Surgery tool

Abstract

To provide a novel surgery tool that facilitates vertebra fixing operation.SOLUTION: Provided is a surgery tool for checking in advance a degree of bending of a spinal rod for fixing vertebrae in vertebra fixing operation. The surgery tool has a rod-shaped core material. The core material is formed of a material being a resin molding having a return angle in a 90° bending test of 15° or less. 90 mass% or more of the entire surgical tool is formed of a resin material and 20 mass% or more of the entire surgical tool is the core material.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to surgical instruments. [Background technology]

[0002] Spinal fusion surgery is a type of spinal surgery that involves using spinal rods to fix multiple vertebrae together, and is performed to treat conditions such as spinal stenosis, herniated discs, scoliosis, spinal cord injury, spondylolisthesis, and spinal tumors.

[0003] In spinal fixation surgery, when fixing vertebrae with a spinal rod, a trial rod (surgical instrument) may be used in advance to check the degree of bending of the spinal rod (see, for example, Patent Document 1). The trial rod described in Patent Document 1 has a configuration in which a core made of a metal material is covered with an outer tube made of silicone rubber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6560632 Summary of the Invention [Problem to be solved by the invention]

[0005] In spinal fixation surgery, there are cases where the surgical field is narrow due to a small incision, or where the spinal rod needs to be attached in a position where it interferes with surrounding tissue. In such cases, conventional trial rods can be difficult to handle during surgery, and improvements were needed.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel surgical instrument that makes spinal fixation surgery easier. [Means for solving the problem]

[0007] The trial rods have a metal core, making it difficult to adjust their length. Therefore, even when the surgical field is narrow, a relatively long trial rod must be used, which can make handling during surgery difficult.

[0008] In response to the above-mentioned problems, the inventors came up with the idea of ​​replacing the metal core with a resin core, which would make it easier to cut. However, if a resin core were simply used, even if the trial rod was bent at the surgical site to check the bending state of the spinal rod, the trial rod would easily recover elastically, making it difficult to achieve the purpose.

[0009] Therefore, the inventors have conducted extensive research into the problem from the above perspective and have completed the invention.

[0010] In order to solve the above problems, one aspect of the present invention includes the following aspects.

[0011] [1] A surgical instrument for checking in advance the degree of bending of a spinal rod that fixes vertebrae together in a spinal fixation surgery, the surgical instrument having a rod-shaped core material, the core material being made of a resin molded body that has a return angle of 15° or less in a 90° bending test, the surgical instrument being made up of 90% or more by mass of resin material, and the core material accounting for 20% or more by mass of the entire surgical instrument.

[0012] [2] The resin molding has a density of 950 kg / m 3 The surgical instrument according to [1] is made from an ethylene homopolymer or an ethylene-α-olefin copolymer having a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 5 to 15 and an α-olefin content of 3 to 6 carbon atoms of less than 2% by weight.

[0013] [3] A surgical instrument according to [1] or [2], which comprises a coating layer that covers the outer surface of the core material, and the core material is a laminate formed by stacking a plurality of sheet-shaped resin molded bodies.

[0014] [4] The surgical instrument according to [3], wherein the laminate has unbonded portions between the plurality of resin molded bodies.

[0015] [5] The surgical instrument according to [3] or [4], wherein the covering layer has a scale that defines the longitudinal length of the core material.

[0016] [6] The surgical instrument according to any one of [1] to [5], wherein the core material has a rectangular cross section perpendicular to the longitudinal direction. [Effects of the Invention]

[0017] According to the present invention, a novel surgical instrument that facilitates spinal fixation surgery can be provided. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic perspective view of a surgical instrument 10. [Figure 2] FIG. 2 is a schematic cross-sectional view of the surgical instrument 10. [Figure 3] FIG. 3 is a schematic diagram showing an example of a method for manufacturing the surgical instrument 10. [Figure 4] FIG. 4 is an explanatory diagram showing a 90° bending test for evaluating the surgical instrument 10. [Figure 5] FIG. 5 is a schematic diagram illustrating how to use the surgical instrument 10. DETAILED DESCRIPTION OF THE INVENTION

[0019] The surgical instrument according to this embodiment will be described below with reference to Figures 1 to 4. In all of the following figures, the dimensions and proportions of the components have been changed as appropriate to make the drawings easier to understand.

