Abstract:
A humeral prosthesis includes a stem component and a head component joined by an inclination component. The inclination component is provided with an opening that is designed to accommodate a pair of expandable tabs extending from a side of a plate. The plate is also provided with a taper extending opposite to the pair of expandable tabs. Inclination angle, radial offset, and version are adjustable and are separately and independently set and fixed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of application Ser. No. 11/508,891, filed Aug. 24, 2006, now U.S. Pat. No. 8,323,347 issued Dec. 4, 2012, which claims the benefit of U.S. Provisional Application Ser. No. 60/710,943, filed Aug. 25, 2005, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to surgical reconstitution of the shoulder and, in particular, to prosthetic replacement of the humerus. 
     BACKGROUND OF THE INVENTION 
     The shoulder joint is a ball-and-socket joint with unique features that allow for exceptional freedom of movement. The hemispherical head of the humerus and the glenoid capsule of the scapula support the articular surfaces of the shoulder joint. The head of the humerus is significantly large relative to the shallow glenoid cavity. In addition, ligaments in the shoulder act largely to limit the degree of movement allowed in the joint: They do not act to maintain apposition of the joint surfaces. As a consequence of these and other special characteristics, the shoulder joint exhibits every variety of movement: flexion, extension, abduction, adduction, circumduction, and rotation. The range of movements comes as some cost to joint stability, however. 
     Shoulder instability and other maladies of the shoulder joint, such as arthrosis or fracture, can be sufficiently acute that prosthetic replacement of compromised joint features may be indicated. Replacement of the humeral head involves resecting the humeral head from the humerus and installing a humeral prosthetic at the resection. 
     Early shoulder prostheses attempted to mimic the upper portion of the humerus and extending to include the humeral head. They typically were unitary structures that included a stem to be anchored in the humeral canal and a hemispherical head to be positioned within the glenoid cavity of the scapula. 
     Later developments allowed for adjustments to the geometry of the prostheses. Differences in patient anatomy and surgical techniques necessitated maintaining large inventories of the early, unitary prostheses. Prostheses were kept on-hand with heads and stems of different sizes and various relative tilt angles and radial offsets. 
     The more-recently devised modular prostheses generally are modular systems. Their modularity allows flexibility with respect to either the tilt angle or the radial offset between the head and stem. Although some of these prior art modular systems utilize either a “standard” head or a “standard” stem, most still require a plurality of either the heads or the stems to provide complete tilt angle and radial offset flexibility. None of the prior art systems provides complete tilt angle and radial offset flexibility without requiring different modular head or stem components of each given size. As a result, substantial inventories are maintained of either the stems or heads, which are the most expensive components. Moreover, most of the known systems provide incomplete adjustability of prosthetic geometry. 
       FIG. 1  illustrates a modular humeral-prosthesis  1  disclosed in DE 19509037 to Habermeyer. The humeral-prosthesis  1  allows for adjustment of radial offset, inclination angle, and version (anteversion/retroversion). Humeral-prosthesis  1  includes a stem-module  3  that features a shank  5  having an upper-shank portion  7  and a tongue/tab  9  that supports a pin  11 . Pin  11  hinges an angle-adapter  13  to the rest of the stem-module  3 . Angle-adapter  13  fits over tongue/tab  9  and pivots on pin  11  through an inclination angle a as shown in  FIG. 2 . The angle-adapter  13  can be locked in place to retain a desired inclination angle. 
     Humeral-prosthesis  1  also includes a coupling adapter  17 , shown in  FIGS. 1-4 . The coupling adapter  17  is shown in  FIG. 3  separated from other prosthetic components. The coupling adapter  17  includes an adapter plate  27 . A male Morse taper  29  extends from one side of adapter plate  27 . A ball joint  31  extends from the adapter plate  27  on the side opposite the male Morse taper  29 . The ball joint  31  is located eccentrically on the adapter plate  27 . The eccentricity of the ball joint  31  on the adapter plate  27  allows for adjustment of a radial offset between the prosthetic stem  3  and a spherical cap  27  secured to the male Morse taper  29 , as described further below. Once established, the radial offset is fixed using set screw  23  ( FIG. 4 ). 
     Referring to  FIG. 5 , adjustment of anteversion/retroversion is provided by the angle-adaptor  13 . As discussed above, the angle adaptor  13  pivots on the axis  11  at the top end  7  of the stem  3  to adjust the inclination angle a. In the view of  FIG. 5  it can be seen that the angle adapter  13  is beveled at its interface with coupling adapter  17 . The beveling allows the adapter  13 , and hence the stem  3 , to pivot by way of ball joint  31  with respect to the coupling adapter  17 . The stem  3  and coupling adapter  17  rock through an angle b to one face  15  or the other of coupling adapter  17 . Faces  15  on coupling adapter  17  act as stops to define the maximum pivot to either side. Set screw  23 , used to retain the desired radial offset, also fixes the desired version. 
     A need exists in the prior art for a modular shoulder prosthesis that features universal setting of radial-offset, inclination angle, and anteversion/retroversion, with independent fixing of each setting. 
