Method for manufacturing an orthopedic screw and orthopedic screw

Description

1 / 11 METHOD FOR MANUFACTURING ORTHOPEDIC SCREWS AND ORTHOPEDIC SCREWS BACKGROUND FIELD OF TECHNIQUE

[001] The present invention relates to the surfaces of orthopedic screws. More particularly, it relates to a balance compensation on the thread surfaces of orthopedic screws.

[002] During the manufacture of products of any kind, including screws of any kind, machine lines or manufacturing marks are generally left behind, even at a microscopic level. In the manufacture of screws, and in particular orthopedic screws, the thread formation by the machinery used to form them or the wear behavior of the tool and the corresponding machine surfaces, together with the material from which the screw is made, can and often does result in the thread having machine lines which are referred to in this document as grain. These machine lines, or grains, are directional in nature as a result of the direction in which the screw threads are formed by the tools used for them and have different heights and depths on all surfaces of the screw.

[003] The grain of screws and their threads can impact the ability to accurately drive / insert the screw into the bone in a precisely aligned manner. This is mainly due to the bone (or other workpiece into which the screw is inserted) having its own grain, and the interaction between the bone grain and the thread grain (in either direction) as it is driven. Petition 870250088527, dated 09 / 30 / 2025, page 7 / 39 2 / 11 where the screw is inserted into the bone. The grain of the bone is the result of many things, including, but not limited to, the various layers of bone, both hard and spongy / soft.

[004] Manufacturing marks, machine lines, or inconsistent or erratic thread grain direction, as referred to in this document, are generally not visible to the naked eye but are easily visible at a microscopic level. This is because screw manufacturers polish, galvanize, or otherwise treat the screw to remove the grain so that it appears smooth and clean to the eye and even to the touch. Figure 1 shows an enlarged image in 12x of an existing bone screw thread. This screw has been polished by the manufacturer, but manufacturing marks or grain lines associated with it can be seen. Figure 2 shows a 25x magnification image of the same screw, and it will be readily apparent from this image that there is clearly a grain associated with the thread resulting from the screw's manufacturing process, despite the manufacturers' attempts to polish or remove it.

[005] As will be observed and mentioned above, the grain of the screw and thread has a direction that is a result of how the thread was formed in the material for the screw. In all manufacturing examples, screw threads are cut or milled from a bar stock, and this cutting causes a grain to be formed in the direction of the cutting, milling, or rolling dies. When screw threads are rolled from bar stock, the grain is formed in the direction of the rolling and in the shape used for it. The same applies to cast screws that use cast molds. In other embodiments, screw threads are ground or compressed. Petition 870250088527, dated 09 / 30 / 2025, page 8 / 39 3 / 11 in the bar stock, which also causes a grain to be formed in the direction of grinding or compression.

[006] Examples of various factors that impact the grain of a manufactured screw include, but are not limited to, varying densities of the screw material used to form the screw and varying thicknesses of the screw material.

[007] Another example refers to faceted orthopedic screws where the facets are formed on the threads or on the front or rear edge of the threads by cutting the rod stock with a particular harmonic vibration; this cut can result in a more refined grain on the facets themselves, which are formed in the direction of the cut used to form the facets. Figure 3 shows a 25x magnified image of an exemplary orthopedic screw with facets cut into it. Figure 4 shows a 50x magnified image of the same screw. These images clearly show the grain formed by the formation of the thread facets. Furthermore, it will be apparent that at the transition point of the facets, the grain is displaced (i.e., not perfectly aligned with the adjacent grain of the adjacent facet) in the screw core.

