CA2240979C - Osteosynthesis apparatus - Google Patents

Abstract

A bone fixation apparatus (10) is disclosed which includes an elongated plate member (12) with at least two pairs of circular openings (24 26) and a series of circular openings (62) positioned along the plate member (12). The circular openings each form a cavity (30) with walls (31) extending between the upper and lower plate member surfaces (16, 18), the cavities having smaller diameter portions (32) at the plate member surfaces (16, 18) and a larger diameter portion (34) therebetween. The cavities are configured in the shape of two inverted cones (31a 31b) with matching base circles (31c) for allowing angulation of an implanted bone screw (14). A plurality of bone screws (14) are provided, each having a threaded first end portion (36) and an ellipsoid-shaped enlarged second end portion (40). A locking member (48) is also provided which connects to the second end portion (40) of each bone screw (14) for expanding the second end portion (40) so as to grip the cavity wall (31) of the plate member (12).

Description

~QSYNTHESIS APPARATUS
~ 5 The present invention relates to an improved bone or spinal fucation apparatus in the fornn of an elongated plate member and a ' locking bone screw The apparatus has particutar utility in anterior cervical spine fixation by providing a plate that allows for angulation of the bone sa~ews and a locking bone screw that secures the bone screws into the plate member at a selected angle corresponding to a thick region of the bone mass.
There are a number of surgical procedures which require fixation of portions of the spine with respect to one another.
Typically, bone saeuvs are employed in the fixation of the spine where the implantation of the bone screws is a surgical procedure in which one or more surgical openings are formed in adjacent portions of the spine and threaded bone screws are implanted into the surgical openings. Connective structures such as rods or plates extend befinreen the various spine members and are connected to the spine members by the imptanied bone scr~.
In the treatment of spinal disorders and spinal fractures, both a posterior and an anterior approach is used. The use of plating systems for posterior internal fixation of the spine is well known.
Additionally, several plating systems have been.developed for anterior internal fixation of the spine. For example, the Syracuse I-ptate provides a number of differently sized 1-shaped plates which are engaged across the vertebrae. A contoured anterior spinal fixation plate is known which includes a number of scre~nr openings through the contoured plate. The number of openings simply provide dHierent locations for engaging a bone screw to the vertebrae, and does not allow for anguiation of the bone scre'ws_ A
further problem with the application of: spinal fixation systems is the WO 97/22306 PCT/~JS96/20707 placement of such a system in the cervical region of the spine where cornact anatomical fit and Iadc of bone mass presents a problem.
Irven with these known posterior and anterior plate fixation systems, there remains a need for a plate and scxaw syrstem that , allows for vartativn in saeHr placement along the longitudinal axis of tho plate as wail as pnwiding for angutation in both the mediel-lateral or transverse plane and the cephatad-caudal or longitudinal piano. There is also a need for a fixation system that provides a '10 cocking bona scarew mechanism for searnely fastening the bone screw in a selected angled position within the piste particutaity for locking a bone screw in the 'center portion of the plate. There is futthar a need for a fixation plate that is curved to ftt the contours of the vertebrae and is also somewhat bendabis during implantation 45 but rigid enough to allow fusion to take place after implantation.
It is thus an object of the present invention to provide a bone fixation system that offers a strong and stable construe for maximum fusion augmentation of any bone structure and yet is 20 versatile enough for a variety of bone configurations and is easy to use.
A~cc~orciing to the present invention a bone frxafion apparatus comprises a) An elongated plate member having a Longitudinal plane, a longitudinal axis, upper and lower surfaces, opposed longitudinal side edges, at least two pairs of circular op~ings and a pluraisfy of cicrutar openings positioned along the iongituddnai plane ' of the plate member, said circular openings each having a central vertical axis; , WO 97/22306 PCT/US9b/20707 b) said cir~cutar openings each forming a cavity with waits extending between the upper and lower plate member surtaces with , et least a plurity of said cavities having smelter diameter portion therebetwaen, for allowing transverse and longitudinal angulation of an implanted bone saew~, c) a plurality of bone screws each having a threaded first end portion adapted fior implantation into a patient's bone mass and an enlarged second end portiono end d) a locking member that connects to the second end portion of each bone screw for racpanding the second end portionso as to form an interf~rence bit t~etw~een the cavity welt of the plate member and said enlarged second end portion of the bane screw , thereby to lode ecah bone screw into a selected position within said cit Cuter openings of the plate member.
'd 5 The present invention provides an apparatus that can be used on any segment of the spine and in psrtiartar can be made smelt enough for anterior oenrical spine applications.
The cavities are preferably configured in the shape of two inverted cones with matching base circles for allowing transverse and longitudinal angulation of an implanted bone scnew.
The bone fncation apparatus further includes a plurality of bone screws each having a threaded end for implanting into a patien t's bone mass and an ellipsoid shape enlarged second end portion. The second end portion has a locking member for expanding the second end portion so as to grip the cavity wail of the plate and for locking each bone scxew into a selected position within the circular openings of the plate.