[0020] Fig. 1 is a schematic perspective view of a surgical instrument 10. Fig. 2 is a schematic cross-sectional view of the surgical instrument 10, taken along line II-II in Fig. 1.

[0021] (surgical instruments) The surgical instrument 10 shown in Figures 1 and 2 is used to check in advance the degree of bending of a spinal rod that secures vertebrae together during spinal fixation surgery. Such instruments are generally called "trial rods" or "rod templates."

[0022] The surgical instrument 10 is bendable. For example, when the surgical instrument 10 is subjected to an external force F, it bends in the direction of the symbol X. After being bent, the surgical instrument 10 is capable of maintaining the bent shape.

[0023] The surgical instrument 10 has a scale 10s engraved on the surface 10a. The scale 10s may be printed on the surface 10a of the surgical instrument 10, or may be formed into a convex or concave shape on the surface 10a. By having the scale 10s on the surgical instrument 10, it is possible to check the length of the spinal rod as well as the degree of bending of the spinal rod by using the surgical instrument 10.

[0024] Such a surgical instrument 10 is composed of 90% by mass or more of a resin material. When 90% by mass of the entire surgical instrument 10 is composed of a resin material, the remaining 10% by mass may contain an inorganic material. Examples of inorganic materials that may be contained in the surgical instrument 10 include inorganic fillers known in the field of resin processing. Inorganic materials do not include wires or metal fibers that extend over the entire longitudinal length of the surgical instrument 10.

[0025] Preferably, 95% by mass or more of the surgical instrument 10 is made of resin material, and more preferably, substantially all of the surgical instrument 10 is made of resin material. Here, "substantially all" means that the surgical instrument 10 is allowed to contain inorganic fillers to the extent that they do not affect the physical properties.

[0026] As shown in FIG. 2, the surgical instrument 10 has a core material 1 and a covering layer 2.

[0027] (Core material) The core material 1 is a thin rod-shaped (bar-shaped, pole-shaped) or strip-shaped (sheet-shaped) resin molded body that extends over substantially the entire length of the surgical instrument 10. The cross-sectional shape of the core material 1 is not particularly limited and may be, for example, rectangular, polygonal, circular, or elliptical, although a rectangular shape is preferred.

[0028] The core material 1 accounts for 20% by mass or more of the entire surgical instrument 10. The core material 1 may account for 40% by mass or more, 60% by mass or more, 80% by mass or more, or even 100% by mass of the entire surgical instrument 10 (i.e., a configuration without a coating layer 2). When the core material 1 accounts for 100% by mass of the entire surgical instrument 10, the scale 10s may be engraved directly on the core material 1.

[0029] The core material 1 is a resin molded body whose return angle in a 90° bend test is 15° or less. The "return angle in a 90° bend test" is defined as the return angle θ when the resin molded body is bent 90° at the center of its length and held for 5 minutes, and then released. For example, if the bent part opens to A°, then θ(°) = A-90.

[0030] The core material 1 may be a single layer or a laminate of strip-shaped resin molded bodies. When the core material 1 is a laminate, the rigidity of the core material can be adjusted by adjusting the number of laminated resin molded bodies, making it easy to adjust the rigidity of the entire surgical instrument 10.

[0031] 2 is a laminate of five resin molded bodies 1A, 1B, 1C, 1D, and 1E. The cross-sectional shape of each resin molded body is preferably rectangular.

[0032] The resin molded bodies 1A, 1B, 1C, 1D, and 1E may be joined to one another, but preferably have portions where they are not joined. Note that "joined" includes adhesion and fusion. By having portions where the resin molded bodies are not joined to one another, the layers of the resin molded bodies can slip between each other when the surgical instrument 10 is bent, making it easier to bend than a core material that is an integrally molded body of the same thickness.

[0033] The resin molded body may have the color of the resin itself or may be colored.

[0034] The five resin molded bodies may be the same as or different from one another.

[0035] The material (resin molding) of the core material 1 has a density of, for example, 950 kg / m 3 The above-mentioned polymers can be obtained by melt-molding and stretching an ethylene homopolymer or an ethylene-α-olefin copolymer having a weight-average molecular weight (Mw) / number-average molecular weight (Mn) ratio of 5 to 15 and an α-olefin content of 3 to 6 carbon atoms of less than 2% by weight.

