JP2017108916A - Screw for soft tissue fixation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw for soft tissue fixation configured to be easily screwed without being strongly pressed in with a rotary tool, and reliably fixing a soft tissue by causing a screw body excluding a screw tip end to exert substantially equal large fixing strength.SOLUTION: A screw 10 for soft tissue fixation includes: a screw body 10a, where an outside diameter of a male screw 1 is constant; and a screw tip end 10b, where the outside diameter of the male screw 1 is reduced towards a screw tip end. The screw 10 is so configured that the male screw of the screw tip end has a narrow-width screw thread portion 1b whose width is narrower than the width D of a screw thread part 1a of the male screw of the screw body. The outside diameter of the male screw of the screw body is made constant so as to exert a substantially equal large fixing strength, the outside diameter of the male screw of the screw tip end part is reduced, and the male screw has a narrow-width screw thread portion 1b so as to be easily screwed in without being strongly pressed in.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a screw suitable for fixing soft tissues such as tendons and ligaments, and more particularly, to a soft tissue fixing screw that can be easily screwed into a soft tissue fixing hole formed in a living bone and can securely fix the soft tissue in the hole. .

  As a screw for fixing soft tissues such as tendons and ligaments in a hole formed in a living bone, the outer diameter and valley diameter of the male screw are gradually increased from the screw tip to the screw rear end, and the screw crest of the male screw is increased. An interference screw having a gradually widened portion is known (Patent Document 1).

  Also, the width of the top of the screw thread of the male screw is the same throughout the screw, and the width of the top of the screw thread of the male screw at the tip of the screw is widened in the same way as the width of the top of the screw thread of the male screw other than the screw tip. An interference screw has also been developed.

Special table 2014-508550 gazette

  However, like the screw of the former patent document 1, the outer diameter and valley diameter of the male screw are gradually increased from the screw front end toward the screw rear end, and the width of the screw thread top portion of the male screw is gradually increased. When the screw is screwed into the hole of the living bone into which the end of the soft tissue is inserted, the screw tip or the middle part of the screw (the outer diameter and valley diameter of the male screw are not large and the width of the screw crest is not wide. The tip of the screw and the center of the screw are strongly pressed against the inner surface of the hole in the living bone and the insertion end of the soft tissue, and the male screw is less likely to bite deeply. Since the screw rear end with a large width at the top of the screw thread is strongly pressed against the inner surface of the hole in the living bone and the insertion end of the soft tissue, the male screw with a large outer diameter digs deeply, thereby fixing the soft tissue. Fixing strength is increased to concentrate the screw rear end, there is a problem that it is difficult to exert a substantially uniform large fixing strength throughout the screw.

  Also, as in the latter screw, the width of the screw thread top of the male screw at the screw tip is widened in the same manner as the width of the screw thread top of the male screw other than the screw tip, and the end of the soft tissue is inserted When screwing a screw into a living bone hole, it is difficult to initially bite into the inner surface of the hole in the living bone or the insertion end of soft tissue, so the screw tip of the screw is difficult to bite. There is a problem that it is difficult to screw in unless it is rotated while being pushed.

  The present invention has been made in view of the above problems, and the problem to be solved is that the screw body can be easily screwed in without being strongly pushed in by a rotating tool, and the screw body portion excluding the screw tip portion is almost equally large and fixed. An object of the present invention is to provide a soft tissue fixing screw that exhibits strength and can securely fix soft tissue.

  In order to solve the above problems, the soft tissue fixing screw of the present invention includes a screw main body portion in which the outer diameter of the male screw is constant, and a screw tip portion that gradually decreases in diameter as the outer diameter of the male screw approaches the screw tip. The male screw at the tip of the screw has a portion where the width of the screw top is narrower than the width of the screw top of the male screw of the screw main body. is there.

The screw tip portion of the soft tissue fixing screw of the present invention gradually increases as the outer diameter of the male screw approaches the screw tip so that the outline connecting the screw thread tops of the male screw in the longitudinal cross-sectional view is a curve that swells outward. It is desirable that the diameter is reduced.
Moreover, it is desirable that the male screw of the soft tissue fixing screw of the present invention is a multiple thread.

