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:
CONSTRAINED DISTAL STEM CENTRALIZER FOR INTRAMEDULLARY PROSTHESIS

2. APPLICANT:
Meril Healthcare Pvt. Ltd., an Indian company of the Survey No. 135/139, Bilakhia House, Muktanand Marg, Chala, Vapi- 396191, Gujarat, India.

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

FIELD OF INVENTION
[001] The present invention relates to a centralizer. More specifically, the present invention relates to a distal stem centralizer for an intramedullary stem type prosthesis.
BACKGROUND OF INVENTION
[002] An intramedullary implant is a medical device that is inserted into a medullary cavity of a bone. The intramedullary implant is used to stabilize and support the bone that is damaged or weakened due to injury, disease, or other conditions.
[003] Generally, the intramedullary implant is in the form of a stem type prosthesis. The stem type prosthesis is typically made of a biocompatible material, such as titanium, and is designed to mimic the shape and function of a natural bone.
[004] The stem type prosthesis typically includes a stem, which is inserted into the medullary cavity of the bone, and a head, which sits on top of the stem and provides a surface for articulation with another bone. The stem type prosthesis is, generally, used in joint replacement surgeries, such as total hip arthroplasty (THA), total shoulder arthroplasty and total knee arthroplasty (TKA).
[005] The stem and the head of the stem type prosthesis are mostly made of a biocompatible material, such as titanium, cobalt-chromium alloy, ceramic, etc. The head is shaped to match the natural joint surface. The stem is designed to mimic the shape and function of the natural bone. The stem is designed to fit snuggly into the medullary cavity of the bone, and is typically secured in place with a combination of bone cement, screws and/or press-fit.
[006] In order to prepare the medullary canal for receiving the stem type prosthesis, bone undergoes a surgical process called "reaming." During this process, a surgeon reams inner trabecular bone and shapes the medullary canal to fit the stem type prosthesis. This in turn widens the medullary canal as per a diametrical size of the stem type prosthesis.
[007] Specifically, in case of cemented stem type prosthesis, the medullary canal is additionally reamed than the diametrical size of the stem in order to accommodate cement mantle. Hence, in such cases, owing to the extra space available, there are high chances of misalignment of the stem of the stem type prosthesis thereby impacting the stability of the stem type prosthesis. Therefore, proper alignment of the stem type prosthesis is critical for long term success of the stem type prosthesis.
[008] In order to solve this problem, a centralizer (distal stem centralizer) is used. The centralizer is mounted on a distal tip of the stem type prosthesis initially and then inserted into the medullary canal, which is pre-filled with bone cement that forms the cement mantle. The centralizer helps in alignment of the stem type prosthesis in the medullary canal thereby ensures correct and successful implantation of the stem type prosthesis.
[009] There are many structures of centralizers that are currently available for positioning the stem type prosthesis. However, most of the existing centralizers are incapable of securely aligning the stem type prosthesis and often lead to breakage of components thereby causing unsuccessful implantation of the stem type prosthesis. This causes movement of the stem type prosthesis relative to surrounding bone, mostly either varus (inward angulation towards body's midline) or valgus (outward angulation away from the body’s midline) due to non-uniform distribution of cement mantle surrounding the stem type prosthesis, leading to loosening of the stem type prosthesis post operatively.
[0010] Therefore, there exists a need for an improved centralizer which can overcome the drawbacks associated with existing centralizers.
SUMMARY OF INVENTION
[0011] The present invention relates to a distal stem centralizer for an intramedullary prosthesis. The distal stem centralizer includes a holder for receiving a tip of a distal segment of a prosthesis. The holder is disposed along a central axis of the distal stem centralizer. The holder includes an outer surface. The distal stem centralizer further includes at least two wings projecting from the outer surface of the holder at a pre-defined angle with respect to the central axis. The at least two wings are circumferentially spaced apart. Each of the at least two wings have a free end and an attached end that is coupled to the outer surface of the holder. The free end is heighted above the holder to cause flexing of the wings towards the central axis. The at least two wings have an inner face.
