Proximal focal femoral deficiency -- a rare entity in the sonographic differential diagnosis of developmental dysplasia of the hip,

In the present study, we will describe the differential diagnosis of the rare hip anomaly of proximal focal femoral deficiency (PFFD), based on an analysis of 12,488 ultrasound images of the hips of 6244 neonates, examined in our orthopaedic clinics between 1988 and 1998. The clinical manifestations and ultrasound features of PFFD will be characterised and compared with those of the normal, the mildly dysplastic, and the severely dysplastic hip. Two cases of PFFD (0.032 %) were detected during the investigation period. Both neonates had been referred to the orthopaedic clinic for further evaluation after the initial ultrasound findings suggested an anomaly in the coxal-femoral region. Correct identification of anatomical structures in the acetabular region (acetabular labrum and lower edge of the ilium) was not possible, but the iliac line, femoral head, and greater trochanter could be reliably visualised. Because of these findings, a deformity in the coxal-femoral region was suspected, and further diagnosis was recommended. PFFD was subsequently diagnosed, and specific treatment was initiated. PFFD should be suspected in any neonate with suspicious clinical findings and failure of ultrasound to clearly visualise anatomical landmarks in the region of the acetabulum (acetabular labrum, lower edge of the ilium, cartilage-bone interface) despite the use of a sufficient imaging technique. Radiographs should then be obtained to confirm or refute the tentative diagnosis. Infants with PFFD can then receive proper treatment without unnecessary therapeutic trial and error.