okay now that we have a better understanding of how bones actually develop I think we can start
understanding what happens when something goes wrong and one of the main things that can go
wrong are fractures they can be fairly minor if you're talking about stress fractures or really
severe when you talk about comminuted type of fractures keep in mind two of the bone cell
types so osteoblasts are gonna play a big role in terms of fracture repair as well as osteoclasts
which will resorb portions of the bone that need to be replaced okay so we're gonna
start off talking about the four main types of fractures the first we're going to discuss our
complete fractures and these are typically the second most severe so complete fractures as you
can see you have the complete separation of two portions of bone so they're going to be completely
separated from one another these typically will occur often in the shafts of long bones
or the anatomical necks of long bones they can happen anywhere in terms of skeletal system but
typically you'll see them in long bones more often there are two types of complete fractures the more
severe type are open fractures so one fragment of the bone will actually extend outside of the
skin so those are generally the more cringeworthy ones you see at a football game where the bone is
actually jutting out obviously that's going to be a little bit more difficult and take a little
bit longer for the bones to prepare the second type of complete fracture are closed fractures
so the two fragments of bone actually stay within the skin and typically it's easier to set those
or get those two fragments back together in order for the bone to repair itself now the most severe
type of fracture are comminuted fractures and you can probably tell from the illustration why that
is anytime you have bone actually moving away from where it should actually be they're going
to still try to heal they're still going to try to move into that region so typically when you
have healing of these comminuted fractures they're never exactly the same in terms of the structural
integrity of the bone so generally you have these really large bony calluses left over
from these impacted fractures these typically happen in accidents with extreme force so car
accidents and you'll have one fragment of bone just being pushed with high velocity into the
second fragment of bone now these can be quite severe but if you see the two fragments of bone
are actually touching one another so that will play a big role in terms of being able to heal a
little bit faster however you want to immobilize impacted fractures almost immediately because
anytime that you can have movement this can actually lead for impacted fractures to become
more comminuted fractures which are the most extreme type and the last main type of fracture
are greenstick fractures and what I want you to note here is you'll have a fragment so almost a
complete fragment here but it's not complete you all you have on the other side of the fragment
is a bending of bone so if you think about the components of bone what's the the portion that's
actually going to lead to bending what's going to allow for more flexibility of the bone so collagen
so collagen is going to lead to portions of the bone actually bending instead of breaking
so this is going to occur in individuals where bone development is still occurring so greenstick
fractures are specific or almost exclusively found in juveniles so individuals where bone development
is still occurring now the name greenstick comes from its similarities to actually trying to break
a branch or break a stick so if you think about breaking a stick off of a tree or small bush and
trying to bend it or break it if it doesn't actually break into two pieces you had that
very characteristic bending which we'll have in greenstick fractures as well so those are
the four main types you can have them in any area of the skeletal system we're going to talk about
two areas of the skeletal system where you see fractures more frequently and the first we're
going to discuss is the Colles' fracture or Colles' fracture you'll here either other way either way and
these are going to be the more common and you'll have these if you're looking at this portion of
the illustration associated with your distal forearm and sometimes you can have fracture of
the carpal bones which articulate with the radius so in the Colles' fracture you're always going
to have a fracture of the distal end of the radius it can be a complete fracture it could
be an impacted fracture depending on what type of force occurs with this and this type of fracture
can happen in all age groups generally you have a higher prevalence of this in older individuals
particularly individuals with osteoporosis so if you think about if you are in the act of
falling what's one of the first things you want to do you want to protect your head and how most
individuals go about doing that is out stretching their hand so when you put your hand out you're
going to have a tremendous amount of force right in this region and that can lead to fractures of
this distal end of the radius occasionally it can lead to fracture of certain carpal bones
as well and we'll talk about the specific carpal bones later on in another discussion so this is
one of the most common type of fractures and some of the literature you'll actually hear
refer to as the most common fracture another area where you commonly have fracture is the
ankle and specifically the portion of the ankle of the distal ends of your lower limb bones so
in every Pott's fracture you're going to have a fracture of the fibula so the fibula is the
lateral of your lower limb bones and you can see a portion of the distal end we refer to
this as the lateral malleolus now a more severe Pott's fractures where you have extreme torsion
of the ankle region you can also have avulsion or the complete break off of the distal end of
the tibia referred to as the medial malleolus or medial malleolus so you'll only have this type of
fracture in the most extreme versions of Potts fractures okay so that was discussion in terms
of the four main types as well as two of the more common areas where you have fractures but
one thing I really want to get across in this discussion is how bone repairs itself one of
the common themes and in my discussions here is that bone is dynamic it's not static so bones
trying to heal itself almost immediately so let's talk about what happens right when the fracture
occurs and then we'll talk about how it actually heals itself so if one of the other things that
we've been discussing quite a bit is that bone is highly vascular there are blood vessels throughout
the entirety of the bone so if you think about if you're breaking the bone you're also going to be
breaking the blood vessels in that area so blood is going to rush out fill out fill in the area of
the fracture and then it's not going to actually move outside of the periosteum so it kind of gets
stuck in this region so you have what's referred to as a hematoma and this is where you get that
very characteristic swelling or inflammation that you have with fractures so obviously in
any type of bone repair osteoblasts are going to start secreting extracellular matrix however
in order to maintain the integrity of the bone we don't want to speed that process up too much
so instead of bone completely being replaced in this region you'll actually have an intermediate
portion referred to as the fibrocartilaginous callus so kind of a building up of cartilage in
this region to actually keep the two portions of bone closely associated with one another
and allow for the osteoblasts to secrete fully formed extracellular matrix also it's allowing
osteoclasts to break down portions of the bone that doesn't need to be there anymore so
this this callus this fibrocartilaginous callus can occur within a couple of hours that maybe not so
much a couple hours maybe five to six hours and they can extend up two weeks depending on
how severe the fracture is eventually bone will completely replace the cartilage in this region
so you'll have osteoblasts secreting osteoclast breaking down what does need to be there and the
remodeling bone can continue for years depending on the severity of the fracture so the more severe
like the communited fractures can take years and years and you can actually see evidence of bone
fractures and individuals up to 15-20 years after the fact you can have a little remnant
of that callus after the fact so this is a very natural process bone will immediately do this
however will have continuous discussions in terms of how aging is going to affect all portions of
bone specifically we'll come back in terms of how slow bone repair can happen in older individuals