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So in this next segment we're gonna consider sacral

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insufficiency fractures which can present

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to the emergency department

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because they are a common cause

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of very debilitating back pain in the elderly.

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About one to 5% incidents in that at risk population

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and they're often severely painful.

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The diagnosis can be delayed

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as the symptoms are non-specific

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and they may mimic other entities that cause low back pain.

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The typical risk factors are osteoporosis,

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somebody who's had radiotherapy to the pelvis, people

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with chronic renal osteo dystrophy

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and underlying uh, inflammatory arthropathy such

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as rheumatoid arthritis, either from the primary disease

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or in combination with steroid exposure

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and at risk for osteoporosis.

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So with regards to the sacrum,

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they often get these insufficiency type fractures

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as their form of stress fracture.

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So an insufficiency fracture is

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where you have a stress fracture from basically normal

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that is physiologic

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or perhaps slightly super physiologic stress

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or force applied to abnormal bone.

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If we break up the sacrum into the three zones

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as shown here, one is the most lateral next to the SI joint

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two is more central where you have the sacral foramina,

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and three is a median portion over the vertebral bodies.

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The insufficiency type fractures most commonly

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involve zone one.

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They can be unilateral but not unusual to be bilateral.

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In addition to this vertical component,

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there is often a horizontal connecting component

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and they have a high incidence

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of other concomitant pelvic insufficiency fractures such

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as within the pubic ram eye

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or adjacent to the synthesis pubis.

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So the symptoms they present

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with this diffuse low back pain, there may be some radiation

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to the buttocks, hip and groin.

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Typically the pain does not go below the knee

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to distinguish it from radicular or sciatic type symptoms.

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There may be tenderness to palpation and

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because the lumbosacral plexus does course

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along the anterior margin of the sacrum in the region

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of zone one, when you get a fracture there,

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it can cause inflammation

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and irritation along the lumbosacral plexus,

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particularly the L four

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and L five trunk contribution to the plexus.

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And so they may present with more radicular symptoms as well

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on imaging with radiographs.

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They may present with a vertical sclerotic band parallel

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to the SI joint.

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Uh, once they're a little bit more chronic.

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Again, initially there's a fracture line, but either

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because of overlap of the trabecula

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or part of the reparative process,

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they may develop this band of sclerosis.

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However, the radiographic findings are gonna be late

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and not sensitive

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to these lesions when they present. More acutely

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CT is more sensitive showing sclerosis

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and actually the cortical disruption.

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But sometimes that can be subtle.

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So the sensitivity for CT is about 60 to 75%.

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And then, uh, bone scan using uh, technetium

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will show an area of increased uptake

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and it will show that configuration of one

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or two vertical lines potentially connected

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by a horizontal component which has been

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termed the Honda sign.

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MRI, similar to bone scan, would show those findings

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with increased T two signal.

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So that area of T two prolongation indicates

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that there is a edema in the bone, that it's a subacute

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or unhealed fracture and similar to nuclear medicine

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and uh, usually more readily available

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in the emergency department.

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So while bone scan MRI are the uh, most sensitive,

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they're probably, uh, equally sensitive in that regard.

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So again, using something that's more available to you, the

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fractures may be unilateral or bilateral.

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Again, it may have a connecting component in about

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20 to 40%.

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CT is sometimes done prior to procedures,

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but CT is also readily available

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in the emergency department.

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So it may be the second line imaging if radiography is not

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revealing to assess the extent of the fracture

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and particularly if it's involving the neuroforamin

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and potentially causing nerve symptoms.

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And sometimes these insufficient lesions can be confounded

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with metastatic disease, either both clinically

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or sometimes on imaging studies,

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if not carefully scrutinized.

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So here's an example of a 64-year-old female

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with no osteoporosis has right buttock and groin pain.

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Going through our checklist, if we look carefully,

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we can see that there is an asymmetry in the

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arcuate lines here.

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There's a little bit more sclerosis on the right

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and that's representative of that SA insufficiency fracture.

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Again, this is a frontal view of the pelvis, not a Ferguson

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or an inlet view, which might show those

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fracture lines on phos a little bit better.

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But on the same side where the side of the symptoms are,

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we also see areas of sclerosis

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and remodeling related to the superior pubic ramus adjacent

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to the paray sile region and the inferior pubic ramus.

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So these are all characteristic locations

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of pelvic insufficiency fractures.

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Here's some nice examples on both CT

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and MRI where you can see that there is a band like area

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of abnormality involving

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that zone one adjacent to the SI joint.

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It may present with uh,

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bone mar edema pattern on our fluid sensitive sequence

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depicting a fracture line on our anatomic sequence

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and then evidence of some remodeling and healing. With a

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Sclerosis on ct, it doesn't mean it's completely healed,

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it just means that it's starting the reparative process.

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Now here's a nice companion case not to be confounded

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for other more sinister pathologies.

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And so in this case we have a 67-year-old female remote

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history of gynecological malignancy now presents

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with two weeks of pubic pain as part of

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that malignancy was treated with radiotherapy.

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And so now if we get a magnification view of

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that parasail area

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and compare that to a radiograph

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that was done about a month before that.

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And so here we now see

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that on the right there is this loosen area that is medial

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to both the superior and inferior pubic ramus.

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So that's known as the parafoil region.

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There's also maybe some surrounding sclerosis so

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that it's hard to tell with some overlapping soft tissues.

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CT here confirms that there is a fracture line

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and in addition there's a little bit of heterotopic bone

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that's being formed around that.

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But on the soft tissue windows, there is no evidence

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of a soft tissue deposit

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or a soft tissue mass lesion

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that is causing that abnormality.

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As was one of the initial considerations

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when the case came in the potentially area

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of metastatic deposit.

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So here's our fracture line.

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And so we've talked about the pubic synthesis in traumatic

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lesions where you can get diastasis,

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but more commonly we're gonna see chronic conditions, uh,

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which may present with more acute symptoms

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or maybe with chronic symptoms.

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And so the pubic synthesis is a joint

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that undergoes arthritis.

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It's more of a fibrous joint.

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It can have stress lesions around it known as osteous pubis,

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so having a lot of sclerosis instability,

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which may occur either traumatic or postpartum.

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So after delivery you can have, uh,

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that area potentially diastat.

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These are associated with this other condition known

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as osteous, condensed an ILI I, which is basically a

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sclerotic reaction along the lower iliac bone

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adjacent to the SI joint.

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Again, reflecting just the motion that's occurring with

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SI joint and pubic synthesis.

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You can have stress fractures.

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Typically insufficiency fractures as I just showed you,

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they can be associated with sacral

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alar fractures in about 50% of cases.

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Now, another reason for having osteolysis

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or kind of bone resorption around the pubic synthesis

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is we get back to some of our avulsion abnormalities

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where you have the adductors attaching there.

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So when they pull off of the pubic synthesis region,

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they may create a bony resorption

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rather than a bony fragment.

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And then this manifests as osteolysis.

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And you may also have in athlete's, so-called synthesis,

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which is kind of the precursor to osteo pubis

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where you have a stress reaction across the pubic synthesis.