A robotically-assisted handholdable guide instrument (14, 14') for aligning a trajectory of a surgical device, the instrument comprising: a hand-holdable body (16, 16', 72, 72', 74, 74') adapted to be freely holdable and moved by a hand of a user; and a trajectory assembly (18, 18') operatively connected with the hand-holdable body (16, 16', 72, 72', 74, 74'), the trajectory assembly (18, 18') including: a shaft (76, 76') extending from the hand-holdable body (16, 16', 72, 72', 74, 74'); a pivot frame (26, 26') coupled with the shaft (76, 76'); a guide member (20, 20') pivotally connected with the pivot frame (26, 26'); a support member (80, 80') outwardly extending from and connected with the guide member (20, 20'); two actuators (21, 21', 22, 22') coextending and substantially parallel to an axis of the shaft (76, 76'), each actuator (21, 21', 22, 22') pivotally connected with the support member (80, 80'); wherein the trajectory assembly (18, 18') converts linear movement of the actuators (21, 21', 22, 22') into pivotal movement of the guide member (20, 20') to adjust a trajectory axis, the actuators (21, 21', 22, 22') selectively configured to push and pull the support member (80, 80') connected with the guide member (20, 20'); and wherein the guide member (20, 20') is adjustable to a target trajectory with the actuators (21, 21', 22, 22'), adjusting the trajectory axis of the guide member (20, 20') in at least two degrees of freedom to align the trajectory axis with the target trajectory. a hand-holdable body (16, 16', 72, 72', 74, 74') adapted to be freely holdable and moved by a hand of a user; and a trajectory assembly (18, 18') operatively connected with the hand-holdable body (16, 16', 72, 72', 74, 74'), the trajectory assembly (18, 18') including: a shaft (76, 76') extending from the hand-holdable body (16, 16', 72, 72', 74, 74'); a pivot frame (26, 26') coupled with the shaft (76, 76'); a guide member (20, 20') pivotally connected with the pivot frame (26, 26'); a support member (80, 80') outwardly extending from and connected with the guide member (20, 20'); two actuators (21, 21', 22, 22') coextending and substantially parallel to an axis of the shaft (76, 76'), each actuator (21, 21', 22, 22') pivotally connected with the support member (80, 80'); wherein the trajectory assembly (18, 18') converts linear movement of the actuators (21, 21', 22, 22') into pivotal movement of the guide member (20, 20') to adjust a trajectory axis, the actuators (21, 21', 22, 22') selectively configured to push and pull the support member (80, 80') connected with the guide member (20, 20'); and wherein the guide member (20, 20') is adjustable to a target trajectory with the actuators (21, 21', 22, 22'), adjusting the trajectory axis of the guide member (20, 20') in at least two degrees of freedom to align the trajectory axis with the target trajectory. a shaft (76, 76') extending from the hand-holdable body (16, 16', 72, 72', 74, 74'); a pivot frame (26, 26') coupled with the shaft (76, 76'); a guide member (20, 20') pivotally connected with the pivot frame (26, 26'); a support member (80, 80') outwardly extending from and connected with the guide member (20, 20'); two actuators (21, 21', 22, 22') coextending and substantially parallel to an axis of the shaft (76, 76'), each actuator (21, 21', 22, 22') pivotally connected with the support member (80, 80'); wherein the trajectory assembly (18, 18') converts linear movement of the actuators (21, 21', 22, 22') into pivotal movement of the guide member (20, 20') to adjust a trajectory axis, the actuators (21, 21', 22, 22') selectively configured to push and pull the support member (80, 80') connected with the guide member (20, 20'); and wherein the guide member (20, 20') is adjustable to a target trajectory with the actuators (21, 21', 22, 22'), adjusting the trajectory axis of the guide member (20, 20') in at least two degrees of freedom to align the trajectory axis with the target trajectory.