Pubo-femoral distance: an easy sonographic screening test to avoid late diagnosis of developmental dysplasia of the hip

Abstract

To propose an easy and reproducible sonographic screening test able to avoid late presentation of developmental dysplasia of the hip (DDH). The pubo-femoral distance (PFD) cut-off point was determined on 980 infants who underwent ultrasonography of the hips in comparison with the final diagnosis, based on clinical, ultrasound data and follow-up. PFD reproducibility was tested on 52 hips by both an experienced and an inexperienced radiologist. After teaching this screening method to general radiologists, its impact was evaluated by analysing the rate of late diagnosis in an entire administrative area. An abnormal PFD threshold above 6 mm gave a sensitivity of 97.4 % for the diagnosis of DDH (271 hips) and a specificity of 84 %. Sensitivity increased to 100 % when taking into consideration children of 1 month or older. The PFD measurement stayed reproducible even in inexperienced hands (k = 0.795). For 3 years, following the extension of screening to all female infants, there was no late diagnosis of DDH in girls in amongst a catchment area of 1 million inhabitants. PFD measurement with a threshold for abnormality of 6 mm at the age of 1 month, without asymmetry above 1.5 mm, could eradicate DDH late diagnosis.