A robotic surgical system for performing minimally invasive surgery, the system comprising: a robotic arm with an end effector; a first dilator to access a vertebrae of a patient through the patient's muscles and skin, wherein the first dilator defines a working channel for accessing the vertebrae; one or more subsequent dilators (202b-d, 314) sized and shaped to slide over the first dilator and/or one or more of the one or more subsequent dilators (202b-d, 314), wherein: the one or more subsequent dilators (202b-d, 314) comprise a last added dilator each of the one or more subsequent dilators (202b-d, 314) are configured to be positioned over the preceding dilators and increase the size of the working channel, each dilator (202a-202c) except the last added dilator is configured to be removed from the patient thereby leaving the last added dilator, the last added dilator is configured to be attached to the end effector of the robotic arm using a dilator fixator; and a manipulator configured to allow robotically-assisted or unassisted positioning and/or movement of the end effector by a user with at least four degrees of freedom thereby automatically adjusting an angle and/or position of the last added dilator with respect to the vertebrae and aligning an axis defined by the last added dilator with a desired trajectory during a surgical procedure without removal of the last added dilator from the patient tissue during the repositioning, a surgical instrument guide configured to be placed inside of the attached dilator after the preceding dilators are removed, wherein the surgical instrument guide is sized and shaped to fit at least partially inside the attached dilator along an axis defined by the dilator, wherein the end effector comprises the surgical instrument guide attached thereto, configured to hold and/or restrict movement of a surgical instrument therethrough. a robotic arm with an end effector; a first dilator to access a vertebrae of a patient through the patient's muscles and skin, wherein the first dilator defines a working channel for accessing the vertebrae; one or more subsequent dilators (202b-d, 314) sized and shaped to slide over the first dilator and/or one or more of the one or more subsequent dilators (202b-d, 314), wherein: the one or more subsequent dilators (202b-d, 314) comprise a last added dilator each of the one or more subsequent dilators (202b-d, 314) are configured to be positioned over the preceding dilators and increase the size of the working channel, each dilator (202a-202c) except the last added dilator is configured to be removed from the patient thereby leaving the last added dilator, the last added dilator is configured to be attached to the end effector of the robotic arm using a dilator fixator; and a manipulator configured to allow robotically-assisted or unassisted positioning and/or movement of the end effector by a user with at least four degrees of freedom thereby automatically adjusting an angle and/or position of the last added dilator with respect to the vertebrae and aligning an axis defined by the last added dilator with a desired trajectory during a surgical procedure without removal of the last added dilator from the patient tissue during the repositioning, a surgical instrument guide configured to be placed inside of the attached dilator after the preceding dilators are removed, wherein the surgical instrument guide is sized and shaped to fit at least partially inside the attached dilator along an axis defined by the dilator, wherein the end effector comprises the surgical instrument guide attached thereto, configured to hold and/or restrict movement of a surgical instrument therethrough. the one or more subsequent dilators (202b-d, 314) comprise a last added dilator each of the one or more subsequent dilators (202b-d, 314) are configured to be positioned over the preceding dilators and increase the size of the working channel, each dilator (202a-202c) except the last added dilator is configured to be removed from the patient thereby leaving the last added dilator, the last added dilator is configured to be attached to the end effector of the robotic arm using a dilator fixator; and a manipulator configured to allow robotically-assisted or unassisted positioning and/or movement of the end effector by a user with at least four degrees of freedom thereby automatically adjusting an angle and/or position of the last added dilator with respect to the vertebrae and aligning an axis defined by the last added dilator with a desired trajectory during a surgical procedure without removal of the last added dilator from the patient tissue during the repositioning, a surgical instrument guide configured to be placed inside of the attached dilator after the preceding dilators are removed, wherein the surgical instrument guide is sized and shaped to fit at least partially inside the attached dilator along an axis defined by the dilator, wherein the end effector comprises the surgical instrument guide attached thereto, configured to hold and/or restrict movement of a surgical instrument therethrough.