Patent Publication Number: US-2020275938-A1

Title: Milling tool for prosthetic surgery operations

Description:
FIELD OF THE INVENTION 
     The present invention concerns a milling tool for prosthetic surgery operations, able to be used for example to make a bone seating, for example for installing an acetabular hip prosthesis, or a shoulder prosthesis or other, which can be associated with a corresponding handling device. 
     BACKGROUND OF THE INVENTION 
     In general, milling tools are known that can be used during prosthetic surgery operations and are conformed to create coordinated and mating bone seatings suitable for the disposition and implant of corresponding components of surgical prostheses. 
     In particular, milling tools are known that can be used to make the hemispherical seatings, or in any case those with a spherical cap, suitable for installing coordinated acetabular cups of the hip prostheses. 
     These known milling tools generally provide an internally hollow milling cap, with sizes correlated to the bone seating to be made and on which a plurality of through apertures are made provided with cutting and protruding edges, in order to perform a mechanical action of excavation on the bone. 
     In this way, rotating about an axis of rotation, or of milling, and performing a mechanical action of removal of the bone material, this type of milling tools create an impression on the bone of desired size and conformation, substantially corresponding to the milling cap. 
     It is known that the milling tools as above are operatively associated with handling devices, which can be both of the manual and also the automatic type. 
     It is also known that these milling tools have to be subjected to washing and sterilizing operations after each surgery, also with the use of washing and sterilizing machines designed for this purpose. 
     These washing and sterilizing operations naturally entail an increase in the overall costs deriving from the use of these known instruments or tools. 
     Furthermore, it is possible that these washing and sterilizing operations sometimes prove not to be sufficient, so that contaminating agents, such as viruses, bacteria or suchlike, can in any case remain adherent in particular to the milling cap and, of course, can cause problems for the patient. 
     These disadvantages related to the effectiveness of the washing and sterilizing operations are also due to a certain structural complexity with which the milling tools are made. 
     Moreover, the costs of supplying the known milling tools, and also the warehouse stock of these tools, are also usually and undesirably high. 
     Documents EP-A-2.478.852, US-A-2016/0089158 and EP-A-1.764.046 describe milling instruments for orthopedic surgery, in particular for prosthetic surgery, of a known type. 
     Other limitations and disadvantages of conventional solutions and technologies will be clear to a person of skill after reading the remaining part of the present description with reference to the drawings and the description of the embodiments that follow, although it is clear that the description of the state of the art connected to the present description must not be considered an admission that what is described here is already known from the state of the prior art. 
     There is therefore the need to perfect a milling tool for prosthetic surgery operations that can overcome at least one of the disadvantages of the state of the art. 
     One purpose of the present invention is therefore to provide a milling tool for prosthetic surgery operations which allows to drastically reduce the risk of contamination by external agents, such as viruses, bacteria or suchlike, thus allowing to reduce the risks of contamination for a patient. 
     It is also a purpose of the present invention to provide a milling tool which allows to limit further washing and sterilizing operations, to be carried out possibly only on determinate zones or parts of the milling tool, thereby optimizing these washing and sterilizing operations, while eliminating them at least for the operative cutting parts of the milling tool. 
     Another purpose of the present invention is to provide a milling tool for prosthetic surgery operations which is simple and compact in shape, thus allowing production and supply at lower costs compared to what happens with known milling tools. 
     Another purpose of the invention is to provide a milling tool which is simple, effective and allows to perform the milling operations for which it is intended in an optimal and precise manner. 
     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. 
     SUMMARY OF THE INVENTION 
     The present invention is set forth and characterized in the independent claim. The dependent claims describe other characteristics of the invention or variants to the main inventive idea. 
     According to some embodiments, a milling tool for prosthetic surgery operations is provided, which comprises: 
     a support part with a substantially hemispherical shape and made of metal, provided with a cutting part having a plurality of protruding cutting elements; 
     an attachment part made of metal and permanently connected to the support part by welding, 
     an attachment head provided with clamping means which are able to be selectively activated for a stable and releasable connection to the attachment part, the attachment head being able to be connected to a handling device. 
     The attachment part as above is provided with a central connection seating, having a hexagonal shape, in order to allow a selectively releasable connection with the attachment head. 
     According to possible embodiments, at least the cutting part is made of titanium. 
     According to other possible embodiments, the support part is made of titanium. 
     According to still further possible embodiments, the attachment part is made of titanium. 
     In accordance with other embodiments, the milling tool as above is entirely made of titanium. 
     In accordance with other embodiments, the cutting part and the support part are made in a single body with each other. 
     In accordance with other embodiments, the support part as above has a thickness comprised between 0.8 mm and 1.2 mm. 
     In accordance with other embodiments, the attachment part as above has a thickness comprised between 0.9 mm and 1.1 mm. 
