Study Design. 

Retrospective review of prospectively collected data.

Objective. 

To investigate the size of prepsoas surgical corridors, developed between the iliopsoas and prespinal vessels, at all disk levels between L1 and S1 granted by left and right lateral antepsoas (ATP) approaches. Secondary aims include evaluation of presurgery radiographic prepsoas windows between L1 and S1 with respect to the intraoperative findings.

Summary of Background Data. 

The ATP technique is an evolving alternative to the transpsoas and direct anterior exposures for lumbar fusion. However, the vascular morphometric data of the ATP approach remain underexplored, especially at L5–S1.

Materials and Methods. 

Patients indicated for ATP lumbar-lumbosacral fusion between September 2018 and February 2020 were enrolled (n=121). Data were collected prospectively, including the following (in mm): intraoperative manual measurements of the premobilization psoas-vessel (pre-PV) window, the final postmobilization psoas-vessel (post-PV) window, and the preoperative radiographic psoas-to-vessel distance at the respective studied disk levels.

Results. 

A total of 121 patients (75 female, mean age: 55.3 yr, 81.8% right-sided approach) underwent a total of 279 levels of spinal fusion. Irrespective of the ATP access laterality, we noted ample postmobilization psoas-vessel (post-PV differential) corridors: largest at L4–L5 (36–38 mm) followed by L5–S1 (31–35 mm), L3–L4 (32–33 mm), L2–L3 (28–30 mm), and L1–L2 (20–24 mm). Similarly, the relative increases of the psoas-vessel corridors (post-PV and pre-PV differentials, averaged: 31 mm at L5–S1, 32 mm at L4–L5, 26 mm at L3–L4, 25 mm at L2–L3, and 14 mm at L1–L2) were also significant in both lateral approaches. In right flank approaches, the right vascular structures projected more dorsally compared with left-sided vasculature (P<0.05).

Conclusion. 

The ATP access offers generous bilateral prepsoas surgical windows to L1–S1 intervertebral disks, allowing for a safe anterior column release, decompression, instrumentation, and fusion.