Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(Section 10 and Rule 13)

1. TITLE OF THE INVENTION:
LINER FOR A HIP PROSTHETIC DEVICE

2. APPLICANT:
Meril Corporation (I) Private Limited, an Indian company of the address Survey No. 135/139, Muktanand Marg, Bilakhia House, Pardi, Vapi, Valsad-396191 Gujarat, India.

The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF INVENTION
[1] The present disclosure relates to a medical device. More particularly, the present disclosure relates to a hip prosthesis.
BACKGROUND OF INVENTION
[2] A hip prosthesis, used in hip replacement surgeries, typically includes an acetabular shell, a liner, a femoral head, and a femoral stem. The acetabular shell is implanted in a patient’s acetabulum and provides a stable foundation, replacing a damaged socket of a hip joint. The liner is inserted in the acetabular shell to serve a smooth bearing surface for the femoral head. The femoral head may be a ball-shaped part of the hip joint which articulates with the acetabular shell, thereby facilitating hip movement. The femoral stem is an elongated component that is inserted into a femur to provide stability and support for the femoral head. The femoral stem is coupled to the femoral head.
[3] Various liners with different options are currently available. The different options pertain to various elevations, obliques, offsets, eccentric options and so on and accordingly have different shapes and orientations at the top of the liner. The different options of the liners allow the surgeons to choose an optimal liner for a patient providing sufficient femoral head coverage and ensuring proper hip kinematics post-implantation. However, conventionally, the liners used in hip prosthesis are manufactured as a single construct liner. In other words, there is a separate liner corresponding to each option. As a result, the surgeon has to choose an optimal liner from several liners each pertaining to a separate option. Further, the surgeon needs to assemble a liner having a first option with an acetabular shell and with a femoral head. To check a second liner with a different option, the surgeon then needs to decouple the liner from the acetabular shell and couple the second liner with it. Consequently, choosing a liner with an optimal option is a very cumbersome and time-consuming process with the conventional liners.
[4] Additionally, the portion of the liner impinging with the femoral stem undergoes higher wear and tear. Since the liners are made as a single construct, they are made of a single material. Consequently, the extra wear and tear increases the failure rate of the conventional liners. This leads to revision surgery, which not only increases the patient’s trauma but also their medical costs.
[5] Thus, there arises a need for a liner that overcomes the problems associated with the conventional liners.
SUMMARY OF INVENTION
[6] Particular embodiments of the present disclosure are described herein below with reference to the accompanying drawings; however, it is to be understood that the disclosed embodiments are mere examples of the disclosure, which may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure.
[7] The present disclosure relates to a hip prosthesis. In an embodiment, the hip prosthesis includes a first liner member and a second liner member. The first liner member is coupled to an acetabular shell. The first liner member is configured to reside within a cavity of the acetabular shell. The second liner member is detachably coupled to the acetabular shell and the first liner member. The second liner member includes a base portion detachably coupled to the acetabular shell. The first liner member and the second liner member when coupled to the acetabular shell form a complete liner for the acetabular shell.
BRIEF DESCRIPTION OF DRAWINGS
[8] The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the apportioned drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the disclosure is not limited to specific methods and instrumentality disclosed herein. Moreover, those in the art will understand that the drawings are not to scale.
[9] Fig. 1 depicts an exploded view of a hip prosthesis 200, in accordance with an embodiment of the present disclosure.
[10] Fig. 1a depicts a cross sectional view of the hip prosthesis 200, in accordance with an embodiment of the present disclosure.
[11] Fig. 2 depicts a perspective view of an acetabular shell 80, in accordance with an embodiment of the present disclosure.
[12] Fig. 2a depicts a perspective view of a portion of the acetabular shell 80, in accordance with an embodiment of the present disclosure.
[13] Fig. 3 depicts a perspective view of a first liner member 10, in accordance with an embodiment of the present disclosure.
[14] Fig. 3a depicts another perspective view of the first liner member 10, in accordance with an embodiment of the present disclosure.
[15] Fig. 4a1 depicts a perspective view of a second liner member 20, in accordance with an embodiment of the present disclosure.
[16] Fig. 4a2 depicts another perspective view of the second liner member 20, in accordance with an embodiment of the present disclosure.
