Bone perforation drill

Abstract

To provide a bone perforation drill capable of perforating a hole of a desired diameter with preferable quality even with respect to a bone having non-preferable bone quality.SOLUTION: Provided is a bone perforation drill 1 having an outer shape whose basic tone is a cylinder shape in a longitudinal direction in an axial direction. In the bone perforation drill 1, a cutting blade 11 is provided in a distal end 10, a release groove 21 of cutting power drug so as to form a spiral with respect to an axial center is formed on a cylinder side periphery 22, and an edge formed between the release groove 21 and the cylinder side periphery 22 is chamfered.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a drill for making a pilot hole for screws or nails during bone fixation surgery, and particularly to a drill for perforating bones with poor bone quality, such as osteoporosis patients with low bone density.

Background Art

[0002] Conventionally, when performing surgeries such as bone fixation or inserting a plate into a bone, it has been necessary to drill holes for screws or nails. At this time, for example, a slender guide pin was first driven in, and a cylindrical drill through which the guide pin was inserted was rotated with an electric drill driver to make a hole with a desired diameter and depth.

[0003] However, the conventional technology had the following problems. When perforating bones with high bone density, a hole with a predetermined diameter as specified can be made. However, even if there is a guide pin because a hand-held electric drill is used, when perforating bones with poor bone quality, such as bones with low bone density or brittle bones, due to the influence of hand tremors or the like, the hole may become larger, an irregular force may be applied and small pieces may break off, the inner circumference of the hole may become rough, and the surface properties may deteriorate, resulting in a hole that is not the desired diameter.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the above, and an object thereof is to provide a bone drilling drill capable of accurately drilling a hole with a desired diameter with good quality even for bones with poor bone quality.

Means for Solving the Problem

[0006] The bone drilling bit according to claim 1 is a bone perforating drill that is longitudinally long in the axial direction and has a cylindrical-based outer shape. A cutting edge is provided at the tip, and on the circumferential side of the cylinder, there is formed a chip discharge groove that is dug so as to form a helix with respect to the axis center. The bone drilling bit is characterized in that the edge formed between the chip discharge groove and the circumferential side of the cylinder is chamfered.

[0007] That is, the invention according to claim 1 suppresses the diameter expansion action based on the de facto pressurized rotational contact due to the edge protrusion where the pressure per unit area increases at the site of surgery or the like where the drill driver has to be held and drilled. Thereby, it becomes possible to drill a hole with the desired diameter.

[0008] The cylindrical base can also be expressed as a round bar base, which means that it is cylindrical-like except for the groove and the tip. In terms of the outer shape, it only needs to be cylindrical-like, and it also includes being hollow, that is, cylindrical-like. The chip discharge groove is preferably set to the number corresponding to the number of blades. The pitch (in the case of a normal symmetric drill: lead / number of blades) is long. While the conventional product is generally 1.2 to 2.0 times the cylinder diameter, it is set to 2.5 times to 3.5 times. Thereby, the number of edge contacts per unit rotation can be reduced, and the opportunity of pressurized contact can be decreased. The edge can also be expressed as a ridge or a protrusion. Note that the edge exists on the front side and the rear side with respect to one blade (leading edge and heel), and it is preferable to chamfer both. In particular, it is more preferable to chamfer the leading edge larger than the heel. The chamfer is preferably a round surface or an R surface, but it may be a chamfered surface or the like as long as the protruding part does not hit the bone and is not worn away, that is, does not expand the diameter of the hole, during rotation.

[0009] The bone drilling bit according to claim 2 is the bone drilling bit according to claim 1, characterized in that the cutting edge portion at the tip including the cutting edge is formed with a diameter larger than the cylinder diameter.

[0010] That is, the invention according to claim 2 suppresses the diameter expansion effect based on the pressing contact around the drill side caused by hand tremors at the site of an operation or the like where the drill driver has to be held and drilled. As a result, it becomes possible to drill a hole with a targeted diameter.

[0011] In the cutting edge part, only the cutting edge protrudes outward, and in addition to the mode where the diameter of the circle drawn by the outer end of the blade is larger than the cylinder diameter, the blade is formed on the end face perpendicular to the axial direction, and the circumferential surface of the cutting edge part (the cylindrical part constituting the cutting edge part) is also included in the mode where it is larger than the cylinder diameter by a predetermined axial length.

