Surgical access system and related methods

1. A method for inserting an implant through a trans-psoas operative corridor to a lumbar spine, comprising:

simultaneously advancing plurality of retractor blades of a trans-psoas retractor tool slidably over a trans-psoas dilator and along a lateral, trans-psoas path through bodily tissue toward a targeted intervertebral disc of a lumbar spine, wherein the plurality of retractor blades each have an outwardly facing convex surface region configured to engage a psoas muscle and that each have an inwardly facing concave surface region configured to engage a cylindrical exterior surface region of the trans-psoas dilator, the plurality of retractor blades including at least a caudal-most retractor blade and a cephalad-most retractor blade when the trans-psoas retractor tool creates the operative corridor along the lateral, trans-psoas path, wherein the trans-psoas refractor tool further comprises a blade holder assembly comprising adjustable arm portions, wherein the plurality of retractor blades extend generally perpendicularly relative to the arm portions of the blade holder assembly, wherein a first pivotable arm portion of the adjustable arm portions is configured to pivotably adjust the cephalad-most retractor blade relative to the caudal-most retractor blade, wherein the trans-psoas refractor tool is configured to adjust from a first position in which the plurality of retractor blades are positioned to simultaneously advance along the lateral, trans-psoas path to a second position in which the caudal-most retractor blade and the cephalad-most retractor blade are spaced apart from one another, the blade holder assembly comprising a rotatable actuator that causes independent linear movement of a position of one retractor blade of the plurality of retractor blades relative to another refractor blade of the plurality of retractor blades in response to rotation of the rotatable actuator; and

passing an implant through the operative corridor along the lateral, trans-psoas path toward the targeted intervertebral disc of the lumbar spine while the plurality of retractor blades of the trans-psoas retractor tool maintain the operative corridor along the lateral, trans-psoas path.

2. The method of claim 1 , wherein said simultaneously advancing the plurality of retractor blades while the multi-bladed psoas retractor tool is in the first position such that the caudal-most refractor blade and the cephalad-most retractor blade are adjacent to one another and simultaneously slide over the cylindrical exterior surface region of the trans-psoas dilator toward the lumbar spine to enlarge the tissue distraction corridor.

3. The method of claim 1 , wherein the plurality of retractor blades includes a posterior-most retractor blade when the trans-psoas retractor tool creates the operative corridor along the lateral, trans-psoas path.

4. The method of claim 3 , wherein the position of the posterior-most retractor blade is linearly adjustable relative in response to rotation of the rotatable actuator.

5. The method of claim 4 , further comprising linearly adjusting the position of the posterior-most retractor blade relative to the caudal-most retractor blade and the cephalad-most retractor blade while the caudal-most retractor blade and the cephalad-most retractor blade remain generally stationary relative to the blade holder assembly.

6. The method of claim 3 , wherein the rotatable actuator of the blade holder assembly is configured to linearly adjust a translating arm portion of the adjustable arm portions of the blade holder assembly that is coupled to the posterior-most retractor blade.

7. The method of claim 6 , further comprising linearly adjusting the position of the posterior-most retractor blade relative to the caudal-most retractor blade and the cephalad-most retractor blade by causing the rotatable actuator of the blade holder assembly to interact with teeth on a rack of the translating arm portion.

8. The method of claim 1 , wherein a second pivotable arm portion of the adjustable arm portions is configured to pivotably adjust the caudal-most retractor blade relative to the cephalad-most retractor blade.

9. The method of claim 1 , further comprising using a dilator system to create a tissue distraction corridor along the lateral, trans-psoas path through bodily tissue toward the targeted intervertebral disc of the lumbar spine, wherein an outermost dilator of the dilator system is said trans-psoas dilator having said cylindrical exterior surface region configured to be engaged by the plurality of retractor blades of the trans-psoas retractor tool.

10. The method of claim 9 , wherein the dilator system comprises: an initial dilator, at least one supplemental dilator that slidably advances over an exterior of the initial dilator and engages the lumbar spine, and the trans-psoas dilator.

11. The method of claim 1 , further comprising positioning an elongate inner member in a lumen of the initial dilator of the dilator system, wherein at least one instrument selected from the group consisting of said elongate inner member, the initial dilator, the supplemental dilator, and the trans-psoas dilator includes a stimulation electrode that outputs electrical stimulation for nerve monitoring when the instrument is positioned in the lateral, trans-psoas path.

12. The method of claim 11 , further comprising using a monitoring system that: (a) delivers an electrical stimulation sign to the stimulation electrode of the at least one instrument selected from the group consisting of said elongate inner member, the initial dilator, the supplemental dilator, and the outer dilator, (b) monitors electromyographic activity detected by a set of sensor electrodes in leg muscle myotomes associated with nerves in the vicinity of the spinal disc, and (c) displays to a user: a numeric stimulation threshold that changes in response to the electromyographic activity detected in said leg muscle myotomes, a graphical representation of a patient, and myotomes levels being monitored.

13. The method of claim 12 , 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.

14. The method of claim 11 , further comprising advancing the elongate inner member together with the initial dilator along the lateral, trans-psoas path.

15. The method of claim 1 , further comprising emitting light toward the targeted intervertebral disc of the lumbar spine using one or more light emitting devices coupled with one or more of the caudal-most retractor blade and the cephalad-most retractor blade when trans-psoas retractor tool forms the operative corridor.

16. The method of claim 1 , further comprising removably engaging a spine penetration element with a corresponding one of the plurality of retractor blades so that a distal portion of the spine penetration element extends distally from said corresponding one of the plurality of retractor blades to anchor said corresponding one of the plurality of retractor blades in fixed relation relative the lumbar spine.

17. The method of claim 16 , wherein the spine penetration element includes a tapered tip for penetrating the lumbar spine and includes a proximal connection portion to mate with said corresponding one of the plurality of retractor blades.

18. The method of claim 1 , wherein when the trans-psoas retractor tool is in the first position, the caudal-most retractor blade and the cephalad-most retractor blade abut one another.

19. The method of claim 1 , wherein said passing the implant comprises passing a lateral approach fusion implant carrying bone products or bone morphogenic protein through the operative corridor along the lateral, trans-psoas path.