[17] Fig. 4b1 depicts a perspective view of a second liner member 30, in accordance with an embodiment of the present disclosure.
[18] Fig. 4b2 depicts another perspective view of the second liner member 30, in accordance with an embodiment of the present disclosure.
[19] Fig. 4c1 depicts a perspective view of a second liner member 40, in accordance with an embodiment of the present disclosure.
[20] Fig. 4c2 depicts another perspective view of the second liner member 40, in accordance with an embodiment of the present disclosure.
[21] Fig. 4d1 depicts a perspective view of a second liner member 50, in accordance with an embodiment of the present disclosure.
[22] Fig. 4d2 depicts another perspective view of the second liner member 50, in accordance with an embodiment of the present disclosure.
[23] Fig. 4e1 depicts a perspective view of a second liner member 60, in accordance with an embodiment of the present disclosure.
[24] Fig. 4e2 depicts another perspective view of the second liner member 60, in accordance with an embodiment of the present disclosure.
[25] Fig. 4f1 depicts a perspective view of a second liner member 70, in accordance with an embodiment of the present disclosure.
[26] Fig. 4f2 depicts another perspective view of the second liner member 70, in accordance with an embodiment of the present disclosure.
[27] Fig. 5 depicts a side view of a femoral head component 90, in accordance with an embodiment of the present disclosure.
[28] Fig. 5a depicts a cross-sectional view of the femoral head component 90, in accordance with an embodiment of the present disclosure.
[29] Fig. 6 depicts a perspective view of a femoral stem component 100, in accordance with an embodiment of the present disclosure.
[30] Fig. 7 depicts an assembled view of the hip prosthesis 200 illustrating impingement between the femoral stem component 100 and the second liner member 20, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[31] Prior to describing the invention in detail, definitions of certain words or phrases used throughout this patent document will be defined: the terms “include” and “comprise”, as well as derivatives thereof, mean inclusion without limitation; the term “or” is inclusive, meaning and/or; the phrases “coupled with” and “associated therewith”, as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have a property of, or the like. Definitions of certain words and phrases are provided throughout this patent document, and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior as well as future uses of such defined words and phrases.
[32] Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean “one or more but not all embodiments” unless expressly specified otherwise. The terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive and/or mutually inclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise.
[33] Although the operations of exemplary embodiments of the disclosed method may be described in a particular, sequential order for convenient presentation, it should be understood that the disclosed embodiments can encompass an order of operations other than the particular, sequential order disclosed. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Further, descriptions and disclosures provided in association with one particular embodiment are not limited to that embodiment, and may be applied to any embodiment disclosed herein. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed system, method, and apparatus can be used in combination with other systems, methods, and apparatuses.
[34] Furthermore, the described features, advantages, and characteristics of the embodiments may be combined in any suitable manner. One skilled in the relevant art will recognize that the embodiments may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments. These features and advantages of the embodiments will become more fully apparent from the following description and apportioned claims, or may be learned by the practice of embodiments as set forth hereinafter.
[35] The present disclosure discloses a hip prosthesis. The hip prosthesis of present disclosure includes an acetabular shell, a first liner member, a second liner member, a femoral head and a femoral stem. The second liner member is detachably coupled to the first liner member and the acetabular shell. When coupled with the acetabular shell, the first liner member and the second liner member form a complete liner for the acetabular shell. The first liner member sits within the acetabular shell. The second liner member is designed to provide a corresponding liner option (e.g., a neutral liner option, an oblique liner option, an elevated liner option, an offset liner option, an offset and oblique liner option and so on). In an embodiment, multiple second liner members providing different liner options may be provided to the surgeon. The surgeon, therefore, has a flexibility to choose an optimal second liner member having a desired liner option according to anatomy of the patient. Since the second liner member is detachable, the surgeon can try different liner options by simply coupling and decoupling the second liner member easily. The surgeon does not need to remove the first liner member from the acetabular shell. Thus, the overall process for selection of the optimal liner based upon the requirements is very efficient and less time consuming as compared to the conventional liners.
