AU2016349948B2

AU2016349948B2 - An improved temporomandibular joint (TMJ) prosthesis

Info

Publication number: AU2016349948B2
Application number: AU2016349948A
Authority: AU
Inventors: George Dimitroulis
Original assignee: Tmj Orthopaedics Pty Ltd
Current assignee: Tmj Orthopaedics Pty Ltd
Priority date: 2015-11-04
Filing date: 2016-11-04
Publication date: 2017-11-23
Anticipated expiration: 2036-11-04
Also published as: WO2017075664A1

Abstract

There is provided a prosthesis for the replacement of a temporomandibular joint having a mandible and a temporal bone. The prosthesis comprises a condylar component for fastening to the mandible, the condylar component including a condylar head having a convex spherical articular surface; and a fossa component for fastening to the temporal bone, the fossa component having a concave spherical articular surface defining a socket being operable to engage the condylar head in an articulating manner wherein the concave spherical articular surface traverses through approximately 180°. The fossa component may also be anteroposteriorly symmetric.

Description

An Improved Temporomandibular Joint (TMJ) Prosthesis

Field of the Invention [1] The present invention relates to an improved temporomandibular joint (TMJ) prosthesis.

Background of the Invention [2] The temporomandibular joint is the only ginglymoarthrodial joint in the body. It acts as both a hinge and a sliding joint and can move up to 2000 times each day, meaning wear resistance is a large factor in a replacement design (Guarda-Nardini, Manfredini, & Ferronato, 2007).

[3] The jaw is operated by the muscles of mastication, which are the masseter, temporalis, lateral pterygoid and medial pterygoid. The masseter, temporalis and medial pterygoid function to elevate the mandible; the medial pterygoid also operates with the lateral pterygoid to protrude the mandible.

[4] The digastrics (openers) run along the underside of the jaw and act to depress the mandible (Choi et al, 2005). The muscles of mastication are composed of different subregions: the masseter has a deep and superficial part; the temporalis is composed of the anterior, posterior and deep part; the lateral pterygoid has a superior and inferior part (Koolstra et al, 1988).

[5] Temporomandibular disorders (TMD) are a broad category of conditions that affect the TMJ or the muscles of mastication, which cause pain and reduced function of the jaw (LeResche, 1997).

[6] TMD can be broken down into three main categories: pain and dysfunction of the masticatory muscles; internal derangement of the TMJ, typically caused by displacement or slipping of the articular disc; and TMJ inflammation or degeneration, often caused by osteoarthritis. (Green, 2001).

[7] TMD prevalence within the population ranges from 16-59% (Carlson & LeResche, 1995). The prevalence rate of TMD in women is significantly higher than in males, with women being approximately twice as likely to suffer pain in the temporomandibular region (LeResche, 1997; Kamisaka et al, 2000). TMJ dysfunction is a condition that is most common among adults, with the prevalence declining for the population over 50 years old (LeResche, 1997).

[8] There are a variety of treatment methods available, with surgical intervention and total joint replacement reserved for end-stage TMJ disease (Giannakopoulos et al, 2009).

[9] Total or partial joint replacements have been used since the 1960s and became more popular during the 1980s. Unlike other implant systems there is little uniformity or regulation in the design of the implants. Materials for the TMJ implant varied from stainless steel, cobalt-chrome alloys, fibreglass to Teflon coatings. All these total joint replacements feature a condylar and a fossa component but the designs and methods for fixation vary. Most of these designs disappeared or ceased to be used due to several issues including: bone resorption; cancellous bone growth around the implant; low placement success rates; poor wear characteristics; and material choices that caused metal sensitivity and large cell growth in patients (van Loon et al, 1995).

[10] In the last 20 years, the range of total TMJ implant systems has shrunk. Designs byTechmedica (later TMJ Concepts) and Lorenz began circa 1991 and are very similar in design and material.

