A Novel Computational Model of Babywearing to Predict Growth and Development of the Pediatric Hip Joint

Developmental Dysplasia of the Hip (DDH) describes general instability, or looseness of the hip joint. Due to the developmental nature of the condition, babywearing may influence joint morphogenesis. Babywearing often places infant hips in a flexed and abducted position (M-positioning) and it has been suggested that appropriate babywearing may prevent DDH. In addition, M-positioning may be similar to the position provided by devices used to treat DDH such as the Pavlik harness (PH). Our study aims to quantify the biomechanics and muscle activity of healthy infants in a babywearing device and a PH.

For our experimental study, electromyography (EMG) and marker-based motion-capture was used to evaluate the lower extremity of fourteen healthy infants in a PH and in an inward-facing, soft-structured, baby carrier with M-positioning. Our computational study used a multi-body OpenSim model to estimate joint reaction forces (JRF) within the acetabulum in various positions. In addition, a finite element model (FEM) using a configuration representative of the M-position at 110º flexion and 50º abduction was developed to investigate pressure distribution within the acetabulum. Figure 1 shows the workflow of our studies.

Preliminary results of the FEM show a pressure concentration on the posterior superior aspect of the acetabular cartilage (Figure 2). Results suggest that there are no fully centralized JRF within the acetabulum. Pressure distributions in the acetabular cartilage may provide insight for proper hip joint development. Additionally, the similar muscle activity during babywearing with M-positioning, when compared to the PH, may indicate a more comfortable mechanism to promote healthy hip development.