[36] The conventional liners are made of a single material and suffers from wear and tear of a portion of the conventional liner which impinges with a femoral stem. As a result, the conventional liners are more prone to fail. In contrast, the teachings of the present disclosure allow the second liner member (which impinges with the femoral stem) to be made of a material which can better resist the wear and tear due to the impingement while the first liner member may be made of a different material. Consequently, the failure rate of the proposed liners is less compared to the conventional liners. This increases the longevity of the proposed liners, reduces chances of a revision surgery due to the liner failure and thereby, improves the patient outcome.
[37] Referring to figures, Fig. 1 depicts an exploded view of a hip prosthesis 200 and Fig. 1a depicts a cross sectional view of the assembled hip prosthesis 200, according to an embodiment of the present disclosure. The hip prosthesis 200 is used to replace the hip joint when it becomes damaged or diseased to the extent that it cannot function properly. The hip prosthesis 200 mimics the structure and function of the natural hip joint, allowing for improved mobility and reduced pain. In an embodiment, the hip prosthesis 200 includes an acetabular shell 80, a first liner member 10, a femoral head 90 and a femoral stem 100. The hip prosthesis 200 further includes a second liner member (such as a second liner member 20 in the depicted embodiment) detachably coupled with the first liner member 10 and the acetabular shell 80. When coupled with the acetabular shell 80, the first liner member 10 and the second liner member form a complete liner for the acetabular shell 80 (as depicted in Fig. 1a). The second liner member may be chosen based upon requirements, for example, based upon the anatomy of the patient.
[38] Fig. 2 depicts the acetabular shell 80 according to an embodiment of the present disclosure. The acetabular shell 80 replaces the acetabulum, which is the socket portion of the hip joint. The acetabular shell 80 restores stability and mobility to the hip joint. The acetabular shell 80 generally has a hemi-spherical shape in an embodiment, though it may have any other suitable shape. The acetabular shell 80 includes a cavity 81. The cavity 81 is configured to receive the first liner member 10. The first liner member 10 is coupled with the acetabular shell 80 within the cavity 81. In an embodiment, the acetabular shell 80 is provided with a face 81a (depicted in Fig. 2a) for coupling the acetabular shell 80 with the first liner member 10. It should be appreciated that the acetabular shell 80 may have any other suitable structural feature that can be used instead of, or in combination with, the face 81a for coupling the first liner member 10 with the acetabular shell 80.
[39] The acetabular shell 80 is also detachably coupled with second liner member. In an embodiment, the acetabular shell 80 includes a plurality of grooves (or grooves 83) provided circumferentially towards a top end of the acetabular shell 80. The grooves 83 may be uniformly or non-uniformly distributed. In the depicted embodiment, the acetabular shell 80 includes eight grooves 83 distributed uniformly. The grooves 83 are used to couple the second liner member with the acetabular shell 80. It should be appreciated that the acetabular shell 80 may have other structural features that may be used instead of, or in combination with, the grooves 83 for coupling the second liner member with the acetabular shell 80.
[40] Figs. 3 and 3a depict the first liner member 10, according to an embodiment of the present disclosure. The first liner member 10 acts as a cushion between an acetabular shell (such as the acetabular shell 80) and a femoral head (such as the femoral head 90). The first liner member 10 helps to absorb shock, reduces friction and distributes forces evenly between the acetabular shell 80 and the femoral head 90. The shape and contour of the first liner member 10 generally matches the shape and contour of an inner surface of the cavity 81. In an embodiment, the first liner member 10 has a tapered shape.
[41] In an embodiment, the first liner member 10 is configured to reside within the cavity 81 of the acetabular shell 80 of the hip prosthesis 200. The first liner member 10 is coupled to the acetabular shell 80 using any suitable coupling mechanism such as, without limitation, press-fit, snap-fit, interference fit, etc. In an embodiment, the first liner member 10 is coupled with the acetabular shell 80 using a press-fit mechanism. For example, a face 11 of the first liner member 10 press-fits with the face 81a of the acetabular shell 80. The first liner member 10 includes a cavity 13 configured to receive the femoral head 90. The shape of the cavity 13 generally matches the shape of femoral head 90. The cavity 13 has a bearing surface configured to articulate with an outer surface of the femoral head 90. In an exemplary embodiment, the bearing surface is concave.
