Claims:WE CLAIM:
1. A method for treating a surface of an implant, the method comprising:
a. cleaning surface of an implant;
b. annealing the cleaned implant in a furnace at a temperature ranging from 1000°C to 1200°C in the presence of an inert gas;
c. descaling of the annealed implant using one or more descaling agents or solutions to remove debris;
d. surface treating the descaled implant using one or more reagents;
e. reagent reacts with the metal particles on the surface of the implant to form an oxide layer on the implant; and
f. coating the treated surface of the implant with a coating layer.
2. The method for treating the surface of the implant as claimed in claim 1 wherein the descaling agents or solutions include one or more of purified water, hydrofluoric acid, nitric acid, sodium tetrafluoro borate, and sulfamic acid solution.
3. The method for treating the surface of the implant as claimed in claim 1 wherein the reagents include acetic acid (C2H4O2), citric acid (C6H8O7), a mixture of sodium tripolyphosphate, sodium alkylbenzene sulfonate and/or tetrasodium pyrophosphate or hydrochloric acid (HCL).
4. The method for treating the surface of the implant as claimed in claim 1 wherein the coating comprises
• cleaning a coating material of Titanium niobium with an alkaline solution;
• rinsing the cleaned coated material with purified water; and
• ionizing the coating material of Titanium niobium in a chamber at a predefined temperature resulting in deposition of the coating layer of Titanium niobium nitride on the implant.
5. The method for treating the surface of the implant as claimed in claim 1 wherein the coating layer includes metal nitrides selected from TiN, TiNbN, CrN, TiAlN, and ZrN.
6. The method for treating the surface of the implant as claimed in claim 1 wherein the coating includes cleaning the coating material with one or more of alkaline solution, and purified/distilled water in order to remove contamination.
7. The method for treating the surface of the implant as claimed in claim 1 wherein thickness of the coating layer ranges from 2 µm to 8 µm.
8. The method for treating the surface of the implant as claimed in claim 1 wherein the method is performed in a clean and sterile environment.
9. The method for treating the surface of the implant as claimed in claim 1 wherein the method further comprises packaging of the coated knee implant using a sleeve package device. , 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:
METHOD TO IMPROVE ADHESION PROPERTY OF TITANIUM NIOBIUM NITRIDE COATING ON KNEE IMPLANT
2. APPLICANT:
Meril Life Sciences Pvt. Ltd., an Indian company of the address Survey No. 135/139 Bilakhia House, Muktanand Marg, Chala, Vapi- 396191, Gujarat

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 medical implants, more specifically, to a method of treatment of a surface of an implant to enhance adhesion of a coating on the surface of the implant.
BACKGROUND
[002] Medical implants have been developed to help people of all ages specifically, elderly who suffer from swelling, stiffness and/or pain in the joints caused by various bone injuries or diseases including osteoarthritis, rheumatoid arthritis, gout, bursitis, bone tumor, cartilage tear etc. Among several joints of the body, the knee joint is the main joint that is affected by an injury as it is the largest joint of the human body and helps in performing various physical activities. Hence, any damage or disease caused in the knee joint necessitates replacement of the knee with an implant.
[003] Artificial knee implants are usually made from metal and once installed, are vulnerable to deterioration caused by scratching, wear or damage through the corrosive processes that occur in situ. Damaged implants may exhibit diminished performance, and in some cases, must be repaired or replaced. Implants including metallic substrates having materials such as steel, cobalt, titanium, and alloys thereof, are also vulnerable to damage or mechanically-assisted corrosion that can lead to loss of structural integrity, scratching or increased wear rates and reduction of implant performance. Traditional approaches for improving the scratch and wear-resistance of metallic orthopaedic implants include surface treatments such as ion implantation, gas nitriding, high temperature oxidation, coating techniques, etc.
[004] However, certain limitations such as inability, poor adherence of coatings to underlying substrates, and/or economic feasibility may abridge the utility of some of these methods. Hence, there is a need to develop an efficient implant surface treatment process that would result in an implant surface that can circumvent the conventional issues.
SUMMARY
[005] The present invention relates to a method of surface treating an implant prior to coating the implant with a coating material. The instant method of surface treating an implant addresses the challenges posed by the untreated implants and their adhesion properties with the coating material. The surface treatment of the present invention involves a series of steps that includes cleaning of the untreated implant. The cleaned implant is further annealed, descaled and surface treated under the required temperature conditions and involving various reagents.
