Abstract:
A prosthesis and method for a ball and socket joint. The prosthesis includes a first component including an anchoring shank and a metaphyseal portion. The metaphyseal portion includes a first articular surface configured to move in translation relative to the anchoring shank. An intermediate component includes a first articular surface configured to engage with the first articular surface on the metaphyseal portion, and a second articular surface configured to engage with the ball and socket joint.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/FR2007/000670, with an international filing date of Apr. 20, 2007, entitled Shoulder or Hip Prosthesis and Method for Setting Same (Prothese D&#39;Epaule Ou De Hanche Et Methode De Pose D&#39;Une Telle Prothese), which claims priority to French application No. 0603559, filed Apr. 21, 2006, the disclosures of which are all hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a shoulder or hip prosthesis. 
       BACKGROUND OF THE INVENTION 
       [0003]    Within the field of shoulder prostheses, it is known, for example from FR-A-2 841 768, to use an intermediary component having two convex articulation surfaces designed to co-operate with a concave articulation surface belonging to the humeral component of the prosthesis and a concave glenoid articulation surface respectively. This type of prosthesis gives overall satisfaction, particularly since the distribution of the instantaneous centres of rotation of the articular surfaces in contact enables the point of application of the effort exerted by the deltoid during the abduction movement to be externalised. However, in some implantation configurations, the external part of the humeral component or the humerus risks coming into contact with the acromion, which may be irritating, or even painful, for the patient. 
         [0004]    Similar problems may arise with a shoulder prosthesis that has a humeral component with a convex articulation surface, the intermediate component thus having a corresponding concave articulation surface. Problems of the same type may arise with a known hip prosthesis. 
         [0005]    These are the drawbacks that the invention more particularly aims to remedy by proposing a new shoulder prosthesis in which the abduction effort exerted by the deltoid can be optimised, without risking interaction between the humerus or humeral component and the acromion at the end of the abduction movement. The invention also proposes a hip prosthesis. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    For this purpose, the invention relates to a shoulder or hip prosthesis which comprises a humeral or femoral component having an articulation surface and an intermediate component having a first and second articulation surface designed to co-operate with the articulation surface of the humeral or femoral component respectively and with a concave articulation surface which is natural or belongs to a glenoid or cotyloid component, the humeral component comprising a first part designed to be anchored in the humerus or in the femur. This prosthesis is characterised in that the articulation surface of the humeral or femoral component is formed by a second part of this component which is movable in translation in relation to the first part in a moving-away/approaching direction between the first part and the articulation surface of the humeral or femoral component. 
         [0007]    In the case of a shoulder prosthesis, the possibility of relative movement in translation between the first and second parts of the humeral component makes it possible to vary, during the abduction movement, the lever arm between the point of application of the effort due to the deltoid and the instantaneous centre of rotation of the surfaces in contact located on the humeral component and on the intermediate component respectively. This lever arm can therefore be thinner at the end of abduction, which limits the risks of interference of the humerus or humeral component with the acromion. In the case of a hip prosthesis, similar advantages are obtained on elevating the patient&#39;s leg. 
         [0008]    One embodiment is directed to a prosthesis for a ball and socket joint. The prosthesis includes a first component including an anchoring shank and a metaphyseal portion. The metaphyseal portion includes a first articular surface configured to move in translation relative to the anchoring shank. An intermediate component includes a first articular surface configured to engage with the first articular surface on the metaphyseal portion, and a second articular surface configured to engage with the ball and socket joint. 
         [0009]    In one embodiment, a second component is provided that is adapted for implantation in a socket portion of the ball and socket joint. The second component includes a first articular surface adapted to engage with the second articular surface on the intermediate component. The second articular surface of the intermediate component is preferably unconstrained relative to the first articular surface on the second component. 
         [0010]    In one embodiment the first articular surface on the metaphyseal portion includes a rod telescopically engaged with the metaphyseal portion. The rod preferably includes a non-circular cross-section. The first articular surface of the metaphyseal portion preferably moves in translation relative to the anchoring shaft in one degree of freedom. 