     SUMMARY OF THE INVENTION 
     The present invention provides a humeral prosthetic and surgical methods for reconstitution of a shoulder joint. The humeral prosthetic allows universal adjustment to the prosthetic inclination angle, radial offset, and version. In an exemplary embodiment, the humeral prosthetic includes three components: (i) a stem for attachment to the humerus, (ii) a spherical head for replacing the humeral head, and (iii) a coupling adapter joining the stem and the spherical head. At least one of the settings for the three adjustments noted above may be fixed independently of the other two settings. Preferably, a setting for each of the three adjustments is fixed independently. 
     In an exemplary embodiment, each modular component includes means for setting and fixing a respective one of the three adjustments noted above. More specifically, the exemplary prosthetic stem includes means for setting and fixing the inclination angle of the prosthesis. The exemplary spherical head includes means for setting and fixing the radial offset. The coupling adapter includes means for setting and fixing version. 
     The present invention also provides a method of conducting surgery by: (i) providing a humeral prosthetic comprising a humeral attachment; an adapter comprising a plate, a taper extending from a first side of the plate, a concavity formed along a diameter on a second side of the plate, and an expandable locking component extending from the second side of the plate; and a spherical head; (ii) providing the humeral prosthetic within a patient&#39;s humerus; and (iii) independently adjusting at least one of the radial offset of the spherical head, the inclination angle of the humeral attachment, and the version of the adapter, relative to the other two. 
     These and other features and advantages of the invention will be more apparent from the following detailed description that is provided in connection with the accompanying drawings and illustrated exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a prior art prosthesis shown in anterior/posterior elevation; 
         FIG. 2  is a detailed view of the upper portion of the prior art prosthesis illustrating adjustment of the inclination angle; 
         FIG. 3  is a side view of an adapter portion of the prior art prosthesis shown in  FIGS. 1 and 2 ; 
         FIG. 4  is a partial cut-away view illustrating details of the upper portion of the prior art prosthesis shown in  FIG. 2 ; 
         FIG. 5  is a detailed view from above the prosthesis illustrating the beveled faces allowing adjustment of version in the prior art prosthesis shown in  FIGS. 1-4 . 
         FIG. 6  illustrates a humeral prosthesis according to an exemplary embodiment of the present invention; 
         FIG. 7  illustrates an angle adapter and a coupling adapter enlarged to show detail; 
         FIG. 8  shows a coupling adapter viewed in elevation according to the invention; 
         FIG. 9  shows the coupling adapter of  FIG. 8  viewed in side elevation; 
         FIG. 10  shows details of the coupling adapter of  FIGS. 8 and 9 ; 
         FIG. 11  illustrates a locking screw according to the invention; 
         FIG. 12  illustrates another locking screw according to the invention; 
         FIG. 13  illustrates an exploded view of the prosthesis of the present invention, including an inclination component, a coupling adapter, a screw and a spherical head; 
         FIG. 14  illustrates a perspective view of the coupling adapter of  FIG. 13 ; 
         FIG. 15  illustrates a perspective cross-sectional view of the coupling adapter of  FIG. 14 ; 
         FIG. 16  illustrates a perspective view of the screw of  FIG. 13 ; 
         FIG. 17  illustrates a perspective view of the spherical head of  FIG. 13 ; 
         FIG. 18( a )  illustrates an exploded schematic view of the prosthesis of the present invention, including an inclination component, a coupling adapter, a screw and a spherical head; 
         FIG. 18( b )  illustrates the prosthesis of  FIG. 18( a ) ; 
         FIGS. 19( a )-( c )  illustrate schematic views of the prosthesis of  FIG. 18( b ) ; 
         FIGS. 20( a )-( d )  illustrate schematic views of the inclination component of the prosthesis of  FIG. 18( b ) ; 
         FIGS. 21( a )-( e )  illustrate schematic views of the coupling adapter of the prosthesis of  FIG. 18( b ) ; and 
         FIGS. 22( a )-( e )  illustrate schematic views of the spherical head of the prosthesis of  FIG. 18( b ) . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention provides a humeral prosthetic and surgical methods for reconstitution of a shoulder joint. The humeral prosthetic allows universal adjustment to the prosthetic inclination angle, radial offset, and version. In an exemplary embodiment, the humeral prosthetic includes three components: a stem for attachment to the humerus, a spherical head for replacing the humeral head, and a coupling adapter joining the stem and the spherical head, wherein at least one of the settings for the three adjustments noted above may be fixed independently of the other two settings. Preferably, a setting for each of the three adjustments is fixed independently. 
     In an exemplary prosthesis and as detailed below, each modular component includes means for setting and fixing a respective one of the three adjustments noted above. More specifically, the exemplary prosthetic stem includes means for setting and fixing the inclination angle of the prosthesis. The exemplary spherical head includes means for setting and fixing the radial offset. The coupling adapter includes means for setting and fixing version. 
