Posterior Fixation of APC-2 Pelvic Ring Injuries Decreases Rates of Anterior Plate Failure and Malunion

Background: Biomechanical studies suggest that augmenting anterior fixation of the pelvic ring with posterior fixation increases stability. Prior clinical studies have assessed radiographic outcomes following plate fixation of the symphysis. However, to our knowledge, none have directly compared the radiographic and clinical outcomes of anterior plate fixation alone with the outcomes of such plate fixation with the addition of posterior percutaneous screw fixation in the treatment of a partially disrupted hemipelvis. We attempted to determine whether use of an anterior symphyseal plate alone is adequate to control sagittal and coronal plane rotation and prevent malunion of an anteroposterior compression type-2 (APC-2) pelvic ring injury. Methods: The records of all skeletally mature patients with a traumatic pelvic disruption treated from 2004 to 2014 with an anterior symphyseal plate with or without a posterior iliosacral screw were retrospectively reviewed. Patients with an APC-2 pelvic ring injury evidenced by computed tomography (CT) were included in the study and divided into 2 groups: (1) fixation of the symphysis with an anterior 3.5-mm 6-hole plate alone and (2) the same anterior fixation supplemented posteriorly with a percutaneous partially threaded 7.0 or 7.3-mm iliosacral screw. Postoperative CT scans were reviewed to assess the reduction of the pelvic ring and the position of all implants. The patients were followed for a minimum of 6 months or until the fixation failed. Examined data included demographic factors, type of and time to fixation failure, and presence of malunion. Univariate and multivariate statistical analyses were completed. Results: One hundred and thirty-four patients met the inclusion criteria. Ninety-two (69%) underwent combined anterior and posterior fixation, and 42 (31%) had anterior fixation alone. The average age and duration of follow-up were 38 years and 7.2 months, respectively. Anterior plate fixation failed in 5 patients (5%) in the combined-fixation group and in 17 patients (40%) in the anterior-only group (p < 0.0001). Malunion was identified in 1 patient (1%) in the combined group and in 15 (36%) in the anterior-only cohort (p < 0.0001). Conclusions: Our study indicated that use of an anterior plate and a supplemental posterior screw for fixation of APC-2 pelvic ring injuries significantly decreases the rate of anterior plate failure and malunion compared with use of an anterior plate alone. The potential for selection and detection bias introduced by our study design limited the strength of this conclusion.