Review Question - QID 219207

A 26-year-old female presents to the trauma bay after a head-on motor vehicle collision. She is complaining of right hip pain, and initial radiographs demonstrate a posterior hip dislocation. The hip is reduced under propofol sedation and repeat radiographs are obtained confirming reduction. CT scan is then obtained and does not show any loose bodies but does demonstrate a posterior wall fracture. Which of the following is most accurate in predicting instability of the posterior wall fracture that would indicate an open reduction and internal fixation in this patient?