[006] Further, the treated implant of the present invention is coated using arc physical vapor deposition method in a substantially rectangular housing. The method of coating the treated implant is performed in a clean and sterile environment thus resulting in a smooth and polished surface.
[007] The coated implant is subsequently enclosed inside a packaging sleeve and placed in a packaging device containing a femoral retainer, an outer femoral tray and inner femoral tray. The packaging of the coated implant helps to deliver the coated implant at the desired location without hampering the quality of the coated implant during storage or transportation.
[008] 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 THE DRAWINGS
[009] The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended 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.
[0010] Fig. 1 depicts a rough surface and coated surface of the implant without surface treatment in accordance with an embodiment of the present invention.
[0011] Fig. 2 depicts a flow chart depicting the process of coating the knee implant in accordance with an embodiment of the present invention.
[0012] Fig. 3a depicts the PVD coating device carrying the substrate in accordance with an embodiment of the present invention.
[0013] Fig. 3b shows an expanded view of the rectangular housing of FIG. 3a in accordance with an embodiment of the present invention.
[0014] Fig. 3c illustrates coated implant placed in packaging tray with top protective sleeve and bottom protective sleeve in accordance with an embodiment of the present invention.
[0015] Fig. 4 shows a surface treated implant and coated surface of the implant in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0016] 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.
[0017] 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 merely 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.
[0018] The term “Implant” refers to a substitute for the damaged bone, tissue etc., which is fabricated artificially to match the damaged portion of the bone, and which is attached to a patient undergoing knee replacement surgery. The term “alloy” refers to a metal made by combining two or more metallic elements, particularly to provide greater strength or resistance to corrosion.
[0019] In accordance with the present disclosure, a method for surface treatment of an implant surface is disclosed. The method of the present invention helps to improve adhesion properties of the implant surface. Various steps involved in the method of surface treatment include mechanical treatment, chemical treatment, heat treatment, coating, etc. which help to enhance adherence of the coating on the surface of the implant. Further, owing to the treated implant surface, an ultra-hard, smooth, mirror polished surface with improved adhesion of coating on the implant is obtained. Further, the process of the present invention results in a surface that is free of any contamination/debris and has an oxide layer formed on its surface that result in excellent adhesion of the coating layer on the treated surface of the implant. Thus, the oxide layer helps in enhanced life of the coating layer.
[0020] The step of heat treatment or annealing of the implant at austenitizing temperature aligns the grain structure of the implant thus reducing stress in the implant. This helps to minimize the roughness of the surface and helps to ensure excellent adhesion of a coating layer on the surface of the implant and thus achieves uniform and mirror polished coating with superior abrasion resistance.
[0021] Now specifically referring to figures, FIG. 1 depicts the conventionally coated implant without surface treatment. The uncleaned implant 10a with a rough surface (without coating) and the finally coated implant 10b have been depicted in FIG.1 of the present invention. The said coated implant 10b without any treatment results in reduced adherence of the coating with the implant 10b which thereby causes delamination of the coating and leads to formation of cracks on the coating surface of the implant 10b.
[0022] FIG.2 illustrates a flow chart depicting the process involved in the method of surface treatment of the implant 100 (not shown in FIG.2) of the present invention. The implant 100 thereof can be any suitable implant required to treat one or more joint injuries or diseases not limited to osteoarthritis, rheumatoid arthritis, gout, bursitis, bone tumor, cartilage tear etc. Suitable medical implant 100 in accordance with the present invention are the implants designed and coated for orthopaedic purposes like for hip, knee, ankle joint, shoulder joint, including elbow, spine etc.
