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Identifying Sacral Insufficiency Fractures: Pain Patterns, Physical Exams & Imaging
Sara Stewart • Updated Feb 19, 2025 • 32 hits
Sacral insufficiency fractures are a type of fragility fracture of the sacral spine most commonly seen in elderly patients with osteoporosis. They are a frequently overlooked cause of low back and pelvic pain, with nearly 25% of cases missed in clinical practice. Diagnosing these fractures can be particularly challenging due to their subtle imaging features and overlap with other conditions like SI joint dysfunction. Pain patterns frequently mimic L5 or S1 radiculopathy, further complicating diagnosis. Thorough physical examination and imaging is critical in patients with sacral insufficiency symptoms because with proper diagnosis, early intervention with sacroplasty can reduce pain, prevent instability, and improve patient outcomes.
Interventional radiologist Dr. Douglas Beall explains how to identify sacral insufficiency fractures, interpret imaging findings, and overcome diagnostic challenges. This article features excerpts from the BackTable MSK Podcast. We’ve provided the highlight reel in this article, and you can listen to the full podcast below.
The BackTable MSK Brief
• Sacral insufficiency fractures are underdiagnosed due to overlapping symptoms with other conditions causing sacral pain like SI joint dysfunction.
• Pseudo-radiculopathy, a pain pattern characterized by groin pain and radiating discomfort along the outer thigh and into the foot, is common in sacral insufficiency fractures.
• Many sacral fractures are missed on plain radiographs, making advanced imaging techniques like CT and MRI essential for identifying subtle cortical disruptions and increased STIR signal that can lead to proper diagnosis.
• Physical exam tests such as the sacral thrust, FABER, and Fortin finger test can provide diagnostic clues for sacral insufficiency fracture, especially in combination with imaging findings and high clinical suspicion.
Table of Contents
(1) The History of Sacral Insufficiency Fracture Diagnosis
(2) The Ongoing Challenge of Sacral Insufficiency Fracture Diagnosis
(3) Recognizing Pain Patterns in Sacral Insufficiency Fracture
(4) Detecting Sacral Insufficiency Fracture on Imaging
The History of Sacral Insufficiency Fracture Diagnosis
Sacral insufficiency fractures remain underrecognized despite being relatively common in older populations. Historically, these fractures were poorly understood and rarely diagnosed, with initial descriptions emerging only in the 1980s. Advances in imaging technology, such as CT and MRI, have improved detection, but many clinicians still overlook the subtle signs that indicate a sacral insufficiency fracture. Proper identification requires vigilance in evaluating the sacral region on MRI scans, particularly when signal changes are present near the sacroiliac joint.
[Dr. Jacob Fleming]
One of the other things I'm very passionate about having trained with you is finding those orphaned conditions where patients are often left without treatment, and hence the topic of our discussion today, which is sacral fractures and particularly sacroplasty. We'll just jump right in with the haymaker. Where are we with treatment of sacral fractures? We as in the larger medical community, how are we doing taking care of these patients?
[Dr. Douglas Beall]
I would say we're nowhere close to where we need to be. Not even close. Let's compare the experience we have now in your status in life in terms of where you are versus what it was when I came out. Shortly after the earth cooled, I finished my residency, and that was in the late '90s. I'm going to talk a little bit about some of the history of sacral insufficiency fractures or SIFs and a little bit about sacroplasty. When I came out, it was in 1988 is when I got out of residency. Sacral insufficiency fractures were described when I was in college.
It seems hard to believe, but Lourie did the first description of sacral insufficiency fractures in 1982. This was something that was just completely not recognized at all. We know that the CT scanner came out in the '70s. In the '80s, we had MRI, but people weren't experienced enough or hadn't had enough exposure to some of these fractures that are difficult to see to even describe them. It seems I can't quite fathom the fact that it was so late in terms of the ability to diagnose sacral insufficiency fractures. If you look at it, you understand why.
You look at sagittal views, and people really focus on sagittal views of the MRI lumbar spine. You've got to watch the corners because down at the bottom, any time you have disruption, increased signal in STIR, decreased signal in T1 to the bottom of the corners, that is not normal. It's difficult to see primarily because a lot of times the axial scans don't go far enough south or inferior.
The SI joint has an increased signal. It can have fluid in it. It can have cartilage, articular hyaline cartilage in there. It can mimic. It can have signal heterogeneity. You just gloss over the fact that the sacral insufficiency fractures, which may be subtle in terms of their signal, you can gloss over that. Oh, that's the SI joint. My mind doesn't recognize it, so my eyes don't see it. You miss these things fast and slow.
