A technique for calculating limb length inequality and epiphyseodesis timing using the multiplier method and a spreadsheet

PURPOSE Limb length inequality and epiphyseodesis timing calculations are common in pediatric orthopedics. The multiplier method developed by Paley et al. has significantly simplified the calculation of ultimate limb length. The calculation of limb length inequality has also become very simple for congenital limb length inequalities. However, the equations for limb length inequality from acquired differences and epiphyseodesis timing are not simple, and are prone to arithmetic errors. METHODS To limit these errors, we have developed a spreadsheet which finds the appropriate multipliers, solves the equations, and computes the predicted limb length inequality and the appropriate age for an epiphyseodesis. RESULTS This method of using a spreadsheet and the multiplier calculations is quite simple and quick to use in practice. The calculations can be cut and pasted into computerized charts for future reference. CONCLUSIONS We recommend this method for clinical use and make it available for public use.