There is evidence in several animal and human studies that high intramedullary pressure in the femur is of causal significance for bone marrow release into the circulation, causing pulmonary fatty marrow embolization. A previous clinical study provided evidence that in uncemented hip arthroplasty, high intramedullary pressure and subsequent fat embolism with cardiorespiratory deterioration can occur. In this prospective clinical trial, the effect of five surgical techniques on the femoral intramedullary pressure was recorded intraoperatively in 36 patients during uncemented press fit hip arthroplasty. In Group A, the conventional surgical technique (slide hammer and femoral rasps) showed intramedullary hypertension during opening of the femoral canal, femur preparation, and prosthesis insertion. In Group B, a mechanical high frequency vibration rasp was used, instead of the slide hammer, and provided reduction of the intramedullary pressure peaks during opening of the femoral canal but could not prevent intramedullary hypertension during rasping and prosthesis insertion. In Group C, a modified surgical technique to prevent high intramedullary pressure reduced pressure peaks during opening of the femoral canal and resulted in a significant reduction of intramedullary pressure during femur preparation and prosthesis insertion compared with the conventional surgical technique used with Group A. In Group D the results of the modified surgical technique could be improved additionally by using the high frequency vibration rasp, instead of the slide hammer. In Group E conventional surgical technique in combination with a distal venting hole has not proven to be efficient in uncemented hip arthroplasty. Based on the results of this in vivo study, the proposed modified surgical technique in cementless hip arthroplasty can be recommended to avoid high intramedullary pressure peaks, which should minimize the risk of significant bone marrow release into the circulation and the risk for cardiorespiratory deterioration caused by fat embolism.