According to the invention we also provide a bone fixation apparatus, ay having a longitudinal plane, a longitudinal axis, upper and Iowa surfaces, opposed longitudinal side edges, at least two pairs of circular openings and a plurality of generally circular openings positioned along ~e longitudinal plane of the plate member, said rin~,rlar openings each having a central vertical axis;
b) said circular openings each forming a cavity with walls 90 eoctending beiween the upper and tower plat~ member surfaces with at least a plureility of said cavities having smaller diameter portions at the plate member upper and lower surfaces and a larges diameter portion therebstween, for allowing transvenre arid I~gitudinat angulation of an implanted bone screw;
9 5 c) said plate member having a first end, a second end and a portion wherein the width of the plate is smaller in the region of the center portion than at the first and second ends; and d) said one pair of circular openings being positioned at the first end of the plate member and the second pair of circular 20 openings being positioned at the second endo~f the plate member.
For a further understanding of the natures and objects of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying 25 drawings, in which lik~ parts are given like reference numbers, wherein:
Figure 'I is an anterior view of an embodiment of the apparatus of the Present invention illustrating its placement on the anterior cervical bone tissue;
30 Figure 2 is a plan view of an emtx~iment of the apparatus of the present invention illustrating a plate member, Figure 3 is a side view of the plate shown in Figure 2;

Figure 3A is a sick view of an attemate embodiment of the plate shaam in Fig. 2;
Figu~ 4 is a sectional view of a portion of the plate shown at fines ~4-4 of Figure 2;

5 Figure 5 is a sectional view of a portion of the plate shown at tines 5-5 of Figure 2;
I~igure 6 is a partial sectional view of the plate shown at lines 8-6 of Figure 2;
Figure T is a front view of an embodiment of the apparatus of the preserif invention illustrating a locking bone saw;
Figurre 8 is a front view of an embodiment of the apparatus of the ptesent invention illustrating a Locking mem~r that connects to the bone screw of Figure 7;
Figure 8 is a top view of the bone screw of Figure 7 with the loddng member of Figure 8 in its locked position;
Figure 10 is a fragmentary sectional view of an embodiment of the apparatus of the present invention illustrating the bone screw of Figure 7 ptaoed in an angled position;
Figure 11 is a fragmentary sectional view of an embodiment of the apparatus of the present invention~illustrating a longitudin9l range of anguiatian of an implanted bone screw;
Figure 12 is a fragmentary sectional view of an embodiment of the apparatus of the present invention illustrating a transverse range of angutafion of an implanted bone scxew;
Figure 13 is a plan view of another embodiment of the apparatus of the present invention illustrating a plate member, Figure 14 is a plan view of another embodiment of the apparatus of the present inv~ntion illustrating a ptate member, Figure 15 is a plan view of an alternate configuration of the openings of the plate member of Fg. i 4; and ~ Figure 16 is a ~ptan view of an alternate configuration of the openings of the plate member of Fig. 14.

