Skeletal growth and development of the achondroplastic dwarf.

Certain patterns in growth and development can be seen in the typical achondroplastic dwarf. Height is approximatley 5 standard deviations below average size for age through the age of 14. Sitting height is within normal limits at all ages. On the average the femur is 8 standard deviations and the tibia 7 standard deviations below normal size. Compared to normal, both femur and tibia exhibit approximately a 50 per cent inhibition in growth. A slight decrease in the deviance from the norm is observed for all parameters during growth until the time of the adolescent growth spurt when an increased deviance is seen. Related to normal children of the same sex and age, females are more severely affected than male achondroplastic dwarfs. The skeletal development of the hand is irregular, often having extra metacarpal epiphyses and a wide variance in skeletal maturation assessment between the carpals and the rest of the hand. The skeletal age is generally below chronological age until the adolescent growth spurt when a rapid maturation pattern occurs. Standard skeletal age assessment techniques cannot be applied to the achondroplastic individual.