[0012] The bone drilling drill according to claim 3 is the bone drilling drill according to claim 1 or 2, wherein the cutting edge is formed in a substantially straight line extending radially outward in a rotationally symmetric manner with respect to the axis center when viewed in the axial direction, and the line connecting the outer end and the inner end of the blade is inclined as a coordination in which the outer end precedes during the hole drilling rotation with respect to the radial direction.

[0013] That is, in the invention according to claim 3, since the bone is cut so as to be taken in inward, the chips are not pushed outward to expand the hole.

[0014] The substantially straight line is in a broad sense, and it suffices that a blade that can be regarded as a straight line partially is formed, and the mode of drawing an arc is also included. Further, it suffices that a substantially straight line can be recognized in a plan view, and a blade inclined in the axial direction is of course included.

[0015] The inventions of claims 1 to 3 can be particularly preferably applied to osteoporosis patients, and thus the present invention may also be referred to as an osteoporosis bone drilling drill.

Effects of the Invention

[0016] According to the present invention, even for bones with poor bone quality, it is possible to drill a hole with a targeted diameter and good inner circumferential surface properties without becoming a useless hole. As a result, it becomes possible to fully exhibit the fixing force of screws and nails.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, a bone drilling drill formed in 180° rotational symmetry with a two-flute configuration will be described. Hereinafter, the bone drilling drill will be simply referred to as a drill as appropriate. FIG. 1 is a front view and a side view of the drill of the present invention. FIG. 2 is a perspective view of the drill of the present invention. For convenience of explanation, the scale of the figures is changed as appropriate.

[0019] The drill 1 is composed of a cutting edge portion 10 and a shank portion 20, both of which are based on a cylinder, and in particular, the shank portion 20 is formed longitudinally. The central hole 30 is for a pin, and the drill 1 is inserted into a guide pin (diameter 1.3 mm) that has been previously driven into the bone and rotated along with it to drill the bone.

[0020] On the cutting edge portion 10, two cutting edges 11 provided in 180° rotational symmetry are formed on the end face, that is, the plane perpendicular to the central axis of the cylinder. The front and rear of the rotation of the cutting edge 11 are cut off in the axial direction (cutoffs 12f and 12b are formed), and the cutoff 12f of one cutting edge 11 and the cutoff 12b of the other cutting edge 11 extend along an inclined surface 13 that is inclined with respect to the axis, and the cutoff 12f of the other cutting edge 11 and the cutoff 12b of one cutting edge also extend along another inclined surface 13 that is inclined with respect to the axis in the same manner (the two inclined surfaces 13, the two cutoffs 12f, 12b are also formed in 180° rotational symmetry with respect to the axis). Further, the inclined surfaces 13 are respectively connected to the relief grooves described later.

[0021] The blade 11 is formed in a straight line, and this straight line direction is inclined by 15° obliquely with respect to the radial direction so that the outer end precedes the inner end during rotation (clockwise since it is a right-handed thread) during cutting. As a result, the cutting powder moves toward the axial center side while following the cut-off portion 12f and is discharged from the relief groove through the inclined surface 13. In other words, when the direction of the blade is radial or inclined such that the inner end precedes the outer end, the cutting powder is pushed outside the hole and compresses the bone, which may cause particularly fine chipping or diameter expansion in the case of osteoporosis patients. However, such a situation does not occur, and it is possible to drill a hole with a good shape and the desired diameter.

[0022] The diameter of the cutting edge portion 10 can be appropriately designed. For example, it can be 3.7 mm in diameter and 1.2 mm in depth (axial length).

[0023] On the handle portion 20, a relief groove 21 connected to the inclined surface 13 is formed in a spiral shape on the surface of the cylinder. Also, this relief groove is formed symmetrically with respect to 180° rotation about the axis. Here, the diameter of the handle portion 20 is made shorter than the diameter of the cutting edge portion 10. When the diameter of the cutting edge portion 10 is 3.7 mm, for example, the diameter of the handle portion 20 is made 3.4 mm. This is because when rotating the drill 1 along the guide pin to drill through the bone, during the operation, the electric drill driver must always be held by hand, so even the slightest hand tremor will occur. As a result, the peripheral surface of the drill side hits against the peripheral surface of the already drilled hole, which becomes a factor in diameter expansion. In the drill 1, in order to suppress this hitting, the handle portion 20 is formed with a reduced diameter compared to the cutting edge portion 10 (the cutting edge portion 10 is configured to have a larger diameter than the handle portion 20). Furthermore, regarding the relief groove 21, the edge formed between it and the side peripheral surface 22 is chamfered to a rounded surface. If it is not chamfered, during the above-mentioned hand tremor, the edge may act as an actual blade and cause the diameter of the cutting hole to expand by gouging the bone. Even if it does not gouge, the edge becomes an actual protrusion and increases the pressure per unit area, strongly hitting against the peripheral surface of the already drilled hole, which also becomes a factor in diameter expansion. In the drill 1, this is prevented by chamfering.