     In accordance with other embodiments, the attachment head as above has a hexagonal section shape, mating with the shape of the connection seating 
     In accordance with other embodiments, the clamping means comprise a magnetic element configured to selectively abut against the attachment part in correspondence with the connection seating. 
     In accordance with other embodiments, the attachment part as above comprises a peripheral band of a continuous annular shape and three central spokes substantially equally spaced apart angularly. 
     In accordance with other embodiments, the attachment part is formed by a bar provided with the central connection seating and defining only two diametrically opposite spokes. 
     In accordance with other embodiments, the attachment head as above is provided with a protruding annular bead which abuts against the attachment part. 
     In accordance with other embodiments, the attachment part as above has a perimeter step edge, or crown, of annular shape which couples and abuts with an annular peripheral edge of the support part, where the attachment part is welded to the support part, the perimeter step edge defining an annular portion which narrows the section of the attachment part recessed inside the support part and an annular abutment portion coupled head-wise with an annular peripheral external edge of the support part. 
     In accordance with other embodiments, the attachment part as above has a peripheral smooth edge which couples with the support part, welded and completely recessed flush with an annular peripheral external edge of the support part. 
     In accordance with other embodiments, a milling tool for prosthetic surgery operations is provided, comprising: a support part with a substantially hemispherical shape; an attachment part able to be associated with the support part in order to allow the selectively releasable connection of a handling device; and a cutting part associated at least with the support part and provided with one or more cutting elements. 
     According to some embodiments, at least the cutting part is disposable. 
     Advantageously, therefore, at least the cutting portion, which represents the part that is most operational and most in contact with the bone, is replaced after each use, so that risks or problems of contamination for the patient are eliminated and also, on the cutting parts, washing and sterilizing operations are not necessary. Other parts of the milling tool that can instead be reusable may be subjected to the normal washing and/or sterilizing operations. 
     In some embodiments, at least the disposable cutting part is made of titanium. The use of titanium allows to have a milling tool that is highly biocompatible with humans, preventing post-operative patient rejection problems. 
     In one embodiment, the support part can be permanently associated with the attachment part, and both are disposable. 
     In another embodiment, the support part can be made in a single piece with the attachment part, and both are disposable. 
     In further embodiments, the attachment part can comprise an annular edge permanently associated with an annular edge of the support part. 
     In accordance with some solutions of the invention, the support part can have a thickness comprised between 0.8 mm and 1.2 mm, and in particular of about 1 mm. 
     According to possible solutions, the attachment part can have a thickness comprised between 0.9 mm and 1.1 mm, and in particular of about 1 mm. 
     In some embodiments, the support part can be disposable, and the attachment part can be reusable and comprise means for the releasable connection to the support part. 
     In accordance with possible solutions, the releasable connection means can comprise at least one disk provided on the periphery with seatings able to be associated with teeth protruding internally from the support part; the disc is associated with a clamping element positioned toward the inside of the support part and rotatable with respect to the disc; the clamping element is rotatable into at least a first active clamping position in which it interferes with the teeth, so as to prevent the extraction of the attachment part, and into at least a second inactive position, in which it allows the extraction of the attachment part. 
     The clamping element can comprise a plurality of spokes configured to complete a rotation of a predetermined amplitude; the disc can comprise a plurality of arch-shaped grooves along which the spokes can slide, and which define the amplitude of the rotation of these spokes. 
     The arch-shaped grooves can comprise at least one end-of-travel end, in correspondence with which the spokes are located in correspondence with the teeth. 
     The disc can comprise one or more seatings for positioning pins which are configured to engage in corresponding holes made in the clamping element, in order to stabilize at least the first clamping position. 
     The disc can also comprise through apertures able to allow the rotation of the clamping element from the outside of the attachment part. 
     In some embodiments, only the cutting part can be disposable and is connected in a removable manner to the support part, while the support part and the attachment part can be reusable. 
     The reusable support part can be connected to the attachment part by means of releasable connection means. 
     The cutting part can comprise a plurality of arch-shaped branches, configured to be positioned in corresponding arch-shaped seatings made on the hemispherical surface of the support part. 
     The releasable connection means can comprise a disk able to be associated with a pin provided with a threaded part suitable to be screwed into a corresponding threaded part of the support part. 
     The disc can comprise protruding elements configured to be inserted into corresponding notches made in correspondence with the annular edge of the support part, so as to guarantee a correct positioning of the disc and prevent an accidental rotation thereof. 
     These and other aspects, characteristics and advantages of the present disclosure will be better understood with reference to the following description, drawings and attached claims. The drawings, which are integrated and form part of the present description, show some embodiments of the present invention, and together with the description, are intended to describe the principles of the disclosure. 
