Patent ID: 7887547
Filing Date: 2011-02-15
Classification: A61B,A61F

Abstract:
1. A bone plate system comprising a plate of the type having at least one at least part spherical bores therein for receiving a screw, the screw having a drive head at a first end and a threaded shank at a second end, the part spherical bore extending along an axis from an outer surface to a bone contacting surface of said plate, the part spherical bore having a maximum diameter with respect to the axis including a recessed groove with a larger diameter than said maximum diameter, the screw drive head having a ring contacting outer surface facing the outer plate surface and having a diameter less than said maximum diameter, an expandable ring mounted in the groove and having a relaxed unexpanded inner diameter less than the screw head diameter, the ring capable of expanding in the groove on contacting the screw head, so that when the internal ring diameter expands to at least the screw head diameter so that said screw head can pass through the ring such that the screw can be located in the bone with the drive head ring contacting outer surface located closer to the plate bone contacting surface than a screw head contact surface of the ring and a tool for removing the screw, said tool comprising, a drive shaft with tip for engaging the drive head of the screw, the tip having a cruciform blade having spaced cross members and an inwardly chamfered lead portion for engaging the relaxed internal diameter of said ring and expanding the ring into the groove to open the ring at least to the screw head diameter so that said screw head may be backed out of the bore, wherein said drive shaft is cannulated along its entire length wherein said screw includes a threaded bore open to the first screw end alignable with said cannulation in said drive shaft and further comprising a screw puller having a shaft with a threaded tip, the screw puller shaft and threaded tip being slidably received in said cannulated drive shaft with the threaded tip extending from an end of the drive shaft for engaging the thread in said screw, the threaded tip having a major diameter less than a diameter of the cannulation in the drive shaft.