US20050203530A1

Movatterモバイル変換

Info

Publication number: US20050203530A1
Application number: US11/106,576
Authority: US
Inventors: Kazuya Oribe; Nariyuki Ina
Original assignee: Showa Ika Kogyo Co Ltd
Current assignee: Showa Ika Kogyo Co Ltd
Priority date: 2000-03-28
Filing date: 2005-04-15
Publication date: 2005-09-15
Also published as: EP1639954B1; US6488682B2; US6932822B2; US20010029374A1; DE60136980D1; EP1639955A1; DE60127333T2; EP1138267B1; KR20010093725A; DE60130381T2; EP1138267A3; EP1138267A2; EP1639954A1; DE60127333D1; EP1639955B1; KR100396241B1; US20030018342A1; DE60130381D1

Abstract

A nut guide guides a nut member of a spinal implant having an implant body and an anchoring screw section, and also guides a driver tool having a lower end formed with a nut engagement tip. A a vertebral connecting rod therein is retained with a pair of the spinal implant to be anchored into vertebral bodies. The nut guide includes a grip section, and a hollow cylindrical shaft extending from the grip section and adapted to permit insertion of the driver tool therein, the cylindrical shaft having a lower distal end formed with a rod engaging segment for engaging with and retaining the connecting rod to place the lower distal end in a fixed place, and a threaded bore formed rearward of the rod engaging segment for momentarily receiving the nut member therein.

Description

This is a divisional of U.S. application Ser. No. 10/247,348, filed Sep. 20, 2002 which was a divisional of U.S. application Ser. No. 09/818,229, filed Mar. 27, 2001, now U.S. Pat. No. 6,488,682 issued on Dec. 3, 2002, the contents of which are expressly incorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION

The present invention relates to spinal implants for osteosynthesis devices and, more particularly, to a spinal implant, a driver tool specifically suited for the spinal implant, and a nut guide suited for the spinal implant.

In recent years, various research and development have been attempted to provide a spinal implant that is designed to achieve adaptation to differences in alignment, augulation and depth of penetration of adjacent spinal implants anchored to vertebral bodies which are spaced from one another.

One of such implants is disclosed in U.S. Pat. No. 5,154,719. This device includes a head portion having a pair of upright branches which are internally threaded and which has a U-shaped recess, and a screw portion projecting from the head portion. A connecting rod is received in the two branches, which are fixed in place by means of a ring member. During this operating step, there exist some difficulties in precisely adjusting the orientation of the U-shaped recesses of the spaced spinal implants anchored in vertebral bodies, angulation of the spinal implants and depth of the spinal implants, with a resultant undesirable fixation of the implants and the connecting rod. Since, further, the screw portion is composed of a solid material and the screw portion is merely anchored in the vertebral body. Accordingly, after the spinal implant penetrates in the vertebral body, fixation of the spinal implant is unstable and is liable to be undesirably affected with external forces when they are applied to the spinal implants.

U.S. Pat. No. 5,879,351 discloses a spinal osteosynthesis device comprising at least one vertebral rod, pedicle screws and deformable connectors. In this prior art, each of the pedicle screws is composed of the same solid material as in the prior art discussed above, and a difficulty is similarly encountered in reliably fixing the pedicle screw in the vertebral body. Further, each of the deforimable connectors has an oblong opening through which a head portion of the screw extends and each connector is resiliently supported between a cylindrical base and a nut, with a given space being provided for permitting relative movement of the vertebral rod. With such a structure, the spinal implant is caused to have a large number of component parts, resulting in a complicated structure and an increased cost.

In known techniques, it has been a usual practice to lock a plug into the spinal implant by means of a tool holder. In practice, there are two types of head section formed with two upright branches, that is, a first type of head section having an internally formed thread, and a second type of head section having an outwardly formed thread. In the first type, the plug is screwed in the internal thread of the head section. In this event, the two branches are loosened, thereby providing a difficulty in tightly locking the connecting rod in the spinal implant. On the contrary, in the second type, the plug is screwed onto the outer thread of the head section. In this event, an outer periphery of the plug has a hexagonal profile, and a driver tool having a hexagonal groove is brought into engagement with the outer hexagonal wall of the plug for rotating the plug. In this event, since the driver tool has an outer diameter larger than that of the plug, increasing an occupying space for rotating the driver tool. Under these conditions, when two spinal implants are anchored in adjacent vertebral bodies in a relationship closer to one another, the outer periphery of the driver tool is liable to interfere with the adjacent plug of the spinal implant, causing difficulties in rotating operation of the driver tool.

