Pin

Abstract

To provide a pin capable of achieving relatively high pull-out strength regardless of the magnitude of the applied pressure.SOLUTION: A pin is configured to be melted by receiving ultrasonic vibrations from an ultrasonic welding device. The pin is made of a bioabsorbable material. The pin includes a shaft part and a head part. The head part is formed at one end of the shaft part. Each of the shaft part and the head part includes a first portion having a first degree of crystallinity, and a second portion having a second degree of crystallinity lower than the first degree of crystallinity. The first portion included in the shaft part and the first portion included in the head part are formed continuously. The second portion included in the shaft part and the second portion included in the head part are formed continuously. In the shaft part, the outer peripheral surface of the first portion is covered by the second portion.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to pins, and more particularly to pins that melt when subjected to ultrasonic vibrations from an ultrasonic welding device. [Background technology]

[0002] Japanese Patent No. 4412901 (Patent Document 1) discloses an implant that is implanted by an implantation device. The implantation device includes an oscillator and an oscillation unit. The oscillation unit holds the implant. The oscillation unit oscillates by being excited based on the energy generated by the oscillator. The implant melts by receiving mechanical vibration from the oscillation unit (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4412901 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when the embedding device disclosed in the above-mentioned Patent Document 1 is used and ultrasonic vibration is transmitted to the pin, the pin melts. This melting of the pin is utilized for welding. The present inventor(s) discovered that the pull-out strength of the pin varies greatly depending on the pressure applied to the pin when it melts. Note that "melting" in this specification includes "melting" that occurs when the temperature of the object rises to a temperature equal to or higher than the melting point, and "change to a rubbery state" that occurs when the temperature of the object rises to a temperature equal to or higher than the glass transition point but lower than the melting point.

[0005] The present invention has been made to solve such problems, and an object of the present invention is to provide a pin that can achieve relatively good pull-out strength regardless of the amount of pressure applied. [Means for solving the problem]

[0006] A pin according to the present invention is a pin that melts when subjected to ultrasonic vibrations from an ultrasonic welding device. The pin is made of a bioabsorbable material. The pin includes a shaft portion and a head portion. The head portion is formed at one end of the shaft portion. The shaft portion and the head portion each include a first portion having a first crystallinity and a second portion having a second crystallinity lower than the first crystallinity. The first portion included in the shaft portion and the first portion included in the head portion are formed continuously. The second portion included in the shaft portion and the second portion included in the head portion are formed continuously. In the shaft portion, the outer peripheral surface of the first portion is covered by the second portion.

[0007] In this pin, the first portion having a high degree of crystallinity is continuously formed over the shaft portion and the head portion. Therefore, with this pin, even if the pressure applied to the pin during melting is large, deterioration of the pin at the boundary between the shaft portion and the head portion (e.g., the cause of neck breakage) can be suppressed compared to when the entire pin is composed of the second portion (portion with a low degree of crystallinity). Furthermore, with this pin, even if the pressure applied to the pin during melting is small, the first portion is harder than when the entire pin is composed of the second portion, and the pin can smoothly enter the joint object, so that the occurrence of stuck can be suppressed. Furthermore, in this pin, the outer peripheral surface of the first portion is covered by the second portion in the shaft portion. Therefore, with this pin, regardless of the pressure applied to the pin during melting, the second portion of the shaft portion melts sufficiently when the pin is subjected to ultrasonic vibration, so that a relatively strong joint with the joint object can be realized. In other words, with this pin, a relatively good pull-out strength can be realized regardless of the magnitude of the pressure applied.

[0008] In the pin, the head portion may be covered by the second portion except for an upper surface portion of the first portion.

[0009] In this pin, for example, the second portion is exposed at the underside of the head, and therefore, when the pin is subjected to ultrasonic vibration, the underside of the head melts sufficiently, making it possible to realize a relatively strong bond with the objects to be joined.

