Patent Publication Number: US-2023146587-A1

Title: Prosthetic device for temporomandibular joint and corresponding prosthetic assembly

Description:
FIELD OF THE INVENTION 
     The present invention concerns a prosthetic device for temporomandibular joint and a corresponding prosthetic assembly comprising said prosthetic device and a guide device for the preparation of a suitable bone seating. 
     The prosthetic device as above is particularly suitable for applications in patients with non-extensive joint pathologies, for example in the case of osteoarthrosis/osteoarthritis, condylar resorption, benign neoplasms, or in the case where previous surgeries have failed. 
     This solution can also be adopted as a first surgery in a large number of patients, where the traditional path would involve other attempts at functional arthroplasty, normally destined to fail. 
     BACKGROUND OF THE INVENTION 
     It is known that the reconstruction of the temporomandibular joint is a problem due to the complex role it plays inside the stomatognathic system. 
     It plays an essential role in chewing, in speech, in supporting respiratory exchanges and in swallowing, and is a secondary growth center for the jaw during pre-puberty. Furthermore, the temporomandibular joint is subjected to repeated loading/unloading cycles more than any other joint in the body. 
     Given the complexity of the anatomy and biomechanics of said joint, surgery to solve problems and related pathologies is complex and currently very invasive. 
     The temporomandibular joint articulates the mandibular bone with the temporal bone, in particular it connects the mandibular condyle with the glenoid fossa of the temporal bone. 
     Prosthetic devices for the temporomandibular joint therefore comprise two components: a condyle prosthesis and a glenoid fossa prosthesis respectively associated, during use, with the mandibular condyle and the glenoid fossa of the temporal bone. Both components are made according to the specific needs of the patient and his/her anatomical morphology. 
     Before they are applied, it is necessary to perform osteotomies to prepare the condyle and the glenoid fossa to accommodate the respective prostheses. For this purpose, guide devices can be provided able to facilitate the operation of bone resection performed by the surgeon. Furthermore, it is necessary to use traditional surgical burrs that cause damage, even very extensive, to the affected bone tissues and those surrounding them. 
     The prosthetic devices currently used are very bulky and require a very large installation space between the mandibular branch and the base of the skull, which is necessary to be able to insert the fossa prosthesis and the condyle prosthesis. Because of this, often the osteotomy of the condyle, and if necessary also of the glenoid fossa, must necessarily be very large and invasive. 
     This limits the indications for the implantation of the joint prosthesis only to very severe cases. 
     The sizes of current prostheses also make the surgical procedure very invasive, which provides a pre-auricular incision, for the insertion of the glenoid fossa prosthesis, and a retro-submandibular incision, for the insertion of the branch/condyle prosthesis. 
     The invasiveness of current prostheses and the surgical procedure for their installation lead to long hospitalization times and possible complications for the patient. 
     There is therefore a need to perfect a prosthetic device for application to the temporomandibular joint and corresponding prosthetic assembly that can overcome at least one of the disadvantages of the state of the art. 
     In particular, one purpose of the present invention is to provide a prosthetic device for temporomandibular joint the implantation of which requires a limited osteotomy of the condyle and possibly of the glenoid fossa. 
     Another purpose of the present invention is to provide a prosthetic device for temporomandibular joint that allows to extend the surgical indications, and therefore applicability, to a greater number of patients compared with the use of traditional prostheses. 
     Another purpose of the present invention is to provide a prosthetic device for temporomandibular joint that consists of a limited number of components so as to simplify and speed up its installation. 
     Another purpose of the present invention is to provide a prosthetic assembly for temporomandibular joint that is advantageously customized/individualized and patient-specific, and that allows to simplify and at the same time make the corresponding surgical technique less invasive. 
     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 claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea. 
     In accordance with the above purposes, a prosthetic device for temporomandibular joint, which overcomes the limits of the state of the art and eliminates the defects present therein, comprises a first prosthetic component, able to be associated with a mandibular condyle of a patient, and a coordinated second prosthetic component, able to be associated with a respective glenoid fossa of the patient. 
     The first prosthetic component is configured to cooperate with the second prosthetic component to define the temporomandibular joint and comprises a convex portion, configured to cooperate with the second prosthetic component to define the temporomandibular j oint. 
