Patent ID: 12245943

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a detailed description will be given of the present invention in conjunction with the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be embodied in a variety of different forms and is not limited to the embodiments described herein.

In order to clearly explain the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar elements throughout the specification.

In addition, the terms or words used in the present specification and claims should not be construed as being limited to the ordinary or dictionary meanings, and should be understood as having meanings and concepts consistent with the technical spirit of the present invention based on the principle that the inventor may appropriately define the concepts of terms in order to explain the invention in the best way.

FIG.1is a flowchart showing a process of manufacturing a spinal cage for improving a bone union rate according to an embodiment of the present invention,FIG.2shows the cage body before depositing a coating film according to an embodiment of the present invention,FIG.3shows the cage body after depositing the coating film according to an embodiment of the present invention.

As shown in the drawing, the method of manufacturing a spinal cage according to the present invention includes preparing a cage body to be processed including a polymer material (S100), sanding the surface of the cage body roughly by spraying ceramic beads onto the surface of the cage body (S300), and depositing a coating film with a metal material on the surface of the cage body (S600).

The cage body10is a medical device used in spinal fusion, and is inserted between the vertebral bodies to maintain the gap between the vertebral bodies and create a space for the bone to grow into for fusion.

A hollow is formed in the central portion of the cage body10, and this hollow is filled with autograft, allograft, or synthetic bone to promote bone growth.

In the illustrated embodiment, the cage body10is formed in a bullet shape that is long in the front-rear direction, but the present invention is not limited thereto and the cage body may be formed in various shapes such as a flat shape, a curved shape, a disc shape, and the like. The cage body10may be manufactured using an SLM (selective laser melting)-type 3D printer.

The cage body10may include a polymer material as a main component of the cage body10, and may also include various additives or fillers.

The polymer material constituting the cage body10is preferably polyether ether ketone (PEEK).

Polyether ether ketone (PEEK) is a high-performance thermoplastic resin that has mechanical strength and superior chemical resistance at high temperatures and has excellent tensile properties. In particular, polyether ether ketone (PEEK) has similar strength to vertebral bodies, so it may provide stability when used as the cage body10.

The coating film20deposited on the surface of the cage body10is made of a metal material having higher biocompatibility than the polymer material of the cage body10. For example, the metal material of the coating film20is preferably titanium or a titanium alloy.

Titanium is fairly light, weighing equal to or less than half as much as steel, does not rust, and has low thermal and electrical conductivity. A titanium alloy has high specific strength, and exhibits excellent wear resistance and highest corrosion resistance among stainless steel alloys. In particular, titanium or a titanium alloy has high biocompatibility and is therefore suitable for use as a spinal cage.

In the present invention, the coating film20may be deposited using a metal material such as titanium or a titanium alloy on the surface of the cage body10made of a polymer material such as polyether ether ketone (PEEK), thereby simultaneously achieving stability of the polymer material and high biocompatibility of the metal material.

FIG.4shows a sanding process according to an embodiment of the present invention.

The method of the present invention may further include washing the cage body using a neutral detergent containing a surfactant component (S200), after preparing the cage body (S100) and before sanding the surface of the cage body (S300).

In preparing the cage body (S100), processing oil may be left behind on the surface of the cage body10during processing. If this processing oil is not completely removed, deposition performance of the coating film20may remarkably deteriorate in the subsequent deposition process (S600), so processing oil must be removed through washing.

Washing the cage body (S200) before processing is performed using a neutral detergent containing a surfactant component. A surfactant is a material that is activated at the contact surface between materials having different properties, and is used to wash the surface of the cage body10.

Sanding the surface of the cage body (S300) may include processing the surface of the cage body10roughly by spraying ceramic beads30onto the surface of the cage body10, thereby increasing the surface roughness value of the cage body10, which may further increase biocompatibility.

As shown in the drawing, sanding the surface of the cage body (S300) may include filling the inside of a sanding case31with ceramic beads30and spraying the ceramic beads through a nozzle32with high-pressure compressed air to roughen the surface of the cage body10.