[11] Since 2000 a significant number of organisations and implants have had their approval withdrawn by the US Food and Drug Administration (FDA) due to a lack of clinical trials and engineering tests conducted on the implants. The FDA reported that the total TMJ implants needed to be rigorously tested for fatigue since many implants had lifetimes of less than three years. The tested implants had inadequate wear testing, no analysis for wear debris, no analysis for wear of the natural condyle and no examination of wear on implants removed from patients (GAO, 2007). The most common fixation technique to connect the mandibular implant to the bone is the use of orthopaedic screws (Ramos et al, 2009).

[12] Implant loosening, due to poor screw placement and excessive loads, can lead to implant failure through screw loosening or atrophy and micromotion at the bone implant interface, which can hamper bone integration. The best implant fixation techniques and optimum placement of screws still remains unclear as designs vary in screw orientation (Ramos et al, 2009) [13] Current designs still face a range of problems including: pathological responses from wear debris; fracture from metal fatigue and screw loosening; and difficulty in fitting implants to skull (Quinn, 2000). It has also been noted that the lifetime of the implant is insufficient considering the young age of many patients. This means that an improvement to wear rates and more comprehensive fatigue testing is required (van Loon et al, 1995; van Loon et al, 1999).

[14] Figure 1 shows a prior art TMJ prosthesis, referred to herein as Dl, as is taught in laid open US patent publication US5549680 A.

[15] Dl comprises an artificial condyle component for fastening to the mandible and an artificial mandibular fossa component for fastening to the temporal bone. The artificial condyle component includes a condylar head having an articular surface, the articular surface having a substantially spherical articular surface of a first spherical radius forming a substantial portion of the articular surface. Furthermore, the artificial mandibular fossa component has a spherical articular surface of a second spherical radius greater than said first spherical radius.

[16] As such, the artificial mandibular fossa component is operable to engage the condylar head in an articulating manner.

[17] Furthermore, Figure 2, shows a further TMJ prosthesis in accordance with the prior art referred to herein as D2. Specifically, the prosthesis of D2 is an earlier TMJ prosthesis design of the present inventor published by way of Australian Innovation patent publication AU2012100561, published on 2012-06-14.

[18] Since this earlier design, the inventor has conducted computer aided 3-D modelling and analysis and cadaver studies to arrive at the improved TMJ prosthesis as is provided herein.

[19] Specifically, the inventor worked with the Engineering School at the University of Melbourne wherein Finite Element Analysis (FEA) Modelling was performed to fit the earlier D2 design into a virtually reconstructed human which concluded with a report entitled "Design of a novel jaw-joint replacement", the entire contents of which are herein incorporated by reference.

[20] The FEA model included a three-dimensional computer simulation incorporating the mandible, glenoid fossa, cartilage and articular discs as well as the earlier D2 TMJ prosthesis. Muscle forces calculated from the model of the masticatory system were used as boundary conditions in the model.

[21] Tests were run under loading conditions for normal chewing forces and for maximum bite forces. The effect of screw placement and implant malalignment was also assessed. The results were also compared to those obtained during simulations of the D1 prosthesis. The data sets obtained from FEA were reaction loads on the mandible and implant prosthesis condyle, as well as stresses in the natural joint cartilage and articular discs. Implant prosthesis contact stress, loading stress and strain was also recorded.

[22] Comparisons of the D2 TMJ prosthesis to the D1 TMJ prosthesis found several areas of improvement. Specifically, for normal chewing loads the D2 TMJ prosthesis had lower stresses in the neck of the condylar component; 20.4MPa compared to 51.5MPa. Furthermore the D2 TMJ also had a better load distribution across the screws in the condylar component and a lower peak stress in the screws; 338MPa to 376MPa.

[23] However, the design of the D1 TMJ prosthesis proved superior in reducing contact stress at the joint, where the contact stress was 72MPa compared to 85MPa in the D2 TMJ prosthesis. This was due to the design of the condylar head in the D1 TMJ prosthesis being more compatible with the fossa prosthesis. Such indicated that a key area of improvement in the D1 TMJ prosthesis may lie in the shape of the head of the condylar component.

