The first step in the prediction of the future growth remaining in a limb or a limb segment is to determine the growth percentile or the relative size for age (chronologic or skeletal age) within which this limb or limb segment would lie relative to the standard growth records. This is very important because an individual growth tends to be within the same growth percentile throughout different growth phases [23] and in turn would allow us to track and predict the future growth remaining along the records of his peers within the same percentile till skeletal maturity. The growth percentile can be assessed by using different available age and gender specific growth tables and charts which document the average values and percentiles [22, 23, 36, 37].

The most complete set of longitudinal records of height and lower extremity growth in children and the most commonly used growth database in clinical practice is that published by Green and Anderson [22, 23]. Green, Anderson and Messner published two landmark studies. In the first one [23], they used longitudinal data for femoral and tibial lengths of healthy children, recorded by annual lower extremity radiographs from 1 to 18 years of age (67 boys and 67 girls). Those growth data were for North American white males and females of predominately Irish origin and were collected as a part of a longitudinal series of child health and development studies conducted at Harvard School of Public Health, Boston from 1930 to 1956 [38]. They were able to construct gender specific growth tables and charts based on chronologic age from 1 to 18 years defining annual average growth values and standard deviations or growth percentiles (mean ± 1 and 2 SD). In a separate work [22], they published growth remaining charts and tables for the normal femur and tibia relative to chronologic and skeletal age of 50 boys and 50 girls between the age of 8 and 18 years. Forty-nine children (25 girls and 24 boys) had unilateral paralytic poliomyelitis which affected only one lower extremity and therefore data of the healthy side were used. All children had annual orthoroentgenograms for the recording of femoral and tibial lengths as well as hand and wrist radiographic assessment of the skeletal age according to Greulich-Pyle Atlas [22, 26]. They further calculated the annual growth contribution and the growth remaining in the distal femur and proximal tibia (71 % of the total femoral growth and 57 % of the total tibial growth respectively) according to the skeletal age. Growth remaining tables and charts for the normal distal femur and proximal tibia were derived based on the skeletal age between 8 and 17 years with annual average values and four percentile levels (90th, 75th, 25th and 10th) and those tables and charts were the bases of Green and Anderson growth remaining method in predicting the optimal timing of epiphysiodesis. Green and Anderson work became the bases of Moseley straight line graph [39] and Paley’s multiplier method [24].

Other racial specific growth charts and curves were developed by Pritchett and Bortel [37] for Scandinavian American children in Denver, Colorado, by Beumer et al. [36] for Dutch children in Rotterdam, Netherlands and by Ha et al. [40] for Korean children. Beumer et al. [36] studied the femoral and tibial growth data in 182 Dutch children by serial orthoroentgenograms from 1979 to 1994. They found significant differences in the length of the femur in girls aged 8–9 years and boys 10–15 years and in the length of the tibia in boys and girls between the ages of 6–16 years. The Dutch children tend to be taller compared to the data of Anderson et al. [23]. They developed the Rotterdam straight line graph RSLG which is similar but not identical to Moseley straight line graph based on their own growth data.

Fredric Shapiro published an important article [34] in which he retrospectively reviewed longitudinal data of 803 children with LLD followed by the growth study unit at Boston Children’s Hospital over a 40-year period (1940–1980). All patients in this series were assessed at least annually (or more often semi-annually), for a minimum 5 years either to skeletal maturity or to the time of bony surgery. The disease entities which were included were: proximal focal femoral deficiency (PFFD), congenital coxa vara and congenitally short femur, Ollier’s disease, physeal destruction, poliomyelitis, septic arthritic of the hip, fractured femoral diaphysis, hemangioma, neurofibromatosis, hemiplegic cerebral palsy, hemiatrophy or hemihypertrophy, juvenile rheumatoid arthritis and Legg-Calvé-Perthe’s disease (LCPD). Shapiro was able to describe five main basic developmental patterns for progressive lower extremity length discrepancies (Table 46.3 and Fig. 46.2).

The calculation of the predicted LLD is easiest with type I discrepancies which increase at a constant rate during the whole growth. In other words, the percentage of the length achieved by the short limb relative to the healthy side at any age would be the same during the remaining growth and therefore, the first step is to determine the length percentile of the normal bone or limb and calculate its final length at maturity for that percentile. The short limb length is then easily calculated as a percentage of the normal side maturity length. Type II is a difficult pattern to project as the information available from the period of constant increase before the deceleration phase has no predictive value. Multiple assessments for the growth inhibition rate are needed to allow for additional calculations. An example of type II discrepancies is poliomyelitis in which there is a tendency for the discrepancy to increase most rapidly in the first four or five years following infection then the rate of increased discrepancy diminishes gradually thereafter. In type III patterns, once a plateau has reached, the LLD will be the same throughout the remaining growth. The typical example for type III LLD is the overgrowth following femoral shaft fractures. Type IV discrepancies were found to be characteristic for hip diseases in childhood. Premature closure of the proximal capital femoral epiphysis is the cause for the late upward slope following a long time of plateau phase and once detected, it is easy to calculate the remaining growth of the entire femur and to add a 30 % from that value (the contribution of the proximal femoral physis the normal femoral growth) to pre-existing discrepancy to give the final LLD. In type V, the discrepancy starts to correct itself. It is commonly seen in chronic inflammatory diseases which stimulates growth under 10 years of age and then causes premature growth cessation towards the end of growth.

Evaluation of the accuracy of the different methods used to predict final LLD at skeletal maturity was studied extensively by several authors [44–49].