Abstract:
A shoulder prosthesis of a modular type adapted to changing from a direct configuration to an inverted configuration. The prosthesis is particularly non-invasive and has a large modular capacity, permitting full recovery of the articular function following the implant thereof.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to shoulder prosthesis and in particular to modular type shoulder prosthesis, suitable for changing from a direct configuration to an inverted configuration. The direct configuration consists of a shoulder prosthesis wherein a head is associated with the main body of the prosthesis to replace the humeral head, suitable for being coupled with the glenoid, while the inverted configuration consists of a shoulder prosthesis wherein a ball is associated with the glenoid suitable for being coupled with a cup associated with the humerus. 
       BACKGROUND OF THE INVENTION 
       [0002]    Shoulder prostheses according to prior art comprise a main prosthesis body adapted for insertion into the humerus and a ball and socket type coupling to permit relative movements between humerus and glenoid. 
         [0003]    However, said prostheses present numerous drawbacks. For example the prostheses according to prior art do not permit complete recovery of the biomechanical articular function after surgery. In fact the loss of recovery of this function is mainly caused by incorrect suturing of the tuberosities of the humeral head. Lack of functional recovery often makes the prosthesis painful for the patient, and in any case, it limits the shoulder movement of the patient to a large extent. 
         [0004]    Till now, therefore, current shoulder prostheses often have not provided satisfactory recovery of the articular function. 
         [0005]    Furthermore, the prostheses according to prior art often result as being excessively invasive and therefore, in order to permit their insertion, a large amount of bone must be removed, thus causing problems for prosthesis integration and excessive weakening of the bone, especially in the area of the neck of the humeral head. 
         [0006]    Furthermore, the prostheses according to prior art often do not permit the correction of certain important geometric parameters such as the distance between the acromion and the head and the version angle of the head, except by extremely invasive operations requiring the explant of the prosthesis and its total or partial replacement. These operations require interventions that are extremely invasive and painful for the patient, comprising the filing of the neck of the humeral head, with the consequential ablation of a considerable amount of bone. 
         [0007]    The prostheses according to prior art do not permit safe and not particularly invasive attachment to the bone especially in relation to the glenoid. In fact it is often necessary to use numerous very invasive screws which not only complicate the prosthesis implant surgical operation considerably, but also contribute towards weakening the resistant sections of bone that are already particularly reduced from an anatomical point of view. 
         [0008]    For anchoring to the bone, the prostheses according to prior art use pass-through screws that perforate the cortex and penetrate the spongy tissue. 
         [0009]    The use of the drilling method complicates the surgical insertion stage also because incorrect hole drilling can lead to bone fractures. Furthermore, any error in prosthesis positioning also involves the drilling of an invasive hole which can be damaging to bone resistance. 
       SUMMARY OF THE INVENTION 
       [0010]    The object of the present invention is to provide a shoulder prosthesis that overcomes the drawbacks described in relation to prior art. 
         [0011]    These drawbacks are overcome by shoulder prosthesis according to claim  1 . 
