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:
TRIAL HEAD ASSEMBLY 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] Typically, during a hip replacement surgery, a proper fit and alignment of a prosthetic device, such as, an acetabular shell, a liner, a femoral head, and a femoral stem etc., is important for the success of the surgery. Usually, surgeons heavily rely on performance of trial components, for example, trial head, trial liner, etc., during an assessment phase of an implantation procedure to make informed decisions regarding implant selection and placement.
[4] For example, conventionally, surgeons employ trial heads before implanting actual implants. The surgeons couple different trial heads with a femoral stem component to check their fit and alignment as well as a range of motion to decide on an optimal size and offset of the actual modular head to be implanted. Typically, each trial head pertains to one size and one offset only. So, if the surgeon wants to test different offsets for a given size of a trial head, the surgeon needs to first couple one trial head of the given size having a first offset with the femoral stem, assess its alignment and range of motions, decouple it, couple another trial head of the same size but a different offset, and then assess its alignment and range of motions. This coupling-decoupling makes it a very complex and time-consuming process. Further, since there are several trial heads, it can lead to human errors such as, the surgeon missing to test some sizes or offsets or selecting a wrong size or offset. A wrong selection has serious consequences in terms of post-surgical complications such as dislocation, instability, impingement, which can compromise the patient’s recovery, cause pain and may even lead to revision surgery.
[5] Thus, there arises a need for a trial head assembly that overcomes the problems associated with the conventional devices.
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 femoral head trial assembly. The femoral head trial assembly includes a trial head and a sleeve. The trial head has a first end and a second end. The trial head includes a cavity, first threads and a plurality of slots. The cavity extends from the first end of the trial head towards the second end of the trial head for a partial length of the trial head. The first threads are provided on a surface of the cavity towards the first end of the trial head. The plurality of slots is provided on the surface of the cavity. Each slot of the plurality of slots corresponds to an offset position of a plurality of offset positions. The sleeve is rotatably coupled to the trial head and has a first end and a second end. The sleeve includes second threads and a locking member. The second threads are provided on an outer surface of the sleeve towards the first end of the sleeve. The second threads are configured to engage with the first threads. The locking member is provided on the outer surface of the sleeve. The locking member is configured to engage with the plurality of slots. In response to the locking member engaging with a slot of the plurality of slots, the sleeve is locked with the trial head at a corresponding offset position of the plurality of offset positions.
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 a top cross-sectional view of a femoral head trial assembly 100, in accordance with an embodiment of the present disclosure.
[10] Fig. 2a depicts a perspective view of a trial head 110, in accordance with an embodiment of the present disclosure.
[11] Fig. 2b depicts another perspective view of the trial head 110, in accordance with an embodiment of the present disclosure.
[12] Fig. 3a depicts a perspective view of a sleeve 120, in accordance with an embodiment of the present disclosure.
[13] Fig. 3b depicts another perspective view of the sleeve 120, in accordance with an embodiment of the present disclosure.
[14] Fig. 4a depicts the femoral head trial assembly 100 at a negative offset position, in accordance with an embodiment of the present disclosure.
[15] Fig. 4b depicts the femoral head trial assembly 100 at a zero-offset position, in accordance with an embodiment of the present disclosure.
[16] Fig. 4c depicts the femoral head trial assembly 100 at a first positive offset position, in accordance with an embodiment of the present disclosure.
[17] Fig. 4d depicts the femoral head trial assembly 100 at a second positive offset position, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE DRAWINGS
[18] 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.
[19] 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.
[20] 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.
[21] 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.
[22] The present disclosure discloses a femoral head trial assembly (or a head trial assembly). Using the head trial assembly allows surgeons to assess fit, alignment and performance of different femoral head component sizes and/or offsets between the femoral head component and a femoral stem component during a pre-implantation assessment phase of a hip replacement surgery to find a size and an offset that provides optimal stability and range of motion. In an embodiment, the head trial assembly includes a trial head and a sleeve. The trial head is dimensionally and structurally similar to the femoral head component and helps to determine the proper size of the femoral head component. The sleeve is rotatably coupled to the trial head and helps a surgeon to determine an optimal offset between the femoral head component and the femoral stem component.