     The various aspects and characteristics described in the present description can be applied individually where possible. These individual aspects, for example aspects and characteristics described in the attached dependent claims, can be the object of divisional applications. 
     It is understood that any aspect or characteristic that is discovered, during the patenting process, to be already known, shall not be claimed and shall be the object of a disclaimer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other characteristics of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein: 
         FIG. 1  is a three-dimensional view of a first embodiment of a milling tool according to the present invention; 
         FIG. 2  is a section view of a support part of the milling tool of  FIG. 1 ; 
         FIG. 3  is a three-dimensional and exploded view of a second embodiment of the milling tool according to the invention; 
         FIG. 4  is a three-dimensional and assembled view of the second embodiment of the milling tool of  FIG. 3 ; 
         FIG. 5  is a front view of the second embodiment of the milling tool of  FIG. 4 ; 
         FIG. 6  is a section view of the second embodiment of the milling tool considered according to the section line VI-VI of  FIG. 5 ; 
         FIG. 7  is another three-dimensional view of the second embodiment of the milling tool; 
         FIG. 8  is a three-dimensional and exploded view of a third embodiment of a milling tool according to the present invention; 
         FIG. 9  is a longitudinal section and exploded view of the third embodiment of the milling tool; 
         FIG. 10  is a three-dimensional and assembled view of the third embodiment of the milling tool; 
         FIG. 11  is a lateral view of a milling tool in accordance with embodiments described here; 
         FIG. 12  is a section along the line XII-XII of  FIG. 11 ; 
         FIG. 13  is a lateral view with separated parts of a milling tool in accordance with embodiments described here; 
         FIG. 14  is a section along the line XIII-XIII of  FIG. 13 ; 
         FIG. 15  is a perspective view with separated parts of a milling tool in accordance with embodiments described here; 
         FIG. 16  is a perspective view with separated parts of a milling tool in accordance with further embodiments described here; 
         FIG. 17  is a lateral view of a milling tool in accordance with embodiments described here; 
         FIG. 18  is a section along the line XVIII-XVIII of  FIG. 17 ; 
         FIG. 19  is a lateral view with separated parts of a milling tool in accordance with embodiments described here; 
         FIG. 20  is a section along the line XX-XX of  FIG. 19 ; 
         FIGS. 21-22  are perspective views with separated parts of a milling tool in accordance with embodiments described here. 
     
    
    
     To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications. 
     DETAILED DESCRIPTION OF SOME EMBODIMENTS 
     We will now refer in detail to the various embodiments of the present invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, the characteristics shown or described insomuch as they are part of one embodiment can be adopted on, or in association with, other embodiments to produce another embodiment. It is understood that the present invention shall include all such modifications and variants. 
     Before describing these embodiments, we must also clarify that the present description is not limited in its application to details of the construction and disposition of the components as described in the following description using the attached drawings. The present description can provide other embodiments and can be obtained or executed in various other ways. We must also clarify that the phraseology and terminology used here is for the purposes of description only, and cannot be considered as limitative. 
     Embodiments described using the attached drawings concern a milling tool  20   a ,  20   b ,  20   c ,  20   d ,  20   e ,  20   f  for prosthetic surgery operations, in particular to make concave seatings for the prosthesis implant, for example of the shoulder or hip. The milling tool comprises: 
     a support part  21 ,  32  with a substantially hemispherical shape, that is, in the shape of a hemispherical cap, and made of metal, provided, in a single body, with a cutting part  81 ,  82  having a plurality of protruding cutting elements  22 , or blades; 
     an attachment part  24  made of metal and permanently connected to the support part  21 ,  32  by welding  31 , 
     an attachment head  29  provided with clamping means  84  able to be selectively activated for a stable and releasable connection to the attachment part  24 , the attachment head  29  being able to be connected to a handling device  28 . 
     The attachment part  24  is provided with a central connection seating  27 , having a polygonal shape, in particular quadrangular, in order to allow a selectively releasable connection with the attachment head  29 . 
     The polygonal shape, in particular quadrangular, of the central connection seating  27  is advantageous for an effective transmission of the torque required to rotate the milling tool in question. 
     Advantageously, at least the cutting part is made of titanium. 
     In possible implementations, the support part  21 ,  32  is made of titanium. 
     In other possible implementations, the attachment part  24  is made of titanium. 
     Advantageously, the milling tool  20   a ,  20   b ,  20   c ,  20   d ,  20   e ,  20   f  can be entirely made of titanium. 
     Titanium is particularly advantageous since it is hypoallergenic and biocompatible. 
     Alternatively, one, several or all of the above components can be made of steel. 
     In the embodiments described using  FIGS. 1, 2, 3, 4, 11, 12, 13, 14, 15 and 16 , the cutting part  81 ,  82  and the support part  21 ,  32  are made in a single body with respect to each other. 