  When the outer diameter of the male screw of the screw main body occupying most of the screw is constant like the screw for soft tissue fixation of the present invention, the screw of the present invention is screwed into the hole of the living bone into which the end of the soft tissue is inserted. When this is the case, the screw body is almost uniformly pressed against the inner surface of the hole and the insertion end of the soft tissue over its entire length, and the male screw having a constant outer diameter is substantially evenly connected to the inner surface of the hole and the insertion end of the soft tissue. Since the soft tissue is fixed by biting deeply, the fixing strength of the soft tissue does not concentrate on a part (rear end portion) of the screw as in the screw of Patent Document 1, and the screw main body portion is almost the entire length. The soft tissue can be reliably fixed by exhibiting an evenly large fixing strength.

  Moreover, as the soft tissue fixing screw of the present invention, the external diameter of the male screw at the screw tip gradually decreases as the screw approaches the screw tip, and the male screw at the screw tip is the screw of the male screw at the screw body. If there is a part where the width of the screw peak is narrower than the width of the peak, the screw tip with the outer diameter of the male screw reduced is inserted into the hole in the living bone where the soft tissue end is inserted The screw is easy to push because the narrow part of the top of the screw thread at the tip of the screw bites into the inner surface of the hole and the insertion end of the soft tissue. Can be screwed into.

In particular, the screw tip is gradually reduced in diameter as the outer diameter of the male screw approaches the screw tip so that the outline connecting the screw thread tops of the male screw in the longitudinal sectional view is a curve that bulges outward. This makes it easier to narrow the width of the top of the thread of the male screw, and it is easier to screw it into the soft tissue fixing hole of the living bone.
In addition, a screw whose male thread is a multi-thread thread has a distance (lead L) that travels in one rotation is a product of pitch P and the number n of threads, that is, L = nP, and is necessary for screwing the screw. The number of rotations is reduced and the efficiency of screwing work is improved.

It is a front view which shows the screw for soft tissue fixation which concerns on one Embodiment of this invention. It is a top view of the screw. It is a bottom view of the screw. It is a longitudinal cross-sectional view of the screw. It is a schematic sectional drawing which shows one example of use of the screw. It is a schematic explanatory drawing which shows the other usage example of the screw. (A) is a front view of a rotating tool (driver) used for screwing the screw, (b) is a longitudinal sectional view of a tip portion of the rotating tool, and (b) is an end view of the tip of the rotating tool.

  Hereinafter, embodiments of a soft tissue fixing screw according to the present invention will be described in detail with reference to the drawings.

  1 is a front view showing a soft tissue fixing screw according to an embodiment of the present invention, FIG. 2 is a plan view of the screw, FIG. 3 is a bottom view of the screw, FIG. 4 is a longitudinal sectional view of the screw, FIG. Is a schematic sectional view showing an example of use of the screw, and FIG. 6 is a schematic explanatory view showing another example of use of the screw.

  1 to 4, for example, as shown in FIG. 5, by screwing the screw 10 into a hole 30 a of a living bone 30 into which an end of a soft tissue 20 such as a tendon or a ligament is inserted, This is a so-called “interference screw” that fixes the end of the soft tissue 20 to the living bone 30.

  As shown in FIGS. 1 and 4, the soft tissue fixing screw 10 includes a screw body 10a and a screw tip 10b, and a male screw 1 is formed over the entire length of the screw. The male screw 1 is preferably a multi-threaded screw in order to increase the distance (lead) that travels when the screw 10 is rotated once to improve the efficiency of the screwing operation. In the screw 10 of this embodiment, As shown in FIG. 2, by forming three male screws 1, 1, 1 at intervals of 120 °, leads for three pitches can be obtained when the screw 10 is rotated once. .

In the screw main body portion 10a, the outer diameter A of the male screw 1 is constant over the entire length of the main body portion, and the valley diameter B of the male screw 1 is also constant.
On the other hand, the screw tip portion 10b is gradually reduced in diameter as the outer diameter of the male screw 1 approaches the screw tip (lower end in FIGS. 1 and 4), and the valley diameter of the male screw 1 is also gradually reduced. Yes. More specifically, the screw tip portion 10b of this embodiment has an arcuate or substantially arcuate curve in which a contour line L1 connecting the screw thread tops of the male screw 1 in the longitudinal sectional view of FIG. The outer diameter of the male screw 1 is gradually reduced as it approaches the tip of the screw, and the valley diameter of the male screw 1 is a straight line (tapered) in which a line L2 connecting the bottom of the male screw 1 is inclined with respect to the screw axis CL. The diameter is gradually reduced so as to be a line.