[42] The dimensions of the first liner member 10 may vary according to or based upon the anatomy of the patient and/or of patient population in consideration. The first liner member 10 may be made of a material including, but not limited to, Ultra-High Molecular Weight Polyethylene (UHMWPE), polymethyl methacrylate (PMMA), high cross-linked polyethylene (HXLPE) including vitamin E, ceramic, etc. In an embodiment, the first liner member 10 is made of HXLPE with vitamin E.
[43] As explained earlier, the first liner member 10 and the second liner member when coupled to the acetabular shell 80, form a complete liner for the acetabular shell 80. The second liner member may be designed to provide a corresponding liner option with respect to elevation, offset, oblique, etc. Examples of the liner options include, but are not limited to, a neutral liner option, an oblique liner option, an elevated liner option, an offset liner option, an offset and oblique liner option. In an embodiment, the second liner member includes a base portion. According to an embodiment, the base portion has a ring shape. The base portion is detachably coupled with the acetabular shell 80 using a suitable coupling mechanism such as, without limitation, tab locking, snap fit, interference fit, etc. In an embodiment, the base portion includes a plurality of tabs provided circumferentially. The plurality of tabs may be distributed uniformly or non-uniformly. Each tab of the plurality of tabs is configured to engage with a corresponding groove 83 of the plurality of grooves 83 and lock the second liner member with the acetabular shell 80 via the tab-locking mechanism. Further, when the base portion is coupled with the acetabular shell 80, a bottom face of the base portion mates a face 15 of the first liner member 10. In an embodiment, the second liner member may further include an extended portion extending from a top rim of the base portion and covering at least a part of the top rim. The extended portion may be designed according to a liner option. A suitable second liner member having a desired liner option may be selected based upon the patient’s anatomy to provide enhanced results for patient, such as, improving joint stability through a greater range of flexion.
[44] The first liner member 10 and the second liner member may be made of the same or different material. According to an embodiment, the second liner member is made of a material having a higher strength and/or resistance to wear and tear than the material used for making the first liner member 10. The use of the higher strength or wear and tear resistant material for the second liner member reduces its wear and tear due to its impingement with the femoral stem 100. This decreases the chances of failure of the liner (formed by the first liner member 10 and the second liner member) and increases longevity of the overall prosthesis 200, thereby improving the patient outcome. The second liner member may be made of a material including, but not limited to, ultra-high molecular weight polyethylene (UHMWPE), polymethyl methacrylate (PMMA), high cross-linked polyethylene (HXLPE) including vitamin E, ceramic, etc. In an embodiment, the second liner member is made of ultra-high molecular weight polyethylene (UHMWPE). The use of UHMWPE to make the second liner member provides strength to the second liner member and prevents damage to the second liner member due to the impingement. The dimensions of the second liner member may vary according to or based upon the anatomy of the patient and/or of patient population in consideration.
[45] Exemplary second liner members are explained below. It should be understood that the second liner members illustrated herein are merely exemplary and teachings of the present disclosure can be extended to any suitable second liner member and the same is within the scope of the present disclosure.
[46] Figs. 4a1 and 4a2 show the second liner member 20, according to an embodiment of the present disclosure. The second liner member 20 includes a base portion 25. In the depicted embodiment, the base portion 25 includes four tabs 21 distributed uniformly. Each of the tabs 21 locks with a corresponding groove 83 of the grooves 83 of the acetabular shell 80 via a tab locking mechanism. Further, a face 20b of the base portion 25 mates with a face 81b (depicted in Fig. 2a) of the acetabular shell 80. Further, a bottom face 20c of the base portion 25 mates with a top surface 15 of the first liner member 10. A top rim 20d of the base portion is smooth and planar. In the depicted embodiment, the second liner member 20 does not include any extended portion. When the second liner member 20 and the first liner member 10 are coupled with the acetabular shell 80, they form a neutral liner. An inner face 20a of the base portion 25 impinges with a face 107 of the femoral stem 100.
[47] Figs. 4b1 and 4b2 show a second liner member 30, according to an embodiment of the present disclosure. The second liner member 30 includes a base portion 35 and an extended portion 33. The base portion 35 includes four tabs 31 distributed uniformly. The structure of the base portion 35 and the tabs 31 can be referred from the corresponding description of the base portion 25 and the tabs 21 and hence is not repeated for the sake of brevity. When the base portion 35 is coupled to the acetabular shell 80, a face 30b of the base portion 35 mates with the face 81b of the acetabular shell 80 and a bottom face 30c of the base portion 35 mates with the top face 15 of the first liner member 10.
