System and methods for performing surgical procedures and assessments

1. A system for inserting a spinal implant through a trans-psoas operative corridor to an intervertebral disc, comprising:

an elongate stimulation instrument to advance in a trans-psoas path through bodily tissue toward a lateral aspect of the targeted intervertebral disc of the lumbar spine, the elongate stimulation instrument comprising: an elongate body, a distal tip portion configured to engage an annulus of the targeted intervertebral disc, and a stimulation electrode exposed along the distal tip portion to emit an electrical stimulation signal to the bodily tissue for nerve monitoring while the elongate stimulation instrument is positioned in the trans-psoas path through the bodily tissue;

a plurality of trans-psoas dilators of increasing diameters to dilate the trans-psoas path through the bodily tissue toward the lateral aspect of the targeted intervertebral disc of the lumbar spine, the plurality of dilators comprising:

an first dilator to slidably engage with an exterior of the elongate stimulation instrument and having a first length,

a second dilator to slidably engage with an exterior of the initial dilator and having a second length less than the first length of the initial dilator, wherein the second dilator comprises: a proximal connector region configured to releasably mate with an electrical cable of a nerve monitoring system, and a stimulation electrode exposed along a tapered distal tip region of the second dilator to emit an electrical stimulation signal to the bodily tissue for nerve monitoring while the second dilator is positioned in the trans-psoas path, and

a third dilator to slidably engage with an exterior of the second dilator and having a third length less than the second length of the second dilator, wherein the third dilator comprises: a proximal connector region configured to releasably mate with the electrical cable of a nerve monitoring system, and a stimulation electrode exposed along a tapered distal tip region of the third dilator to emit an electrical stimulation signal to the bodily tissue for nerve monitoring while the third dilator is positioned in the trans-psoas path;

a working corridor instrument slidable over an outermost of the plurality of trans-psoas dilators along the trans-psoas path through the bodily tissue to the lateral aspect of the targeted intervertebral disc of the lumbar spine, the working corridor instrument being configured to enlarge the trans-psoas path through the bodily tissue and define a trans-psoas operative corridor along the trans-psoas path through the bodily tissue toward the lateral aspect of the targeted intervertebral disc of the lumbar spine, wherein the trans-psoas operative corridor defined by the working corridor instrument is dimensioned so as to pass a spinal fusion implant through the trans-psoas operative corridor to the targeted intervertebral disc of the lumbar spine.

2. The system of claim 1 , wherein the working corridor instrument has an insertion length configured to extend through the bodily tissue to the lateral aspect of the targeted intervertebral disc, the insertion length of the working corridor instrument being less than the third length of the third dilator.

3. The system of claim 2 , wherein the working corridor instrument comprises an external proximal portion that has a maximum width greater than a maximum lateral width of the trans-psoas operative corridor to be defined by the working corridor instrument.

4. The system of claim 1 , further comprising a nerve monitoring system that delivers the electrical stimulation signal to the stimulation electrode of the elongate stimulation instrument, monitors electromyographic activity detected by a set of sensor electrodes in leg muscle myotomes associated with nerves in the vicinity of the lumbar spine, and displays a numeric stimulation threshold required to obtain the electromyographic activity in at least one of said leg muscle myotomes.

5. The system of claim 4 , wherein the monitoring system comprises a control unit having a video display device, a patient module connected to the control unit via a data cable, an EMG sensor harness having the set of sensor electrodes connected to the patient module.

6. The system of claim 5 , wherein the control unit receives signals from the patient module and processes EMG responses output from the sensor electrodes to extract characteristic information for each of said leg muscle myotomes.

7. The system of claim 4 , wherein the monitoring system displays said numeric stimulation threshold in the form of a numeric value of an electrical current.

8. The system of claim 1 , wherein the plurality of trans-psoas dilators and the elongate stimulation instrument are removable from the working corridor instrument after the working corridor instrument advances to the lateral aspect of the targeted intervertebral disc of the lumbar spine to establishing the trans-psoas operative corridor to the intervertebral disc of the spine.

9. The system of claim 1 , further comprising an electrical cable for a nerve monitoring system, wherein a distal end of the electrical cable includes a connector device that is shaped to releasably receive the proximal connector region of the second dilator and to releasably receive the proximal connector region of the third dilator.

10. The system of claim 1 , wherein the working corridor instrument is shaped to define a generally cylindrical operative corridor.

11. The system of claim 1 , wherein the elongate stimulation instrument is configured to advance together with the initial dilator in the trans-psoas path through the bodily tissue toward the lateral aspect of the targeted intervertebral disc of the lumbar spine.

12. The system of claim 1 , wherein the elongate stimulation instrument comprises a K-wire.

13. The system of claim 1 , wherein the working corridor instrument comprises a working cannula that defines a lumen.