         [0012]    Other embodiments of the prosthesis according to the invention are described in the following claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Further characteristics and advantages of the present invention will be made more clear in the description below and the preferred non-limiting embodiments, wherein: 
           [0014]      FIG. 1  shows a perspective view of a shoulder prosthesis according to one embodiment of the present invention; 
           [0015]      FIG. 2  shows a front view of the prosthesis in  FIG. 1 ; 
           [0016]      FIG. 3  shows a cross-section view of the prosthesis in  FIG. 1 , along the section line III-Ill in  FIG. 2 ; 
           [0017]      FIG. 4  shows a side view of the prosthesis in  FIG. 1 ; 
           [0018]      FIG. 5  shows a front view of a detail of a prosthesis according to one embodiment of the present invention; 
           [0019]      FIG. 6  shows a cross-section view of the detail in  FIG. 5 , along the section line VI-VI in  FIG. 5 ; 
           [0020]      FIG. 7  shows a side view of the detail in  FIG. 5 ; 
           [0021]      FIG. 8  shows a cross-section view of the detail in  FIG. 5 , along the section line VIII-VIII in  FIG. 5 ; 
           [0022]      FIG. 9  shows a cross-section view of the prosthesis in  FIG. 3 , along the section line IX-IX in  FIG. 3 ; 
           [0023]      FIG. 10  shows a perspective view of a shoulder prosthesis according to a further embodiment of the present invention; 
           [0024]      FIG. 11  shows a cross-section view in relation to the section line XI-XI in  FIG. 10 ; 
           [0025]      FIG. 12  shows a side view of the prosthesis in  FIG. 10 ; 
           [0026]      FIG. 13  shows a cross-section view of a detail of the prosthesis in  FIG. 10 ; 
           [0027]      FIG. 14  shows a view in separate parts of a shoulder prosthesis according to a further embodiment of the present invention; 
           [0028]      FIG. 15  shows a side view of the prosthesis in  FIG. 14 ; 
           [0029]      FIG. 16  shows a front view of the prosthesis in  FIG. 14  in an assembled configuration; 
           [0030]      FIG. 17  shows a side view of the prosthesis in  FIG. 16 ; 
           [0031]      FIGS. 18 and 19  show views from different angles of a detail of the prosthesis in  FIG. 14 ; 
           [0032]      FIG. 20  shows a perspective view of a prosthesis according to the invention in a configuration of the insertion into a humerus; 
           [0033]      FIG. 21  shows a front view of a shoulder prosthesis according to a further embodiment of the present invention; 
           [0034]      FIG. 22  shows a cross-section view of the prosthesis in  FIG. 21 , along the section line XXII-XXII in  FIG. 21 ; 
           [0035]      FIGS. 23-25  show views in separate parts of the prosthesis in  FIG. 22 , according to further variants of the embodiment; 
           [0036]      FIG. 26  shows a side view of a detail of the prosthesis in  FIG. 21 ; 
           [0037]      FIG. 27  shows a front view of a shoulder prosthesis according to a further embodiment of the present invention; 
           [0038]      FIG. 28  shows a cross-section view of the prosthesis in  FIG. 27 , along the section line XXVIII-XXVIII in  FIG. 27 ; 
           [0039]      FIGS. 29-31  show in separate parts of the prosthesis in  FIG. 27 , according to further variants of the embodiment; 
           [0040]      FIG. 32  shows a side view of a detail of the prosthesis in  FIG. 27 ; 
           [0041]      FIG. 33  shows a front view of a shoulder prosthesis according to a further embodiment of the present invention; 
           [0042]      FIG. 34  shows a cross-section view of the prosthesis in  FIG. 33 , along the section line XXXIV-XXXIV in  FIG. 33 ; 
           [0043]      FIGS. 35-37  show in separate parts of the prosthesis in  FIG. 33 , according to further variants of the embodiment; 
           [0044]      FIGS. 38   a  and  38   b  show side views and in cross section of a detail of the prosthesis in  FIG. 33 ; 
           [0045]      FIG. 39  shows a cross-section view of an enlarged detail of a component of a prosthesis according to the present invention; 
           [0046]      FIG. 40  shows a perspective view in an assembled configuration of a shoulder prosthesis according to a further embodiment of the present invention; 
           [0047]      FIGS. 41 and 42  show side views from different angles of the prosthesis in  FIG. 21 ; 
           [0048]      FIG. 43  shows a plane view from below of the prosthesis in  FIG. 40 ; 
           [0049]      FIG. 44  shows a perspective view in separate parts of the prosthesis in  FIG. 40 ; 
           [0050]      FIG. 45  shows a perspective view of a shoulder prosthesis according to a further embodiment of the present invention; 
           [0051]      FIGS. 46 and 47  show side views from different angles of the prosthesis in  FIG. 45 ; 
           [0052]      FIGS. 48A and 48B  show plane views seen from above and below of the prosthesis in  FIG. 45  respectively; 
           [0053]      FIG. 49  shows a perspective view in separate parts of the prosthesis in  FIG. 45 ; 
           [0054]      FIG. 50  shows a perspective view of a prosthesis according to the present invention in a configuration assembled on a scapula (during preparation); 
           [0055]      FIG. 51  shows a perspective view in separate parts of a shoulder prosthesis according to a further embodiment of the present invention; 
           [0056]      FIG. 52  shows a perspective view in an assembled configuration of the prosthesis in  FIG. 51 ; 
           [0057]      FIG. 53  shows a side view of the prosthesis in  FIG. 52 ; 
           [0058]      FIG. 54  shows an enlarged detail of the prosthesis in  FIG. 53 . 