SUMMARY OF THE INVENTION

The present invention has been made with a view to overcoming the various disadvantages encountered in prior art devices and it is therefore an object of the present invention to provide a spinal implant for an osteosynthesis device, a driver tool for rotating the spinal implant, and a nut guide for guiding the implant body and the driver tool.

According to a first aspect of the present invention, there is provided a spinal implant for an osteosynthesis device having a vertebral connecting rod for interconnecting vertebral bodies spaced from one another. The spinal implant comprises an implant body including a head section having a threaded portion and a rod retaining recess opening outward for retaining the connecting rod therein, and an anchoring screw section longitudinally extending from the head section and adapted to be screwed into the vertebral body, a retaining plug coupled to the head section of the implant body to maintain the connecting rod in place, and rod movement stabilizing means directly located in at least one of the rod retaining recess and the retaining plug for allowing pivotal movement of the connecting rod in the retaining recess, thereby preserving mobility to the connecting rod.

According to a second aspect of the present invention, there is provided a driver tool for a spinal implant having an implant body and an anchoring screw portion, and a nut member screwed onto a head portion of the implant body and having an upper wall formed with a tool engagement groove. The driver tool comprises

an elongated shaft, and a tubular tool end having substantially the same diameter as that of the nut member, the tubular tool end having an engaging segment adapted to engage with the engagement groove formed on the upper wall of the nut member.

According to a third aspect of the present invention, there is provided a nut guide for guiding a nut member of a spinal implant having an implant body and an anchoring screw section, and for guiding a driver tool having a lower end formed with a nut engagement tip, wherein a vertebral connecting rod is retained with a pair of the spinal implant to be anchored into vertebral bodies. The nut guide comprises a grip section, and a hollow cylindrical shaft extending from the grip section and adapted to permit insertion of the driver tool therein, the cylindrical shaft having a lower distal end formed with a rod engaging segment for engaging with and retaining the connecting rod to place the lower distal end in a fixed place, and a threaded bore formed rearward of the rod engaging segment for momentarily receiving the nut member therein. The cylindrical shaft allows the driver tool to pass therein such that the nut engagement tip is brought into engagement with the nut member guided with the cylindrical shaft to move the nut member from the threaded bore to the implant body of the spinal body.

Other aspect and advantages of the invention will become more apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an osteosynthesis device incorporating a first preferred embodiment of a spinal implant according to the present invention, with a connecting rod being utilized to interconnect spaced vertebral bodies by means of plural spinal implants;

FIG. 2 is a side view illustrating the relationship between the plural spinal implants and the associated connecting rod;

FIG. 3 is an enlarged front view of the first preferred embodiment of the spinal implant according to the present invention;

FIG. 4 is a cross sectional view of the spinal implant shown inFIG. 3;

FIG. 5 is another cross sectional view of the spinal implant shown inFIG. 3;

FIG. 6 is a left side view of the spinal implant shown inFIG. 3;

FIG. 7 is an enlarged front view of a second preferred embodiment of a spinal implant according to the present invention;

FIG. 8 is an enlarged front view of a third preferred embodiment of a spinal implant according to the present invention, with the connecting rod being shown as being fastened by the spinal implant of the third preferred embodiment;

FIG. 9 is en enlarged, front view of a nut member forming part of the spinal implant shown inFIG. 8;

FIG. 10 is an enlarged, plan view of the nut member shown inFIG. 8;

FIG. 11 is an enlarged, bottom view of the nut member shown inFIG. 8;

FIG. 12 is an enlarged, front view of a driver tool specifically suited for use in the nut member shown inFIG. 8;

