Dr. Dror Paley is a doctor who specializes in lengthening reconstructive surgery (LRS) using the Ilizarov Technique. He wrote in his paper Lengthening Reconstruction Surgery for Congenital Femoral Deficiency
Classifications of congenital short femur and proximal femoral focal deficiency ( PFFD ) are descriptive but are not helpful in determining treatment....My classification system is based on the factors that influence the lengthening and reconstruction of the congenital short femur. [[Lengthening Reconstruction Surgery for Congenital Femoral Deficiency|Dror]]
His classification is based on the hip and knee structures.
Type 1: intact femur with mobile hip and knee
a) normal ossification proximal femur
b) delayed ossification proximal femur
Type 2: mobile pseudarthrosis (hip not fully formed, a false joint) with mobile knee
a) femoral head mobile in acetabulum
b) femoral head absent or stiff in acetabulum
Type 3: diaphyseal deficiency of femur (femur does not reach the acetabulum)
a) knee motion > 45 degrees
b) knee motion < 45 degrees