           [0059]      FIGS. 55-58  show perspective views, side views and views in cross section of shoulder prosthesis according to a further embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0060]    The common elements or parts of elements present in the embodiments described hereafter will be identified by the same numerals. 
         [0061]    In reference to the aforesaid figures, according to one embodiment of the present invention throughout, the numeral  4  indicates a shoulder prosthesis suitable for insertion in a humerus  6 , preferably positioned on the head  8  of said humerus  6 . 
         [0062]    According to one embodiment, the prosthesis  4  comprises a stem  12  suitable for insertion into the humerus to attach the prosthesis  4  on the humerus  6 , the stem identifying a direction of insertion X. 
         [0063]    The prosthesis  4 , according to one embodiment, comprises a main body of the prosthesis  16  or metaphysary component, attachable to said stem  12 , and adapted for insertion at least partially into the humerus positioned on the humeral head  8  having a pair of tuberosities  20 . 
         [0064]    Preferably, the stem  12  has an axis of symmetry in relation to the insertion direction X, in a manner to form a revolving surface adapted to rotation inside said humerus to permit the correct angular positioning of the prosthesis  4  in the humerus. 
         [0065]    The main body of the prosthesis  16  extends according to a prevalent extension Y set at an angle in relation to the insertion direction X in a manner to follow the anatomical angle of the humeral head  8 . Preferably said prevalent extension Y forms a curved line. 
         [0066]    The main body of the prosthesis  16  is adapted to being associated with a spherical head  24  or with a cup  28  in a manner to interact with a glenoid cavity  32 , if necessary covered with a relative plate  142 , or with a glenosphere  36 , respectively. 
         [0067]    Advantageously, the main body of the prosthesis  16  comprises at least two support fins  40  that together form, in relation to a plane perpendicular to said prevalent extension Y, a flare angle a between 60 and 120 degrees in a manner to be abutted by said tuberosities  20  of the humerus, by the internal part of the bone, in an insertion configuration of the prosthesis in the humerus. 
         [0068]    Preferably, said fins  40  together form, in relation to a plane perpendicular to said set at an angle direction, a flare angle a between 80 and 100 degrees. 
         [0069]    Even more preferably, said fins  40  together form, in relation to a plane perpendicular to said set at an angle direction, a flare angle a equal to 90 degrees. 
         [0070]    Advantageously, the support fins  40  present at least one hole  44  adapted to allowing the passage of a suture for the resuturing of said tuberosities  20 . 
         [0071]    Preferably, said fins  40  present three holes  44  arranged along the prevalent extension Y of the main body of the prosthesis  12 , said holes  44  being adapted to allowing the passage of a suture for the resuturing of said tuberosities  20 . 
         [0072]    According to a possible embodiment, said fins  40  present slots  45  adapted to allowing an easier passage of the suture for the resuturing of said tuberosities  20  as well as to permit the insertion of the bone fragments to favour the osteointegration of the prosthesis  4 . 
         [0073]    Advantageously, said support fins  40  have a blade-like configuration and extend from said prevalent extension Y, in such a manner that the main body of the prosthesis  16  assumes a general section that is at least bilobate. 
         [0074]    According to one embodiment, the main body of the prosthesis  16  comprises at least a third fin  46 , preferably positioned symmetrically in relation to said support fins  44 , said third fin extending from the opposite side to the support fins  44  in relation to the prevalent extension Y, in such a manner that the main body of the prosthesis  16  assumes a general “Y” shaped cross-section. 
