FETAL LONG BONES, HANDS AND FEET

HANDS AND FEET

• Confirm presence of both hands and feet
• Number of digits
• Size of digits
• Straight course of digits
• Normal relationship to distal long bones
• Metatarsals and carpus well ossified by 4 months.
• Carpal and tarsal bones are cartilaginous throughout pregnancy and only ossify after birth.
• Calcaneous and talus ossify at 5-6 months.

• Foot length (Table)– Chervenak et.al. 1992
• Foot length (Graph)– Chervenak et.al. 1992

LONG BONES

• Skeletal system develops from mesoderm
• Two types of ossification:
• Endochondral = ossification preceded by cartilage
  Þ Long Bones
• Intramembranous = ossification develops directly in the mesenchyme without cartilage formation
  Þ Flat Bones
• Normal ossification centers.
• Ossification in long bones proceeds in a set orderly fashion. It begins in the middle of the diaphysis and extends in both directions towards the epiphysis where two areas of cartilage are left. During the last weeks of the third trimester and in the early neonatal period ossification centers appear in the epiphysis and lead to bone formation. The metaphysis (cartilaginous) is the growing portion of bone, which ossifies in adulthood.
• Ultrasound.
• Length of proximal and distal long bones
  Femur
  Humerus, radius, ulna, tibia and fibula
  All end at the same level distally but proximally the ulna is larger than the radius ( helps to differentiate them).

• Ossification of long bones is determined by the echogenicity and acoustic shadow cast by the bone.
• Bone curvature is assessed subjectively.
• Normal continuity (discontinuities may be due to fractures, however shadowing from structures overlying the bone may give a similar appearance)