[0036] The above physical properties can be determined by the following methods.

[0037] (Measurement of the physical properties of raw materials used) Resin density: Method specified in ASTM D1505 Molecular weight distribution (Mw / Mn): Calculated from the weight average molecular weight (Mw) and number average molecular weight (Mn) measured by gel permeation chromatography (GPC) Comonomer (α-olefin with 3 to 6 carbon atoms) content: Comonomer content in resin measured by NMR

[0038] Biomass-derived ethylene or α-olefin (biomass monomer) may be used as the monomer for the ethylene homopolymer or ethylene-α-olefin copolymer that is the material (resin molded body) of the core material 1. Here, biomass means "organic resources derived from living organisms, excluding fossil resources." The proportion of biomass monomers in the monomers of these materials can be set as desired. The proportion of carbon derived from biomass monomers in the carbon that makes up the resin molded body can be confirmed by a known method that uses carbon dating as the measurement principle.

[0039] The density of the polymer is 955 to 970 kg / m 3 is preferable, and 960 to 970 kg / m3 is more preferred.

[0040] The Mw / Mn of the polymer is preferably 6-14.

[0041] The content of the α-olefin having 3 to 6 carbon atoms in the polymer is preferably 0.05% by mass or more and 1.5% by mass or less.

[0042] The polymer is preferably an ethylene-α-olefin copolymer rather than an ethylene homopolymer, and propylene is preferred as the α-olefin constituting the ethylene-α-olefin copolymer.

[0043] The melt flow rate (MFR) of the polymer is preferably 0.1 or more and 1.0 or less, and more preferably 0.2 or more and 0.5 or less (both in units of g / 10 min) at 190° C. under a load of 2160 g. The melt flow rate can be measured according to the standard of ASTM D1238.

[0044] The material (resin molded body) of the core material 1 can be produced by melt-molding the above polymer, for example, into a strip, and then stretching it at 100°C or less, preferably 85°C or higher and 100°C or lower, to the extent that the desired return angle is achieved.

[0045] The thickness of the molded body before stretching is preferably 1 mm or more and 20 mm or less, more preferably 1 mm or more and 12 mm or less.

[0046] The stretching ratio is in the range from the yield point to the breaking point of the molded article before stretching, and is preferably 7 times to 20 times, more preferably 10 times to 16 times.

[0047] The core material may contain other thermoplastic resins and various additives within a range that achieves the desired physical properties. Examples of other thermoplastic resins that may be used include plant-based biodegradable plastics.

[0048] Examples of additives include processing aids, coloring pigments, antistatic agents, and inorganic fillers.

[0049] Note that materials other than those using the above resins can also be used for the core material 1, as long as they are resin molded bodies that have a return angle of 15° or less in a 90° bending test. Also, examples of commercially available products that can be used as the material for the core material 1 include "Forte" (manufactured by Sekisui Seizo Co., Ltd.) and "Technoroto" (manufactured by M.A. Life Materials Co., Ltd.).

[0050] (covering layer) The covering layer 2 covers the outer peripheral surface of the core material 1. The above-mentioned scale 10s is provided on the surface of the covering layer 2. The covering layer 2 is flexible and made of a resin material.

[0051] The material for the covering layer 2 is not particularly limited as long as it exhibits the desired flexibility, and examples thereof include crosslinked (vulcanized) rubber, thermoplastic elastomer, and thermoplastic resin.

[0052] The inner surface of the coating layer 2 and the core material 1 may or may not be bonded. In the surgical instrument 10, it is preferable that the surface 2x of the inner surface of the coating layer 2 facing the resin molded body 1A is bonded to the resin molded body 1A. It is also preferable that the surface 2y of the inner surface of the coating layer 2 facing the resin molded body 1E is bonded to the resin molded body 1E.

[0053] 3A and 3B are schematic diagrams showing an example of a manufacturing method for a surgical instrument 10. First, as shown in Fig. 3A, resin molded bodies 1A, 1B, 1C, 1D, and 1E that make up the core material 1 are laminated and inserted into the interior 20a of a heat-shrinkable tube 20 made of, for example, polyethylene. The resin molded bodies 1A, 1B, 1C, 1D, and 1E may or may not be bonded before being inserted into the heat-shrinkable tube 20.