         [0075]    According to one embodiment, at least one of said fins  40 ,  44  extends, in relation to the axis of the prevalent extension Y, in an increasing distance, moving from a first end  50  of the main body of the prosthesis  16 , from the attachable stem  12 , to a second end  52  of the main body of the prosthesis  16 , opposite to said first end  50 . 
         [0076]    Preferably, the configuration of the main body of the prosthesis  16  comprising two fins  40  and a third fin  46  is adapted to being used for shoulder arthrosis pathologies; a configuration comprising two fins  40 , without the third fin  46 , is preferably used in the case of fractures of the humeral head  8 . 
         [0077]    According to one embodiment of the present invention, said fins  40 , 44  opposite the stem  12 , are operatively connected to a plate or disc  56  attachable by means of form coupling to a coupling portion  60  adapted to creating kinematic coupling with the glenoid. 
         [0078]    According to a further embodiment of the present invention, said disc  56  is associated with a first cone  57 , preferably of the ‘morse’ type adapted to favouring the fixing action of said coupling portion  60  to the main body of the prosthesis  16 , by means of form coupling. The coupling portion  60 , in the form of a spherical head  24  for example, will be provided with a housing having the counter form of the first cone  57  in a manner to ensure the secure blocking of the spherical head  24  on the main body of the prosthesis  16 . 
         [0079]    Preferably, the connection between the main body of the prosthesis  16  and the stem  12 , positioned at said first end  50  of the main body of the prosthesis  16 , is achieved by means of form coupling. 
         [0080]    For example, the stem  12  comprises a threaded pin, which is screwed directly into a relative nut screw  61  of the main body of the prosthesis  16 . Preferably, the main body of the prosthesis  16 , positioned at said first end  50 , comprises a connecting protuberance  62 , presenting a second cone  62 ′, preferably of the ‘morse’ type, and a threaded portion  63 . The stem  12  possesses a conical seat  65  adapted to blocking inside the second cone  62 ′ and a threaded hole  66 . According to a possible embodiment, said threaded hole  66  is adapted to being screwed into the threaded portion  63  of the connecting protuberance  62 . 
         [0081]    Preferably, the connecting protuberance  62  comprises a rotation-proof ridge  67  adapted to preventing undesirable rotation between the stem  12  and the main body of the prosthesis  16 . 
         [0082]    According to a possible embodiment, the stem  12  presents at least one groove  69 , being parallel to the direction of the prevalent extension X-X for example, in a manner to create a rotation proof action of stem  12  following the new growth of the bone; in other words, as the bone grows it will penetrate the groove  69  to form an undercut. 
         [0083]    According to one embodiment, the coupling portion  60  comprises a spherical head  24 , on the opposite side of the main body of the prosthesis  16 , adapted to creating kinematic coupling with a glenoid  64  of the attachable scapula. 
         [0084]    According to one embodiment, said disc  56  presents at least one ribbing  68  positioned on an axial rim and said coupling portion presents at least one groove  72  having the counter form of said ribbing  68 . 
         [0085]    Preferably, the disc  56  comprises four ribbings  68  in step formation, preferably perpendicular to each other, and in turn, the coupling portion  60  presents four grooves  72  set perpendicular to one another to permit coupling with said ribbing  68 . 
         [0086]    Preferably, the area of the section of the fins  40 , 44  in relation to a plane perpendicular to said prevalent extension Y does not exceed 85% of the total area of a disc associated with the main body of the prosthesis for the connection of the main body of the prosthesis to a coupling portion  60 . 
         [0087]    According to a further embodiment of the present invention, said coupling portion  60  comprises a cup  28  adapted to create kinematic coupling with a glenosphere  36  associated with the corresponding scapula. 
         [0088]    According to an advantageous embodiment of the present invention, the main body of the prosthesis  16  is associated, by means of a male-female type form coupling to a coupling portion  60  in the form of a cup  28  adapted to interacting with a glenosphere  36  attachable to a corresponding glenoid  64 . 
         [0089]    According to one embodiment, the main body of the prosthesis  16  comprises a first connecting element  76 , for example parallel to said prevalent extension Y, and the coupling portion  60  comprises a second connecting element  78  having the counter form of said first connecting element  76 . 
