초록 ▼

A locking screw assembly is provided which allows installation into a plate-like member using relatively little force, but which requires relatively great force for removal. The fastener has an annular locking ring provided within a groove in the head of the screw to allow the screw to sit within or

A locking screw assembly is provided which allows installation into a plate-like member using relatively little force, but which requires relatively great force for removal. The fastener has an annular locking ring provided within a groove in the head of the screw to allow the screw to sit within or flush with the anterior surface of the plate. The through-hole in the plate which receives the locking screw comprises an entrance, a collar section, an undercut, and an exit. The locking ring resides within the undercut. The locking ring has a leading surface that is chamfered or radiused and a trailing surface that is flat. The chamfer allows the locking ring to easily be inserted into the through-hole by interacting with a lead chamfer in the entrance. After installation, the flat trailing surface abuts a lip adjoining the collar section and the undercut and prevents the screw from being easily removed from the through-hole.

대표청구항 ▼

What is claimed is: 1. A system for locking a fastener to a plate comprising: a) a locking fastener having a proximal end and a distal end, further comprising (i) a head having an upper region, a groove adjacent said upper region, and a lower region adjacent said groove; wherein said upper region h

What is claimed is: 1. A system for locking a fastener to a plate comprising: a) a locking fastener having a proximal end and a distal end, further comprising (i) a head having an upper region, a groove adjacent said upper region, and a lower region adjacent said groove; wherein said upper region has a first diameter at said proximal end of said locking fastener and a second diameter adjacent said groove, and wherein said lower region has a third diameter adjacent said groove and a fourth diameter at a distal end of said lower region; (ii) a shank having a proximal end and a distal end, wherein said proximal end of said shank is adjacent said lower region of said head, and wherein said distal end of said shank further comprises a shoulder; (iii) a threaded section adjacent said shank; and (iv) a locking ring having an outer diameter and an inner diameter and a leading surface and a trailing surface, wherein said leading surface further comprises a chamfer, and wherein said locking ring resides within said groove of said head; and b) a plate further comprising an anterior surface and a posterior surface, wherein said plate further comprises a through-hole through said anterior surface and said posterior surface, said through-hole having associated therewith an imaginary longitudinal axis through the centroid of said through-hole; and wherein said through-hole comprises an undercut having a proximal end and a distal end, said through-hole further comprising a first lip located proximally of said proximal end of said undercut and a second lip located distally of said distal end of said undercut. 2. The system for locking a fastener to a plate according to claim 1 wherein said through-hole further comprises an entrance having a proximal end and a distal end; a collar section adjacent said entrance having a proximal end and a distal end; an undercut adjacent said collar section having a proximal end and a distal end; and an exit located distally of said undercut and having a proximal end and a distal end, said exit further comprising an exit diameter. 3. The system for locking a fastener to a plate according to claim 2 wherein said proximal end of said entrance is coplanar with said anterior surface of said plate. 4. The system for locking a fastener to a plate according to claim 3 wherein said distal end of said entrance is adjacent said proximal end of said collar section. 5. The system for locking a fastener to a plate according to claim 4 wherein said distal end of said collar section is adjacent said proximal end of said undercut. 6. The system for locking a fastener to a plate according to claim 5 wherein said distal end of said exit is adjacent said proximal end of said shank. 7. The system for locking a fastener to a plate according to claim 6 wherein said entrance further comprises a first diameter at said proximal end of said entrance and a second diameter at said distal end of said entrance, wherein said first diameter is greater than said second diameter. 8. The system for locking a fastener to a plate according to claim 7 wherein said collar section further comprises a third diameter, wherein said third diameter is equal to said second diameter of said entrance. 9. The system for locking a fastener to a plate according to claim 8 wherein said undercut further comprises a fourth diameter, wherein said fourth diameter of said undercut is greater than said third diameter of said collar section. 10. The system for locking a fastener to a plate according to claim 9 wherein said distal end of said collar section meets with said proximal end of said undercut at said first-lip. 11. The system for locking a fastener to a plate according to claim 10 wherein said through-hole further comprises a ramp adjacent said distal end of said undercut, and having a proximal end and a distal end, said ramp having a fifth diameter at said proximal end of said ramp and a sixth diameter at said distal end of said ramp, wherein said fifth diameter is greater than said sixth diameter. 