JPH10211213A - Screw for bone joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To arbitrarily inject bone cement and fully function as a screw without losing its fixed strength by forming a lot of through holes, whose inner end communicates with a hollow hole and outer end is opened to the outside, around the circumferential wall of the screw main body in such a state as being dispersed in the axial and circumferential directions of the screw main body. SOLUTION: A screw main body 1 is provided with a screw part 2 in its tip side, a non-screw part 3 in the base end side, and a head part 4, where the tip of a hexagonal wrench or a screw driver is inserted and engaged, in the other end. A hollow hole 5 penetrating the screw main body in the axial direction (long shaft direction) is formed in the screw main body 1 so that a guide pin can be inserted in the hollow hole 5. The tip of the screw main body 1 is notched into a recessed shape so as to facilitate its insertion into the bone and a plurality of through holes 6 whose inner end communicates with the hollow hole 5 and outer end is opened to outside are formed in an a valley part 2a of the screw part 2 in the circumferential wall of the screw main body 1 in such a state as being dispersed in the axial and circumferential directions of the screw main body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an osteosynthesis screw, and more particularly to an osteosynthesis screw suitable for use in performing a bone augmentation method in surgery or the like for a femoral neck fracture with osteoporosis.

[0002]

2. Description of the Related Art Conventionally, osteosynthesis screws called cannulated screws are often used in surgery for femoral neck fractures accompanied by osteoporosis. This is a rod-shaped screw body in which a screw portion is formed from one end side on the outer peripheral surface, and a hollow hole called a guide hole that penetrates the screw body in the axial direction is formed. The guide hole is inserted through the pin, and the screw body is rotated clockwise by a wrench or a screwdriver to insert the screw body, thereby compressing and fixing the fractured portion formed in the bone head and diaphysis.

However, in the case of severe osteoporosis patients,
When the bone quality of the femoral head was weakened, mechanical fixation with a cannulated screw alone was insufficient in fixation strength. For this reason, some reinforcement surgery methods are required, and as one of them, a filling reinforcement method using bioactive bone cement such as calcium phosphate cement has recently attracted attention. Conventional bone cements were difficult to use in terms of heat generation during polymerization, the effect of unpolymerized monomers on the circulatory system, and biocompatibility.However, calcium phosphate cement has no problems of heat buildup and biotoxicity. Since it has excellent osteophilicity, it does not have such a problem, and it can be injected into a bone having a rough trabecular bone to strengthen weakened bone and enhance pull-out strength.

[0004]

However, when the filling reinforcement method using bone cement is used, even if calcium phosphate cement is used as the bone cement, the conventional cannulated screw originally has the structure of the bone cement. Since it was not produced for the purpose of combined use, a two-stage operation was necessary in which bone cement was injected by a separate means and then fixed by a cannulated screw.

The present invention has been made in view of the above circumstances, and it is possible to arbitrarily inject bone cement, and furthermore, an osteosynthesis functioning sufficiently as a screw without impairing the fixing strength of a conventional osteosynthesis screw. It is intended to provide a screw for use.

[0006]

According to the present invention, there is provided a rod-shaped screw main body having a screw portion formed on one end side on an outer peripheral surface, and a hollow hole passing through the screw main body in an axial direction is formed. In the osteosynthesis screw which is inserted into the bone from the screw portion side and screwed into the bone, the inner end communicates with the peripheral wall of the screw main body (the wall portion facing the radial direction of the screw main body) through the hollow hole. A plurality of through-holes whose ends are open to the outside are formed discretely in the axial direction and circumferential direction of the screw main body.

In the above, the plurality of through holes are preferably formed such that the number of through holes and / or the area of the opening of the through hole increases as approaching the one end of the screw body. Each have a substantially circular cross section,
It may have a slit-shaped cross section, a substantially oval cross section, or a combination of these various shapes. Further, the through hole may be formed over the ridge and the valley of the screw portion, and in the case of the fine hole, it may be formed only at the valley of the screw portion.

