Pediatric Sickle Cell Disease Musculoskeletal

  • Etiology:
    — Sickling of red blood cells -> anemia -> marrow hyperplasia, marrow reconversion, extra-medullary hematopoiesis
    — Vascular occlusion -> bone infarcts, osteonecrosis
    — Osteomyelitis due to Staphylococcus aureus + Salmonella
  • Imaging:
    — Marrow hyperplasia: long bones – widening of metaphyses / widening of trabeculae / thinning of cortex / osteopenia, skull – widened diploic spaces
    — Bone infarct: in proximal femur / proximal humerus / distal femur / proximal tibia, lucency + sclerosis of medullary bone, cortical bone infarct -> periosteal reaction, H-shaped vertebra due to infarct of central part of vertebral body
    — Infection: see erosions / lysis / periosteal reaction, infarction vs. infection appear similar on MR as marrow edema and extra-osseous fluid collections but infarction has high signal intensity on T1WI with fat saturdation due to packed RBCs
  • Clinical: osteomyelitis is 50 times less common than osteonecrosis, suspect osteomyelitis if patient does not respond to conservative management / has asplenia or impaired complement and phagocytic activity
  • Spine T1 marrow changes
    — Age < 1 year – vertebral body signal decreased than adjacent disc — 1 year – 5 years – vertebral body signal = adjacent disc — > 5 years – vertebral body signal greater than adjacent disc
  • Extremity T1 marrow changes
    — There is fat in epiphysis within 6 months of radiographic appearance
    — Fatty marrow changes in diaphysis of humerus and femur begin by 1 year and complete by 10 years
  • Normal T1 marrow changes
    — During 1st and 2nd decade of life red marrow gradually converts to yellow (fatty) marrow
    — In each extremity, conversion occurs from periphery (fingers and toes) to center of body (shoulders and hips)
    — In each bone, 1st epiphysis, 2nd diaphysis, 3rd metaphysis
  • Marrow reconversion with anemia
    — Order of transformation back to red marrow is reversed
    — Epiphysis are the last part to reconvert

Radiology Cases of Sickle Cell Disease Musculoskeletal

Radiograph of sickle cell disease of the spine
Lateral radiograph of the thoracic spine shows multiple H-shaped vertebral bodies.
CXR of acute chest syndrome
CXR AP (left) shows a dense opacity in the left lower lobe which on the lateral (right) is seen to be located posteriorly, causing a spine sign. The lateral radiograph also shows the T8 and T10 vertebral bodes to be H-shaped.
CXR of H-shaped vertebral bodies in sickle cell disease
CXR AP (left) shows opacity in the left lower lobe that on the lateral (middle) is located posteriorly (spine sign). The vertebral bodies (right) have an H-shaped appearance throughout the thoracic and lumbar spine.