         [0011]    The distance between the first articular surface and the metaphyseal portion decreases with abduction of the ball and socket joint. The center of rotation of the first articular surface on the metaphyseal portion is typically located inside the ball and socket joint. The lever arm of the ball and socket joint typically decreases in abduction. In one embodiment, the prosthesis includes end stops on the intermediate component and the metaphyseal portion limiting abduction of the ball and socket joint. 
         [0012]    In one embodiment, the first articular surface on the metaphyseal portion is concave, and at least the first articular surface on the intermediate component is convex. In another embodiment, the first articular surface on the metaphyseal portion is convex, and at least the first articular surface on the intermediate component is concave. In another embodiment, the ball and socket joint is a shoulder joint and the anchoring shank is adapted to connect to a medullary cavity of a humerus. 
         [0013]    Another embodiment is directed to a prosthesis for a shoulder joint. A first component includes an anchoring shank adapted to connect to a medullary cavity of a humerus, and a metaphyseal portion. A first articular surface coupled to the metaphyseal portion is configured to move in translation relative to the anchoring shank. An intermediate component includes a first articular surface configured to engage with the first articular surface on the metaphyseal portion, and a second articular surface configured to engage with a glenoid cavity of the shoulder joint. In one embodiment, a second component adapted for implantation in a glenoid cavity of the shoulder joint is provided. The second component includes a first articular surface adapted to engage with the second articular surface on the intermediate component. 
         [0014]    The present invention is also directed to a method of fitting a prosthesis in a shoulder joint. The method includes connecting an anchoring shaft of a first component to a medullary cavity of a humerus. A first articular surface is coupled to a metaphyseal portion of the first component to move in translation relative to the anchoring shank. An intermediate component is located between a glenoid cavity of the shoulder joint and the first articular surface. A first articular surface on the intermediate component is engaged with the first articular surface on the metaphyseal portion. A second articular surface on the intermediate component is engaged with the glenoid cavity of the shoulder joint. 
         [0015]    In one embodiment, the method includes implanting a second component in the glenoid cavity and engaging a first articular surface on the second component with the second articular surface on the intermediate component. In another embodiment, a distance between the first articular surface and the metaphyseal portion is reduced during abduction of the shoulder joint. 
         [0016]    According to the advantageous but not obligatory features of the invention, such a prosthesis may incorporate one or more additional. 
         [0017]    For example, the second part of the humeral or femoral component has an assembly rod on the first part, such rod forming part of a telescopic structure to guide the translation movement between the first and second parts of this component. According to a first embodiment, the rod may be engaged in a guide bore formed by or connected to the first part. According to another embodiment, the rod is hollow and adapted to receive, with the possibility of sliding, a finger which projects in relation to the first part. Furthermore, the rod and the supplementary part of the telescopic structure advantageously have a non-circular cross-section. 
         [0018]    End stops are provided to the relative translation movement of the first and second parts of the humeral component in an approaching direction between the first part and the intermediate component. 
         [0019]    According to a first type of prosthesis according to the invention, the articulation surface of the humeral or femoral component is concave, whereas the first and second articulation surfaces of the intermediate component are convex. According to another type of prosthesis according to the invention, the articulation surface of the humeral or femoral component is convex, whereas the first and second articulation surfaces of the intermediate component are concave and convex respectively. 
         [0020]    The invention also relates to a method of fitting a shoulder or hip prosthesis as previously described and, more precisely, a method of fitting a prosthesis that comprises a humeral or femoral component, of which a first part is designed to be anchored in the humerus or the femur and which has an articulation surface and an intermediate component that have a first and second articulation surface designed to co-operate with the articulation surface of the humeral or femoral component respectively and with a concave articulation surface which is natural or belongs to a glenoid or cotyloid component, this method comprising a stage consisting in fitting a second part of the humeral or femoral component, which forms its articulation surface, in a sliding manner onto the first part. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0021]    Further features and advantages of the invention will emerge more clearly from the following description of three embodiments of a prosthesis according to its principle, given purely by way of example and made with reference to the accompanying drawings in which: 
           [0022]      FIG. 1  is a sectional view of a prosthesis in according with an embodiment of the present invention shown in a patient&#39;s arm at the start of an abduction movement. 
