JPH11262491A - Bone stretching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bone stretching apparatus which can stretch a bone at a curved part and which can be miniaturized so that it can be worn under the skin. SOLUTION: This bone stretching apparatus 1 has a plate-shaped rail 2 having a predetermined length, a moving block 3 being movable in the direction of the axis of the plate-shaped rail 2 and secured to a bone and adapted for the plate-shaped rail 2, and two bone securing members 4, 5 provided near both ends of the plate-shaped rail 2. The plate-shaped rail 2 is formed of a hard material, can be forcibly curved and deformed toward the side faces of the plate-shaped rail 2, and has a rack 21 formed on its upper surface. The moving block 3 has a rotating shaft 33 having a worm gear which meshes with the rack 21, and the moving block 3 is movable to the front end or rear end of the plate-shaped rail 2 by rotating the rotating shaft 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bone stretching device used in oral surgery, orthopedic surgery and the like, and more particularly to a bone stretching device suitably used in a bone stretching compression connection method.

[0002]

2. Description of the Related Art For the treatment of malignant tumors occurring in the mandible and the like, the mandible is partially resected. In the mandibular defect caused by this partial resection, a substitute made of metal or plastic is buried, or autologous bone collected from another part of the body is transplanted. However, implantation as an alternative is not sufficiently compatible with the living body, and autologous bone grafting requires surgical invasion of a normal site. So recently,
In the field of orthopedics and oral surgery, a bone lengthening treatment using a bone lengthening treatment has been proposed. Examples of such a device used for the bone lengthening treatment include, for example, Japanese Patent Application Laid-Open No. Hei.
No. 501092 (International Publication WO89 / 11254)
There are the following. The present applicant has proposed a bone distraction device disclosed in Japanese Patent Application Laid-Open No. 9-215699.

[0003]

SUMMARY OF THE INVENTION The above-mentioned Japanese Translation of PCT International Publication No. Hei 3-501
The device disclosed in Japanese Patent Publication No. 092 is effective as a compression and stretching device for bone. However, the device disclosed in this publication is based on the premise that the support unit is moved linearly on the threaded rod, and is not intended for use in a curved portion. For this reason, if the screw rod is forcibly bent, the movement of the support unit becomes difficult, and the rotation of the nut for fixing the support unit to the screw rod also becomes impossible.
Japanese Patent Application Laid-Open No. 9-215699 can extend a bone at a curved portion, and exhibits a sufficient effect. However, the device is relatively large, and sometimes hinders daily life while wearing the device. In view of the above, the present invention provides a bone stretching device that can stretch a bone at a curved portion, can be reduced in size, and can be worn under the skin.

[0004]

To achieve the above object, a plate-like rail having a predetermined length, a moving block movable in the axial direction of the plate-like rail and fixed to a bone are provided. A bone extension device comprising two bone fixing members provided near both ends of the plate-like rail, wherein the plate-like rail is formed of a hard material and is forced in a side direction of the plate-like rail. The moving block further comprises a rack formed on an upper surface or a lower surface of the plate-shaped rail, and the moving block rotatably includes a rotating shaft having a worm gear meshing with the rack of the plate-shaped rail. The moving block is a bone stretching device that is movable to the front end side or the rear end side of the plate-like rail by rotating the rotary shaft.

