Bone plate apparatus

Abstract: Bone plate apparatus comprises a plate having a superior surface, and inferior surface, a slot extending between the superior and inferior surfaces, and a rim extending around the slot. The rim includes an interrupted surface. A fastener includes a shaft which can extend into the bone. A collar is coupled to the shaft and a head is coupled to the collar for movement in the slot. The collar includes an interrupted surface which can mate with the interrupted surface of the slot rim. A nut cooperates with the head of the fastener to couple the interrupted surfaces of the fastener and rim together, and to lock the head in a fixed position within the slot.

Description: The present invention relates to bone plates, more particularly the present invention relates to bone plates that apply compressive stress over a fracture. Most particularly, the present invention relates to bone plates that provide incremental compressive stress over a fracture. Fasteners that thread into the vertebra are known, such fasteners, their structures and the manner in which they are used are taught in US-4696290, US-4854311, US-5613967 and US-5261910. FR-A-2692775 discloses a bone plate assembly corresponding to the preamble of claim 1 in which the bone plate itself has a plurality of openings extending through it, and a ribbed surface. The plate is used with the ribbed surface facing away from the surface of the bone which is damaged. Bone screws and cooperating nuts and washers are used to fasten the plate to the bone. Each washer has a rib on the surface which contacts the plate and is held in place against the plate surface by means of its respective screw, which extends through an opening in the plate into the bone. The present invention provides bone plate apparatus which comprises: a plate including a superior surface, and an inferior surface to face the damaged bone when the apparatus is in use, a slot extending between the superior and inferior surfaces, and a rim extending about the slot on the inferior surface of the plate, the rim including an interrupted surface, a fastener including a shaft formed for extension into the bone, a collar coupled to the shaft, and a head coupled to the collar for movement in the slot, the collar including an interrupted surface, the interrupted surface of the collar being formed to mate with the interrupted surface of the rim of the slot, and a nut formed to cooperate with the head of the fastener to couple the interrupted surfaces of the collar and rim together and lock the head in a fixed position within the slot. The bone plate in the apparatus of the invention can be prevented from moving relative to the vertebrae and the fasteners. The apparatus can therefore be used to preload or to provide incremental compressive stress over a fracture to aid in fusion. In preferred embodiments, there can be a plurality of slots. The or each slot can include a first end and a second end, with the or each rim extending between the first and second ends. Each rim includes opposite ends adjacent to the first and second ends of the slots and side walls that extend between the opposite ends of the rim. The interrupted surface is formed on each of the side walls of the rim to mate with the interrupted surface formed on the collar of the fastener. The interruptions on the plate and fastener are preferably teeth that have a width of about 1 mm. In addition to spaced apart teeth providing the interruptions, it will be apparent that the interruptions made take the form of spaced apart bumps or indents that mate with corresponding spaced apart recesses. Accordingly, the term "interruptions" is intended to refer to spaced apart elements or recessed on the slots that mate or mesh with spaced apart elements or recesses on the fastener or locking device for fastener. Therefore, according to the present invention a spinal plate assembly is provided that includes a plate having at least two elongated slots, a threaded fastener to extend through each slot into the spine, and a locking device to engage each fastener to hold it in a selected position in its slot. Each slot is formed with interruptions spaced along its length. In addition, cooperating interruptions are formed on the fastener or the locking device to mate with the slot's interruptions selectively to position the plate relative to the fastener. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a bone plate apparatus as it would appear to a surgeon during attachment of the apparatus to a vertebrae of a patient, showing the apparatus including a bone plate formed to include spaced-apart slots and fasteners extending through the slots; Fig. 2 is a perspective view of a bone plate of Fig. 1 showing the plate including a superior surface having opposite ends, the slots extending through the superior surface adjacent to the opposite ends, and elongated openings positioned to lie between the spaced-apart slots; Fig. 3 is a bottom view of the bone plate of Fig. 2 showing an inferior surface of the plate and rims extending about each of the slots, the rims including teeth thereon; Fig. 4 is a view taken along lines 4-4 of Fig. 1 showing the fastener including a threaded shaft extending into the