     In possible implementations, the support part  21  has a thickness S 2  comprised between 0.8 mm and 1.2 mm. 
     In further possible implementations, the attachment part  24  has a thickness S 1  comprised between 0.9 mm and 1.1 mm. 
     In possible embodiments described using  FIGS. 1, 2, 11, 12, 13, 14, 15 and 16 , the attachment head  29  has a shape with a polygonal section, in particular quadrangular, mating with the shape of the connection seating  27  and the clamping means  84  are provided with an elastic retractable element  87  configured to selectively engage the attachment part  24  in correspondence with the connection seating  27  (see for example  FIG. 12 ). 
     The attachment head  29  can be provided for the connection to a handling device  28 . 
     The elastic retractable element  87 , therefore, acts as an advantageous selective clamping element with the attachment part  24 . This proves to be favorably useful, for example, to prevent undesired detachments or uncoupling between the attachment part  24  and the attachment head  29  associated with the handling device  28 . 
     In possible embodiments, the attachment part  24  comprises a peripheral band  25  with a continuous annular shape and three central spokes, or arms,  37  substantially equally spaced apart angularly (see for example  FIGS. 1 and 15 ). 
     In other possible embodiments, the attachment part  24  is formed by a bar, or crosspiece,  24   a  provided with the central connection seating  27  and defining only two diametrically opposite spokes, or arms,  37  (see for example  FIG. 16 ). 
     In possible embodiments described using  FIGS. 11 to 16 , the attachment head  29  is provided with a protruding annular bead  85  which abuts against the attachment part  24  (see for example  FIG. 12 ). The provision of the protruding annular bead  85  is advantageous since it defines an end-of-travel or safety abutment for the connection between the attachment head  29  and the attachment part  24 , also preventing the rise of situations in which, by exerting thrust and pressure on the handling device  28 , the attachment head  29  is thrust excessively and in an undesired manner beyond the attachment part  24 , toward the inside of the support part  21 , with the obvious risks this would entail. 
     In possible embodiments described using  FIGS. 11 to 15 , the attachment part  24  has a perimeter step edge, or crown,  86  with an annular shape which couples and abuts with an annular peripheral edge  26  of the support part  21 , where the attachment part  24  is welded to the support part  21  by means of the welding  31 , the perimeter step edge  86  defining an annular portion  86   a  which narrowed the section of the attachment part  24  recessed inside the support part  21 , and an annular abutment portion  86   b  coupled head-wise with an annular peripheral external edge  26  of the support part  21 . 
     In other possible embodiments described using  FIG. 16 , the attachment part  24  has a peripheral smooth edge  25   a  which couples with the support part  21  welded and completely recessed, flush with an annular peripheral external edge  26  of the support part  21 . 
     Other embodiments described using  FIGS. 1 to 16  concern milling tools  20   a ,  20   b ,  20   c ,  20   d ,  20   e  for prosthetic surgery operations. 
     The milling tools  20   a ,  20   b ,  20   c ,  20   d ,  20   e  comprise:
         a support part  21 ,  32 ,  57  with a substantially hemispherical shape,   an attachment part  24 ,  33 ,  68  able to be associated with the support part  21 ,  32 ,  57  in order to allow the selectively releasable connection of a handling device  28 ; and   a cutting part  81 ,  82 ,  83  associated at least with the support part  21 ,  32 ,  57  and provided with one or more cutting elements  22 .       

     In accordance with possible embodiments, at least the cutting part  81 ,  82 ,  83  can be disposable, and therefore of the type that can be replaced after each use of the milling tool  20   a ,  20   b  and  20   c . According to one possible solution, at least the cutting part  81 ,  82 ,  83  is made of titanium. 
     The use of this material, also given its relatively low cost, makes it possible to make at least the cutting part  81 ,  82 ,  83  disposable. In addition, the use of titanium ensures the high biocompatibility of this material with the human body, preventing problems of postoperative rejection. 
     In other embodiments, at least the cutting part  81 ,  82 ,  83  can instead be re-used several times, and therefore is not disposable. 
     The cutting part  81 ,  82  and  83  can comprise a plurality of cutting elements  22 , or blades, provided to perform the action of removing the material. 
     In accordance with another embodiment of the present invention, the support part  21 ,  32 ,  57  can have the shape of a hemispherical cap, on which hemispherical cap there is associated the cutting part  81 ,  82 ,  83 . 
     The attachment part  24  comprises at least one central connection seating  27  to allow the selectively releasable connection of the handling device  28 . 
     The handling device  28  can be provided with an attachment head  29  with a shape mating with the central connection seating  27 , in particular for coupling the attachment head  29 , and with a grip  34 . 