[0010] The pin may be melted by receiving ultrasonic vibrations from an ultrasonic welding device, and the ultrasonic welding device may include an oscillator that generates ultrasonic power and a handpiece that generates ultrasonic vibrations based on the ultrasonic power generated by the oscillator, and in the head, a recess may be formed on the upper surface of the first part into which the tip of the handpiece is inserted.

[0011] In the pin, the length of the first portion in the longitudinal direction may be 70% or more of the length of the second portion in the longitudinal direction.

[0012] In this pin, the first portion extends to the vicinity of the tip of the shaft. Therefore, with this pin, ultrasonic vibrations are effectively propagated to the tip of the shaft compared to a case where the first portion does not extend to the vicinity of the tip of the shaft, and the pin can be melted smoothly. As a result, with this pin, for example, it is possible to prevent the pin from becoming stuck.

[0013] In the pin, the bioabsorbable material may be polylactic acid-polyglycolic acid (PLAGA). Effect of the Invention

[0014] According to the present invention, it is possible to provide a pin that can achieve relatively good pull-out strength regardless of the amount of pressure applied. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a diagram showing a schematic plan view of a pin. [Diagram 2] FIG. 2 is a schematic diagram showing a cross section taken along line II-II of FIG. [Diagram 3]FIG. 1 is a diagram showing a schematic configuration of an ultrasonic welding device. [Figure 4] FIG. 2 is a perspective view showing a typical chip. [Diagram 5] FIG. 13 is a diagram showing a schematic view of how pins are attached to protrusions of a chip. [Figure 6] FIG. 13 is a diagram for explaining how welding of a pin progresses. [Figure 7] FIG. 13 is a diagram to explain "neck breakage" that can occur when too much pressure is applied to the pin when it melts. [Figure 8] FIG. 13 is a diagram illustrating "stuck" that can occur if too little pressure is applied to the pin as it melts. [Figure 9] FIG. 13 is a diagram showing a schematic state in which the pin is welded. [Figure 10] 1 is a flowchart showing a manufacturing procedure of a pin. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter also referred to as "the present embodiment") will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated. Also, each drawing is drawn in a schematic manner with objects appropriately omitted or exaggerated for ease of understanding.

[0017] [1. Configuration] <1-1.Pin configuration> Fig. 1 is a diagram showing a schematic plan view of a pin 100 according to the present embodiment. Fig. 2 is a diagram showing a schematic cross section taken along line II-II of Fig. 1. The pin 100 melts, for example, when it receives ultrasonic vibrations from an ultrasonic welding device 10 (see Fig. 3) described below. That is, the ultrasonic welding device 10 is configured to melt the pin 100 by propagating ultrasonic vibrations to the pin 100, thereby welding the pin 100.

[0018] The pin 100 is made of a bioabsorbable material and is fused to a human bone. For example, a bone fracture is treated by fixing a plate placed at a position spanning the fracture site to the bone. The plate has a plurality of through holes for inserting the pins 100. Holes are formed in the bone at positions corresponding to the through holes of the plate. Each pin 100 is inserted into both the hole in the plate and the hole formed in the bone, and is fused to the bone by the ultrasonic welding device 10, thereby fixing the plate placed at a position spanning the fracture site to the bone. The pin 100 is used, for example, for such an application.

[0019] Considering that the pin 100 may be used for such purposes, it is preferable that the pull-out strength of the pin 100 is relatively high and is unlikely to vary depending on the user, such as a doctor. The pin 100 according to this embodiment has a relatively high pull-out strength and has structural features that make the pull-out strength unlikely to vary depending on the user. The structure of the pin 100 will be described in detail below.

