The posterior and posterolateral surgical approach has been frequently used for total hip replacement arthroplasty (THA). But there is a risk of dislocation with this method and so several other methods for preventing dislocation have been presented. The short external rotator preserving technique is currently under the limelight and the reported clinical outcomes have been good. But we report here on one case of disruption of the piriformis muscle from the origin site due to excessive tension during total hip arthroplasty with using the short external rotator preserving technique. We think the conventional approach is safer than the short external preserving approach if excessive tension has to be loaded on the short external rotator for obtaining an appropriate intraoperative field for the patient with a large skeletal structure or the obese patient.