The treatment of hallux valgus with overriding second toe.

effusion in either child (Fig. 2) but needle aspirations subsequently demonstrated intracapsular blood under pressure . Following decompression, hip movements became much freer and the hips were radiographically reduced (Fig. lb). Discussion. Plain radiographs have been shown to be less accurate than ultrasound examination in the detection of hip effusion (Peck 1986); thus it has been suggested that they are redundant in the routine investigation of irritable hip. However, in our two cases tense effusions were not detected by ultrasound examinations whilst radiographic changes were clearly present. How can this come about? With a tense effusion, extrusion of the femoral head may tighten the anterior capsule across the front ofthe femoral neck, displacing intracapsular fluid into the acetabulum. A given volume of intracapsular fluid is therefore accommodated at lower pressure but at the expense of subluxation. In this way, with the flattening of the iliofemoral ligament against the femoral neck, the ultrasonic sign of effusion is masked. This previously unrecognised phenomenon therefore requires that subluxation is excluded by radiography before ultrasound examination can be considered reliable. Conclusion. If a significant hip effusion is suspected on clinical grounds, both a radiograph and an ultrasound examination should be performed. Neither one in isolation can exclude an effusion.