     According to one aspect of the present invention, the first prosthetic component comprises at least one anchoring element projecting from, and attached at least to, the concave portion as above, since the anchoring element is contained in the concave portion and has a main extension along a latero-medial axis. The anchoring element is configured to be inserted into a mating anchoring seating present, or provided, on the mandibular condyle as above. Furthermore, the coupling seating is at least partly open along the latero-medial axis. 
     In this way, the first prosthetic component can be easily inserted in a direction parallel to the latero-medial axis as above, allowing to limit the removal of bone material from the patient to a minimum, and at the same time allows to greatly simplify the surgical practice. In addition, the minimal invasiveness of the surgical approach and of the resection of the condyle allows to extend the surgical indications and therefore a considerably greater applicability compared with the use of traditional prostheses. 
     In some embodiments, the first prosthetic component comprises a concave portion, defining a coupling seating having a shape mating with the shape of the mandibular condyle. The concave portion is therefore configured to cooperate with the second prosthetic component to define the temporomandibular joint. The convex portion as above is opposite the concave portion. 
     In accordance with some embodiments, a guide device is provided to prepare an anchoring seating for the prosthetic device as above, in particular to position the first prosthetic component. 
     The guide device comprises a central body able to be positioned against at least the upper lateral part of a mandibular condylar branch, and a guide wall associated at the upper part with the central body and having the profile of the osteotomy to be performed on the condyle. 
     According to a characteristic aspect of the present invention, the guide device has a groove which extends vertically from the guide wall toward the central body. Furthermore, the groove is open at the upper part and is through in a direction parallel to the latero-medial axis. 
     Some embodiments of the present invention comprise a prosthetic assembly, advantageously customized and patient-specific, provided with the prosthetic device and the corresponding guide device as above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects, characteristics and advantages 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 perspective view of a prosthetic device for temporomandibular joint in accordance with the embodiment described here; 
       -  FIG.  2    is a perspective view of the first prosthetic component of the prosthetic device of  FIG.  1   ; 
       -  FIG.  3    is a perspective view of the second prosthetic component of the prosthetic device of  FIG.  1   ; 
       -  FIG.  4    is a lateral view of the anchoring element of  FIG.  2   ; 
       -  FIG.  5    is a perspective view showing the coupling of the first prosthetic component with the mandibular condyle; 
       -  FIG.  6    is an external lateral plan view of the first prosthetic component during use; 
       -  FIG.  7    is an internal lateral plan view of the first prosthetic component during use; 
       -  FIG.  8    is a front view of the first prosthetic component during use; 
       -  FIG.  9    is a perspective view of a guide device in accordance with the embodiment described here; 
       -  FIGS.  10 - 11    are perspective views that show the functioning of the guide device of  FIG.  9   . 
     
    
    
     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 possible embodiments of the 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, one or more characteristics shown or described insomuch as they are part of one embodiment can be varied or 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. 
     Some embodiments described here concern a prosthetic device  10  for temporomandibular joint ( FIGS.  1 - 7   ) and a guide device  35  ( FIGS.  9 - 11   ) required to prepare a specific anchoring seating  113  ( FIG.  11   ) for the prosthetic device  10 , as will be described in more detail below. Other embodiments also include a prosthetic assembly, advantageously customized/individualized and patient-specific, which comprises the prosthetic device  10  and the guide device  35 . 
     Here and hereafter, the terms proximal, distal, anterior, posterior, medial, lateral are defined by their standard use for a person of skill in the art to indicate a particular aspect or orientation of a bone, an anatomical part, a prosthetic device and its components, or other elements according to the relative disposition of the natural anatomy of the human and/or animal body, or directional terms of reference with respect thereto. 
     With particular reference to  FIG.  1   , the temporomandibular joint articulates the mandibular bone  111  with the temporal bone  110 , in particular it connects a mandibular condyle ( FIG.  5   ), hereafter condyle,  112  with a respective glenoid fossa of the temporal bone  110 , hereafter fossa. 
     The prosthetic device  10  therefore comprises a first prosthetic component  11 , able to be associated with a condyle  112  of a patient, and a coordinated second prosthetic component  12 , able to be associated with a respective fossa of the patient. In particular, the condyle  112  is suitably shaped to house the first prosthetic component  11 , as will be described in more detail below. 
     The first prosthetic component  11  comprises a concave portion  13 , defining a coupling seating  14  having a shape mating with the shape of the previously shaped condyle  112 . 
