Sacral insufficiency fracture

sacral insufficiency fractures


Sacral insufficiency fractures (SIFs) are often misdiagnosed or under diagnosed and may be the root of back or groin pain. They were orginally described in 1982 and can be a disabloing cause of low back pain and immobilization [1].  Many times the condition can elude diagnostic studies if the sacrum or pelvis is not properly imaged or if there is lack of suspicion by the provider.  The incidence of SIF is estimated to be between 1.0-1.8% but rates as high as 5 % have been reported [2-3].

Case Vignette

A 73 year old female with a history of osteoporosis presents with very mild left groin discomfort and mild right buttocks pain for about one month that seemed to worsen quickly over a few days. She denies any particular trauma to the region. The pain does seem to be fairly constant throughout the day and worsens with activity. She denies increasing her walking activity or workload recently. There has been very mild relief with ibuprofen and the pain does not seem to wake her up from sleep. On physical examination, there is tenderness over her right sacroiliac joint and along the sacral ala region superiorly on the right. She had an x-ray of her lumbar spine, pelvis and left hip that showed mild degenerative change over the left hip joint and scattered degenerative changes over the lower lumbar spine, but no definitive fracture. What is the most likely diagnosis?

A) Femoral neck fracture
B) Baastrup’s disease
C) Sacral insufficiency fracture
D) Chronic lumbar compression fracture

The sacroiliac joint relieves torsional stress created during normal gait.  When pathology is present in the SI joint, mechanical load is transferred more to the sacrum.  The sacrum can become weak with age and other conditions such as osteoporosis and can become prone to fracture.  This is due to less resistance to the torsional stress and decreased stabilization of the pelvis with physiological stress [4].  Risk factors tend to support this pathophysiology.  These include osteoporosis, steroid-induced osteopenia, postmenopause, pelvic radiation and rheumatoid arthritis.  SIFs are mostly found in patients older than 55 years and predominate in those with a mean age of 70–75 years old.


The clinical presentation and physical examination can be variable and diagnosis can be challenging.  This condition is clinically characterized by pain in the inguinal and gluteal regions and commonly occurs in patients with no trauma or minor trauma resulting from a fall.  It does fall under the common stress pattern with symptoms being worse with activity and better with rest.  This does make more concerning diagnosis such as malignancy less likely, but SIFs can be associated with malignancy or metastasis.  Neurological signs and symptoms are rare.

physical examination

Physical examination can also be fairly nonspecific, but is necessary to rule out other concomitant conditions.  There may be tenderness over one or both sacroiliac joints and when palpating the sacrum.  There may be pain with internal rotation of the affected side and a FABER test may also be positive for sacroiliad joint pain, though these signs are neither specific or sensitive.  A thorough lumbar and lower extremity neurologic physical examination should also be performed to aid the diagnosis.  Some reports show decreased ankle reflexes and restricted back extension.


A plain film or radiograph of the pelvic and sacrum should be performed, though it can also be unrevealing.  A fracture is sometimes seen over the sacral ala and there is often  a delay of 40 to 55 days from onset of pain to sacral radiographs [4].

X-ray sacral insufficiency fracture

Image 1.  Plain radiograph showing vertical sacral insufficiency fracture.  Adopted from [21]

As a result of nonspecific symptoms on presentation and variable findings on X-ray, SIF may be missed or misdiagnosed. Physical exam findings can be entirely normal; however, some patients may have diminished ankle reflexes or restricted back extension. In such patients, X-ray findings can similarly be entirely unremarkable; however, fracture is most often seen in the sacral ala. Often, there is a delay of 40–55 days in obtaining sacral radiographs and 20-38 percent of SIFs are visible on plain radiographs with 12.5 % with visible fracture lines. MRI is the gold standard for imaging studies.  MRI may show disc degeneration, lumbar stenosis, or hyper-intensity with foraminal stenosis in the sacral region. Late in the disease course, MRI may reveal associated edema in the sacral region.  One study showed diagnosis by MRI in 74% of cases, 12% with CT scan and 12% with plain x-ray [5]. It is also worth noting that the majority of SIFs tend to occur with a lumbar MRI ordered and not a pelvic MRI.  Bone scintigraphy can be nonspecific and look similar to lumbar degenerative changes.

The Denis classification describes different types of traumatic sacral fractures as well as the various SIF. There are three “zones” in the Denis classification.  The first zone describes a sacral fracture that is most lateral and involves the sacral ala. Zone 1 is the most common location of fracture for patients with SIF.  Zone 2 is a sacral fracture involving the neural foramina, and zone 3 is medial involving the sacral bodies and transverse central canal. These fractures tend to fracture vertically; however, there can be a horizontal component as well that can be seen on MRI as the “Honda” or “H” sign [5].

Denis classification sacrum

Image 2: Denis classification for sacrum fractures.  Adopted from [20].


