Fat Embolism Syndrome

Author: Tracy Jones

Topic updated on 03/17/13 9:34pm

Introduction
A syndrome caused by an inflammatory response to embolized fat globules characterized by hypoxia CNS depression pulmonary edema petechial rash Epidemiology incidence 3-4% with isolated long bone trauma 10-15% with polytrauma Pathophysiology fat and marrow elements are embolized into the bloodstream during acute long bone fractures intramedullary instrumentation intramedullary nailing hip & knee arthroplasty pathophysiology two theories regarding the causes of fat embolism include mechanical theory embolism is caused by droplets of bone marrow fat released into venous system metabolic theory stress from trauma causes changes in chylomicrons which result in formation of fat emboli Prognosis fatal in up to 15% of patients
Diagnosis Criteria
Major (1) hypoxemia (PaO2 < 60) CNS depression (changes in mental status) petechial rash pulmonary edema Minor (4) tachycardia pyrexia retinal emboli fat in urine or sputum thrombocytopenia decreased HCT Additional PCO2 > 55 pH < 7.3 RR > 35 dyspnea anxiety
Presentation
History symptoms usually present within 24 hours of inciting event Symptoms patient complains of feeling "short of breath" patient appears confused Physical exam tachycardia tachypnea petechiae axillary region conjunctivae oral mucosa
Studies
ABG hypoxemia (PaO2 < 60 mmHg)
Treatment
Nonoperative mechanical ventilation with high levels of PEEP (positive end expiratory pressure) indications acute fat emboli syndrome Prevention early fracture stabilization indications early fracture stabilization (within 24 hours) of long bone fracture is most important factor in prevention of FES techniques to reduce the risk of fat emboli overreaming of the femoral canal during a TKA use of reamers with decreased shaft width reduces the risk during femoral reaming for intramedullary fixation use of external fixation for definitive fixation of long bone fractures in medically unstable patients decreases the risk

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(OBQ09.214) An 85-year-old woman undergoes the treatment seen in Figure A for a displaced left femoral neck fracture. During wound closure, the patient becomes hypoxic and hypotensive. Despite aggressive resuscitation efforts, she passes away three hours later in the intensive care unit. The autopsy findings seen in Figure B from the patient's lungs are most likely the result of which of the following Topic

Review Topic

FIGURES: A

1. Reaming for the femoral component
2. Insertion of a femoral component after cement pressurization
3. Utilization of undersized broaches during canal preparation
4. Inadequate beta blockade
5. Use of spinal anesthesia

PREFERRED RESPONSE ▶

DISCUSSION: The clinical scenario is consistent with fat emboli syndrome. Figure A, shows a cemented bipolar hemiarthroplasty while Figure B shows marrow embolization into the lungs. Studies have shown that intramedullary pressure and fat embolization are greatest during pressurization of cement and implant insertion.

Intramedullary pressure is influenced by size, shape, sharpness and insertion rate of an implant. Pressurization during cementing of a femoral component generates a large degree of pressure over a much wider surface area than in the other methods described of femoral canal instrumentation or preparation, as the entire femoral canal is pressurized at one time. This results in the highest degree of marrow embolization to the lungs resulting in hypoxia.

Dobrjanski et al studied which variables affected intramedullary pressurization and found that lower implant insertion speed, lower hammering force, a rubber- compared with steel-tipped hammer and a larger synthetic bone-to-implant radial gap reduced intramedullary pressure generated in a femur module.

REFERENCES:

1. Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 307-31

2. Dobrjanski D, Saghir Z, Behdinan K, Zalzal P, de Beer J, Papini M.Intramedullary canal pressure distribution: An experimental parametric study. J Arthroplasty 2007;22:417-427 PMID:17400098 (Link to Abstract)

Question Authors:

Jan Szatkowski MD, Patrick McCulloch MD, Michael Hughes MD, Edward Perez M.D.,

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(OBQ06.62) A 79-year-old female with a history of congestive heart failure falls onto her right hip at home. A radiograph is provided in Figure A. She undergoes an uncemented unipolar hemiarthroplasty. During insertion of the stem into the femoral canal, the patient becomes hypotensive and hypoxic. Which of the following has most likely occurred? Topic

Review Topic

FIGURES: A

1. Femoral shaft fracture
2. Inadequate fluid resuscitation during surgery
3. Acute myocardial infarction
4. Pulmonary embolism caused by dislodging of deep venous thrombosis during hip exposure
5. Intramedullary fat and marrow embolization

PREFERRED RESPONSE ▶

DISCUSSION: During insertion of the femoral stem, the intramedullary pressures are increased. Fat and marrow elements can become embolized into the bloodstream at this point resulting in ventilation perfusion mismatch in the lungs.

