Transinguinal sonographic determination of the position of the femoral head after reposition and follow-up in a spica cast

BACKGROUND: Transinguinal sonography can be used to demonstrate the position of the femoral head after reduction of a dislocated hip. OBJECTIVE: To determine whether transinguinal sonography can replace radiography and CT in the follow-up after reduction of a hip dislocation? MATERIALS AND METHODS: Thirty-three children with 39 dislocated hips were followed up with sonography after reduction and immobilization in a spica cast. In cases of an abnormal position a CT scan was advised. A pelvic radiograph at the end of treatment served as an indicator that no dislocations were missed during the previous sonographic examinations. RESULTS: The repositioned hips were examined on 138 occasions. Twenty-four examinations were abnormal and CT scanning was performed on 11 occasions. In four children additional CT was done because a recurrent dislocation was suspected or because sonography was difficult to perform. No dislocations were demonstrated. In five children a recurrent dislocation was suspected, on one or more occasions. In all but one child a CT scan was performed that confirmed the dislocation. CONCLUSION: Transinguinal sonography is well-suited to demonstrate a normal position of the femoral head in a spica cast. Transinguinal sonography decreases the number of radiographs and CT scans and reduces the exposure to ionizing radiation.