[0020] 1 and 2, the pin 100 includes a shaft portion 110 and a head portion 120. The shaft portion 110 has a cylindrical shape and extends downward from the lower surface of the head portion 120. In a plan view, the shaft portion 110 has a perfect circular shape. The diameter of the cross section of the shaft portion 110 is substantially the same at any position in the vertical direction. The shape of the shaft portion 110 in a plan view does not necessarily have to be a perfect circular shape. The shape of the shaft portion 110 in a plan view may be, for example, an elliptical shape or a polygonal shape. The diameter of the cross section of the shaft portion 110 may not necessarily be substantially the same at any position in the vertical direction. For example, the diameter of the cross section of the shaft portion 110 may be gradually shortened from top to bottom, or may change so that a portion with a long diameter and a portion with a short diameter alternate from top to bottom.

[0021] The head 120 is formed at one end of the shaft portion 110. In a plan view, the head 120 has a perfect circular shape. In a plan view, the diameter of the head 120 is longer than the diameter of the shaft portion 110. Note that the shape of the head 120 in a plan view does not necessarily have to be a perfect circular shape. The shape of the head 120 in a plan view may be, for example, an elliptical shape or a polygonal shape.

[0022] The head 120 is formed with a recess H1 recessed in the direction in which the shaft 110 extends. The recess H1 forms a substantially cylindrical space. Although details will be described later, when a tip 230 (see FIG. 3) of a handpiece 200 included in the ultrasonic welding apparatus 10 is inserted into the recess H1, the pin 100 is held in the handpiece 200 by frictional force.

[0023] Moreover, the pin 100 includes a first portion 130 and a second portion 140. More specifically, each of the shaft portion 110 and the head portion 120 includes the first portion 130 and the second portion 140. The first portion 130 included in the shaft portion 110 and the first portion 130 included in the head portion 120 are formed continuously. Moreover, the second portion 140 included in the shaft portion 110 and the second portion 140 included in the head portion 120 are formed continuously.

[0024] Each of the first portion 130 and the second portion 140 is made of a bioabsorbable material. In the pin 100 according to this embodiment, the first portion 130 and the second portion 140 are made of the same kind of bioabsorbable material. This increases the mutual bonding strength of the first portion 130 and the second portion 140. The first portion 130 and the second portion 140 do not necessarily have to be made of the same kind of bioabsorbable material, and may be made of different kinds of bioabsorbable materials. The crystallinity of the first portion 130 is higher than the crystallinity of the second portion 140. The first portion 130 may be made of a crystallized crystalline resin, and the second portion 140 may be made of an amorphous resin. In the pin 100, the first portion 130 functions as a core.

[0025] Examples of bioabsorbable materials include polylactic acid-polyglycolic acid copolymers (PLAGA), poly-L-lactide (PLLA), polylactic acid (PLA), polyglycolic acid (PGA), polyglycolide, polylactide, poly-ε-caprolactone, lactide-glycolic acid copolymers, glycolide-ε-caprolactone copolymers, lactide-ε-caprolactone copolymers, polycitric acid, polymalic acid, poly-α-cyanoacrylate, poly-β-hydroxy acid, and polytrimethylene oxalate. Examples of suitable polysaccharides include polysaccharides such as poly(γ-benzyl-L-glutamate), poly(γ-methyl-L-glutamate), poly(L-alanine), and natural polymers such as polysaccharides including starch, alginic acid, hyaluronic acid, chitin, oxidized cellulose, chitosan, pectinic acid, and derivatives thereof, and proteins including gelatin, collagen, albumin, fibrin, and fibroin. Each of the first portion 130 and the second portion 140 is preferably made of PLAGA.

[0026] The first portion 130 includes a shaft portion 131 and a head portion 132. The shaft portion 131 has a cylindrical shape and extends downward from the lower surface of the head portion 132. In a plan view, the shaft portion 131 has a perfect circular shape. The diameter of the cross section of the shaft portion 131 is substantially the same at any position in the vertical direction. The shape of the shaft portion 131 in a plan view does not necessarily have to be a perfect circular shape. The shape of the shaft portion 131 in a plan view may be, for example, an elliptical shape or a polygonal shape. The diameter of the cross section of the shaft portion 131 may not necessarily be substantially the same at any position in the vertical direction. For example, the diameter of the cross section of the shaft portion 131 may gradually become shorter from top to bottom, or may change so that a portion with a long diameter and a portion with a short diameter alternate from top to bottom.

