JP2005245520A - Bone fixation device, assembly method and operating tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bone fixation device for not only increasing the support force of a bone screw and preventing movement but also facilitating assembly and preventing the detachment of a cap. <P>SOLUTION: The bone fixation device comprises the bone screw 50 having a head 54, the cap 56 for supporting the upper side of the head, a receiver member 58 having a bore 70 to which the head of the bone screw is locked and having a U-shaped channel where a support bar is housed, and a bar fixing nut 60 for fixing the support bar. The bore is composed of a multiple step part 74 formed on a lower inner surface so as to be in linear contact with the upper outer surface of the head and increase the support force of the head, a cap housing part formed on the upper side of the multiple step part so as to house the cap, and a screw part formed into an inner diameter smaller than the inner diameter of the cap housing part, to which the bar fixing nut is screw-connected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a bone anchoring device for fixing a bone such as a spine without being moved after calibration to a normal state.

  Conventional bone fixation devices for fixing bones such as the spine include Korean Patent Publication No. 2000-48562 (Patent Document 1) and US Patent No. 6280442 (Patent Document 2).

  The above-mentioned Patent Document 1 includes a bone screw 10 having a spherical head 12 as shown in FIG. 1, a contraction collet 14 that supports the head 12 of the bone screw, and a tapered recess 16 that accommodates the contraction collet 14. A receiver member 18 having a central bore to be defined and having a U-shaped channel that communicates with the recess 16 and accommodates the support bar (R) therein, and is screwed to the receiver member 18 to attach the support bar (R). A set screw 20 to be fixed.

  A tool receiving recess 22 for receiving a tool is formed in the head 12 of the bone screw. The tool receiving recess 22 is limited to a flatly cut upper surface 24, and a set screw 20 is screwed to a channel portion of the receiver member 18. Thus, an internal screw 26 is formed, and a recess 28 is formed on the back surface of the contraction collet 14 to which the head 12 is in close contact. A plurality of slots are formed in the lower portion of the contraction collet 14 and the recess 28 to provide a constant compressive force to the bone screw head 12.

  When the set screw 20 is tightened, the support bar (R) compresses the contraction collet 14, and the contraction collet 14 presses the bone screw 10 vertically or at a predetermined angle while being pressed against the tapered recess 16 of the receiver member. Come to fix.

  In Patent Document 2, as shown in FIG. 2, a plurality of protruding bands 34 are formed on the head 32 of the bone screw 30, a support ring 38 is fitted to the lower inner surface of the bore of the receiver member 36, and the lower side of the head 32 is The cap 40 is put on the upper side of the head 32, and the support bar (R) is inserted into the channel of the receiver member 36 on the upper side of the cap 40 and fixed with the bar fixing nut 42. .

  Then, the inner diameter of the portion where the cap 40 is inserted in the receiver member 36 is formed larger than the inner diameter of the portion where the bar fixing nut 42 is screwed, and when the support bar R is separated by loosening the bar fixing nut 42, The cap 40 is prevented from detaching to the upper side. At the time of assembling, the cap 40 is inserted through the lower side of the receiver member 36, and then the head 32 of the bone screw 30 is inserted into the lower side of the receiver member 36 and then supported. The ring 38 is extrapolated from the lower end of the bone screw 30 and fitted to the lower inner surface of the bore of the receiver member 36.

On the other hand, a structure is also disclosed in which a female screw is formed inside the receiver member to the lower side so that the cap 40 is not detached by screwing.
Korean Patent Publication No. 2000-48562 US Pat. No. 6,280,442

  However, the conventional bone anchoring device as disclosed in Patent Document 1 cannot be maintained in the initial support state because the support force is weak and the head 12 that rests on the tapered recess 16 moves due to external disturbance.

  Although Patent Document 2 is an improvement of the problem of Patent Document 1, it is not only easy to fit and assemble the support ring 38 but also has a problem that it does not deserve the support force of the bone screw. It was.

