Method for Manufacturing Bone Staples

Technical Field:

The present invention relates to orthopaedic staples or similar components used for bone fixation.

Background Art:

The use of orthopaedic staples (also known as "bone staples") has always been attractive in orthopaedic surgery. The bone staple, or similar component, application by an orthopaedic surgeon to repair bone fractures dates back to the early 1940's. A couple of biocompatible materials have been applied to manufacture bone staples, or similar components, which include, but are not limited to, nickel titanium alloys (e.g. nitinol), titanium and its alloys, cobalt-chrome alloys, stainless steel, tantalum and its alloys, tungsten and its alloys, and other biocompatible metals and alloys.

Bone staples, or similar components, usually have a U-shape, which have a bridge and first and second legs extended from respective sides of the bridge. The first and second legs of bone staples, or similar components, may be angled inwardly at rest conditions. At the ends of the first and second legs of bone staples, or similar components, a barb or plural barbs exist, which ensure better bone fusion and retard backing out of the staples, or similar components.

Bone staples, or similar components, are now manufactured mainly from sheet materials. The staples or components are laser cut, or wire electrical discharge machined from the sheet materials. In this case, the material utilization ratio is low. Additionally, the productivity is low. Moreover, it has a high possibility to introduce defects on the tips of barbs, which can lead to failures or at least increased failure possibility of the staples, or similar components. Last but not the least, the price of produced staples will be high, which will deteriorate the competition of bone staples.

One patent (U.S. Pat. No. 9,402,624) was filed to manufacture nitinol bone staples from round wires. However, the barbs on the legs were still cut using removal methods. This method possibly introduces defects at the tips of the barbs, and possibly causes metal ion leakage. There is need, therefore, for a method for manufacturing bone staples that reduces the probability of defects at the tips of the barbs and reduces the possibility of metal ion leakage.

Summary of Invention:

The summary of the invention is a guide to understanding the invention. It does not necessarily describe the most generic embodiment.

The present invention provides a method to manufacture orthopaedic staples, or similar components, from wires, through deformation technology.

The invention in one form is directed to form the barbs at the ends of legs through die forging formation technology, or similar deformation technologies. The barbs may be on the inside of the orthopaedic staples or on both the inside and outside of the orthopaedic staples, or similar components. The number of the barbs at the ends of each leg of the orthopaedic staples, or similar components, may be one or more.

Figures 2A and 2B are front views of orthopaedic staples that can be made by the methods described herein. An orthopaedic staple 200, 220 may comprise: a) a bridge portion 202, 222 comprising first 204, 224 and second 206, 226

ends;

b) first 205, 225 and second 207, 227 legs depending from said first and second ends; and

c) a one or more barbs 208, 228, 229 on said first or second leg.

Figure 1 is a flow chart 100 of a process for making the staples. A staple may be formed by steps comprising: d) form 102 on a section of wire said one or more barbs at least in part by a deformation process; and

e) bend 104 said section of wire with said one or more barbs into a generally U- shape.

The deformation process may be a die forging process. The orthopaedic staple may comprise a biocompatible material such as a nickel- titanium alloy, titanium, a cobalt-chrome alloy, a stainless steel, tantalum, or tungsten.

The section of wire may have a round, rectangular, square or other suitable cross section. The section of wire may have a diameter or width, in the range of 0.5 millimeter and 5.0 millimeter. Referring to figures 2A and 2B, the bridge portion of the orthopaedic staple may be straight 222 or arcuate 202. The barbs may be on the inside 228 or outside 229 of the legs.

The invention in another form is directed to the inward angled legs 205, 207 of the orthopaedic staples, or similar components. The inward angled legs of the orthopaedic staples, or similar components, ensure a better bone fusion and speed up the recovery.

The invention in yet another form is directed to the projected straight or arcuate bridge from the front, elevational view of the orthopaedic staples, or similar components.

An advantage of the present invention is to provide a streamline surface of orthopaedic staples, or similar components, which will increase the fatigue performance, corrosion resistance and reduce the possibility of metal ion leakage.

Another advantage of the present invention is to improve the barb-strength, which improves the retard backing force of the orthopaedic staples, or similar components.

Yet another advantage of the present invention is to increase the productivity of the orthopaedic staples, or similar components.

Brief Description of Drawings:

Figure 1 is a flow chart of a processing method to manufacture bone staples.

