Abstract: A bone plate is formed with a throughgoing hole formed with a radially inwardly open outer groove. A screw fastener has a shaft engageable coaxially through the hole and a head of larger diameter than the shaft and adapted to bear axially on the plate around the hole. The shaft is formed offset from the head with a radially outwardly projecting ridge defining a radially outwardly open inner groove aligned radially with the outer groove when the fastener is fitted through the hole with the head bearing on the plate. An elastically deformable ring of a diameter generally equal to that of the hole at the outer groove is formed with at least one radially inwardly directed projection that, when the ring is fitted to the outer groove and the fastener is seated in the hole, projects radially inward into the inner groove of the fastener.

Abstract: A bone plate is formed with a throughgoing hole formed with a radially inwardly open outer groove. A screw fastener has a shaft engageable coaxially through the hole and a head of larger diameter than the shaft and adapted to bear axially on the plate around the hole. The shaft is formed offset from the head with a radially outwardly projecting ridge defining a radially outwardly open inner groove aligned radially with the outer groove when the fastener is fitted through the hole with the head bearing on the plate. An elastically deformable ring of a diameter generally equal to that of the hole at the outer groove is formed with at least one radially inwardly directed projection that, when the ring is fitted to the outer groove and the fastener is seated in the hole, projects radially inward into the inner groove of the fastener.

Abstract: A spinal-column distractor (10) comprises a first pusher plate (1) intended to bear on a vertebra, a second pusher plate (2) intended to bear on an adjacent vertebra, and a slide (3). The slide (3) is connected to the first pusher plate (1) via a scissor linkage (4), and shiftable by a threaded spindle to change a spacing between the first pusher plate (1) and the second pusher plate (2), while the second pusher plate (2) forms a track for the slide (3).

Abstract: A spinal-column distractor (10) comprises a first pusher plate (1) intended to bear on a vertebra, a second pusher plate (2) intended to bear on an adjacent vertebra, and a slide (3). The slide (3) is connected to the first pusher plate (1) via a scissor linkage (4), and shiftable by a threaded spindle to change a spacing between the first pusher plate (1) and the second pusher plate (2), while the second pusher plate (2) forms a track for the slide (3).