An orthopedic assembly comprising: a) a plate member having an upper surface and a lower surface, and an aperture extending through the upper surface and the lower surface; b) an anchor received within the aperture, the anchor comprising a head portion , a neck portion and a shank portion that form a unitary body, wherein at least a portion of the shank portion includes inner threads ; and c) a locking mechanism received within the anchor , the locking mechanism comprising a head and a shaft having outer threads, wherein the outer threads of the locking mechanism engage the inner threads of the shank portion , d) wherein the locking mechanism expands the head portion of the anchor as the locking member is downwardly inserted into the locking mechanism , thereby securing the anchor to the plate member , and wherein e) the head portion of the anchor comprises a four resilient flexible quadrants , f) each of the quadrants including an inner relief formed along an inner surface thereof providing a region in which the head portion of the locking mechanism is designed to contact and nest within the anchor , g) so that when the head of the locking mechanism is inserted into the anchor , the head of the locking mechanism causes outward expansion of the head portion of the anchor as the locking member is downwardly inserted into the locking mechanism , thereby securing the anchor to the plate member ; h) and then upon further downward insertion of the locking mechanism once the head of the locking mechanism is nested and positioned within the inner reliefs , the resilient quadrants of the head portion of the anchor retract radially inward to tighten and capture the locking mechanism within the anchor . a) a plate member having an upper surface and a lower surface, and an aperture extending through the upper surface and the lower surface; b) an anchor received within the aperture, the anchor comprising a head portion , a neck portion and a shank portion that form a unitary body, wherein at least a portion of the shank portion includes inner threads ; and c) a locking mechanism received within the anchor , the locking mechanism comprising a head and a shaft having outer threads, wherein the outer threads of the locking mechanism engage the inner threads of the shank portion , d) wherein the locking mechanism expands the head portion of the anchor as the locking member is downwardly inserted into the locking mechanism , thereby securing the anchor to the plate member , and wherein e) the head portion of the anchor comprises a four resilient flexible quadrants , f) each of the quadrants including an inner relief formed along an inner surface thereof providing a region in which the head portion of the locking mechanism is designed to contact and nest within the anchor , g) so that when the head of the locking mechanism is inserted into the anchor , the head of the locking mechanism causes outward expansion of the head portion of the anchor as the locking member is downwardly inserted into the locking mechanism , thereby securing the anchor to the plate member ; h) and then upon further downward insertion of the locking mechanism once the head of the locking mechanism is nested and positioned within the inner reliefs , the resilient quadrants of the head portion of the anchor retract radially inward to tighten and capture the locking mechanism within the anchor . <EOS>