Multiplier method for predicting adult foot length.

Lower and upper limb lengths and total height can be predicted by the multiplier method. The multiplier is a coefficient that corresponds to each age and gender. The coefficient for any age can be multiplied by the length at that age to give the length at skeletal maturity. Our purpose was to calculate foot length multipliers and determine whether they are independent of percentile, much like the multipliers for lower and upper limb lengths and total height. Foot length multipliers were calculated from 3 separate previously published databases of foot length in children. The multipliers were calculated by dividing foot length at maturity by foot length at each respective age for each percentile and for both genders. The multiplier values for each percentile group at each age were found to be relatively equivalent, with little variability (as was found for the validated multipliers for lower limb length and total height). Also, little variability was found among multipliers calculated from different databases. In addition, we compared foot length multipliers with lower limb, upper limb, and total height multipliers. Compared with lower limb (tibial and femoral) multipliers, the foot length multipliers were significantly different because the foot achieves a higher percentage of maturity length earlier than does the femur or tibia. Because prediction of limb length and limb length discrepancy can be achieved accurately by using the lower limb multiplier, it is also likely that the foot length multiplier can be used to predict foot length and foot length discrepancy at maturity.

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.