As shown in FIGS. 1 and 4, the male screw 1 formed on the screw 10 has a flat thread top 1a, and the width D of the screw top 1a of the male screw 1 in the screw main body 10a. Is constant.
On the other hand, the male screw 1 in the screw tip portion 10b has a portion 1b in which the width of the screw top is narrower than the width D of the screw top of the male screw 1 in the screw main body 10a. That is, in the vicinity of the boundary between the screw main body portion 10a and the screw front end portion 10b, the male screw 1 of the screw front end portion 10b has a width D of the screw thread top portion 1a of the male screw 1 of the screw main body portion 10a. However, the width of the top of the screw thread gradually becomes narrower as it approaches the tip of the screw, and the width of the top of the screw thread becomes extremely narrow near the tip of the screw, resulting in a male screw with a sharp point on the top of the screw thread. .

  Moreover, the trough part 1c of the external thread 1 in the screw main body part 10a and the screw tip part 10b is formed in a substantially semicircular shape as shown in the longitudinal sectional view of FIG. When screwing into the soft tissue fixing hole, the stress is relaxed from being concentrated in the deepest portion of the valley portion 1c, and the strength is increased.

  An engagement hole 2 is formed in the screw 10 so as to overlap the screw axis CL so that the tip engagement portion 40a of the rotating tool (driver shaft) 40 shown in FIG. Has been. 2 and 4, the engagement hole 2 is formed in a hexagonal hole having a tapered shape (downwardly narrowed in the drawing), and a distal end engaging portion 40a (a distal end) of the rotating tool 40. When the hexagonal cylindrical tip engagement portion with a tapered taper is inserted into the engagement hole 2 from the rear side, the hexagonal outer surface of the tip engagement portion 40a becomes the hexagonal inner surface of the engagement hole 2. They are brought into contact with each other so that they cannot be idle.

  As shown in FIGS. 3 and 4, a small round hole 3 for inserting a Kirschner wire (not shown) is formed at the tip (lower end in the drawing) of the hexagonal engagement hole 2, As shown in FIG. 7B, a through hole 40b having a different diameter for inserting the Kirschner wire is also formed inside the rotating tool 40 over the entire length of the rotating tool.

Although the dimension of each part of this screw 10 is not specifically limited, A suitable dimension is illustrated below for reference.
The outer diameter D of the male screw 1 in the screw body 10a is about 4 to 10 mm, the valley diameter B is about 3 to 8.5 mm, the outer diameter C of the screw tip is about 2 to 5 mm, and the length of the screw body 10a is 5. About 30 mm, the length of the screw tip portion 10b is about 4-15 mm, the pitch P is about 1.5-3 mm, the width D of the screw peak at the screw body portion 10a is about 0.3-0.8 mm, the screw tip The width of the top of the screw thread in the portion 10b is D or less, the radius of curvature when the outline L1 of the screw tip 10b is an arcuate curve is about 5 to 25 mm, and the taper line L2 connecting the valley bottom of the screw tip 10b. The inclination angle with respect to the screw axis CL is 4 to 25 °.

The screw 10 is a crystalline biodegradable and absorbable polymer, for example, having a crystallinity of 5% or more and a viscosity average molecular weight of about 150,000 to 600,000 in order to have a strength equal to or higher than that of a living bone. It is preferable to produce with poly-L-lactic acid, polyglycolic acid, etc., and especially with a bioceramic powder that is bioabsorbable and bioactive within a range of 30 to 60% by mass. preferable. The screw manufactured with the biodegradable absorbable polymer containing such bioceramics powder is hydrolyzed inside the pores of the living bone, and the bone tissue is finally formed (conductive) inside the screw. Therefore, there is an advantage that the whole bone is completely replaced.
In addition to the above, biodegradable and absorbable polymers include amorphous or mixed poly-D, L-lactic acid, L-lactic acid and D, L-lactic acid, and lactic acid. A copolymer of lactic acid and glycolic acid, a copolymer of lactic acid and caprolactone, a copolymer of lactic acid and ethylene glycol, a copolymer of lactic acid and para-dioxanone, and the like can also be used.