[0023] In an exemplary embodiment of the present invention, the implant 100 disclosed is a knee implant. The said knee implant may be formed of a suitable material that provides strength and rigidity to the joints. Suitable materials for manufacturing of the said knee implant include metals and/or composite materials such as metals and/or metal alloys including cobalt chromium molybdenum alloy (CoCrMo), cobalt chromium alloy (CoCr), titanium alloys, commercially pure TI (cpTi), medical grade stainless steels, tantalum and tantalum alloys, Nitinol (“NiTi”), ASTM F-75 CoCr alloy, or Arcam. Further, some of the ceramic materials, e.g., aluminum oxide or alumina, zirconium oxide or zirconia, compact of particulate diamond, and/or pyrolytic carbon may be used for manufacturing the implant 100. Some other suitable materials may include one or more biomaterials including Ti—Nb—Zr, Ti-Al-V, tantalum, etc. The biomaterials may be used in powdered form which facilitates specific biomaterial configurations for the patient-specific knee implant, in a cost effective manner. The knee implant used in the present invention is made from cobalt chromium molybdenum alloy (CoCrMo). The said implant 100 may be accurately and specifically designed and manufactured by one or more methods which may include additive manufacturing or three-dimensional printing technology, laser sintering or electron-beam melting, precision CNC (Computerized numerical control) machining, metal casting technique, investment casting technique, etc.
[0024] Prior to application of the coating on a requisite surface, a series of steps are performed to make the surface coating ready, for example, mechanical treatment, chemical treatment, heat treatment or combination thereof. The term ‘surface coating ready’ in the context of the present invention may imply a surface that is obtained post treatment of a rough surface of the implant 100. Such surface obtained post treatment promotes adhesion of the coating.
[0025] In the context of the present invention, the method has been described on an exemplary implant 100 made of CoCrMo alloy. However, the method can be applicable to implants made of other materials as provided in the earlier part of the description.
[0026] In an embodiment of the present disclosure, the method of surface treatment 200 of the implant 100 along with the steps involved in the coating on the said implant 100 is disclosed. The steps involved in the treatment process are illustrated in FIG.2 of the present invention in detail. At first step 201, a mechanically processed implant 100 having a rough surface is cleaned with purified water to remove excess debris or unwanted particles from the surface of the implant 100.
[0027] At next step 203, annealing is performed. The cleaned implant 100 is subjected to heat and vacuum treatment. The process of annealing may be performed in a closed housing like a furnace or a chamber. The temperature and pressure conditions of the furnace are suitably maintained during the complete annealing step. The temperature of the furnace disclosed for the annealing process of the present invention ranges from 1000°C to 1200°C and more preferably from 1050°C to 1150°C.
[0028] In addition to temperature, the annealing process involves treatment of the implant 100 in the presence of an inert gas or vacuum in the said housing. One or more inert gases may be used for the implant 100 treatment which may include argon, nitrogen, helium, etc. In accordance with the present invention, said inert gas is Nitrogen gas and the treatment is performed at 1 milibar pressure. Further, the above pressure and temperature conditions inside the furnace may be maintained for a predefined time i.e. for approximately 10 minutes to 5hrs more preferably from 50 minutes to 3hrs after which the said furnace is allowed to cool to 100°C.
[0029] The said annealed implant 100 is additionally subjected to ultrasonic cleaning with purified water at a temperature ranging between 45°C to 65°C and more preferably from 50°C to 60°C. Thus, the annealing process disclosed at step 203 of the present invention provides a treated implant 100 with an equal structured metal alloy surface defining a specific grain size of the CoCrMo alloy on the surface. Moreover, the above mentioned steps performed on the said implant 100 are not only restricted to CoCrMo alloy implants rather, implants made from alloys like cobalt chromium, titanium cobalt etc. can also be treated.
[0030] At the next step 205, in accordance with the present invention, the annealed implant 100 is further subjected to descaling process. The said descaling process leads to removal of the unwanted debris from the surface of the annealed implant 100 thus creating a smoother surface. The process of descaling of the said implant 100 utilizes one or more descaling agents or solutions selected from purified water, hydrofluoric acid, nitric acid and/or sodium tetrafluoro borate, sulfamic acid solution, etc. The descaling solution used for the treatment in the present invention is a combination of concentrated nitric acid, hydrofluoric acid and water in specific quantities. The concentration of nitric acid in the descaling solution ranges from 15% v/v to 20% v/v, hydrofluoric acid ranges from 4.0% v/v to 8.0% v/v and that of water ranges from 70% v/v to 80% v/v. The said descaling process involves immersing the annealed implant 100 in the descaling solution disclosed above and subjected to ultrasonic wave treatment for a desired time i.e. 200 to 240 minutes at temperature ranging from 65°C to 70°C. Further, the said treated implant 100 is followed by washing of the immersed implant 100 with purified water and subsequently drying.