Kim et al prospectively followed 156 total hip arthroplasties including bilateral and unilateral procedures as well as cemented and uncemented procedures. They found no difference in fat embolization amongst any of the groups. However, they did find that if patients had evidence of bone marrow cells in the right atrium on the first postoperative day, they developed diffuse encephalopathy with confusion and agitation that lasted for about twenty-four hours.

REFERENCES:

1. Kim YH, Oh SW, Kim JS: Prevalence of fat embolism following bilateral simultaneous and unilateral total hip arthroplasty performed with or without cement: A prospective, randomized clinical study. J Bone Joint Surg Am 2002;84:1372-1379. PMID:12177267 (Link to Abstract)

Question Authors:

John Badylak MD, Patrick McCulloch MD, Ben Taylor MD,

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(OBQ05.194) In a patient undergoing total knee arthroplasty, the femoral and tibial bone resections can be done using intra-or extra-medullary alignment systems. Extra-medullary guidance systems have what benefit over intra-medullary guidance systems? Topic

Review Topic

1. Decreased fracture risk
2. Decreased embolization risk
3. Decreased surface area available for cement interdigitation
4. Increased risk of blood loss and/or transfusion requirement
5. Increased rates of cerebral ischemia

PREFERRED RESPONSE ▶

DISCUSSION: Compared to intra-medullary guidance systems used for total knee arthroplasty, extra-medullary guidance systems show decreased embolization risk for the patient. The reason for this finding is that embolism syndrome in TKA typically is due to the placement of intra-medullary instrumentation for determination of the anatomical alignment.

Kim et al prospectively showed that fat embolization occurs due to intramedullary insertion of the alignment components. In their study, fat embolism was more common in bilateral than unilateral TKA as 65 patients (65%) with a bilateral TKA compared with and 46 patients (46%) with a unilateral TKA developed fat emboli.

In a second study, Kim et al evaluated the risk of fat embolism associated with computer navigated total knee arthroplasty and found that computer navigation does not appear to impart an elevated risk of fat embolism to the patient.

Ries et al studied the effect of different alignment rods on the risk of fat embolism. They found that intramedullary pressure during alignment rod insertion was significantly higher in patients with round compared with fluted alignment rods. As such, they recommend a fluted rather than a round intramedullary alignment rod to be used to minimize intramedullary pressure and pulmonary shunting during knee arthroplasties.

REFERENCES:

1. Kim YH: Incidence of fat embolism syndrome after cemented or cementless bilateral simultaneous and unilateral total knee arthroplasty. J Arthroplasty 2001;16:730-739 PMID:11547371 (Link to Abstract)

2. Kim YH, Kim JS, Hong KS, Kim YJ, Kim JH. Prevalence of fat embolism after total knee arthroplasty performed with or without computer navigation. J Bone Joint Surg Am. 2008 Jan;90(1):123-8. PMID:18171966 (Link to Abstract)

3. Ries MD, Rauscher LA, Hoskins S, Lott D, Richman JA, Lynch F Jr. Intramedullary pressure and pulmonary function during total knee arthroplasty. Intramedullary pressure and pulmonary function during total knee arthroplasty.Intramedullary pressure and pulmonary function during total knee arthroplasty.Clin Orthop Relat Res. 1998 Nov;(356):154-60. PMID:9917680 (Link to Abstract)

Question Authors:

Patrick O'Donnell MD/PhD, Patrick McCulloch MD, John Badylak MD,

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(OBQ04.147) A 20-year-old male sustains bilateral humeral shaft fractures and bilateral femoral shaft fractures from a motor vehicle collision. While awaiting surgery, the patient suddenly becomes tachycardic, hypoxemic and experiences mental status changes. Physical exam demonstrates multiple petechiae in bilateral axilla. CT angiography is negative for pulmonary embolus. What is the most likely diagnosis? Topic