[0012] At least one stopper protrudes from at least one of, the inner face and/or the outer surface, The at least one stopper is positioned in such a way that the at least one stopper lies between each wing of the at least two wings and the holder to restrict maximum displacement of the wings towards the central axis thereby allowing constrained flexing of the wings.
[0013] The distal stem centralizer may include a holder having a tapered outer surface to restrict maximum displacement of the wings towards the central axis thereby allowing constrained flexing of the wings and acting as a stopper in itself.
[0014] The foregoing features and other features as well as the advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[0015] 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 instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale.
[0016] Figure 1 depicts a centralizer 100 coupled to a stem type prosthesis 10 in accordance with an embodiment of the present invention.
[0017] Figure 1a depicts a centralizer 100 coupled to the stem type prosthesis 10 and implanted at a target site in accordance with an embodiment of the present invention.
[0018] Figures 2a depicts a magnified view of the centralizer 100 having wings 103 with stoppers 105a in accordance with an embodiment of the present invention.
[0019] Figures 2b depicts a magnified view of the centralizer 100 having a tapered holder 101h in accordance with an embodiment of the present invention.
[0020] Figures 2c-2d depict the centralizer 100 having wings 103 with stoppers 105b in accordance with an embodiment of the present invention.
[0021] Figure 2e depicts the centralizer 100 having wings 103 with longitudinal stoppers 105c in accordance with an embodiment of the present invention.
[0022] Figures 2f-2g depict the centralizer 100 having a holder 101 with ring-type stoppers 105d in accordance with an embodiment of the present invention.
[0023] Figure 2h depicts the centralizer 100 having the holder 101 with longitudinal stoppers 105e in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF DRAWINGS
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] In accordance with the present disclosure, a distal stem centralizer (hereon referred as ‘centralizer’) for a stem type prosthesis (hereon referred as ‘prosthesis’ or ‘intramedullary prosthesis’ or ‘intramedullary stem type prosthesis’) is disclosed. The centralizer disclosed in the present invention is used to guide and align the stem type prosthesis at a target site. The target site of the present invention is an intramedullary canal of a bone. The centralizer of the present invention helps to prevent malpositioning of the prosthesis and improves the stability of the prosthesis at the time of implantation, cementing operations and post-implantation as well.
[0029] The centralizer of the present invention includes various components such as a holder, a plurality of wings and at least one stopper. The holder is structured to receive and hold a stem of the stem type prosthesis. The wings are coupled to an outer surface of the holder such that one of the ends of the wings is attached to the holder while the other end is free (or free end). The free end of each of the wings extends away from the holder thereby making an angle with respect to a central axis of the centralizer which in turn allow the wings to flex towards the central axis of the centralizer.
[0030] The stopper(s) of the present invention may either be protruding from an inner face of the wings or the outer surface of the holder. Alternatively, the present invention may include a tapered holder which acts as a stopper in itself. The stopper(s) allows constrained/controlled flexing of the wings by restricting unwanted movement or displacement of the wings thereby preventing any chances of breakage of components during implantation of the prosthesis and cementing operations such as curing. Also, owing to the presence of the stopper(s), the stability of the wings is maintained which significantly reduces the chances of improper positioning of the prosthesis leading to successful implantation of the prosthesis. Further, the restricted movement of the wings helps in maintaining even distribution of the bone cement thereby, eliminating any chances of fracture due to loosening of the prosthesis caused by uneven distribution of the bone cement.
[0031] Now referring to figures, Figure 1 depicts a prosthesis 10 coupled to a centralizer 100 of the present invention. The prosthesis 10 may be in the form of an artificial cemented bone implant that may be used for correcting bone defects at various joints of the body, using cement fixation.
[0032] In an embodiment, the prosthesis 10 is used for total hip replacement. The prosthesis 10 may be made of any biocompatible material such as titanium alloy, high nitrogen stainless steel (HNSS), cobalt alloy, etc. In an embodiment, the prosthesis 10 is made of high nitrogen stainless steel (HNSS).
