Well because the human body was designed to be symmetrical, If this were to happen the child would live until the body compensates, with an uneven gait. This uneven gait can affect the curvature of the spine if it goes on long enough causing exaggerated curvatures, called Scoliosis.
Here is an interesting fact though, a fracture through the epiphyseal plate of developing children when broken can actually stop growth of the bone causing almost the exact same thing.