The osteosynthesis screw of the present invention can be used in the same manner as a conventional cannulated screw. However, in the case of severe osteoporosis patients, the bone quality of the patient's femoral head is weakened. If it is, fix it to the patient's femoral head in the same way as a conventional cannulated screw, then apply bone cement, especially bioactive bone cement such as calcium phosphate cement, to the hollow hole that also serves as the guide hole of the guide pin. inject. The injected bone cement penetrates between the trabeculae of the roughened bone from the hollow hole through the through hole in the peripheral wall. As a result, the bone itself is strengthened and the pull-out strength is increased. In addition, in the screw for osteosynthesis of the present invention, since bone cement or bone tissue enters into the through-hole formed in the peripheral wall, rotation of the screw after fixation can also be prevented. This effect of preventing rotation is also exhibited when bone cement is injected in advance into the portion where the screw is fixed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the screw for osteosynthesis according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a side view showing the entire osteosynthesis screw. In the figure, reference numeral 1 denotes a screw main body. The screw main body 1 is formed of a titanium alloy, which is a material having biocompatibility, strength, rigidity, and the like. The screw main body 1 includes a screw portion 2 at a distal end (one end) side, and a non-screw portion 3 at a base end (other end) side. The other end is provided with a head 4 into which a hexagon wrench or the tip of a screw driver is inserted and engaged. Here, various lengths and diameters of the screw main body 1, lengths of the screw portions or non-screw portions, screw thread diameters, and the like are prepared so as to be adaptable to any patient. The screw main body 1 is formed with a hollow hole 5 penetrating the screw main body 1 in the axial direction (long axis direction), and a guide pin described later can be inserted into the hollow hole 5. The tip of the screw main body 1 is notched in a concave shape so that insertion into bone is facilitated.

The above structure is basically the same as that of the conventional cannulated screw. However, in the osteosynthesis screw according to the present invention, as shown in an enlarged view in FIG. A plurality of through-holes 6 whose inner ends communicate with the hollow holes 5 and whose outer ends are open to the outside are formed in the valleys 2a of the screw portion 2 on the peripheral wall of the screw portion 2 in the axial direction and the circumferential direction of the screw main body 1. It is formed in a state. When the bone cement is injected into the hollow hole 5 which also serves as an insertion hole for the guide pin, the bone cement is discharged laterally from the peripheral wall through the plurality of through holes 6.

Here, in the example shown in FIGS. 1 and 2, the through holes 6 are all of a substantially circular cross section having the same diameter, and are provided at equal intervals in the spiral valleys 2a of the screw portion 2. I have. But,
The shape and arrangement of the through holes 6 are not limited to this example.
Various modifications are possible.

FIG. 3 shows one of such modifications, in which the valley portion 2a of the screw portion 2 is spaced apart at the same distance from the valley portion 2a and has an elongated oval shape extending in the extending direction of the valley portion 2a. A hole 6a is provided. The elliptical through-hole 6a is an ellipse whose major axis is considerably long at a position close to the tip of the screw body 1,
The major axis of the ellipse is gradually reduced toward the base end of the screw body 1, and is substantially circular near the end of the screw portion 2. In such a structure, the opening area of the through-hole increases toward the distal end side of the screw main body 1, and more bone cement is released from the peripheral wall near the distal end of the screw main body 1.

FIG. 4 shows another modification. In this example, the through hole 6b is formed not only in the valley 2a but also in the ridge 2b of the screw 2.
The screw body 1 is disposed at equal intervals in the circumferential direction and the axial direction of the screw main body 1, but has a slit shape extending in the axial direction of the screw main body 1 at the distal end side of the screw main body 1. The shape is shortened toward the end. Also in this example, the opening area becomes larger toward the distal end side of the screw main body 1, and more bone cement is released from the peripheral wall on the distal end side of the screw main body 1.

The shape, size, number and arrangement of the plurality of through holes can be variously modified in addition to the above. In particular, it should not be formed only on the screw portion 2, but may be formed on any part of the peripheral wall of the screw main body 1 as long as it is a part to be inserted into the bone, and may be formed on the non-screw portion 3. . Further, the holes can be formed by changing the discrete positions of the through holes depending on the indication case.

