okay in this video we're going to talk about bone repair uh so bone repair is a consequence of some sort of damage right so fractures are going to be a type of damage to bone that are caused by breaks right so during youth most fractures result from some sort of form of trauma but in old age you know fractures can result from a weakness of bone due to age related thinning or osteoporosis now in terms of the classification of breakes there's really three questions we can use to address how the break is classified uh so we want to know the position of the bone the completeness of the break and whether or not the skin is penetrated by that broken bone so for the position of the bone there's basically two positions it can be in it can either be non-displaced or displaced if it's non-displaced we're saying that the ends retain their normal position so that the Bone's in its normal aligned position within the joint with respect to other bones and tissues around it displaced means the ends of the bone are out of normal alignment and this could be due to Joint derangement where essentially the bones may be displaced from their joint and uh out of their normal position so we would use these terms to describe the position of the bone itself now in terms of completeness of the break we can also subdivide this into two major States complete versus incomplete a complete break is one which is the bones broken all the way through so we're saying that you now have two separate pieces of bone that are separated by the break itself and an incomplete break or fracture is where the bones not broken all the way through this might just be where there's a fracture that extends into the bone but doesn't separate any pieces now uh the third question here is whether or not the skin is penetrated and we can say that the Skin's going to be either open or closed right so if it's open we call it a compound fracture this is where the skin surface has been penetrated and there are fragments of bone that are protruding through the skin surface um and are now visible um above the skin now a closed fracture is also called Simple this is where the skin surface is not been penetrated you know this is not to be confused with maybe there are bone fragments within skin but if the skin surface is not penetrated and that barrier is not compromised then we call that a closed or a simple fracture so we can also describe the fractures based on their location their external appearance and just the general nature of the break as well although these are the three major uh categories we can use to describe the the type of fracture or break so what we see here then are common types of fractures uh this one here is called commuted so commuted is when you have lots of bone fragments that are in lots of tiny little pieces and this is common in the elderly who whose bones are more brittle so you find that a combinated fractures where you have lots of tiny little uh loose pieces of uh bone uh due to that fracture or break now a compression fracture is where the bonees actually crushed and you can see here along the spine where in the in the body of the vertebrae here if it's been crunched together we would call that a compression fracture this is more common in Porous bones you know ones that are osteoporotic or and subjected to extreme trauma like in a fall but if you look at the body of a vertebrae you know in cross-section you'd find that it's actually mostly spongy bone which is why these are more commonly going to have compression fractures spiral fractures are those which you know the fracture just kind of spirals longitudinally around the bone it's a common Sports fracture due to like twisting of the of a limb you know in a fall of some sort or if your limb gets trapped uh in some way now uh it's a ragged break where you have excessive twisting forces that are apply to the Bone which is why the fracture kind of spirals around the length of that bone now epipal fractur is where basically the diaphysis and the epiphysis separate and this typically occurs along the epiphysial plate or even in the epipal line and it actually occurs with the cartilage cells are dying and calcification of the Matrix is occurring because calcified carage is weaker than bone this is a kind of a weak point in long bones so you're going to find that epiales are more common in children and adolescents whose bones are still growing at the epith thesales fracture is basically where you have a broken bone that's pushed inward you know typical of a skull fracture so you have a little divot or indentation in the skull in a green stick fractures where the bone breaks incompletely you know it's called green stick because it's almost as if you know the Bone's breaking like a stick that's not totally dry yet you know have you you break that stick but it doesn't separate into two separate pieces right there's still pieces that connect the stick together that's kind of like how these bones might fracture in children whose bones are relatively more organic and more f ible so you'd find then that only one side of the shaft will break while the other side bends so it's still kind of stuck together here that's why we call it a green stick fractur so again they're more common in children now in terms of uh treatment of bone fracture you know it's going to be aimed at reducing uh the amount of movement and