Human fetal femoral head sphericity

The question of decreasing sphericity of the human femoral head during fetal growth was investigated with a Talyrond roundness-measuring machine. In 58 pairs of randomly selected femore, from 12 weeks to term, there was a trend for the femoral head to become less round with age and more oval or ellipsoidal in shape. At term a position of best "fit" may exist. No significant laterality or sex differences were found. Restriction of joint motion towards the end of pregnancy may decrease congruency, decrease joint stability, and become a factor in neonatal hip instability.