vertebrae, a threaded head extending from the slot and coupled to a nut, and a collar positioned to lie between the shaft and the head and engaging the rim of the slot; Fig. 5 is an exploded assembly view of the apparatus of Fig. 1 showing the collar including teeth that correspond with the teeth formed in the rim of the slot and showing an end screw that is formed for extension into a cavity formed in fastener once the surgeon has coupled the bone plate to the vertebrae; Fig. 6 is a view taken along lines 6-6 of Fig. 4 showing the lock teeth of the collar engaging the teeth of the rim to hold the bold in a selected position on the bone plate; Fig. 7 is an exploded assembly view of a bone plate apparatus in accordance with the present invention, showing the apparatus including a bone plate having an inferior surface formed to include a slot and a rim extending about the circumference of the slot and including apertures therein, a fastener including a threaded shaft, a threaded head, and a collar positioned to lie between the shaft and the head, the collar including protrusions thereon that correspond to the apertures formed on the rim, a nut formed to engage the threaded head of the fastener, and an end screw formed for extension through the nut and into a cavity formed in the head of the fastener; and Fig. 8 is a cross-sectional view of the apparatus of Fig. 7 showing the threaded shaft extending into the vertebrae, the threaded head extending from the slot and coupled to a nut, and protrusions on the collar engaging the apertures formed on the rim of the slot. Referring to the drawings, Fig. 1 shows a bone plate apparatus 10 is provided in accordance with the present invention. Apparatus 10 preloads or provides incremental compressive stress in fine increments of at least about 1 mm over a fracture in a vertebra 12 to aid in fusion. It is appreciated that apparatus 10 preloads or provides incremental compression in fine increments over a graft in a vertebrectomy or corpectomy. Apparatus 10 includes a bone plate 14 configured to engage vertebrae 12, fasteners 16 extending through bone plate 14 into vertebrae 12, corresponding locking devices, such as nuts 18, and end screws 19 formed to engage fasteners 16. Referring now to Figs. 2 and 3, the bone plate 14 includes a superior surface 20, an inferior surface 22, and an edge 23 extending between superior and inferior surfaces 20, 22. In addition, the bone plate 14 includes opposite plate ends 24, 26 and a middle portion 28 positioned to lie between ends 24, 26. Slots 30, 32 are formed in bone plate 14 adjacent to ends 24, 26 respectively. Bone plate 14 further includes apertures 46, 48 positioned to lie adjacent to slot 30 and an aperture 50 positioned to lie adjacent to slot 32. Apertures 46, 48, 50 are sized to receive lock screws (not shown) once bone plate 14 has been coupled to vertebrae 12 by fasteners 16. In addition, elongated openings 52, 54 are formed through bone plate 14 and are positioned to lie adjacent to middle portion 28 between slots 30, 32. Elongated openings 52, 54 are formed to receive a handle (not shown) that is used to move bone plate 14 from one location to another. It is appreciated may be formed to include any number of apertures in a variety of locations to receive a handle or other gripping apparatuses suitable for carrying bone plate 14 from one location to another. As best shown in Fig. 3, slots 30, 32 are formed through bone plate 14 in general alignment with one another. Slots 30, 32 include a first end 34 and a second end 36 adjacent to respective ends 24, 26 of bone plate 14. Bone plate 14 further includes a tapered rim 38 extending about each slot 30, 32. While one rim 38 and slot 30 are illustrated and will be described hereafter it is understood that the description applies equally to both rims 38 and to slot 32. Rim 38 includes opposite ends 40, 42 adjacent to first and second ends 34, 36 of slot 30 and side walls 44 extending between ends 40, 42. Side walls 44 are each formed to include an interrupted surface 45. Surface 45 is interrupted by teeth 56 extending away from inferior surface 20. The width of teeth is about 1 mm. It is appreciated that the size and number of teeth may vary in accordance with the present disclosure. Fasteners 16 are sized for extension through slots 30, 32. One fastener 16 is shown in Figs. 4 to 6, but it is appreciated that the following description applies to both fasteners. Fastener 16 includes a shaft 58 having threads 60, a collar 62 coupled to a superior end 64 of shaft 54, and a head 66 extending from collar 58. As shown in Fig. 5, head 66 is formed to include an exterior surface 67 that includes opposing sides 68 and opposite curved ends 71 that extend between sides 68. Sides 68 are generally flat and face side walls 44 of tapered rim 38 to permit head 66 to extend into slot 30 and slide between first and second ends 34, 36 of slot 30, as shown by arrows 69 in Fig. 6. Sides 68 are also formed to interact with side walls 44 of rim 38 to prevent fastener 16 rotating in slot 30 and backing out of slot 30. Ends 71 face first and second ends 34, 36 of slot 30 and include threads 70 that correspond with threads 72 formed on an interior surface 74 of nut 