FIGS. 9 show the various embodiments of the bone fixation ~paratus of the present inverttion, designated generally by the numeral ?0, implanted on the anterior side of cervical vertebrae V of a human patient. The bone fixation apparatus 10 includes a plate member 92 and locking bone screws i4. The plate 92, as shown in FtG. 2, is an elongated plate member 12 having a longitudinal axis LA, s iong'rtcrdinat plane LP and upper arxi lower surfaces 16, 18.
The piste member 12 has apposed longitudinal side edges 20, 22, 7 0 first and second ends 23, 25 and a her portion 21. The center portion 21 preferably has a generally smaller width in relation to a larger width at the first and second ends 23, 25. Plate member 12 hae a transverse plane TP (FIG. 2) and the plate member 12 can be curved along the transverse plane TP. if arrved, the radius of the '! 5 transverse curve cross-section is between about 22.0 to 7T.0 millimeters and is illustrated in FIGS. 4 and 5. As shown in FIG. 3, the plate member 92 can be generally flat elong the longitudinal p(aneLP or the plate member t2 can be curved along the longitudinal plane as illustrated in I=IG. 3A The longitudinal curare 20 can halve an arc angle of between about 6' to 40'. The curve in both the transverse plane and the longi~tudinai plane will allow the plate member 12 to achieve a better fit in on the selective vertebrae particularfy in the anterior cervical portion of the spinal coiumn_ 25 The plate member 12 includes a pair of ciroular openings 24 positioned at its first end 23 and a second pair of circular openings 26 positioned at its second end 25. A series of openings, such as at least one elongated slot 28 is positioned along the longitudinal pDane LP of the plate member 12. The series of openings can be .
30 positioned along the longitudinal axis LA or offset from the longitudinal axis LA, tn one embodiment three elongated slots 28 are positioned along the long'rtudinat axis LA of the plate member ~

