Musculoskeletal · Orthopedic Trauma
The facts most likely to be tested
High-energy femoral shaft fractures are frequently associated with hypovolemic shock due to significant occult blood loss into the thigh compartment.
The classic physical exam finding for a femoral shaft fracture is a shortened, externally rotated leg with significant thigh deformity.
Fat embolism syndrome is a life-threatening complication characterized by the triad of hypoxemia, neurologic abnormalities, and a petechial rash.
Intramedullary nailing is the gold standard surgical treatment for diaphyseal femoral fractures in adults to allow for early mobilization.
Traction splinting (e.g., Hare or Sager splint) is the immediate prehospital intervention to reduce pain and minimize further soft tissue injury.
Femoral neck fractures carry a high risk of avascular necrosis (AVN) of the femoral head due to disruption of the medial circumflex femoral artery.
Compartment syndrome is a rare but critical complication of femur fractures that presents with pain out of proportion to injury, pain with passive stretch, and tense compartments.
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A 24-year-old male is brought to the emergency department following a high-speed motorcycle collision. He is tachycardic and hypotensive. Physical examination reveals a shortened, externally rotated right lower extremity with a grossly deformed, swollen mid-thigh. The patient is alert but confused. A petechial rash is noted on his chest and axilla 12 hours after admission.
What is the most likely diagnosis for the patient's new-onset respiratory distress and cutaneous findings?
Fat embolism syndrome
The patient's presentation of hypoxemia, altered mental status, and petechial rash following a long-bone fracture is the classic triad for fat embolism syndrome, which is a high-yield complication of femur fractures.
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High yield triage
Etiology / Epidemiology
High-energy trauma in young adults; low-energy falls in osteoporotic elderly. Femoral neck fractures carry high risk of avascular necrosis.
Clinical Manifestations
Shortened, externally rotated leg is the classic presentation. Pain with hip rotation is pathognomonic for occult fractures.
Diagnosis
AP/Lateral Radiographs are the gold standard. MRI is the diagnostic choice for suspected occult fractures.
Treatment
Intramedullary nailing is the standard for shaft fractures. ORIF is required for displaced femoral neck fractures.
Prognosis
High risk of fat embolism syndrome and DVT/PE. Mortality rate in elderly patients is up to 20-30% at one year.
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Epidemiology & Etiology
High-energy trauma (MVA, falls from height) is the primary cause in young patients. In the elderly, low-energy falls on an outstretched limb or direct lateral impact are the most common mechanisms. Osteoporosis and vitamin D deficiency are critical underlying risk factors.
Pertinent Anatomy
The femoral neck is intracapsular, making it highly susceptible to disruption of the medial circumflex femoral artery. The femoral shaft is surrounded by massive musculature, capable of significant blood loss and muscle spasm.
Pathophysiology
Fractures result in significant hemorrhage, with a single femur fracture often sequestering 1.0–1.5 liters of blood. Muscle spasms cause the characteristic shortening and deformity. Disruption of blood supply to the femoral head leads to avascular necrosis.
Clinical Manifestations
Patients present with severe thigh pain and inability to bear weight. The limb is typically shortened and externally rotated. Fat embolism syndrome presents as a triad of hypoxemia, neurological abnormalities, and a petechial rash. Compartment syndrome is a surgical emergency requiring immediate fasciotomy.
Diagnosis
AP/Lateral Radiographs of the femur and hip are the initial diagnostic step. If radiographs are negative but clinical suspicion remains high, MRI is the gold standard for detecting occult fractures. CT scan is utilized for preoperative planning in complex comminuted fractures.
Treatment
Initial stabilization includes traction splinting and aggressive fluid resuscitation. Intramedullary nailing is the definitive treatment for shaft fractures. Displaced femoral neck fractures require ORIF or hemiarthroplasty in elderly patients. Do not delay surgery beyond 24-48 hours to reduce mortality.
Prognosis
Complications include nonunion, malunion, and infection. Prophylaxis against venous thromboembolism is mandatory for all patients. Long-term functional recovery is often limited in geriatric populations due to pre-existing comorbidities.
Differential Diagnosis
Hip dislocation: limb is internally rotated (posterior) or externally rotated (anterior) without fracture
Pelvic fracture: pain localized to the pelvic ring rather than the femur
Femoral neck stress fracture: insidious onset of pain, often in athletes
Septic arthritis: fever and elevated inflammatory markers
Pathologic fracture: history of malignancy or bone lesions