Bioceramic powders contained in biodegradable and absorbable polymers include uncalcined and uncalcined hydroxyapatite, calcium phosphate, dicalcium phosphate, triflate having good bone conduction (induction) ability and good biocompatibility. Powders such as calcium phosphate, tetracalcium phosphate, octacalcium phosphate, calcite, serabital, diopsite, natural coral are preferably used. Among them, uncalcined and uncalcined hydroxyapatite, tricalcium phosphate, octacalcium phosphate. Is highly preferred because it has high biological activity, excellent bone conduction (induction) ability, low toxicity, and is absorbed into the living body in a short period of time.
In some cases, the biodegradable absorbable polymer may contain biological bone growth factors such as BMP, TGF-β, EP4, b-FGF, and PRP.

This screw 10 is manufactured by the following method, for example.
First, a biodegradable absorbent polymer or a biodegradable absorbent polymer containing bioceramic powder is molded to form a cylindrical molded body, and then this cylindrical molded body is shown in FIGS. The screw 10 is cut into a screw shape as shown in FIG. In that case, when a cylindrical molded body is made by cutting by means of compression molding or forging, the cylindrical molded body becomes dense and the polymer molecules and crystals are three-dimensionally oriented, so the strength is even greater. The screw 10 can be obtained. Alternatively, the screw 10 may be manufactured by cutting a cylindrical shaped body in which polymer molecules are uniaxially oriented by stretching.

  As shown in FIG. 5, the basic usage of the soft tissue fixing screw 10 as described above is to screw the screw 10 into a hole 30a of a living bone 30 into which an end of the soft tissue 20 such as a tendon or a ligament is inserted. This is a mode in which the soft tissue 20 is fixed to the hole 30 a of the living bone 30 by biting the male screw 1 into the inner surface of the hole 30 a and the insertion end of the soft tissue 20.

  In addition, as another use mode, for example, a case where it is used for transplantation reconstruction of a tendon of a knee joint as shown in FIG. In this mode of use, holes 50a and 60a are made in the femur 50 and the tibia 60, the diameter of the hole is enlarged and adjusted by a dilator (not shown), and then transplanted so as to have grafted bone pieces 70a and 70a at both ends. A tendon 70 (soft tissue) is passed through these holes 50a and 60a, and a distal end engaging portion 40a (not shown) of the rotary tool 40 (not shown) is inserted into the engaging hole 2 (not shown) of the screw 10. At the same time, a Kirschner wire (not shown) is inserted into the through hole 40b (not shown) of the rotating tool and the round hole 3 (not shown) of the screw 10, and while rotating the rotating tool, The screw 10 is screwed in an appropriate direction between the graft bone piece 70a and the male screw 1 of the screw 10 is bitten into the inner surface of the hole 50a and the surface of the graft bone piece 70a, and the graft tendon is inserted into one hole 50a. One end of 70 The graft bone piece 70a is fixed, and similarly, the screw 10 is screwed between the inner surface of the other hole 60a and the graft bone piece 70a at the other end of the graft tendon 70, and the graft bone fragment at the other end is inserted into the other hole 60a. 70a is fixed.

  As described above, when the soft tissue fixing screw 10 is screwed into the living bone hole 30a into which the end of the soft tissue 20 is inserted or the living bone holes 50a and 60a into which the graft bone pieces 70a at both ends of the graft tendon 70 are inserted. The screw main body 10a having a constant outer diameter of the male screw 1 is almost uniformly pressed against the inner surface of the holes 30a, 50a, 60a and the insertion end of the soft tissue 20 or the grafted bone piece 70a over the entire length thereof. The male screw 1 of the portion 10a bites into the inner surfaces of the holes 30a, 50a, 60a, the insertion end of the soft tissue 20 and the grafted bone piece 70a almost equally deeply, and the grafted bone fragments at the insertion end of the soft tissue 20 and both ends of the graft tendon 70 Since 70a is fixed, the fixing strength of the soft tissue does not concentrate on a part (rear end portion) of the screw as in the screw of Patent Document 1, and the screw main body portion 10a extends over its entire length. It exerts a uniform high fixing strength can be reliably fix the soft tissue 30 and the reconstructed ligament 70.

  In addition, the soft tissue fixing screw 10 gradually decreases in diameter as the outer diameter of the male screw 1 of the screw tip portion 10b approaches the screw tip, and the male screw of the screw tip portion 10b becomes the male screw 1 of the screw main body portion 10a. Therefore, the screw tip portion 10b with the outer diameter of the male screw 1 is reduced between the end portion of the soft tissue 20 and the both ends of the graft tendon 70. It is easy to insert into the bones 30a, 50a, 60a of the living bone into which the bone graft 70a has been inserted, and the screw top of the male screw 1 at the screw tip 10b can be rotated by simply rotating the screw 10 with the rotating tool 40. The narrow portion of the bite bites into the inner surfaces of the holes 30a, 50a, 60a, the insertion end portion of the soft tissue 20, and the grafted bone fragments 70a at both ends of the graft tendon 70, so that the screw 10 can be easily Flip can be writing.

