Quantification of Sacroiliac and Sacral Exposure via the Lateral Window Approach: Impact of Anterior Superior Iliac Spine Osteotomy

Abstract

OBJECTIVES: The traditional lateral window of the ilioinguinal approach for open sacroiliac (SI) joint reduction provides limited visualization of the L5 nerve root as well as the anterior aspect of the sacral ala and SI joint. Adding an anterior superior iliac spine (ASIS) osteotomy may enhance exposure and improve safety and ease of reduction. This cadaveric study evaluates whether ASIS osteotomy significantly increases SI joint visualization compared with the standard lateral window.

DESIGN: Four fresh-frozen cadaveric specimens (8 SI joints) underwent lateral window exposure. Kirschner wires marked visible osseous boundaries, and calibrated digital images were obtained. A digastric ASIS osteotomy was then performed, preserving external oblique insertion. The ASIS was reflected medially to enhance visualization, and the most medial Kirschner wires were repositioned to reflect the expanded view.

SETTING: Cadaveric laboratory.

PATIENT SELECTION CRITERIA: Cadavers of approximately standard proportions.

OUTCOME MEASURES AND COMPARISONS: Images of SI joint exposure were captured and analyzed using ImageJ software. Surface area exposure before and after osteotomy was compared using a paired t test.

RESULTS: The lateral window initially provided a mean SI joint exposure of 53.4 cm 2 ± 17.3 cm 2 . After ASIS osteotomy, mean exposure significantly increased to 88.0 cm 2 ± 26.6 cm 2 ( P = 0.04). The mean relative increase in exposure after the osteotomy was 70% ± 24%.

CONCLUSIONS: In this cadaveric study, the addition of an ASIS osteotomy to the traditional lateral window of the ilioinguinal approach resulted in a significant increase in SI joint visualization. The enhanced exposure may facilitate more accurate reduction and safer instrumentation. These findings suggest that the ASIS osteotomy may be a beneficial adjunct to the lateral window for management of complex