Dilation system and method

1. A dilation system, comprising:

a first dilator including an elongated body having longitudinal axis, a proximal end, a distal end, and an outer surface extending between the proximal end and the distal end, the first dilator having a major axis and a minor axis, the minor axis being substantially normal to the major axis; and

a second dilator including an elongated body having longitudinal axis, a proximal end, a distal end, an outer surface extending between the proximal end and the distal end, and a bore extending from the proximal end to the distal end, the second dilator having a major axis and a minor axis, the minor axis of the second dilator being substantially normal to the major axis of the second dilator, the bore of the second dilator configured to matingly receive the first dilator in such a way that the major axis of the second dilator is aligned with the minor axis of the first dilator and the minor axis of the second dilator is aligned with the major axis of the first dilator.

2. The dilation system of claim 1 , wherein the elongated body of the first dilator has a bore extending from the proximal end to the distal end, and wherein the bore of the first dilator is aligned with the longitudinal axis of the first dilator.

3. The dilation system of claim 2 , wherein the bore of the second dilator is aligned with the longitudinal axis of the second dilator.

4. The dilation system of claim 1 , wherein the elongated body of the first dilator has a bore extending from the proximal end to the distal end, and wherein the bore of the first dilator is offset relative to the longitudinal axis of the first dilator.

5. The dilation system of claim 4 , wherein the bore of the second dilator is aligned with the longitudinal axis of the second dilator.

6. The dilation system of claim 1 , wherein the elongated body of the first dilator has at least one channel for receiving a stimulating probe, the channel extending from the proximal end to the distal end and intersecting the major axis of the first dilator.

7. The dilation system of claim 6 , wherein the elongated body of the second dilator has at least one channel for receiving a stimulating probe, the channel extending from the proximal end to the distal end and intersecting the major axis of the second dilator.

8. The dilation system of claim 1 further comprising:

a third dilator including an elongated body having longitudinal axis, a proximal end, a distal end, an outer surface extending between the proximal end and the distal end, and a bore extending from the proximal end to the distal end, the third dilator having a substantially circular transverse cross section, the bore of the third dilator configured to matingly receive the second dilator.

9. The dilation system of claim 8 , wherein the elongated body of the third dilator has at least one channel for receiving a stimulating probe, the channel extending from the proximal end to the distal end.

10. The dilation system of claim 1 , wherein the bore of the second dilator is aligned with the longitudinal axis of the second dilator.

11. The dilation system of claim 1 , wherein the elongated body of the second dilator has at least one channel for receiving a stimulating probe, the channel extending from the proximal end to the distal end and intersecting the major axis of the second dilator.

12. A method of forming an access opening through a psoas muscle to a patient's spine, the psoas muscle having a plurality of muscle fibers, the method comprising:

inserting a dilator having a major axis and a minor axis through the psoas muscle toward the patient's spine with the major axis of the dilator in a substantially parallel relationship to the muscle fibers of the psoas muscle; and

rotating the dilator to position the major axis of the dilator in a substantially perpendicular relationship to the muscle fibers of the psoas muscle.

13. The method of claim 12 , wherein the dilator is a first dilator, and wherein the method further comprises:

inserting a second dilator having a major axis and a minor axis over the first dilator and through the psoas muscle toward the patient's spine with the major axis of the second dilator in a substantially parallel relationship to the muscle fibers of the psoas muscle; and

rotating the second dilator and the first dilator to position the major axis of the second dilator in a substantially perpendicular relationship to the muscle fibers of the psoas muscle.

14. The method of claim 13 , further comprising:

inserting a third dilator having a circular transverse cross section over the second dilator and through the psoas muscle toward the patient's spine.

15. The method of claim 14 , further comprising:

inserting a second stimulating probe into a channel extending from a proximal end to a distal end of the third dilator in a way to locate a safe zone in the psoas muscle.

16. The method of claim 13 , further comprising:

inserting a stimulating probe into a channel extending from a proximal end to a distal end of the second dilator and intersecting the major axis of the second dilator in a way to locate a safe zone in the psoas muscle.

17. The method of claim 12 further comprising inserting a stimulating probe into the psoas muscle to locate a safe zone in the psoas muscle prior to inserting the dilator through the psoas muscle, and wherein the step of inserting the dilator further comprises inserting the dilator over the stimulating probe.

18. The method of claim 17 , further comprising:

inserting a second stimulating probe into a channel extending from a proximal end to a distal end of the dilator and intersecting the major axis of the dilator in a way to locate a safe zone in the psoas muscle.