[0033] As illustrated in Figure 1, the prosthesis 10 includes a proximal section 10a, and a stem 10b. Figure 1a depicts the prosthesis 10 fixed at a target site via the centralizer 100 of the present invention.
[0034] The proximal section 10a of the prosthesis 10 includes an acetabular cup 10a1 and an acetabular interface 10a2. The acetabular cup 10a1 is to be attached to an acetabulum (the socket of the hip joint) and serves as a new socket for a head of femur.
[0035] The acetabular interface 10a2 is placed between the stem 10b and the acetabular cup 10a1. The stem 10b may be in the form of a rod that is inserted into the femur (or thigh bone) during total hip replacement surgery. The stem 10b is designed to provide support and stability to the prosthesis 10. The stem 10b may be press-fitted or cemented into the femur, and serves as the attachment point for the prosthesis 10.
[0036] The stem 10b of the prosthesis 10 may include a proximal segment b1 that is connected to the acetabular interface 10a2 and a distal segment b2.
[0037] As shown in Figure 1, a tip of the distal segment b2 of the stem 10b is coupled to the centralizer 100 of the present invention. The centralizer 100 is positioned so that it sits against the tip of the distal segment b2 of the stem 10b and covers the distal segment b2 of the stem 10b engaging with a fix fit. The centralizer 100 extends outwards to make contact with the inside of the femur as shown in Figure 1. The centralizer 100 is positioned around the prosthesis 10 to maintain its proper placement within a medullary canal ‘IC’ (or canal, or intramedullary canal). The stem 10b of the prosthesis 10 is inserted into a reamed medullary canal ‘IC’ and cemented in place to provide stability and support. Hence, as shown in Figure 1a, the prosthesis 10 along with the centralizer 100 are positioned and fixated in the canal ‘IC’.
[0038] The centralizer 100 works by exerting radial pressure against the walls of the medullary canal ‘IC’, keeping the prosthesis 10 in the center and causing a centralizing effect on the prosthesis 10. Hence, the centralizer 100 helps to implant the prosthesis 10 into the canal ‘IC’ of the bone while centralizing the prosthesis 10 in the canal ‘IC’ successfully without component breakage while moving the prosthesis 10 downwards into a cement mantle. The centralizer 100 helps to ensure that the stem 10b is properly aligned and centered within the femur and helps to reduce the risk of loosening or dislocation (migration) of the prosthesis 10. The centralizer 100 provides uniform load distribution to a surrounding bone tissue. The centralizer 100 helps to guide the stem 10b into the correct position within the femur.
[0039] The centralizer 100 may be made of a biocompatible or a bioabsorbable material such as PMMA (poly(methyl methacrylate)) , UHMWPE (Ultra-High Molecular Weight Polyethylene), silicone, etc. In an embodiment, the centralizer 100 is made of PMMA.
[0040] As shown in Figures 2a-2h, the centralizer 100 includes various components such as a holder 101, a plurality of wings 103 (or at least two wings 103) and at least one stopper. The aforesaid components are disposed along a central axis ‘x’ of the centralizer 100. The aforesaid components may be formed as a single piece or alternatively, be assembled together in a pre-defined manner to form an integral structure. In an embodiment, the said components may be formed by way of extrusion. However, other techniques may also be employed for forming the same.
[0041] The holder 101 of the present invention is structured to receive the tip of the distal segment b2 of the stem 10b and secure the same in place. The holder 101 acts as a base to the prosthesis 10 and allows the tip of the distal segment b2 to be securely seated within the holder 101 thereby facilitating stable implantation of the prosthesis 10 at the target site without any dislocation/migration.
[0042] The holder 101 may include a pre-defined shape and dimensions. The shape and dimensions of the holder 101 may be dependent upon the shape and dimensions of the tip of the distal segment b2 of the stem 10b of the prosthesis 10. The pre-defined shape of the holder 101 may be, without limitation, cylindrical, spherical, conical, etc. In an embodiment, the holder 101 is cylindrical in shape having a circular cross-section.
