Musculoskeletal manifestations of sickle cell disease: an imaging perspective

Sickle cell disease (SCD) is a spectrum of inherited blood disorders, leading to propensity to sickling disruption of red blood cells. Musculoskeletal complications are a common cause of acute and chronic morbidities, related to the main pathophysiological processes: (i) hemolysis and anemia, resulting in marrow hyperplasia and extramedullary hematopoiesis; and (ii) vaso-occlusion, leading to osteonecrosis/bone infarction, myonecrosis, and infection (osteomyelitis and septic arthritis). Knowing the pathophysiology and clinical manifestations is essential for imaging interpretation, but differentiation between acute osteomyelitis and bone infarction remains a clinical and imaging challenge, therefore requiring a multidisciplinary approach. Large subperiosteal fluid collections (≥ 4 mm in depth), in conjunction with elevated inflammatory markers and white blood counts, are more suggestive of osteomyelitis rather than isolated bone infarction. The unenhanced T1-weighted fat-suppressed sequence on MR images was also proposed to aid in this differentiation, but so far with controversial results. Future perspectives of MR imaging include the DIXON technique, which has shown promising results as a biomarker of morbidity of SCD, through evaluation of fat fraction (FF) of bone marrow in a single acquisition and noninvasive way.