Double fertilization results in the formation of one diploid embryo and a triploid endosperm. Double fertilization is characterized by the formation of two embryos; the embryo proper which is diploid and the fusion product of the central cell with one male gamete which is triploid. This secondary triploid zygote develops into the endosperm.
This is because the shoulder has a shallower joint socket, so it can become dislocated easier.