FIG. 13 is an enlarged view for illustrating the relationship between the spinal implant and a nut guide of a fourth preferred embodiment according to the present invention;

FIG. 14 is a side view of the osteosynthesis device shown inFIG. 13;

FIG. 15 is an enlarged, exploded view of the nut guide shown inFIG. 13; and

FIG. 16 is an enlarged side view of the nut guide shown inFIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings and more particularly toFIGS. 1 and 2, a spinal osteosynthesis device, generally designated at10, is shown as applied to separatevertebral bodies12 for interconnecting pluralvertebral bodies12 in place.

Thespinal osteosynthesis device10 includes an elongated vertebral connectingrod14 retained by a pair ofspinal implants16 of a first preferred embodiment according to the present invention. Each of thespinal implants16 penetrates eachvertebral body12 in a manner as will be discussed below in detail. The connectingrod14 is made of malleable, elastically deformable material having a large elastic capacity, permitting elastic deformation necessary for adaptation it to differences in alignment, angulation and depth of penetration of theimplants16.

Referring now toFIGS. 3 and 4, thespinal implant16 includes acylindrical implant body18 for firmly retaining the connectingrod14 in place, and ananchoring screw section20 that longitudinally extends from theimplant body18 and adapted to be anchored in the vertebral body12 (seeFIGS. 1 and 2).

The anchoringscrew section20 has a hollowinternal fusion chamber22, and a plurality ofspinal openings24 each of which is composed of a longitudinally extending elongated slit. Each of theelongated slit24 transversely extends through the anchoringscrew section20 from one side to the other side and communicates with theinternal fusion chamber22 to permit borne ingrowth into thefusion chamber22. Thus, the anchoringscrew section20 has a plurality of circumferentially spaced,elongated wall segments26 defined between the hollowinternal fusion chamber22 and theplural slits24, providing elastic deformation to theanchoring screw section20 to allow adaptation of any positioning of the threaded section while permitting an effective fixation without impairing the borne anchorage.

A head portion of theimplant body18 is formed with a U-shapedrod retaining recess28 that opens outward, and an internally threaded bore30 extending in a longitudinal direction at a position adjacent therod retaining recess28. A disc shapednut member32 is screwed into the internally threaded bore30, thereby retaining the connectingrod14 in place in therod retaining recess28.

As seen inFIGS. 5 and 6, abottom wall34 of the retainingrecess28 includes a rod movement stabilizing means35 composed of slanted engagement surfaces36 directly located in therod retaining recess28 for allowing pivotal movement of the connectingrod14 in the retainingrecess28, thereby preserving mobility to the connectingrod14. To this end, each of the slantedengagement surface36 is slightly inclined from points slightly displaced from the center of axis of theimplant body18 at an angle ⊖ from an axis of the connectingrod14 perpendicular to the axis of theimplant body18.

With such a structure, the connectingrod14 is allowed for pivotal movement within a range defined by the slanted engagement surfaces36 of the retainingrecess28 of theimplant body18. Thus, the slanted engagement surfaces36 of the rod movement stabilizing means35 is defined in the retainingrecess28 of theimplant body18, allowing the connectingrod14 to be inclined.

Although, the connectingrod14 is inclined in a plane involving the center of axis of theimplant body18, the slantedengagement surface36 of the rod movement stabilizing means35 may be modified such that the connectingrod14 is allowed to be slightly inclined in a plane crossing the central axis of theimplant body18. More particularly, as shown by a phantom line inFIG. 6, the retainingrecess28 has inclined engagement surfaces40 formed in a longitudinal direction in right and left directions inFIG. 6, except for the threadedportion38.

With the structure discussed above, the pluralspinal implants16 are screwed into and anchored in separatevertebral bodies12 in a manner as shown inFIGS. 1 and 2 such that the associatedrod retaining sections28 of twoimplant bodies18 are aligned, and both ends of the connectingrod14 are received in theimplant bodies18. In a subsequent step, thenut member32 are screwed into the threadedportions30 of theimplant bodies18, respectively, firmly retaining the both ends of the connectingrod14 to clamp the same in the required position.

