely an interval in the rotator cuff, and into position in the shoulder joint while the transhumeral reamer shaft  75  is inserted through the transhumeral tunnel  7  and an optional protective transhumeral sheath  8  into the shoulder joint and reversibly coupled by the engagement tip  76  to the engagement slots  57 ,  98  of the reamer  50 ,  80 ,  90  ( FIGS.  13 A,  13    B,  13 C,  13 D,  14 C,  14 D,  16 A,  16 B,  16 C). The reamer  50 ,  80 ,  90  can be configured to be used to drill and cut transverse or perpendicular to the axis of the reamer shaft  75 , particularly not off-axis. For example, the cut surfaces  65   a, b, c , of the prepared portion of humeral head shown in  FIG.  13 D  after the use of the reamer in  FIGS.  13 B and  13 C  shows that the reamer can cut planes that are perpendicular to the axis of the reamer shaft  75 . There is a centering sleeve  78  moving freely around the reamer shaft  75  that engages a centering cannulation  58 ,  82  on the reamer heads  65 ,  81  to ensure the reamer cuts the humeral surface  3  on axis, i.e perpendicular to the transhumeral tunnel  7  and the reamer shaft  75 . The glenoid reamer  90  does not require a centering sleeve  78  but rather is cannulated  93  to ream over a guide pin  100  positioned through the transhumeral tunnel  7  and the protective transhumeral sheath  8  and into the surface  42  and vault  41  of the glenoid  40  (FIGS.  16 A,  16 B,  16 C). The reamer shaft for the glenoid also possesses a cannulation  74  for the guide pin  100 . 
     The cutting surfaces  66 ,  67 ,  83 ,  84 ,  92 , and  96  vary in geometry and aggressiveness to optimally prepare the bone  3 ,  5 ,  41 ,  42  for their respective implants  10 ,  13 ,  17 . The reamer head  65  has two cutting surfaces  66 ,  67 , one cutting surface  66  to cut the humeral surface  3  and the other cutting surface  67  to cut the perimeter to the level  6  of the anatomic neck of the humerus  1  ( FIG.  11 D ). The reamer head  81  for the convertible humeral implant  13 , 17  also has two cutting surfaces, one protruding cutting surface  83  with variable geometry to cut a humeral metaphyseal socket  85  and a second  84  to cut the perimeter near the level  6  of the anatomic neck of the humerus  1 ( FIGS.  14 A,  14 B ). The cutting surface  92 ,  96  of the glenoid reamer  90  has a protruding aggressive cutting surface  92  to cut a precise glenoid cavity  44  into the glenoid vault  41 ; an intermediate smooth non-cutting surface  94  to help keep the reamer  90  on axis and prevent damage to prepared peripheral glenoid surface bone  43 ; and a less aggressive cutting surface  96  on the peripheral rim  95  of the glenoid reamer head  91  to less aggressively prepare the peripheral aspect of the glenoid surface  42  ( FIGS.  16 A,  16 B,  16 C ). 
     In some embodiments, the implants  10 ,  13 ,  17  can be implanted through an implant method that comprises the following steps: fixing an articular humeral component  11 ,  26 ,  13   a ,  17   a  comprising an articular surface  20 ,  25  to a prepared articular portion of a proximal humerus; placing a stem  12   a ,  12   b ,  16  in the tunnel  7  in the proximal humerus without fixing the stem within the tunnel  7 ; and, connecting the stem to the articular humeral component. Depending on the chosen approach for implantation, the order of the foregoing steps can vary. Further, in some embodiments, the connecting step is not used, for example, when the stem is already fixed to or formed with the articular humeral component. 
     In some embodiments, the step of connecting occurs before the articular humeral component is fixed to the proximal humerus, and in some cases, before the stem is placed in the tunnel  7 . For example, when the stem and the articular humeral component are implanted as a unit, the stem being placed from the articular side of the humerus into the tunnel  7  toward the lateral bony cortex  4 , in the direction D, B. The stem being moved into the tunnel until the articular humeral component is seated on the prepared articular portion. The articular humeral component may be fixed at or after the humeral component is seated on the prepared articular portion. 
     In some embodiments, the stem is placed through tunnel  7  from the lateral bony cortex  4  side in the direction A, C and is connected to the articular humeral component before the articular humeral component is fixed to the prepared articular portion of a proximal humerus. In some embodiments, the stem is placed in the tunnel, the articular humeral component is fixed to the prepared articular portion of a proximal humerus, and then the stem is connected to the articular humeral component. 
     In some embodiments, the step of connecting occurs during the step of placing. For example, the stem may be connected articular humeral component when it is placed within the tunnel. As explained above, in some embodiments, the stem is placed in the tunnel  7  in the proximal humerus without fixing the stem within the tunnel against post-surgery longitudinal movement. 
     It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.