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EP-4081167-B1 - METHOD OF MANUFACTURING MEDICAL IMPLANT

EP4081167B1EP 4081167 B1EP4081167 B1EP 4081167B1EP-4081167-B1

Inventors

  • MINOCHA, Dr. Pramod Kumar
  • KOTHWALA, Deveshkumar Mahendralal
  • DAVE, Arpit Pradipkumar

Dates

Publication Date
20260513
Application Date
20200312

Claims (15)

  1. A method of manufacturing an implant (100), the method comprising: a. preparing a template assembly (20), the template assembly (20) being made entirely from wax; b. providing a lamination layer over the outer surface of the template assembly (20) resulting in a laminated template assembly (20'), the lamination layer 'LL' being composed of at least one polymer dissolved in one or more solvents; c. preparing a mold (30) by providing one or more coating layers of a pre-defined coating material over the laminated template assembly; d. providing pre-dried sand over the mold (30) to form a sand coated mold (30b); e. de-waxing and baking the sand coated mold (30b) for melting out the template assembly (20) to form a de-waxed mold (30c); f. pouring a pre-defined casting material over the de-waxed mold (30c) to form a casted mold; g. cooling and solidifying the casted mold to form a casted implant (30e); and h. heat treating and finishing the casted implant (30e) to form an implant (100).
  2. The method of manufacturing an implant as claimed in claim 1 wherein, the preparing the template assembly (20) includes fabricating a template assembly (20) using fused deposition modelling.
  3. The method of manufacturing an implant as claimed in claim 1 wherein, the preparing the template assembly (20) includes preparing a customized template assembly (20) using one or more anatomical characteristics derived from simulation of a radiological imaging technique.
  4. The method of manufacturing an implant as claimed in claim 3 wherein the one or more anatomical characteristics include one or more of thickness, curvature and/or size of an implantation site.
  5. The method of manufacturing an implant as claimed in claim 1 wherein the wax may include one or more of paraffin wax, bees wax, montan wax, carnabua wax or a blend of wax.
  6. The method of manufacturing an implant as claimed in claim 1 wherein providing the lamination layer 'LL' includes first providing an adhesive coat 'AC' over the template assembly (20).
  7. The method of manufacturing an implant as claimed in claim 6 wherein the adhesive coat 'AC' is composed of one or more resins dissolved in one or more solvents.
  8. The method of manufacturing an implant as claimed in claim 6 wherein the adhesive coat 'AC' includes a thickness ranging between 2µm and 6µm.
  9. The method of manufacturing an implant as claimed in claim 1 wherein the lamination layer 'LL' includes a composition having LDPE in a concentration of 5wt% - 40wt% dissolved in 50 - 90 wt% of solvents.
  10. The method of manufacturing an implant as claimed in claim 1 wherein the lamination layer 'LL' includes a thickness ranging between 10µm and 80µm.
  11. The method of manufacturing an implant as claimed in claim 1 wherein the preparing the mold (30) includes providing one or more coating layers having a thickness ranging between 03 mm to 10 mm.
  12. The method of manufacturing an implant as claimed in claim 1 wherein the pre-defined coating material includes ceramic slurry.
  13. The method of manufacturing an implant as claimed in claim 1 wherein the de-waxing involves autoclaving the sand coated mold (30b) at a temperature ranging from 80°C to 200°C.
  14. The method of manufacturing an implant as claimed in claim 1 wherein the baking involves a temperature ranging between 700°C to 1200°C.
  15. The method of manufacturing an implant as claimed in claim 1 wherein the pre-defined pouring material is molten cobalt chromium molybdenum alloy; optionally wherein the cooling and solidifying includes air cooling the casted mold for 1-2 hours followed by water jet cooling of the casted mold; optionally wherein the heat treating and finishing includes hipping and annealing of the casted implant (30e); and optionally wherein the heat treating and finishing is followed by surface treating the implant (100).

Description

FIELD OF INVENTION The present invention relates to medical implants, more specifically, the present invention relates to a method of preparing the medical implant. BACKGROUND Osteoarthritis and rheumatoid arthritis have become more common in the elderly population suffering from chronic joint disease and injuries caused by trauma. In order to address osteoarthritis and/or rheumatoid arthritis, total knee replacement surgery has proved to be an effective treatment in the current days. Knee replacement surgery involves removing an unhealthy portion of a femoral bone and tibial bone and replacing it with a metal prosthetic implant. The conventional implants are fabricated using standard dimensions. The replacement of such conventional implants requires removal of diseased bone as well as unaffected bone (healthy bone) using various bone removal tools so that the standard sized implant can fit an implantation site. This intensive cutting process may lead to intense trauma and pain for a patient during the post-operational and recovery phases of surgery. In fact, it is documented that approximately 20% of total knee patients are not satisfied after the procedure because of their painful experiences which might last even for a long time. In addition, the post-operative treatments for attending to such pain are expensive and have least chances of optimal recovery. Moreover, there may be possibilities of dislocation of the knee implant segments as it might not fit with the bones perfectly. Further, generally, the conventional implants are manufactured using metal 3D-printing technique. The implants manufactured through this technique have poor surface finish since the said process includes deposition of metal alloy layer by layer. (Ref: 3D Printing: Applications in evolution and ecology; Matthew Walker, Stuart Humphries; Ecology and Evolution. 2019; 9: 4289-4301.) The layer by layer deposition results in increased porosity as small cavities are formed within the part which leads to decrease in density of the 3D-printed implant. This affects the mechanical properties of the implants wherein decreased density makes the implants prone to cracks and damages under high loads and cyclic stresses. Apart from the above procedure, methods involving wax template for fabrication of metal implants are also conventionally known. In such methods, one or more layers of coatings over a wax template are applied. Such coatings are approximately 4 - 6 mm thick so that the wax template can bear the molten metal at later stage. The application of multiple coatings over the fragile wax template results in development of micro-cracks and/or dots due to presence of viscous slurry coating with varying particle sizes having intensive and thick coating. Also, the wax template is often deformed by this procedure. As a result, such processes form implants having higher rejection rate. It is estimated that approximately 600gms of precious medical grade metals like Co-Cr Alloys, Co - Cr - Mo Alloys, Titanium alloys etc. are wasted per every metal implant rejected. Thus, a higher rejection rate of conventional implants results in more wastage of metals (around thousands of kilograms of metal). The resulting conventional metal implants as derived from the above disclosed processes, are vulnerable to deterioration caused by scratching, wear or damage through the corrosive processes that occur in situ once installed. 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. 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. A method to rapidly make castings is disclosed in prior art having publication number US6446697B1. The method includes the steps of graphically designing a solid model, dividing the model into blocks, carving a wax solid for each block, assembling the wax solids, forming a ceramic shell around the wax solids, heating to remove the wax from the ceramic shell, and pouring molten metal into the ceramic shell. However, the castings produced form the said method includes residual wax, dot impressions and micro cracks. Another method to produce open-celled metal structures is disclosed in a prior art having publication number US5016702A. The method includes cleaning an open pored plastic substrate formed over a wax foundation, applying a layer of strengthenin