12. The circx~lar openings 24, 26 snd elongated slots 28 have a central vertical eras CA, as illustrated in FIGS. 4 and 5. tn an alfemate embodiment, more than two pairs of circular openings can be placed on the ends of the plate member 12.
The openings 24, 2fi and the elongated slots 28 of the plate member 12 each form a cavity 30 with angled wails 31 extending between the upper and lower plate member surtaces 16, 18. The angled walls 31 form two inverted cones 31a, 31b with matching base circles 31 c. The cavities 30 have smaller diameter wail portions 32 at the upper and lower plate surfaces 16, 18 and a central lar~er diameter wall portion 34 tharebetv~rsen. The diameter of the wait portions 32 are larger at the upper surface 16 than the diameter of the wall portions 32 at the lower plate surface 18, but 9 5 the diameter of the watt portions 34 is always larger than that at both the upper and lower surfaces 16, 18. The slightly smaNer diameter of the wail portions 32 at the tower surface 18 of the plate member 12 keeps the bona screw 94 from slapping through the cavities 30 prior to insertion of the locking membex 48 into the central bore 42 of the bone screw 74. The angufation of the wall surtaces 31 or the inverted cones 31 a, 31 b, between the upper and lower piste surfaces 16.18, is generally about between 110° to 160°. The cavities 30 of the openings 24, 26 and.slots 28 are shaped to allow for a transverse angulation of each of the bone stxews 14 generally up to about 35' in both directions from the central vertical axis CA of the openings 24, 26 and slots 28 when each of the bone screws 14 is inserted into the openings 24, Z6 and slots 28 (FIG. 12). The cavities 30 of the openings 24, 26 are shaped to allow for a longitudinal angutation of each of the bone saews 14 generally up to about 35' In both directions from the central vertical axis of the ~ openings 24, 26 when each of the bone scxews 14 is inserted irrfio eacri of the openings 24, 26 (FIG. 12J. The cavities 30 of the slots WO 97J2230b PCT/LTS96/20707 28 are shaped to aiiow for a longitudinal angulation of each of the bone screws 14 of generally beiween 0' to 130' in both directions from the central vertical axis of the slots 28 when each of the bone screws 14 is inserted into each of the slots 28 (FtG. 11 ). The openings 24, 26 and slots 28 have a beveled surface 15 on the upper and Power plate surfaces 76, 18 as illustrated in FIGS. 4-6.
The geometry of the plate member 'l2, plus the load factors of the openings 24. 26 and slots 28, allow the plate member 92 to be somewhat bendabte during.implantation while still maintaining the rigidity needed for adequate fixation and immobilization of the vertebrae. Additionally, the ability of plate member 12 to have either a transverse or longitudinal curve allows for a closer fit to the contours of the vertebrae.
FtG. 13 illustrates plate member 12A, an attemate embodiment of plate member 12, having a plurality of openings 60 positioned along the longitudinal plane t_P of the plate member 1?A
The provision of a plurality of circular openings along the longitudinal plane of the plate member offers the flexibility of choosing one of a number of different positions along the length of the plate in which to secure a bone screw and thus th~r screw may be placed in the part of the bony mass to be secured which appears most advantageous to the.surgeon_ Although the provision of slots along the longitudinal plane of the plate offers a great deaf of choice in the tangitudina! placement of the screws, cirrxrlar openings may provide a more secure fixation between the scxew head and th~
plate because the area of contact between the screw head and the plate is greater. Each circular opening 60 is spaced at least about 1.8 to Z.0 millimeters apart front each other. The plurality of openings 60 can include any number of individual openings and in a prefiemed embodiment up to about sixteen (16? individual openings WO 97!22306 PCT/US96/20707 60. Each of the plurality of openings 60 has the same configuration as the openings 24, 26. All other aspects of plate member 12A are the same as piste member 12.
FIGS. 14-16 illustrates another alternate embodiment plate member 92, plate member 128, which has a plurality of cir~cutar openings 62 positioned along the longitudinal plane LP of the plate member 12B with each circular opening 62a being connected to a next circular opening 62b by a narrow slot 64. The nan-ow slot 64 has a width that is equal to about between 113 to 1I2 the diameter of each circular opening 62 and s length that is between about 1.4 to 2.00 millimeters. The width of the narrow slot 64 is smaller than the diameter of any bone screw that would be inserted into the circular openings 62 and does not allow for the sliding of a bone screw between the citcular openings 62a and 62b. The non ow slots 64 allow for controlled flexing of the plate member 9 2B. The slots may also be beneficial in assisting the surgeon to stabilise the plate during implantation because an instrument may be inserted info the openings to hold the plate in position end, by keying into one or more of the narrow slots, the torsioriai movement of the plate may be controlled. Also, where the circular openings are set relatively close together and are wider in a plane located between the upper and lower surtaces of the plate than at the upper anri lower surfaces, the piste may be easier to manut~acture when adjacent holes are connected by a narrow slot.