[0005] The moving block and the bone fixing member preferably have a large number of holes for fixing screws. Further, the moving block has an insertion opening for the plate-shaped rail formed on both side surfaces, a plate-shaped rail passage communicating with both the insertion openings, and an outer surface of the plate-shaped rail provided in the plate-shaped rail passage. It is preferable to have a bearing mechanism that is in contact or close proximity. Further, the bearing mechanism is, for example, a bearing mechanism using a needle roller. Preferably, the rotating shaft includes a wrench connection protruding from the moving block, and a wrench for rotating the rotation shaft is attached to the wrench connection. The wrench is preferably detachable from the wrench connection portion of the rotary shaft. Further, the wrench and the wrench connection portion, in a state where both are connected,
It is preferable to have a clearance capable of moving a wrench at least in the side direction of the plate-like rail. Further, the bearing mechanism may include, for example, a first set of needle rollers including two needle rollers provided substantially parallel to each other at a predetermined distance and substantially parallel to the side surfaces of the plate-shaped rail, And a second set of needle rollers comprising two needle rollers provided substantially parallel to each other and parallel to the first set of needle rollers.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The bone stretching device of the present invention can be said to be, in other words, a stretching device for bone compression connection. The bone extension device of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a state in which the bone extension device of the present invention is slightly curved. FIG.
1 is a front view of a state in which a bone stretching device of the present invention is not bent. FIG. 3 is a plan view showing a state where the bone extension device of the present invention is not bent. FIG. 4 is a plan view showing a state in which a wrench has been removed from the bone extension device of the present invention. FIG. 5 is a plan view showing a state in which the bone extension device of the present invention is slightly curved. FIG.
FIG. 2 is an enlarged perspective view of the vicinity of a moving block used in the bone extension device of the present invention. FIG. 7 is an exploded perspective view for explaining the internal structure of the moving block used in the bone extension device of the present invention. FIG. 8 is an explanatory diagram for explaining an engagement state between a rotary shaft and a plate-shaped rail used in the bone extension device of the present invention. FIG. 9 is a cross-sectional view of a tip portion of a wrench and a rotating shaft used in the bone extension device of the present invention. FIG. 10 is a sectional view taken along line AA of FIG. FIG.
FIG. 10 is a sectional view taken along the line BB of FIG. 9. FIG. 12 is an explanatory diagram for explaining the operation of the bone extension device of the present invention. FIG.
FIG. 3 is an explanatory diagram for explaining the operation of the bone extension device of the present invention.

The bone stretching device 1 of the present invention comprises a plate-like rail 2 having a predetermined length, a moving block 3 which is movable in the axial direction of the plate-like rail 2 and is fixed to the bone, There are provided two bone fixing members 4 and 5 provided near both ends of the rail 2. The plate-like rail 2 is formed of a hard material, is capable of being forcedly bent and deformed in the side direction of the plate-like rail 2, and further includes a rack 21 formed on the upper or lower surface of the plate-like rail 2. The moving block 3 houses a rotating shaft 33 provided with a worm gear 34 meshing with the rack 21 of the plate-shaped rail 2 so as to be rotatable from the outside. It can move to the side or the rear end side.

The bone stretching device of the present invention comprises: a plate-like rail 2 having a predetermined length; a moving block 3 which is movable in the axial direction of the plate-like rail 2 and is fixed to a bone; Two bone fixing members 4 fixed near both ends of 2
5 is provided.

The plate-like rail 2 is formed in a slender plate-like shape from a hard material. In this embodiment, as shown in FIGS. 1, 2, 4, 6, 7 and 8, A rack 21 is formed entirely. The rack 21 meshes with a worm gear 34 of a rotating shaft 33 described later.

As shown in FIG. 1, the plate-like rail 2 is made of a material which can be forcibly deformed. Specifically, for example, as shown in FIG. 5, it is used by being forcibly curved as shown in FIG. 5 according to the bone shape of the two plate-like rails to be attached from the straight state shown in FIG.

The material for forming the plate-like rail 2 is stainless steel (specifically, SUS30 of JIS G4304).
4, SUS316, etc.), pure titanium (specifically, JI
SH4670), titanium alloy (specifically, JIS4
657 Ti-6Al-4V, ASTM F-136
Ti-6Al-4V ELI) or the like is used. It is necessary that the material of the plate-like rail 2 be capable of holding the shape after the deformation further in order to facilitate the deformation to some extent, and for this, the thickness is 0.2 to 2 m.
m, width is about 1-20 mm, preferably 1-15
mm, particularly preferably about 5 to 12 mm. Further, those having a length of about 10 to 500 mm, particularly about 50 to 200 mm are suitable.

The rack 2 formed on the plate-like rail 2
The pitch of 1 is preferably about 0.2 to 2 mm, and the height of the ribs forming the rack 21 is 0.2 to 2 m.
m is preferable, and the axial length of the ribs forming the rack 21 is about 0.1 to 1 mm, and the axial length of the grooves formed between the ribs is about 0.1 to 1 mm. Is
About 0.1 to 1 mm is preferable. The rack 21
May not be formed near both ends of the plate-like rail 2. The rack 21 is preferably formed over the entire width of the upper surface of the plate-like rail 2 (the thickness of the plate-like rail 2), but is formed partially (for example, only at the center of the upper surface of the plate-like rail 2). May be. Further, the rack 21 may be provided on the lower surface of the plate-like rail 2 instead of the upper surface. In this case, only the plate-shaped rail of the bone extension device 1 and the moving block 3 are rotated by 180 degrees. In addition, plate-like rail 2
At both ends (the front end and the rear end), holes for fixing with a bone fixing member described later are provided.

