The lower extremity extension swaddling position is a risk factor for femoral trochlear dysplasia: a randomized controlled trial

Background: This study aims to investigate the effect of the infants' lower limb extension swaddling position on the development of femoral trochlear in newborn Wistar rats. Methods 40 newborn Wistar rat pups (6–8 hours after birth) were selected and fixed by wrapping both lower limbs with 0.5 cm wide medical tape for 10 days as the experimental group. 40 newborn Wistar rat pups were randomly selected without administration as the control group. On the 10th day, 10 pups of the experimental group and 10 pups of the control group were randomly selected. The pups were executed by over anesthesia, and femoral trochlear specimens were taken, which were was conducted with HE staining, saffron O-solid green staining and immunohistochemistry. The remaining pups of the experimental group were released from swaddling and were placed in the clean cabinet of the sterile laminar-flow room. At the end of the 8th week, the animals were executed by over anesthesia. The patellofemoral joint was examined by micro-CT (30° knee flexion ) and the angle, width, and depth of the trochlear groove were measured to determine the development of femoral trochlear. Results Histological staining showed that the cartilage tissue of the femoral trochlear in the experimental group decreased, while the collagen fiber and bone tissue increased. The immunohistochemistry revealed that the expression of collagen X and VEGF in the experimental group was significantly lower than that of the control group. Micro-CT showed that the trochlear groove of the experimental group tended to increase in terms of the width and angle of the trochlear groove, while the depth of the groove decreased, and the arrangement of the trochlear cartilage was disorganized. Conclusion The lower limb swaddling position may adversely affect the development of the femoral trochlear and cause damage.