What is a bone callus in a metatarsal stress fracture? Well that’s what we’re talking about today on the Doc On The Run Podcast.
A bone callus is something that you may see on an x ray and it may actually cause some concern and perhaps even some problems later if you don’t really understand it, and don’t know what to do about it or whether or not you should just ignore it.
A bone callus is actually a lump just like if you rub your hands a lot if you’re digging ditches, and you get big calluses on your hand or if you look at your feet, maybe on your big toe on your heel on the outside of your foot. You may have some spots that you put a lot of pressure and friction on you get really thick calluses, which is basically just a clump of skin. Well, a bone callus is similar to how bone callus is actually a thing that forms when the bone gets injured and it happens a couple of different ways.
But a bone callus first of all is normal. But when you see it on an x ray, it may make you really worried because it looks really abnormal. It’s a lump. You can see it on the X ray. It’s a bulge in the bone and usually kind of round right around where that fracture is. Sometimes when you have a stress fracture and your doctor doesn’t see anything on the X rays, they will tell you we’re going to have you back in four weeks or six weeks and we’ll take an x ray to confirm that this was actually a stress fracture. What they’re usually looking for is that formation of a lump around where they couldn’t see a crack that signifies the bone is healing, which then later confirms you’re at a stress fracture.
There’s two reasons you really need to understand this. The first thing is there’s two kinds of callus really, and if you look it up you’ll see all kinds of confusing physiology terms, just like the fibroblasts, chondroblasts, osteoblasts, osteoclasts, you see fibrocartilage callus as a description and what happens is you get a crack in the bone you get a blood clot and then within that blood clot you get fibrocartilage developing between the two bones that creates a cushion with the cartilage and a kill. It can it’s some connections that form stability with the fibrous part of it.
So it’s collagen mostly, but that’s where those terms come from. So fibroblasts actually are the little cells that lay down strands of collagen, binding the bone together to help hold it still. There’s a whole bunch of strings holding it together. Chondroblasts make cartilage and so they formed the stiffer material that’s cushioning in between the bones that also add some rigidity to that soft callus that actually holds the bone still.
When you get that formed, that amount of cushioning instability, that kind of firm glue that’s holding you together. That usually causes a fracture to stop hurting. That’s also where a lot of people are tempted to start running and a rip it apart, and then it starts to hurt again. And you do that over and over and it causes a real problem.
So what happens here is that you get this bony or cartilaginous or fibrocartilaginous bridge between the bones and what happens is that over time, it will ossify or turn into bone. Now all of that big lump of stuff in there starts to get calcium deposit in it. That’s when it shows up on an x ray. That’s a bone callus.
The first thing is that it can be too big. So you would think the bigger it is the more stable it is and that’s sort of true, except that a really large callus in the bone often signifies too much motion in the bone. And so it’s just a sign of your body’s actually tried really hard to stop those pieces of bone from moving against one another and you get a really large callus.
You would think well, great, that’s going to make it stronger, not necessarily because that’s disorganized bone. What happens is you have a balance of these two bone cells called osteoblasts and osteoclasts that actually go and work together to one of them actually eat out a channel of the disorganized bone that’s weaker and then the next cell comes down and lays down more organized bone in a much more stable way.
So over time, those two bone cells remodel the bone to make it stronger and the callus will usually dissipate and get resorbed over time, but you may decades later see it on an x ray where there’s still a slight bulge that brings up a couple of other problems. One is that the callus is really big in your body doesn’t resorb it, it can take up space, so it pushes on other things like the interossei muscle or the nerves that that lead to a Morton’s neuroma and if it’s pushing on neighboring structures, you might get pain just because that lump of bone is pushing on other things in your foot. That can be a problem.
The other thing is that if you get one of those, and you basically treat the stress fracture on your own, you treat it yourself or you just had an achy foot after an ultra-marathon you took some time off didn’t really think about it that much but it healed on its own. You could actually have a scenario where you go in to see the doctor you have some foot pain they take an x ray, they see that long and they say up, you have a stress fracture, you can’t run and that may or may not be true because if you don’t have a previous X ray that shows that it wasn’t there before your foot started hurting, it could have been years ago that you actually got that but the bone callus actually causes a misdiagnosis as a new stress fracture when it was really an old completely healed stress fracture that is no longer a problem.
Hopefully this helps you understand a little bit more about the bone callus, how it happens in stress fractures and what it really means and whether or not you need to worry about if you see one on an x ray when you have foot pain.
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