12. The system for locking a fastener to a plate according to claim 11 wherein said first diameter of said upper region of said head is equal to said second diameter of said upper region of said head, and wherein said third diameter of said lower region of said head is equal to said fourth diameter of said lower region of said head, and wherein said shank has a diameter approximately equal to said exit diameter of said exit, and wherein said exit receives said shank of said locking fastener so that said locking fastener cannot angulate about said longitudinal axis. 13. The system for locking a fastener to a plate according to claim 11 wherein said first diameter of said upper region of said head is less than said second diameter of said upper region of said head, and wherein said third diameter of said lower region of said head is greater than said fourth diameter of said lower region of said head, and wherein said exit receives said shank of said locking fastener such that said locking fastener can angulate about said longitudinal axis of said through-hole. 14. In combination with a plate having a through-hole therein, wherein said through-hole further comprises an entrance having a proximal end and a distal end, a collar section adjacent said distal end of said entrance having a proximal end and a distal end, an undercut adjacent said distal end of said collar section having a proximal end and a distal end, wherein a substantially horizontal lip is present in said through-hole adjacent said proximal end of said undercut, a ramp adjacent said distal end of said undercut having a proximal end and a distal end, and an exit adjacent said distal end of said ramp; a locking fastener comprising: a) a head having an upper region, a groove, and a lower region, wherein said upper region has a proximal end and a distal end and wherein said upper region has a first diameter at said proximal end and a second diameter at said distal end; and wherein said lower region has a third diameter at a proximal end thereof and a fourth diameter at a distal end thereof, wherein said groove is located between said upper region and said lower region; b) a shank having a proximal end and a distal end, wherein said proximal end of said shank is adjacent said distal end of said lower region of said head; c) a threaded section having a proximal end and a distal end, wherein said proximal end of said threaded section is adjacent said distal end of said shank; and d) an annular cylindrical locking ring having an outer diameter and an inner diameter and a leading surface and a trailing surface, wherein said leading surface further comprises a chamfer thereon, and wherein said locking ring resides within said groove of said head. 15. The combination of claim 14 wherein said groove has a diameter that is less than said second diameter of said upper region of said head and less than said third diameter of said lower region of said head. 16. The combination of claim 15 wherein said outer diameter of said locking ring is greater than said second diameter of said upper region of said head and greater than said third diameter of said lower region of said head. 17. The combination of claim 16 wherein said inner diameter of said locking ring is less than said third diameter of said lower region of said head. 18. The combination of claim 17 wherein said inner diameter of said locking ring is elastically deformable between a first position and a second position, wherein said first position is a normal resting state and wherein in said second position said inner diameter of said locking ring is equal to said third diameter of said lower region of said head. 19. The combination of claim 14 wherein said first diameter of said upper region of said head is equal to said second diameter of said upper region of said head, and wherein said third diameter of said lower region of said head is equal to said fourth diameter of said lower region of said head. 20. The combination of claim 19 wherein said upper region of said head and said lower region of said head each comprise an outer surface that is cylindrical. 21. The combination of claim 20 wherein said distal end of said shank is inserted into said exit of said through-hole such that angulation of said locking fastener is prevented. 22. The combination of claim 14 wherein said first diameter of said upper region of said head is less than said second diameter of said upper region of said head, and wherein said third diameter of said lower region of said head is greater than said fourth diameter of said lower region of said head. 23. The combination of claim 22 wherein said upper region of said head and said lower region of said head each comprise an outer surface that is a portion of a sphere. 24. The combination of claim 23 wherein said distal end of said shank interacts with said exit of said through-hole such that angulation of said locking fastener about said longitudinal axis is possible. 25. A method of retaining a fastener within a plate, wherein the method comprises: a) providing a fastener further comprising a head having a groove therein, a shank adjacent said head, and a threaded section adjacent said shank; b) providing a plate further comprising a through-hole having an entrance, a collar section, an undercut, a ramp, and an exit; wherein said undercut has a diameter greater than a diameter of said collar section; c) installing a locking ring having a trailing surface and a leading surface on said screw by inserting said screw first through said trailing surface of said locking ring and progressing said screw through said locking ring until said locking ring surpasses said first diameter of said lower section of said head; d) attaching said screw to a driving instrument; e) installing said screw in said plate using said driving instrument; f) rotatably engaging said threads of said screw into a bone structure until said locking ring in said head snaps into said undercut of said through-hole; and g) removing said driving instrument from said screw.