           [0023]      FIG. 2  is a sectional view of the prosthesis of  FIG. 1  shown at the end of an abduction. 
           [0024]      FIG. 3  is a partial section of the prosthesis of  FIG. 1  along line III-III in  FIG. 2 . 
           [0025]      FIG. 4  is a section similar of an alternate prosthesis according to an embodiment of the present invention. 
           [0026]      FIG. 5  is a section similar of another alternate prosthesis according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]    The prosthesis P shown in  FIGS. 1 to 3  comprises a humeral component  1  which includes a part  11  designed to be anchored in the medullary canal of the humerus H of the joint to be fitted with the prosthesis P. Part  11  comprises an anchoring shank  111  and a metaphyseal part  112  in which a tube  113  with an oval internal section is fixed, as can be seen more clearly in  FIG. 3 . The component  1  also comprises a pad  12  which defines a concave surface S 1  and is fitted, opposite the surface S 1 , with a rod  121  with an oval section that is complementary to the inner section of the tube  113 . 
         [0028]    In the mounted configuration of the prosthesis, the concavity of the surface S 1  is facing towards the glenoid G of the shoulder. 
         [0029]    The prosthesis P also comprises a glenoid component  2  anchored in the glenoid G and defining a concave surface S 2  whose concavity is turned towards the exterior of the glenoid. Between the components  1  and  2 , an intermediate component  3  is inserted which defines an external convex surface S′ 2  which is substantially complementary to surface S 2 , as well as a surface S′ 1  which is also convex and substantially complementary to surface S 1 . The surface S′ 2  of the intermediate component  3  is preferably unconstrained relative to the surface S 2 . 
         [0030]    In the embodiment described, the surfaces S 1 , S 2 , S′ 1  and S′ 2  are sections of a sphere, the radius R 1  common to surfaces S 1  and S′ 1  being smaller than the radius R 2  common to surfaces S 2  and S′ 2 . However, surfaces S 1 , S 2 , S′ 1  and S′ 2  are not necessarily sections of a sphere. 
         [0031]    The relative position of surfaces S 1 , S 2 , S′ 1  and S′ 2  is in accordance with the technical disclosure of FR-A-2 841 768. Note that C 1  is the instantaneous centre of rotation of surface S 1  in relation to surface S′ 1 . It is a centre common to the spheres defining the surfaces S 1  and S′ 1 . The geometry of elements  2 ,  3  and  12  is such that the centre C 1  is situated in the glenoid bone G, that is, in a median position in relation to the anatomical centre of rotation of the shoulder before operation. 
         [0032]    Note also that C 2  is the instantaneous centre of rotation between surfaces S 2  and S′ 2 . In this embodiment, it is the centre common to the spheres defining these surfaces. It is situated beyond the surface S′ 1  in relation to surface S 2 , which is in accordance with the technical disclosure of FR-A-2 841 768. Commonly assign U.S. Pat. No. 7,033,396 and U.S. Patent Publication Nos. 2005/0288791 and 2005/0165490 are hereby incorporated by reference. 
         [0033]    Note that H 1  is the point of the humerus H at which the resultant force of the effort F D  of the deltoid is applied during the abduction movement of the humerus. 
         [0034]    Note that Z-Z′ is an axis that is globally parallel to the vertebral column of the patient when standing and passes through the centre C 1 . Note that d 1  is the distance, measured perpendicularly to the axis Z-Z′, between point H 1  and the centre C 1 . This distance d 1  constitutes the lever arm of the effort F D  that causes the movement of the surface S 1  of the pad  12  on the surface S′ 1  during abduction. The longer this lever arm, the easier it is for the patient to lift his arm as a result of the effort F D  exerted by the deltoid, which is particularly great if the rotator cuff, which holds down the humeral head, is deficient. 