Due to the separateelongated wall segments26 formed in the anchoringscrew section20, the anchoringscrew section20 is allowed to be penetrated into thevertebral body12 in reduced diametrical size owing to the inward elastic deformation of the separateelongated segments26, thereby providing ease of penetration of theimplant16. Since, also, when the penetration of the anchoringscrew section20 has been completed, the separateelongated wall segments26 expand to their original position due to their restoring forces, thereby providing an improved fixation, in an early stage, of thescrew section20 to thevertebral body12 in a highly reliable manner. Owing to the provision of the plurality of spinal openings defined by theelongated slits24 and the hollowinternal fusion chamber22, further, thespinal implant16 permits borne ingrowth into thehollow fusion chamber22 for thereby further improving fixation of the implant.

In a event the both ends of the connectingrod14 are fitted to the retaining recesses28 of theimplant bodies18 after the pluralspinal implants16 are firmly fitted to thevertebral bodies12 in a manner discussed above, if the rotational positions of the retaining recesses28 of the pluralspinal implants16 are not aligned with one another, a desired one of thespinal implants16 may be slightly rotated. In addition, further, when the depths of penetration of the pluralspinal implants16 are different from one another and the pluralspinal implants16 undergo misalignment in height, the connectingrod14 is partly allowed to be suitably deformed along the slantedsurface36, absorbing a slight difference in height of the bottom walls of the pluralspinal implants16 penetrated in thevertebral bodies12.

In other words, even when there exists a slight difference in height between thebottom walls34 of the adjacentspinal implants16, the connectingrod14 is reliably adaptable to that difference, providing improved engagement of the connecting rod in the plural spinal implants in an easy and simplified manner.

FIG. 7 shows a second preferred embodiment of a spinal implant according to the present invention, with like parts bearing the same reference numerals as those used in FIGS.1 to5.

Thespinal implant16 ofFIG. 7 differs in structure from the first preferred embodiment of the spinal implant in that theimplant body18 has arod retaining recess40 composed of a longitudinally extending oblong opening and a distal end of theimplant body18 has a laterally extendingtool engagement groove42. Thespinal implant16 of the second preferred embodiment has the same advantages as those of the first preferred embodiment discussed above. Other features of the second preferred embodiment of thespinal implant16 are identical to those of the first preferred embodiment and, accordingly, a detailed description of the second preferred embodiment of thespinal implant16 is herein omitted for the sake of simplicity.

FIGS.8 to11 show a third preferred embodiment of a spinal implant according to the present invention. InFIG. 8, thespinal implant16 includes animplant body18 and an anchoringscrew section20 having a plurality ofsmall apertures46 extending in a plane perpendicular to the axis of thescrew portion20 to allow borne ingrowth therein. Theimplant body18 has an upper end formed with anouter thread50, to which anut member52 having an upper wall formed withtool engagement grooves56 is screwed. Theimplant body18 also has aU-shaped retaining recess54, with which a spherical engaging segment14aof a connectingrod14 engages for pivotal movement.

As best seen inFIG. 10, theimplant body18 has a pair of

upright retaining segments

18A,18B providing relativelylarge spaces62 and each having an arch-shaped cross section. Thus, the

upright retaining segments

18A,18B provide an open distal end such that when the spherical engagingsegment14A is retained in theU-shaped recess54, the connectingrod14 is allowed for pivotal movement relative to the central axis of thespinal implant16.

Thenut member52 has a ring-shape having an inner thread engaging theouter thread50 of theimplant body18. An upper side of thenut member52 has a plurality oftool engagement grooves56 that cross each other in lateral direction. As best seen inFIGS. 9 and 10, the ring-shape nut member52 receives therein acentral pivot shaft58 coaxially extending through thenut member52. A lower ends of thecentral pivot shaft58 is integrally formed with arod retaining member60, that includes a central, globular retaining groove60a, and a pair of laterally extending arch-shaped retaininggrooves60b. As seen inFIG. 9, therod retaining member60 projects downward from a lower distal end of thenut member52. Therod retaining member60 has a radial length substantially equal to the diameter of thenut member52 and has a lateral width slightly smaller than the width of therod retaining groove54. An upper end of thecentral pivot shaft58 has acircular flange58ahaving substantially the same shape as therod retaining member60.