Review Topic

1. hypovolemic shock
2. stroke
3. fat embolism syndrome
4. sundown syndrome
5. narcotic overdose

PREFERRED RESPONSE ▶

DISCUSSION: The clinical presentation is consistent for fat emboli syndrome. Fat embolism syndrome results when embolic marrow fat macroglobules damage small vessel perfusion leading to endothelial damage in pulmonary capillary beds leading to respiratory failure and ARDS like picture. Patients following long bone fractures are particularly susceptible to fat emboli syndrome. Fat emboli syndrome occurs in only 3-4% of patients with long bone fractures. The major clinical features of FES include hypoxia, pulmonary edema, central nervous system depression, and axillary or subconjunctive petechiae. Gurd et al. developed a criteria system to diagnose fat emboli syndrome based on the presence of major and minor criteria (see topic review for list of criteria). Key to treatment is maintaining perfusion to vital organs. Treatment is largely supportive.

REFERENCES:

1. Levy D. The fat embolism syndrome. A review. Clin Orthop Relat Res. 1990 Dec;(261):281-6. Review. PMID:2245559 (Link to Abstract)

2. Gurd AR, Wilson RI. The fat embolism syndrome. J Bone Joint Surg Br. 1974 Aug;56B(3):408-16. PMID:4547466 (Link to Abstract)

3. Tolo VT: Management of the multiply injured child, in Beaty JH, Kasser JR (eds): Rockwood and Wilkins’ Fractures in Children, ed. 5. Philadelphia, PA, Lippincott Williams & Wilkins 2001

Question Authors:

Paul D. Kim MD, Patrick McCulloch MD,

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Evidence & References Show References

Level of Evidence 2 (Prospective Cohort Study)

Kim YH, Oh SW, Kim JS: Prevalence of fat embolism following bilateral simultaneous and unilateral total hip arthroplasty performed with or without cement: A prospective, randomized clinical study. J Bone Joint Surg Am 2002;84:1372-1379. PMID:12177267 (Link to Abstract)

Level of Evidence 5 and Other Journal Articles (includes Case Reports, Expert Opinions, Personal Observations, and Biomechanic Studies)

Dobrjanski D, Saghir Z, Behdinan K, Zalzal P, de Beer J, Papini M.Intramedullary canal pressure distribution: An experimental parametric study. J Arthroplasty 2007;22:417-427 PMID:17400098 (Link to Abstract)

Textbooks

Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
Orthopaedic Knowledge Update 10, John M Flyn. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2011
Hoppenfeld SP. Surgical Exposures in Orthopaedics: The Anatomic Approach. Lipponcott, Williams, and Wilkins, Philadelphia, PA, Copyright 2009
Orthopaedic In-training Examination (OITE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Self-Assessment Examination (SAE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 307-31

Undefined

Kim YH: Incidence of fat embolism syndrome after cemented or cementless bilateral simultaneous and unilateral total knee arthroplasty. J Arthroplasty 2001;16:730-739 PMID:11547371 (Link to Abstract)
Kim YH, Kim JS, Hong KS, Kim YJ, Kim JH. Prevalence of fat embolism after total knee arthroplasty performed with or without computer navigation. J Bone Joint Surg Am. 2008 Jan;90(1):123-8. PMID:18171966 (Link to Abstract)
Ries MD, Rauscher LA, Hoskins S, Lott D, Richman JA, Lynch F Jr. Intramedullary pressure and pulmonary function during total knee arthroplasty. Intramedullary pressure and pulmonary function during total knee arthroplasty.Intramedullary pressure and pulmonary function during total knee arthroplasty.Clin Orthop Relat Res. 1998 Nov;(356):154-60. PMID:9917680 (Link to Abstract)
Levy D. The fat embolism syndrome. A review. Clin Orthop Relat Res. 1990 Dec;(261):281-6. Review. PMID:2245559 (Link to Abstract)
Gurd AR, Wilson RI. The fat embolism syndrome. J Bone Joint Surg Br. 1974 Aug;56B(3):408-16. PMID:4547466 (Link to Abstract)
Tolo VT: Management of the multiply injured child, in Beaty JH, Kasser JR (eds): Rockwood and Wilkins’ Fractures in Children, ed. 5. Philadelphia, PA, Lippincott Williams & Wilkins 2001

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Fat Embolism Syndrome

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