HIP SPICA CAST A hip spica is a large cast which extends from the mid-chest down to the ankle of the broken leg. It also covers the other leg slightly above the knee. A bar may be placed between the legs in order to help reinforce the cast and prevent breakage. An area around the groin is left open in order to facilitate toileting. What is a hip cast? A hip cast is also called a hip spica cast. It corrects hip dysplasia and other conditions in infants and children. Adults often don't use hip casts. If an adult has hip dysplasia, surgery can fix the condition. The cast keeps a baby's or child's pelvis and thighbones still so the hip joint bones can move into the right position.