Pulvinar and pubic cartilage measurements to refine universal ultrasound screening for developmental dysplasia of the hip: Data from 1896 infant hips.

PURPOSE: Screening modalities for Developmental Dysplasia of the Hip (DDH) and indications for treatment of mild forms remain controversial. Ultrasound (US) measurement of the pubofemoral distance (PFD > 6 mm, composed of the pubic cartilage and the pulvinar) can avoid late diagnoses of DDH. A thick pubic cartilage may nevertheless lead to false positives. The purpose of this study was to establish standard measurements of pubic cartilage and pulvinar, through universal US screening, to lower false positive results and thus any overtreatment. METHODS: This is a single-center observational prospective study conducted from December 2016 to January 2018, on infants who underwent universal US screening for DDH. The only inclusion criterion was an adjusted age between 4 and 12 weeks when US was realized. PFD measurement was made using the Couture and Tréguier method. In addition, thicknesses of pubic cartilage and pulvinar were measured on the same US section, in millimeters. RESULTS: Nine hundred and forty-eight patients, representing 1896 hips, were included. The average value of pubic cartilage thickness was 1.25 mm ±â€¯0.58 mm, with an upper threshold of 2.39 mm (+1.96σ). The average value of pulvinar thickness was 2.67 mm ±â€¯0.78 mm, with an upper threshold of 4.20 mm (+1.96σ). We found high inter-observer reproducibility in pubic cartilage measurements. CONCLUSION: Systematic measurements of pubic cartilage and pulvinar may refine therapeutic decision by identifying false positives. Patients with increased PFD due to a thick pubic cartilage >2,39 mm, without an associated pulvinar enlargement (<4,20 mm), could be therefore only monitored and not overtreated.