  Furthermore, the structure in which the upper part of the bone screw head is screwed and fixed with a cap not only requires the cap to be screwed down, but also the fixing force of the bar fixing nut cannot be transmitted to the head. In addition to being not easy to assemble, there was a problem that the supporting force of the bone screw was low.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is not only to prevent the movement by increasing the supporting force of the bone screw but also to remove the cap while being easy to assemble. An object of the present invention is to provide a bone anchoring device that prevents this.

  In order to achieve the above object, a bone fixation device according to the present invention includes a bone screw having a head, a cap for supporting an upper side of the head of the bone screw, and at the same time the cap is accommodated. A receiver member having a U-shaped channel in which a head is locked and a support bar is accommodated; and a bar fixing nut that is screwed to the receiver member to fix the support bar. The bore is formed on the upper surface of the multiple step portion so as to be in line contact with the upper outer surface of the head so as to increase the support force of the head and on the inner surface of the lower portion so as to accommodate the cap. A cap housing portion, and a screw portion formed with an inner diameter smaller than the inner diameter of the cap housing portion to which the bar fixing nut is screwed. The threaded inner diameter greater than the outer flange formed of through is formed of said cap is characterized in that the flange is inserted into the cap receiving portion plastically deformed with the lower end of the threaded portion.

  A plurality of groove bands are formed at predetermined intervals on the outer surface of the bone screw so as to increase the frictional force with the cap, but the groove band crosses the lower end contact line of the cap regardless of the fixing angle of the bone screw. It is formed asymmetrically with respect to the axis of the bone screw. The depth of the groove band is preferably 0.01 to 0.03 mm.

  The receiver member has a bowl shape in which the diameter of the central portion through which the support bar passes is larger than the upper and lower diameters.

  When the cap is assembled, the cap is tilted so that one side of the flange is first accommodated in the cap accommodating portion and the other side of the flange is locked to the screw portion. The flange portion locked to the cap portion is inserted into the cap housing portion while causing plastic deformation together with the lower end portion of the screw portion.

  The tool used when performing the operation with the bone anchoring device includes a tip protruding portion inserted into the wrench insertion port of the bone screw and a screw portion screwed to the screw portion of the receiver member, and the bone screw and the receiver of the bone anchoring device. An alignment rod for aligning the members, and a handle coupled to the alignment rod to rotate the alignment rod.

  In order to increase the tightening force and relaxation force of the bone screw to facilitate the retraction of the receiver member, the alignment rod has a flange inserted and locked into the channel of the receiver member on the outside of the alignment rod. The outer pipe is slidable in the direction. It is preferable that a handle is formed at the end of the outer pipe so that the outer pipe can be easily moved.

  According to the bone anchoring device of the present invention, not only does the bone screw have a high supporting force to prevent movement, but also the assembly is easy, the force transmission force is large, the loosening is prevented, and the cap is prevented from being detached. is there.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  3 and 4, the bone anchoring device according to the embodiment of the present invention includes a bone screw 50 having a spiral portion 52 and a head 54, and a cap 56 supports the upper side of the head 54 of the bone screw. In this structure, the head 54, the cap 56, and the support bar (R) are accommodated and fixed. A support bar R is fixed to the upper side of the receiver member 58, but a fixing nut 60 is screwed.

  The spiral portion 52 of the bone screw 50 is a portion that is driven into the bone, and the lower end thereof is pointed so as to be easily inserted into the bone, and the diameter of the valley becomes smaller toward the lower side. Have the same diameter. If the screw thread has the same external meridian and the same thread height, the fixing force is weakened by external force, etc., and there is a problem that the bone screw rattles. In order to do this, the outer diameter becomes smaller toward the end of the spiral part, such a structure has a problem that the rigidity is lowered and the bone screw is damaged, and the diameter of the trough is reduced as in this embodiment. On the other hand, the structure becomes smaller as it goes down, but the structure in which the diameter of the crest of the spiral portion is the same can prevent the rigidity from being lowered while the spiral portion is firmly fixed to the bone.