     The first component  11  comprises a convex portion  15 , opposite the concave portion  13  and configured to couple with the second prosthetic component  12  to define the temporomandibular j oint. 
     The first prosthetic component  11  is provided with at least one anchoring element  16  projecting from, and attached at least to, the concave portion  13 . The anchoring element  16  has an overall size such as to be substantially contained inside the concave portion  13 . 
     The anchoring element  16  has a main extension along a latero-medial axis X. In particular, the term latero-medial here and hereafter is intended to indicate a direction that goes from a lateral zone toward a zone located in the proximity of the median plane of the patient’s body. 
     The anchoring element  16  is configured to be inserted in a mating anchoring seating  113  ( FIG.  11   ) made on the condyle  112  of the patient which is shaped following the profile of the guide device  35  which will be described below. 
     The coupling seating  14  is at least partly open along the latero-medial axis X so as to allow, in one possible application, the coupling of the first prosthetic component  11  with the condyle  112  in a direction parallel to the latero-medial axis, which runs from the outside to the inside ( FIG.  2   ,  FIG.  5    and  FIGS.  7 - 8   ). In the embodiment described here, the coupling seating  14  has a shape substantially mating with the articulating upper portion of the condyle  112 . 
     The particular geometry of the prosthetic device  10  and in particular of the first prosthetic component  11  provided with the anchoring element  16  with latero-medial insertion allows to limit the removal of bone material from the patient to a minimum, and at the same time allows to greatly simplify the surgical practice which becomes less invasive thanks to the need to only create one access route, with a pre-aural incision. 
     According to some embodiments described here, with particular reference to  FIGS.  2 ,  5  and  8   , the first prosthetic component  11  also comprises an external lateral portion  17  configured to couple laterally with the condyle  112 . The external lateral portion  17  has an extension such as to allow a lateral abutment during the positioning of the first prosthetic component  11  along the lateromedial axis X, and to allow a stabilization thereof. 
     The first prosthetic component  11  can be configured as a condyle prosthesis configured to at least partly cover the condyle  112  of the patient. This first prosthetic component  11  is conceived as a covering prosthesis with the purpose of preserving the original bone portion of the condyle  112  as much as possible. Favorably, this condylar prosthesis can be used in the case of non-extensive pathologies, which in fact are those with the greatest incidence. 
     In particular, the first prosthetic component  11  is configured to cover the lateral surface of the condyle  112 , the upper surface - the one that normally articulates with the fossa - and possibly also the posterior and anterior surfaces. Obviously, given the mode of insertion of the first prosthetic component  11 , that is, in a direction parallel to the latero-medial axis X, it is not provided to cover the medial portion of the condyle  112  ( FIGS.  7 - 8   ). 
     With particular reference to  FIG.  2   , the first prosthetic component  11  comprises a shell  18  having an upper wall  19  and an external lateral wall  20  disposed inclined with respect to the upper wall  19 . The inclination of the external lateral wall  20  is essentially given by the anatomy of the mandibular branch  114  of the patient. In the example embodiment described here, this inclination is about 90 °, or slightly smaller. 
     The upper wall  19  has a shape such as to define, at the bottom, the concave portion  13  and, at the upper part, the convex portion  15  ( FIG.  2    and  FIG.  7   ). 
     The upper wall  19  is configured to at least partly cover the condyle leaving an internal medial part thereof substantially free. For this purpose, the shell  18  is open, as well as at the bottom, also along the latero-medial axis X in a zone opposite the external lateral wall  20  and terminal of the upper wall  19  ( FIGS.  7 - 8   ). 
     The external lateral wall  20  has a main development along the mandibular branch  114  and is substantially parallel or subparallel to the median plane of the body. 
     Optionally, the external lateral wall  20  can be provided with at least one through hole  21  for the insertion of an attachment element, for example a screw  22  (see for example  FIG.  2    and  FIGS.  5 - 6   ). The screw  22  allows to obtain a primary stabilization of the first prosthetic component  11  at least during the period of osseointegration thereof with the mandibular condyle of the patient. The size and length of the screw  22  vary according to the conformation and sizes of the condyle. 
     In the embodiment described here, with particular reference to  FIG.  2    and  FIG.  7   , the shell  18  also comprises a pair of opposite walls, respectively an anterior wall  23  and a posterior wall  24 , configured to at least partly wrap the condyle anteriorly and posteriorly in order to guarantee greater stability. The anterior  23  and posterior wall  24  are connected at the upper part to the upper wall  19 , respectively on one side and the other of the latter, and laterally to the external lateral wall  20 . 
