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Basics ⬇

Author: RebeccaBacharach, DO

Description

  • Traumatic fractures of the sacrum are most commonly described using the Denis system of fracture orientation:
    • Zone 1:
      • Fracture line usually vertically through the sacral ala
      • Entirely lateral to foramina
      • Typically, strength of sacroiliac (SI) ligaments spares SI joint from injury, but fractures that enter SI joint at greater risk for instability
      • Neural elements typically spared; <10% with neurologic involvement
    • Zone 2:
      • Fracture line through the neural foramina, but sparing the central spinal canal
      • 20–30% with neurologic injury
    • Zone 3:
      • Fracture line medial to neural foramina; typically includes transverse fractures
      • >50% with neurologic injury
  • Atraumatic injuries result from a mismatch between bone stress and bone strength:
    • Stress fractures in athletes
    • Insufficiency fractures in elderly:
      • Typically, bilateral in those with normal gait and unilateral in those with altered gait mechanics

Epidemiology

Sacral fractures need to be considered in several clinical scenarios:

  • Multitrauma patients with other pelvic or thoracolumbar injury:
    • Sacral fractures rarely occur as isolated injury (<5%).
  • Osteoporotic patients with low back or gluteal pain:
    • Atraumatic or trivial injury
  • Athletes with activity-related pain of low back/SI region:
    • 1.6% of sports-related low back pain (2)
    • Usually in running-based sports:
      • Often after increases in training intensity
    • May produce thigh pain as well

Etiology and Pathophysiology

Sacral fractures may occur by the following mechanisms:

  • Posttraumatic injuries:
    • Producing large forces and fracture across healthy bone:
      • Typically, motor vehicle accidents or falls from a height
  • Atraumatic injuries:
    • Normal stresses (or trivial injury) producing fractures across relatively weakened bone:
      • Insufficiency fractures in the elderly/ill
      • Fractures often bilateral
    • Increased stress or overuse, producing fracture across relatively normal bone:
      • Stress fractures in the younger, athletic population
      • Fractures often unilateral

Risk-Factors

  • Insufficiency fractures are most common in elderly osteoporotic females:
    • May occur in others at risk for poor bone density, including the following:
      • Chronic corticosteroid use
      • History of pelvic irradiation
  • Stress fractures occur most commonly in running athletes:
    • As with other stress fractures, risk probably increases with the following:
      • Training errors (inadequate recovery, increasing training, etc.)
      • Biomechanical factors (leg length discrepancy, poor core, and pelvic stabilization)
      • Increased impact forces (footwear, training surface)
      • Nutritional/hormonal impacts on bone density (relative energy deficiency in sport [RED-S], inadequate calcium [Ca]/vitamin D)

Commonly Associated Conditions

Acute sacral fractures may be seen in conjunction with:

  • Other bony injury:
    • Other pelvic ring disruptions
    • Other spinal fractures:
      • May be noncontiguous
    • Fracture-dislocations of lower facet joints or disruption of lumbosacral junction
  • Neurologic injury:
    • Should be described according to the Gibbons grading system:
      • Grade 1: no neurologic deficit
      • Grade 2: paresthesias/sensory changes only
      • Grade 3: motor deficit but gastrointestinal (GI)/genitourinary (GU) function normal
      • Grade 4: loss of GI/GU function
  • Injury to other pelvic contents:
    • Rectal perforation most common
  • Atraumatic sacral fractures
  • Osteoporosis
  • RED-S

Diagnosis ⬆ ⬇

Prehospital:

  • Traumatic sacral fractures typically occur in the multitrauma patient.
  • Initial assessment and treatment should proceed as per Advanced Trauma Life Support for patients with suspected spine injury:
    • Airway, breathing, and circulation (ABCs)/resuscitation
    • Spine precautions/backboard
    • Transport

History

  • Injury to sacrum is suggested by pain in lower back or pelvic pain and can radiate to the leg, groin, buttocks, or thigh (3).
  • Pain is often worse with weight-bearing activity; improved with rest
  • Important to inquire about possible nerve root involvement:
    • Incontinence of bowel or bladder, sexual dysfunction
    • Sciatica
    • Paresthesias, especially of saddle region
  • Patients without history of trauma should be asked about:
    • Change in activity or footwear, especially in running-based sports.
    • Risk factors for poor bone density:
      • Osteopenia/osteoporosis in patient or family members
      • Past or present disordered eating pattern
      • Oligo- or amenorrhea in females

Physical Exam

  • Trauma patient:
    • Inspect for ecchymosis/bruising over sacral prominence.
    • Palpate entire spinal column and bony pelvis in addition to the sacrum.
    • Neurologic testing of L5–S5 nerve root function should be completely assessed initially then periodically reevaluated:
      • Pinprick sensation, rectal sphincter contraction and tone as well as cremasteric, bulbocavernosus, perianal wink reflexes
      • L5 injuries most common with zone 2 injuries
      • Sacral roots have bilateral input, and unilateral injuries to S2–S5 are difficult to detect.
    • Digital rectal and vaginal evaluation to exclude open fractures
  • Atraumatic patient with possible insufficiency or stress fracture:
    • No pathognomonic findings
    • Typically with tenderness over sacrum, paraspinal, or over region of SI joint
    • FABER test (with hip in flexion, abduction, external rotation) often positive
    • Tenderness with lateral compression
    • Squish test—patient supine, palpate anterior superior iliac spine (ASIS) bilaterally
    • Distal neurovascular assessment typically normal
    • Gait may be antalgic and may have pain with a hop test.