The connected circular openings 62 can be in groupings of two circular openings, three circular openings or four circular openings as illustrated in t=IGS_ 14-16. The groupings of circular openings 62 on the plate member 12B can be in any combination of the groupin8s of two, three or four circular openings 62, An example of the various combinations on plate member 12B is WO 97/223fl6 PCT/C1S96/20707 1a illustrated in FIGS 14-16. Each grouping of circular openings fit is no fees than 'f .5 miitimeters apart from the next grouping of cirnuBar openings 62. Each of th plurality of openings 62 has the same configuration as the openings 24, 26. Aii other aspects of plate member '! 2B are the same as plate member 12.
The bone screw 14 (FiG. 7) has an elongated shank 36, a lower tip 37, and an enlarged upper portion 40 affixed to cue end of the shank 36. The Iower tip 37 of the bane scxew 14 communicates with a helical thread 38 that begins at the lower tip 37 and terminates at the upper portion 40_ The enlarged upper portion 40 has a generafiy ellipsoid-shaped outer surtace 41, a generally ~ylindricat central bore 42 and upper wails 43. The upper wails 43 of the enlarged portion 40 have at least 2 radial slits 44 intersecting the bore 42, and in a preferred embodiment, four radial silts 44 intersecting the bore 42, as seen in F1G. 9. The central bore 42 includes irttemal threadins 46 on a portion of the cylindrical surface 45, as illustrated in FIGS. 7 and 10. The ellipsoid-shaped surface 41 of the upper portion 40 interfaces with the cavities 30 of the openings 24, 26 and elongated slots 28 (see FiG. 10) or the plurality of circular openings 60, 62, as will be described more fully her~einatter.
A Locking member 48, as shown in F1G. 8, has lower and upper portions 50, 52 respectively and a top surface 51, with the locking member 48 being sized and shaped to ~t into the cylindrical cer~rai bore 42 of ~e bone screw 14. The locking member 48 includes extdmal threading 54 on its lower pardon 50 which engages the corresponding internal threading 46 of the central bore 42. A toot receptive socket such as hexagonal socket 56 (PIG. 9) is provided on the flat top surface 51, so that the locking member 48 can be rotated using a hexagonal wrench or other such tool or WO 97/22306 PCTlUS96/20707 instrument. When locking mamber 48 is threaded into the central bore 42 of bone screw i4, the upper walls 43 expand oufw~ardly further enlarging the upper portion 40.
As shown in FIGS. 10-12, the angular shape of the cavity walls 31 allows for both transverse and i~gitudingi sngulatlon of en implanted bone screw 14. Trie ellipsoid-shaped surtaoe 41 allows the upper portion 40 of the bone scrow 14 to be freely rotateble within the plats member cavity 30 prior to insertion of the loddnp member 48. After the bone screws 14 have been positioned within the openings 24, 26, slots 28 or plurality of circular openings fi0, 62 of the plate members 12, 12A or 128 and implanted in the vertebrae of a patient, the iodcing members 48 are threaded into the central bore 42 of the bone screws 94. The threading 54 of the toddnp member 48 engages the thn3ading 48 of the central bore 42 and the radial slits 44 allow the upper wall portions 43 to expand outwardly as the locking member 48 is tightened into the central bore 42 (FiG.
9).
When the ioddng member 48 is threaded into the central bore 42 of bone scxew 14, the ellipsoid-shaped outer surtace 41 of the upper portion 40 expands to a spherically-shaped outer surtace 41 a which causes the upper wall portions 43 to grip the cavity walls 31 so as to lack each bone screw 14 into a selected position within the openings 24, Ze, slots 28 or plurality of circular openings fi0, 62 of the plate members 12, 12A or 128 as ilfusbattd in FIGS. i i and 12. The geometry of the final expanded shape of the sphericaily-shaped outer surface 14 allows for an interfenencs fit that provides a solid rigid mating mechanism within the sonically-shaped cavities 30. The two inverted cones 31 a, 31 b with the matching base circles 31 a of the cavities 30 provide for Iine cornact with the apherically-shaped expanded outer surtace 41 of the upper wails 43. This allows for a secure locking mechanism between the bone screw 14 and the plate member 12. This is particularly true because a spherically-shaped bone screw will deform into an eltipsoid.shape wh~n expanded which will not engage in fine contact with a spherically or conicalfy shaped opening. The inventive locking mechanism between the plate member 12, 12A or 12B and the bone screws 14 locks the bone scx~surs 14 into the piste member 12, 12A
or 12B which prevents the implanted bone screws 14 from baddng out of the plate member 12, 12A or 128. This in tum prevents the bone screws 14 from backin8 out of the vertebrae. The ability of the inventive bone fixation apparatus 10 to lock the bone screws 14 into the plate member 12, 12A or 12B is critical in anterior cervical spine applications because if implanted bone screws back out of the vertebrae in this area of the spine the bone sa~ews can cause serious injury to the patient. The present locking mechanism, plus 1 S the geometry of the plate member 12, 12A and 12B allows the bone fixation apparatus 10 to provide a rigid construct when in'~tiaHy implanted. However, as the implanted bone scxews loon over tirtte, the bone fucation apparatus 10 becomes semi-rigid and provides a construct that is somewhat flexible and compliant.
I=urther, the loddng mechanism and the plate geometry allows for variable initial rigidity at the bone screw 14 and plate member 12, 12A and ~12B interface. Variable rigidity of the locking mechanism means that the bone screw 14 can be locked into the plate member 12, 12A or 12B so as to provide a very rigid interface botween the bone screw end the plate member in which there is no movement of the bone screw 14 within the cavity 30 or the bone screw 14 can be .
locked into the plate member 12, 12A or 12B so as to provide a less rigid intertace beiw~een the bone screw and the plate member in which there is a small amount of movement or flexing of the bone scxew 14 within the cavity 30.