The incidence of these fractures, the best data I could get for incidence of fractures, having just finished the teaching curriculum for the Stryker course on how to do this, was between about 4.4% and 12.4%. That's quite a bit. It's a fairly common fracture in people that are 75 years old or older. As much as we think we're really good at recognizing these fractures, I can tell you that we still aren't great at recognizing these fractures. What happens after you do recognize the fractures?
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The Ongoing Challenge of Sacral Insufficiency Fracture Diagnosis
Diagnosing sacral insufficiency fractures remains a persistent challenge, with nearly 25% of cases going undetected. A key diagnostic hurdle is distinguishing sacral insufficiency fractures from other sources of sacral pain, such as SI joint dysfunction. Even when the diagnosis is made, few patients receive appropriate osteoporosis treatment to prevent future fractures. This combination of missed diagnoses and untreated underlying conditions underscores the urgent need for continued education and greater clinical vigilance.
[Dr. Douglas Beall]
The first sacroplasty description was made in 2000 and that was done by a guy named Marcy. This was done with sacral mets, metastatic disease to the sacrum. 2000, it seems just unfathomable but it really was true. Because I wasn't doing a lot of sacroplasty. I had done sacroplasty before the year 2000 but not a lot. As soon as we started seeing more and more of these, I started doing more and more of these and it was still uncharted territory. This was something that I started doing, just like 95% of the things I do today, I never was taught to do in residency or fellowship. That's not abnormal. That's the normal course of things. You have to keep on learning.
The best thing that you can do is to teach somebody how to learn new things. You could adapt your visual, spatial skills and perfect those and really understand the anatomy and the do's and don'ts and the general rules. You can quickly and effectively learn new techniques. These new techniques have really been acquired in the last 24 years since that original description. These are things treating sacral fractures as much as we've improved. We have improved.
We have improved treating sacral fractures. Still, if you look at the number of times these things are missed, statistically, it's going to be about 25%. For radiologists, the real number is 23.5%. 76% of other physicians, non-diagnostic-related physicians, will miss these things. We're still missing fast and slow. If this isn't a compelling enough story, a compelling enough case that we need to do better, how many people are treating underlying osteoporosis after fixing vertebral compression fractures? How many times have we seen this?
You've been with me for a year. I'd be interested in your-- We've seen hundreds of fractures, vertebral, and we've seen, oh, I don't know, probably 40 sacral fractures or something like this. How many times were these people already being treated for their underlying osteoporosis by someone else by the time they came to us? What do you think? What is a good guess number? I know we don't keep track of the answer to this.
[Dr. Jacob Fleming]
Somewhere in the range of 0% and -5%.
[Dr. Douglas Beall]
It sure seems like that. The demoralizing component puts it into the negative, I think. It sure seems like that. There's hardly anybody being treated for it. We've got a long way to go. This is one of these things that I can't really fathom how long we have to go. We have hip fractures in the early 2000s. Only about 22% of the patients were treated for that. It went down to 11% by the year 2011. This was after an anabolic bone agent, teriparatide, called Porteo, made by Lilly, was introduced. November 2001 when it was approved. Then April 2017, we had another anabolic bone agent, Tymlos, abaloparatide. Then April 2019, we had romosozumab, Evenity.
We now have three anabolic bone agents. These people get sacral fractures. We had somebody in here that that had SI pain just this last week or the week before, somewhere in that range. She couldn't get out of a chair. That doesn't really worry me very much but she's really tender. Her pain didn't seem to be with sitting. It seemed to be with movement and transition, and so didn't really see anything that had to do with sacral fractures. The transitional pain, standing to sitting to lying, getting up and moving around, comfortable as long as she wasn't moving.
Sure enough, we sent her for a CT scan and she had subtle but present and accounted for sacral insufficiency fractures that had been missed over the course of time. I think this is a combination of vigilance, knowing that they're there, especially after pelvic radiation. People after pelvic radiation, high rate of fractures, and 80% of those fractures in the pelvis will occur in the sacrum. This is something that should occur at the elderly patient. I bring the original patient up because she was somewhere in the range of 65, 66, maybe even a year older than that.
She wasn't 85 and I told her that this is something we typically see in 80, 85-year-old, then Caucasian females in Northern European, et cetera, people that otherwise have a biogenetic predisposition for sacral fractures. It's abnormal, whatever the reason, she had multiple factors which were beyond the scope. Nevertheless, it's something that raises the level of importance for treatment, raises the level of importance for vigilance. Just that little clinical scenario is something that really, hopefully, will stick with us both to know the difference between SI pain and sacral insufficiency fracture pain, even though they're about a few millimeters to a centimeter distance from one another.
