Paley et al. derived the multiplier method, a simple arithmetic formula for predicting limb-length discrepancy at skeletal maturity. The multiplier (M) is calculated by dividing mature limb length by limb length at each age, yielding age- and gender-specific values that are constant across all percentiles. The method was prospectively validated against the Moseley straight-line graph in 16 epiphysiodesis and 14 limb-lengthening patients.
Before this paper, predicting LLD at skeletal maturity required plotting multiple data points on the Moseley straight-line graph — a process so cumbersome that the method was frequently skipped in practice.
When a child presents with congenital LLD (fibular hemimelia, congenital short femur, hemihypertrophy), apply Δm = Δ × M using Table V and the child's age and sex. You need one radiograph and one multiplication.
For developmental LLD (physeal arrest, polio, Ollier disease), you need two interval radiographs to calculate growth inhibition, then apply Δm = Δ + (I × G). The same multiplier table gives you growth remaining.
The multiplier method only applies to Shapiro type-I (proportionate) LLD patterns. Before using it, confirm there are no periods of acceleration or deceleration in the discrepancy. Shapiro types II–V cannot be predicted with this or any existing formula.
For epiphysiodesis planning, remember the two key physeal contributions: distal femur = 71% of femoral growth, proximal tibia = 57% of tibial growth. These percentages, combined with the multiplier, let you calculate the precise bone length at which to perform the arrest.
Paley et al. derived the multiplier method, a simple arithmetic formula for predicting limb-length discrepancy at skeletal maturity. The multiplier (M) is calculated by dividing mature limb length by limb length at each age, yielding age- and gender-specific values that are constant across all percentiles. The method was prospectively validated against the Moseley straight-line graph in 16 epiphysiodesis and 14 limb-lengthening patients.
Before this paper, predicting LLD at skeletal maturity required plotting multiple data points on the Moseley straight-line graph — a process so cumbersome that the method was frequently skipped in practice.
When a child presents with congenital LLD (fibular hemimelia, congenital short femur, hemihypertrophy), apply Δm = Δ × M using Table V and the child's age and sex. You need one radiograph and one multiplication.
For developmental LLD (physeal arrest, polio, Ollier disease), you need two interval radiographs to calculate growth inhibition, then apply Δm = Δ + (I × G). The same multiplier table gives you growth remaining.
The multiplier method only applies to Shapiro type-I (proportionate) LLD patterns. Before using it, confirm there are no periods of acceleration or deceleration in the discrepancy. Shapiro types II–V cannot be predicted with this or any existing formula.
For epiphysiodesis planning, remember the two key physeal contributions: distal femur = 71% of femoral growth, proximal tibia = 57% of tibial growth. These percentages, combined with the multiplier, let you calculate the precise bone length at which to perform the arrest.