[23] In an embodiment, the sleeve is configurable to be set at a plurality of offset positions. Therefore, unlike the conventional trial assemblies where different trial heads are required for different offset positions, the proposed head trial assembly can realize all different offsets using a single trial assembly and enables the surgeon to test different offsets with a single trial assembly. This decreases the time taken for the trial, thereby improving the efficiency of the overall procedure and the patient outcome. It also reduces the number of components required for the trial.
[24] Now referring to the figures, Fig. 1 shows a cross-sectional view of a femoral head trial assembly 100 (or a head trial assembly 100). The head trial assembly 100 includes a trial head 110 and a sleeve 120. The head trial assembly 100 enables the user to trial the alignment, fit and range of motion for a plurality of offset positions. In the depicted embodiment, the head trial assembly 100 enables the trial for four offsets, namely, a negative offset (e.g., -4 mm), a zero-offset, a first positive offset (e.g., +4 mm) and a second positive offset (e.g., +7 mm). It should be appreciated though that the teachings of the present disclosure can be applied to any two or more offsets and the same is within the scope of the present disclosure.
[25] The trial head 110 is used to assess femoral head size, offset, and range of motion before the permanent implantation. The evaluation done using trial head 110 minimizes complications and ensures proper alignment and functionality of the hip prosthesis. The trial head 110 mimics the shape and size of a femoral head to be implanted (hereinafter, implant femoral head). In an embodiment, the trial head 110 has a spherical body. The trial head 110 has a first end 110a and a second end 110b.
[26] Referring to Figs. 2a – 2b, the trial head 110 includes a cavity 111. The cavity 111 extends from the first end 110a towards the second end 110b for a partial length of the trial head 110. The shape of the cavity 111 corresponds to the shape of the sleeve 120. In an embodiment, the cavity 111 is generally cylindrical.
[27] In an embodiment, the cavity 111 is configured to receive the sleeve 120 (explained later). A surface 111a of the cavity 111 includes first threads 113 and a plurality of slots.
[28] The first threads 113 are provided on the surface 111a of the cavity 111 towards the first end 110a of the trial head 110. The first threads 113 may have a pattern, such as, without limitation, spiral, circular, helical, etc. In an embodiment, the first threads 113 have a spiral pattern (as depicted in Figs. 2a and 2b). The first threads 113 can be male threads or female threads. In an embodiment, the first threads 113 are a single female thread. The first threads 113 are used to couple the sleeve 120. In an embodiment, the first threads 113 includes a single thread.
[29] The plurality of slots is provided on the surface 111a of the cavity 111. Each of the plurality of slot corresponds to an offset position of a plurality of offset positions. The plurality of slots is configured to lock the sleeve 120 at the plurality of offset positions. In an embodiment, the plurality of slots includes four slots, namely, a first slot 115a, a second slot 115b, a third slot 115c, a fourth slot 115d. The first slot 115a, the second slot 115b, the third slot 115c and the fourth slot 115d correspond to the negative offset position, the zero-offset position, the first positive offset position and the second positive offset position, respectively. It should be appreciated that though the trial head 110 may have any suitable count of slots wherein the count of slots correspond to the count of offset positions desired for the head trial assembly 100. In an embodiment, the plurality of slots are holes.
[30] The plurality of slots is suitably positioned based upon the respective offset position. For example, a gross vertical distance between two adjacent slots is equal to a distance between the respective offset positions. In the depicted embodiment, the gross vertical distance between the second slot 115b and the first slot 115a is 4 mm, the gross vertical distance between the third slot 115c and the second slot 115b is 4 mm and the gross vertical distance between the fourth slot 115d and the third slot 115c is 3 mm.
