Can Experts in Acetabular Fracture Care Determine Hip Stability After Posterior Wall Fractures Using Plain Radiographs and Computed Tomography?

Hip stability status after a posterior wall acetabular fracture involving 20%-50% of the posterior wall is difficult to determine. However, noted experts have professed that hip stability can be accurately determined by careful review of high-quality anteroposterior and oblique plain radiographs and a computed tomography scan. The objective of this investigation was to evaluate the interobserver and intraobserver reliabilities and accuracies in determining hip stability status by fellowship-trained orthopedic traumatologists expert in acetabular fracture care using these studies.Reliability and validation study.Level 1 trauma center.Fifteen patients with isolated unilateral posterior wall (OTA 62-A1) acetabular fractures involving 20%-50% of the posterior acetabular wall and known clinical outcome had undergone dynamic stress fluoroscopy under anesthesia to determine hip stability.High-quality anteroposterior and oblique plain radiographs and axial computed tomography images of 15 fractures involving 20%-50% of the posterior acetabular wall were reviewed in random order by 4 fellowship-trained orthopedic traumatologists specializing in acetabular fracture care in 2 separate sessions. The second session occurred after a minimum 1-month washout period. Determination of hip stability status was made for each fracture at the 2 time points based on the images along with any history of dislocation of the hip at the time of injury. These determinations were compared with the findings of examination under anesthesia, which served as the gold standard.Measurement of agreement using the Kappa statistic.Although intraobserver reliability was good (0.65), interobserver reliability was poor (0.12). In addition, percent correct was only 53% (32/60) for the initial reading and only 52% (31/60) for the second. For the initial reading, sensitivity and specificity were 100% (28/28) and 13% (4/32), respectively. For the second reading, the sensitivity and specificity were 57% (16/28) and 47% (15/32), respectively.Orthopedic traumatologists expert in acetabular fracture care cannot adequately determine hip stability status for fractures involving 20%-50% of the posterior wall using plain radiographs, computed tomography, and the patient's hip dislocation status. If the diagnosis is in doubt, open reduction and internal fixation clearly is the much safer course than nonoperative treatment. Examination under anesthesia should be considered as a helpful addition to the surgeon's armamentarium in determining hip stability status for these fractures.