Anatomy of the superior hypogastric plexus and its relevance to anterior lumbar interbody fusion

OBJECTIVE Retrograde ejaculation (RE) is a known complication of anterior lumbar interbody fusion (ALIF) and results from injury to the superior hypogastric plexus (SHP) during intervertebral disc exposure. Yet, there has been no recommendation for SHP mobilization. Thus, the aim of this study was to describe the anatomy of the SHP and vessels at the L5–S1 level, and to evaluate the possibility of SHP mobilization and its retraction to the side. METHODS Twelve formaldehyde-embalmed cadavers (6 female and 6 male; mean age 65.5 years [range 60–77 years]) were dissected. Distances from the SHP and middle sacral vessels to the midline were measured at the L5–S1 level. The relationship of the great vessel bifurcations and common iliac vessels to the SHP were noted. The extent of lateral retraction of the SHP following mobilization was measured in relation to the midline. Moreover, the positions of the SHP and middle sacral vessels relative to the midline at the L5–S1 level were determined. RESULTS The SHP formed below the aortic bifurcation and was present at the L5–S1 level in all cases. The SHP overlaid the midline with a left-sided shift. There were 4 cases (33.3%) in which lateral retraction was not achievable because the plexus divided into hypogastric nerves at the L5–S1 level or was too wide for safe mobilization. In the remaining cases, retraction on the left side was achievable up to 15.3 mm from the midline, while retraction to the right side was limited to 5.3 mm from the midline. The types of SHP morphological arrangement included single cord (41.7%), plexiform (41.7%), and fiber (16.6%). CONCLUSIONS Based on the more extensive left-sided shift of the SHP at the L5–S1 level and frequent presence of the third left splanchnic lumbar nerve, attempting retraction to the left side is recommended. If it is not feasible, the SHP should be split at the midline, with both components mobilized laterally.