Here, the ceramic beads30used in sanding the surface of the cage body (S300) are preferably round ceramic beads.

Beads used in a conventional sanding process are generally made of sharp metal materials. However, when the cage body10made of a polymer material is subjected to sanding (S300) using sharp beads, the beads may become embedded in the surface of the cage body10, making it difficult to remove the beads, and it may be dangerous if the beads enter the human body. Hence, round ceramic beads30are used.

Moreover, the particle size of the ceramic beads30used in sanding the surface of the cage body (S300) is preferably 0.1 to 600 μm. In general, as the surface roughness value of the cage body10increases, the bone union rate (biocompatibility) increases. However, if the surface roughness value is excessively high, performance of coating deposition may decrease.

Therefore, in the present invention, the ceramic beads30have a particle size suitable for maximizing biocompatibility without deteriorating coating performance. If the particle size of the ceramic beads30is less than 0.1 μm, the surface roughness value may be too low and biocompatibility may remarkably decrease, whereas if the particle size of the ceramic beads30exceeds 600 μm, the surface roughness value may be too high, remarkably impairing performance of deposition of the coating film20.

FIG.5is a flowchart showing a first washing process according to an embodiment of the present invention, andFIG.6is a flowchart showing a second washing process according to an embodiment of the present invention.

As shown in the drawings, after sanding the surface of the cage body roughly (S300), the first washing process (S400) and the second washing process (S500) are performed to remove the remaining ceramic beads30from the cage body10.

Specifically, the first washing process (S400) includes subjecting the cage body to first washing using a predetermined washing solution (S410), subjecting the cage body to second washing in distilled water at a predetermined temperature (S420), and subjecting the cage body to third washing using a predetermined washing solution (S430).

The first washing (S410) is performed for about 5 minutes using a washing solution including 100 parts by weight of distilled water and 10 to 50 parts by weight of acetone.

The second washing (S420) is performed for about 5 minutes using 100% distilled water at a temperature of 20 to 90° C.

The third washing (S430) is performed for about 5 minutes using a washing solution including 100 parts by weight of distilled water and 10 to 50 parts by weight of acetone.

When performing the first washing process (S400) in this way, the ceramic beads30remaining on the surface of the cage body10may be removed to some extent, and the second washing process (S500) is subsequently performed.

Specifically, the second washing process (S500) includes subjecting the cage body to fourth washing using ultrasonic waves in a washing water tank containing an alkaline solution (S510), subjecting the cage body to fifth washing by spraying ultrapure water (S520), and subjecting the cage body to sixth washing in a washing water tank containing ultrapure water (S530).

The fourth washing (S510) is performed using ultrasonic waves at a temperature of 10 to 90° C. for about 9 minutes. In the fourth washing (S510), an ultrasonic vibrator (not shown) is installed in the washing water tank to generate vibration, and the generated vibration is transmitted to the alkaline solution to disperse the ceramic beads30on the surface of the cage body10. The alkaline solution contained in the washing water tank may include sodium hydroxide, sodium carbonate, sodium silicate, sodium phosphate, or sodium cyanide.

The fifth washing (S520) is performed using ultrapure water at a temperature of 10 to 90° C. for about 15 minutes. As used herein, the term “ultrapure water” refers to distilled water with electrical conductivity, number of solid particles, number of viable bacteria, organic matter, etc. suppressed to extremely low values, and more specifically, the number of particles with a diameter of 0.1 μm or less per cm3may be 20 or less, and the number of viable bacteria per 100 cm3may be 1 or less.

The sixth washing (S530) is performed using ultrapure water at a temperature of 10 to 90° C. for about 6 minutes. In the sixth washing (S530), the cage body10may be washed with high-temperature ultrapure water to remove the ceramic beads30from the surface thereof, and subsequent drying (S540) may be performed more easily.

The second washing process (S500) may further include drying the cage body at a temperature of 60 to 120° C. for about 8 minutes (S540) after the sixth washing (S530). After completion of the drying (S540), the cage body10is transferred to a deposition device to perform the deposition process (S600).