18. Head 66 also includes an interior surface 76 that includes threads 78 thereon and defines a cavity 80. Cavity 80 is sized to receive an end screw 19. Collar 62 of fastener 16 includes a seat portion 82 that has a first end 84 adjacent to head 66, an opposite second end 86 spaced-apart from first end 84, and a centre portion 88 positioned between ends 84, 86. Collar 62 also includes an edge 90 that extends from second end 86 of seat portion 82. See Fig. 5. Centre portion 88 includes an interrupted surface 89 that is formed to mate with interrupted surface 45 of rim 28. Surface 89 is interrupted by teeth 92 that extend from centre portion 88 between first and second ends 84, 86 to cooperate with teeth 56 of tapered rim 38 to lock fastener 16 in a fixed position within slot 30. Illustratively, three teeth 92 extend from centre portion 88 of collar 62 adjacent to each side 68 of head 66. Each tooth 92 has a width of about 1 mm. It is appreciated that the size of teeth may vary and that greater or fewer than three teeth may be used in accordance with the disclosure to lock fastener 16 within slot 30. Thus, due to the interaction between teeth 56, 92, the number of fastener positions within slot 30 is limited by only the tooth 56, 92 width and the length of slot 30. As shown in Fig. 5, end screw 19 is formed to include a shaft 102 sized for extension into cavity 80 of head 66 and an end cap 103 that engages nut 18. Shaft 102 is formed to include threads 104 that extend in a direction opposite than that of threads 70 of head 66. Therefore, if nut 18 should begin to rotate on head 66 in a nut disengagement direction away from bone plate 14, such rotation would serve to rotate end screw 19 in a screw engagement direction toward bone plate 14. Thus, end screws 19 act to block disengagement of nuts 18 from fasteners 16. In use, the surgeon insets shaft 58 of each of the fasteners 16 into preformed apertures 94 in vertebrae 12 so that edge 90 of collar 62 engages an upper surface 96 of vertebrae 12. See Fig. 4. Referring now to Fig. 1, fasteners 16 are aligned in vertebrae 12 so that sides 68 are positioned to face anterior and posterior sides 98, 100 of vertebrae 12. Bone plate 14 is then placed upon upper surface 96 of vertebrae 12 so that heads 66 of fasteners 16 extend through respective slots 30, 32 and teeth 56 of rim 38 engage teeth 92 of collar 62. As shown in Fig. 5, when head 66 is placed through slot 30, sides 68 face side walls 44 of tapered rim 38. The surgeon is free to slide bone plate 14 relative to fasteners 16, such that fasteners 16 move between first end 34 and second end 36 of respective slots 30, 32. Once the surgeon has selected a desirable position for bone plate 14 on fasteners 16, nuts 18 are threaded upon heads 66 of respective fasteners 16, as shown in Fig. 6. As nuts 18 are tightened on heads 66, teeth 56 of rim 38 are pressed between teeth 92 of collar 62. Once nuts 18 have locked teeth 56, 92 together, heads 66 of fasteners 16 are locked in a fixed position within slots 30, 32 and bone plate 14 is held in a fixed position on vertebrae 12. End screw 19 is then inserted into cavity 80 of head 66 and rotated until cap 103 engages nut 18. Referring now to Fig. 7, a bone plate apparatus 110 is provided in accordance with the present invention. Apparatus 110 preloads or provides incremental compressive stress in fine increments over a fracture in a vertebra 12 to aid in fusion. Apparatus 110 includes a bone plate 114 configured to engage vertebrae 12, fasteners 116 extending through bone plate 114 into vertebrae 12, corresponding nuts 18, and end screws 19 formed to engage fasteners 116. Bone plate 114 is formed in a manner similar to bone plate 14 and like reference numerals will be used to denote like components. Bone plate 114 includes a tapered rim 138 extending about slot 30 on inferior surface 22. Only one tapered rim 138 is shown in Figs. 7 and 8, but it is appreciated that the following description applies to a rim that surrounds slot 32 in bone plate 114. Rim 138 includes opposite ends 140, 142 adjacent to first and second ends 34, 36 of slot 30 and side walls 144 extending between ends 140, 142. Side walls 144 each include an interrupted surface 145. Surface 145 is interrupted by a series of apertures 156. Fastener 116 is sized for extension through slot 30. Fastener 116 is formed in a manner similar to fastener 16 and like reference numerals will be used to denote like components. One fastener 116 is shown in Figs. 7 and 8, but it is appreciated that the following description applies to any number of fasteners suitable for use with bone plate 114. Fastener 116 includes a collar 162 coupled to superior end 64 of shaft 54. Head 66 extends from collar 162. Collar 162 includes a seat portion 182 and an edge 190 that extends away from seat portion 182. As shown in Fig. 7, seat portion 182 has a first end 184 adjacent to head 66, an opposite second end 186 spaced-apart from first end 184 adjacent to edge 190, and a centre portion 188 positioned between ends 184, 186. Centre portion 188 of seat portion 182 includes an interrupted surface 189. Surface 189 is interrupted by protrusions 192 that extend from centre portion 188 to cooperate with apertures 