[31] In an embodiment, the trial head 110 includes a passage 117 (shown in Fig. 1). The passage 117 extends from the second 110b of the trial head 110 to the cavity 111. The passage 117 provides a passage for air within the cavity 111 to escape when the sleeve 120 is inserted into the cavity 111. In an embodiment, the passage 117 has a cylindrical shape, though it may have any other suitable shape.
[32] The trial head 110 may be made of a material, such as, without limitation, acetal co-polymer, polyphenylsulfone (e.g., Radel R-5500), etc. or any other suitable material. In an exemplary embodiment, the trial head 110 is made of acetal co-polymer. The trial head 110 is suitably dimensioned based upon the bone anatomy of the patient and/or the patient population in consideration.
[33] The sleeve 120 is rotatably coupled to the trial head 110. The sleeve 120 is used to determine the correct offset between the femoral head component and the femoral stem component based upon the anatomy of the patient during the pre-implantation trial phase. Referring to Figs. 3a – 3b, the sleeve 120 has a hollow, cylindrical shape. The sleeve 120 has a first end 120a and a second end 120b. The sleeve 120 is configured to be coupled to the trial head 110 at the plurality of offset positions.
[34] In an embodiment, an outer surface 120c of the sleeve 120 includes second threads 121 and a locking member 123. The second threads 121 are provided towards the first end 120a of the sleeve 120. The second threads 121 may have a suitable pattern, such as, without limitation, spiral, circular, helical, etc. In an embodiment, the second threads 121 have a spiral pattern (as depicted in Figs. 3a and 3b). The second threads 121 are complementary to the first threads 113 and are configured to engage the first threads 113, thereby coupling the sleeve 120 to the trial head 110. In the depicted embodiment, the second threads 121 are a single, male thread.
[35] The locking member 123 is configured to lock the sleeve 120 with the trial head 110 at a desired offset position of the plurality of offset positions. For example, a portion of the locking member 123 is configured to engage with a slot of the plurality of slots corresponding to the desired offset position. In response to the locking member 123 engaging with a slot of the plurality of slots, the sleeve 120 is locked with the trial head 110 at a corresponding offset position of the plurality of offset positions. In an exemplary embodiment, the locking member 123 is a ball plunger. In this case, when a ball portion of the ball plunger aligns with a slot of the plurality of slots, the ball portion fits within the slot to lock the sleeve 120 at that position. The dimensions of the plurality of slots correspond to the dimensions of the ball portion.
[36] The sleeve 120 may be made of a material, such as, without limitation, acetal co-polymer, polyphenylsulfone (e.g., Radel R-5500), etc. or any other suitable material. In an exemplary embodiment, the sleeve 120 is made of acetal co-polymer. The cavity 111 and the sleeve 120 are suitably dimensioned such that the sleeve 120 can be inserted into and fit within the cavity 111.
[37] In an embodiment, the second end 120b of the sleeve 120 is inserted into the opening of the cavity 111 of the trial head 110. The sleeve 120 and the trial head 110 are aligned such that the first threads 113 of the trial head 110 engage with the second threads 121 of the sleeve 120. This couples the trial head 110 with the sleeve 120. The trial head 110 or the sleeve 120 is then rotated in a suitable direction to achieve a desired offset position of the plurality of offset positions as explained below.
[38] For example, the trial head 110 or the sleeve 120 is rotated until the locking member 123 aligns and locks with the first slot 115a, thereby locking the sleeve 120 at the negative offset position (e.g., -4 mm offset). At the negative offset position, a face 120d of the sleeve 120 is flushed with a face 110c of the trial head 110 (as depicted in Fig. 4a). Thus, the head trial assembly 100 achieves the negative offset.
[39] To achieve the zero-offset with the head trial assembly 100, the trial head 110 or the sleeve 120 is rotated until the locking member 123 aligns and locks with the second slot 115b, thereby locking the sleeve 120 at the zero-offset position (as depicted in Fig. 4b).
[40] To achieve the first positive offset with the head trial assembly 100, the trial head 110 or the sleeve 120 is rotated until the locking member 123 aligns and locks with the third slot 115c, thereby locking the sleeve 120 at the first positive offset position (as depicted in Fig. 4c).
