1052 - Can Pulvinar Measurements Help Us Diagnose Developmental Dysplasia of the Hip: How Does it Compare to Alpha Angle and Percentage Bony Coverage?

Objectives: Diagnosis of developmental dysplasia of the hip (DDH) is based on ultrasound (US) morphology of the alpha angle (ɑ) and % bony coverage (%BC). Observations of increased pulvinar prompted the authors to study the significance of this finding. The Couture and Treguier method measures pubofemoral distance (PFD) (pubic cartilage (CT) plus pulvinar thickness (PT)). Thick PT is abnormal; thick CT is normal. The purpose of this study is to evaluate whether PFD correlates with ɑ and %BC and determine the true/false positive rate should this method be widely used.

Design: This is a retrospective study on infants < 6 months screened with hip US at one institution from 2016- 2020. Patients with syndromes, neuromuscular disorders or inadequate US quality were excluded. Demographic and clinical data were collected. A radiologist measured ɑ, %BC, PFD, PT, and CT on patients’ first US.

Results: 130 patients with 252 hips were included. 157 hips had DDH based on ɑ and/or %BC; 43 hips based on PFD; 159 hips based on abnormal ɑ, %BC, and/or PFD. Among 209 hips with normal PFD, mean ɑ was 61 ± 8.2°; mean %BC was 50 ± 11%. Among 43 hips with abnormal PFD, mean ɑ was 46 ± 11° mean %BC was 34 ± 12%. Of hips with abnormal PFD, there were 9 “false positives” and 29 “true positives”, with a positive predictive value (PPV) of 76%. Bivariate analysis demonstrated associations between PFD and both ɑ and %BC but not age.

Conclusions: PFD significantly correlates with ɑ and %BC and the PPV of using PFD to diagnose DDH is 76%. Measurement of PFD may refine US screening of DDH but requires radiologist experience in this method. A 21% false positive rate could lead to overtreatment of DDH, but measurement of CT and PT when PFD is abnormal can prevent this.