As shown in FIGS. 1 to 4, bone fixing members 4 and 5 are fixed to both ends (a front end and a rear end) of the plate-like rail 2. The bone fixation member 4 includes a plurality of bone fixation screw holes formed on the upper and lower portions.
It is located between the two flat plate portions 41, 42 and the two flat plate portions 41, 42, protrudes forward, and has a storage groove for storing the end of the plate-like rail 2 on the surface and a screw hole formed in the center thereof. And two plate portions 4
The bottom surfaces of the rails 1 and 42 and the plate-like rail holding portion 43 are continuous flat surfaces. The bone fixing member 4 is fixed to an end of the plate-like rail 2 by a fixing screw 44 screwed into a screw groove of the plate-like rail holding portion 43.

Similarly, the bone fixing member 5 is located between the two flat plate portions 51, 52 having a plurality of screw holes for bone fixing formed in the upper and lower portions, and between the two flat plate portions 51, 52, A plate-like rail holding portion 53 that projects forward and has a groove for storing the end of the plate-like rail 2 on the surface and a screw hole formed in the center of the groove is provided.
The bottom surfaces of the rails 1 and 52 and the plate-like rail holding portion 53 are continuous flat surfaces. The bone fixing member 5 is fixed to the end of the plate-like rail 2 by a fixing screw 54 screwed into a screw groove of the plate-like rail holding portion 53. And
In order to facilitate attachment of the bone extension device under the skin, it is preferable that the thickness of the plate-like rail holding portions 43 and 53 be 5 mm or less.

Since the bone fixing members 4 and 5 come into contact with bone, they are formed of stainless steel (specifically, J
SUS304 and SUS316 of ISG4304),
Pure titanium (specifically, JIS 4670), titanium alloy (specifically, Ti-6Al-4 of JIS 4657)
V, ASTM F-136 Ti-6Al-4V EL
It is preferable to use one having excellent biocompatibility such as I).

As shown in FIGS. 1 to 5, a moving block 3 is provided between both ends of the plate-like rail 2 so as to be movable in the axial direction and fixed to the bone. The moving block 3 has a structure as shown in FIGS. The moving block 3 is provided with a rotatable shaft 33 provided with a worm gear 34 that meshes with the rack 21 of the plate-shaped rail 2 so as to be rotatable from the outside. Or move to the rear end side. The moving block 3 is in contact with the insertion openings of the plate-like rails 2 formed on both side surfaces, the plate-like rail passages communicating with both the insertion openings, and the side surfaces of the plate-like rails 2 provided in the plate-like rail passages. Bearing mechanism. In addition, the moving block 3 has a number of holes for mounting fixing screws.

More specifically, the moving block 3 includes:
The housing includes a moving block housing 31, a bearing case 32 housed in the moving block housing 31, and a rotating shaft 33 in which a worm gear 34 is housed above the bearing case 32.

As shown in FIGS. 1, 2, and 6, the movable block housing 31 includes a flat plate portion 31a having a bone fixing screw hole 32c at an upper portion and a lower portion, and a bearing storage portion 31b having an open side surface. . As shown in FIG. 7, the bearing case 32 has a notch 32a for storing the worm gear portion of the rotary shaft 33 formed so as to face the upper side and a plate-like rail insertion opening 32b formed so as to face the lower side. Prepare. Inside the bearing case 32, four needle rollers 35a, 35
b, 35c and 35d are stored. Bearing case 32 and four needle rollers 35a, 35b, 35
A bearing mechanism is constituted by c and 35d.

The first set of needle rollers consisting of the two needle rollers 35a and 35b is spaced apart by a predetermined distance and is substantially parallel to the side surface of the plate-like rail 2 (in other words, substantially the plate-like rail insertion opening 32b). They are provided so as to be parallel. The second set of the needle rollers 35c and 35d is provided substantially in parallel with a predetermined distance, and is provided in parallel with the first set of the needle rollers. Therefore, the plate-like rail 2 passes through one plate-like rail insertion opening 32b, between the needle rollers 35a and 35b, further between the needle rollers 35c and 35d, and through the other plate-like rail insertion opening.