[0043] As illustrated in Figures 2a-2h, the holder 101 includes a top end 101a and a bottom end 101b disposed along the central axis ‘x’ of the centralizer 100. In an exemplary embodiment, the top end 101a of the holder 101 is open while the bottom end 101b of the holder 101 is closed thereby forming a cylindrical cup type structure having a hollow cavity. Such a construction of the holder 101 helps to receive the tip of the distal segment b2 of the stem 10b.
[0044] The bottom end 101b of the holder 101 may be, without limitation, spherical, flat, oval, etc. In an embodiment, the holder 101 has a spherical bottom end 101b.
[0045] The holder 101 may have a uniform cross-section from the top end 101a to the bottom end 101b as shown in Figures 2a and 2c-2h. Alternatively, the holder 101 may include a non-uniform cross-section from the top end 101a to the bottom end 101b. For example, Figure 2b shows a tapered holder 101h having the outer surface 101d being tapered from the top end 101a to the bottom end 101b. Such a tapered profile of the holder 101h itself acts as a stopper and allows constrained/controlled flexing of the wings 103 (elaborated below).
[0046] The holder 101 may include an inner surface 101c corresponding to an inner circumference of the holder 101. Likewise, the holder 101 includes an outer surface 101d that corresponds to an outer circumference of the holder 101. The inner surface 101c of the holder 101 is configured to be in constant contact with the tip of the distal segment b2 of the stem 10b. The inner surface 101c may be a uniform/smooth surface or a rough/non-uniform surface. In an embodiment, the inner surface 101c is a smooth surface. Alternatively, the inner surface 101c may include tiny bumps (not shown) to tightly secure the distal segment b2 of the stem 10b. In an embodiment, the inner surface 101c of the holder 101 is tapered from the top end 101a to the bottom end 101b. Such a tapered profile of the holder 101 helps the centralizer 100 to accept variable sizes of the stem 10b.
[0047] The outer surface 101d of the holder 101 is configured to be in constant contact with the bone cement. The outer surface 101d may be a uniform/smooth surface or a rough/non-uniform surface. In an embodiment, the outer surface 101d is a smooth surface. Alternatively, the outer surface 101d may include a plurality of ridges (not shown) to allow the bone cement to adhere to the centralizer 100 properly.
[0048] The outer surface 101d of the holder 101 may be provided with the plurality of wings 103. As evident from Figures 2a-2h, the wings 103 are projecting components of the centralizer 100 that are extruded from the outer surface 101d of the holder 101.
[0049] The wings 103 of the centralizer 100 act as a guide, keeping the prosthesis 10 in place and preventing it from misaligning (becoming off-center) as the prosthesis 10 is inserted into the canal ‘IC’. Thus, the wings 103 help in proper alignment of the prosthesis 10 thereby ensuring that the load is distributed evenly across the bone and risk of instability of the prosthesis 10 is completely eliminated.
[0050] In addition to maintaining proper alignment, the wings 103 act as a buffer between the prosthesis 10 and surrounding tissue, thus reducing any risk of injury/damage to the surrounding tissue during the implantation process.
[0051] The centralizer 100 may include at least two wings 103. The number of wings 103 may be dependent upon the cross-section of the centralizer 100. In an embodiment, the centralizer 100 includes three wings 103 as illustrated in Figures 2a-2h.
[0052] The wings 103 may be uniformly distributed around the outer surface 101d of the holder 101. Alternatively, the wings 103 may randomly project from the outer surface 101d of the holder 101. Irrespective of the manner of distribution of the wings 103, the wings 103 are circumferentially spaced apart in such a way that an appropriate radial spacing is available for cement to move/flow upon insertion of the prosthesis 10 for avoiding bubble formation as bubbles in the cement mantle induce implantation defects thereby leading to failure of the prosthesis 10.