         [0090]    Advantageously, the coupling between the main body of the prosthesis  16  and the cup  28  is an axial type according to a coupling direction parallel to said first and second connecting element  76 , 78  in a manner to permit the fastening and release of the cup  28  from the main body of the prosthesis  16  in a same axial coupling direction, preferably parallel to said prevalent extension Y. 
         [0091]    Advantageously, in an insertion configuration of the cup  28  into the main body of the prosthesis  16 , a lower portion  82  of the cup  28 , facing the main body of the prosthesis  16 , results as aligned with a lower base  84  of said first connecting element  76 , said lower base  84  being in a position facing the main body of the prosthesis  16 . 
         [0092]    According to one embodiment of the present invention, the first connecting element  76  presents a disc  56  having on its side surface, at least one ribbing  68  and said second connecting element  78  presents at least one groove  72  having the counter shape of said ribbing  68 . 
         [0093]    According to one embodiment of the present invention, said disc  56  presents four ribbings  68  positioned perpendicular to each other and said second connecting element  78  presents four grooves positioned perpendicular to each other to permit coupling with the ribbings. 
         [0094]    According to one embodiment, the cup  28  comprises a wedge-shaped portion  88  in order to direct the cup  28  in a direction at an incidence with the glenosphere  36  of the attachable scapula. 
         [0095]    Preferably, the area of the section main body of the prosthesis  16  in relation to a plane perpendicular to said prevalent extension Y does not exceed 85% of the total area of a disc  56  associated with the main body of the prosthesis  16  for the connection of the main body of the prosthesis  16  to a coupling portion  60 , such as a cup  28 . 
         [0096]    According to a further embodiment, the first connecting element  76 , for example set parallel to said prevalent extension Y, comprises a pocket  77  and the coupling portion  60 , in the form of a cup  28 , comprises a second connecting element  78  having the counter form of said first connecting element  76 . For example, the second connecting element  78  is equipped with an annular ridge  79  suitable for insertion into said pocket  77  by means of form coupling. 
         [0097]    Preferably, the main body of the prosthesis  16  is made of a metallic material and the cup  28  is made of a polymer material, preferably very high-density polyethylene (UHDPE). Alternatively, the cup  28  can be made of metallic material. Advantageously, the cup  28  presents a pass-through hole  80 , which crosses the body  16  completely in a manner to permit the insertion of a connecting screw  81  between the main body of the prosthesis  16  and the stem  12 . The connecting screw  81  presents a threaded section adapted to engagement with the threaded hole  66  of the stem  12 . This makes it possible to change from the direct configuration to the inverted configuration of the prosthesis  4  by extracting the main body of the prosthesis  16 , previously inserted in the humerus and mounted with a spherical head  24  according to the direct configuration concept, and by inserting a different main body of the prosthesis  16  mounted with a cup  28 . Said main body of the prosthesis  16  is preferably circular and free of any fins  40 , 46 . 
         [0098]    In particular, the main body of the prosthesis  28  mounted with a cup can be anchored to the stem  12  which has remained inserted into the humerus by means of the insertion of the connecting screw. The removal of the main body of the prosthesis  16  from the stem is made easier by the connection between the main body of the prosthesis  16  and the stem  12  by means of a “morse” cone coupling. After the insertion of the main body of the prosthesis in the inverted configuration, in other words, equipped with a first connecting element  76  having a pocket  77 , and after the screwing of the relative connecting screw, it is possible to fasten the cup by means of a click-on action to the main body of the prosthesis by fastening the annular ridge  79  in the pocket  77 . 
         [0099]    According to a further embodiment of the present invention, said prosthesis  4  comprises means of correction  92  for the relative position between the main body of the prosthesis  16  and the coupling portion  60 , adapted to allowing a relative axial sliding action between the disc and the coupling portion  60  along at least one axial direction belonging to a plane perpendicular to said prevalent extension. 