[0024] Also, the pitch of the relief groove 21 is set to 3.0 times the diameter, increasing the axial feed of the relief groove 21 per unit rotation. This also reduces the number of edge contacts compared to the case of a short pitch, preventing the occurrence of diameter expansion.

[0025] <Comparative Experiment> A drilling comparison was conducted between the drill of the present invention (blade tip diameter 3.7 mm, shank diameter 3.4 mm, two blades, blade inclination 15°, pitch 30 mm, made of stainless steel) and a comparative drill (manufactured by Teijin Medical Technology Co., Ltd., product number D35C4AL: diameter 3.5 mm, three blades, blade inclination 0°, pitch 30 mm, made of stainless steel). As simulated bones, healthy cortical bone blocks (product number SAW) and healthy cancellous bone blocks (product number SAW1522 - 03) and osteoporotic cancellous bone blocks (product number SAW1522 - 01) manufactured by SAWBONE were used. The drilling depth was set to 10 mm for the cortical bone model and 25 mm for the cancellous bone model, and manual drilling was performed with the drill rotation speed set to 1900 rpm and n = 10.

[0026] The evaluation points were set at positions 2 mm, 5 mm, 10 mm from the surface, and for the cancellous bone block, further at 15 mm and 20 mm depths. The hole diameters were measured at each position and averaged, and the evaluation was performed based on the ratio to the drill diameter. The results are shown in Figure 3. The diameter expansion ratio, that is, the drill hole expansion rate, exceeds 1 for all conventional products (conventional drills) and expands by about 5% to 10%. Therefore, when drilling with conventional products, there is a concern about the screw engagement stability afterwards. On the other hand, for the inventive product (new drill), the expansion ratio is slightly less than 1, resulting in substantially accurate drilling. Especially regarding the osteoporotic cancellous bone block, the difference between the conventional product and the inventive product is significant, and it can be said that the present application is particularly excellent in drilling for osteoporosis.

[0027] As described above, by using the drill 1 of the present invention, it is possible to drill a hole with the intended diameter and good inner peripheral surface properties without creating a sloppy hole even in bones with poor bone quality. Thereby, it becomes possible to fully exert the fixing force of screws and nails.

[0028] Note that the present invention is not limited to the above examples. For example, it can also be configured with three blades or four blades. The inclination of the blade with respect to the diameter is not limited to 15° and can also be set to 10° to 30°. Further, instead of forming the blade on the end face, it can also be made into a shape in which the inner end protrudes, a protruding shape in which the outer end protrudes, or a concave shape.

Industrial Applicability

[0029] The present invention can be suitably used for perforating the bones of osteoporosis patients.

Explanation of Reference Numerals

[0030] 1 Drill 10 Cutting Edge Portion 11 Blade 12 Cutting-off (12a: Front Cutting-off, 12b: Rear Cutting-off) 13 Inclined Plane 20 Handle Portion 21 Relief Groove 22 Side Peripheral Surface 30 Hole

Claims

1. A bone perforating drill that is axially long and has a cylindrical-based outer shape, with a cutting edge provided at the tip, and on the cylindrical side circumference, there is formed a chip evacuation groove that is dug so as to form a helix with respect to the axis center, and the edge formed between the chip evacuation groove and the cylindrical side circumference is chamfered. A bone drilling drill characterized by this.

2. The bone drilling drill according to claim 1, characterized in that the cutting edge portion of the tip including the cutting edge is formed with a diameter larger than the cylindrical diameter.

3. The cutting edge, when viewed in the axial direction, is formed in a substantially straight line radially outward with rotational symmetry with respect to the axis center, and the line connecting the outer end and the inner end of the blade is inclined as a coordination in which the outer end leads during the drilling rotation with respect to the radial direction. The bone drilling drill according to claim 1 or 2, characterized by this.

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