[0031] At step 207, the surface treatment of the above mentioned descaled implant 100 is performed. The said implant 100 thereof is treated with one or more reagents. The said reagents may include but not limited to acetic acid (C2H4O2), citric acid (C6H8O7), a mixture of sodium tripolyphosphate, sodium alkylbenzene sulfonate and/or tetrasodium pyrophosphate or hydrochloric acid (HCL). The surface treatment reagent used in the embodiment of the present invention is citric acid and the concentration of the said reagent may range from 05% to 10%. The said reagent(s) reacts with the metal particles on the surface of the implant 100 to form an oxide layer over the implant 100 surface. The said oxide layer results in a corrosion free implant 100. The entire process disclosed above is carried out in a clean room.
[0032] Proceeding further, in step 211, the surface of the treated implant 100 is coated. The present invention is directed towards a thin layer of coating that is provided on the treated surface of the said implant 100 (referred to as the substrate material in FIG. 3a) of the said implant 100. The scope of the present invention also extends to having multiple layers of coating. In accordance with an embodiment of the present invention, various materials that may be involved in the said coating process are disclosed. One or more coating materials 101 referred to as the base material in FIG.3a of the present invention may include titanium niobium (TiNb), titanium (Ti), chromium (Cr), titanium aluminium (TiAl), zirconium (Zr), etc. In an exemplary embodiment, the coating material 101 includes titanium niobium (TiNb).
[0033] In an embodiment of the present invention, said (TiNb) compound is treated prior to coating on the implant 100 surface. The steps of treatment involve washing of the coating material 101 with an alkaline solution for at least 03 minutes under temperature ranging from 70°C to 80°C. The alkaline solution used for washing the titanium niobium material is preferably a basic solution having pH 9.0 to 10.0 and more preferably 9.4 to 9.6. Further, said compound is rinsed with distilled water and dried in a cabinet air dryer with air flow rate at around 80°C temperature. After drying process, coating material 101 is placed on the rotatory device 107 in the chamber 103 of the PVD system (described in Fig 3a).
[0034] It is to be noted that a hygienic and clean environment should be maintained in the room or the area where the said coating process is performed to ensure avoidance of any foreign particle intervention in the process.
[0035] Further, the thickness of the coating layer may range from 2µm to 8µm and more preferably from 3µm to 6µm. The hardness of the coating layer may range from 2000HV to 2800HV, more preferably 2200HV to 2600HV. The roughness of the coating layer ranges from 0.03 µm to 0.07 µm and more preferably 0.04 µm to 0.06 µm, which helps to achieve uniform and smooth coating layer on the implant 100. Further, the micro-hardness of the coating layer ranges 2000 HV to 2800 HV, more preferably 2200 HV to 2600 HV.
[0036] The deposition of the said coating layer on the surface treated implant 100 may be performed using a technique that provides desired layer or coating characteristics. The characteristics include without limitation desired thickness profile, adhesion properties, etc over the implant 100. The techniques include without limitation physical vapor deposition, chemical vapor deposition, cathodic arc PVD, steered cathodic arc PVD, filtered cathodic arc PVD, plasma-assisted PVD, laser-assisted PVD, DC magnetron sputtering, RF magnetron sputtering, unbalanced magnetron sputtering, high power impulse magnetron sputtering, chemical vapor deposition (CVD), plasma-assisted CVD, laser-assisted CVD, plasma- enhanced CVD, photo-enhanced CVD, metal-organic CVD, atmospheric pressure CVD, ion plating, pulsed laser deposition, atomic laser deposition, cold spray, thermal spray, solution plasma spray, solution precursor plasma spray, plating, reactive evaporation, and/or reactive ion beam assisted deposition. Any combination or hybrid of two or more of these techniques may be used. In an embodiment of the present invention, physical vapor deposition (PVD) is used for depositing the coating layer on the surface of the implant 100.
[0037] In accordance with the present invention, the PVD coating method may be selected from arc evaporation, thermal evaporation sputtering or ion plating. In an embodiment of the present invention, PVD coating technique is cathodic arc evaporation. The coating of surface treated implant 100 accomplished through the process of physical vapor deposition results in an implant 100 with high biocompatibility, allergy prevention, good chemical stability and superior abrasion resistance, high flexion to segments, hardness and durability.
[0038] The said cathodic arc PVD coating process and system depicted in FIG.3a of the present invention may be performed in a chamber 103 i.e. substantially rectangular housing, where one or more environmental parameters may be maintained. The said parameters may include chamber temperature and pressure, voltage, time for which the said process is carried out, etc.
