How Infant Positioning Impacts Hip Motion and the Associated Implications for Babies with Hip Dysplasia

Developmental dysplasia of the hip (DDH) refers to a group of disorders, ranging from slight instability (Grades 1-3) to a severe dislocation (Grade 4) of the femoral head from the acetabulum [1]. In order to treat DDH in infants, a reduction procedure and the use of a lower body harness to secure the hip joint as the bones and ligaments re-form properly is typically prescribed. The Pavlik Harness is currently the “gold-standard” orthopedic device used to place hips in proper positioning. However, little research has been reported on the biomechanical affects during use of these device types. Although the Pavlik Harness is successful, placing infants in a full lower body brace or cast is unfavorable for caregivers. One possible alternative to these cumbersome devices is babywearing, the act of carrying an infant with the aid of a device worn by the caregiver, which is hypothesized to place infant hips in similar “M-positioning”. To understand and test this theory, the muscle biomechanics, muscle exertion, and muscle development of common infant positions, movement data (via Vicon Cameras) and muscle activity (via surface EMG) of the infants was captured during five 30-second collection conditions: in a Pavlik Harness, in a Rhino Cruiser, held in an inward-facing soft-structured baby carrier (Boba, Inc., Boulder, CO, USA), held in arms, and in a standard car seat. The results of this study support the fact that proper babywearing does not produce significantly different muscle activation when compared to the Pavlik Harness. Therefore, appropriate babywearing may promote positive hip development