To evaluate the changes in the leg length discrepancy in idiopathic hemihypertrophy as a function of time.

A lower extremity scannogram was performed on 33 patients (16 boys and 17 girls) who were clinically diagnosed with idiopathic hemihypertrophy from September, 1985 to December, 1996. The leg length discrepancy was compared every 6 months. The mean age of the patients on the first visit was 1.6 years (range, 1 to 5 years) and the average follow up period was 9.1 years (range, 8 to 15 years).

Not all the discrepancies continued to increase at a constant rate with time. The developmental discrepancy patterns identified were classified as follows: type I, increasing pattern; type II, increasing-plateau pattern; type III, plateau pattern; type IV, increasing-decreasing pattern; type V, decreasing pattern. Twenty five patients (75%) had types I and II discrepancy patterns.

A continual periodic follow up of the leg length is important in idiopathic hemihypertrophy patients because the developmental patterns of a discrepancy in the length of a lower extremity can vary.