     According to variants, the handling device  28  can be provided with coupling portions for coupling into the corresponding coupling elements provided in the attachment part  24 . 
     With reference to the attached drawings, possible embodiments of milling tools are shown, indicated respectively with reference numbers  20   a ,  20   b ,  20   c ,  20   d ,  20   e.    
     In particular, in one embodiment of the present invention ( FIGS. 1, 2 and 11-16 ) the milling tool  20   a ,  20   d ,  20   e  for prosthetic surgery operations, according to the invention, provides that the support part  21 , the cutting part  81 , and the support part  32  are connected to each other in an irremovable manner in order to define as a whole a completely disposable single body. 
     In accordance with one solution ( FIGS. 1, 2 and 11-16 ), the cutting part  81  and the support part  21  can be made in a single body with respect to each other. 
     According to another solution ( FIGS. 1, 2, 11-16 ), the attachment part  24  and the support part  21  with corresponding cutting part  81  are made in one piece, that is, in a single body, or they can be permanently joined together, for example by welding, so as to constitute a single disposable assembly. 
     In accordance with possible solutions of the present invention ( FIGS. 1, 2, 11-16 ), the attachment part  24 , the support part  21  and the cutting part  81  can all be made of titanium, making the whole milling tool  20   a ,  20   d ,  20   e  completely disposable and biocompatible with surgical operations. In possible solutions ( FIGS. 1, 2 and 11-16 ), the support part  21  has a substantially hemispherical shape and is internally hollow. The cutting elements  22 , preferably, can be uniformly distributed on the surface of the support part  21  and through apertures  23  are made in correspondence with them. 
     The cutting elements  22  can have various shapes and have the function of cutting or milling the bone component, while the through apertures  23  allow the removal of bone residues from the cutting or milling zone. 
     According to a possible solution, the cutting elements  22  defined above are made in the thickness of the support part  21  and are each provided with at least one cutting edge in order to allow the removal of the material. 
     The support part  21  is provided with an annular end edge  26  that has a circular shape in which the attachment part  24  is connected, in an irremovable manner. 
     In accordance with one solution ( FIGS. 1, 2 and 11-16 ), the attachment part  24  has a discoid shape and is provided with an annular, or peripheral, band  25  with a shape and size mating with the annular edge  26  of the support part  21 . In particular, it can be provided that the annular band  25  of the attachment part  24  is in contact and integrally attached to the annular edge  26  of the support part. 
     In particular, the annular band  25  of the attachment part  24  can be positioned in part of the hemispherical cavity defined by the support part  21 , that is, it can be at least partly recessed in it. This positioning of the attachment part  24  allows to obtain an increase in the containing rigidity of the support part  21  preventing it from collapsing in correspondence with the annular edge  26 . The attachment part  24  can also comprise spokes, or arms,  37  (see  FIGS. 1, 2  and  11 - 16 ) between which through apertures  30  are made which have a lightening function and allow the removal of the bone residues from the cutting or milling zone. 
     In accordance with some solutions ( FIGS. 1, 2 and 11-16 ), the attachment part  24  has a thickness S 1  comprised between 0.9 mm and 1.1 mm, and preferably of about 1 mm, see  FIG. 2 . These thicknesses are, in fact, sufficient to allow the transmission of the torque exerted by the handling device  28 , preventing damage to the attachment part  24  and also making this part disposable, reducing the waste of material. 
     The support part  21 , in accordance with possible embodiments with reference for example to  FIGS. 1 and 2 , which as stated can have the shape of a hemispherical cap, can have a thickness S 2  comprised between 0.3 mm and 0.8 mm and preferably about 0.5 mm. 
     It has been found that these thickness values S 2  of the support part  21  guarantee a perfect circularity of the annular edge  26  of the support part  21 , even while the milling tool  20   a  is being used. 
     In other embodiments, as stated, the thickness S 2  of the support part  21  can be comprised between 0.8 mm and 1.2 mm and preferably be about 1 mm, particularly when the support part  21  and the corresponding cutting part  81 ,  82  can be reused several times as described above, that is, they are not disposable. 
     The annular band  25  of the attachment part  24  and the annular edge  26  of the support part  21  can be joined, as mentioned, by welding  31 . 
     The milling tool  20   a ,  20   d ,  20   e  therefore has a support part  21  with a cutting part  81  and an attachment part  24  which can be reused several times, that is, not disposable, or can be completely disposable, that is, they are replaced after each use, depending on requirements. 
     In another embodiment of the present invention ( FIGS. 3-7 ) the milling tool  20   b  comprises the support part  32  provided with the cutting part  82  and the attachment part  33 . 
     Also in this case, by way of example, the cutting part  82  and the support part  32  can be made in a single body with respect to each other. 
     In particular, it can be provided that the cutting part  82  is formed by the cutting elements  22 , variously positioned and made on the support part  32 . 