During implantation, the configurettion of the openings 24, 2fi provides secure fixation at the ends of the plate meMbet 12, 12A
and 12B while the riots 28 and plurality of circular openings 60, 62 provide for a variation in screw placement along the fongitudinai axis ofi the plate member 12, 1 ZA and 128. The bone fixation apparatus 10 can be sized to be used on cervical or lumbar vertebrae in either an anterior or posterior location. The bone focation apparatus 10 can also be sized to be used on other bone aurtaces in addition to vertebrae.
Although the present Invention has been described with refierence to its preferred embodiments, those skilled in the art will recognize changes which may be made in form or structure which do not part from the spirit of the invention already described in the specification and embodied in the claims which follow.

Claims (37)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A bone fixation apparatus, comprising:
a) an elongated plate member having a longitudinal plane, a longitudinal axis, upper and lower surfaces, apposed longitudinal side edges, at least two pairs of first circular openings and a series of second openings positioned along the longitudinal plane of the plate member, said first circular openings and said series of second openings each having a central vertical axis;
b) said first circular openings and said series of second openings each forming a cavity with walls extending between the upper and lower plate member surfaces with at least a plurality of said cavities having smaller diameter portions at the plate member upper and lower surfaces and a larger diameter portion therebetween, said cavities being configured in the shape of two inverted cones with matching base circles for allowing transverse and longitudinal angulation of an implanted bone screw;
c) a plurality of bone screws each having a threaded first end portion for implantation into a patient's bone mass and an ellipsoid shaped enlarged second end portion;
d) a locking member that connects to the second end portion of each bone screw for expanding the second end portion so as to grip the cavity wall of the plate member and for locking each bone screw into a selected position within the said first circular openings and said series of second openings of the plate member;
e) wherein the series of second opening includes a plurality of second openings having a diameter and positioned along the longitudinal plane of the plate with each second opening being connected to a next second opening by a narrow slot having a width not greater than 1/2 the diameter of the second opening which allows for controlled flexing of the plate.

2. The apparatus of claim 1, wherein the second end portion of each bone screw has a cylindrical central bore and at least two radial slits intersecting the bore, said central bore including threading on a portion of a surface of the bore.

3. The apparatus of claim 2, wherein each bone screw has four radial slits intersecting the bore.

4. The apparatus of claim 2 or 3, wherein the locking member is sized and shaped to fit into the central bore of each bone screw and has threading on a portion of a surface of the locking member for engaging the threading on the surface of the bore.

5. The apparatus of any one of claims 1 to 4, wherein said plate member has a transverse plane and is formed so as to include a curve in the transverse plane.

6. The apparatus of any one of claims 1 to 4, wherein said plate member is formed so as to include a curve in the longitudinal plane of the plate member.

7. The apparatus of any one of claims 1 to 6, wherein the plate member has a first end, a second end and a center portion with the apposed longitudinal side edges having a smaller width at the center portion in relation to a larger width at the first and second ends.

