Introduction:

Among the interbody fusions, the Lateral Lumbar Interbody Fusion (LLIF) allowed access to the lumbar spine through the major psoas muscle, which offers several advantages to the spine surgeon. However, some of its drawbacks cause surgeons to avoid using it as a daily practice. Therefore, to address some of these challenges, the Prone Transpsoas technique was proposed, differing mainly from the traditional technique on patient position – moving from lateral to prone decubitus, theoretically enhancing the lordosis and impacting the psoas morphology.

Methods:

Twenty-four consecutive patients were invited to perform MRI exams in three different positions (Prone, Dorsal, Lateral). Two observers measured the following parameters, vertebral body size, psoas diameter, psoas anterior border distance, plexus distance, total lumbar lordosis, distal lumbar lordosis, and proximal lumbar lordosis. Values of p < 0,05 were deemed significant.

Results:

The prone position yielded a significant increase in the lumbar lordosis, both L1S1 (57° vs., 46,5°) and proximal lordosis (40,4° vs. 36,9°) when compared to lateral position. Regarding the morphological aspects, the patients in prone presented lesser psoas muscles forward shift, but no difference was noted in the plexus position neither for L3L4 nor L4L5.

Conclusion:

The prone position results in a significantly increased lumbar lordosis, both distal and proximal, which may enable the spine surgeon to achieve significant sagittal restoration just by positioning. The prone position also produced a posterior retraction of the psoas muscle. However, it did not significantly affect the position of the plexus concerning the vertebral body.