[0027] The head 132 is formed at one end of the shaft portion 131. In a plan view, the head 132 has a perfect circular shape. In a plan view, the diameter of the head 132 is longer than the diameter of the shaft portion 131. Note that the shape of the head 132 in a plan view does not necessarily have to be a perfect circular shape. The shape of the head 132 in a plan view may be, for example, an elliptical shape or a polygonal shape. In addition, a recess H1 is formed in the head 132.

[0028] In the shaft portion 110, the outer peripheral surface of the first portion 130 is covered by the second portion 140. In the head portion 120, the portion of the first portion 130 other than the upper surface portion SF1 is covered by the second portion 140. Specifically, in the head portion 120, the side surface portion SF2 and the lower surface portion SF3 are covered by the second portion 140. Note that a portion of the upper surface portion SF1 of the first portion 130 may be covered by the second portion 140.

[0029] In the shaft portion 110, the longitudinal length L1 of the first portion 130 is 70% or more and 95% or less of the longitudinal length L2 of the second portion 140, preferably 75% or more and 90% or less, and more preferably 80% or more and 85% or less.

[0030] <1-2. Configuration of ultrasonic welding equipment> Fig. 3 is a diagram showing a schematic configuration of ultrasonic welding apparatus 10. Referring to Fig. 3, ultrasonic welding apparatus 10 is used, for example, to weld pin 100 according to the present embodiment. Ultrasonic welding apparatus 10 includes oscillator 20 and handpiece 200. Oscillator 20 and handpiece 200 are connected via cable 30.

[0031] The oscillator 20 is configured to convert power supplied from a commercial power source into ultrasonic power and supply the ultrasonic power to the handpiece 200 via the cable 30. For example, the frequency of the ultrasonic power supplied by the oscillator 20 is approximately constant. Also, for example, the magnitude of the ultrasonic power supplied by the oscillator 20 (the product of the voltage value and the current value) is approximately constant.

[0032] The handpiece 200 includes a BL transducer (bolt-clamped Langevin type transducer) 210, a case 220, a horn 225, and a tip 230. The BL transducer 210 is configured to generate ultrasonic vibrations based on ultrasonic power supplied from the oscillator 20. The case 220 has, for example, a hollow cylindrical shape, and is configured to accommodate the BL transducer 210 therein. The horn 225 is attached to the tip of the BL transducer 210, and is configured to amplify the ultrasonic vibrations generated by the BL transducer 210.

[0033] Tip 230 is connected to the tip of horn 225, and is configured to propagate the ultrasonic vibration amplified by horn 225 to an object to be welded. Tip 230 may be configured to be detachable from horn 225, or may be configured integrally with horn 225. Tip 230 is made of, for example, titanium or ceramics.

[0034] FIG. 4 is a perspective view showing a schematic of the tip 230. As shown in FIG. 4, the tip 230 includes a base 235 and a protrusion 231. The base 235 has, for example, a substantially cylindrical shape. The protrusion 231 is formed on a tip surface FC1 of the base 235 and has a substantially cylindrical shape. The length (diameter) of the protrusion 231 in the width direction is shorter than the length (diameter) of the base 235 in the width direction. The protrusion 231 is configured to hold the pin 100 which is the welding object. Specifically, the protrusion 231 holds the pin 100 by being inserted into a recess H1 (see FIGS. 1 and 2) of the pin 100.

[0035] [2. Welding pins using ultrasonic welding equipment] Fig. 5 is a schematic diagram showing how pin 100 is attached to protrusion 231 of chip 230. Referring to Fig. 5, pin 100 is attached to protrusion 231, for example, in a state in which pin 100 is placed on fixed base 400. Fixed base 400 has a plurality of holes H2 formed therein, and each hole H2 houses a pin 100.

