Biomechanical evaluation of hip joint after Salter innominate osteotomy: along-term follow-up study

The biomechanical state of the hip after a Salter innominate osteotomy was investigated by using the radiographic data of 38 operated and 21 contralat eral nonoperated hips from our archives. The centre-edge angle of Wiberg wa s determined from the radiographs taken shortly after the operation. From t he radiographs of the latest follow-up (7-13 years after the operation), we also determined the peak value of contact hip joint stress normalized by t he body weight, and the functional angle of the weight-bearing area. A math ematical model was used. We show that the geometrical parameters aside from the centre-edge angle may considerably influence the contact hip stress di stribution. We also show that the functional angle of the weight-bearing ar ea is a more relevant parameter than the normalized peak stress if the exac t magnification of the images is not known and if there is considerable var iation of the image size within the sample. The development of the centre-e dge angle of the operated hips and of the contralateral hips was also studi ed. We found that the centre-edge angle increases on average during the fol low-up time in the operated hips as well as in the contralateral nonoperate d hips, but the average increase is smaller in the former. It is shown that an unfavorable stress distribution is connected to the decrease of the cen tre-edge angle over time. Finally, we found a weak positive correlation bet ween the centre-edge angle shortly after the operation and the functional a ngle of the weight-bearing area at the of the latest follow-up.