[0053] Depending upon the number of wings 103 present as well as the manner of disposition of the wings 103, the wings 103 are placed at a pre-defined angle ‘A’ with respect to each other. In an embodiment shown in Figures 2a-2h, the centralizer 100 includes three wings 103 that project equidistantly at an angle of 120 degrees with respect to each other.
[0054] The wings 103 of the present invention help to provide a larger surface area for creating centering force and help to guide the centralizer 100 into place at the target site during implantation of the prosthesis 10. Additionally, the wings 103 help to improve the stability of the centralizer 100 during cementing operations and reduce the risk of differential sticking (an imbalance in the pressure applied to the prosthesis 10, causing it to become stuck in the bone).
[0055] The wings 103 may be made of a similar material as that of the holder 101 for example, PMMA.
[0056] The wings 103 may be in the form of flap-type structures having a pre-defined shape such as, without limitation, rectangular, oval, spherical, triangular, etc. In an embodiment, the wings 103 are rectangular in shape and have smooth edges. The wings 103 may include pre-defined dimensions that are dependent upon the diametrical size of the prosthesis 10.
[0057] The wings 103 may include a free end 103a and an attached end 103b. As the name suggests, the attached end 103b of each of the wings 103 is coupled to the outer surface 101d of the holder 101 at a pre-defined location. In an embodiment, the pre-defined location corresponds to a location that lies midway along a length of the holder 101. However, it should be noted that other locations of attachment of the wings 103 on the holder 101 are also within the scope of the present invention.
[0058] The free end 103a remains unattached and does not contact the holder 101. Hence, owing to the free end 103a, each of the wings 103 extends away from the holder 101 thereby making a pre-defined angle ‘B’ with respect to the central axis ‘x’. The pre-defined angle ‘B’ depends upon the dimensions of the canal ‘IC’.
[0059] In an exemplary embodiment, the wings 103 are so positioned that the free end 103a are heighted above the holder 101. Such a disposition helps in flexing of the wings 103. Flexing of the wings 103 helps the centralizer 100 to adjust/adapt/conform to the shape of the reamed medullary canal ‘IC’ and provide better stability and control over the placement of the prosthesis 10. This helps to ensure that the prosthesis 10 is positioned correctly within the bone and remains centered, reducing the risk of implant migration and improving the stability of the prosthesis 10.
[0060] Flexing also helps to reduce the amount of pressure placed on the bone during implantation, which can help to minimize the risk of bone damage and improve the overall outcome of the implantation procedure.
[0061] Owing to the presence of the stopper(s) (described below in detail), the wings 103 are capable of flexing towards the central axis ‘x’ of the centralizer 100 upon external loading in a controlled/constrained manner. The controlled/constrained flexing of the wings 103 allows the centralizer 100 to adjust itself as per the size of the reamed intramedullary canal ‘IC’, thus aligning the prosthesis 10 at the center of the canal ‘IC’. The controlled/constrained flexing of the wings 103 also helps in distributing the bone cement mantle surrounding the prosthesis 10 evenly and hence, improves fixation of the prosthesis 10 without breakage of any component.
[0062] Further, the free end 103a of the wings 103 may be bent or curved inwardly towards the inner face 103c at a pre-defined angle ‘C’. Such a bend towards the free end 103a helps to maximize the surface area of the wings 103 in contact with the canal ‘IC’ while insertion/implantation of the prosthesis 10.
[0063] The wings 103 may include uniform dimensions along the length of the wings 103 i.e. from the attached end 103b to the free end 103a as shown in Figures 2a-2h. Alternatively, the dimensions of the wings 103 may vary along the length of the wings 103. For example, the wings 103 may include a greater width at the attached end 103b which gradually decreases towards the free end 103a. Though not explicitly disclosed/illustrated, other combinations of varied dimensions are also within the teachings of the present invention.
[0064] Each of the wings 103 includes an inner face 103c and an outer face 103d. The inner face 103c corresponds to a surface that extends from the attached end 103b to the free end 103a and faces the holder 101. The outer face 103d corresponds to a surface that extends from the attached end 103b to the free end 103a and faces away from the holder 101.