realignment of the broken ends so a closed reduction is where the physician manipulates the correct position and an open reduction is where we have surgical pins or wires that secure uh the ends of those bones now immobilization is can uh be achieved by a cast or uh you know other forms of traction that are needed for healing and time's needed for repair But ultimately depends on the break of uh severity of the break right so we're saying that you know not all bones heal at the same time span and not everyone uh heals at the same rate because it's age dependent and also you know what which bones are broken so in terms of bone fracture repair uh it actually occurs in four major stages here uh the first stage of fracture repair occurs almost immediately with the hematoma or blood clot we know we learned how bone is highly vascular so that when it breaks blood vessels will also break or rupture blood's going to kind of leak out into spaces which can lead to a hematoma uh we also get a fibrocartilaginous callus that can form next so that the blood clots converted the cartilage fibrocartilage then that fiber cartilage is actually turned into uh bony material bony callous and then we have bone remodeling that that occurs for weeks and years uh sometime later so the first stage here is hematoma formation this is where we have torn vessels that Hemorrhage and when they Hemorrhage you know basically it's bleeding into a space forming a mass of clotted blood called the hematoma this hematoma sets the stage for repair because you have growth factors that are nearby uh it's prevents the additional bleeding and it forms a nice substrate for cells to invade and start to replace that blood clot with fioc cartilage so you find those is in this stage is that the site is going be swollen painful inflamed but also weak because blood clots are not strong so you know the hematoma here um is the first stage of bone repair but the bone is still going to be weak at the side of fracture now you can see here what the hematoma would look like you know first of all you have a hemorrhage of these blood vessels when they're ruptured they're going to bleed out and because of the periosteum that blood should be contained within this space here so it prevents too much blood from leaking out into adjacent tissues because the periostium can kind of hold it and contain it within this cavity now it's going to clot based on normal clotting mechanisms forming a more solid mass that is going to be soft but it's also be inflamed and tender because of a lot of you know nerve fibers here and we're also going to get an inflammatory response where immune cells come in and they start to clean up debris in dead cells now the second stage here is called a fibrocartilaginous callus this is basically where new capillaries or new blood vessels grow into the hematoma or blood clot immune cells like ftic cells can clear out the debris and then new fibr blasts come into the tissue or the the hematoma here and they start to secrete collagen fibers that span the break and connect broken ends of the bone remember collagen is a very tough protein and uh what happens next too is that fiber blasts come in and actually turn this hematoma with lots of collagen already in it into fibrocartilage so that way what happens then is that we get the Reconstruction of bone from the fibrocartilaginous standpoint and it secretes cartilagenous Matrix and this sets the stage for uh osteoblast to come in and also convert this into bone so the fibrocartilagenous callus is going to basically be where the hematoma is converted to fibrocartilage stabilized by lots of collagen fibers here this is obviously going to be stronger than the hematoma um however you know it's not going to be as strong as bonees so again this is still going to be weakened at the sight of injury you have new blood vessels that grow in and basically uh you know Supply blood to the healing tissue phagocytic cells come in here as well and also help to clean up debris and um what happens too is that osteoblast can begin to invade and convert this uh into oous tissue in fact and when that occurs to a greater extent what we find then is that a bony callus can form so within one week new tcul appear and you get a fibrocartilaginous callus that uh you know is there however this callus is converted to a bony hard callus of spongy bone because osteoblasts come in and they convert that cartilage into bony tissue this bony callus formation continues for about two months until a firm Union occurs so what happens then is that even up to two months after the break this the bones going to be still weakened at the side of injury so this is what the Bony callus would look like you see that their spongy bone is replaced where the fibrocartilage had had been now uh The Next Step here is bone remodeling we talked about bone remodeling in in the last video we said it's a lifelong process and it's dependent on how you use bones that even continues with bone breaks so what we find then is that once the Bony callus is formed we still get bone remodeling where excess material um in the diaphysis and medular Cav is removed but it's all based on the needs of that bone compact bones laid down where the reconstructed shaft um needs to occur because again because of uh you know tension and uh compression forces would promote the formation of compact bone