Multiplier method for prediction of adult height in patients with achondroplasia

To date, the only way to predict adult height in achondroplastic dwarves has been to consult a growth chart. The purpose of this study was to ascertain whether the multiplier method of predicting adult height at skeletal maturity in healthy persons can be applied to persons with achondroplasia. Previous studies have shown that the multiplier method can be applied to lower limb length, upper limb length, total height, foot length, and foot height. It is therefore reasonable to suggest that the growth pattern for total height in achondroplastic dwarves might also be characterized by a multiplier. Total height multipliers for achondroplastic dwarves ("achondroplasia height multipliers") were calculated from two separate databases by dividing height at maturity by height at each respective age for both genders. Little variability was found among multipliers for each age and among multipliers calculated from different databases. Upper torso (sitting height) multipliers and lower limb multipliers were also derived for achondroplastic dwarves. Lower limb and total height growth rates were slower in achondroplastic dwarves compared with healthy persons. However, sitting height multipliers for achondroplastic dwarves were closely related to sitting height multipliers for healthy persons. Because these findings showed that the multiplier values were independent of population and percentile, the multiplier method may be a valid method for quickly predicting height at any age for achondroplastic dwarves.