Differential Diagnosis

  • Differential diagnosis for acute fractures:
    • Contusion
    • Other pelvic or lumbar fractures
    • Nerve root injuries
  • Differential diagnosis for atraumatic/stress fractures:
    • Lumbar disc disease
    • Mechanical low back pain
    • SI dysfunction
    • Spondylolysis

Diagnostic Tests & Interpretation

  • Trauma patients should have stool assessed for occult blood.
  • Consider secondary osteoporosis such as hyperthyroidism, hyperparathyroidism, and osteomalacia (thyroid-stimulating hormone [TSH], parathyroid hormone [PTH], Ca, phosphate [Phos], albumin, 25-hydroxyvitamin D, urinary Ca, complete blood count [CBC], liver function test [LFT], C-reactive protein [CRP], erythrocyte sedimentation rate [ESR]).
  • Traumatic injury:
    • Although radiographs typically only reveal about 30% of sacral fractures, they may be useful for initial assessment of suspected sacral injury:
      • Anteroposterior (AP) views of the pelvis are standard in multitrauma patients.
      • Visualization of suspected sacral injuries may be enhanced with the addition of pelvic inlet view: 35 to 40 degree caudal tilt of radiograph tube; pelvic outlet view: 45-degree cranial tilt of radiograph tube; lateral view of sacrum
      • Look for transverse L5 fractures, which can be seen in up to half of pelvic and sacral fractures.
    • Computed tomography (CT) scanning is now standard for definitive assessment of suspected acute sacral fracture:
      • Routine CT scans often not satisfactory
      • Close consultation with radiologist on gantry alignment recommended
      • Thin section (1.0 to 1.5 mm cuts) with coronal and sagittal reconstructions; relatively high radiation exposure: 10 to 20 mSV
    • Magnetic resonance imaging (MRI) may help delineate neural compression or injury:
      • Multiplanar nature may also better assess fracture alignment.
  • Atraumatic injury:
    • Initial lumbar spine series as well as AP views of the pelvis are often obtained:
      • Usually unremarkable
    • MRI of sacrum appropriate for diagnosis:
      • Gold standard for sacral stress fracture
      • Most bony stress injuries will have high signal on T2-weighted images, low signal on T1-weighted images.
      • Fracture line may or may not be present.
    • CT is an alternative to MRI:
      • Increased radiation
      • Can see sclerotic healing or fresh fracture line
    • Bone scan most sensitive but not specific for bony stress injury:
      • Stress fractures in athletes; typically with unilateral uptake sacral ala
      • Insufficiency fractures; often with multiple sites of injury; classic “H” sign seen in about 40% of patients; bilateral vertical fractures with horizontal component
      • Uptake can be obscured by residual in bladder; outlet views in addition to standard anterior and posterior projections

Treatment ⬆ ⬇

  • Acute fracture:
    • See below for surgical indications.
    • Stable injuries without neurologic involvement treated with initial bed rest and gradual ambulation and activity advancement as tolerated:
      • Fractures through S3 and distally often require protection with sitting until pain free.
  • Stress fracture: average ±6 wk for return to sport (but some may take up to 3 mo):
    • Protected weight-bearing if limp or pain with ambulation:
      • Advance weight-bearing as tolerated
    • Discontinue painful activity/relative rest.
    • Maintain cardiovascular conditioning with pain-free activity:
      • May need to begin with non–weight-bearing activity (typically swimming or cycling)
    • Begin progressive rehabilitation typically after 3- to 5-day pain-free interval:
      • Core/pelvic stabilization; address underlying biomechanical deficiencies.
      • Cardiovascular cross-training progression through following sequence when activity is pain free: non–weight-bearing (i.e., pool running, bicycling), weight-bearing/nonimpact (i.e., elliptical-type trainer), impact (i.e., running), sports-specific functional progression
  • Insufficiency fractures in elderly may have prolonged symptoms (up to 9 mo):
    • Initial treatment is usually nonoperative, even for patients with neurologic deficit:
      • Many authors recommend initial period bed rest followed by progressive ambulation.
      • Neurologic symptoms appear to improve as pain resolves.
    • Consider surgery if severe pain after 3-mo trial conservative treatment.

