 I am Dr. Steven Pomerantz and this is my colleague, Dr. Allison Griewie, and we're two ortho radiologists doing ortho MR for the greater good so that you can raise the bar as you take your recredentialing examination, your board certification, and your CAQ. So we're going to go at this case by case and we'll get right to it with associated questions that are relevant and perhaps may appear in some form on your exam. Let's start out with this 47 year old woman who had sudden onset of sharp leg pain while running one month ago. And maybe I'll handle the first question if that's okay. All right. So let's do a little scrolling here just to get you on track. We've got a T1 sagittal. We'll make that a little bigger. Got a water weighted fat suppression image. We'll make that a little bigger. And we'll put something in the center, perhaps the coronal that shows the abnormality of interest clearly. And that is another fat suppression sequence, although not quite as much fat suppression as the one on the right where the fat is very black. So what is the most likely mechanism of the obvious distal fibular fracture in this patient? Is it impaction? Is it insufficiency? Is it a fatigue fracture? Is it a pathologic fracture? Or is it none of the above? So let's start out with just the appearance of it. Unlike an acute fracture that you get from major trauma, it wouldn't usually make a straight line like this. It would kind of be jagged or regular or zigzaggy. This one has that sort of very subtle, if we blow it up, almost looks a little bit like atrial fibrillation on an EKG. And that is very typical of an insufficiency type of fracture or a stress type of fracture, both of which are overused fractures. The difference between them being that insufficiency fractures occur in brittle bone or abnormal bone and stress fractures, overuse type fractures occur in otherwise healthy bone. So what do you think is the most likely diagnosis, you know, audience? What would you choose? And, you know, this is a transverse complete fracture of the distal fibula, and the most likely mechanism is going to be an insufficiency fracture based on the fact that it's a 47-year-old woman. You know, fatigue fractures or stress fractures occur in normal bone, so I don't think that is a terrible choice. But in an osteoporotic person with some marrow pallor, an insufficiency fracture is going to make the most sense. And nowadays, the diagnosis of osteoporosis is even made with a combination of marrow pallor and a fracture seen on MR, an insufficiency fracture seen on MR. So you don't even have to do a DEXA to corroborate the diagnosis, although you might use DEXA for treatment. Sadgily, you can see some blood and some reparative tissue along the periosteum of the fibula. Why don't we try another question on this one? I'll let you have at it. This is the true-false question. So which statement is false for fibular stress fractures? Is it A, that they account for 5-10% of all stress fractures? B, most commonly occur in the distal third of the fibula? C, more frequently are seen in runners training on hard surfaces? D, most common mechanism of the fracture is due to weight-bearing compression? Or E, that they are low risk and can be managed with cessation of activity until the point of tenderness resolves? And so the answer for this is going to be, which one of these is false, is going to be that they are due to weight-bearing compression forces. Fibular stress fractures may be caused by muscle traction and torsional forces as opposed to weight-bearing compression forces. So in terms of the rest of the answers, 5-10% of stress fractures do occur in the fibula. Fibula is pretty common, even though it's not a weight-bearing bone, which is sort of weird. And they do most commonly occur in the distal third, although you can see them in the shaft occasionally. It's no secret that this should be an easy one. It occurs in runners training on rigid surfaces. And often when we bring them back into their activity, we only allow them to go on grass or on a soft track with special shoes for a while. And management is clinically, you just have them rest. And not only do you have them rest, it's probably considered a violation of the standard of care to let somebody with a completed insufficiency or fatigue or stress fracture go back to their activity until A, they're pain-free and B, you know, you see bridging. We do break these down, these stress fractures into 4A and 4B depending upon whether they involve one edge of the cortex or both edges of the cortex. Should we hit the next question? So this would be a 4B. This would be a 4B. To be or not to be, it's a 4B. All right. Which is a true statement regarding stress injuries? Nuclear bone scans have a higher specificity than MRI in identifying stress fractures. I'm not sure that anything has a higher specificity than MR, but that's kind of biased. Bone scan is the preferred imaging study for follow-up of healing due to the intensity of activity decreasing over 3 to 18 months as the bone remodels often lagging behind the clinical resolution of symptoms. Low signal fracture lines seen on both T1 and T2 images represents grade 4 injury. Earliest MRI findings of a stress injury is bone marrow edema visible on T1 and T2-aided images. And finally, stress fractures are characterized with normal radio nucleotide examinations and blood pool images and longitudinally oriented areas of increased radio nucleotide accumulation on delayed images. Well, let's start out with A. A is false. MR has a higher sensitivity and specificity than Centigraphy for identifying stress fractures. Bone scans are highly sensitive, but they're not all that specific. I mean, you just get a glob or a hotspot, as we well know. B is false. Bone scan is not followed up for healing because the intensity persists forever and a day. And it's also not a good idea to give a young man or woman 3 or 4 millisieverts to the testes or ovaries on a repeated basis, unless you don't like them. And even then, it's a bad idea. C is the correct answer. A low signal fracture line is seen on both T1 and T2-aided images. And the more chronic it is, the lower it will appear because it gets sclerotic progressively over time. D is false. The earliest MRI finding of a stress injury is periosteal edema and bone marrow edema visible only on the water-weighted sequences, especially the fat-suppressed PD spur or any really fine fat-suppressed sequence. And finally, E is false. Normal, scintographic images on any phase and longitudinally oriented areas of uptake occur in lower grades of stress phenomenon, whereas transverse areas of uptake are typical of an actual fatigue or insufficiency fracture. Want to take the last one? Sure. Stress fractures with risk for delayed union include the following except A, the talus, B, medial malleolus, C, navicular, D, fifth metatarsal base, and E, calcaneus. So all of these have a risk for delayed union except the calcaneus. I wonder why that is. I don't know, do you? I don't really know either. Yeah, you would think if you're walking on your calcaneus all the time that it would have trouble healing. Now, being an old codger, an old guy doing MR, and you're a young gal doing MR, and I have seen quite a few base of the fifth fractures that just have not healed, kind of in a pseudo-Jones or Jones fracture configuration. I've seen several medial malleolar fractures that haven't healed, but honestly, that dialed into the fact that the calcaneus is the one that is at greatest risk for delayed union. A couple of other tidbits here. Low-risk fractures include the post-romedial tibia, the metatarsals, the cuboid, the cuneiform, the fibula, the medial femoral neck, and the femoral shaft and pelvis. And then just regarding kind of for the clinical management of this, how long will this be a sclerotic line there or the dark line persist? And if a clinician calls asking, when can I let this person go back to actually performing their activities? Is it just when they're pain-free? Do you have to do follow-up imaging? Are you looking for a resolution of edema? Yeah, it's a really important question. I think it all boils down to pain. So you don't even really have to rescan them if their pain goes away. Unfortunately, with these more chronic fatigue or insufficiency fractures, they build up so much tissue and pressure in the periosteum that it often takes longer than the typical six to eight weeks for them to get back to their activities, which are repetitive. So I've seen them take up to a year to actually go back to, say, half-marathon running or 5K running. So it can be a particularly problematic lesion. I would only rescan them if they're not improving in the six to eight-week timeframe, because then you're looking for a mal or a non-union. And I never treat the MRI. You ask how long that line would persist. The line will persist for up to a year. And eventually, you'll see bridging of the cortex on both sides. You may see the white signal of the medullary tissue wipe away the line, or you may see a little delicate dark scar persist throughout life. So you may be able to tell 10 years later that there had been an insufficiency or fatigue fracture there. Shall we do another one? Sure. That was great.