8. The apparatus of claim 7, wherein one pair of first circular openings is positioned at the first end of the plate and the second pair of first circular openings is positioned at the second end of the plate.

9. The apparatus of any one of claims 1 to 8, wherein the plurality of second openings includes circular openings with each of the plurality of second circular openings being spaced at least about 1.8 to 2.0 millimeters apart from each other.

10. The apparatus of claim 9, wherein the plurality of second circular openings includes a series of at least two spaced apart second circular openings.

11. The apparatus of claim 9, wherein the plurality of second circular openings includes a grouping of two second circular openings being connected to each other by the narrow slot.

12. The apparatus of claim 9, wherein the plurality of second circular openings includes a grouping of three second circular openings, each second circular opening being connected to the next second circular opening by the narrow slot.

13. The apparatus of claim 9, wherein the plurality of second circular openings includes a grouping of four second circular openings, each second circular opening being connected to the next second circular opening by the narrow slot.

14. The apparatus of claim 9, wherein the series of second openings includes any combination from the group consisting of two second circular openings being connected to each other by the narrow slot; three second circular openings, each second circular opening being connected to the next second circular opening by the narrow slot; and four second circular openings, each second circular opening being connected to the next second circular opening by the narrow slot.

15. The apparatus of any one of claims 1 to 14, wherein the first circular openings and series of second openings allow for transverse angulation of each of the bone screws of up to about 35° in each direction from the central vertical axis of the first circular openings and the series of second openings when each of the bone screws is inserted into each of the first circular openings and each of the series of second openings.

16. The apparatus of any one of claims 1 to 14, wherein the first circular openings and series of second openings allow for longitudinal angulation of each of the bone screws of up to about 35° in each direction from the central vertical axis of the first circular openings and the series of second openings when each of the bone screws is inserted into each of the first circular openings and each of the series of second openings.

17. The apparatus of any one of claims 1 to 16, wherein the first circular openings and series of second openings include a beveled surface on the upper and lower surfaces of the plate member.

18. The apparatus of any one of claims 1 to 17, wherein the plate member is sized to be placed on adjoining cervical vertebrae.

19. The apparatus of any one of claims 1 to 17, wherein the plate member is sized to be placed on adjoining lumbar vertebrae.

20. The apparatus of any one of claims 1 to 17, wherein the plate member is sized to be placed on an anterior side of the cervical vertebrae.

21. A bone fixation apparatus, comprising:

a) an elongated plate member having a longitudinal plane, a longitudinal axis, upper and lower surfaces, apposed longitudinal side edges, at least two pairs of first circular openings and a series of second openings positioned along the longitudinal plane of the plate member, said first circular openings and said series of second openings each having a central vertical axis;
b) said first circular openings and said series of second openings each forming a cavity with walls extending between the upper and lower plate member surfaces with at least a plurality of said cavities having smaller diameter portions at the plate member upper and lower surfaces and a larger diameter portion therebetween, said cavities being configured in the shape of two inverted cones with matching base circles for allowing transverse and longitudinal angulation of an implanted bone screw;
c) a plurality of bone screws each having a threaded first end portion adapted for implantation into a patient's bone mass and an ellipsoid shaped enlarged second end portion;
d) a locking member that connects to the second end portion of each bone screw for expanding the second end portion so as to form an interference fit between the second end portion of each bone screw and the cavity wall of a selected first circular opening or selected series of second openings of the plate member which allows each bone screw to be locked into a selected position within the said first circular opening and said series of second openings of the plate member e) wherein the series of second opening includes a plurality of second openings having a diameter and, positioned along the longitudinal plane of the plate with each second opening being connected to a next second opening by a narrow slot having a width not greater than 1/2 the diameter of the second opening which allows for controlled flexing of the plate.

