[Statics and dynamics after total hip arthroplasty. An electromyographic study (author's transl)]

The weightbearing of the hip of 147 patients after total prosthesis operation was controlled by the two wages method. In most of them the weightbearing becomes normal in a few months after the operation. In 39 patients with 48 total prostheses an electromyographic examination of the erectores trunci and the glutaei as well as the quadriceps of both legs in standing and walking was performed. In standing the patients demonstrate an hyperactivity of the paravertebral muscles and glutaei before as well as after the operation. They cannot find the normal standing posture with its typical lack of activity of the back, pelvis or leg muscles. In standing on one leg as well as in walking the innervation of the glutaei is diminished. In many cases it becomes normal after the total hip operation. Only in 1/3 of the cases we can observe a fully normal electrical activity of the glutaei with the classical "fan sign" which corresponds to the normal rotation of the pelvis during the stand phase. The erectores trunci demonstrate before and after the operation the same anomalies of innervation.