Historically, conservative management has been the mainstay of treatment for SIFs.  The main focus is on early rehabilitation/physical therapy, modified bed rest and pain control.  Initial guidelines recommended relative immobility for approximately three to six months following the fracture.  More recent studies show early mobilization may improve outcomes and lead to fewer complications.  Complications from prolonged immobility include deep vein thrombosis (DVT), decreased muscle strength and cardiac dysfunction [6].  Further bone demineralization can also occur with limited weight bearing.  Traditional weight-bearing activity as tolerated can stimulate osteoblastic bone formation.  The use of assisted devices may be necessary such as protected weight bearing with crutches or a walker.  Aqua therapy is another modality used to achieve weight bearing activity.  Many will show improvement in 1-2 weeks and there has also been evidence of less pain and increased mobility even at 6 months [7].  

There are also pharmacologic agents used for SIFs.  Pain control is important during recovery, although this can be challenging.  Opioids, Non-steroid anti-inflammatory drugs (NSAIDs) and acetaminophen are most frequently used.  Many people will use NSAIDs, although debate remains on whether NSAIDs reduce bone mineral density or delay fracture healing.

MRI sacral insufficiency fracture

Image 3: MRI with T2 images showing sacral insufficiency fracture.  Adopted from [21]

Underlying conditions should also be treated if present.  Many patients may have a history of osteoporosis or osteopenia.  Vitamin D (at least 800 IU) and Calcium (1200-1500 mg) should be used daily.  Bisphosphonates are most commonly used to treat osteoporosis and it is recommended to reassess every 5 years if one chooses to treat with this.  Teriparatide, a recombinant form of parathyroid hormone (PTH), has recently emerged as a new treatment for SIF.  Studies have demonstrated that teriparatide has positive effects on bone healing such as increasing bone mineral density, increasing osseous tissue volume, and reducing fracture healing time [8-11].   The mean time to fracture healing was 7.4 weeks compared to 13.6 weeks in the control group in one of the studies [12].  The efficacy of long-term management of teriparatide is not yet known. However, after 2 years of use, there appears to be a reduction in bone mineral density and increase in porosity [13].

Newer interventional treatment options are also available.  Similar to a kyphoplasty, a sacroplasty is a minimally invasive procedure in which polymethyl methacrylate (PMMA) cement is injected into bone to improve its structural integrity and alleviate symptoms.  The literature has been positive at this point but is very limited.  Thus far in patients with SIF, sacroplasty has been demonstrated to improve pain scores and increase patients’ participation in activities of daily living (ADL) [14-15].  Kortman et al. assessed the effectiveness and safety of sacroplasty in patients with osteoporotic SIF or pathological sacral lesions. They studied 243 patients with 204 with painful SIF and 39 with symptomatic sacral lesions. The average pretreatment pain score of 9.2 was significantly improved after sacroplasty to 1.9 [16].  Balloon sacroplasty is a similar procedure that has also been shown to be effective in limited studies [17].  

One recent ten year longitudinal study followed a group of 244 SIF patients, 34 of whom received nonsurgical management (NSM), and 210 of whom were treated with sacroplasty.  Although both groups had a comparable average initial VAS score after 2 weeks, the sacroplasty group experienced an average pain score reduction of 66%, while the NSM group only experienced a 27.2% reduction. Each group then had significant drops in pain scores over the next ten years, but the sacroplasty group used less opioids [18].  

Transiliac-transsacral screw stabilization is a surgical technique that may offer rapid pain relief for patients refractory to conservative management. Follow-up studies indicate patients remain mobile and pain-free for at least 12 months after the surgery with high satisfaction [19].  There can be unique challenges with surgical management due to osteoporotic bone. 


In conclusion, sacral insufficiency fractures (SIFs) most commonly occur in the elderly population and sometimes with other pathologic conditions.  They tend to occur due to compromised biomechanics and weakened bone density.  It is often improperly diagnosed or misdiagnosed due to nonspecific symptoms and limited value of plain radiographs.  Conservative management has been evolving and early mobilization, physical rehabilitation and pain control are the focus of treatment.  Sacroplasty and balloon sacroplasty are more recent procedures that have shown promise with fairly rapid and long term results.  In comparison with nonsurgical management, sacroplasty has been shown to have greater pain reduction and improved mobility.  Transiliac-transsacral screw stabilization is a surgical treatment reserved for failure of conservative measurements and has also shown promising results. 

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Case Conclusion

Answer C. As a result of nonspecific symptoms on presentation and variable findings on X-ray, SIF may be missed or misdiagnosed. Physical exam may be normal but there can be some tenderness over the sacroiliac joint, sacrum, diminished ankle reflexes and restricted back extension. There is frequently a delay of 40–55 days in obtaining sacral radiographs and only 20-38 percent of SIFs are visible on plain radiographs with 12.5 % with visible fracture lines. MRI is the gold standard for imaging studies and many times needed for definitive diagnosis. The patient in the vignette had no trauma to the area and no acute fractures were seen on plain radiographs, making femoral neck fracture or chronic lumbar compression fracture less likely. Baastrup’s disease usually presents with pain with extension and relief with flexion.

Kinoshita H, Miyakoshi N, Kobayashi T, Abe T, Kikuchi K, Shimada Y. Comparison of patients with diagnosed and suspected sacral insufficiency fractures. J Orthop Sci. 2019;24:702–7.


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