[0036] First, the protrusion 231 of the tip 230 is inserted into the recess H1 of the head 120. By inserting the protrusion 231 into the recess H1, the pin 100 is held on the tip 230 by frictional force. When the handpiece 200 is lifted with the tip 230 holding the pin 100, the pin 100 is removed from the fixed base 400. In this manner, the pin 100 is attached to the protrusion 231 of the tip 230.

[0037] Fig. 6 is a diagram for explaining how welding of the pin 100 progresses. Referring to Fig. 6, the horizontal axis indicates time. In this example, welding of the pin 100 is performed in a state in which the pin 100 is inserted into both a hole formed in the plate 500 and a hole formed in the bone 600. The plate 500 is fixed to the bone 600 by welding the pin 100.

[0038] At time t0, the pin 100 is pressed downward by the tip 230, and the pin 100 is gradually pushed into the hole of the bone 600. In this state, ultrasonic vibration is propagated from the tip 230 to the pin 100. When the pin 100 receives the ultrasonic vibration, frictional heat is generated between the pin 100 and each of the plate 500 and the bone 600, and the side of the pin 100 begins to melt. At time t1, the pin 100 is further pushed into the hole of the bone 600, and the melting of the pin 100 progresses further. At time t2, the melting of the shaft portion 110 progresses further, and the resin enters the gap of the hole of the bone 600. As a result, the pin 100 is firmly attached to the bone 600. In this way, the plate 500 is fixed to the bone 600 by the welding of the pin 100. Note that at time t2, the shaft portion 110 may be completely melted, or may not be completely melted. For example, at time t2, a portion of first portion 130 of shaft portion 110 may not be melted.

[0039] [3. Suppression of variation in pin pull-out strength] It is preferable that the pull-out strength of a pin used for the same purpose as pin 100 is relatively high and is less likely to vary depending on the user, such as a doctor. However, the present inventor(s) found that, for example, the pull-out strength of a pin made of a crystalline resin in an amorphous state or only an amorphous resin varies greatly depending on the pressure applied to the pin when it is melted.

[0040] FIG. 7 is a diagram for explaining "neck breakage" that can occur when too much pressure is applied to the pin when it is melted. Referring to FIG. 7, the pin 100X used for comparison is made of, for example, only amorphous resin or crystalline resin in an amorphous state. If too much force is applied from above to the pin 100X when it is melted, a large load is applied to the boundary between the shaft 110X and the head 120X (the neck portion of the pin 100X). This causes the neck portion of the pin 100X to deteriorate. As a result, the pull-out strength of the pin 100X decreases, making the pin 100X more likely to break (break) at the neck portion.

[0041] FIG. 8 is a diagram for explaining "stuck" that can occur when the pressure applied to the pin when melting the pin is too small. Referring to FIG. 8, if the force pressing the pin 100X from above when melting the pin 100X is too small, a part (S1) of the molten shaft portion 110X penetrates between the head portion 120X and the plate 500. This phenomenon is called "stuck." When stuck occurs, the length of the portion of the shaft portion 110X that penetrates into the bone 600 becomes shorter, and the joining strength between the pin 100X and the bone 600 decreases. As a result, the pull-out strength of the pin 100X decreases.