[008] Thus, it should be noted that when the grain of the screw thread surface (with or without facets) comes into contact with the bone grain during insertion, if these grains are not aligned with each other (even at the microscopic level), this can cause the screw to become slightly misaligned from its intended direction / position during insertion into the bone for the specific application. Furthermore, the misalignment (along with the grains on the thread surfaces) can unnecessarily cut the bone mass. Petition 870250088527, dated 09 / 30 / 2025, page 9 / 39 4 / 11 of the material, which causes residue between the thread and the product (e.g., bone), further destabilizing the intended mechanical performance of the product. This destabilization can lead, for example, to infection and / or rejection of the screw implant by the patient receiving it.

[009] Since bone grains, like wood grains, are not regular or predictable in all situations, it is desirable to manufacture a bone screw surface that compensates for these small misalignments resulting from the combination of the screw grain with the bone grain. This is achieved by the present invention by providing a balanced and aligned manufacturing or machine surface marks during the manufacture of the bone screw. SUMMARY

[0010] According to one implementation of the present invention, the screw thread is compensated for by balance by changing the direction of the screw grain throughout the screw during manufacturing. This and other aspects of the invention are achieved, according to one embodiment, by selectively controlling and altering the cutting direction of the cutting tools used to form the threads during manufacturing. According to another embodiment, the direction of the bar stock can be altered relative to the cutting tools to selectively control and alter the cutting direction during the manufacturing process.

[0011] Other aspects and features of the present principles will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It should be understood, however, that the drawings are designed for illustrative purposes only and not as a Petition 870250088527, dated 09 / 30 / 2025, page 10 / 39 5 / 11 definition of the limits of these principles, to which reference should be made to the attached claims. It should also be understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are intended only to conceptually illustrate the structures and procedures described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In drawings where similar reference numerals denote similar components in all views:

[0013] Figure 1 is a 12x magnification image of a bone screw according to the known state of the art;

[0014] Figure 2 is a 25x magnified image of the bone screw in Figure 1;

[0015] Figure 3 is a 25x magnification image of another bone screw according to the known state of the art;

[0016] Figure 4 is a 50x magnification image of the bone screw in Figure 3;

[0017] Figures 5 and 6 are exemplary images of bones in partial cross-section showing their various layers;

[0018] Figures 7A-7D are cross-sectional views of a screw showing the partitioning into sections of 1 / 2, 1 / 3, 1 / 4 and 1 / 8, respectively;

[0019] Figure 8 is a flowchart of the method for providing a balance-compensated screw thread, according to one embodiment of the invention; and

[0020] Figures 9A and 9B are plan views that Petition 870250088527, dated 09 / 30 / 2025, page 11 / 39 Figures 6 / 11 show the use of various cutting devices on the same stock of bars, according to another implementation of the present invention. DETAILED DESCRIPTION

[0021] Figures 5 and 6 show partial cross-sectional images of bones to demonstrate the various layers involved in driving a screw into them. As will be observed, there are many layers in bones, including, for example, the periosteum (outermost layer), compact bone, spongy bone, along with blood vessels, osteons, concentric lamellae, Haversian canal, and Volkmann's canal. Each of these layers has varying density and thickness, and thus, when inserting a bone screw into the bone, it becomes evident that these varying densities and thicknesses, in themselves, have an impact on the screw being inserted. Add to this the thread grain of this bone screw and how it interacts with each of these layers, and it becomes even more apparent that each layer (of different density and thickness) can have a different impact on the alignment of the screw as it is inserted into the bone.For example, as the screw is inserted into the bone (through a pre-drilled channel or hole), the different densities and thicknesses of the bone layers can have different impacts on different parts of the screw as it descends into the pre-drilled channel or hole.

[0022] The present invention proposes to alter the way screws are manufactured to provide a geometrically balanced thread surface, so that the manufacturing marks or grain automatically align and balance the screw during insertion and thus compensate Petition 870250088527, dated 09 / 30 / 2025, p. 12 / 39 7 / 11 possible misalignments or damage to bone mass resulting from the same. In another alternative modality, the concept of a balanced aligned surface in threading refers to non-cutting thread surfaces (i.e., surfaces on the angled portions of the thread that extend from the axis to the peak of the thread) that do not cut when inserted into the bone, thus eliminating the possible formation of debris.