Figure 2A is a front view of an orthopaedic staple.

Figure 2B is a front view of an orthopaedic staple.

Best Mode for Carrying Out the Invention:

The detailed description describes non-limiting exemplary embodiments. Any individual features may be combined with other features as required by different applications for at least the benefits described herein. As used herein, the term "about" means plus or minus 10% of a given value unless specifically indicated otherwise.

A portion of the disclosure of this patent document contains material to which a claim for copyright is made. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but reserves all other copyright rights whatsoever.

As used herein, the term "shaped" means that an item has the overall appearance of a given shape even if there are minor variations from the pure form of said given shape.

As used herein, the term "generally" when referring to a shape means that an ordinary observer will perceive that an object has said shape even if there are minor variations from said shape.

As used herein, relative orientation terms, such as "up", "down", "top", "bottom", "left", "right", "vertical", "horizontal", "distal" and "proximal" are defined with respect to an initial presentation of an object and will continue to refer to the same portion of an object even if the object is subsequently presented with an alternative orientation, unless otherwise noted.

As used herein the terms "left" and "right" also disclose the mirror images of objects so described.

According to the present invention, orthopaedic staples, or similar components, can be manufactured from sections of wires (round, rectangular or square), and the barbs at the ends of the legs can be manufactured using die forging, or similar deformation technologies. The materials used to manufacture orthopaedic staples, or similar components, include, but are not limited to, nickel titanium alloys (e.g. nitinol), titanium and its alloys, cobalt-chrome alloys, stainless steel, tantalum and its alloys, tungsten and its alloys, and other

biocompatible metals and alloys.

Figure 1 is a flow chart 100 of a method for forming bone staples. The barbs are first formed 102 from the starting wires, irrespective of said wires having round, rectangular or square cross sections, through deformation technology, like die forging. The die forging, or similar deformation methods, can be conducted at room temperature or at elevated temperature. In this step, the two ends 201, 203 (Figure 2A) or 221, 223 (Figure 2B), of the staple blank are also rounded. Since the barbs are die formed from the staple blank, the diameter or thickness of the two ends of staple blank is a little smaller than that of the center section, where the bridge is formed. In the second shape setting step, the staple blank is further bent to manufacture the staple with a shape setting 104 at a temperature range of 400 °C to 600 °C. The bone staples may then get a surface treatment 106 and passivation 108.

The formed barbs at both ends of the starting wires can be single or plural. The barbs can be formed on both sides, which will be further shape set as the inside and outside of the general U-shape bone staples, or similar components.

The bone staple, or similar components, may comprise a bridge and two legs. The bridge comprises an inner surface 212, 232 and an outer surface 211, 231. The two legs can be symmetric or asymmetric. The ends of the legs may have laterally inwardly directed barbs. The legs of a staple may be angled generally inward.

The bridge of the U-shape bone staple can be straight or arcuate in rest condition, which will benefit the fixing force for the surgeon.

The transverse cross-section of the staple bridge can be round, rectangular, square or other shape. Each of these possible configurations may have a flat inner surface, which grips the bone well, and a radiused, contoured, outer surface which may mitigate the irritation to the skin of the patient. The staples may have no abrupt surface changes (e.g. sharp corners or edges) on the outer surfaces. Because a staple is manufactured from wire, it can be easily formed with virtually any desired cross-sectional configuration. Thus, the outer surface edges can be rounded without the necessity for further working of the staple, like long time tumbling in a media to round the sharp edges from laser or wire electrical discharge machine cutting in prior art staples. Unfortunately, the prior art tumbling step impacts the entire surface of staple. Thus, the barbs and the inner surfaces of the staple may be rounded whereas said barbs and inner surfaces perform better when sharp. In contrast, the outer and inner surfaces and the edge of the barb of a staple can be customized in the present process simply by modification of the dies used during barb formation and staple manufacture.

One advantage of the staples of the present invention is the fact that the outer surface of the present invention has a continuous, streamline surface, which improves the fatigue performance and anti-corrosion resistance, and reduces the possibility of metal ion leakage from the staple.

Another advantage of the staple of the present invention is that the strength of the barb is increased due to the streamline surface. This is in contrast to the prior art staples where the barb is formed from grinding or other material removing methods, hence defects cannot be totally avoided.

Conclusion

While the disclosure has been described with reference to one or more different exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt to a particular situation without departing from the essential scope or teachings thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention.