Session VII - Pelvic Trauma

Nonoperative Management of Acetabular Fractures: The Use of Dynamic lntraoperative Stress Views

Paul Tornetta, III, MD

University Hospital, Brooklyn, New York, USA

Introduction: The outcome of acetabular fractures lies in the reduction of the roof (weightbearing surface), the concentricity of the head under the roof, and the stability of the hip. In continued efforts to identify which fractures require fixation, Matta has described the use of roof arcs and later, the CT correlate of roof arc measurements. He and others have also recommended surgery for posterior wall fractures that create hip instability, although the percentage of posterior wall injury is not clear. General guidelines for nonoperative management include minimal displacement (<2mm) and displaced fractures in which the head is congruent with the roof of the acetabulum on the AP and both Judet views and the posterior wall is affected less than 50% on all CT cuts (Olson and Matta). However, a dynamic test of stability has not been described. The purpose of this study is to describe the use of an intraoperative fluoroscopic stress test to further evaluate the stability of the hip in acetabular fractures that otherwise meet the guidelines for nonoperative management.

Methods: Over a four year period, 41 acetabular fractures meeting the above criteria for nonoperative management were treated by the author. Superior rami fractures that entered the inferior portion of the acetabulum were not included. There were 14 posterior wall (62-Al), 10 very low anterior column / wall (62-A3.1), 9 transverse, 6 T-shaped (62-B2.1), and 2 posterior column fractures (62-A2). Nine patients had associated pelvic fractures of which 4 were operative (3 symphyseal dislocations, 1 sacral fracture). In all cases the roof of the acetabulum was intact as determined by intact 45° roof arcs on plain films and the 1 cm acetabular ring on the CT scan. The head was congruent to the roof on the AP and Judet views and at least 50% of the posterior wall was intact on all CT cuts. All patients were brought to the operating room for fluoroscopic stress views of the hip under anaesthesia. These were performed by first ranging the hip in flexion, extension, and abduction while rotating internally and externally in each position. This was followed by applying moderate force in the direction of the displacement for the given fracture pattern. For example, posterior wall fractures were stressed in flexion and internal rotation. This series was repeated while viewing the hip in the AP, obturator, and iliac oblique views. The fluoroscopic image was evaluated dynamically for change in congruity of the femoral head with respect to the acetabulum and the stress position saved on the screen. The normal side was used as a comparison when needed. Hips that were stable were managed nonoperatively regardless of the displacement or fracture pattern.

Results: The average displacement of the fractures was 5 mm. The stress view showed some motion of the fracture in 12 cases. In three cases the femoral head was demonstrated to sublux away from the roof indicating instability. This occurred in 1 transverse and 2 posterior wall fractures. Two of these hips subluxed with range of motion alone and one only with stress applied. All three were fixed anatomically. The other 38 acetabular fractures were managed with early motion and toe touch ambulation (the same protocol as after operative fixation). Four patients were lost to f/u including one operative case. The other cases were followed for an average of 2 years and 3 months. None of the cases managed nonoperatively have significant hip or groin pain in followup. However, one has very minimal incongruence of the head with the roof and one has minimal joint space narrowing at 3 years. The clinical results are excellent or good in 32/35 nonoperative patients (91%). The other 3 have fair results due to other components of their injury but have no hip or groin pain. Of the patients treated operatively who have followup, one has an excellent and one a good result.

Discussion: Displaced acetabular fractures that do not enter the roof and are not subluxed present a difficult management decision. The choice of operative vs. nonoperative management must be made on the basis of improving on the natural history of the injury and tempered by the risks of major surgery. The outcome of acetabular fractures is dependent on stability and congruence of the hip. Olson and Matta have described utilization of static radiographs and CT evaluation to confirm stability and congruence and reported good or excellent results in 82% of fractures meeting their criteria that were treated nonoperatively. The addition of a stress view to rule out dynamic instability has increased this to 91% and identified one possible cause of failure in patients treated nonoperatively. In this series 3/41 (7%) hips that met the standard static radiographic criteria for nonoperative management had instability of the hip that was demonstrable using fluoroscopy.

Conclusion: Fluoroscopic stress views under anaesthesia provide an additional method of evaluation for acetabular fractures that are being considered for nonoperative management. This technique can identify dynamic instability of the hip.