[48] In an embodiment, the extended portion 33 includes an elevated wall 33a covering a portion of a top rim 30d of the base portion 35 and having a pre-defined height. In the depicted embodiment, the elevated wall 33a covers about half of the top rim 30d. The height of the elevated wall 33a is designed according to or based upon the anatomy of the patient and/or the patient population in consideration. When the second liner member 30 and the first liner member 10 are coupled with the acetabular shell 80, they form an elevated liner. An inner face 30a of the extended portion 33 impinges the face 107 of the femoral stem 100.
[49] Figs. 4c1 and 4c2 show a second liner member 40, according to an embodiment of the present disclosure. The second liner member 40 includes a base portion 45 and an extended portion 43. The base portion 45 includes four tabs 41 distributed uniformly. The structure of the base portion 45 and the tabs 41 can be referred from the corresponding description of the base portion 25 and the tabs 21 and hence is not repeated for the sake of brevity. When the base portion 45 is coupled to the acetabular shell 80, a face 40b of the base portion 45 mates with the face 81b of the acetabular shell 80 and a bottom face 40c of the base portion 45 mates with the top face 15 of the first liner member 10.
[50] In an embodiment, the extended portion 43 includes an oblique wall 43a covering at least a part of a top rim 40d of the base portion 45. The oblique wall 43a has a top face 43b making a pre-defined angle with the top rim 40d of the base portion 45. In the depicted embodiment, the top face 43b of the oblique wall 43a is 10-degree oblique with respect to the top rim 40d. When the second liner member 40 and the first liner member 10 are coupled to the acetabular shell 80, they form a 10-degree oblique liner. An inner face 40a of the extended portion 43 impinges the face 107 of the femoral stem 100.
[51] Figs. 4d1 and 4d2 show a second liner member 50, according to an embodiment of the present disclosure. The second liner member 50 includes a base portion 55 and an extended portion 53. The base portion 55 includes four tabs 51 distributed uniformly. The structure of the base portion 55 and the tabs 51 can be referred from the corresponding description of the base portion 25 and the tabs 21 and hence is not repeated for the sake of brevity. When the base portion 55 is coupled to the acetabular shell 80, a face 50b of the base portion 55 mates with the face 81b of the acetabular shell 80 and a bottom face 50c of the base portion 55 mates with the top face 15 of the first liner member 10.
[52] In an embodiment, the extended portion 53 includes an oblique wall 53a covering at least a part of a top rim 50d of the base portion 55. The oblique wall 53a has a top face 53b making a pre-defined angle with the top rim 50d of the base portion 55. In the depicted embodiment, the top face 53b of the oblique wall 53a is 15-degree oblique with respect to the top rim 50d. When the second liner member 50 and the first liner member 10 are coupled to the acetabular shell 80, they form a 15-degree oblique liner. An inner face 50a of the extended portion 53 impinges the face 107 of the femoral stem 100.
[53] Figs. 4e1 and 4e2 show a second liner member 60, according to an embodiment of the present disclosure. The second liner member 60 includes a base portion 65 and an extended portion 63. The base portion 65 includes four tabs 61 distributed uniformly. The structure of the base portion 65 and the tabs 61 can be referred from the corresponding description of the base portion 25 and the tabs 21 and hence is not repeated for the sake of brevity. When the base portion 65 is coupled to the acetabular shell 80, a face 60b of the base portion 65 mates with the face 81b of the acetabular shell 80 and a bottom face 60c of the base portion 65 mates with the top face 15 of the first liner member 10.
[54] In an embodiment, the extended portion 63 includes an oblique wall 63a covering a top rim (not shown) of the base portion 65 completely. The oblique wall 63a has a pre-defined offset with the top rim of the base portion 65. The oblique wall 63a has a top face 63b inclined at a pre-defined angle with respect to a radial plate of the top rim of the base portion 65. In the depicted embodiment, the oblique wall 63a has an offset of 4 mm and the top face 62b is inclined at 10-degree oblique with respect to the radial plane of the top rim of the base portion 65. When the second liner member 60 and the first liner member 10 are coupled to the acetabular shell 80, they form a liner having an offset and oblique. An inner face 60a of the extended portion 63 impinges the face 107 of the femoral stem 100.