         [0100]    According to one embodiment, the means of correction comprises a first distancer  94  adapted to creating a form coupling with said disc  56 , and a second distancer  96  adapted to creating a form coupling with the coupling portion  60 , said first and second distancers  94 , 96  being able to move along at least one axial direction belonging to a plane perpendicular to said prevalent extension Y of the main body of the prosthesis  16 . 
         [0101]    According to one embodiment, at least one of said first and second distancers  94 , 96  comprises a slide shoe  98  adapted to allowing relative sliding action between said distancers. 
         [0102]    The distancers  94 , 96  can be reciprocally blocked with each other along the slide by means of a continuous type or a discrete type regulation. 
         [0103]    According to a further embodiment, the present invention relates to a shoulder prosthesis  100  adapted to being associated with a glenoid  64 . The shoulder prosthesis  100  comprises a coupling element  104  suitable for attachment to a glenoid  64  to create a kinematic coupling with an attachable humerus and fixing means  108  of the coupling element  104  to the glenoid  64 . 
         [0104]    According to one embodiment, the fixing means  108  comprises an expanding element  110  suitable for insertion into a bone in a non-expanded configuration inside the bone in order to provide at least an undercut adapted to preventing the exit of the coupling element  104  from the bone. 
         [0105]    The expanding element  110  comprises a portion for insertion  114 , suitable for association with the coupling element  104 , on the opposite side of the glenoid, and an expanding portion  116 . 
         [0106]    Preferably, the portion for insertion  114  forms an insertion coupling with the collar  120  of said coupling element  104 . 
         [0107]    The collar  120  and the portion for insertion  114  form a pass-through cavity  122 . 
         [0108]    Preferably, the prosthesis  100  comprises a pin  126  suitable for insertion into said cavity  122  through the collar  120  and the portion for insertion  114 , in a manner so that it penetrates the expanding portion  116  and provokes expansion. 
         [0109]    The expanding portion  116  comprises at least one tang  130  adapted to bending during the change from a non-expanded configuration to an expanded configuration. 
         [0110]    Preferably, the expanding portion  116  comprises a plurality of tangs  130  that radially encircle a lower opening  134  in relation to the cavity  122  or in any case, to the diameter of the pin  126  in such a manner that after the insertion of a pin  126 , this will interact with said tangs  130  provoking the expansion towards the exterior. 
         [0111]    The pin  126  presents a beat head  134  adapted to acting as the end of run during the pin  126  insertion on the coupling element from the opposite side of the expanding element. 
         [0112]    Preferably, the portion for insertion  114  comprises ledges  138  adapted to stabilising the prosthesis during rotation and flexion. Preferably, said ledges are positioned along an external rim of said collar. 
         [0113]    According to one embodiment, the coupling element  104  is a glenosphere  36  adapted to being fixed to a scapula in such a manner that it will couple with a cup  28  operatively connected to a humerus. 
         [0114]    According to a further embodiment, the coupling element  104  is a glenoid prosthesis being concave on the side of the attachable humerus and adapted to being associated with a head of a humerus. 
         [0115]    According to a further embodiment, the shoulder prosthesis  100 , adapted to being associated with a glenoid, comprises a plate  142  adapted to being fixed to a glenoid  64  to create a kinematic coupling with a head of a humerus. The prosthesis  100  comprises a plate element  146  and means for fastening to the glenoid  150 . Preferably, the fastening means  150  comprises at least a catch  154  adapted to fastening onto a rim of the glenoid. 
         [0116]    Preferably, the plate element  146  comprises at least two catches positioned on the opposite sides of the plate element, and even more preferably comprises two pairs of catches positioned on the opposite sides of the plate element. 
         [0117]    According to one embodiment, the plate element  146  comprises a protuberance  156  adapted to being inserted at least partially into the glenoid  64 . 
         [0118]    The plate element  146  presents a coupling hole  158  adapted to allowing the insertion onto the plate element  146  of a coupling interface  160  to a humerus. 
         [0119]    For example, said coupling interface  160  can be a coating plate  164  adapted to covering the plate element  146  on the opposite side from the glenoid, said plate  164  being concave on the side of the attachable humerus. 