[24] As such, the inventor further conducted cadaver studies wherein 3-D prints of the improved computer simulated model design were inserted into 6 human cadaver heads. During these cadaver the inventor experimentally discovered improvements to the fossa component which are provided herein in embodiments. For example, one embodiment of the present TMJ prosthesis was found to provide for greater range of motion allowing the opening of the jaw by about 40° whereas prior art TMJ prosthesis allowed only about 33°.

[25] Furthermore, the inventor discovered several disadvantages with prior art TMJ prosthesis through their utilisation in practice.

[26] For example, the Inventor discovered that the condylar head could unexpectedly be misplaced during surgery thereby damaging the tympanic plate of the middle ear causing deafness.

[27] Furthermore, the Inventor discovered found that it is quite difficult to locate the condylar head in the fossa component during surgery using prior art TMJ prosthesis.

[28] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

[29] Other aspects of the invention are also disclosed.

Summary [30] As such, with the foregoing in mind, in accordance with one aspect, there is provided a prosthesis for the replacement of a temporomandibular joint having a mandible and a temporal bone comprising: a condylar component for fastening to the mandible, the condylar component including a condylar head having a convex spherical articular surface; a fossa component for fastening to the temporal bone, the fossa component having a concave spherical articular surface defining a socket being operable to engage the condylar head in an articulating manner wherein the concave spherical articular surface traverses through approximately 180°.

[31] The deepened socket of the fossa component having the articular surface traversing through approximately 180° reduces the likelihood of tympanic plate damage from the condylar head during surgery wherein the deepened socket and the more vertical posterior edge defined thereby substantially prevents or reduces the likelihood of the condyle ahead slipping past the fossa component during installation and damaging the tympanic plate causing deafness. Furthermore, the more vertical interior edge of the socket defined by the deepened socket further provides anterior dislocation protection in use. Furthermore, the deepened socket assists the surgeon incorrectly locating the condylar head within the socket during surgery which is often times out of you given the angle of installation wherein, whereas with prior art TMJ prosthesis it was difficult for the surgeon to ascertain whether the condylar head was correctly located within the socket of the fossa component, the deepened socket of the present fossa component allows the surgeon to feel when the condylar head it correctly placed.

[32] The diameter of the condylar head may be approximately 75% than that of the socket.

[33] The condylar head may comprise a diameter of between 5-15 mm.

[34] The condylar head may comprise a diameter of about 11 mm.

[35] The condylar component may comprise an inferior portion and a condylar neck transitioning between the inferior portion and the condylar head.

[36] The inferior portion may be about 2mm thick.

[37] The condylar head may define a lateral extremity and wherein the inferior portion may define a lateral face and wherein the lateral extremity extends laterally beyond the lateral face.

[38] The condylar head may define a medial extremity and wherein the inferior portion may define a medial face and wherein the medial extremity extends medially beyond the medial face.

[39] The condylar head may define an apex and wherein the apex coincides mediolaterally approximately with the medial face.

[40] The condylar head may define a lateral and medial extremities and wherein the inferior portion may define lateral and medial faces and wherein the medial extremity extends medially beyond the medial face to a medial extent and wherein the lateral extremity extends laterally beyond lateral face to a lateral extent and wherein the medial extent is greater than the lateral extent.

[41] The fossa component may be anteroposteriorly symmetric.

[42] The fossa component includes a superior lateral flange and a superior surface medially adjacent the superior lateral flange and wherein the superior lateral flange is poised at about 100° with respect to the superior surface.

[43] The superior lateral flange may define bone fixation screwholes therein.

[44] The bone fixation screwholes therein are arranged in superior and inferior rows and are anteroposteriorly adjacently staggered.

[45] The condylar component includes anteroposteriorly divergent anterior and posterior portions.

[46] The posterior portion may comprise bone fixation screwholes.

[47] The posterior portion may comprise 6 bone fixation screwholes.

[48] According to a further aspect, there is provided a prosthesis kit for use for differently sized patients the prosthesis kit comprising a plurality of condylar components as described herein, wherein each of the condylar components comprise: condylar heads having the same diameter; and differing heights.

[49] The differing heights comprise at least two of about 55, 60 and 65 mm.

[50] The condylar components may comprise condylar necks having differing lengths.