     In this case, the support part  32  and the cutting part  82  are disposable, while the attachment part  33  can be reusable and therefore can be selectively connected to the support part  32  in a removable manner. 
     The support part  32  has the shape of a hemispherical cap and therefore comprises the annular edge  26  that defines a circular aperture  54  into which the attachment part  33  is inserted. 
     The support part  32  and the attachment part  33  are provided with connection means, selectively releasable, in order to allow the selective connection and the subsequent separation, for example after use, of the support part  32  with respect to the attachment part  33 . 
     The support part  32  internally comprises, that is, in the concavity defined by the hemispherical cap, a plurality of teeth  35  protruding radially and configured to engage with corresponding seatings  36  made in a disk  38  of the attachment part  33 . 
     The disc  38  comprises a protruding annular edge  55  on which the annular edge  26  of the support part  32  rests in abutment. 
     The teeth  35  are preferably made in the proximity of the annular edge  26  of the support part  32 . 
     The teeth  35  can be made by plastic deformation of the support part  32  in order to generate a protrusion toward the inside of the hemispherical cap. 
     For example, it is possible to provide three teeth  35 , disposed equally distanced one from the other in the proximity of the annular edge  26  of the support part  32 . 
     The disc  38 , see in particular  FIG. 6 , comprises a cylindrical support  39  located, during use, in the cavity of the spherical cap of the support part  32 . 
     On the cylindrical support  39  there is positioned a rotatable clamping element  40 , provided for this purpose with a through hole  41  in which the cylindrical support  39  is inserted. 
     This cylindrical support  39  can be threaded at the protruding end, so as to engage with a closing ring  42 , which is internally threaded. 
     Once the clamping element  40  has been inserted on the cylindrical support  39 , the ring  42  is screwed to the cylindrical support  39 , so as to keep the clamping element  40  in the correct position and allow it to rotate with respect to the cylindrical support  39  and therefore to the disk  38 . 
     The clamping element  40  comprises a plurality of spokes  43  protruding radially, and having an extension such as to reach, in a clamping position, in correspondence with the seatings  36  made on the disc  38 . 
     Each of the spokes  43  has the function of preventing the attachment part  33  from separating from the support part  32 , once the seatings  36  of the disc  38  have been correctly positioned on the corresponding teeth  35 , as shown in  FIG. 6 . 
     With particular reference to  FIG. 7 , it can be observed that on the lateral wall  44  of the disc  38  arch-shaped grooves  45  are made, along which the spokes  43 , integral with the clamping element  40 , can rotate. 
     The clamping element  40  is therefore substantially rotatable with respect to an axis L, in order to make a rotation in the direction R, in one sense or the other, of an amplitude defined by the extension of the arch-shaped grooves  45 . 
     Each of the arch-shaped grooves  45  comprises two end-of-travel ends  46  and  47  which define two limit positions of the spokes  43  of the clamping element  40 : one active position in which each spoke  43  is located in correspondence with the seating  36  of the disc  38 , and one inactive position, in which the clamping element  40  is inoperative and allows reciprocal separation of the attachment part  33  with respect to the support part  32 . 
     The disc  38  also comprises spokes  48  between which through apertures  49  are made. 
     The through apertures  49  allow to interact from the outside with the clamping element  40 , in order to be able to rotate it at least into the active position and at least into the inactive position. 
     In the spokes  48 , see the section of  FIG. 6 , there are made seatings  56  for housing a series of pins  50  for positioning the clamping element  40 . 
     The pins  50  are provided with a spherical or hemispherical head  51  suitable to engage, for example in a snap-in manner, in corresponding holes  52  made on the spokes  43  of the clamping element  40 , in particular in the position in which the spokes  43  are located in correspondence with the seatings  36  of the disc  38 , therefore in the active clamping position. 
     The pins  50  allow to firmly keep the clamping element  40  in position, at least when it is in the active clamping position. 
     Further holes  53  could also be made on the clamping element  40 , suitable to allow its engagement with a rotation tool or device, or suchlike. 
     Looking for example at  FIG. 5 , it can be assumed that, from the outside of the milling tool  20   b , a suitable tool can be inserted through the through apertures  49  and engage in the holes  53  to allow the rotation R of the clamping element  40 . 
     Substantially, therefore, the disc  38  of the attachment part  33  can already be supplied with the clamping element  40  mounted and rotatable in one sense or the other with respect to the disc  38 , as a function of the extension of the arch-shaped grooves  45 . The disc  38  and the clamping element  40  are kept adjacent and in position thanks to the ring  42 . 
     The attachment part  33  with the disc  38 , clamping element  40  and ring  42  appears, for example, as in  FIG. 7 , so that the seatings  36  are not covered by the spokes  43  of the clamping element  40 . 