  The head 54 of the bone screw 50 has a spherical shape with the upper part cut flat, and a hexagonal groove 62 is formed at a predetermined depth on the flat cut surface so that a tool such as a wrench can be inserted and turned easily. The hexagonal groove can be composed of various square grooves.

  As shown in FIG. 7, a plurality of groove bands 54a are formed at predetermined intervals on the outer surface of the head 54 of the bone screw 50 so as to increase the frictional force with the cap. The groove bands 54a are fixed to the bone screw. It is formed asymmetrically (spiral, spiral, etc.) with respect to the axis of the bone screw so that the lower end contact line of the cap 56 crosses regardless of the angle. The groove band 54a is processed with a depth (d) of 0.01 to 0.03 mm and a radius (r) of about 0.2 mm. The groove band 54a is preferably formed continuously. Such a groove band 54a does not generate debris, barr, metal chip, or the like that may occur due to line contact with the cap when assembling, performing, or removing the bone anchoring device. To.

  As shown in FIG. 6, the cap 56 has a cylindrical shape with a flange 64 having an outer diameter larger than the inner diameter of a later-described receiver member threaded portion formed at the upper end, and communicates with a hexagonal groove 62 at the center. A hole 66 is formed, and a recess 68 is formed at a predetermined depth on the back surface. The recess 68 is a curved surface having a curvature radius smaller than the curvature radius of the head 54, and the lower end angle (P 3) of the curved surface is in line contact with the upper outer surface of the head 54. The recess can also be an inclined surface.

  As shown in FIG. 5, the receiver member 58 has a bore 70 formed in the longitudinal direction so that the head 54 of the bone screw is locked at the same time that the cap 56 is accommodated, and a support bar (R) passes therethrough. And a U-shaped channel 72 formed to be seated. The diameter of the central portion through which the support bar (R) passes is larger than the diameter of the upper and lower sides.

  The portion of the receiver member 58 through which the support bar (R) passes has the largest moment of inertia. In this way, the flange shape in which the diameter of the central portion of the receiver member 58 is larger than the diameter of the upper and lower sides is the strength of the receiver member 58. To prevent twisting. In most cases, the support bar is bent according to the anatomical structure of the spine during the operation. When bending the support bar, two or more fixing devices coupled to one support bar are used. Interference (or collision) may occur between them. At this time, interference mainly occurs between the bulky receiver members, but this interference is minimized when the receiver members are bowl-shaped. Furthermore, interference will also occur between the spine and the fixation device, but if the lower end of the receiver member is saddle shaped, the interference between the bone and the fixation device will also be minimal.

  A multiple stepped portion 74 composed of two steps is formed on the inner surface of the lower portion of the bore 70 so as to increase the support force of the head 54, and each protrusion angle (P1) (P2) of the multiple stepped portion is in line contact with the lower outer surface of the head 54 To do. Multiple step portions can be formed in three steps, four steps, or the like. The protrusion angle (P2) on the upper side of the multiple stepped portion 74 has a larger inner diameter than the protrusion angle (P1) on the lower side, and the lower outer surface of the spherical head 54 comes into line contact.

  The bore 70 includes a multiple stepped portion 74, a cap accommodating portion 76 formed on the upper side of the multiple stepped portion 74 so that the cap 56 is accommodated, and a screw portion 78 to which the bar fixing nut 60 is screwed.

  The inner diameter of the cap housing portion 76 is formed larger than the inner diameter of the screw portion 78. Therefore, the cap 56 is not detached after the flange 64 is plastically deformed together with the lower end portion of the screw portion 78 and inserted into the cap housing portion 76 by an assembly method described later.

  The thread portion 78 is formed so that the upper thread depth (H1) is deeper than the lower thread depth (H2) so that the bar fixing nut 60 is locked on the upper side and does not move any further. . The pitch of the upper and lower threads is the same. Accordingly, since the bar fixing nut 60 is inserted only to a depth at which the support bar (R) is tightened, the position of the bar fixing nut 60 is maintained in a state where the support bar (R) is not inserted, thereby speeding up the assembly. it can.