22. The apparatus of claim 21, wherein the interference fit between the expanded second end portion of each bone screw and the cavity wall of the selected first circular opening or selected series of second openings of the plate member create a locking mechanism that allows for variable rigidity of the locking mechanism at each bone screw and plate member interface.

23. A bone fixation apparatus, comprising:
a) an elongated plate member having a longitudinal plane, a longitudinal axis, upper and lower surfaces, apposed longitudinal side edges, at least two pairs of first circular openings and a series of second openings positioned along the longitudinal plane of the plate member, said first circular openings and said series of second openings each having a central vertical axis;
b) said first circular openings and said series of second openings each forming a cavity with walls extending between the upper and lower plate member surfaces with at least a plurality of said cavities having smaller diameter portions at the plate member upper and lower surfaces and a larger diameter portion therebetween, said cavities being configured in the shape of two inverted cones with matching base circles for allowing transverse and longitudinal angulation of an implanted bone screw;
c) said plate member having a first end, a second end and a center portion with the apposed longitudinal side edges having a smaller width at the center portion in relation to a larger width at the first and second ends;
d) said one pair of first circular openings being positioned at the first end of the plate member and the second pair of first circular openings being positioned at the second end of the plate member;
e) wherein the series of second openings includes a plurality of second openings having a diameter and positioned along the longitudinal plane of the plate with each second opening being connected to a next second opening by a narrow slot having a width not greater than 1/2 the diameter of the second opening which allows for controlled flexing of the plate.

24. The apparatus of claim 23, wherein said plate member has a transverse plane and is formed so as to include a curve in the transverse plane.

25. The apparatus of claim 23, wherein said plate member is formed so as to include a curve in the longitudinal plane of the plate member.

26. The apparatus of any one of claims 23 to 25, wherein the plurality of second openings includes circular openings with each of the plurality of second circular openings being spaced at least about 1.8 to 2.0 millimeters apart from each other.

27. The apparatus of any one of claims 23 to 26, wherein the plurality of second circular openings includes a series of at least four spaced apart second circular openings.

28. The apparatus of any one of claims 23 to 26, wherein the plurality of second circular openings includes a grouping of two second circular openings being connected to each other by the narrow slot.

29. The apparatus of any one of claims 23 to 26, wherein the plurality of second circular openings includes a grouping of three second circular openings, each second circular opening being connected to the next second circular opening by the narrow slot.

30. The apparatus of any one of claims 23 to 26, wherein the plurality of second circular openings includes a grouping of four second circular openings, each second circular opening being connected to the next second circular opening by the narrow slot.

31. The apparatus of any one of claims 23 to 26, wherein the series of second openings includes any combination from the group consisting of two second circular openings being connected to each other by the narrow slot three second circular openings, each second circular opening being connected to the next second circular opening by the narrow slot, and four second circular openings, each second circular opening being connected to the next second circular opening by the narrow slot.

32. The apparatus of any one of claims 23 to 31, wherein the first circular openings and series of second openings allow for transverse angulation of each of the bone screws of up to about 35° in each direction from the central vertical axis of the first circular openings and the series of second openings when each of the bone screws is inserted into each of the first circular openings and each of the series of second openings.

33. The apparatus of any one of claims 23 to 31, wherein the first circular openings and series of second openings allow for longitudinal angulation of each of the bone screws of up to about 35° in each direction from the central vertical axis of the first circular opening and the series of second openings when each of the bone screws is inserted into each of the first circular openings and each of the series of second openings.

34. The apparatus of any one of claims 23 to 33, wherein the first circular openings and series of second openings include a beveled surface on the upper and lower surfaces of the plate member.

35. The apparatus of any one of claims 23 to 34, wherein the plate member is sized to be placed on adjoining cervical vertebrae.

36. The apparatus of any one of claims 23 to 34, wherein the plate member is sized to be placed on adjoining lumbar vertebrae.

37. The apparatus of any one of claims 23 to 34, wherein the plate member is sized to be placed on an anterior side of the cervical vertebrae.