Bowel position does not preclude safe access in prone trans-psoas surgery

There are conflicting reports of the safety of surgical approach to the lateral spine during prone transpsoas surgery based on cadaveric and radiological data however a lack of true clinical data assessing safety is available. The objective of the study is to introduce a grading system assessing the safety of the surgical approach corridor in prone transpsoas surgery specifically in relation to bowel position, and the impact of the bowel position on bowel complications after prone transpsoas (PTP) surgery. Retrospective review of prospectively collated data. A 5-point grading system of bowel overlay was established. Consecutive patients undergoing prone transpsoas surgery across eighteen months were reviewed and graded using the 5-point grading system. Exclusions for prone transpsoas surgery was the configuration of the psoas musculature and retroperitoneal vessels. No consideration was given in regard to the bowel position pre-operatively. Analysis of grade in comparison to BMI, side of approach and levels were performed with the primary outcome measure being bowel injury. One hundred and forty patients were included in the study, all of whom underwent posterior pedicle screw fixation at 207 spinal levels. Mean age was 72.0 ± 9.9 with a female (N = 93) preponderance and an average BMI of 28.2 ± 4.9 kg/m². There was a correlation with higher bowel overlay grade with lower BMI. When categorized into high (grades 3-5) or low (0-2) overlay grades, 96 patients had a low-grade overlay (68.5%), and 44 patients had a high-grade overlay (31.43%). There was no bowel complication encountered in any grade of bowel overlay. The presence of bowel overlying the lateral disc in the prone position is not a contraindication to the PTP approach. While academically interesting, anatomical and radiological studies reporting narrowing of the retroperitoneal space in the prone position have little clinical relevance when considering the safety of the approach for PTP surgery.