[0054] 3(b), when the heat-shrinkable tube 20 is heated, the heat-shrinkable tube 20 shrinks and tightens and fixes the core material 1. Heating may be performed by blowing hot air, or by placing the core material 1 and the heat-shrinkable tube 20 in a heated environment.

[0055] Furthermore, heating may be performed by pressing a heating body against the outside of the heat-shrinkable tube 20. By employing such a heating method, the covering layer 2 obtained from the heat-shrinkable tube 20 is further partially melted at the locations where the heating body is pressed, and the resin molded bodies 1A and 1E inside and the covering layer 2 are bonded (thermally fused).

[0056] After forming the covering layer 2, both ends in the longitudinal direction may be further heat-treated to completely seal the internal core material 1. Alternatively, separate caps (not shown) may be attached to both ends in the longitudinal direction to protect the core material 1 from exposure.

[0057] Other methods for forming the coating layer include: The material for the coating layer is dissolved in a solution, and the resulting solution is applied around the core material and allowed to dry. · A coating layer is formed directly around the core material using injection molding (insert molding). Examples of such methods include:

[0058] The above method yields the surgical instrument 10. The surgical instrument 10 may have, for example, a total length of 300 mm, a width of 4.7 mm, and a thickness of 3.9 mm.

[0059] The surgical instrument 10 thus obtained is evaluated by performing the following 90° bending test. Figure 4 is an explanatory diagram showing the 90° bending test for evaluating the surgical instrument 10, and is a plan view showing the test conditions.

[0060] (90° bending test (surgical instruments)) First, as shown in FIG. 4(a), a protractor P with a radius of 5 cm is placed on an evaluation table, and the surgical instrument 10 to be evaluated is placed along a chord S of the protractor P. One end 10X of the surgical instrument 10 is aligned with the end of the chord S. The surgical instrument 10 is in the state indicated by the symbol 10A.

[0061] Next, while holding the position of one end 10X of the surgical instrument 10, the other end 10Y is grasped and moved along the arc of the protractor P until the other end 10Y coincides with the 90° position P1 on the protractor P. The surgical instrument 10 then assumes the state indicated by reference symbol 10B.

[0062] Next, while maintaining the state in which the surgical instrument 10 overlaps with position P1, the evaluator uses force to bend the surgical instrument 10 along the chord S of the protractor P. As the surgical instrument 10 bends, it approaches the center C of the protractor P. When the surgical instrument 10 is bent to the limit at which it can maintain the state in which it overlaps with position P1 (state indicated by reference symbol 10C), the distance L from one end 10X to position P2 where the surgical instrument 10 separates from the chord S of the protractor P is measured. The distance L is used as an index of flexibility.

[0063] Next, as shown in Figure 4(b), the surgical instrument 10 is fixed in the state indicated by reference numeral 10C for five minutes, and then released. One minute after the release, the surgical instrument 10 has elastically recovered and is in the state indicated by reference numeral 10D. The position P3 where the surgical instrument 10 overlaps with the chord S of the protractor P is recorded, and the angle φ formed by points P1, C, and P3 is measured. The angle φ is called the "return angle" and is used as an indicator of the ability of the surgical instrument 10 to maintain its bent shape (shape retention).

[0064] The surgical instrument 10 has a return angle φ of 15° or less (evaluation criterion 1) and a distance L of 20 mm or more (evaluation criterion 2) in the above 90° bending test. This surgical instrument 10 can be bent freely for the purpose of determining the bending state of a spinal rod in spinal fixation surgery, and it is easy to maintain the bent shape.

[0065] FIG. 5 is a schematic diagram illustrating how to use the surgical instrument 10. First, as shown in Figure 5(a), depending on the size of the surgical field in the spinal fixation surgery and the range of vertebrae to be fixed, the surgical instrument 10 is cut at the position indicated by the symbol α to form a first rod 11 and a second rod 12.

[0066] Since 90% or more by mass of the entire surgical instrument 10 is made of resin material, it can be easily cut to adjust the length. The first rod 11 is used in surgery. The second rod 12 is used in another surgery or discarded.

