Radiographic evaluation of hip dislocations necessitating revision total hip arthroplasty

Although prosthetic hip dislocation is a common reason for revision arthroplasty, few studies have comprehensively evaluated the radiographic factors that may lead to the need for revision. Therefore, the authors radiographically evaluated all prosthetic hip dislocations that were treated at one institution. They then specifically assessed those that required revision surgery. The authors found that the prosthetic center of rotation (pCOR) was located superolateral and inferolateral to the native COR (nCOR) in all patients. Most hips had pCOR distances more than 5 mm from the nCOR. Furthermore, most patients had cup inclination and anteversion angles within Lewinnek's previously defined "safe zone." Determining these similarities and properly planning these procedures may help decrease the instability rate and therefore improve the overall success of this procedure.