Change in Effective Leg Length after Angular Deformity Correction by Hemiepiphyseal Stapling

BACKGROUND: The hemiepiphyseal stapling has both positive and negative effects on effective leg length. The purpose of this study was to analyze change in effective leg length after angular correction by hemiepiphyseal stapling, and to validate in clinical cases. METHODS: Mathematical analysis of a hemiepiphyseal stapling model was conducted. The induced formula was validated in 6 cases fulfilling the assumptions of the model. Anatomical parameters involved in this formula were measured in additional 21 cases undergoing hemiepiphyseal stapling or hemiepiphysiodesis. RESULTS: Effective leg length increased or decreased according to three parameters in this model: 1) limb length distal to the operated physis (L), 2) width of the operated physis (d), and 3) the amount of angular deformity to be corrected (θ). Actual change in effective leg length of 6 cases similar to this model coincided with the predicted change at least in its direction. L/d ratio was 4.82 ± 0.51. CONCLUSIONS: Considering the narrow range of the L/d ratio, hemiepiphyseal stapling is likely to decrease effective leg length if the amount of angular correction is less than 10°, whereas to increase it if the amount of angular correction is larger than 16°. This should be taken into consideration when selecting the surgical method for angular deformity correction in skeletally immature patients.