The needle roller has a small diameter at the upper portion from the center to form a worm gear storage space. Each needle roller has a bearing case 32
Are rotatably supported at the inner corners of the four folded portions at the upper end of the. The upper end of the inner corner of the folded portion at the upper end of the bearing case 32 is cut off by a quarter circle to support the needle roller. Further, four needle roller support holes are formed vertically below each corner. Therefore, the needle roller is rotatably supported by a hole formed in the bottom surface of the bearing case 32 and the inside corner of the folded portion at the upper end of the bearing case 32. Also, between the facing needle rollers (between 35a and 35b and between 35c and 35d).
) And the plate-like rail insertion opening 32b have a width that allows passage of the curved portion of the plate-like rail 2. In other words, between the facing needle rollers (between 35a and 35b and between 35c and 35d) and the plate-like rail insertion port 3
2b is 0.05 to 0.5 mm from the thickness of the plate-like rail 2
It is getting bigger. Thereby, even if the plate-like rail 2 is curved, it does not hinder the movement of the moving block 3.

The bearing mechanism is not limited to the one using the needle roller as described above, but may be one using a ball. Also in this case, it is preferable to use two pairs (a total of eight) of two opposing pairs (a total of four) of balls. Then, in order to facilitate the mounting of the bone extension device under the skin, it is preferable that the thickness of the moving block 3 (the thickness of the moving block housing 31) be 10 mm or less.

Since the moving block housing 31 comes into contact with the bone, the forming material is made of stainless steel (specifically, SUS304 or SUS316 of JISG4304), pure titanium (specifically, JISH4670), titanium alloy ( Specifically, JIS 4657 Ti-6A
1-4V, ASTM F-136 Ti-6Al-4V
It is preferable to use one having excellent biocompatibility such as ELI).

As shown in FIGS. 7 and 8, the rotary shaft 33 has a wrench connection part 36, a worm gear 34 and a flange 37. The worm gear 34 has a spiral rib 34 a having the same pitch as the pitch of the rack 21 of the plate-shaped rail 2 for meshing with the rack 21 of the plate-shaped rail 2.
Is provided. The width of the spiral rib 34a is smaller than the groove of the rack 21 of the plate-like rail 2 (the axial length of the groove of the plate-like rail 2). Therefore, even if the plate-like rail 2 is curved, the worm gear 34 meshes with the rack 21 of the plate-like rail 2 and the rotating shaft 3 with respect to the plate-like rail 2.
3 (moving block 3) can be moved.

The rotating shaft 33 is, as shown in FIG.
The wrench connection portion 36 and the flange, which are the enlarged diameter portion, are located outside the bearing case 32, and the worm gear 34
Are arranged so as to be surrounded by the four needle rollers. In this state, the worm gear 34 of the rotary shaft 33 meshes with the rack 21 of the plate-like rail 2 as shown in FIG.

The wrench 6 is detachably attached to the wrench connection portion 36 of the rotating shaft 33. In addition,
The wrench 6 may not be removable. Wrench connection 3
As shown in FIGS. 9 and 10, the inside of 6 has a substantially polygonal prism shape (in this embodiment, a hexagonal prism shape) with a reduced diameter at the open end. 9 and 11 correspond to this.
As shown in FIG. 7, the tip of the wrench 6 is also a polygonal column-shaped (in this embodiment, hexagonal column-shaped) bulging portion 6a. Further, the tip end of the wrench 6 (the tip of the bulging portion 6a) is reduced in the shape of a polygonal pyramid in order to facilitate insertion of the wrench connection portion 36 into the end portion. The rear end of the bulging portion 6a is also reduced in diameter to a truncated polygonal pyramid shape. As described above, the wrench connection portion 36 and the tip of the wrench 6 are formed in a polygonal column shape, so that by rotating the connected wrench 6, the rotating shaft 33 can be rotated, and the moving block 3 can be rotated.
Can be easily moved. In addition, the diameter of the maximum diameter portion of the bulging portion 6a of the wrench 6 is slightly larger than the inner diameter of the maximum diameter portion of the wrench connection portion 36 at the reduced open end. Therefore, in a state where the wrench 6 is connected to the wrench connection portion 36, the wrench 6 does not easily come off the wrench connection portion 36 even if the wrench 6 is pulled toward the rear end. Note that the shape of the wrench and the wrench connection portion is not a hexagonal column shape, but may be any shape as long as the rotational force given to the wrench can be transmitted to the rotary shaft via the wrench connection portion. And so on.