[51] The condylar components may comprise an anteroposterior length of about 29 mm.

[52] The prosthesis kit may further comprise a fossa component sized for articularly engaging each of the plurality of condylar components.

[53] The fossa component may be anteroposteriorly symmetric

Brief Description of the Drawings [54] Notwithstanding any other forms which may fall within the scope of the present invention, a preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: [55] Figure 1 shows a (Dl) TMJ prosthesis in accordance with the prior art; [56] Figure 2 shows a further (D2) TMJ prosthesis in accordance with the prior art; [57] Figure 3A shows a fossa component in accordance with an embodiment of the present disclosure; [58] Figure 3B shows an improved TMJ prosthesis in accordance with an embodiment of the present disclosure; [59] Figure 4A shows a perspective view of a condylar component in accordance with an embodiment of the present disclosure; [60] Figure 3b shows a cross-sectional magnified sagittal plane view showing the articulation of a convex spherical articular surface of the condylar component and a concave spherical articular surface of the fossa component in accordance with an embodiment of the present disclosure; [61] Figure 5A shows a top view of the fossa component in accordance with an embodiment of the present disclosure; [62] Figure 5B shows a lateral elevation view of the fossa component in accordance with an embodiment of the present disclosure; [63] Figure 5C shows a posterior or anterior view of the fossa component in accordance with an embodiment of the present disclosure; [64] Figures 6A-C shows side elevation views of a plurality of condylar components for use with differently sized patients in accordance with an embodiment of the present disclosure; [65] Figure 6D shows a front elevation view of the condylar component of the prosthesis in accordance with an embodiment of the present disclosure; and [66] Figure 7 shows a side elevation view of the condylar component for comparison with the prior art D2 prosthesis.

Description of Embodiments [67] For the purposes of promoting an understanding of the principles in accordance with the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications of the inventive features illustrated herein, and any additional applications of the principles of the disclosure as illustrated herein, which would normally occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the disclosure.

[68] Before the structures, systems and associated methods relating to prosthesis for the replacement of a temporomandibular joint are disclosed and described, it is to be understood that this disclosure is not limited to the particular configurations, process steps, and materials disclosed herein as such may vary somewhat. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the disclosure will be limited only by the claims and equivalents thereof.

[69] In describing and claiming the subject matter of the disclosure, the following terminology will be used in accordance with the definitions set out below.

[70] It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[71] As used herein, the terms "comprising," "including," "containing," "characterised by," and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps.

[72] It should be noted in the following description that like or the same reference numerals in different embodiments denote the same or similar features.

[73] Figure 3B shows the TMJ prosthesis 1 for the replacement of a temporomandibular joint having a mandible and a temporal bone. The prosthesis 1 comprises a condylar component 2 for fastening to the mandible. Furthermore, the prosthesis 1 comprises a fossa component 3 for fastening to the temporal bone and specifically the zygomatic arch.

[74] The condylar component 2 comprises anteroposteriorly divergent posterior portion 4 and an anterior portion 5 which diverge at a midsection so as to define a substantially pear-shaped void 6 therebetween while joining at respective superior and inferior ends.

[75] The divergent posterior portion 4 and anterior portion 5 provides for enhanced structural integrity of the condylar component 2 including even in the event of breakage of either the posterior portion 4 or the anterior portion 5 in use. As can be seen, the anterior portion 4 may have greater width than that of the anterior portion 5 and comprise a series of screw holes 7 therealong for the receipt of bone screws therethrough in use. In the embodiment shown, the screw holes 7 extend along the inferior portion of the posterior portion 4 extending towards the inferior tip of the condylar component 2. Furthermore, in the embodiment shown, 6 screw holes 7 are provided.

[76] Stemming from the superior juncture of the posterior portion 4 and the anterior portion 5, is a condylar neck 8 which terminates superiorly at a condylar head 9 shown engaged within the fossa component 3 in figure 3B.

[77] As is also shown in figure 3B, the fossa component 3 comprises a body defining an inferior socket for receipt of the condylar head 9 therein in use. Furthermore, the fossa component 3 comprises a superior flange 10 extending upwardly from the body at an angle for securing the fossa component 3 to the cranial base in use and, in particular the zygomatic arch of the temporal bone.