     The attachment part  33  is then inserted into the support part  32  through the aperture  54 , and the seatings  36  of the disk  38  are positioned on the teeth  35 . 
     The insertion of the attachment part  33  is completed when the annular edge  55  arrives in abutment on the annular edge  26  of the support part  32  and the seatings  36  are completely positioned on the teeth  35 . 
     Once the positioning is completed, as for example in  FIG. 4 , the clamping element  40  is rotated in the direction R,  FIG. 7 , so that the spokes  43  move in correspondence with the seatings  36 , so that the teeth  35  will be positioned between the seatings  36  and the spokes  43 , see for example the section of  FIG. 6 : the clamping element  40 , by means of the spokes  43 , is in abutment on the teeth  35 , preventing the extraction of the attachment part  33 . 
     Therefore, the clamping element  40 , in this active or clamping position, interferes with the teeth  35 , in particular by means of the spokes  43 . 
     The attachment part  33 , in this position, is firmly connected to the support part  32  and cannot therefore be disconnected from it. The correct positioning of the attachment part  33  on the support part  32  is also guaranteed by the engagement of the holes  52  of the spokes  43  on the pins  50 . 
     The disc  38  provided with a rotatable clamping element  40  therefore represent a non-limiting example of possible means for the releasable connection of the attachment part  33  to the support part  32 . 
     In order to separate the attachment part  33  from the support part  32 , the clamping element  40  will be rotated in the opposite sense to the clamping rotation R, so that the spokes  43  are no longer abutting on the tooth  35  of the support part  32 . 
     In this embodiment of the milling tool  20   b , therefore, the support part  32  and the cutting part  82  are disposable, while the attachment part  33 , comprising the disc  38  and the clamping element  40 , is reusable. 
       FIG. 8 ,  FIG. 9  and  FIG. 10  show another embodiment of the milling tool  20   c.    
     The milling tool  20   c  comprises the support part  57  in the form of a hemispherical cap configured to house the cutting part  83 . 
     Protruding cutting elements, such as for example the cutting elements  22  of  FIG. 1  or  FIG. 3 , can be positioned, or made on the cutting part  83 , in the proximity of the through apertures  23 . 
     In this embodiment of the milling tool  20   c , only the cutting part  83  is disposable, while the other parts of the milling tool  20   c  are reusable. 
     The cutting part  83  is formed by a plurality of branches  60 , with an arched shape, configured to be positioned in corresponding arch-shaped seatings  64  made on the hemispherical surface of the support part  57 . 
     The branches  60  are joined at a common end  62  and are provided, at their free ends, with an edge  63 , folded toward the inside of the milling tool  20   c , in particular in the radial direction. 
     It is possible to provide that the cutting part  83  is formed for example by four branches  60 , reciprocally equidistant from each other. 
     The seatings  64 , configured to accommodate the branches  60  to size, can preferably be provided with through apertures  65 , located during use in correspondence with the internal side of the cutting elements  22 . The through apertures  65  allow to discharge the material which is removed by the cutting elements  22  into the concavity of the spherical cap. 
     Each of these seatings  64  comprises an edge  61 , inside which the edge  63  of the corresponding branch  60  is positioned, so that the cutting part  83  is correctly positioned on the support part  57 , as for example in  FIG. 10 . 
     For this purpose, in the positioning of the cutting part  83  on the support part  57 , the branches  60  widen slightly and elastically, until the edges  63  are correctly positioned under the edges  61  of the seatings  64 . 
     The support part  57  is also provided, on the annular edge  26 , with one or more notches  66 , for example with an arched shape, configured to engage with elements  67  protruding from an attachment part  68 . 
     The attachment part  68  comprises a disk  69 , on the annular edge  70  of which the protruding elements  67  are made. 
     The protruding elements  67  are inserted in the notches  66  of the support part  57 , so as to guarantee the correct positioning of the attachment part  68  in the support part  57 , and in order to prevent their reciprocal rotation. 
     The disc  69  of the attachment part  68  comprises spokes  71  between which through apertures  72  are made, joined in a central part  73 . 
     The central part  73  is provided with a through hole  74 , suitable to allow the passage of the stem  76  of a pin  75  and to house the head  77  to size. 
     The head  77  can have a truncated cone shape, and the through hole  74  can consequently be provided with a corresponding truncated cone shape. 
     The stem  76  of the pin  75  comprises, at the opposite end with respect to that of the head  77 , a threaded part  78 , configured to be screwed with a corresponding threaded part  79  made inside the support part  57 , in particular in a top portion  80  of the support part  57 . 
     The attachment part  68  also comprises a spacer element  59  provided with a through hole  58  and suitable to rest on one side on the central part  73  of the disk  69  and, on the other side, on the top portion  80  of the support part  57 . 