     Although the upper wall  19 , the external lateral wall  20  and the anterior  23  and posterior walls  24  have been described as distinct and separate elements, it goes without saying that they can be made in a single body so that one can be an extension of the other, according to the geometry and the reciprocal disposition just described. 
     According to some embodiments described here, the anchoring element  16  is configured as a lamella  25  attached at the upper part to the upper wall  19 , on the side of the concave portion  13 , and laterally to the external lateral wall  20 . However, it is not excluded that the lamella  25  can be attached only to the upper part  19 . The lamella  25  can be conformed as a wall, a septum, a suitably shaped ridge projecting from the upper wall  19 . 
     In particular, the lamella  25  projects in a direction substantially orthogonal to the upper wall  19  ( FIG.  2    and  FIG.  7   ). The lamella  25  divides the coupling seating  14  substantially into two parts, each of which is able to rest on a respective portion of condyle  112  located on the sides of the anchoring seating  113  ( FIG.  11   ). 
     The lamella  25  has a longitudinal extension, or length, L ( FIG.  4   ) in the direction of the latero-medial axis X substantially equal to the extension of the upper wall  19  in the same direction ( FIG.  2   ). 
     However, it is not excluded that the lamella  25  may also have a shorter length L. Evidently, the greater the length L, the greater the useful surface in contact with the bone of the condyle for a better integration and stabilization. 
     The lamella  25  has a height H ( FIG.  4   ) proportional to the depth of the anchoring seating  113  ( FIG.  11   ) provided on the condyle  112 . For example, the height H can have a minimum value of 4 mm, or be larger. 
     The lamella  25  has a thickness W1 ( FIG.  7   ) much smaller than the length L. For example, the thickness W1 can vary between about 1 mm and about 4 mm. Favorably, the thickness W1 is comprised between about 2 mm and about 3 mm. 
     Advantageously, the lamella  25  is configured to promote the primary stabilization of the prosthesis, the neoformation of cancellous bone and the osseointegration with the cortical bone of the condyle  112 . 
     In particular, the lamella  25  can have a substantially rectangular shape and be provided with macro grooves and micro grooves to promote the neoformation of cancellous bone and the osseointegration with the cortical bone of the condyle  112 . 
     In one embodiment,  FIGS.  2  and  4   , the lamella  25  is provided with a plurality of teeth  26  suitably inter-spaced to define the macro grooves as above, in such a way as to promote, during use, bone growth inside them in order to guarantee a greater stability of the first prosthetic component  11 . For example, the lamella  25   and the teeth  26  define a comb-like conformation. 
     The lamella  25  can also be provided with a chamfer  29  able to facilitate the latero-medial insertion of the first prosthetic component  11  in the anchoring seating  113  on the condyle  112 . In this case,  FIG.  4   , the shape of the lamella  25  can be a rectangle trapezoid in which the inclined side that defines the chamfer  29  can also have more than one inclination or be defined by a curve. 
     According to some embodiments, the first prosthetic component  11  is made with a biocompatible material, for example titanium or an alloy thereof, or other possible known or unknown biocompatible materials. Advantageously, the articulating surface of this first prosthetic component  11  can be treated so that it is as smooth as possible, for example mirror-like, in order to reduce frictions during joint movement to a minimum. 
     In particular, the lamella  25  can be made of titanium, and its surface can be favorably treated to increase the contact surface with the bone and promote osseointegration with the latter. For example, the surface of the lamella  25  can be treated with a sandblasting process with hydroxyapatite and acid passivation (RBM). In possible embodiments, the lamella  25  can, alternatively and for the purposes of osseointegration, have an at least partly porous or lattice-shaped structure, which for example reproduces the trabecular structure of the bone, possibly associated with a portion of compact material. 
     The best osseointegration is also promoted by the piezo surgical preparation of the surgical site, which provides a preservation of the bone tissues and much less damage than a traditional cutter for the preparation of an osteotomy site. 
     In some embodiments, the first prosthetic component  11  can be made with a Selective Laser Melting (SLM) process, or with a Direct Metal Laser Sintering (DMSL) process, or again by means of Electron Beam Melting (EBM) technique, or in general by means of a suitable “additive manufacturing” or 3D printing technique, based on the specific anatomical needs of the patient. Such techniques, for example, are advantageous in the event the first prosthetic component  11 , and in particular the lamella  25 , at least partly have an at least partly porous or lattice-shaped structure, for example trabecular, possibly associated with a portion of compact material. 