[0042] FIG. 9 is a schematic diagram showing a state in which the pin 100 according to the present embodiment is welded. Referring to FIG. 9, in the pin 100, the first portion 130 having a high degree of crystallinity is continuously formed over the shaft portion 110 and the head portion 120. Therefore, even if the pressure applied to the pin 100 during melting is large, the pin 100 can suppress deterioration of the pin 100 at the boundary (neck portion) between the shaft portion 110 and the head portion 120, as compared with the case in which the entire pin is made of only amorphous crystalline resin or amorphous resin. Furthermore, even if the pressure applied to the pin 100 during melting is small, the pin 100 can smoothly advance into the bone 600 because the first portion 130 is hard, as compared with the case in which the entire pin is made of only amorphous crystalline resin or amorphous resin, and thus can suppress the occurrence of stuck. Furthermore, in the pin 100, the outer peripheral surface of the first portion 130 in the shaft portion 110 is covered by the second portion 140. Therefore, with pin 100, regardless of the pressure applied to pin 100 during melting, when pin 100 is subjected to ultrasonic vibration, second portion 140 of shaft 110 melts sufficiently, thereby achieving a relatively strong bond with bone 600. In other words, with pin 100, relatively good pull-out strength can be achieved regardless of the magnitude of pressure applied.

[0043] In addition, in the pin 100, for example, the second portion 140 is exposed at the underside of the head 120. Therefore, according to the pin 100, when the pin 100 is subjected to ultrasonic vibration, the underside of the head 120 is sufficiently melted, so that a relatively strong bond with the plate 500 and the bone 600 can be realized.

[0044] Furthermore, in the pin 100, the first portion 130 reaches close to the tip of the shaft portion 110. Therefore, in the pin 100, ultrasonic vibrations are more effectively propagated to the tip of the shaft portion 110 than in a case where the first portion 130 does not reach close to the tip of the shaft portion 110, and smooth melting of the pin 100 can be achieved. As a result, the pin 100 can, for example, prevent the occurrence of sticking.

[0045] [4. Pin manufacturing procedure] 10 is a flow chart showing the manufacturing procedure of the pin 100. Each step shown in this flow chart is performed by an operator using various manufacturing devices.

[0046] 10, an operator injection-moldes the first portion 130 (amorphous state) by using an injection molding machine (step S100). For example, PLAGA is used to mold the first portion 130. A first mold is used to mold the first portion 130. An operator anneals the first portion 130 (amorphous state) by using an annealing device (step S110).

[0047] After that, the worker places the crystallized first portion 130 in a second mold of an injection molding machine, and uses the injection molding machine to injection mold the second portion 140 around the first portion 130 (step S120). For example, PLAGA is used to mold the second portion 140. The second mold is a size larger than the first mold. In this way, the pin 100 is manufactured.

[0048] The annealing process may cause the first portion 130 to shrink. However, since the second portion 140 is injection molded around the first portion 130, the pin 100 as a whole will have a specified size even if the first portion 130 shrinks during the annealing process.

[0049] [5. Features] As described above, in the pin 100 according to the present embodiment, the first portion 130 having a high degree of crystallinity is continuously formed over the shaft portion 110 and the head portion 120. Therefore, even if the pressure applied to the pin 100 during melting is large, the pin 100 can be prevented from deteriorating (e.g., causing neck breakage) at the boundary between the shaft portion 110 and the head portion 120, as compared to the case where the entire pin 100 is composed of the second portion 140 (a portion with a low degree of crystallinity). Furthermore, even if the pressure applied to the pin 100 during melting is small, the pin 100 can be prevented from sticking because the first portion 130 is harder and the pin 100 can smoothly enter the joining object, as compared to the case where the entire pin 100 is composed of the second portion 140. Furthermore, in the pin 100, the outer peripheral surface of the first portion 130 in the shaft portion 110 is covered by the second portion 140. Therefore, with pin 100, regardless of the pressure applied to pin 100 during melting, when pin 100 is subjected to ultrasonic vibration, second portion 140 of shaft 110 melts sufficiently, thereby realizing a relatively strong bond with the object to be joined. In other words, with pin 100 according to the present embodiment, relatively good pull-out strength can be achieved regardless of the magnitude of pressure applied.

[0050] [6. Other embodiments] The concept of the above embodiment is not limited to the embodiment described above. Hereinafter, an example of another embodiment to which the concept of the above embodiment can be applied will be described.