[55] Figs. 4f1 and 4f2 show a second liner member 70, according to an embodiment of the present disclosure. The second liner member 70 includes a base portion 75 and an extended portion 73. The base portion 75 includes four tabs 71 distributed uniformly. The structure of the base portion 75 and the tabs 71 can be referred from the corresponding description of the base portion 25 and the tabs 21 and hence is not repeated for the sake of brevity. When the base portion 75 is coupled to the acetabular shell 80, a face 70b of the base portion 75 mates with the face 81b of the acetabular shell 80 and a bottom face 70c of the base portion 75 mates with the top face 15 of the first liner member 10.
[56] In an embodiment, the extended portion 73 includes an elevated wall 73a covering a top rim (not shown) of the base portion 75 completely. The elevated wall 73a has a pre-defined height uniformly. A top face 73b of the elevated wall 73 is parallel to the top rim of the base portion 75. In the depicted embodiment, the elevated wall 73a has a height of 4 mm. When the second liner member 70 and the first liner member 10 are coupled to the acetabular shell 80, they form an offset liner (having a 4 mm offset in the depicted embodiment). An inner face 70a of the extended portion 73 impinges the face 107 of the femoral stem 100.
[57] Fig. 5 and Fig. 5a shows the femoral head 90, according to an embodiment of the present disclosure. The femoral head 90 has a generally spherical shape. The femoral head 90 is configured to be inserted into the first liner member 10 and articulate with the first liner member 10. The femoral head 90 includes a cavity 91 configured to receive the femoral stem 100. In an embodiment, the cavity 91 may have a tapered shape. The femoral head 90 is suitably dimensioned according to or based on the anatomy of the patient and/or the patient population in consideration. The femoral head 90 can be made of a suitable biocompatible material such as, without limitation, stainless steel (e.g., high nitrogen stainless steel, SS 316), cobalt chromium, etc. In an example implementation, the femoral head 90 is made of cobalt chromium.
[58] Fig. 6 depicts the femoral stem 100, according to an embodiment of the present disclosure. The femoral stem 100 is coupled with the femoral head 90. The femoral stem 100 includes a trunnion 101, a neck 103 and a stem portion 105. The trunnion 101 is configured to be inserted into the cavity 91 of the femoral head 90. In an embodiment, the trunnion 101 is locked with an annular slot (not shown) within the cavity 91, though any other suitable coupling technique may be used to couple the trunnion 101 with the femoral head 90.
[59] The neck 103 may vary in length, curvature, and angle according to or based upon the anatomy of the patient and/or the patient population in consideration. The neck 103 ensures alignment and range of motion in the hip joint. In an embodiment, the face 107 of the neck 103 impinges with an inner face of the second liner member. For example, the face 20a of the second liner member 20 impinges with the face 107 of the neck 103 as depicted in Fig. 7.
[60] In an embodiment, the stem portion 105 mimics the shape of the natural femoral shaft. The stem portion 105 provide structural support and stability by anchoring securely within the medullary canal of the femur. The femoral stem 100 is suitably dimensioned according to or based on the anatomy of the patient and/or the patient population in consideration. The femoral stem 100 can be made of a suitable biocompatible material such as, without limitation, stainless steel, titanium, cobalt chromium, etc. In an example implementation, the femoral stem 100 is made of titanium.
[61] In an embodiment, the hip prosthesis 200 can be assembled as follows. The first liner member 10 is inserted into the acetabular shell 80, such that, the face 11 of the first liner member 10 press-fits with the face 81a of the acetabular shell 80, thereby coupling the first liner member 10 with the acetabular shell 80. A suitable second liner member is chosen based upon the patient’s anatomy and requirements. In the depicted embodiment, the second liner member 20 is chosen. Then, the second liner member 20 is inserted into the acetabular shell 80 such that the bottom face 20c of the second liner member 20 mates the face 15 of the first liner member 10. The tabs 21 of the second liner member 20 are inserted into and locked with the grooves 83 of the acetabular shell 20 and the face 20b of the second liner member 20 mates with the face 81b of the acetabular shell 80, thereby coupling the second liner member 20 with the acetabular shell 80. The first liner member 10 and the second liner member 20 upon coupling with the acetabular shell 80, form a complete liner for the acetabular shell 80 (as depicted in Fig. 1a). The trunnion 101 of the femoral stem 100 is inserted into the cavity 91 of the femoral head 90 and press-fitted in the annular slot within the cavity 91. The femoral head 90 is then inserted into the first liner member 10. An outer surface 90a of the femoral head 90 contacts the bearing surface of the cavity 13 of the first liner member 10 and articulates with it, thereby assembling the hip prosthesis 200 as depicted in Fig. 1a.
