Regarding the ossification of the femur, which statement correctly describes both primary and secondary ossification centers?
- A The primary center appears in the shaft (diaphysis) at 7th week of intrauterine life; the distal femoral epiphysis (lower end) is the first secondary center to appear at 36 weeks gestation and is a marker of fetal maturity ✓
- B The primary center appears at birth; the distal femoral epiphysis appears postnatally at 6 months
- C The proximal femoral epiphysis (upper end) appears before the distal epiphysis in fetal life
- D The primary center appears at 12 weeks gestation; the proximal tibial epiphysis appears simultaneously with the distal femoral epiphysis
Correct answer: A. The primary center appears in the shaft (diaphysis) at 7th week of intrauterine life; the distal femoral epiphysis (lower end) is the first secondary center to appear at 36 weeks gestation and is a marker of fetal maturity
Explanation
The primary ossification center of the femoral shaft appears at the 7th week of intrauterine life. The distal femoral epiphysis (lower end) is the first secondary ossification center to appear in the entire body, present at approximately 36 weeks gestation (term); its presence on neonatal radiographs indicates fetal maturity. The proximal femoral epiphysis (head) appears postnatally at approximately 6 months. The proximal tibial epiphysis also appears around 36–40 weeks gestation, but the distal femoral is slightly earlier and better established as a fetal maturity marker.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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