[0051] <6-1> In the above embodiment, in the shaft 110 of the pin 100, the length L1 in the longitudinal direction of the first portion 130 is set to be 70% or more and 95% or less of the length L2 in the longitudinal direction of the second portion 140. However, the length L1 in the longitudinal direction of the first portion 130 does not have to be 70% or more of the length L2 in the longitudinal direction of the second portion 140. For example, the length L1 in the longitudinal direction of the first portion 130 may be less than 70% of the length L2 in the longitudinal direction of the second portion 140. For example, it is sufficient that a part of the first portion 130 is located at the boundary between the shaft 110 and the head 120.

[0052] <6-2> In the above embodiment, in the head 132 of the first portion 130, the side surface portion SF2 and the lower surface portion SF3 are entirely covered by the second portion 140. However, the side surface portion SF2 and the lower surface portion SF3 do not necessarily have to be entirely covered by the second portion 140. In other words, a portion of the side surface portion SF2 and the lower surface portion SF3 do not have to be covered by the second portion 140.

[0053] <6-3> In the above embodiment, the second portion 140 is not annealed. However, the second portion 140 may also be annealed. In this case, the second portion 140 is annealed so that the crystallinity of the second portion 140 is less than the crystallinity of the first portion 130. By also annealing the second portion 140, the decomposition rate of the second portion 140 can be reduced.

[0054] The above describes the embodiments of the present invention by way of example. That is, the detailed description and the accompanying drawings are disclosed for the purpose of illustrative description. Therefore, some components described in the detailed description and the accompanying drawings may be non-essential components for solving the problem. Therefore, just because the non-essential components are described in the detailed description and the accompanying drawings, it should not be immediately determined that the non-essential components are essential.

[0055] Moreover, the above-described embodiments are merely examples of the present invention in every respect. Various improvements and modifications of the above-described embodiments are possible within the scope of the present invention. For example, at least a part of the configuration of any of the embodiments may be combined with at least a part of the configuration of any of the other embodiments. In other words, in implementing the present invention, specific configurations can be appropriately adopted according to the embodiment. [Explanation of symbols]

[0056] 10 ultrasonic welding device, 20 oscillator, 30 cable, 100, 100X pin, 110, 110X, 131 shaft portion, 120, 120X, 132 head portion, 130 first portion, 140 second portion, 200 handpiece, 210 BL transducer, 220 case, 225 horn, 230 tip, 231 protrusion portion, 235 base portion, 400 fixing base, 500 plate, 600 bone, FC1 tip surface, H1 recess, H2 hole, SF1 upper surface portion, SF2 side portion, SF3 lower surface portion.

Claims

1. A pin that melts when subjected to ultrasonic vibrations from an ultrasonic welding device, Constructed of a bioabsorbable material, A shaft portion, a head portion formed at one end of the shaft portion, Each of the shaft portion and the head portion is a first portion having a first crystallinity; a second portion having a second crystallinity lower than the first crystallinity; The first portion included in the shaft portion and the first portion included in the head portion are formed continuously, The second portion included in the shaft portion and the second portion included in the head portion are formed continuously, A pin, wherein the outer peripheral surface of the first portion of the shaft portion is covered by the second portion.

2. The pin according to claim 1 , wherein a portion of said head portion other than an upper surface portion of said first portion is covered by said second portion.

3. The ultrasonic welding apparatus includes: an oscillator for generating ultrasonic power; a handpiece that generates the ultrasonic vibration based on ultrasonic power generated by the oscillator, The pin according to claim 2 , wherein the head portion has a recess formed on an upper surface of the first portion into which the tip end of the handpiece is inserted.

4. The pin according to claim 1 , wherein the length of the first portion in the longitudinal direction of the shaft is 70% or more of the length of the second portion in the longitudinal direction.

5. The pin according to any one of claims 1 to 3, wherein the bioabsorbable material is polylactic-co-glycolic acid (PLAGA).

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