[0065] The inner face 103c and the outer face 103d may be uniform/smooth or non-uniform/rough. In an embodiment, the inner face 103c and the outer face 103d are uniform and smooth.
[0066] As mentioned above, the centralizer 100 of the present invention includes one or more stoppers to prevent uncontrolled flexing of the wings 103. At the time of implantation, the uncontrolled flexing of the wings 103 towards the central axis ‘x’ may cause breakage of components while the prosthesis 10 is inserted in the canal ‘IC’ filled with cement mantle. Also, uncontrolled flexing of the wings 103 may cause breakage of components during curing of the bone cement. Further, uncontrolled flexing of the wings 103 causes movement of the stem type prosthesis 10 relative to surrounding bone, mostly either varus (inward angulation towards body's midline) or valgus (outward angulation away from the body’s midline) due to non-uniform distribution of cement mantle surrounding the stem type prosthesis 10, leading to loosening of the stem type prosthesis 10 post operatively.
[0067] The stopper(s) of the present invention is provided to restrict the maximum displacement of the wings 103 towards the central axis ‘x’ of the centralizer 100 thereby allowing controlled/constrained flexing of the wings 103.
[0068] The stopper(s) may protrude from a pre-defined location of the centralizer 100. In an embodiment, in order to restrict the flexing of the wings 103, one or more stoppers either protrude from the inner face 103c of the wings 103 or the outer surface 101d of the holder 101.
[0069] The stopper(s) of the present invention may be made of a material similar to the holder 101 or the wings 103.
[0070] The stopper(s) of the present invention may be provided in different configurations/geometry/shape/size/number as shown in Figures 2a-2h. It should be noted that the embodiments of the stoppers as illustrated in figures 2a-2h are only exemplary in nature and any structure that forms a part of the centralizer 100 and is targeted to restrict the maximum displacement of the wings 103 beyond a certain level of displacement required for implantation and fixation of the prosthesis 10 is within the scope of the present invention. Hence, irrespective of the structure of the stopper, the dimensions of the stopper are such that the flexing/displacement of the wings 103 is controlled or partially restricted/constrained. Further, irrespective of the structure and dimensions of the stopper(s), the stopper(s) is positioned in such a way that each stopper lies between a wing 103 and the holder 101 to allow constrained flexing of the wings 103 towards the central axis ‘x’ to restrict maximum displacement of the wings 103 towards the central axis ‘x’ thereby allowing constrained flexing of the wings 103.
[0071] In an embodiment, each of the inner faces 103c of the wings 103 are provided with the stoppers. As shown in figure 2a, each inner face 103c includes a stopper 105a in the form of a bumped notch having a steep slope protruding from the inner face 103c towards its free end 103a. Though figure 2a illustrates a single stopper 105a on each wing 103, the number of stoppers 105a may vary depending upon requirement. For example, in case of two stoppers 105a, the stoppers 105a may be provided adjacent to each other such that the stoppers 105a are either placed side by side or one below another. In case of more than two stoppers 105a, the stoppers 105a may either be positioned in an equidistant manner following a pre-defined pattern or positioned randomly.
[0072] Though the stoppers 105a are shown to be protruding from the inner faces 103c of the wings 103, the stoppers 105a may alternatively/additionally protrude from the outer surface 101d of the holder 101.
[0073] In another embodiment, each inner face 103c includes a stopper 105b in the form of a half three-dimensional cylinder protruding from the inner face 103c towards the free end 103a as illustrated in figure 2c. The number of stoppers 105b on each of the wings 103 may be increased. For example, figure 2d includes two spaced apart stoppers 105b on each of the wings 103. Though figure 2d depicts two adjacently placed stoppers 105b that are positioned one below another, the stoppers 105b may also be placed side by side. Likewise, in case of more than two stoppers 105b, the stoppers 105b may either be positioned in an equidistant manner following a pre-defined pattern or positioned randomly.
[0074] Though the stoppers 105b are shown to be protruding from the inner faces 103c of the wings 103, the stoppers 105b may alternatively/additionally protrude from the outer surface 101d of the holder 101.
