Which Clinical Exam findings are most predictive of an abnormal hip ultrasound in the newborn? A chart review from a Canadian pediatric hospital
Authors: Drover Anne 
Published: May 2018

Abstract

BACKGROUND
Developmental dysplasia of the hips is a condition that if not detected early and managed properly can lead to lifelong morbidity. The incidence of DDH in most developed countries is reported to be 1.5 to 20 cases per 1000 births. The Canadian Task Force on Preventive Health Care reports fair evidence to include a serial clinical examination of the hips by a trained clinician in the periodic health examination of all infants until they are walking independently. The indications for ultrasound examination are less clear. Guidelines for the clinical exam cite indications of imaging to be unstable hip, hip laxity, hip click and asymmetric skin folds. Given that some of these findings are extremely common it is likely that a large number of normal hips are being imaged unnecessarily.

OBJECTIVES
The purpose of this project is to determine which clinical findings are most predictive of an abnormal hip on ultrasound. It is hoped that this will assist the paediatrician or family doctor to balance unnecessary testing with the fear of missing an abnormal hip.

DESIGN/METHODS
All hip ultrasounds performed at a Canadian children’s hospital during 2016/17 on infants less than one year were reviewed for indication and outcome. The birth rate for the same year was 2,861. A total of 528 hip ultrasounds were performed. 156 ultrasounds were ordered by Paediatric Orthopaedic specialists and thus were not reviewed, leaving 372 ultrasounds for review. Ultrasounds were classified by age category at the time of imaging: <14 days, 14–28 days, 29–60 days, 61 days-6 months, 6 months-1 year. Tests were ordered by paediatricians, neonatologists, family doctors and nurse practitioners. The indications for ultrasound were categorized into 9 categories; hip click, hip laxity, unstable hip (positive Barlow, dislocatable hip), asymmetric skin folds, breech presentation, family history of DDH, hip click + breech, hip laxity + breech, or no indication given. When multiple terms were noted on requisition a hierarchy was followed with hip laxity>hip click>asymmetric skin folds. Ultrasound reports reported as normal or abnormal.

RESULTS
The primary indication for hip ultrasound was asymmetric skin folds, (N-132); followed by Hip laxity (N-101), Hip click (N-72), Unstable hip (positive Barlow, dislocatable hip) (N-31), no indication noted (N-23), Breech presentation (N-8), Family History of DDH (N-3) and other (N-2). The ultrasound findings with asymmetric skin folds revealed 100% of tests were normal (132/132) on first ultrasound regardless of baby’s age at imaging. For Hip laxity, 93% (94/101) ultrasounds were normal following second ultrasound and for hip click, 99% (71/72) were normal following second ultrasound. For those ultrasounds that were performed for hip click and hip laxity (N-173), only one ultrasound would have been required if performed at greater than 8 weeks of age. In the unstable hip, 82% (28/34) were normal following second ultrasound. None of the ultrasounds performed for risk factors such as family history or breech presentation were abnormal but when combined with a lax hip exam 3 were reported as abnormal. In our study, a diagnosis of DDH was given to 15/2,861 newborns. Of these 15; the clinical finding was 7/16 hip laxity alone, 6/16 unstable hip, 3/16 hip laxity + breech.

CONCLUSION
Though practitioners must continue to be vigilent in clinical hip surveillance, symmetric skin folds and isolated hip click are low yield indications for hip ultrasound in the newborn. For hip laxity or unstable hip, waiting until 8 weeks improves the reliability of the ultrasound result and thus reducing unnecessary retesting. The breech presentation alone did not increase diagnosis but when combined with exam was predictive.