     When assembling the milling tool  20   c , firstly, preferably, the cutting part  83  is positioned on the support part  57 , therefore with the branches  60  correctly positioned in the seatings  64 . 
     The attachment part  68  is then assembled and connected to the support part  57 . 
     The stem  76  of the pin  75  is inserted in the through hole  74  of the disk  69  and then into the through hole  58  of the spacer element  59 , so that the threaded part  78  exits from the spacer element  59  and can engage with the threaded part  79  of the top portion  80  of the support part  57 . 
     The protruding elements  67  of the disc  69  are naturally inserted into the corresponding notches  66 . 
     Furthermore, the annular edge  70  of the disc  69  abuts at least against the annular edge  26  of the support part  57 . 
     The milling tool  20   c  will then appear, in its assembled and operational configuration, as in  FIG. 10 . 
     The disk  69  that can be associated with the pin  75  which can be screwed into the support part  57  therefore represents a non-limiting example of possible means for the releasable connection of the attachment part  68  to the support part  57 . 
     To the disk  69  of the attachment part  68  there can be connected a corresponding handling device, provided with suitable elements for releasable connection, for example, to the spokes  71  of the disk  69 . 
     The milling tools  20   a ,  20   b ,  20   c ,  20   d ,  20   e  can therefore have at least the cutting parts  81 ,  82 ,  83  of the disposable type, or which can be reused, therefore not disposable. 
     In the case of the milling tool  20   a ,  20   d ,  20   e  the support part  21  and the attachment part  24  can also be disposable, or reusable, therefore not disposable. In the case of the milling tool  20   b , in addition to the cutting part  82 , the support part  32  can also be disposable. In the case of the milling tool  20   c , only the cutting part  83  can be disposable. 
     The present milling tool  20   a ,  20   b ,  20   c ,  20   d ,  20   e , or at least the support parts  21 ,  32 ,  57  and the cutting parts  81 ,  82 ,  83 , are preferably made of titanium so as to be biocompatible with the body and prevent rejection problems for the patient. In particular, the titanium used can be grade “0” or grade “1”. 
     Furthermore, titanium guarantees high mechanical resistance in relation to weight, which can be advantageously contained. 
     It is clear that modifications and/or additions of parts may be made to the milling tool  20   a ,  20   b ,  20   c ,  20   d ,  20   e  for prosthetic surgery operations as described heretofore, without departing from the field and scope of the present invention. 
     It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of milling tool  20   a ,  20   b ,  20   c ,  20   d ,  20   e  for prosthetic surgery operations, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby. 
     Embodiments shown in  FIGS. 17-22  concern a milling tool  20   f  for prosthetic surgery operations, in particular to make concave seatings for prosthesis implants, for example of the shoulder or hip. 
     The milling tool  20   f  has characteristics that can be combined with any of the characteristics whatsoever described with reference to the milling tools  20   a ,  20   b ,  20   c ,  20   d ,  20   e  with the exception that the attachment part  24  of the milling tool  20   f  is provided with a central connection seating  27 , with a hexagonal shape in order to allow a selectively releasable connection with a respective attachment head  29  with a hexagonal-shaped section mating with the shape of the connection seating  27 . 
     In particular, the attachment head  29  is provided with a connection portion  29   a  projecting from the protruding annular bead  85  and having the hexagonal-shaped section as above. 
     The hexagonal shape of the central connection seating  27  and of the attachment head  29  allows to distribute the connection force between the attachment head  29  and the support part  21  in a more homogeneous manner. With the same transmitted force, the hexagonal shape allows to reduce the sizes of the connection seating  27 . 
     In accordance with some embodiments, the clamping means  84  of the attachment head  29  comprise a magnetic element  89  configured to selectively abut with the attachment part  24  in correspondence with the connection seating  27 . 
     In accordance with some embodiments, shown in  FIG. 18  and  FIG. 20 , the attachment head  29  is provided with a throat  88 , made on the protruding annular bead  85  and circumscribed to the connection portion  29   a , in which the magnetic element  89  is positioned. 
     The magnetic element  89  has an annular shape substantially mating with the shape of the throat  88 . 
     Advantageously, the presence of the magnetic element  89  allows to transmit a uniform connection force on the attachment part  24 , and not localized precisely as in the case of the elastic retractable element  87 . In fact, the annular shape of the magnetic element  89  allows to act on the entire perimeter zone around the connection seating  27 . 
     Although the magnetic element  89  is only described with reference to the milling tool  20   f , it can be adapted for any milling tool  20   a ,  20   b ,  20   c ,  20   d ,  20   e  as previously described. 
     In the following claims, the sole purpose of the references in brackets is to facilitate reading: they must not be considered as restrictive factors with regard to the field of protection claimed in the specific claims.