A separable surgical guide instrument comprising: a guide body that defines a proximal end and a distal end spaced from the proximal end along a longitudinal direction, the separable surgical guide instrument further defining a guide aperture that extends through the guide body from the proximal end to the distal end, wherein the distal end includes a first distal end portion and a second distal end portion that are arranged such that at least one of the first and second distal end portions (42a, 42b) is movable with respect to the other of the first and second distal end portions (42a, 42b) between 1) a closed position whereby the first and second distal end portions (42a, 42b) are concurrently insertable into a bone fixation aperture of a bone plate, and 2) an open position whereby the first distal end portion is spaced from the second distal end portion a sufficient distance such that the first and second distal end portions (42a, 42b) are not concurrently insertable into the bone fixation aperture, wherein, when the first and second distal end portions (42a, 42b) are in the open position, a bone anchor having a threaded head is drivable through the guide aperture along the longitudinal direction from the proximal end to the distal end, and out the distal end such that the threaded head threadedly purchases with the bone plate in the bone fixation aperture, characterized in that the first distal end portion defines at least one first thread segment at an outer surface, the second distal end portion defines at least one second thread segment at an outer surface, and when the first and second distal end portions (42a, 42b) are in the closed position, the first and second thread segments (50, 52) are aligned along a common helix and configured to threadedly purchase with the bone plate in the bone fixation aperture. a guide body that defines a proximal end and a distal end spaced from the proximal end along a longitudinal direction, the separable surgical guide instrument further defining a guide aperture that extends through the guide body from the proximal end to the distal end, wherein the distal end includes a first distal end portion and a second distal end portion that are arranged such that at least one of the first and second distal end portions (42a, 42b) is movable with respect to the other of the first and second distal end portions (42a, 42b) between 1) a closed position whereby the first and second distal end portions (42a, 42b) are concurrently insertable into a bone fixation aperture of a bone plate, and 2) an open position whereby the first distal end portion is spaced from the second distal end portion a sufficient distance such that the first and second distal end portions (42a, 42b) are not concurrently insertable into the bone fixation aperture, wherein, when the first and second distal end portions (42a, 42b) are in the open position, a bone anchor having a threaded head is drivable through the guide aperture along the longitudinal direction from the proximal end to the distal end, and out the distal end such that the threaded head threadedly purchases with the bone plate in the bone fixation aperture, characterized in that the first distal end portion defines at least one first thread segment at an outer surface, the second distal end portion defines at least one second thread segment at an outer surface, and when the first and second distal end portions (42a, 42b) are in the closed position, the first and second thread segments (50, 52) are aligned along a common helix and configured to threadedly purchase with the bone plate in the bone fixation aperture.