         [0035]    In order to prevent point H 1  or a region of the humerus close to this point from impinging on the acromion A at the end of the abduction movement, the rod  121  slides inside the tube  113 , which makes it possible to vary the distance d 2  between the surface S 1  and the bottom of the bore  114  made in the part  112  in order to receive the tube  113 , this distance d 2  being measured parallel to the central longitudinal axis X 121  of the rod  121 . The axis X 121  is also the central axis of the tube  113 . 
         [0036]    Thus, the pad  12  is movable in translation away from/approaching part  11 , in the direction of the double arrow T and parallel to axis X 121 . The translation movement of the pad  12  in relation to the part  13  corresponds to an approach of part  11 , on the one hand, and of the elements  12  and  3  resting on each other, on the other, during abduction. By contrast, when the patient lowers his arm, elements  12  and  3 , on the one hand, and  11 , on the other, move away from each other. 
         [0037]    In other words, the rod  121  can slide inside the tube  113 , which forms a bore that guides the rod in translation, so that the distance d 2  is variable, as a comparison between  FIGS. 1 and 2  shows. The variable nature of distance d 2  also results in the distance d 1  having a variable nature. In the configuration shown in  FIG. 2 , the distance d 1  is shorter than it is in the configuration shown in  FIG. 1 . This is not problematic since, when the humerus is near the configuration shown in  FIG. 2  or in this configuration at the end of the abduction movement, the resultant F D  of the effort due to the deltoid forms an angle α, with the axis Z-Z′, which is substantially greater than in the configuration shown in  FIG. 1 , so that this resultant force then tends to draw the top of the prosthesis towards the glenoid G, which limits the risks of luxation (e.g., displacement or misalignment of a joint). Thus, at the end of the abduction movement, the distance between the humerus H and the acromion A is not zero, although less than it was at the start in the configuration shown in  FIG. 1 . 
         [0038]    Thus, the telescopic structure formed by the rod  121  and the tube  113  allows the lever arm d 1  of the resultant F D  to be adapted to the position of the humerus H during the abduction movement. At the start of the movement shown in  FIG. 1 , this distance or lever arm d 1  is maximum, which facilitates abduction, whereas, at the end of the movement, this distance or lever arm is minimum, which prevents interference with the acromion. 
         [0039]    As shown more clearly in  FIG. 3 , the rod  121  and the tube  113  have complementary non-circular sections, which enables the angular position of the pad  12  to be restrained about the axis X 121 . The non-circular cross-sections constrain movement of the rod  121  in the tube  113  to one degree of freedom. In an alternate embodiment, the rod  121  and tube  113  have circular cross-sections, permitting rotation of the pad  12  relative to the metaphyseal part  112 . In this alternate embodiment, the pad  12  is permitted to move in two degrees of freedom. 
         [0040]    Furthermore, a plug  13 , inserted in the humerus H around the part of the tube  113  which projects in relation to the metaphyseal part  112 , comes in abutment against a corresponding portion  31  of the component  3  at the end of the abduction movement in order to limit the approach of parts  11  and  12 . Parts  13  and  31  thus form a stop to the approaching movement of parts  11  and  12  during abduction. 
         [0041]    In a variant, the end  113   a  of the tube  113  opposite the shank  111  can come to a stop against the rear face  122  of the pad  12 , that is the face of this pad opposite the surface S 1 . The abutment of the end  113   a  against the face  122  thus forms a stop to the approaching movement of parts  11  and  12 . 
         [0042]    According to an optional feature of the invention, the edge  32  of the component  3  can receive the plug  13  in sliding bearing, the shape of this edge being compatible with an approach of the surface S 1  and part  11  during the adduction movement, as shown in  FIGS. 1 and 2 . 
         [0043]    According to a feature of the invention which is not shown, a stop can also be provided, for example in the vicinity of the free end of the rod  121 , to limit the distancing of parts  11  and  12  and thus prevent the extraction of the rod  121  in relation to the tube  113  in the configuration shown in  FIG. 1 . 
