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Updated: Nov 26 2023

Sacral Fractures

Images 2.jpg - AP Pelvis - L sacral fx_moved.jpg 1.jpg
  • Summary
    • Sacral fractures are common pelvic ring injuries that are under-diagnosed and often associated with neurologic compromise.
    • Diagnosis can made with pelvis radiographs but frequently require pelvic CT scan for full characterization.
    • Treatment may be nonoperative or operative depending on fracture displacement, associated pelvic ring instability and patient activity demands. 
  • Epidemiology
    • Incidence
      • common in pelvic ring injuries (30-45%)
    • Bimodal distribution
      • young adults
        • as a result of high energy trauma
      • elderly
        • as a result of low energy falls
    • Associate injuries
      • 25% are associated with neurologic injury
        • frequently missed
          • 75% in patients who are neurologically intact
          • 50% in patients who have a neurologic deficit
  • Anatomy
    • Osteology
      • formed by fusion of 5 sacral vertebrae
      • articulates with
        • 5th lumbar vertebra proximally
        • coccyx distally
        • ilium laterally at sacroiliac joints
      • contains 4 foramina which transmit sacral nerves
    • Nerves
      • L5 nerve root runs on top of sacral ala
      • S1-S4 nerve roots are transmitted through the sacral foramina
        • S1 and S2 nerve roots carry higher rate of injury
      • lower sacral nerve roots (S2-S5)
        • function
          • anal sphincter tone / voluntary contracture
          • bulbocavernosus reflex
          • perianal sensation
        • unilateral preservation of nerves is adequate for bowel and bladder control
    • Biomechanics
      • transmission of load distributed by first sacral segment through iliac wings to the acetabulum
  • Classification
    • Denis classification
      • Denis classification
      • Zone 1
      • Fracture lateral to foramina
      • Most common (50%)
      • Nerve injury rare (5%). 
             -usually occurs to L5 nerve root
      • Zone 2
      • Fracture through foramina
      • May be stable vs. unstable
      • Zone 2 fracture with shear component highly unstable
      • Unstable fractures have higher risk of nonunion and poor functional outcome
      • Fracture medial to foramina into the spinal canal
        Highest rate of neurologic deficit (60%)
      •     -bowel, bladder, and sexual dysfunction
    • Transverse sacral fractures
      • higher incidence of nerve dysfunction
    • U-type sacral fractures
      • results from axial loading
      • represent spino-pelvic dissociation
      • high incidence of neurologic complications
  • Presentation
    • History
      • motor vehicle accident or fall from height most common
      • repetitive stress
        • insufficiency fracture in osteoporotic adults
    • Symptoms
      • peripelvic pain
    • Physical exam
      • inspection
        • soft tissue trauma around pelvis should raise concerns for pelvic or sacral fracture
      • palpation
        • test pelvic ring stability by internally and externally rotating iliac wings
        • palpate for subcutaneous fluid mass indicative of lumbosacral fascial degloving (Morel-Lavallee lesion)
        • perform vaginal exam in women to rule-out open injury
      • neurologic exam
        • rectal exam
        • light touch and pinprick sensation along S2-S5 dermatomes
        • perianal wink
        • bulbocavernosus and cremasteric reflexes
      • vascular exam
        • distal pulses
          • if different consider ankle-brachial index or angiogram
  • Imaging
    • Radiographs
      • only show 30% of sacral fractures
      • recommended views
        • AP
        • lateral
          • effective screening tool for sacral fractures
          • often of poor quality
        • inlet view
          • best assessment of sacral spinal canal and superior view of S1
        • outlet view
          • provides true AP of sacrum
      • findings
        • L4 or L5 transverse process fractures
        • asymmetric foramina
        • anterior pelvic ring disruptions
        • stepladder sign
          • seen on AP view
          • results from displacement with overriding of transverse fracture fragments
          • indicates disruption of anterior sacral foramina and lumbrosacral facets
    • CT
      • diagnostic study of choice
      • recommend coronal and sagittal reconstruction views
    • MRI
      • recommended when neural compromise is suspected
  • Treatment
    • Nonoperative
      • progressive weight-bearing +/- orthosis
        • indications
          • <1 cm displacement and no neurologic deficit
          • insufficiency fractures
    • Operative
      • surgical fixation
        • indications
          • displaced fractures >1 cm
          • soft tissue compromise
          • persistent pain after non-operative management
          • displacement of fracture after non-operative management
      • surgical fixation with decompression
        • indications
          • any evidence of neurologic injury
  • Techniques
    • Percutaneous screw fixation
      • screws may be placed as sacroiliac, trans-sacral or trans-iliac trans-sacral
      • useful for sagittal plane fractures
      • technique
        • screws placed percutaneously under fluoroscopy
        • beware of L5 nerve root
        • avoid overcompression of fracture
          • may cause iatrogenic nerve dysfunction
        • screw placement posterior to the ICD ensures safe screw placement
          • non-dysmorphic sacrum
      • cons
        • may result in loss of fixation or malreduction
        • does not allow for removal of loose bone fragments
        • do not use in osteoporotic bone
    • Posterior tension band plating
      • approach
        • posterior two-incision approach
      • technique
        • may use in addition to iliosacral screws
      • pros
        • allows for direct visualization of fracture
      • cons
        • wound healing complications
    • Iliosacral and lumbopelvic fixation
      • approach
        • posterior approach to lower lumbar spine and sacrum
      • technique
        • pedicle screw fixation in lumbar spine
        • iliac screws parallel to the inclination angle of outer table of ilium
        • longitudinal and transverse rods
      • pros
        • shown to have greatest stiffness when used for an unstable sacral fracture
      • cons
        • invasive
    • Decompression of neural elements
      • technique
        • indirect
          • reduction through axial traction
        • direct
          • posterior approach followed by laminectomy or foraminotomy
  • Complications
    • Venous thromboembolism
      • often as a result of immobility
    • Iatrogenic nerve injury
      • may result from
        • overcompression of fracture
        • improper hardware placement
    • Malreduction
      • more common with vertically displaced fractures
  • Prognosis
    • Presence of a neurologic deficit is the most important factor in predicting outcome
    • Displacement confers an increased risk of neurologic dysfunction
    • Mistreated fractures may result in
      • lower extremity deficits
      • urinary dysfunction
      • rectal dysfunction
      • sexual dysfunction
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