Hello Thank you for asking question. This is Dr Adil. Depending upon the nature and function of fractured bone, the duration of plaster is decided. For example, tibia, which bears larger portion of weight of the body, needs much time to heal, Fibula on the other hand, supports the tibia and provides more stability to ankle joint. Usually bony callus formation completes within four weeks, and after four to six weeks, cast is removed. Healing may not complete by four weeks but weight bearing starts the process of remolding. Remolding is a process in which the portion of bone that bear more stress becomes more stronger. So you may remove the cast after four weeks, and start to put weight. But avoid intense activities for at least two months. Kind Regards. Dr Adil