[62] The present disclosure provides several advantages. For example, the process of choosing an optimal liner with a desired option (e.g., offset, oblique, etc.) is very efficient due to the detachable coupling of the second liner member with the acetabular shell. One second liner member with a first liner option can be easily decoupled from the acetabular shell and another second liner member with a second liner option can be coupled with the acetabular shell. Further, since the first liner member and the second liner member are detachable, the complete liner for the acetabular shell can be made of two different materials. For example, the second liner member may be made of a material having better strength and more resistance to wear and tear causing by impingement of the second liner member with the femoral stem. This reduces the chances of failure and improves the life of the liner and therefore, of the hip prosthesis. This improves the overall patient outcome.
[63] The scope of the invention is only limited by the appended patent claims. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used. , Claims:WE CLAIM
1. A hip prosthesis (200) comprising:
i. a first liner member (10) coupled to an acetabular shell (80) and configured to reside within a cavity (81) of the acetabular shell (80); and
ii. a second liner member (20, 30, 40, 50, 60, 70) detachably coupled to the acetabular shell (80) and the first liner member (10), the second liner member (20, 30, 40, 50, 60, 70) having a base portion (25, 35, 45, 55, 65) detachably coupled to the acetabular shell (80);
iii. wherein, when coupled to the acetabular shell (80), the first liner member (10) and the second liner member (20, 30, 40, 50, 60, 70) form a complete liner for the acetabular shell (80).
2. The hip prosthesis (200) as claimed in claim 1, wherein the base portion (25, 35, 45, 55, 65, 75) has a ring-shape.
3. The hip prosthesis (200) as claimed in claim 1, wherein the second liner member (30, 40, 50, 60, 70) comprises an extended portion (33, 43, 53, 63, 73) covering at least a part of a top rim (30d, 40d, 50d) of the base portion (35, 45, 55, 65, 75).
4. The hip prosthesis (200) as claimed in claim 3, wherein the extended portion (43, 53) comprises an oblique wall (43a, 53a) covering at least a part of the top rim (40d, 50d) of the base portion (45, 55) and having a top face (43b, 53b) making a pre-defined angle with the top rim (40d, 50d) of the base portion (45, 55).
5. The hip prosthesis (200) as claimed in claim 3, wherein the extended portion (33) comprises an elevated wall (33a) covering a part of the top rim (30d) of the base portion (35).
6. The hip prosthesis (200) as claimed in claim 3, wherein the extended portion (73) comprises an elevated wall (73a) covering the top rim of the base portion (75) completely and having a pre-defined height.
7. The hip prosthesis (200) as claimed in claim 3, wherein the extended portion (63) comprises an oblique wall (63a) covering the top rim of the base portion (65) completely and having a pre-defined offset with the top rim of the base portion (65), the oblique wall (63a) having a top face (63b) inclined at a pre-defined angle with respect to a radial plane of the top rim of the base portion (65).
8. The hip prosthesis (200) as claimed in claim 1, wherein the base portion (25, 35, 45, 55, 65, 75) comprises a plurality of tabs (21, 31, 41, 51, 61, 71), each tab of the plurality of tabs (21, 31, 41, 51, 61, 71) is configured to engage with a corresponding groove of a plurality of grooves (83) provided towards a top surface of the acetabular shell (80).
9. The hip prosthesis (200) as claimed in claim 1, wherein the first liner member (10) and the second liner member (20, 30, 40, 50, 60, 70) are made of different materials.
10. The hip prosthesis (200) as claimed in claim 1, wherein the first liner member (10) comprises a cavity (13) having a bearing surface configured to articulate with a femoral head (90).