[0039] FIG. 3b discloses an expanded view of the rectangular housing of FIG. 3a in which the said process is performed.
[0040] The one or more implants are placed on the rotatory device 107 enclosed in the PVD chamber 103 or housing. The said rotatory device 107 provides a planetary rotation movement to the implant 100 thus ensuring equal distribution of the coating material 101 over the implant 100 surface.
[0041] The one or more implant 100 may be located in proximity to a plurality of cathodes. The said cathode 105 holds one or more materials to be deposited on the implant 100 surface. The coating material 101 used in the present invention as discussed above is Titanium niobium (TiNb). Before performing the coating process disclosed in the present invention, the PVD coating chamber 103 is treated with one or more of, vacuum and/or inert gas through ports 103a, 103b and 103c to decontaminate the chamber 103. The inert gas disclosed in the present invention may include without any limitation nitrogen gas. The pressure of the said nitrogen gas inside the chamber 103 may range from 2 to 6 bar and more preferably from 3 to 5 bar. Moreover, along with inert gas treatment, said chamber 103 may be plasma 103d cleaned before initiating the coating process.
[0042] The coating material having TiNb interacts with the inert gas say, nitrogen, present in the chamber to form Titanium niobium nitride (TiNbN). The composition of Titanium niobium nitride (TiNbN) as formed at this step of the present invention is elaborated in Table 1 below.

[0043] Alternately, the amount of niobium in the composition may range from 10% to 50% and more preferably from 20% to 40%. In addition, inert gases including nitrogen may range from 0.01% to 0.05%, more preferably 0.02% to 0.04%.
[0044] Once the cleaning steps are performed, the coating material 101 (TiNb) placed on the cathode 105 may be evaporated by an evaporator 103e maintaining a temperature in the range between 350°C to 500°C, more preferably from 400°C to 460°C in the chamber 103. In addition to the temperature treatment, the current required to generate magnetic field that helps in ignition and ionization of the coating material 101 may be between 55A and 95A, more preferably 60A and 90A. Further, the rotation of the rotatory device 107 maintains a continuous distribution of the coating material 101 over the implant 100 surface. The speed of the rotatory device 107 ranges from 0.5rpm to 4.5rpm and more preferably from 1.5rpm to 3.5rpm (rotation per minute).
[0045] Additionally, in the present embodiment, once the coating is provided, the coated implant 100 of the said invention is allowed to cool down to the ambient temperature before final cleaning process is initiated. The final cleaning process is performed to remove the residual particles if any on the surface of the coated implant 100. The process of final cleaning involves washing the coated implant 100 with purified water at ambient temperature for 03 minutes to 07 minutes. Further, hot water at temperature 85°C to 90°C is used for 15 minutes to 20 minutes to clean the coated implant 100 in the subsequent step. Cleaning with hot water is repeated again over the coated implant 100 for 03 minutes to 07 minutes at the ambient temperature. Further, the washed coated implant 100 is dried at the temperature ranging from 115 °C to 125 °C for 45 minutes to 50 minutes. The TiNbN coated implant 100 is left for cooling for 03 to 07 minutes at the ambient temperature ranging from 22°C to 25°C temperature.
[0046] Proceeding further from step 211 in FIG. 3c, the final packaging step 213 (sleeve packaging) of the TiNbN coated implant 100 is performed to deliver the said coated implant 100 to the desired location without hampering the quality of the coated implant 100 during storage or transportation. The packaging of the coated implant 100 is carried out in three enclosures or devices designed to specifically hold the coated implant 100 during transportation. The said device as depicted in FIG.3c of the present invention includes an inner femoral tray (not shown in FIG.3c), femoral retainer 109 and outer femoral tray 111 which are made from one or more medical grade polymer sheets including polypropylene (PP), polyethylene (PE), polystyrene (PS), acrylonitrile butadiene (ABS), polyvinyl (PV) and polyethylene terephthalate (PET). To ensure protection of the said implant 100 during transportation, the coated implant 100 is placed or wrapped in a sleeve or sheet made from polyvinyl (PV) (marked as top 113a and bottom 113b sleeves in FIG.3c) and thus helps to secure the implant 100. To ensure removal of the unwanted debris or particles the said packaging process is carried out in laminar air flow.
