So-called anatomical prostheses of the shoulder are known, which reproduce naturally the gleno-humeral anatomy, and comprise a glenoid insert anchored to the scapula by means of a support attached to the glenoid cavity; the insert articulates with a spherical element attached to the top of the humerus by means of a supporting body and an attachment rod inserted into the humerus itself.
So-called inverse prostheses of the shoulder are also known, which reproduce the gleno-humeral anatomy in an inverse manner, and which, unlike anatomical prostheses, comprise a spherical element attached to the scapula and a mating humeral cup or insert attached to the upper end of the humerus.
In order to anchor the support to the glenoid cavity it is usually provided to insert into the bone seating a rod substantially passing through the axis of the support, and to use two or more screws that attach to the bone seating a platelet solid with the rod. The screws are normally disposed on the periphery of the rod, and are attached on the scapula substantially along the same direction as the rod.
Due to particular bone pathologies, or the anatomical morphology of the scapula, or the lack of a sufficient bone thickness, known attachment solutions are not always able to guarantee a correct and enduring attachment of the support to the glenoid cavity. This may entail possible mechanical yielding of the prosthetic part constrained to the glenoid cavity, and consequent problems, obviously, for the patient concerning the progressive loosening and possible reciprocal detachment of the components of the prostheses.
Moreover, even in substantially normal bone conditions, it may be difficult for the surgeon, given the extremely limited space available, to intervene with medical instruments in order to screw the traditional screws inside the bone of the scapula, and this may cause a non-optimum attachment of the support.
EP-A1-1.488.764, in the name of the Applicant, discloses an inverse prosthesis able to be disassembled and comprising a double-conical pin element able to be used for mounting a spherical head onto a glenoid insert attachable on the glenoid cavity of the shoulder.
EP-A1-1.437.099 discloses a device for protecting and covering a femoral neck, which comprises a hollow sleeve able to be mounted on the reshaped femoral neck, and a rigid platelet or flange which extends outwards the sleeve and has a plurality of through holes for the passage of a relative fastener fixable to the bone.
However, these documents do not provide a solution for improving the attachment conditions of a prosthesis to a glenoid seating of a shoulder, more particularly for guaranteeing a correct and enduring attachment.
One purpose of the present invention is therefore to achieve a prosthesis of the shoulder, both of the anatomical or inverse type, suitable to guarantee an optimum attachment thereof to the scapula, substantially in any pathological and anatomical condition of the patient, or operating condition of the surgeon.
Another purpose of the present invention is to resolve the problems of the state of the art, in a simple and economical manner, without in any way affecting the correct functionality of the prosthesis.
Another purpose is to allow to modify, also over time, the conditions of attachment, for example as the consequence of a progressive bone degeneration, without intervening on the normal components of the prosthesis.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.