InFIGS. 8 and 12, there is shown a fourth preferred embodiment of adriver tool70 for rotating thenut member52. Thedriver tool70 includes a hollow,tubular tool end72 and anelongated shaft74 extending upward from thetubular body72. A lower end of the tubular body has a plurality of substantially axially extending engagingsegments72athat are adapted to engage with thetool engagement grooves56 formed on the upper wall of thenut member52. Thetubular body72 is designed to have a diameter substantially equal to thenut member52.

With such a structure discussed above, the anchoringscrew sections20 of the pluralspinal implants16 penetrates the vertebral bodies and, subsequently, the connectingrod14 and the spherical engaging segment14aare located in therod retaining groove54 of theimplant body18. In next step, therod retaining member60 is brought into engagement with therod retaining groove54 of theimplant body18, and thenut member52 is screwed into theouter thread50 of theimplant body18. Thenut member52 is rotated with thedriver tool70 of which engagingteeth72ameshes with thetool engagement grooves56 of thenut member52, such that thenut member52 is fixed in place. This movement is enhanced with the aid of thedriver tool70, providing ease of fixing operation of thenut member52 to theimplant body18. As previously discussed, since thetubular body72 has substantially the same diameter as thenut member52 and an outer periphery of thetubular body72 of thedriver tool70 does not interfere with an outer periphery of the adjacent retaining plug, thereby enhancing easy fixing operations of thedriver tool70 with respect to the adjacent retaining plugs located in a narrow space. Thetool engagement grooves56 may not be limited to the specific groove shown inFIGS. 8 and 9, but may have any other configuration such as a bore.

FIGS.13 to16 show a fifth preferred embodiment of a driver tool according to the present invention, with thespinal implant16 being identical in structure with that of the first preferred embodiment except that the retainingplug32 has a non-circular,hexagonal engagement groove32A. In the fifth preferred embodiment, an upper end of adriver tool78 has agrip section78a, and a lower portion formed with atool end78bthat has a hexagonal,nut engagement tip78c. Thedriver tool78 is used in combination with anut guide80 that includes agrip section84 and a hollow,cylindrical shaft82. Thegrip section84 has an inner guide bore84athat is adapted to receive thegrip section78aof thedriver tool78. Thecylindrical shaft82 has an axially extending through-bore86 to guide thedriver tool78. A lower end of thecylindrical shaft82 has an inner threaded bore88, anut guide chamber90, an engagingguide chamber92, and arod engaging recess94 that is adapted to receive the connectingrod14. Plural preliminary mounting stems98 are fixedly connected to a mountingbase96 for temporarily supportingrespective nut members32 on top ends of the stems. Thenut members32 have thehexagonal engagement grooves32a, respectively.

In operation, the pluralspinal implants16 are sequentially fixed into thevertebral bodies12, and the connectingrod14 is suitably located in the rod retaining recesses28 of theimplant16. In a subsequent step, thenut guide80 is placed on one of thenut members32, which has been placed on the mountingstem98, such that thenut member32 is guided through thenut guide hole90 of thenut guide80. Thenut member32 is thud held with thenut guide80, and thenut guide80 is moved to an operating position shown inFIG. 13. In this event, therod engaging recess94 of thenut guide80 is aligned with the connectingrod14 such that the upper portion of theimplant body18 engages with the engaging guide bore92 of thenut guide80 in a manner as shown inFIG. 13. Then, thedriver tool78 is inserted through thenut guide80 until theengagement tip78cengages with thetool engagement groove32aof thenut member32, and thedriver tool78 is rotated to cause thenut member32 to be screwed into theimplant body18 of thespinal implant16 until thenut member32 is brought into contact with the connectingrod14. Accordingly, thenut member32 is easily secured to theimplant body18 in a highly reliable manner without causing any misalignments or difficulties.