  The threaded portion 78 may have the same shape with the upper and lower portions formed at the same depth.

  The thread of the threaded portion 78 is formed of a trapezoidal screw so that the receiver member 58 is prevented from being deformed while being in an optimum state in terms of force transmission, fastening force, and loosening prevention. That is, if the bar fixing nut 60 is fastened in the case of a triangular screw, the fastening force is excellent, but the force transmission force is small in the longitudinal direction and the receiver member after fastening spreads in the radial direction. There are disadvantages that must be combined with the cap. And although a square screw is excellent in force transmission force in the longitudinal direction, it has a disadvantage that it may loosen after fastening. However, the trapezoidal screw allows the fastening force and the force transmission force to be maintained at appropriate values at the same time, and the cap does not have to be coupled to the outside of the receiver member.

  In the trapezoidal screw, the bar fixing nut is easily assembled, while the inclination of the upper side face (F1) of the thread is preferably larger than the inclination of the lower side face (F2) of the thread so as not to loosen. Specifically, the inclination of the upper side surface (F1) of the screw thread is 10 °, and the inclination of the lower side surface (F2) of the screw thread is more preferably 1 °. That is, if the angle of the upper side is larger than the angle of the lower side, the bar fixing nut 60 can be easily fastened when initially fastened on the upper side, and deformation is minimized even when a force acts in the opposite direction. The insertion of the threaded portion 78 and the bar fixing nut 60 is increased to improve the precision of the screw and prevent loosening.

  The bar fixing nut 60 has a cylindrical shape in which a thread 80 to be screwed to a threaded portion 78 of the receiver member is formed on the outer peripheral surface thereof. A hexagonal groove 82 is formed at the center of the bar fixing nut 60 and a hole 84 is formed at the same time. It is a structured.

  The assembly of the bone anchoring device according to the present invention constructed as described above is as follows.

  First, the bone screw 50 is inserted into the bore 70 of the receiver member 58 above the receiver member 58, the head 54 is seated on the multiple stepped portion 74, and the cap 56 is accommodated in the cap accommodating portion 76 of the receiver member 58.

  As shown in FIG. 8, the cap 56 is inclined so that one side of the flange 64 is first accommodated in the cap accommodating portion 76, and the other side of the flange 64 is locked to the end portion of the screw portion 78. After that, the cap 56 is pressed by the pressurizing tool (T) and the flange portion locked to the screw portion 78 is inserted into the cap housing portion 76 while causing plastic deformation together with the lower end portion of the screw portion 78. Thus, the cap 56 that has been plastically deformed and inserted into the cap housing portion 76 is not detached upward.

  The pressurizing tool T uses a tool in which a male screw to which the screw portion 78 is coupled is formed at the lower end portion. At this time, the screw outer diameter of the pressing tool T is determined in consideration of the depth (H2) of the lower thread of the threaded portion 78 so that the male screw of the pressing tool T completely passes through the threaded portion 78.

  Next, a surgical tool to be described later is screwed into the receiver member 58 and inserted into the hexagonal groove 62 of the head 54 through the hole 66 of the cap 56 to align the receiver member 58 and the bone screw 50, and then the surgical tool is rotated. The bone screw 50 is fixed to the bone, and the support bar (R) is seated on the upper side of the cap 56 across the U-shaped channel 72, and then the bar fixing nut 60 is tightened to fix the bone screw 50.

  The fastening force of the bar fixing nut 60 is transmitted to the head 54 through the support bar (R) and the cap 56 in order, and each protrusion angle (P1) (P2) of the multiple stepped portion 74 of the receiver member is the head 54. The lower end of the cap 56 is in line contact with the lower end corner (P3) of the cap 56 in line contact with the upper outer surface of the head 54, and the bone screw 50 is firmly fixed and supported so as not to move.

  As shown in FIG. 7, the bone screw 50 is tilted and fixed within a turning angle of about 26 ° around the central axis. However, a groove band 54a is asymmetrically formed on the outer surface of the head 54 of the bone screw 50 (spiral, Since the contact line (corner: P3) at the lower end of the cap 56 crosses the groove band 54a regardless of the fixing angle of the bone screw, the frictional force with the cap 56 is increased.