[0047] FIG. 4 of the present invention illustrates a surface treated clean implant 40a and the coated implant 40b after surface treatment.
[0048] Further, the packaged coated implant 100 is subjected to a sterilization process at step 215. The sterilization can be done using any radiation sterilization technique like e-beam radiation sterilization or gamma sterilization. In present invention, the coated implant 100 is sterilized using gamma radiation sterilization. The coated implants are packaged in corrugated boxes for gamma sterilization.
Some of the examples have been illustrated below:
Example 1 (prior art):
[0049] The mechanically processed cobalt chromium molybdenum alloy implant 100 is coated with TiNbN utilizing the arc evaporation technique of physical vapor deposition. The TiNbN material is washed with alkaline solution, dried and mounted over the rotation system of coating chamber 103. The implant 100 is mounted on the rotatory device 107 and subjected to PVD coating wherein the rotation per minute of planetary frame is 02 rpm, nitrogen gas pressure is set at 04 bar, temperature of chamber 103 is maintained around 450°C and current required to generate magnetic field is set between 60A and 90A. The TiNbN coated implant 100 is allowed to reach at 85°C temperature and then washed with purified water multiple times for cleaning any residual particles present on the surface. The coated implant 100 is then analyzed for adhesion properties of coating layer over implant 100. The adhesion properties are analyzed by subjecting the coated implant 100 to surface grinding abrasion test for around 15 minutes. It was observed that during grinding process the TiNbN coating layer partially delaminates with a crack formation on the surface of the implant 100 and almost 40-50% of the coating layer failed to adhere with the implant 100.
Example 2:
[0050] A mechanically processed CoCrMo alloy implant 100 is subjected to descaling and surface treatment prior to coating the implant 100 with TiNbN. Firstly, the implant 100 is subjected to descaling process where the said implant 100 is cleaned using the mixtures of descaling agents that includes purified water, hydrofluoric acid and nitric acid solution followed by multiple washes with purified water. Secondly, a surface treatment process is carried over the descaled implant 100 where the implant 100 is treated with citric acid and/or Alconox® powder to achieve smooth and clean surface. Further, the descaled and surface treated implant 100 is subjected to PVD coating wherein the parameters for the coating are set as mention in example 1. The adhesion test is performed on the coated implant 100 thereof. The adhesion properties were analyzed by subjecting the coated implant 100 to surface grinding abrasion test for around 15 minutes. It was observed that during the grinding process the TiNbN coating layer partially delaminates with a crack formation on the surface of the implant 100 and 20%-25% of the coating layer failed to adhere with the implant 100 surface.
Example 3 (present invention):
[0051] A mechanically processed CoCrMo alloy implant 100 is initially subjected to annealing process before coating TiNbN over the implant 100. The annealing process is performed on implant 100 prior to descaling and surface treatment processes. The annealing process is carried out in a furnace where the temperature is maintained at 1150°C. Additionally, the vacuum is maintained in the furnace with a pressure below 01 mbar and the hold time for the said annealing process of the implant 100 is at least 60 minutes. The implant 100 is further cooled and cleaned using purified water. This annealed and cleaned implant 100 is further subjected to descaling and surface treatment processes. The annealed, descaled and surface treated implant 100 is then subjected to TiNbN coating using PVD method wherein, the parameters for the coating are set as mentioned in example 1. The coated implant 100 is then analyzed for adhesion properties of TiNbN over the implant 100 and the adhesion test was performed. Further, the coated implant 100 is subjected to surface grinding abrasion test for 15 minutes and the property of TiNbN coating over the coated implant 100 was observed. As a result, it was found that 90%-95% of the coating layer adhered to the implant 100 surface. Further, not only did adherence of the coating increase, the coated surface was more smooth and minimal debris were formed through abrasion (or wear or tear) of the adjoining components like a plastic spacer between femoral and tibial components, patellar etc. From the above, it can be easily deciphered that the adhesion properties of the pretreated implant 100 prior to coating were improved as compared to untreated implants.
[0052] Although the invention has been described using a coating of TiNbN, it is to be noted that the teachings of the present invention are applicable in the context of other coatings including but not limited to ZrN, TiN, TiNbN, CrN, and TiAlN.
[0053] The above experimental data suggests that there is a considerable increase in the adhesion of the coating material on the surface treated implant.
[0054] 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.