When fixation of the sacro-iliac joint is necessary, the patient is often in a critically injured state. Presently either cannulated screws are inserted under radiological control or plating is used. These techniques have drawbacks: the time-consuming cannulated screw technique is not always ideal in the polytraumatised patient, and fixation of plates generally calls for entry into non-injured areas. Since 1999 the author has used the USSC spinal system to stabilise the sacro-iliac joint in four patients. The technique does not involve entry into non-injured tissues, and provides enough stability to mobilise the patient immediately.