Recognizing Pain Patterns in Sacral Insufficiency Fracture
Recognizing the pain patterns of sacral insufficiency fractures can be difficult, as they often mimic other conditions like SI joint dysfunction or sciatica. Patients may present with pelvic girdle pain, low back pain, and posterior hip pain. However, what is most consistent with sacral insufficiency fracture is pseudo-radiculopathy, typically resembling L5 radiculopathy, with pain radiating from the groin down the outer thigh, across the knee, and into the foot. This pain arises from irritation of the lumbosacral trunk due to pelvic movement or bony disruption from the fracture. Early recognition of these patterns, paired with sacroplasty and proper osteoporosis management, can significantly improve patient outcomes.
[Dr. Douglas Beall]
When people present with SI pain inlet sacral fracture pain, they'll commonly present with, yes, pelvic girdle pain, yes, low back pain, yes, posterior hip pain, but it is really common to get an L5 radiculopathy, and variant of L5 radiculopathy means pain in the groin and then pain that radiates down the outside of the thigh, over the top of the knee, front of the leg, to the top and bottom of the foot. That is an L5 radiculopathy and of course, you can add certain variations, it can affect the S1 or the L4 but mainly it's an L5 and this is a pseudo radiculopathy, pseudo sciatica because it's just being irritated. It's being irritated by that lumbosacral trunk.
That's one of the things with it, a stretch, movement of the pelvis, bony anatomy with irritation that either comes from sacral pelvic dysfunction, SI joint dysfunction, or a fracture of the sacral ala, you can have a pseudo-radiculopathy. I've heard people say it can't be a sacral insufficiency fracture because a person has sciatic. Whoa, be careful, watch out for that because that does not mean that.
In fact, you hear some of our receptionists talking to the patient and they'll ask, "Do you have that wraparound pain and you have that pain down your leg?" They don't know that you're not supposed to have sciatica or sacral fractures, but just talking to enough people with thoracic pain, thoracic radiculopathy around the ribs, sacral fractures, or sciatica down the legs, they've suddenly become expert in this.
That's what happens when you talk to a lot of people and get a lot of feedback on that. That really, it plays out well and you understand you get a good understanding of the pain pattern or presentation and most importantly, you're not don't have a lot of influence by your colleagues telling you this can never happen, that can never happen, stay away from this, stay away from that, don't use this, don't use that. That's one of the worst things that can happen and I think for sacral insufficiency fractures, the best thing that could happen is a sacroplasty followed by treatment of the underlying disorder of osteoporosis.
Detecting Sacral Insufficiency Fracture on Imaging
Detecting sacral insufficiency fractures can be especially challenging due to their subtle imaging features, which often go unnoticed on plain radiographs. These fractures typically require advanced imaging for confirmation. CT scans can reveal subtle cortical disruptions and trabecular abnormalities while MRI may show increased STIR signal, although fractures can occasionally lack this finding. Clinicians should maintain a high index of suspicion, particularly in patients with unexplained low back or pelvic pain, and combine imaging with physical examination tests such as the sacral thrust, FABER, and the Fortin finger test to refine their diagnosis. Early intervention with sacroplasty can reduce chronic pain, restore function, and improve long-term outcomes in patients with sacral insufficiency fractures.
[Dr. Jacob Fleming]
It's very difficult, I think, clinical diagnosis when it's not on your plate of what you're thinking about. For some reason, it's just commonly not. Even for us, it's not the first place where we go with diagnostic criteria that we're thinking of. We actually put that patient on the table, on our fluoro table, and had a look just because the suspicion was so high. As we know, most sacral fractures are not really apparent on radiographs, but it demonstrated the difference between reading a study blind and looking at your own patient who you know what you're looking for. We did see some subtle cortical disruption that sealed our suspicion. We sent the patient for CT.
I think that commonly, this is just not thought of by the first-line diagnostic physicians who are involved in this. A lot of these patients have at least gone to the ER once, if not more, and these can often get glossed over. As you said, a lot of times, it's very subtle. A lot of times, I feel that we just see the trabecular disruption on the CT. MR, of course, you may see increased STIR signal, that's the thing we look for, but you can have fractures without much STIR signal as well, right?
[Dr. Douglas Beall]
These fractures are notoriously difficult. There's no way that we would have seen them had we had a high level of suspicious to see them. Looking at that and finding the little cortical disruption, that it's one of those things very hard to see, but once it, you can't unsee it. It's there, it's there, it's there, and sure enough, it was there on CT scan.
You see what you look for, you look for what you know, and that saying is based on Nobel Prize-winning data from Elie Wiesel in the '70s, but that really is, the visual cortex and the neocortex are related, and once it, once it, you have to be able to recognize and know what you're looking for to actually be able to see it literally. You have to be able to see it figuratively as well.