[0023] This is achieved, according to one embodiment, by cutting or forming the thread in parts or sections along its entire length. For example, by dividing the screw (from a cross-sectional perspective) into halves, thirds, quarters, eighths, etc., it is possible to form the thread in each geometric portion separately, so that the surface grain or the manufacturing marks / machine lines meet and align to counteract each other along the entire thread, compensating for deflection misalignments caused by the grain of the workpiece (e.g., bone).

[0024] Figure 7A shows a cross-sectional view of a screw 10A divided into two halves 70A and 70B. Figure 7B shows a cross-sectional view of a screw 10B divided into thirds, 72A, 72B and 72C. Figure 7C shows a cross-sectional view of a screw 10C divided into quarters, 74A, 74B, 74C and 74D. Figure 7D shows a cross-sectional view of a screw 10D divided into eights, 76A, 76B, 76C, 76D, 76E, 76F and 76G.

[0025] Figure 8 shows a flowchart of method 80 for manufacturing a balanced compensated screw according to an embodiment of the invention. The machine loading has been initiated (e.g., Numerical Control) Petition 870250088527, dated 09 / 30 / 2025, page 13 / 39 8 / 11 Computerized (CNC) with the bar or thread from which the screw will be made (82). The machine is set up or programmed (84) to cut the threads in sections selected by the user. As noted above, this can be as simple as two sections (halves) or it can be more complex with three or more sections. The machine is then started and a section of threads is cut from the stock in an initial or predetermined direction (86). The next adjacent section of threads is then cut from the stock in a second direction that is opposite to the initial or predetermined direction (88). Next, a determination is made (90) to ascertain whether the thread cutting is complete (i.e., whether all sections set in step 84 have been completed). If so, the process ends and the screw is ejected from the machine. If not in step 90, the process continues to cut the next adjacent section of threads in the initial or first predetermined direction.Next, a further determination is made (94) as to whether the thread cutting is complete. If the thread cutting is complete, the process ends. If the thread cutting is not complete, the process returns to step 88 and begins again by cutting the next adjacent section in the first direction.

[0026] As will be observed by those skilled in the art, the direction of the cutting directions may be clockwise or counterclockwise with respect to the screw stock, provided that the opposite cutting technique is used on adjacent sections of the screw designated at the start of manufacturing.

[0027] According to another embodiment for providing geometrically balanced threading, the present invention proposes more than one cutting tool engaged with the stock of bars. With reference to Figure 9A, Petition 870250088527, dated 09 / 30 / 2025, page 14 / 39 Figure 9 / 11 shows an example of a 90 bar, and a first cutting blade 92A and a second cutting blade 94A. In this embodiment, blade 92A and blade 94A will rotate in opposite directions relative to each other and are displaced from each other by a thread, so that, in this example, a complete rotation of the 90 bar will cause the thread cut by blade 92A to meet the thread cut by blade 94A. After the completion of one rotation, blades 92A and 92B are moved to a next position shown by 92B and 94B to complete the next rotation of the bar stock. In this way, each rotation of the bar stock causes two adjacent threads to be cut with opposite cutting directions. In this exemplary embodiment, two cutting blades that simultaneously cut adjacent threads are shown. It should be noted that modifications to the spacing of the blades and cut threads can be made without departing from the scope of the present invention.

[0028] Figure 9B shows another example where blades 92A and 92B are separated from each other, so that two rotations of bar 90 will be necessary for the thread cut by blade 92A to meet the thread cut by blade 94A. In this way, the change in the direction of the cut (or in the grain of the screw) will occur for every two threads and not for each adjacent thread, as shown in the embodiment of Figure 9A.

[0029] According to another embodiment for providing geometrically balanced threading, the present invention proposes the use of more than one cutting tool engaged to the stock of bars during manufacturing. This would allow multiple cutting tools to rotate in Petition 870250088527, dated 09 / 30 / 2025, page 15 / 39 10 / 11 different directions simultaneously during screw / screw thread manufacturing.

