Halo-pelvic apparatus: peritoneal penetration by pelvic pins

In a series of over 250 patients, four suffered peritoneal penetration by one of the pelvic pins while being put into a halo-pelvic apparatus. In each case a point on the iliac crest two to three centimetres posterior to the anterior superior iliac crest had been used as the anterior landmark for the positioning of the pelvic pin guide. To avoid this complication we advise that the anterior landmark for the guide should be the "tubercle of the crest", five centimetres or more posterior to the anterior superior iliac spine.