[0067] Next, as shown in Figure 5(b), the first rod 11 is bent and attached to the holding portion B of the spinal rod, and the positional deviation of the vertebrae A1, A2, A3, A4 and vertebrae A5, A6 to which the holding portion B is attached is adjusted so that they are aligned to the desired shape of the spine A. The degree of bending of the spinal rod in the spinal fixation surgery can be confirmed from the first rod 11 bent in this way. In addition, the length of the spinal rod can be confirmed from the scale engraved on the first rod 11 (scale 10s shown in Figure 1).

[0068] The surgical instrument 10 has a core material 1 that is a resin molded body with a return angle of 15° or less in a 90° bending test, and the core material 1 accounts for 20% by mass or more of the entire surgical instrument 10. As a result, the surgical instrument 10 also satisfies the above evaluation criteria 1 and 2, can be bent freely, and can maintain its shape.

[0069] Based on the shape (degree of bending) and length of the first rod 11 thus molded, a spinal rod 100 to be used for actual spinal fixation is formed, and the spine A is fixed using the spinal rod 100.

[0070] The surgical instrument 10 configured as described above allows for easy length adjustment, allows for free bending, and can maintain the bent shape, making it easy to grasp the degree of bending of the spinal rod, thereby facilitating spinal fixation surgery.

[0071] In this embodiment, the five resin molded bodies constituting the core material 1 each have a return angle of 15° or less in a 90° bending test, but this is not limited to this. For example, one or more of the five resin molded bodies may be a molded body with a return angle greater than 15° or less, as long as the surgical instrument 10 achieves the effects of the invention.

[0072] In addition, in this embodiment, the scale 10s is engraved on the surface 10a, but this is not limited to this. When the covering layer 2 is optically transparent, the scale may be engraved on the core material 1. Furthermore, the surgical instrument 10 does not have to have a scale.

[0073] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on the design, specifications, etc., without departing from the spirit of the present invention. [Example]

[0074] The present invention will be described below with reference to examples, but is not limited to these examples. The core materials used in the following examples 1 and 2 and comparative examples 1 to 3 all had the same length.

[0075] The physical properties of the polyolefin contained in the resin molded product (Technorot) used in the following examples were measured by the method described above in (Measurement of physical properties of raw materials used). Resin density: 964kg / m 3 Molecular weight distribution (Mw / Mn): 9 Comonomer (propylene) content: 0.15% by mass

[0076] [Example 1] A polyolefin resin molded body (Technoroth, model number H20000, manufactured by M.A. Life Materials Co., Ltd., length 300 mm) was used as the core material. The resin molded body (Technoroth H20000) used as the core material was confirmed to have a return angle θ of 15° or less in a 90° bending test using the method described above. Five resin molded bodies were stacked and inserted into a polyethylene heat-shrinkable tube (Heyiarbeit).

[0077] A heating tool (clothing iron) heated to 80°C was pressed against the outside of the heat-shrinkable tube to shrink the heat-shrinkable tube and bond the core material and the heat-shrinkable tube, thereby obtaining the surgical instrument of Example 1 (cross section 4.7 mm x 3.9 mm).

[0078] [Example 2] The surgical instrument of Example 2 (cross section 4.6 mm × 3.7 mm) was obtained in the same manner as in Example 1, except that five polyolefin resin molded bodies (Technorot, model number H18000, manufactured by M.A. Life Materials Co., Ltd.) were stacked together as the core material.

[0079] The resin molding (Technoroth H18000) used as the core material was confirmed to have a return angle θ of 15° or less in a 90° bending test using the method described above.

[0080] [Comparative Example 1] A commercially available rod template (silicon nitinol rod template 250 mm (5.5 × 250 mm) (manufactured by Nippon MDM Co., Ltd.)) was used as the surgical instrument in Comparative Example 1. It consisted of a nickel-titanium alloy (nitinol) wire core covered with silicone resin and had a circular cross section.

[0081] Comparative Example 2 A surgical instrument of Comparative Example 2 (approximately circular cross section, diameter 5.2 mm) was obtained in the same manner as in Example 1, except that five ABS 3D printer filaments (manufactured by Verbatim, circular cross section, diameter 1.75 mm) were bundled together as the core material.