[0030] Although fundamental and innovative features of these principles have been shown, described, and pointed out, it will be understood that various omissions, substitutions, and alterations in the form and details of the methods described and devices illustrated, as well as in their operation, may be made by those skilled in the art without departing from the spirit thereof. For example, it is expressly intended that all combinations of these elements and / or steps of the method that substantially perform the same function and substantially in the same manner to achieve the same results are covered by the scope of these principles. Furthermore, it should be recognized that the structures and / or elements and / or steps of the method shown and / or described in connection with any disclosed form or implementation of these principles may be incorporated into any other disclosed, described, or suggested form or implementation as a general matter of design choice.The intention, therefore, is to be limited only as indicated by the scope of the claims attached to this document.

[0031] After describing the preferred modalities, which serve to illustrate various concepts, structures, and techniques that are the subject of this patent, it will now become apparent to those with common skill in the art that other modalities incorporating these concepts, structures, and techniques may be used. Furthermore, elements of different modalities described herein may be combined to form other modalities not specifically set forth above.

[0032] Consequently, it is claimed that this scope Petition 870250088527, dated 09 / 30 / 2025, page 16 / 39 The scope of patent 11 / 11 should not be limited to the embodiments described, but should be limited only by the spirit and scope of the following claims. Petition 870250088527, dated 09 / 30 / 2025, page 17 / 39

Claims

1 / 2 CLAIMS 1. METHOD OF MANUFACTURING AN ORTHOPEDIC SCREW characterized by comprising: rotating a stock of rods in a machine for a first predetermined amount of rotation in a first direction; cutting (86) a thread in the stock of rods using a blade for the first predetermined amount of rotation; changing the first direction of rotation of the stock of rods to a second direction of rotation opposite to the first direction of rotation for a second predetermined amount of rotation; and cutting (88) the thread in the stock of rods using the blade for the second predetermined amount of rotation.

2. METHOD, according to claim 1, characterized in that the first predetermined amount of rotation is 45 degrees.

3. METHOD, according to claim 1, characterized in that the second predetermined rotation value is 45 degrees.

4. METHOD, according to claim 1, characterized in that the first predetermined amount of rotation is 90 degrees.

5. METHOD, according to claim 1, characterized in that the second predetermined rotation value is 90 degrees.

6. METHOD, according to claim 1, characterized in that the first predetermined amount of rotation is in the range of 90 to 180 degrees. Petition 870250088527, dated 09 / 30 / 2025, page 18 / 39 2 / 2 7. METHOD, according to claim 1, characterized in that the second predetermined amount of rotation is in a range of 90 to 180 degrees.

8. ORTHOPEDIC SCREW characterized by being manufactured according to the method as defined in claim 1.

9. METHOD OF MANUFACTURING AN ORTHOPEDIC SCREW characterized by comprising: rotating a stock of rods in a machine for a first predetermined amount of rotation in a first direction of rotation; cutting (86) a thread in the stock of rods using a blade that rotates opposite to the first direction of rotation for the first predetermined amount of rotation; changing the first direction of rotation of the stock of rods to a second direction of rotation opposite to the first direction of rotation for a second predetermined amount of rotation; and cutting (88) the thread in the stock of rods using the blade that rotates in the opposite direction to the second rotation for the second predetermined amount of rotation.

10. METHOD OF MANUFACTURING AN ORTHOPEDIC SCREW characterized by comprising: placing a stock of rods in a machine; cutting (86) a thread in the stock of rods using a first blade that rotates in the first direction; and cutting (88) the thread in the stock of rods using a second blade positioned so as not to interfere with the cutting by the first blade, the second blade rotating in a second direction opposite to the first. Petition 870250088527, dated 09 / 30 / 2025, page 19 / 39

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