The concept of combined safe-zone delivers clear guidelines how to position both components of a total hip prosthesis in order to maximise range of movement and to reduce the risk of prosthetic impingement. It is the basis of the stem-first surgical technique. Computer-based navigation or mechanical instruments can be used to implement this new concept in surgical practice.

The results demonstrate that the knee still does not have a normal stability postoperatively, but the results were reproducible and the method appears to be reliable.