  In particular, the screw tip portion 10b of the soft tissue fixing screw 10 has a male screw so that an outline L1 connecting the top of the screw thread of the male screw 1 in the longitudinal sectional view is an arcuate or substantially arcuate curve that bulges outward. The outer diameter of the male screw 1 is gradually reduced as it approaches the tip of the screw, and the valley diameter of the male screw 1 is screwed so that the line L2 connecting the valley bottom of the male screw 1 becomes a tapered line inclined with respect to the screw axis CL. Since the diameter is gradually reduced as it approaches the tip, the height of the thread relative to the valley is relatively large, and the width of the top of the thread is easily narrowed, and the holes 30a and 50a of the living bone are correspondingly increased. , 60a, it becomes easier to screw.

  Next, the “screwing ease confirmation test” conducted for examining the effect of the screw for soft tissue fixation of the present invention will be described.

[Screwability confirmation test]
A simulated bone [SAWBONES block (20 pcf)] made of polyurethane foam satisfying the ASTM (F1839-01) standard is drilled with a pilot hole having a diameter (6 mm) smaller than the outer diameter of the male screw of the screw main body. The bone was attached to the testing machine [TNX-10 manufactured by Nidec Symposium Co., Ltd.], and the screw of the example having the dimensions shown in [Table 1] below was held by the screwdriver and attached to the testing machine. .
Then, the driver is lowered while confirming the numerical value of the load meter, and while applying the load of 5N, 10N, 20N, 30N, 40N, and 50N in sequence, the driver is rotated at a speed of 2.5 rpm in each load state. A test was performed, the screwed state of the screw after the test was confirmed, and the load into which the screw was screwed was examined. The results are shown in [Table 2] below.
For comparison, the load into which the screw was screwed was examined in the same manner as described above for the screw of the comparative example having the dimensions of the respective parts shown in [Table 1] below. The results are shown in [Table 2] below.

  In [Table 2], “◯” indicates that the screw can be screwed, and “x” indicates that the screw is idle and cannot be screwed.

As shown in [Table 1], the screw of the example and the screw of the comparative example have the same dimensions except for the difference in the width of the screw top at the screw tip. As shown in Table 2, the width of the top of the screw thread at the top of the screw is the same as the width of the top of the screw at the top of the screw body and 0.8 mm. Is 50N or more. On the other hand, the width of the screw crest at the screw tip is 0.3 mm, and the screw of the embodiment having a narrow width of about 1/3 of the width of the screw crest of the screw body is minimum as shown in [Table 2]. It is possible to screw in only by applying a load of 20N.
As a result, the screw of the present invention is rotated while being pushed a little with a rotating tool (driver shaft), and the narrow portion of the top of the screw thread at the tip of the screw bites into the soft tissue fixing hole of the living bone. It was proved that the screw can be screwed much more easily than the screw of the comparative example in which the width of the screw thread top at the screw tip is wide.

  The screw of the present invention can be applied to, for example, a bone fixing screw other than the soft tissue fixing screw.

DESCRIPTION OF SYMBOLS 1 Male screw 1a Thread peak part of the male screw of a screw main-body part 1b The part where the width | variety of the screw thread top part of a male screw in a screw front-end | tip part is narrow 10 Screw for soft tissue fixation 10a Screw main-body part 10b Screw front-end | tip part L1 Outline that bulges outside to connect parts

Claims (3)

  A screw having a constant external diameter of a male screw, and a screw tip portion that gradually decreases in diameter as the external diameter of the male screw approaches the screw tip, wherein the male screw at the screw tip portion is A screw for soft tissue fixation, characterized in that it has a portion where the width of the top of the screw thread is narrower than the width of the top of the thread of the male screw of the screw body.   The screw tip portion is gradually reduced in diameter as the outer diameter of the male screw approaches the screw tip so that the outline connecting the screw thread tops of the male screw in the longitudinal sectional view is a curve that bulges outward. The soft tissue fixing screw according to claim 1.   The screw for soft tissue fixation according to claim 1 or 2, wherein the male screw is a multi-thread screw.

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