Human limbs can never grow out when broken, because humans are different from other animals, such as other low-cell animals, such as earthworms can grow their heads or tails when broken. Geckos can regenerate after their tails are broken and can grow their own tails. Amphibian lizards, after their tails are broken, can also grow. Such low-cell animals, lower animals, can regenerate, so after their limbs are broken, they can grow limbs again. In contrast, humans are mammals, higher animals, and when a limb is severed, it cannot be regenerated. Therefore, the severed limb must be replanted through current surgical procedures, which in medical terms means that the severed limb will be replanted and become alive. Therefore, it is absolutely impossible to regenerate an amputated human limb, but due to the current development of medicine, I believe that in the future, when science has reached a certain level, it is hoped that the amputated limb can be regenerated, which is the ultimate goal. The limb does not grow out because of the human genetic tissue cells and decided. The human body has no ability to regenerate a broken limb. Therefore, it is necessary to use surgery to replant and reimplant the broken limb to continue its function.