Comparison of Different Bone Age Methods and Chronological Age in Prediction of Remaining Growth Around the Knee

Abstract

Background: Bone age (BA) has been shown to be superior to chronological age (CA) when predicting remaining growth. However, it is not known whether the calculations are more accurate when BA is assessed by the Greulich and Pyle (GP) or the Sauvegrain (SG) methods. The aim of our study was to identify the method which gives an estimate closest to actual growth in the lower extremities. Methods: Leg length radiographs, hand radiographs, and elbow radiographs were simultaneously obtained during the adolescent growth spurt (10 to 16 years) in 52 children treated for LLD, with radiographic follow-up of segmental length (femur, tibia, and foot) until skeletal maturity, were randomly selected from a local institutional register. BA, according to GP and SG, were manually rated, and BA based on the GP method was additionally assessed by the automated BoneXpert (BX) method. The remaining growth was calculated based on the White-Menelaus method for both BA methods (GP, SG), the combination of the 2 methods, GP by BX, CA, and the combination of CA and GP by BX. Estimated growth was compared with the actual growth in the distal femur and proximal tibia from the time of BA determination until skeletal maturity. Results: For all included methods, the average calculated remaining growth was higher compared with the actual growth. The mean absolute difference between calculated remaining growth and actual growth in the femur and tibia was lowest using GP by BX [0.66 cm (SD 0.51 cm) and 0.43 cm (SD 0.34 cm)] and highest using CA [1.02 (SD 0.72) and 0.67 (SD 0.46)]. It was a significant association between calculated growth and the difference between actual and calculated growth for the SG method (P=<0.001). Conclusion: During the adolescent growth spurt, the GP method compared with the SG method and CA gives the most accurate estimate of remaining growth around the knee according to our results. Clinical relevance: In calculations of remaining growth around the knee, BA assessment by the GP atlas or BX method should be used as the parameter of biological maturity.