[0075] In yet another embodiment, each inner face 103c include a longitudinally protruding stopper 105c that is in a shape of a three-dimensional half tear drop as illustrated in Figure 2e. The number of stoppers 105c on each of the wings 103 may be increased. In case of two stoppers 105c, the stoppers 105c may be provided adjacent to each other such that the stoppers 105c are either placed side by side or one below another. In case of more than two stoppers 105c, the stoppers 105c may either be positioned in an equidistant manner following a pre-defined pattern or positioned randomly.
[0076] Though the stoppers 105c are shown to be protruding from the inner faces 103c of the wings 103, the stoppers 105c may alternatively/additionally protrude from the outer surface 101d of the holder 101 to restrict the maximum displacement of the wings 103 towards the central axis ‘x’.
[0077] As mentioned above, the one or more stoppers of the present invention can also protrude from the outer surface 101d of the holder 101. In an embodiment, the outer surface 101d of the holder 101 may include at least one stopper 105d in the form of a ring extending along the outer circumference of the holder 101 as illustrated in figures 2f and 2g. Though the stopper 105d is shown to be in the form of a continuous ring, the ring may alternatively be discontinuous.
[0078] Figure 2f illustrates a single stopper 105d protruding from the holder 101 near the top end 101a of the holder 101. Though the stopper 105d is shown to protrude from the holder 101 near its top end 101a, the location of the stopper 105d may be varied. Figure 2g depicts two stoppers 105d spaced apart along the central axis ‘x’, one protruding at the top end 101a while the other protruding below the top end 101a of the holder 101. In case of more than two stoppers 105d, the stoppers 105d may either be positioned in an equidistant manner following a pre-defined pattern or positioned randomly.
[0079] The stoppers 105d may be positioned in a manner that the stoppers 105d are perpendicular to the central axis ‘x’. Alternatively, the stoppers 105d may be angled with respect to the central axis ‘x’.
[0080] Though the stoppers 105d are shown to protrude from the outer surface 101d, the stoppers 105d may alternatively/additionally protrude from the inner faces 103c of the wings 103.
[0081] In another embodiment as shown in figure 2h, the stoppers 105e in the form of longitudinal triangular prism may protrude from the outer surface 101d of the holder 101 longitudinally along the central axis ‘x’. The disposition of the stoppers 105e may be such that the stoppers 105e are positioned on a portion of the outer surface 101d of the holder 101 that faces the inner face 103c of the wings 103. In an embodiment, the number of such stoppers 105e may be equivalent to the number of wings 103. Alternatively, the number of stoppers 105e may be more than the number of wings 103. Though the stoppers 105e are positioned along the central axis ‘x’, the stoppers 105e may be angled with respect to the central axis ‘x’.
[0082] Though the stoppers 105e are shown to protrude from the outer surface 101d, the stoppers 105e may alternatively/additionally protrude from the inner faces 103c of the wings 103.
[0083] In yet another embodiment, the function of the stoppers is performed by the tapered holder 101h as illustrated in Figure 2b which helps to restrict maximum displacement of the wings 103 towards the central axis ‘x’ thereby allowing constrained flexing of the wings 103.
[0084] It should be noted that the above embodiments have been described as singular possibilities, however, one or more of the above embodiments of the stoppers may co-exist in a single centralizer 100 at a given time. All such combinations are within the scope of the present invention.
[0085] For example, the centralizer 100 may include three wings 103. One of the wings 103 may be provided with three stoppers 105a while the remaining wings 103 may be provided with two stoppers 105b.
[0086] Likewise, the centralizer 100 may include four wings 103. Two of the wings 103 may be provided with a single stopper 105c each while the remaining two wings 103 may be devoid of any stoppers. However, the outer surface 101d of the holder 101 facing the remaining two wings 103 may be provided with stoppers 105e.