The spinal implant, the driver tool and the nut guide of the present invention provide numerous advantages over the prior art practices and which include:

(A) The spinal implant includes an implant body for retaining a vertebral connecting rod, and an anchoring screw section longitudinally extending from the implant body and adapted to be anchored in a vertebral body. The anchoring screw section has a plurality of spinal openings to permit borne ingrowth therein, with a resultant improved fixation of the spinal implant. Each of the spinal openings includes a longitudinally extending slit or laterally extending bore that thoroughly extends from one side to the other side.

- (B) The anchoring thread section may also have a hollow, internal fusion chamber communicating with the spinal openings and longitudinally extending through the thread section to allow borne ingrowth therein. With this structure, the spinal implant can be anchored in the vertebral body with a suitable fixing condition in an early stage and, in a subsequent stage, the spinal implant can further be firmly anchored in the vertebral body owing to the borne ingrowth progressed in the spinal openings and the internal fusion chamber. This results in a reliable fixation of the spinal implant relative to the vertebral body for an extended time period.
- (C) A head portion of the implant body has a rod member stabilizing means to retain the connecting rod relative to the adjacent spinal implants for adapting it to the differences in alignment between a rod retaining section and the connecting rod, the height of the rod retaining section, and angulation and depth of penetration of the anchoring screw sections. Thus, the connecting rod can be easily supported in place with the adjacent spinal implants without causing any complicated, troublesome alignments or adjustments of angulation and depth of penetration of the anchoring screw sections.
- (D) The spinal implant also includes a nut member which is designed to be screwed into a head portion of the implant body, with the nut member including a rod retaining member for retaining the connecting rod in place in the implant body while permitting pivotal movement of the connecting rod, thereby preserving smooth mobility to compensate for positional misalignments or erroneous orientation between the adjacent spinal implants.
- (E) A driver tool is employed to rotate the nut member relative to the implant body, with the driver tool having at least one engaging segment that engages with an engagement groove of the nut member and having substantially the same diameter as that of the nut member, enabling the driver tool to drive the nut member of one of the spinal implants in an easy manner without conflicting the adjacent nut member of the other spinal implant closely positioned to the former spinal implant.
- (F) A nut guide is proposed for reliably guiding the nut member to be easily removed to the anchored spinal implant in a highly reliable manner, and a driver tool is also guided by the nut guide to cause an engaging tip of the driver tool to precisely engage with the engaging groove of the nut member of the spinal implant. Consequently, the nut member can be smoothly coupled to the implant body within a short time period without causing rotation of the implant body relative to the vertebral body.

The foregoing description of the preferred embodiments of the invention ha been presented to illustrate the principles of the invention and not to limit the invention to the particular embodiments illustrated. For example, although the preferred embodiments have been illustrated and described that the anchoring screw section of the spinal implant includes a spinal opening composed of an elongated slip or plural laterally extending bores, the spinal opening may have any other suitable configurations such as an oblong opening or an elliptical bore. It is intended that the scope of the invention be defined by all of the embodiments encompassed within the following claims, and equivalents thereof.

Claims

1. A nut guide for guiding a nut member of a spinal implant having an implant body and an anchoring screw section, and for guiding a driver tool having a lower end formed with a nut engagement tip, wherein a vertebral connecting rod is retained with a pair of the spinal implant to be anchored into vertebral bodies, the nut guide comprising:

a grip section; and

a hollow cylindrical shaft extending from the grip section and adapted to permit insertion of the driver tool therein, the cylindrical shaft having a lower distal end formed with a rod engaging segment for engaging with and retaining the connecting rod to place the lower distal end in a fixed place, and a threaded bore formed rearward of the rod engaging segment for momentarily receiving the nut member therein;

wherein the cylindrical shaft allows the driver tool to pass therein such that the nut engagement tip is brought into engagement with the nut member guided with the cylindrical shaft to move the nut member from the threaded bore to the implant body of the spinal body.

2. A nut guide according toclaim 1, wherein the cylindrical shaft further has a nut guide hole formed between the threaded bore and the rod engaging segment.