     The invention also provides a method of surgical reconstruction of shoulder by: (i) providing a humeral prosthetic comprising a humeral attachment; an adapter comprising a plate, a taper extending from a first side of the plate, a concavity formed along a diameter on a second side of the plate, and an expandable locking component extending from the second side of the plate; and a spherical head; (ii) providing the humeral prosthetic within a patient&#39;s humerus; and (iii) independently adjusting at least one of the radial offset of the spherical head, the inclination angle of the humeral attachment, and the version of the adapter, relative to the other two. 
     Referring now to the drawings, where like elements are designated by like reference numerals,  FIG. 6  illustrates an exemplary humeral prosthesis according to an exemplary embodiment of the invention.  FIG. 6  illustrates modular humeral-prosthesis  30  including a stem-module  33  that features a shank  35  having an upper-shank portion  37  and a tongue/tab  39  that supports a pin  41 . Pin  41  hinges an inclination component  43  to the rest of the stem-module  33 . Inclination component  43  fits over tongue/tab  39  and pivots on pin  41  through an inclination angle a as shown in  FIG. 2  illustrating the prior art prosthesis. The inclination component  43  includes an opening  44  ( FIG. 7 ) that provides access to a screw (not shown) threaded between a pair of spreadable leaves formed in a portion of the tongue/tab  39 . The spreadable leaves are spread progressively further apart by advancement of the screw and into locking frictional engagement with opposing inside surfaces of the inclination component  43 . The screw is advanced by turning sufficient to fix the position of the inclination component  43  at a desired inclination angle. 
     Humeral-prosthesis  30  also includes coupling adapter  47 , shown in  FIGS. 6-10 . The coupling adapter  47  is shown in  FIG. 7  paired with the inclination component  43 . The coupling adapter  47  includes an adapter plate  57 . An access opening  48  through the adapter plate  57  corresponds to the opening  44  in the inclination component  43  and provides access to the inclination-angle locking screw discussed above. A male Morse taper  59  extends from one side of adapter plate  57 . Morse taper  59  locks into a female Morse taper  49   a  formed in spherical head  49 . A shallow, elongate concavity  55  extends along a diameter of adapter plate  57  on a side opposite the male Morse taper  59 . The elongate concavity  55  complements an elongate convex surface  56  formed on inclination component  43 , discussed in further detail below. 
       FIGS. 8-10  further illustrate details of coupling adapter  47 . A pair of clothespin tabs  61  extends from adapter plate  57 . The clothespin tabs are accepted into a rectangular opening  63  formed in inclination component  43 . A pre-installed locking screw  65  ( FIG. 11 ) or  67  ( FIG. 12 ) is urged within tapped hole  69  between clothespin tabs  61 . The locking screw  65 ,  67  wedges between clothespin tabs  61 . The clothespin tabs  61  spread apart to frictionally-engage inner walls of rectangular opening  63  with sufficient force to fix a relative versional position between inclination component  43  and coupling adapter  47 . In an exemplary embodiment, clothespin tabs  61  may have a square configuration to lock within rectangular opening  63  and to prevent rotation within the inclination block. However, the invention is not limited to this exemplary embodiment, and contemplates additional shapes and geometries for the clothespin tabs  61 , for example, a rectangular or trapezoidal configuration among many others. 
     More specifically, version is adjusted by pivoting adapter plate  57  with respect to inclination component  43 . The components will pivot through angles b of retroversion and anteversion as illustrated in  FIG. 5  showing a prior art prosthesis. Instead of pivoting around a bevel, however, elongate concavity complements convex surface  45  so that the two are mutually engaged throughout the range of motion from +b to −b, the range being determined by the fit of clothespin-tabs  61  within rectangular opening  63 . Once the desired version is achieved, one of the locking screws  65 ,  67  is used to spread the clothespin tabs into locking engagement with inside surfaces delimiting rectangular opening  63 . 
     Referring again to  FIG. 6 , the female Morse taper socket is formed eccentric to a central axis of the spherical head  49 . Radial offset is adjusted by rotating the spherical head  49  around male Morse taper  59  with respect to coupling adapter  47 . The radial offset is fixed in position by the locking interaction of the complementary Morse taper features. 
       FIG. 13  illustrates a an exploded view of the prosthesis of the present invention, comprising inclination component  43 , coupling adapter  47  with clothespin tabs  61 , locking screw  65  and spherical head  49 . Coupling adapter  47  is further detailed in  FIGS. 14 and 15 , which illustrate a perspective view and a perspective cross-sectional view, respectively, of the coupling adapter.  FIG. 16  illustrates a perspective view of locking screw  65  while  FIG. 17  illustrates a perspective view of the spherical head  49 . 
       FIGS. 18-22  illustrate additional schematic views of the prosthesis of the present invention, comprising inclination component  43 , coupling adapter  47  with clothespin tabs  61 , locking screw  65  and spherical head  49 . 
     The above description and drawings illustrate preferred embodiments which achieve the objects, features and advantages of the present invention. It is not intended that the present invention be limited to the illustrated embodiments. Any modification of the present invention which comes within the spirit and scope of the following claims should be considered part of the present invention.