Further, the wrench 6 and the wrench connecting portion 36
Has a clearance capable of moving the wrench 6 at least in the lateral direction of the plate-like rail 2 when both are connected. This is because both polygonal columnar portions have a certain amount of clearance, and as described above, the front end and the rear end of the bulging portion 6a of the wrench 6 are formed in a conical or truncated conical shape. Therefore, as shown in FIG. 5, even if the plate-like rail 2 is curved, the moving block 3 can be moved by rotating the main body of the wrench 6 in a state close to the bone fixing member 5. Become. That is, even if the moving block 3 is moved to the bone fixing member 4 on the distal end side, the wrench 6 rises up and does not move away from the bone fixing member on the rear end side. The wrench 6 does not compress the skin even if the wrench 6 is worn between the two. The wrench 6 is preferably operable from outside the skin, for which purpose the wrench 6 is preferably longer than the plate-like rail 2. In particular, the wrench 6 is preferably about 5 to 50 mm longer than the plate rail 2.

Since each member of the bone extension device comes into contact with skin cells and the like, it is formed of stainless steel (specifically, SUS304 or SUS316 of JIS G4304).
Etc.), pure titanium (specifically, JIS 4670),
Titanium alloy (specifically, Ti-6 of JIS H4657)
Al-4V, ASTM F-136 Ti-6Al-4
It is preferable to use a material having excellent biocompatibility such as VELI).

Next, the operation of the stretching device 1 for osteosynthesis of the present invention will be described with reference to FIGS. The patient's mandible has a defect 61 formed by partial resection performed for the treatment of a malignant tumor. First, the shape of the patient's mandible before partial resection is recorded in advance by a method such as X-ray contrast, and the plate-shaped rail 2 is curved in accordance with the shape of the mandible. Then, the two bone fixing members and the moving block 3 are attached to the three portions of the mandible, which are initially arranged, using the bone fixing screws 40. Then, at the site 62, the cortical bone is cut. This state is shown in FIG.
This is the state shown in FIG. If possible, the skin of the bone stretching instrument fixing portion is sutured so that the rear end of the wrench 6 slightly projects.

After 5 to 10 days (for example, one week) have passed since the cortical osteotomy, the bone is stretched using the bone stretching device of the present invention from the time when a thin periosteum is formed at the cortical osteotomy. Bone extension is performed by gradually expanding the cortical bone cutting part 62. Specifically, in a state where a thin periosteum is formed in the cortical bone cut portion, the moving block 3 is rotated by 0.5 to 1..
It is moved on the plate-like rail 2 to the rear end side fixing member side by a moving amount of about 5 mm / day. For the movement, the amount of movement is 2 to
It is performed about 4 times / day.

When the wrench 6 is rotated once, the moving block 3 moves on the plate rail 2 by, for example, 1 mm. If the wrench 6 is rotated by half, the 0.5 mm moving block 3 moves. I do. Twice every 12 hours / da
By performing y, the moving block 3 can be moved toward the bone fixing member 5 on the rear end side by about 1 mm.

The movement of the moving block 3 causes the cortical bone cutting section 62 to be expanded, and the callus formed in the cortical bone cutting section 62 is extended. By performing such an operation until the end face of the bone defect part comes into contact with the end face of the defect part, the defect part is restored by the grown autogenous bone as shown in FIG.
Therefore, there is no need to bury a substitute made of metal or plastic or to transplant autologous bone collected from another part of the body.