These are things and things like this will commonly get missed in physical examination tests for this, physical examination tests for SI pain, the sacral thrust, sacral compression, Gaenslen's, Patrick FABER's test, and the distraction test. These are in addition to things like Fortin's finger test. These things are positive in patients with sacral fractures because the lines of force go vertically up and down through the sacral ala.
They typically affect S1 and S2 predominantly, a little bit of S3 commonly, and then the force across the body of S2 is the side-to-side force and these things will transmit down, as you know, based on the biomechanical data, down through the superior and inferior pubic ramus. That's why you have sacral fractures associated with pubic rami fractures and the first thing we have to do is look at pubic rami and scour the rami to make sure they're not fractured as well because that provides additional instability in the pelvis and just cementation may not be enough.
The trauma literature says that any gap in a sacral fracture of about 10 millimeters, 1 centimeter or more, and you really probably should be using hardware as well. In my experience, these are not the same. You can't apply trauma rules and requirements to osteoporotic fractures. We try to because we don't really have enough data there for sacral insufficiency fractures, so we do apply that. Now, anything more than about a centimeter or more in terms of a hypotrophic, oligotrophic nonunion, a gap after a sacral fracture, we will go ahead and add screws, as you know, as you have done, and we've seen a good amount of success to this.
We count a low threshold to adding screws anyway because that's what we do for other sacral pelvic pain scenarios such as SI joint dysfunction and it's fairly easy to do. We have a low threshold to do that. Do we do it too much? I hope not and I surely don't think we do, but that's applying an L1 burst. If grandma falls down from a standing height, she has a fracture that's medial, laterally, and anteroposteriorly bigger than a level above, a level below. What is it? It's a burst, but we don't hesitate at all to treat it with standalone cement, just vertebroplasty, kyphoplasty, and now Spinejack, of course, but we've treated this for years.
It's very different from a high-velocity injury where you drive your car to a bank on I-35 and disrupt your PLL and have a traumatic burst. These are very different things and I think the same thing applies to the sacrum. It's very different than a motorcycle injury with a sheer force, using the scale to figure out exactly the mechanism. These are different issues. These are more traumatic issue.
I think we have a long way to go. I think we really need to have the ability to do sacroplasty. One of the things I see commonly in our registry and enrolling people for sacral fracture fixation is there are not very many people doing this. In our state, I think there are two people doing sacroplasty. I think my former fellow and us, three all together, soon to be two, but it's just not the number of people that do this. There are not nearly as many people that do sacroplasty as that do vertebral augmentation. That's a real travesty. One of the things that we have seen is that this is one of the best things that not only the people can do but that is dark.
The mortality rate for sacral insufficiency fractures and the common things that we use in terms of pain and debilitation. I'm going to go back a half step and here's what happens when we don't recognize and treat them, the one, three, or five-year mortality rates for sacral insufficiency fractures and this is, I'm going to quote some data. This is from Chandra, who did the best systematic review on that analysis on sacral insufficiency fractures and the classic paper, here's what happens if you don't treat these people that have sacral fractures. The one, three, and five-year mortality rate ranges from about 11.5% to 23.5% to almost 27% in one year, three years, and five years.
If you don't treat somebody with a fracture, by the time you hit a week, the bone loss goes up to 50 times normal bone loss and it's age-related, 50 times, which is crazy. At about the two-week time point, you're cracking along at about, you lose 10% to 15% of strength every week that you're down, and by the time you hit two weeks, about 10 days to 2 weeks, you're at about equivalent to a 10-year loss, age-related loss in conditioning, bone and muscle. By the time that you're five to six weeks out, you're half as strong as you once were. That's just incredible to me. You put a young guy down, 20-year-old male, and the bone loss is very swift, too. If you measure the calcium goes up, bone loss goes up, and this is something that happens in younger patients too.
It's just more debilitating in older patients because there's no reserve there. You get the idea that if you thump them too hard, they lose their grip on the edge of the sink and go down. This is not something that they can or should or have to withstand. By the time these people are discharged, the data is half of them can't be discharged at the level they once were when they came in and 40% of them will have chronic pain. 40% will have chronic pain. Just can't imagine that. There are people that would advocate for non-treatment because it's too risky to do treatment, too risky, too risky, and too risky.
[Dr. Jacob Fleming]
Too risky is the lack treatment.
Podcast Contributors
Dr. Douglas Beall
Dr. Douglas Beall is the Chief of Radiology Services at Clinical Radiology of Oklahoma.
Dr. Jacob Fleming
Dr. Jacob Fleming is a diagnostic radiology resident and future MSK interventional radiologist in Dallas, Texas.
Cite This Podcast
BackTable, LLC (Producer). (2024, June 19). Ep. 51 – Sacroplasty I: Principles & New Data in the Treatment of Sacral Insufficiency Fractures [Audio podcast]. Retrieved from https://www.backtable.com
Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
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