Quantification of bony pelvic exposure through the modified Stoppa approach

Authors previously have described anatomic structures commonly seen through the modified Stoppa approach; however, no study has formally quantified the areas and amount of visual bony exposure that is obtained. This information is important for proper preoperative planning of acetabulum fractures with regard to fracture reduction and fixation. The aim of this study was to quantify and describe the extent of bony pelvis exposed while identifying the limits of exposure from osseous landmarks within the dissection of the modified Stoppa approach.

Ten modified Stoppa approaches were performed on cadavers. Specific anatomic landmarks were identified, and the far boundaries of the exposed osseous structures from the surgeon's perspective were marked on each cadaver. All soft tissues were then stripped, and calibrated digital images of the demarcated area of exposure were taken and total viewable osseous surface area was calculated. Additionally, the boundaries of exposure based on various anatomic landmarks were determined.

All neurovascular structures at potential risk (external iliac, obturator, corona mortis, and superior gluteal) were identified in each exposure. The entire pelvic brim from the pubic symphysis to beyond the sacroiliac joint was visualized in all exposures, with an average ± SD of 10 ± 5 mm of anterior sacrum exposed. On average, visualization above the pelvic brim was possible 15 ± 5 mm anteriorly over the acetabular roof and 19 ± 5 mm posteriorly above the greater sciatic notch. The viewable area included 51 ± 5 mm below the pelvic brim along the quadrilateral surface, with 41 ± 5 mm of the obturator foramen depth and 29 ± 9 mm of the greater sciatic notch seen on average. Approximately 32% ± 4% of the total surface area of the inner pelvis was able to be visualized, which included 79% ± 5% of the inner true pelvis below the brim and 80% ± 6% of the quadrilateral surface.

The modified Stoppa approach allows for exposure of most (79%) of the inner true bony pelvis including the entire pelvic brim and 80% of the quadrilateral surface. On average, visualization is possible 2 cm above the pelvic brim and 5 cm below the pelvic brim along the quadrilateral surface, providing adequate anterior exposure for clamp and implant placement.