[78] The superior flange 10 further comprises bone fixation screw holes 7 for the receipt of bone screws therethrough in use for fastening the flange 10 to the cranial base. Specifically, the zygomatic arch may be shaped so as to conform substantially to the medial of the fossa component 3 so as to allow the fossa component 3 to be inserted into the shaped zygomatic arch wherein, once inserted, bone screws may be inserted into the bone fixation screw holes 7 so as to fasten the flange 10 to the temporal bone.

[79] In the embodiment shown, the screw holes 7 of the superior flange 10 are adjacently staggered along two rows which may avoid bone line fractures.

[80] As can be further seen, whereas the superior flange of D2 extended further anteroposteriorly as is shown in figure 2A, the present superior flange 10 does not as the above cadaver studies shoed that such flange extension was not required to obtain suitable fixation stability and such further avoids the problems of D2 of unnecessary tissue removal to accommodate the extended flange.

[81] As can be further seen from figure 3B, the fossa component 3 is anteroposteriorly symmetric so as to be "evenhanded" so as to allow for either left or right-handed installation, thereby been distinguished from D1 which required two fossa components for respective left and right-hand installations.

[82] Figure 4B shows a cross-sectional magnified sagittal plane view further illustrating the articulation of the condylar component 2 with respect to the fossa component 3. Specifically, the condylar head 9 defines a convex spherical articular surface 11. The fossa component 3 cooperatively defines a concave spherical articular surface 12 defining an inferior socket being operable to engage the condylar head 9 in an articulating manner.

[83] Furthermore, the condylar head 9 and the socket are circular in the transverse/axial plane.

[84] As can be seen, the socket defined by the fossa component 3 is substantially deeper than that of prior art arrangements D1 and D2. Such a configuration was experimentally derived during the above-mentioned cadaver studies and practical experience including for reducing mislocation during installation which may damage the tympanic plate causing deafness, assisting the placement of the condylar head 9 during installation.

[85] Specifically, as can be seen, the concave spherical articular surface 12 of the fossa component 3 transitions substantially through 180° so as to provide a depth substantially equal to half that of the diameter of the socket.

[86] As can be appreciated, the posterior edge defined thereby terminates substantially vertically and so too does the opposite anterior edge.

[87] The posterior edge therefore creates a rearward rim which may prevent or reduce the likelihood of the condylar head 9 slipping posteriorly and damaging the tympanic plate.

[88] Furthermore, the deepened socket assists during installation wherein the deeper socket allows the surgeon to feel that the condylar head 9 has been correctly placed. Furthermore, the deepened socket further defines medial and lateral rims so as to further reduce or prevent mediolateral dislocation.

[89] In a particular embodiment, the diameter of the condylar head 9 may be about 75% of that of the socket. In a particular embodiment for example, the diameter of the condylar head 9 may be about 11 mm whereas the diameter of the socket defined by the fossa component 3 may be about 15 mm.

[90] In the embodiment shown in figure 4B the radii of the concave articular surface 12 and the convex articular surface 11 shown a substantially equal. Flowever, in embodiments, the radius of the convex articular surface 9 may be less than that of the convex articular surface 11 so as to allow for movement in the transverse plane.

[91] Turning now to figure 5, there are shown exemplary dimensions of the fossa component 3 in accordance with a particular embodiment. Specifically, figure 5A shows a top plan view, figure 5B shows a lateral view and figure 5C shows an anterior or posterior view of the fossa component 5.

[92] As can be seen from figure 5C, the superior flange 10 is angled mediolaterally with respect to a superior surface 13 of the body of the fossa component 3.

[93] Now, in a preferred embodiment, the angle between the superior surface 13 and the superior flange 10 is approximately 100°. Specifically, whereas the earlier D2 design comprised an angle of approximately 120°, such was found during the above-described cadaver studies to result in undesirably mediolateral rocking of the fossa component 3 once installed beneath the zygomatic arch. As such, the 100° angle between the superior surface 13 of the body of the fossa component 3 and the superior flange 10 was found experimentally to substantially prevent or reduce rocking of the fossa component 3.