FIG.7is a flowchart showing the deposition process according to an embodiment of the present invention, andFIG.8shows the deposition process according to an embodiment of the present invention.

As shown in the drawing, a coating film20is deposited with a metal material on the surface of the cage body10(S600) after completion of the first washing process (S400) and the second washing process (S500).

The thickness of the coating film20deposited on the surface of the cage body10is preferably 0.1 to 10 μm. If the thickness of the coating film20is less than 0.1 μm, there may be a very high possibility that the coating is not properly performed, and the coating film20may melt and disappear too quickly. On the other hand, if the thickness of the coating film20exceeds 10 μm, adhesive strength may remarkably decrease, and the coating film20may be projected on the screen when X-ray is projected, which may cause confusion in medical treatment.

Depositing the coating film (S600) may include disposing cage bodies on a rotating unit rotatably provided in a chamber (S610), disposing a metal target made of a metal material at a distance from the cage bodies in the chamber (S620), injecting an inert gas into the chamber through a gas supply unit (S630), and coating the surfaces of the cage bodies with the metal material by applying a predetermined temperature and pressure to an inside of the chamber and applying a predetermined voltage to the metal target (S640).

As shown in the drawing, a deposition device configured to perform depositing the coating film (S600) includes a chamber40, a rotating unit41, a metal target44, etc. The chamber40has a space therein so that various parts may be placed, and the rotating unit41is provided rotatably at the center of the inside of the chamber40.

As such, the rotating unit41includes a pair of longitudinal supports42rotatably disposed on both sides about the rotation axis and a plurality of transverse supports43disposed perpendicular to individual longitudinal supports42. The transverse supports43are vertically spaced apart from each other while being perpendicular to the longitudinal supports42, and the intervals between the transverse supports43are preferably the same. The cage bodies10may be disposed on respective transverse supports43.

In the present invention, the cage bodies10may be rotated in a state of being spaced apart from each other at regular intervals in both the longitudinal and transverse directions inside the chamber40. Accordingly, when depositing the coating film20, the coating film20may be uniformly deposited on the surfaces of the cage bodies10.

The metal target44is spaced apart from the rotating unit41and attached to the inner surface of the chamber40, and a metal material is supplied to the cage body10by applying a voltage thereto. The gas supply unit45supplies an inert gas into the chamber40. Argon gas, etc. may be used as the inert gas.

In the coating process (S640), when a predetermined temperature and pressure are applied to the inside of the chamber40and a predetermined voltage is applied to the metal target44, ions of the inert gas are accelerated and collide with the metal target44, and the metal material (e.g., titanium) that is separated due to such collision adheres to the cage body10, so that the coating film20is deposited.

Here, the coating process (S640) is preferably performed at a pressure of 3*10−3to 7*10−3torr, a temperature of 100 to 300° C., a power of 20 kW, and a voltage of 5 to 30 V.

If the pressure applied in the coating process (S640) is less than 3*10−3torr, the time for which the deposition process is performed may excessively increase, whereas if the pressure applied in the coating process (S640) exceeds 7*10−3torr, deposition efficiency of the coating film20may decrease.

If the temperature applied in the coating process (S640) is lower than 100° C., the temperature may be too low to perform the deposition process, whereas if the temperature applied in the coating process (S640) is higher than 300° C., the melting point of polyether ether ketone (PEEK) constituting the cage body10is about 341° C., and thus a possibility of damage to the cage body10may remarkably increase.

If the voltage applied in the coating process (S640) is less than 5 V, the ions of the inert gas in the chamber40may not receive sufficient force, making it difficult to separate the metal material despite collision of such ions with the metal target44, whereas if the voltage applied in the coating process (S640) exceeds 30 V, the ions of the inert gas in the chamber40may penetrate in the metal target44, rather than the metal material being separated due to collision thereof with the metal target44.