156 of tapered rim 138 to lock fastener 116 in a fixed position within slot 30. It is appreciated rim 138 could include protrusions and collar 162 could include apertures in accordance with the present disclosure. For example, one protrusion 192 extends from centre portion 188 of collar 162 adjacent to each wall 68 of head 66. It is appreciated that the size of protrusions 192 and apertures 156 may vary and that greater than one protrusion 192 may be used in accordance with the disclosure to lock fastener 116 within slot 30. Thus, due to the interaction between apertures and protrusions 156, 192, the number of fastener positions within slot 30 is limited by only the protrusion width and the length of slot 30. In use, the surgeon insets shaft 58 of each fastener 116 into preformed apertures 94 in vertebrae 12 so that edge 190 of collar 162 engages an upper surface 96 of vertebrae 12. See Fig. 8. Similar to fasteners 16, fasteners 116 are aligned in vertebrae 12 so that walls 68 are positioned to face anterior and posterior sides 98, 100 of vertebrae 12. Bone plate 114 is then placed upon upper surface 96 of vertebrae 12 so that heads 66 of fasteners 16 extend through respective slots 30, 32 and apertures of rim 138 receive protrusions 192 of collar 162. As shown in Fig. 8, when head 66 is placed through slot 30, walls 68 face side walls 144 of tapered rim 138. The surgeon is free to slide bone plate 114 relative to fasteners 116, such that fasteners 116 move between first end 34 and second end 36 of respective slots 30, 32. Once the surgeon has selected a desirable position for bone plate 114 on fasteners 116, nuts 18 are threaded upon heads 66 of respective fasteners 116, as shown in Fig. 8. As nuts 18 are tightened on heads 66, protrusion 192 of collar 162 is pressed into one of the apertures 156 in rim 138. Once nuts 18 have locked protrusion 192 in aperture 156, heads 66 of fasteners 116 are locked in a fixed position within slots 30, 32 and bone plate 114 is held in a fixed position on vertebrae 12. End screw 19 is then inserted into cavity 80 of head 66 and rotated until cap 103 engages nut 18. Interrupted surfaces of the present disclosure are not limited to the teeth and the protrusion and aperture illustrated in Figs. 1 to 8. It is appreciated that the interruptions may be any number of detents, stops, tabs, and the like that serve to lock the fastener in a fixed position within the slot. According to the present invention, the interrupted surface of the fastener or locking device mates with the interrupted surface of the plate to lock the fastener in a fixed position within the slot. Thus, the number of fixed fastener positions within slot 30 is limited by only the width of the interruptions and the length of slot 30.

Claims: Bone plate apparatus comprising: a plate (14) including a superior surface (20), and an inferior surface (22) to face the damaged bone (12) when the apparatus is in use, a slot (30, 32) extending between the superior and inferior surfaces, and a rim (38) extending about the slot, the rim including an interrupted surface (45), a fastener (16) including a shaft (58) formed for extension into the bone, a collar (62) coupled to the shaft, and a head (66) coupled to the collar for movement in the slot, the collar including an interrupted surface (89), the interrupted surface of the collar being formed to mate with the interrupted surface of the rim of the slot, and a nut (18) formed to cooperate with the head of the fastener to couple the interrupted surfaces of the collar and rim together and lock the head in a fixed position within the slot, characterised in that the rim (38) in on the inferior surface of the plate. Apparatus as claimed in claim 1, in which interrupted surface (45) of the rim (38) includes teeth (56). Apparatus as claimed in claim 2, in which the teeth (56) each have a width of about 1 mm. Apparatus as claimed in claim 2, in which the interrupted surface (89) of the collar (62) includes teeth (92). Apparatus as claimed in claim 4, in which the teeth (92) on the interrupted surface (89) of the collar (62) have a width of about 1 mm. Apparatus as claimed in claim 1, in which the interrupted surface (45) of the rim (38) includes apertures formed therein. Apparatus as claimed in claim 1, in which the rim (38) includes opposite ends (40, 42) and side walls (44) extending between the ends and the interrupted surface (45) is formed on each of the side walls. Apparatus as claimed in claim 7, in which the head (66) of the fastener (16) has generally flat walls (68) facing the side walls of the rim. Apparatus as claimed in claim 8, in which the head of the fastener includes curved walls (71) extending between the generally flat walls, the curved walls including threads (70) that cooperate with the nut (18). Apparatus as claimed in claim 1, in which the plate (14) has a plurality of the said slots (30, 32) extending between the superior and inferior surfaces thereof. Apparatus as claimed in claim 1, in which the interrupted surface (89) of the collar (62) is tapered.

Inventors: BONO FRANK S, BONO, FRANK S.
Applicants: DEPUY ACROMED INC, DEPUY ACROMED, INC.
Application year: 1999
Main classification: A61B17
IPC codes: A61F2, A61B17