System and methods for performing surgical procedures and assessments

A method of inserting a spinal implant through a trans-psoas operative corridor to an intervertebral disc, comprising:

• mounting a plurality of EMG electrodes proximate to selected leg muscles;
• activating a control unit operable to provide a stimulation signal and including a graphical user interface to receive user input and to display neuromuscular response information in response to signals from the EMG electrodes;
• inserting an initial dilator cannula in a trans-psoas path through bodily tissue toward a lateral aspect of a spine while an elongate stimulation instrument is disposed within an inner lumen of the initial dilator cannula;
• activating the elongate stimulation instrument to deliver the stimulation signal proximate to a distal end of the initial dilator cannula when the initial dilator cannula is inserted into the trans-psoas path toward the spine;
• monitoring the neuromuscular response information displayed by the control unit in response to delivery of the stimulation signal when the initial dilator cannula is inserted into the trans-psoas path toward the spine;
• advancing two or more sequential dilator cannulas of increasing diameter in the trans-psoas path toward the spine;
• advancing a working corridor instrument over the two or more sequential dilator cannulas in the trans-psoas path toward the spine;
• establishing a trans-psoas operative corridor to an intervertebral disc of the spine using the working corridor instrument;
• and
• delivering a spinal fusion implant through the trans-psoas operative corridor toward the spine.