  FIG. 12 is a graph in which the supporting force of the bone screw of the bone anchoring device of the present invention and the conventional bone anchoring device is tested. After the bar fixing nut 60 is tightened with the same fastening torque (14 N.m), the static load is applied. 6 is a graph in which the head 54 yields and is displaced when the value is added.

  The test equipment was a universal compression tester (MTS 793), and the test method was performed according to ASTM F1717.

  FIG. 9 is a schematic diagram showing a test state. As shown in the figure, after the bone screw 50 is driven into the upper and lower objects (M) at intervals of 76 mm, the support bar (R) is connected and the bar fixing nut (not shown) is tightened, and then 40 mm from the head of the bone screw. FIG. 12 is a graph showing a state in which the object (M) is displaced by applying a load (F) to a distant place.

  In the graph, A is a graph for the product of the example of the present invention, B is a graph of the product manufactured by Patent Document 2, and C is a graph of the product manufactured by Patent Document 1.

  As shown in the graph, since the yield point of the conventional product is about 450 N and 300 N compared to the yield point of the product of the embodiment of the present invention is about 550 N, the supporting force of the bone fixation device of the present invention is It can be seen that it is extremely high.

  On the other hand, FIG.10 and FIG.11 represents the treatment tool used when the bone screw 50 in which the head 54 was accommodated in the receiver member 58 is fixed to a bone.

  As shown in the figure, the tool used when performing the operation with the bone anchoring device of the present invention is screwed into the tip protrusion 86 inserted into the hexagonal groove 62 that is the wrench insertion port of the bone screw 50 and the threaded portion 78 of the receiver member 58. An aligning rod 90 having a threaded portion 88 to be joined to align the bone screw 50 and the receiver member 58 of the bone anchoring device, and the tightening and relaxation forces of the bone screw 50 are enhanced to retract the receiver member 58. To facilitate, an outer pipe 94 having a flange 92 inserted and locked into the U-shaped channel 72 of the receiver member 58 and slidably coupled to the outside of the alignment rod 90 in the longitudinal direction of the alignment rod 90. And a handle 94 coupled to the alignment rod 90 so as to rotate the alignment rod 90.

  The handle 96 may be integrally coupled to the alignment rod 90. However, as shown in FIG. 10, the handle 96 may be detachably coupled to the end of the alignment rod 90 by a known detachable structure. preferable. The handle 96 is connected to a moving switch tube 98 which is elastically moved by a spring so as to lock / unlock the alignment rod 90.

  A handle portion 100 that protrudes perpendicularly to the longitudinal direction of the outer pipe 94 is formed at the upper end portion of the outer pipe 94 so that the outer pipe 94 can be easily moved. The width (W) and the protruding length (L) of the flange 92 are determined by the U-shaped channel 72.

  As shown in FIG. 11, the treatment tool configured as described above is configured such that when the screw portion 88 of the alignment rod 90 is rotated by the handle 96 in accordance with the screw portion 78 of the receiver member 58, the tip protrusion portion 86 of the alignment rod 90. Is inserted into the hexagonal groove 62 of the bone screw 50, and the receiver member 58 and the bone screw 50 are aligned to maintain a straight state. Therefore, the handle 96 is continuously rotated to easily bring the bone screw 50 into the bone. Can be fixed.

  At this time, if the flange 92 of the outer pipe 94 is inserted into the U-shaped channel 72 of the receiver member 58 and is rotated simultaneously with the handle 96 and the handle portion 100 of the outer pipe 94, the tightening force on the bone screw 50 is increased. Since the receiver member 58 is locked to the flange 92, the receiver member 58 can be easily removed at the same time when the bone screw 50 is loosened.

  The present invention is not limited to the embodiments, and can be implemented with various modifications.