[94] As can be further seen from figure 5C, the medial face 14 of the superior flange 10 may be substantially planar wherein the fossa component 3 comprises a curvature between the medial face 14 and the substantially planar superior surface 13. Furthermore, the lateral face 15 of the fossa component 3 may also be substantially planar and comprise cutaways 17 at an inferior portion thereof.

[95] The superior profile of the body of the fossa component 3 may be chamfered. Furthermore, as can be seen from figure 5C, the inferior edge 16 may be laterally medially upwardly angled with respect to the superior surface 13.

[96] Turning now to figure 6D, there is shown an anterior or posterior side elevation view of the condylar component 2. As can be seen, the inferior portion of the condylar component 2 may be substantially planar defining planar lateral and medial faces 20, 21.

[97] As can be further seen, the condylar neck 8 widens superiorly so as to transition between the relatively narrow inferior portion of the entire component 2 and the superior condylar head 8. In the embodiment shown, the inferior portion of the condylar component may comprise a thickness of approximately 2 mm whereas, and as alluded to above, the condylar head 9 may comprise a diameter of approximately 11 mm.

[98] As can be appreciated from the embodiment shown in figure 6D, the angle between the condylar head 9 and the inferior portion of the condylar component 2 is more upright when compared to D2. Specifically, figure 7 shows a comparison between the present prosthesis 1 and that of D2 wherein, as can be seen, the condylar neck 8 of the present prosthesis 1 is more upright (whereas that of D2 is angled an about 45°), such design configuration being experimentally derived during the above-described cadaver studies so as to present the head 9 within articulating range substantially centred around the vertical axis of the socket during normal use.

[99] Cadaver studies also showed that furthermore, the condylar head of D2 was too anteroposteriorly narrow and the angle of such would result in the head miss contacting the fossa component when placed in a real human.

[100] As can be further seen from figure 6D, the lateral extremity 18 of the condylar head 9 extends laterally beyond the lateral surface 20 of the inferior portion of the condylar component 2. Similarly, the medial extremity 19 of the condylar head 9 extends medially beyond the medial face 21 of the inferior portion of the condylar component 2. In the embodiment shown, the medial extremity 19 extends to an extent further beyond the medial face 21 as compared to the extent of the lateral extremity 18 extending beyond the lateral face 20. Furthermore, the apex 22 of the condylar head 9 may coincide substantially mediolaterally with respect to the inner face level 21 of the inferior portion of the condylar component 2.

[101] The particular configuration of the condyle component 2 and the fossa component 3 was experimentally found to allow for jaw opening of about 40° whereas prior art arrangements allowed only up to about 33°.

[102] Figure 6A-C shows a condylar component kit comprising a plurality of condylar components 2 of different dimensions suited for differing patients. Specifically, in the embodiment shown, the condylar component kit comprises three sizes, labelled as small, medium and large wherein, as can be appreciated, the constituent condylar components 2 comprise differing heights. As such, during surgery, the appropriately sized condylar component 2 may be selected in accordance with patient specific dimensions.

[103] Specifically, in one embodiment, the small condylar component 2 may comprise a height of about 55 mm, the medium-sized condylar component 22 may comprise a height of about 60 mm and the large condylar component may comprise a height of about 65 mm.

[104] As can be appreciated, the diameters of the condylar heads 9 of the constituent condylar components remains the same so as to allow for universal fit with a single design of fossa component 3. Furthermore, as alluded to above, the fossa component 3 provided herein, on account of being anteroposteriorly symmetric, allows for both left and right-handed installation.

[105] As can be further seen, the dimensions of the inferior portions of the condylar component 2 may remain substantially the same whereas the variation in height of the different sizes of condylar components 2 is provided primarily on account of appropriate elongation of the condylar neck 8. In this regard, the width of the inferior portion of the condylar component may be approximately 28.8 mm and the height approximately 48.4 mm.

