Pattern of growth retardation after Blount stapling: a roentgen stereophotogrammetric analysis

The roentgen stereophotogrammetric method has been used in 19 children treated by Blount stapling for progressive leg length discrepancy. The growth plates of distal femur and/or proximal tibia were stapled with a total of 31 growth regions stapled. Longitudinal growth rate of 25 intact growth regions of distal femur and proximal tibia was determined and correlated well to growth rates as derived from growth tables of Green and Anderson and Kember and Sissons. In stapled growth regions, a uniform pattern of growth retardation was found and correlated well to skeletal age: the more advanced the skeletal age at time of stapling, the more pronounced and rapid initial growth retardation and the lower basal growth rate. Significant asymmetric growth was registered in 5 of 31 stapled growth regions, especially in three patients who developed loosening of staples. In five patients the staple tip motion was analyzed. Widening of staples and staple tip movements within the bony epiphysis and metaphysis were small. In the skeletally younger cases the widening and tip movement were more pronounced than in the older cases. In summary, the roentgen stereophotogrammetric method was used in order to analyze pre- and postoperative growth pattern and was found valuable in checking growth rates after Blount stapling to detect early complications such as asymmetric growth and loosening of staples. Furthermore, the movements and the deformation of the staples by the growth process could be evaluated with high precision.