Medication

  • Analgesics should be titrated for symptom relief:
    • Should not be used specifically to allow for progression of activity or sport participation
    • Scheduled doses for first several days of diagnosis may allow for pain-free rest:
      • Over-the-counter analgesics often sufficient for stress fractures: acetaminophen up to 1,000 mg q4h PRN; pediatric dosage 10 to 15 mg/kg up to q4h nonsteroidal drugs often beneficial. Theoretically may impair bony healing, but no consensus on effect on clinical outcomes. Naproxen 500 mg q12h; pediatric dosage 10 to 20 mg/kg/day divided BID
    • Patients with severe pain may need stronger medications for first several days:
      • Hydrocodone/acetaminophen 5/500 1 to 2 PO q4–6h PRN; pediatric suspension 7.5/500/15 mL; patient weight 32 to 45 kg: 10 mL q4–6h PRN
      • Tramadol 50 mg 1 to 2 tabs q4–6h PRN; maximum dose 400 mg/day; caution in elderly and with renal or hepatic impairment
  • Supplemental vitamin D and Ca for stress or insufficiency fractures:
    • 1 g Ca daily
    • 800 to 1,000 IU vitamin D daily

Surgery/Other Procedures

  • Surgical consideration for traumatic sacral fractures:
    • Unstable injuries
    • Severe disruption of sagittal or coronal alignment:
      • In AP plane displacement, >1 cm generally recognized as unstable
    • Neurologic impairment
    • Injuries with persistent pain after about 6 mo
  • Insufficiency fractures considered for surgery if with persistent, severe pain after 3 mo conservative treatment

Admission, Inpatient, and Nursing Considerations

  • Acute traumatic sacral fractures often require hospitalization for additional injury:
    • Isolated and stable zone 1 or 2 fractures with no neurologic deficit and adequate pain control may be considered for outpatient treatment.
  • Stress fractures and insufficiency fractures are generally managed in outpatient setting.

Ongoing Care ⬆ ⬇

Sacral stress or insufficiency fractures may be a bellwether for underlying metabolic bone disease:

  • Bone density testing or other laboratory evaluation should be considered.

Diet

Patients with insufficiency or stress fractures should be counseled on appropriate intake of Ca and vitamin D.

Patient Education

Education should focus on biomechanical issues and training errors predisposing to injury:

  • Importance of maintaining adequate strength and flexibility of core and pelvic musculature
  • Advance training volume by ~10% per week to minimize risk of additional overuse injury.
  • Especially in the running athlete, the importance of appropriate footwear selection:
    • Effective life span of most running shoes is 300 to 400 miles.

Prognosis

  • Healthy athletes with sacral stress injury:
    • Usually able to return to normal activity 4 to 6 wk
    • Usually able to return to sport 6 to 10 wk
  • Elderly patients with insufficiency fractures may have pain for many months.
  • Fractures requiring surgery often with instrumentation:
    • Up to 1/3 may have hardware failure.

Complications

  • Deformity or bony callus formation after acute injury may lead to nerve root entrapment.
  • Prolonged pain common in elderly with insufficiency fractures

Additional Reading ⬆ ⬇

  • Kuklo TR, Potter BK, Ludwig SC, et al. Radiographic measurement techniques for sacral fractures consensus statement of the Spine Trauma Study Group. Spine (Phila Pa 1976). 2006;31(9):1047–1055.
  • Levine AM. Fractures of the sacrum. In: BrownerBD, LevineAM, JupiterJB, et al, eds. Skeletal Trauma. 4th ed. Philadelphia, PA: Saunders; 2008.
  • Micheli LJ, Curtis C. Stress fractures in the spine and sacrum. Clin Sports Med. 2006;25(1):75–88.
  • Shah MK, Stewart GW. Sacral stress fractures: an unusual cause of low back pain in an athlete. Spine (Phila Pa 1976). 2002;27(4):E104–E108.
  • White JH, Hague C, Nicolaou S, et al. Imaging of sacral fractures. Clin Radiol. 2003;58(12):914–921.

References ⬆ ⬇

  1. Beckmann NM, Chinapuvvula NR. Sacral fractures: classification and management. Emerg Radiol. 2017;24(6):605–617.
  2. Kaneko H, Murakami M, Nishizawa K. Prevalence and clinical features of sports-related lumbosacral stress injuries in the young. Arch Orthop Trauma Surg. 2017;137(5):685–691.
  3. Longhino V, Bonora C, Sansone V. The management of sacral stress fractures: current concepts. Clin Cases Miner Bone Metab. 2011;8(3):19–23.

Clinical Pearls ⬆

  • Consider sacral injury in any acute injury resulting in other pelvic or spinal injury.
  • Consider sacral injury in chronic cases of low back, thigh, or buttock pain.
  • Sacral fractures are typically occult on plain radiographs and often require advanced imaging for definitive diagnosis.