Updated: 9/24/2019

Sacral Insufficiency Fracture

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Introduction
  • Overview
    • sacral insufficiency fractures are a fragility fracture that occurs more commonly in elderly women
      • treatment is usually observation, with operative treatment reserved for those who fail nonoperative treatment
  • Epidemiology
    • incidence
      • 1% of women > 55 years old
        • increases with age
        • estimated to increase by 23% each year
    • demographics
      • females more commonly affected 2:1
      • average age is 69 years old
    • risk factors
      • osteoporosis
      • vitamin D deficiency
      • rheumatoid arthritis
      • prolonged immobilization
      • long-term steroid use
      • pelvic radiation
  • Pathophysiology
    • mechanism of injury
      • low energy trauma (i.e. ground level fall)
  • Associated conditions
    • other fragility fractures (i.e. distal radius, vertebral, hip)
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 
Zone 1
 • fracture lateral to foramina
Zone 2
 • fracture through foramina
Zone 3
 • fracture medial to foramina into the spinal canal
 
 
Presentation
  • History 
    • low-energy trauma (i.e. ground level fall)
  • Symptoms
    • pain
      • groin, low back, buttock
      • worse with weightbearing
  • Physical exam
    • limited hip motion
    • neurologic deficits are rare
Imaging
  • Radiographs
    • recommended views
      • AP
      • lateral
      • inlet view
        • best assessment of sacral spinal canal and superior view of S1
      • outlet view
        • provides true AP of sacrum
  • CT
    • indications
      • negative radiographs but high suspicion for fracture
      • confirmed fracture on radiographs
  • MRI
    • indications
      • negative radiographs and CT but high suspicion for occult fracture
  • Bone scan
    • indications
      • no longer used
    • findings
      • Honda or H sign
        • seen with H-type fractures
Studies
  • Serum labs
    • evaluate for causes of osteoporosis
Treatment
  • Nonoperative
    • observation, mobilization, analgesia, osteoporosis screening & treatment
      • indications
        • first line of treatment
  • Operative
    • sacroplasty
      • indications
        • minimally displaced zone 1 injuries after failed nonoperative treatment
    • ORIF
      • indications
        • displaced zone 1 injuries after failed nonoperative treatment
        • zone 2 or 3 injuries after failed nonoperative treatment
Techniques
  • Sacroplasty
    • technique
      • injection of polymethylmethacrylate cement
    • complications specific to this treatment
      • cement leakage
        • avoid sacroplasty in displaced fractures due to risk of symptomatic cement leakage
  • ORIF
    • technique
      • unilateral iliosacral screws
        • place 2 parallel 7-8mm cannulated screws perpendicular to the fracture plane
          • 2 screws have more stability than 1 screw
          • screws should cross midline
          • stability is dependent on the strength of the sacral cancellous bone
        • use washers to prevent penetration of the screw head through the lateral cortex of the posterior part of the ilium
      • trans-sacral screw
        • place 6mm screw through the sacral corridor of S1
      • posterior bridging plate
        • place plate against sacrum and posterior part of ilium
        • acts as tension band
    • complications specific to this treatment
      • implant loosening
      • hardware failure
Complications
  • Non-union
  • Persistent pain
 

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