         [0120]    The coating plate  164  presents a ridge  168  adapted to being inserted and fixed in said coupling hole  158  of the plate element  146 . 
         [0121]    According to a further embodiment, said coupling interface  160  is a glenosphere  36  that is convex on the side of the attachable humerus. 
         [0122]    According to a further embodiment of the present invention, the shoulder prosthesis  100  comprises a coupling element  104  in the form of a glenosphere  36 , associated with the plate  142  adapted to being fixed to a glenoid  64  to create a kinematic coupling with a head of humerus. The plate  142  is produced in a single piece with an attachment protuberance  170  adapted to being inserted into the glenoid  64 , preferably having at least a flared or bevelled form  172  to prevent relative rotation between the coupling element  104  and the attachable glenoid  64 . Preferably, the fixing protuberance  170  comprises four flared elements  172 ; preferably at least one flared element having a pass-through hole adapted to favouring the osteointegration of the prosthesis. 
         [0123]    Preferably, the prosthesis comprises said cavity  122  adapted to housing the pin  126  to fasten the glenosphere  36  to plate  142  and to the attaching protuberance  170 . The plate  142  preferably presents holes or slots  45  for the possible insertion of fixing pins or to facilitate osteointegration. 
         [0124]    As can be appreciated from the aforesaid description, the prosthesis of the present invention is able to overcome all the drawbacks present in prostheses of prior art. 
         [0125]    In particular, the prosthesis according to the invention is especially non invasive, because of the reduced volume of the main body of the prosthesis. 
         [0126]    The prosthesis according to the present invention provides far easier and optimal results in operations for resuturing the tuberosities of the humeral head (trochite and trochine) with the consequential improvement in articular function recovery. In fact the fins of the main body of the prosthesis create an advantageous support for the tuberosities during the resuturing stage, and as well as making resuturing operations easier for the surgeon, they also ensure correct support for the bone. 
         [0127]    The prosthesis according to the present invention allows to correct certain important geometrical parameters such as anterior and posterior and central-side offset in the head-acromion distance without the need for explanting the prosthesis in question. 
         [0128]    The prosthesis according to the present invention provides the possibility of post-operatory correction following error or for corrective purposes. 
         [0129]    Thanks to the fact that the connecting section of the cup to the main body of the prosthesis is positioned above the anatomic neck of the humerus, this limits further invasive interventions of the prosthesis during any change from direct configuration to inverted configuration. 
         [0130]    The prostheses according to the present invention provide safe attachment to the bone without being particularly invasive, and especially in relation to the glenoid. In fact, the use of an expanding element allows a single hole to be realised thus resulting far less invasive compared to the plurality of holes of the screw systems used in prior art. 
         [0131]    The drilling of a single hole also limits the danger of drilling errors or ill-positioned holes, as well as the risk of bone fracture in proximity to the hole. 
         [0132]    The anchoring system of the prosthesis to the glenoid by means of click-in fins provides the possibility of avoiding hole drilling in the bone; this provides a non-invasive method and yet guarantees very high stability. The elasticity of the fins also permits the correction of positioning errors or in any case, the removal of the prosthesis during implanting without the need for drilling. 
         [0133]    The use of a stem without any ribbing permits the humerus to be inserted without damaging the humerus spongy tissue and furthermore, also allows any correction of the angular orientation of the stem and of the main body of the prosthesis that may be necessary without damaging the spongy tissue. 
         [0134]    Therefore the use of a stem without ribbing contributes towards limiting invasive intervention of the prosthesis. 
         [0135]    Advantageously, the area of the sections of the main body of the prosthesis, such as the fins for example, does not exceed 85% of the total area of the connecting element of the main body of the prosthesis to the coupling portion. In this manner the connecting element, having the form of a disc for example, resists against the penetration of the prosthesis into the humerus to ensure that the connecting element always remains in a position that is not lower than the neck of the humeral head. 
         [0136]    In order to satisfy pertinent and specific necessities, those skilled in the art will be able to apply numerous modifications and variants to the aforesaid prosthesis, while remaining within the scope of the invention as defined in the following claims.