[0032]

According to the bone stretching device of the present invention, a plate-like rail having a predetermined length, a moving block movable in the axial direction of the plate-like rail and fixed to a bone, and the plate-like rail are provided. A bone extension device comprising two bone fixing members provided near both ends of the plate-like rail, wherein the plate-like rail is formed of a hard material and capable of forcibly bending and deforming in a side direction of the plate-like rail. It further comprises a rack formed on the upper surface or lower surface of the plate-shaped rail, the moving block rotatably comprises a rotating shaft provided with a worm gear meshing with the rack of the plate-shaped rail, the moving block, By rotating the rotating shaft, the plate-shaped rail can be moved to the front end side or the rear end side. In particular, since the plate-shaped rail is formed of a hard material and can be forcibly bent and deformed in the side direction of the plate-shaped rail, it is possible to attach a bone extension device to a curved portion, and further, the moving block is Since the block is moved by the rotation of the rotating shaft provided with the worm gear meshing with the rack of the plate-shaped rail, the block can be moved even if the plate-shaped rail is curved. Furthermore, since the thickness of the moving block can be small, it can be mounted under the skin.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which a bone stretching device of the present invention is slightly curved.

FIG. 2 is a front view showing a state where the bone extension device of the present invention is not bent.

FIG. 3 is a plan view showing a state where the bone extension device of the present invention is not bent.

FIG. 4 is a plan view showing a state in which a wrench has been removed from the bone extension device of the present invention.

FIG. 5 is a plan view showing a state in which the bone extension device of the present invention is slightly curved.

FIG. 6 is an enlarged perspective view of the vicinity of a moving block used in the bone extension device of the present invention.

FIG. 7 is an exploded perspective view for explaining an internal structure of a moving block used in the bone extension device of the present invention.

FIG. 8 is an explanatory diagram for explaining an engagement state between a rotary shaft and a plate-like rail used in the bone extension device of the present invention.

FIG. 9 is a sectional view of a tip portion of a wrench and a rotating shaft used in the bone extension device of the present invention.

FIG. 10 is a sectional view taken along the line AA of FIG. 9;

FIG. 11 is a sectional view taken along the line BB of FIG. 9;

FIG. 12 is an explanatory diagram for explaining the operation of the bone extension device of the present invention.

FIG. 13 is an explanatory diagram for explaining the operation of the bone extension device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bone extension apparatus 2 Plate rail 3 Moving block 4, 5 Bone fixing member 6 Wrench 33 Rotation shaft 34 Worm gear

Claims (8)

[Claims] 1. A plate-like rail having a predetermined length, a moving block movable in the axial direction of the plate-like rail and fixed to a bone, and provided near both ends of the plate-like rail. A bone stretching device comprising two bone fixing members,
The plate-shaped rail is formed of a hard material and is capable of being forcedly bent and deformed in a side direction of the plate-shaped rail, and further includes a rack formed on an upper surface or a lower surface of the plate-shaped rail, A rotatable shaft provided with a worm gear that meshes with the rack of the plate-shaped rail, and the moving block is movable to the leading end or the rear end of the plate-shaped rail by rotating the rotating shaft. A bone stretching device, characterized in that: 2. The bone stretching device according to claim 1, wherein the moving block and the bone fixing member have a plurality of holes for fixing screws. 3. The moving block includes an insertion opening for the plate-shaped rail formed on both side surfaces, a plate-shaped rail passage communicating with both insertion openings, and the plate-shaped rail provided in the plate-shaped rail passage. The bone extension device according to claim 1 or 2, further comprising a bearing mechanism that contacts or approaches the outer surface of the bone. 4. The bone extension device according to claim 1, wherein the bearing mechanism is a bearing mechanism using a needle roller. 5. A bearing device comprising: a first set of needle rollers comprising two needle rollers provided substantially parallel to each other at a predetermined distance and substantially parallel to a side surface of the plate-like rail; 5. The bone stretching device according to claim 4, further comprising a second set of needle rollers that are provided substantially in parallel and spaced apart from each other and that are provided in parallel with the first set of needle rollers. . 6. The wrench connection portion protruding from the moving block, wherein the wrench connection portion is provided with a wrench for rotating the rotation shaft. A bone stretching device according to any of the claims. 7. The bone extension device according to claim 6, wherein the wrench is detachable from the wrench connection portion of the rotary shaft. 8. The wrench and the wrench connection,
The bone stretching device according to claim 6 or 7, wherein the bone stretching device has a clearance capable of moving a wrench at least in a lateral direction of the plate-like rail when both are connected.