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Updated: Jun 18 2021

Sickle Cell Anemia

Images fish vertebra.jpg - knee - col_moved.jpg
  • summary
    • Sickle cell disease is a common genetic disorder of abnormal hemoglobin synthesis that causes affected blood cells to become "sickle shaped" with an inability to pass through blood vessels efficiently. Patients present with severe bone pain, acute hand swelling, and osteonecrosis.
    • Diagnosis is made with hemoglobin electrophoresis.
    • Treatment is medical management with hydroxyurea for sickle cell crises and monitoring for developing of osteonecrosis and osteomyelitis.
  • Epidemiology
    • Incidence
      • approximately 2 million Americans carry the sickle cell gene
        • 1 in 12 African Americans
  • Etiology
    • Two forms
      • sickle cell anemia
        • sickle cell anemia involves the presence of two abnormal hemoglobin S alleles
        • more severe form
      • sickle cell trait
        • sickle cell trait involves a single copy of the abnormal hemoglobin gene
        • usually asymptomatic
        • increased risk of sudden-death with exertion
          • due to collapse
          • responds early to oxygen, rest, hydration
        • more common
    • Pathophysiology
      • under low oxygen conditions the affected blood cells become "sickle shaped" and are unable to pass through vessels efficiently
    • Orthopaedic manifestations
      • sickle cell crisis (see below)
      • osteomyelitis
      • septic arthritis
      • osteonecrosis of femoral and humeral heads
      • bone infarcts
      • growth retardation / skeletal immaturity
      • dactylitis (acute hand / foot swelling)
  • Imaging General
    • Radiographs
      • recommended
        • AP and lateral standard of involved area
      • findings
        • bone infarcts common
        • biconcave "fishtale" vertebrae
    • MRI
      • recommended for differentiating bone infarction from osteomyelitis
        • obtain gadolinium enhanced T1 sequences which will identify infection
    • Bone Scan
      • helps differentiate infarct from infection
  • Studies General
    • Labs
      • serum
        • CBC, ESR, CRP
          • may be elevated in both osteomyelitis and sickle cell crisis
      • joint aspiration and culture
        • may be necessary to determine if diagnosis is osteomyelitis or sickle cell crisis
  • Sickle Cell Crisis
    • Presentation
      • severe bone pain
      • usually begins near age 2-3 years
      • caused by substance P
      • may lead to bone infarcts
    • Treatment
      • nonoperative
        • hydroxyurea provides
          • pain relief during bone crisis
  • Osteomyelitis
    • Introduction
      • often in diaphysis
      • organism
        • increased incidence of salmonella (may spread from gallbladder infection)
          • staph aureus and salmonella are the most common organisms causing osteomyelits in children with sickle cell disease, although unclear which is more common
          • salmonella osteomyelitis occurs most commonly in children with sickle cell disease
    • Imaging
      • radionuclide bone scan and radionuclide bone marrow scan can differentiate bone infarct from osteomyelitis
        • osteomyelitis: normal marrow uptake, abnormal bone scan
        • infarct: decreased marrow uptake, abnormal bone scan
    • Evaluation
      • aspirate and culture to differentiate from a bone infarct
  • Septic arthritis
    • Sickle cell patients are susceptible to infection due to
      • hyposplenia
      • sluggish circulation
      • decreased opsonization of bacteria
    • Presentation
      • bone pain
      • fever
    • Labs
      • elevated CRP and ESR
    • Studies
      • aspirate joint and culture to identify organism
    • Treatment
      • irrigation & debridement
        • consider preoperative oxygenation and exchange transfusion prior to surgery
  • Avascular Necrosis of Femoral Head
    • Osteonecrosis of the femoral head
      • can be bilateral in sickle cell disease
    • Presentation
      • hip pain with weight bearing
        • screening with hemoglobin to hematocrit ratio is the strongest predictor for osteonecrosis
    • Treatment
      • Nonoperative
        • partial weight bearing and range of motion
          • indications
            • initial treatment
      • Operative
        • total hip arthroplasty
          • indications
            • failed non operative
            • intractable pain
          • outcomes
            • results of total joint arthroplasty are poor due to ongoing remodeling of bone
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