[41] To achieve the second positive offset with the head trial assembly 100, the trial head 110 or the sleeve 120 is rotated until the locking member 123 aligns and locks with the fourth slot 115d, thereby locking the sleeve 120 at the second positive offset position (as depicted in Fig. 4d).
[42] The sleeve 120 includes a cavity 125 (depicted in Figs. 3a-3b) extending from the first end 120a towards the second end 120b for a partial length of the sleeve 120. The cavity 125 is configured to receive a trunnion (not shown) of the femoral stem component (not shown). The cavity 125 has a tapered shape. The cavity 125 includes a longitudinal slot 127 (depicted in Figs. 1 and 3b) extending from the first end 120a and an annular slot 129 provided towards the second end 120b (depicted in Fig. 1). The longitudinal slot 127 is configured to receive a protrusion on the trunnion and functions as a guide channel while inserting the trunnion into the sleeve 120. The annular slot 129 is configured to lock the trunnion with the sleeve 120, and thereby with the head trial assembly 100.
[43] Advantageously, the head trial assembly proposed in the present disclosure enables assessing a precise alignment and compatibility between the femoral head component and the femoral stem component to be implanted thereby minimizing a risk of mismatch between them during the hip replacement surgery. This avoids post-surgical complications. The proposed head trial assembly allows the user to assess different offsets using a single assembly and thus, reduces the complex and time-consuming process of managing several components and coupling (and decoupling) different trial heads for testing alignment for different offsets as seen with conventional systems. The proposed head trial assembly is very easy to operate and prevents human errors. This reduces delays and inconvenience during the hip replacement surgery. Furthermore, an enhanced compatibility assessment of the femoral head component and the femoral stem component before employing actual implant mitigates a risk of instability and dislocation post-surgery thereby promoting better patient outcomes and minimizing a need for additional interventions.
[44] 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 femoral head trial assembly (100) comprising:
a. a trial head (110) having a first end (110a) and a second end (110b) and comprising:
i. a cavity (111) extending from the first end (110a) of the trial head (110) towards the second end (110b) of the trial head (110) for a partial length of the trial head (110);
ii. first threads (113) provided on a surface 111a of the cavity (111) towards the first end (110a) of the trial head (110); and
iii. a plurality of slots provided on a surface 111a of the cavity (111), each slot of the plurality of slots corresponds to an offset position of a plurality of offset positions; and
b. a sleeve (120) rotatably coupled to the trial head (110) and having a first end (120a) and a second end (120b), the sleeve (120) comprising:
i. second threads (121) provided on an outer surface (120c) of the sleeve (120) towards the first end (120a) of the sleeve (120), the second threads (121) are configured to engage with the first threads (113); and
ii. a locking member (123) provided on the outer surface (120c) of the sleeve (120) and configured to engage with the plurality of slots;
c. wherein, in response to the locking member (123) engaging with a slot of the plurality of slots, the sleeve (120) is locked with the trial head (110) at a corresponding offset position of the plurality of offset positions.
2. The femoral head trial assembly (100) as claimed in claim 1, wherein the first threads (113) are a single female thread and the second threads (121) are a single male thread.
3. The femoral head trial assembly (100) as claimed in claim 1, wherein the locking member (123) is a ball plunger and the plurality of slots are holes.
4. The femoral head trial assembly (100) as claimed in claim 1, wherein the plurality of offset positions comprises a negative offset position, a zero-offset position, a first positive offset position and a second positive offset position.
5. The femoral head trial assembly (100) as claimed in claim 1, wherein the sleeve (120) comprises:
a. a cavity (125) extending from the first end (120a) towards the second end (120b) for a partial length of the sleeve (120) and configured to receive a trunnion of a femoral stem component; the cavity (125) comprising:
i. a longitudinal slot (127) extending from the first end (120a) and configured to receive a protrusion on the trunnion; and
ii. an annular slot (129) provided towards the second end (120b) and configured to lock the trunnion of femoral stem component with the sleeve (120).