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

Abstract

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.

Fig. 1

Clinical photograph shows transinguinal sonography of the left hip. A convex transducer with a small footprint is orientated in the transverse plane

Fig. 2

Sonogram of a normal right hip of a 9-month-old girl in a spica cast. The superior pubic ramus (white arrow), the cartilaginous rim of the acetabulum (asterisk), the ossified femoral metaphysis (arrowhead) and the femoral head with a small ossified nucleus are visible (open arrows)

Fig. 3

a Sonogram of the left hip of a 10-month-old girl, 2 days after closed reduction. The superior pubic ramus (white arrow), the ossified femoral metaphysis (arrowhead) and the femoral head with a small ossified nucleus are visible (open arrow). Some echogenic material is seen between the hypoechoic cartilaginous acetabular rim and the femoral head (asterisk). The femoral neck and the superior pubic ramus are in line. b Same hip, 6 weeks later. The echogenic material (asterisk) has almost disappeared

Fig. 4

a Sonogram of the right hip of an 11-month-old girl. The femoral head (open arrow) is too low and too anterior in relation to the ischial bone (arrow). This is confirmed on axial CT (b)

Fig. 5

a Sonogram in a 2.5-year-old girl with bilateral dislocation. The right femoral head is not well depicted at the level of the superior pubic ramus (arrow). Only some echogenic material is visible. The femoral neck is seen deeper in the soft tissues (arrowhead) and not in line with the superior pubic ramus. b CT scan shows that the femoral head (open arrow) is dorsally positioned in the acetabulum