Methods of adjusting a virtual implant and related surgical navigation systems

A method of operating an image-guided surgical system using imaging information for a 3-dimensional anatomical volume, the method comprising:

• detecting a pose of a probe based on information received from a tracking system, wherein the probe defines a longitudinal axis;
• upon receiving an initial placement instruction from a user, determining an initial placement and a first trajectory of a virtual implant for the 3-dimensional anatomical volume based on the pose of the probe and based on a non-zero offset from an end of the probe along the longitudinal axis, such that the first trajectory of the virtual implant is in a geometric relationship with the longitudinal axis of the probe in the pose;
• and
• after determining the initial placement of the virtual implant, adjusting the position of the virtual implant along only the first trajectory and responsive to movement of the probe while proportionally maintaining the offset,
• wherein the first trajectory is linear;
• determining a second trajectory of the virtual implant,
• wherein the second trajectory is separate from the first trajectory.