[0082] The return angle θ of the filament used as the core material was measured in a 90° bending test using the method described above, and it was confirmed to be greater than 15°.

[0083] Comparative Example 3 A polyolefin resin molded body (Technoroth, model number H18000, manufactured by M.A. Life Materials Co., Ltd.) was used as the core material, and the same heat-shrinkable tube was placed inside a polyethylene heat-shrinkable tube, and the core material was inserted into the inner heat-shrinkable tube. Heating was performed in the same manner as in Example 1 to obtain a surgical instrument (cross section 2.6 mm × 7.0 mm) for Comparative Example 3.

[0084] <evaluation> (Evaluation 1. Possibility of cutting) We checked whether each surgical instrument could be cut with commercially available scissors. Surgical instruments that could be cut were rated as passed, and surgical instruments that could not be cut were rated as failed.

[0085] (Evaluation 2. Shape retention) Each surgical instrument was subjected to a 90° bending test according to the method described above (90° bending test (surgical instruments)), and the return angle φ, which is an index of shape retention, was measured. A return angle φ of 20° or more was considered pass, and one less than 20° was considered fail.

[0086] (Rating 3. Flexibility) A 90° bending test was performed on each surgical instrument according to the method described above (90° bending test (surgical instruments)), and the distance L, which is an index of flexibility, was measured. A distance L of 20 mm or more was considered pass, and a distance L of less than 20 mm was considered fail.

[0087] (comprehensive evaluation) A surgical instrument that was evaluated as passing in all of the above evaluation items 1 to 3 was evaluated as passing overall, and a surgical instrument that was evaluated as not passing in any one of the items was evaluated as failing.

[0088] The configuration of each surgical instrument is shown in Table 1, and the evaluation results are shown in Table 2. In Table 2, pass is indicated as "A" and fail is indicated as "B".

[0089] [Table 1]

[0090] [Table 2]

[0091] As a result of the evaluation, it was found that the surgical instruments of Examples 1 and 2 could be easily cut with scissors, and also had shape retention and flexibility.

[0092] On the other hand, it was found that the surgical instrument of Comparative Example 1 could not be easily cut because the core material was made of metal, and it was also found to have poor flexibility.

[0093] The surgical instrument of Comparative Example 2 had a return angle of the core material used that exceeded 15°, and it was found to have poor shape retention and flexibility.

[0094] In the surgical instrument of Comparative Example 3, the proportion of core material to the entire instrument was less than 20% by mass, and therefore the physical properties of the core material used were not very apparent in the surgical instrument, and it was found that the surgical instrument had poor shape retention and flexibility.

[0095] From the above results, it was found that the present invention is useful. [Explanation of symbols]

[0096] 10...surgical instrument, 1...core material, 10s...scale, 1A to 1E...resin molded body, 2...covering layer, 100...vertebral rod, A...vertebra, A1, A5...vertebrae, θ...return angle

Claims

1. A surgical instrument for confirming in advance the degree of bending of a spinal rod that fixes vertebrae together in a spinal fixation surgery, It has a rod-shaped core material, The core material is a resin molded body having a return angle of 15° or less in a 90° bending test, 90% by mass or more of the entire surgical instrument is made of a resin material, A surgical instrument, wherein the core material accounts for 20% by mass or more of the entire surgical instrument.

2. The resin molded body has a density of 950 kg / m ３ The surgical instrument according to claim 1, wherein the material is an ethylene homopolymer or an ethylene-α-olefin copolymer having a weight average molecular weight (Mw) / number average molecular weight (Mn) of 5 to 15 and an α-olefin content of 3 to 6 carbon atoms of less than 2% by weight.

3. a coating layer that coats the outer peripheral surface of the core material; 3. The surgical instrument according to claim 1, wherein the core material is a laminate in which a plurality of the sheet-shaped resin molded bodies are stacked.

4. The surgical instrument according to claim 3 , wherein the laminate has unbonded portions between the plurality of resin molded bodies.

5. The surgical instrument according to claim 3 , wherein the covering layer has a scale that defines the length of the core material in the longitudinal direction.

6. 3. The surgical instrument according to claim 1, wherein the core member has a rectangular cross section perpendicular to the longitudinal direction.

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