An orthopedic implant system , comprising: a plate including a first surface and a second surface , the plate including at least one aperture , the aperture including one or more female threads which define a thread crest angle T1, and a thread root and at least two recesses within the threads which interrupt the threads to define at least two sections having a thread crest segment, wherein the aperture is a compound opening including an annulus having an annulus configuration and joined to a mouth in at least one of the first surface and the second surface; and at least one screw including an elongate shaft and a head member having a head configuration including male locking threads , the male locking threads of the head member defining a thread trough angle, T2, and; wherein the at least one screw is configured for insertion within at least one threaded aperture at a plurality of different insertion angles while achieving a locking engagement between the threaded head and the threaded aperture; and characterized in that : the male locking threads of the fastener head member and the female threads of the aperture having a differing thread configuration wherein T1 is different to T2; and the annulus configuration is cylindrical and the head configuration decreases in diameter along a vertical axis; or the annulus configuration decreases in diameter along a vertical axis and the head configuration decreases in diameter along a vertical axis at a different rate that the annulus configuration. a plate including a first surface and a second surface , the plate including at least one aperture , the aperture including one or more female threads which define a thread crest angle T1, and a thread root and at least two recesses within the threads which interrupt the threads to define at least two sections having a thread crest segment, wherein the aperture is a compound opening including an annulus having an annulus configuration and joined to a mouth in at least one of the first surface and the second surface; and at least one screw including an elongate shaft and a head member having a head configuration including male locking threads , the male locking threads of the head member defining a thread trough angle, T2, and; wherein the at least one screw is configured for insertion within at least one threaded aperture at a plurality of different insertion angles while achieving a locking engagement between the threaded head and the threaded aperture; and characterized in that : the male locking threads of the fastener head member and the female threads of the aperture having a differing thread configuration wherein T1 is different to T2; and the annulus configuration is cylindrical and the head configuration decreases in diameter along a vertical axis; or the annulus configuration decreases in diameter along a vertical axis and the head configuration decreases in diameter along a vertical axis at a different rate that the annulus configuration. the male locking threads of the fastener head member and the female threads of the aperture having a differing thread configuration wherein T1 is different to T2; and the annulus configuration is cylindrical and the head configuration decreases in diameter along a vertical axis; or the annulus configuration decreases in diameter along a vertical axis and the head configuration decreases in diameter along a vertical axis at a different rate that the annulus configuration. <EOS>