Research Review by Dr. Shawn Thistle©

Date:

Apr. 2007

Study Title:

Sacral insufficiency fractures: Current concepts of management

Authors:

Tsiridis E, Upadhyay N & Giannoudis PV

Publication Information:

Osteoporosis International 2006; 17: 1716-1725.

Summary:

Stress fractures can mimic many conditions commonly treated in musculoskeletal practice. In the pelvic ring, osteoporotic fractures are not uncommon, but are frequently unrecognized. Insufficiency fractures represent a unique category of stress factures that occur in bones with reduced mineral content and elastic resistance.

Sacral insufficiency fractures (SIF) are a well-defined subgroup of insufficiency fractures that can be difficult to detect. As the population ages, this clinical entity will become more common and socially and economically significant. SIFs represent an important differential diagnosis for patients presenting with back and pelvic pain. The clinical aspects of SIFs will be reviewed below.

Epidemiology of SIFs:
  • the exact prevalence of SIFs is unknown, but is increasing as the population ages
  • the best estimate based on the available literature indicates that ~2% of women over the age of 55 presenting with low back pain may have a SIF
  • 90% of SIFs occur in elderly women
  • SIF victims require an average of 20 days of hospitalization, with total costs comparable to femoral neck stress fractures
Classification of SIFs: Currently, there is no classification system for SIFs. However, Denis et al. (Clin Orthop Rel Res 1988) previously developed a classification system for traumatic sacral fractures that can easily be applied to SIFs:
  1. 1) Zone 1 fracture: involves the sacral ala (lateral to the foramen), and is rarely associated with neurological deficits, although damage to the lumbosacral nerve roots may occur
  2. Zone 2 fracture: involves one or several of the sacral foramina but does not enter the central sacral canal - often cause unilateral lumbosacral radiculopathies
  3. Zone 3 fracture: occur through the body of the sacrum and involve the vertical or transverse central canal - significant neurological deficit is common including saddle anesthesia and loss of sphincter control (cauda equine syndrome)
The majority of SIFs occur in zone 1, with the fractures generally being vertical, parallel to the SI joint, and in line with the lateral margins of the lumbar vertebrae. This area corresponds to the vertical loading axis in the sacrum. SIFs are frequently bilateral, and related to other stress fractures in the pelvic ring.

Risk Factors & Pathophysiology
  • several conditions that can compromise bone density can contribute to SIFs
  • postmenopausal osteoporosis is the most common cause of SIFs
  • other predisposing factors include: long-term corticosteroid therapy, radiation therapy, hyperparathyroidism, osteomalacia, renal osteodystrophy, Paget's disease, Rheumatoid Arthritis, and any other conditions that can adversely affect bone mineral density
  • poor dietary intake and reduced gut absorption of Vitamin D is also a common risk factor
  • pregnancy and lactation-induced transient osteoporosis has also been reported to be associated with SIFs in case reports - osteopenia coupled with relaxin-induced ligament laxity is thought to be the mechanism involved
Clinical Presentation & Physical Examination
  • SIF presentation is variable, and often inconspicuous
  • SIFs often present as mechanical low back pain that is insidious, intractable, and associated with a loss of mobility and function (again, primarily in seniors)
  • symptoms are generally worsened when weight-bearing, and improve with rest, particularly in a supine position
  • the predominant symptom is lumbosacral pain, which may be severe, and radiate to the groin, low back, buttocks and thighs
  • SIFs associated with pubic rami fractures may also present with tenderness over the parasymphysial area
  • the patient may not report a traumatic onset, or report severe onset of pain with a relatively low impact trauma
  • physical examination may reveal sacral tenderness with any compression testing (ex. side compression, P-A joint challenge), while SI joint tests may also be positive (ex. FABERE, Gaenslen's, thigh thrust)
  • gait can become slow and antalgic (of course this is not specific to SIF)
  • Trendelenburg test and nerve tension tests (ex. straight leg raise) are usually negative
  • neurological examination is generally normal (except in cases of nerve root compromise as mentioned above)
  • Differential Diagnoses - lumbar compression fracture, malignancy or osteomyelitis, Si joint conditions, spinal stenosis, abdominal pathology, space-occupying lesions, degenerative spondylolisthesis
Imaging & Laboratory Investigation:
  • lab tests relevant to SIFs include: Bone Alkaline Phosphatase (ALP), and any test involved in identifying causes of reduced bone mineral density - thyroid-stimulating hormone, parathyroid hormone, calcium, phosphorus, albumin, Vitamin D, C-reactive protein, erythrocyte sedimentation rate (ESR), urine proteins
  • Plain film x-rays of the lumbar spine, sacrum and pelvis are the first line of diagnostic imaging – but may be inadequate to demonstrate SIF, particularly in the acute phase before adequate bone calcification can be visualized. Look for sclerotic bands, cortical disruption, or fresh fracture lines.
  • MRI is by far the most sensitive imaging modality for SIFs - can visualize the actual fracture (coronal series may be very helpful for this), and any associated bone marrow edema resulting from the inflammatory and reparatory processes
  • bone scintigraphy (bone scan) - classic "H"pattern may be visualized, however this modality may not identify bilateral fractures due to the higher uptake that generally occurs in sacroiliac joint regions
  • CT scan - not as useful as MRI but may be more readily available in some regions
  • Bone Mineral Density (BMD) - should be included if the patient has not had a recent test done
Treatment & Management
  • SIFs are initially treated conservatively with bed rest and analgesic medications or modalities
  • longer-term management includes gradual mobilization and activation (which may be facilitated by walking aids), in addition to anti-resorptive medication to reduce the risk of subsequent fracture
  • physical therapy interventions (after the brief period of bed rest) can include: progressive weight-bearing exercises, electro-modalities, hydrotherapy, soft tissue therapy for adjacent musculature, proprioceptive training, supportive devices, and eventual progressive strengthening exercises (note that sufficient literature to support or guide the application of any of these interventions does not yet exist)
  • treating clinicians should be aware of potential immobilization (bed rest) complications including: deep vein thrombosis, pulmonary embolism, muscle atrophy, respiratory complications, urinary tract infections, gastrointestinal complications, and mental health symptoms
  • recent literature suggests that early weight-bearing rehabilitation can provide a stimulating effect on muscle tension and osteoblastic bone formation (although the ideal timing of this intervention is not yet known)
  • spinal manipulation of the pelvis is contraindicated in patients with known SIF, and extreme caution should be employed in applying manipulation to any other body region in these patients until bone status is clarified

Conclusions & Practical Application:

In a clinical setting, SIF should be suspected in elderly patients presenting with low back and pelvic pain with no history of trauma (or with low impact trauma). Post-menopausal osteoporosis is the most common risk factor, but reversible causes of secondary osteoporosis should also be ruled out.

The prudent manual therapist will co-manage these patients with a primary care physician, but can provide symptomatic relief in a variety of ways, and play a leading role in the rehabilitation and strengthening process once appropriate healing has occurred.