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Safe zones of pin insertion in the pelvis and acetabulum: a cadaver study

Background: The external fixator is used in emergency stabilization of unstable pelvic fractures; however, its role as a definitive fixation device remains unestablished. The main problem is the risk of injury to surrounding neurovascular structures with no definite safe corridors for pin insertion. The purpose of the current cadaver study is to outline safe corridors in the pelvis and acetabulum and directions for pin insertion. Methods: A cadaver study using two bony and three cadaver pelves was undertaken. Half pins were inserted in specific demarcated sites and tested for resistance to pullout and safety of nearby neurovascular structures. Results: The iliac crest, anterior inferior iliac spine, anterior superior iliac spine, posterior inferior iliac spine, and posterior superior iliac spine, supraacetabular region, ischial tuberosity both triangular and quadrangular areas, anterior column of the acetabulum lateral to the anterior superior iliac spine, and the lateral 1 cm of ala of the sacrum are safe pin insertion sites, while the area 1 cm medial to both the anterior inferior iliac spine and the anterior superior iliac spine, and the rest of the ala of the sacrum are unsafe. Conclusions: There are many safe areas for half pin insertion in pelvic and acetabular fractures, while there are other unsafe areas. Adequate knowledge of the safe sites and direction of pin insertion decreases the risks of neurovascular injury and allows a wider use of external fixators in pelvic and acetabular fractures.