Interpretation

Terminology [106] In describing the preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "forward", "rearward", "radially", "peripherally", "upwardly", "downwardly", and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

Comprising and Including [107] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

[108] Any one of the terms: including or which includes or that includes as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others. Thus, including is synonymous with and means comprising.

Scope of Invention [109] Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention. For example, any formulas given above are merely representative of procedures that may be used. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention.

[110] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Industrial Applicability [111] It is apparent from the above, that the arrangements described are applicable to the prosthesis industries.

Claims

Claims

1. A prosthesis for the replacement of a temporomandibular joint having a mandible and a temporal bone, the prosthesis comprising: a condylar component for fastening to the mandible, the condylar component including a condylar head having a convex spherical articular surface; a fossa component for fastening to the temporal bone, the fossa component having a concave spherical articular surface defining a socket being operable to engage the condylar head in an articulating manner wherein: the concave spherical articular surface traverses through approximately 180°.
2. A prosthesis as claimed in claim 1, wherein the diameter of the condylar head is approximately 75% than that of the socket.
3. A prosthesis as claimed in claim 2, wherein the condylar head comprises a diameter of between 5-15 mm.
4. A prosthesis as claimed in claim 3, wherein the condylar head comprises a diameter of about 11 mm.
5. A prosthesis as claimed in claim 1, wherein the condylar component comprises an inferior portion and a condylar neck transitioning between the inferior portion and the condylar head.
6. A prosthesis as claimed in claim 5, wherein the inferior portion is about 2mm thick.
7. A prosthesis as claimed in claim 5, wherein the condylar head defines a lateral extremity and wherein the inferior portion defines a lateral face and wherein the lateral extremity extends laterally beyond the lateral face.
8. A prosthesis as claimed in claim 5, wherein the condylar head defines a medial extremity and wherein the inferior portion defines a medial face and wherein the medial extremity extends medially beyond the medial face.
9. A prosthesis as claimed in claim 5, wherein the condylar head defines an apex and wherein the apex coincides mediolaterally approximately with the medial face.
10. A prosthesis as claimed in claim 5, wherein the condylar head defines a lateral and medial extremities and wherein the inferior portion defines lateral and medial faces and wherein the medial extremity extends medially beyond the medial face to a medial extent and wherein the lateral extremity extends laterally beyond lateral face to a lateral extent and wherein the medial extent is greater than the lateral extent.
11. A prosthesis as claimed in claim 1, wherein the fossa component is anteroposteriorly symmetric.
12. A prosthesis as claimed in claim 1, wherein the fossa component includes a superior lateral flange and a superior surface medially adjacent the superior lateral flange and wherein the superior lateral flange is poised at about 100° with respect to the superior surface.
13. A prosthesis as claimed in claim 12, wherein the superior lateral flange defines bone fixation screwholes therein.
14. A prosthesis as claimed in claim 13, wherein the bone fixation screwholes therein are arranged in superior and inferior rows and are dear George dear George dear adjacently staggered.
15. A prosthesis as claimed in claim 1, wherein the condylar component includes anteroposteriorly divergent anterior and posterior portions.
16. A prosthesis as claimed in claim 15, wherein the posterior portion comprises bone fixation screwholes.
17. A prosthesis as claimed in claim 16, wherein the posterior portion comprises 6 bone fixation screwholes.
18. A prosthesis kit for use for differently sized patients the prosthesis kit comprising a plurality of condylar components as claimed in any one of claims 1-17, wherein each of the condylar components comprise: condylar heads having the same diameter; and differing heights.
19. A prosthesis kit as claimed in claims 18, wherein the differing heights comprise at least two of about 55, 60 and 65 mm.
20. A prosthesis kit claimed in claims 18, wherein the condylar components comprises condylar necks having differing lengths.
21. A prosthesis kit claimed in claims 18, wherein the condylar components comprise an anteroposterior length of about 29 mm.
22. A prosthesis kit claimed in claims 18, further comprising a fossa component sized for articularly engaging each of the plurality of condylar components.
23. A prosthesis kit claimed in claims 22, wherein the fossa component is anteroposteriorly symmetric.