When performing an osteosynthesis operation using the osteosynthesis screw having the above configuration, first, the osteosynthesis screw is inserted into the bone in the same manner as a conventional cannulated screw. That is, as shown in FIG. 5, the angle at which the osteosynthesis screw is inserted by the angle guide 7 is determined, and the guide pin 8
Is inserted into the head from outside the diaphysis. Next, as shown in FIG. 6, the length of the intraosseous insertion portion of the guide pin 8 is measured using the guide pin depth gauge 9, and the length of the osteosynthesis screw to be used is determined. Then, as shown in FIG. 7, by inserting the guide pin 8 into the hollow hole 5 of the osteosynthesis screw, the distal end of the osteosynthesis screw is inserted until it reaches the diaphysis.
Next, as shown in FIG. 8, a bone screw is screwed in with a hexagon wrench or a screwdriver or the like to compress and fix the fracture generated in the bone head and diaphysis, and then the guide pin 8 is removed. FIG. 9 shows a state in which the attachment of the two osteosynthesis screws has been completed. When the head 4 of the screw body 1 may be buried in the bone, a washer (not shown) is interposed in front of the head 4.

Next, a bone cement, particularly a bioactive bone cement such as calcium phosphate cement, is injected into the hollow hole 5 from the base end side of each osteosynthesis screw. The bone cement injected into the hollow hole 5 has a plurality of through holes 6, 6a, 6
b and is extruded into the roughened bone. In this way, the bone itself is strengthened and the pull-out strength of the osteosynthesis screw is increased. In addition, since bone cement or bone tissue enters the through holes 6, 6a, 6b, reverse rotation (return) of the screw can be reliably prevented.

In the osteosynthesis screw having the above configuration, bone cement can be injected from the hollow hole 5 through the through holes 6, 6a and 6b in the peripheral wall into the femoral neck where the trabecular bone is roughened. Therefore, the bone cement injection procedure can be easily performed simultaneously with the fracture fixing operation. Also, the through holes 6, 6
Since a and 6b are discretely formed in the axial direction and the circumferential direction of the screw main body 1, it becomes possible to flow the bone cement evenly and accurately into a necessary portion in the bone.

The method of using the osteosynthesis screw according to the present invention is not limited to the above-mentioned method, and the type of bone cement to be injected, the case to be applied, the use, and the like are arbitrary. It can also be used simply as a replacement for a conventional cannulated screw.

[0020]

According to the screw for osteosynthesis of the present invention, a bone cement, particularly a bioactive bone cement such as calcium phosphate cement is injected into a bone through a hollow hole and a through hole after being fixed to a patient's femoral head or the like. Therefore, the trabecular bone itself can be strengthened and the pull-out strength can be increased. Further, since the through holes are formed discretely in the axial direction and the circumferential direction of the screw main body, there is an effect that the bone cement can be uniformly and accurately poured into a necessary portion in the bone.

[Brief description of the drawings]

FIG. 1 is a partially broken side view showing the entire osteosynthesis screw according to the present invention.

FIG. 2 is an enlarged view of a main part of the osteosynthesis screw of FIG. 1;

FIG. 3 is a view similar to FIG. 2, showing a modification of the present invention.

FIG. 4 is a view similar to FIG. 2, but showing another modification of the present invention.

FIG. 5 is a schematic view showing a process of using the osteosynthesis screw according to the present invention, in which a guide pin is inserted.

FIG. 6 is a view similar to FIG. 5, showing a state in which the insertion length of the guide pin is measured.

FIG. 7 is a view similar to FIG. 5, showing a state in which a bone screw is inserted into a guide pin.

FIG. 8 is a view similar to FIG. 5, but showing a state in which a bone screw is screwed.

FIG. 9 is a view similar to FIG. 5, but showing a state in which a bone screw is screwed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw main body 2 Screw part 3 Non-screw part 5 Hollow hole 6, 6a, 6b Through-hole

Claims (5)

[Claims] 1. A rod-shaped screw main body having a screw portion formed on one end side on an outer peripheral surface, a hollow hole passing through the screw main body in an axial direction is formed, and inserted into bone from the screw portion side. In the osteosynthesis screw to be screwed into a bone, a plurality of through holes having an inner end communicating with the hollow hole and an outer end open to the outside are formed in a peripheral wall of the screw main body in an axial direction and a circumferential direction of the screw main body. An osteosynthesis screw which is formed discretely in a direction. 2. The plurality of through holes are formed such that the number of through holes and / or the opening area of the through holes increases as approaching the one end of the screw body. Item 7. An osteosynthesis screw according to Item 1. 3. The osteosynthesis screw according to claim 1, wherein the through-hole has a substantially circular cross section. 4. The osteosynthesis screw according to claim 1, wherein the through hole has a slit-shaped cross section. 5. The osteosynthesis screw according to claim 1, wherein the through hole has a substantially oval cross section.