there and then the final structure should resemble the original structure as well as the surrounding bone because it responds to the same mechanical stressors so one thing that's important to note about bone remodeling then is it's dependent on how you use bones so uh the sort of a new philosophy then with with bone repair is that you want to be able to have individuals that have had a fracture be able to use their bones as much as possible in order to you know promote proper healing and remodeling of that bone to uh you know eventually have the bone reconstruct into uh you know an effective bone so what here what we see here then is basically where the bones remodel you can see that it looks much like the surrounding bone and tissue you see that excess spongy bonees been removed here in the medular cavity compact bones been laid down on the periphery and this process of remodeling occurs on the order of years so just to summarize this process remember we have four major steps we have hematoma which is the blood clot fibrocartilaginous callus where that hematoma is converted to fiber cartilage bony callus where fiber cartilage is converted to spongy bone and then bone remodeling which occurs over the course of years and it's where uh basically the new bone is remodeled in a way that best suits how this bone is going to be used now in terms of Developmental aspects of bone uh we can actually make pretty decent predictions about uh the rate of oifc in fact we can look at how bones of aifi to determine age this can be determined by x-ray or sonograms because ocation occurs so predictably that you can look at the rate of ocation or the degree of it to know at what stage of fetal development you know they're currently in so most long bones begin aify by 8 weeks and the primary oif centers develop by week 12 now uh in terms of birth to Young adulthood we see that at Birth most of the long bones are aifi except for the epiphyses remember we have the secondary oifc centers that begin to grow later in fetal development but they're not fully formed at Birth so the epiales though persist through childhood and Adolescence because this is the site of new interstital bone growth or lengthening and by about age 25 most of your bones are completely aifi so you say that all skeletal growth ceases but this should not be mistaken with skeletal repair and uh remodeling uh essentially what we find is that by age 25 you don't get growth lengthwise there's no more interstial growth so someone's not going to get taller after age 25 or so on average but bones can still Remodel and reform based on the demands you place on them remember spongy bones replaced every several years Kack bones replaced about every 10 years so what this is showing is basically the bones of a fetus and you can see that um you know at week 12 most of your long bones have started to aify however a lot of other Bones still aren't present you can see that that there's not really much bony material here in the knees or the wrists you know uh the vertebrae aren't completely fused the hip bones haven't haven't aifi yet there's really not much bones in the feet either uh but this is again only at week 12 this is only several months in field development and you think about it it makes sense though how you don't want bones to be fully aifi because uh you know labor is you know a challenging process and so we don't want our bones to be fully rigid by the time the fetus needs to pass to the birth canal so it's important then that some modification occurs before birth but that it's not totally complete that way you know the skull can kind of change shape as it passes through the birth canal and the limbs are more flexible as well because they're not fully aifi now in terms of other age related changes in bone we find that in children adolescence bone formation exites resorption so that males uh also have a tender a greater tendency towards a thicker sort of uh bone mass than females but again that's just on average and um but in young adults both are pretty well balanced so you find then that bone resorption and break and uh and deposition are well balanced however uh in adults and as we age bone resorption exceeds formation and eventually our bones become brittle but one way to prevent excessive bone resorption is just use those bones right there's this adage in biology you use it or lose it and if you're using your bones throughout adulthood you're going to prevent resorption and therefore prevent the weakening of Bones now bone density changes over lifetime are largely determined by genetics so we find then that you know osteoporosis can you know run in families and it can relate to vitamin D metabolism and in individuals vitamin D uh usage early on can tell us about the risk for osteoporosis later uh bone mass and mineralization and healing all decrease with age beginning in the fourth decade so the fourth decade is your 30s and uh except for the bones of the skull we find that bone loss is greater in uh whites and in females so especially white females are be more prone to osteoporosis but again one way to prevent osteoporosis is adequate diet right so getting enough calcium and vitamin D in your diet preventing inflammation because inflammation promotes resorption and also using your bones because if you use them you don't lose them and the cell is going to promote deposition