         [0044]    In the second embodiment of the invention shown in  FIG. 4 , elements similar to those of the first embodiment bear the same reference numerals. This embodiment differs from the preceding one substantially in that the rod  121  of the pad  12  is hollow and forms a bore to receive a finger  113 ′ which projects in relation to part  11 , in the direction of the pad  12 . As before, a telescopic structure is formed which allows the lever arm to be adjusted between the point H 1  where the resultant F D  of the effort due to the deltoid is exerted and the instantaneous centre of rotation C 1  of the concave surface S 1  formed by the pad  12  in relation to the corresponding convex surface S′ 1  formed by the intermediate component  3 . 
         [0045]    As in the first embodiment, the elements  121  and  113 ′ that make up the telescopic structure have a non-circular section. In this embodiment, they can have a polygonal section. 
         [0046]    In the third embodiment of the invention shown in  FIG. 5 , elements similar to those shown in the first embodiment bear the same reference numerals. This embodiment differs from the preceding one in that the articulation surface S 1  of the humeral component is formed by a section of a sphere  123  mounted, using a Morse-taper type assembly, on a rod  121  similar to that of the first embodiment. The intermediate component  3  defines a concave articulation surface S′ 1 , in the form of a section of a sphere substantially complementary to the surface S 1 , as well as a convex articulation surface S′ 2  complementary to an articulation surface S 2  defined by the glenoid component  2  of the prosthesis P. 
         [0047]    The rod  121  is mounted sliding in a tube  113  and can move within this tube, parallel to its longitudinal axis X 121 . 
         [0048]    Once assembled, parts  121  and  123  together form a pad  12  which is movable in translation in relation to part  11  of the prosthesis P anchored in the humerus H. The telescopic structure formed between elements  121  and  113  enables the lever arm to be adjusted between point H 1  where the resultant F D  of the effort due to the deltoid is exerted and the instantaneous centre of rotation C 1  of the surface S 1  in relation to the surface S′ 1 . 
         [0049]    As before, elements  121  and  123  can have a non-circular section. 
         [0050]    When a prosthesis according to one of the previously-described embodiments is to be fitted, its part  11  is anchored in the humerus before the pad  12  is fitted onto this part  11 , with the possibility of sliding, by engaging its rod  121  in the corresponding tube  113  for the first embodiment or the finger  113 ′ in the rod  121  for the second embodiment. The pad  12  may be fitted onto part  11  before or after surface S 1  of this pad has been placed in contact with surface S′ 1  of component  3 . 
         [0051]    In a variant, the pad  11  can be fitted onto part  12  before this part is anchored in the humerus. 
         [0052]    According to a variant of the invention, not shown, the glenoid component  2  can be omitted and the surface S′ 2  of component  3  rests against a natural glenoid surface. 
         [0053]    The invention has been shown installed in shoulder prostheses. It is also applicable to hip prostheses of which the femoral component can have two parts that are movable in translation in relation to each other in a moving-away/approaching direction between the part designed to be anchored in the femur and its articulation surface. 
         [0054]    Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the inventions. The upper and lower limits of these smaller ranges which may independently be included in the smaller ranges is also encompassed within the inventions, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the inventions. 
         [0055]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which these inventions belong. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present inventions, the preferred methods and materials are now described. All patents and publications mentioned herein, including those cited in the Background of the application, are hereby incorporated by reference to disclose and described the methods and/or materials in connection with which the publications are cited. 
         [0056]    The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present inventions are not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed. 
         [0057]    Other embodiments of the invention are possible. Although the description above contains many specificities, these should not be construed as limiting the scope of the invention, but as merely providing illustrations of some of the presently preferred embodiments of this invention. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the inventions. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed inventions. Thus, it is intended that the scope of at least some of the present inventions herein disclosed should not be limited by the particular disclosed embodiments described above. 
         [0058]    Thus the scope of this invention should be determined by the appended claims and their legal equivalents. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims.