|MadSci Network: Medicine|
Dear Abida, The average broken bone (fracture) takes about 6 weeks to heal, some more, some less, depending on where the break is and how serious it is. The good news is that when bones heal, they are usually at least as strong as before the break, if not a little stronger. What a cast does is keep the broken parts very close together and not let those parts move during healing, like when you glue something and you have to keep the parts from moving until the glue hardens. The reason for this is that healing goes through a couple of stages. First, bone cells come to the rescue and secrete what is called a fracture callus, which is a somewhat soft and flexible protein "patch", into the broken part. Only after this forms can the hard, white bone mineral precipitate into the callus, forming the first genuine bone and joining the broken surfaces strongly back together. Over the next few months, that first bone will get remodeled. That is, it gets eaten a little at a time by special bone-resorbing cells, then new bone gets laid down in which the protein fibers are lined up like the grain in wood, forming the final, "lamellar" bone. So the answer to your question depends on how serious the fracture is and which bone is broken. If you break a toe, for example, usually there is no treatment at all. You just limp around for a while and the bone heals by itself. In some fractures, the bone parts get displaced and need to be set, this is, moved back together in their original position, like when you put pieces of a broken cup back together as closely as possible when you glue it. The smaller the space that needs to be filled in, the faster things heal. If the bone can move during the healing process, which after all, most bones do, like arms, legs, back, shoulders, hips, knees, wrists, and so on, there is a danger of ripping up the newly-forming fracture callus, and then you have to start healing all over again. So a cast keeps the set bone or bones immobilized while they heal. There is nothing magical about a cast. Bones can heal just fine without one, so long as the bone is kept from moving while it heals. If an injury occurs where no treatment is available, the bone should be set so the parts are where they belong, an then the person should be kept still to prevent any movement of the set bone. A temporary wrapping, or a sling or splint of some kind is sometimes enough for that purpose, at least until medical care becomes avaialable. But some fractures involve bones being splintered, or broken into little pieces, or the fracture occurs in a joint where bones move against one another. Then things get more complicated, sometimes requiring surgery with little screws and strips of metal to put the pieces back together while things heal. That kind of injury is difficult to do much with if medical care is not available. If major fractures don't heal properly, they can cause serious disabilities, like crooked legs, joints that don't work right, jaws that can't chew, and so on. So good first aid and proper medical attention can make a tremendous difference in whether a fracture leads to long-term trouble for the victim. I hope this answers your question. Paul Odgren, Ph.D. Department of Cell Biology University of Massachusetts Medical School Worcester
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