     According to the embodiment shown in  FIG.  1    and  FIG.  3   , the second prosthetic component  12  can be configured as a fossa prosthesis configured to cover the glenoid fossa of the patient. 
     The second prosthetic component  12  comprises an articulating portion  30  able to cooperate, during use, with the convex portion  15  of the first prosthetic component  11 , and a zygomatic portion  31  which, during use, is able to cover the zygomatic arch of the patient. 
     The articulating portion  30  has a convex articulating surface  32  having a shape mating with the convex portion  15 . 
     The upper part of the articulating portion  30 , the one which, during use, is positioned in contact with the glenoid fossa of the patient, has a shape that traces the pre-existing, or surgically shaped, bone surface of the fossa. 
     The second prosthetic component  12  can be stabilized to the temporal bone by means of screws  34 . For this purpose, both the articulating portion, in an outermost part thereof, and also the zygomatic portion  31  can provide through holes  33  for the screws  34 . In the example described here, the zygomatic portion  31  is stabilized with three screws  34 . 
     According to some embodiments, the second prosthetic component  12  is made with a biocompatible material, for example ultra-high molecular weight polyethylene (UHMWPE), or other possible known and unknown biocompatible materials. 
     In accordance with the embodiment described in  FIGS.  9 - 11   , the guide device, in this specific case a surgical template,  35  comprises a central body  36  able to wrap at least the upper lateral part of the condylar branch, and a guide wall  37  attached at the upper part to the central body  36  and having the profile of the osteotomy to be performed on the condyle  112  of the patient. In particular, the central body  36  can be suitable to also partly wrap the posterior and anterior surfaces of the condyle  112  for a better positioning. 
     The surgical template  35  has a central vertical groove  38  open at the upper part which divides the guide wall  37  into a first guide branch  37   a  and a second guide branch  37   b . 
     In the example described here, the guide wall  37  has a substantially curved profile, however, it is not excluded that the guide wall  37  may have a squared profile, or other profile suitable to make the least invasive osteotomy possible. 
     The vertical groove  38  is through in a direction parallel to the latero-medial axis X in order to allow the surgeon to perform a vertical osteotomy in order to prepare the anchoring seating  113  in the condyle  112  of the patient. 
     The guide groove  38  can also extend, in part, in the central body  36 . 
     The groove  38  is open at the upper part and has a terminal part, or bottom,  39  able to act as an abutment for the surgical blade during the preparation of the anchoring seating  113  ( FIG.  11   ). 
     The groove  38  has a depth D substantially equal to the height H of the lamella  25  of the first prosthetic component  11 , and a width W2 smaller than or equal to the thickness W1 of the lamella  25  ( FIG.  11   ). Furthermore, it is possible to provide a slight tapering that goes from the upper aperture of the groove  38  to the terminal part  39  thereof. 
     The surgical template  35  is provided with at least one calibrated hole  40  prepared through the central body  36 . The calibrated hole  40  allows to prepare a corresponding hole in the condyle  112  of the patient to position a screw which serves to stabilize the surgical template  35  and subsequently to attach the first prosthetic component  11 . In possible implementations, the condylar prosthetic component, that is, the condyle  112 , can be modeled and shaped in its external lateral part in order to house more attachment screws and, for this purpose, this can also provide the use of a dedicated template. 
     Operatively, after the identification of the part of the condyle  112  to be removed, the surgical template  35 , having profiles suitably shaped according to the anatomical needs of the patient, is positioned on the condylar branch  114  and attached to it with a screw (not shown) ( FIG.  10   ). Subsequently, a first osteotomy is performed following the profile of the guide wall  37  and then a second vertical osteotomy is performed along the groove  38  to create the anchoring seating  113  ( FIG.  11   ) to house the lamella  25 . Favorably, the osteotomies are performed using a blade with piezoelectric handle, guaranteeing maximum cutting precision. 
     It is clear that modifications and/or additions of parts may be made to the prosthetic device for temporomandibular joint and corresponding prosthetic assembly as described heretofore, without departing from the field and scope of the present invention as defined by the claims. 
     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 prosthetic device for temporomandibular joint and corresponding prosthetic assembly, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby. 
     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.