FIG.9shows a performance verification test of the cage body with the coating film deposited thereon according to an embodiment of the present invention,FIG.10shows the cage body after a performance verification test on the cage body with the coating film deposited thereon according to an embodiment of the present invention,FIG.11shows enlarged images of contact portions between the jigs and the cage body after a performance verification test on the cage body with the coating film deposited thereon according to an embodiment of the present invention,FIG.12shows specimens manufactured for animal testing of the cage body with the coating film deposited thereon according to an embodiment of the present invention,FIG.13shows microscope images of tissue that is collected and stained after animal testing of the cage body with the coating film deposited thereon according to an embodiment of the present invention, andFIG.14is a graph comparing the bone area after animal testing of the cage body with the coating film deposited thereon according to an embodiment of the present invention.

As shown inFIGS.9to11, after manufacturing the cage body10with the coating film20deposited thereon according to an embodiment of the present invention, a fatigue test is performed to verify the stability of the product.

In the stability verification test, as shown inFIG.9, jigs50are placed on the top and bottom of the cage body10and a load is repetitively applied 5 million times to determine whether debris or particles are generated on the surface of the cage body10.

The stability verification test is conducted using field emission-scanning electron microscopy (FE-SEM), and as shown inFIG.10, the contact portions a-1, a-2, b-1, b-2between the jigs50and the cage body10are analyzed.

As shown inFIG.11, based on results of FE-SEM of the contact portions between the jigs50and the cage body10, it can be confirmed that there is no peeling or detachment of the coating film20.

As shown inFIGS.12to14, after manufacturing the cage body10with the coating film20deposited thereon according to an embodiment of the present invention, animal testing is performed to compare bone union rates. In animal testing, a specimen is manufactured and implanted into the leg bone of a rabbit, and the extent to which the bone is attached to the surface of the cage body10is determined.

As shown inFIG.12, three specimens are prepared. In the drawing, the leftmost specimen is a polyether ether ketone (PEEK) specimen, the middle specimen is a specimen in which the coating film20is deposited on the surface of the cage body10according to an embodiment of the present invention, and the rightmost specimen is a titanium specimen.

Each of three sterilized specimens thus prepared is implanted in the femur of a 4-month-old male rabbit (New Zealand white rabbit), and after a 12-week recovery period, each specimen is extracted and the extent of bone formation around the specimen is analyzed.

FIG.13shows microscope images of tissue that is collected and stained 12 weeks after implanting each specimen into the femur of a rabbit. In the drawing, the leftmost image is an image of the polyether ether ketone (PEEK) specimen, the middle image is an image of the specimen of the cage body10with the coating film20deposited thereon according to an embodiment of the present invention, and the rightmost image is an image of the titanium specimen.

As shown in the drawing, it can be confirmed that the specimen of the cage body10with the coating film20deposited thereon according to an embodiment of the present invention has a larger amount of newly generated bone, and also that tissue is in good contact with no gaps between the surface of the specimen (titanium coated peek) and the newly generated bone.

More specifically, as shown inFIG.14, based on results of measurement of the bone formation rate (bone area) in the selected area by analyzing the microscope images, the bone area is determined to be much higher in the specimen (G2) with the titanium coating film20deposited thereon according to an embodiment of the present invention than in the polyether ether ketone (PEEK) specimen without any coating (G1).

In this way, the coating film20is deposited with a metal material on the surface of the cage body10including a polymer material in the present invention, thereby applying the advantages of stability of physical properties of the polymer material and high biocompatibility of the metal material to a spinal cage.

As is apparent from the above description, the present invention has the effect of applying the advantages of stability of physical properties of a polymer material and high biocompatibility of a metal material to a spinal cage by depositing a coating film with a metal material on the surface of a cage body including a polymer material.

In addition, the present invention has the effect of further increasing biocompatibility without deteriorating performance of the coating film by increasing the surface roughness value of a cage body by a sanding process.

Furthermore, the present invention has the effect of remarkably enhancing adhesion between different materials by depositing a coating film with a metal material on the surface of the cage body under optimal conditions.

The present invention described above is not limited to the aforementioned embodiments and the appended drawings, and those skilled in the art will appreciate that various substitutions, modifications, and alterations are possible, without departing from the technical spirit of the present invention.