[0087] 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. , C , Claims:WE CLAIM
1. A distal stem centralizer (100) for an intramedullary prosthesis (10), the distal stem centralizer (100) comprising:
a holder (101) for receiving a tip of a distal segment (b2) of a prosthesis (10), the holder (101) disposed along a central axis ‘x’ of a distal stem centralizer (100), the holder (101) includes an outer surface (101d);
at least two wings (103) projecting from the outer surface (101d) of the holder (101) at a pre-defined angle ‘B’ with respect to the central axis ’x’, the at least two wings (103) being circumferentially spaced apart, each of the at least two wings (103) having a free end (103a) and an attached end (103b) coupled to the outer surface (101d) of the holder (101), the free end (103a) being heighted above the holder (101) to cause flexing of the wings (103) towards the central axis ‘x’, the at least two wings (103) having an inner face (103c); and
at least one stopper (105a-105e) protruding from at least one of, the inner face (103c) and/or the outer surface (101d), wherein the at least one stopper (105a-105e) positioned in such a way that the at least one stopper (105a-105e) lies between each wing (103) of the at least two wings (103) and the holder (101) to restrict maximum displacement of the wings (103) towards the central axis ‘x’ thereby allowing constrained flexing of the wings (103).
2. The distal stem centralizer (100) for the intramedullary prosthesis (10) as claimed in claim 1 wherein, the at least two wings (103) are placed at a pre-defined angle ‘A’ with respect to each other.
3. The distal stem centralizer (100) for the intramedullary prosthesis (10) as claimed in claim 1 wherein, the free end (103a) of each of the at least two wings (103) is bent inwardly towards the inner face (103c) at a pre-defined angle ‘C’ to maximize the surface area of the wings (103) in contact with a medullary canal ‘IC’ while insertion/implantation of the prosthesis (10).
4. The distal stem centralizer (100) for the intramedullary prosthesis (10) as claimed in claim 1 wherein, the at least one stopper includes one or more stoppers (105a), each in the form of a bumped notch having a steep slope.
5. The distal stem centralizer (100) for the intramedullary prosthesis (10) as claimed in claim 1 wherein, the at least one stopper includes one or more stoppers (105b), each in the form of a half three-dimensional cylinder.
6. The distal stem centralizer (100) for the intramedullary prosthesis (10) as claimed in claim 1 wherein, the at least one stopper includes one or more longitudinally protruding stoppers (105c), each in a shape of a three-dimensional half tear drop.
7. The distal stem centralizer (100) for the intramedullary prosthesis (10) as claimed in claim 1 wherein, the at least one stopper includes one or more stoppers (105d), each in the form of a ring.
8. The distal stem centralizer (100) for the intramedullary prosthesis (10) as claimed in claim 1 wherein, the at least one stopper includes one or more stoppers (105e), each in the form of a longitudinal triangular prism positioned along the central axis ‘x’.
9. The distal stem centralizer (100) for the intramedullary prosthesis (10) as claimed in claim 1 wherein, the distal stem centralizer (100) is made of a bio-compatible material or a bio-absorbable material.
10. A distal stem centralizer (100) for an intramedullary prosthesis (10), the distal stem centralizer (100) comprising:
a holder (101h) for receiving a tip of a distal segment (b2) of a prosthesis (10), the holder (101h) disposed along a central axis ‘x’ of a distal stem centralizer (100), the holder (101h) includes an outer surface (101d);
at least two wings (103) projecting from the outer surface (101d) of the holder (101h) at a pre-defined angle ‘B’ with respect to the central axis ’x’, the at least two wings (103) being circumferentially spaced apart, each of the at least two wings (103) having a free end (103a) and an attached end (103b) coupled to the outer surface (101d) of the holder (101), the free end (103a) being heighted above the holder (101h) to cause flexing of the wings (103) towards the central axis ‘x’, the at least two wings (103) having an inner face (103c); and
wherein the outer surface (101d) of the holder (101h) being tapered from a top end (101a) to a bottom end (101b) of the holder (101h) to restrict maximum displacement of the wings (103) towards the central axis ‘x’ thereby allowing constrained flexing of the wings (103).