  According to the bone anchoring device of the present invention, not only does the bone screw have a high supporting force to prevent movement, but also the assembly is easy, the force transmission force is large, the loosening is prevented, and the cap is prevented from being detached. Therefore, it is useful as a bone fixing device for fixing a bone such as a spine without being moved after calibrating it to a normal state.

It is sectional drawing which shows an example of the conventional bone fixing device. It is sectional drawing which shows another example of the conventional bone fixing device. 1 is a cross-sectional view showing a bone anchoring device according to the present invention. FIG. 3 is a separation view of a bone anchoring device according to the present invention. It is sectional drawing which shows the receiver member of FIG. It is sectional drawing which shows the cap of FIG. FIG. 4 is a detailed view of the outer surface of the head of the bone screw of FIG. 3. FIG. 3 is a state diagram of assembling a cap with the bone anchoring device according to the present invention. It is a use condition figure of the bone anchoring device by the present invention. It is a disassembled perspective view showing the tool used for the treatment of the bone fixing device by this invention. It is a use condition figure of the tool of Drawing 10. 3 is a graph showing a test of a supporting force of a bone fixation device according to the present invention and a conventional bone fixation device. It is the general | schematic route which showed the test state of the bone fixing apparatus.

Explanation of symbols

50 Bone screw 52 Spiral portion 54 Head 56 Cap 58 Receiver member 60 Bar fixing nut 64 Flange 68 Recess portion 70 Bore 72 U-shaped channel 74 Multiple stepped portion 76 Cap housing portion 78 Screw portion 86 Tip protruding portion 88 Screw portion 90 Alignment rod 92 Flange 94 Outer pipe 96 Handle

Claims (7)

A bone screw having a head, a cap for supporting an upper side of the head of the bone screw, and a U-shaped housing for receiving a support bar having a bore for engaging the head of the bone screw at the same time as the cap is received. A receiver member having a channel, and a bar fixing nut for fixing the support bar by screwing to the receiver member,
The bore is formed above the multiple stepped portion so as to be in line contact with the upper outer surface of the head and formed on the lower inner surface so as to increase the supporting force of the head, and to accommodate the cap. A cap accommodating portion, and a threaded portion formed with an inner diameter smaller than the inner diameter of the cap accommodating portion and to which the bar fixing nut is screwed.
A flange having an outer diameter larger than the inner diameter of the screw portion is formed at the upper end of the cap, and the cap is inserted into the cap housing portion by causing plastic deformation together with the lower end portion of the screw portion. Bone fixation device characterized. A plurality of groove bands are formed at predetermined intervals on the outer surface of the bone screw head so as to increase the frictional force with the cap.
2. The bone fixation according to claim 1, wherein the groove band is formed asymmetrically with respect to an axis of the bone screw so that a lower end contact line of the cap crosses regardless of a fixation angle of the bone screw. apparatus. The bone fixation device according to claim 2, wherein a depth of the groove band is 0.01 to 0.03 mm. The bone fixing device according to claim 1, wherein the receiver member has a hook shape in which a diameter of a central portion through which the support bar passes is larger than a diameter of an upper side and a lower side. When assembling the cap of the first item,
After tilting the cap, one side of the flange is first accommodated in the cap accommodating portion, and the other side of the flange is locked to the screw portion,
A bone fixing device, wherein the cap is pressed by a pressing tool and a flange portion locked to the screw portion is inserted into the cap housing portion while causing plastic deformation together with a lower end portion of the screw portion. Assembly method. A tool used when performing the operation with the bone fixation device according to the first aspect,
An alignment rod having a tip protrusion inserted into a wrench insertion port of the bone screw and a screw portion screwed to a screw portion of the receiver member, and aligning the bone screw and the receiver member of the bone fixation device;
A handle coupled to the alignment rod to rotate the alignment rod;
A surgical tool for a bone anchoring device comprising: A flange inserted into the channel of the receiver member and locked to the outside of the alignment member so as to facilitate the retraction of the receiver member by increasing the tightening force and the relaxation force of the bone screw. The surgical tool of the bone fixation device according to claim 6, wherein an outer pipe slidable in a longitudinal direction of the alignment rod is coupled.

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