Variables associated with loss of reduction after plate fixation of pubic symphysis injuries

Purpose: To determine what variables are associated with loss of reduction of pubic symphysis injuries after plate fixation. Methods: A retrospective review of patients treated with plate fixation of symphysis injuries was performed. Symphysis diastasis on injury, postoperative, and follow-up radiographs was measured. Associations between patient, fracture, and fixation characteristics and a loss of reduction >= 10 mm were analyzed. Results: Fifty patients were included. The median age was 38.5 years (IQR 27.7 to 48.5), and a majority were male (80.0%, n=40). A loss of reduction >= 10 mm occurred in 18% (n=9), and revision fixation occurred in 6.0% (n=3). On univariate analysis, patients with a loss of reduction, compared to patients without, had a greater BMI (32.2 vs. 26.5, p=0.001), increased symphysis diastasis on injury radiographs (46.0 vs. 24.0 mm, p=0.0001), and more anterior pelvic space infections (55.6% vs. 14.6%, p=0.01). There were no associations between loss of reduction and age, AO/OTA classification, Young Burgess classification, 4-screw vs. >4-screw plate fixation, number of posterior screws, or residual post-fixation symphyseal diastasis (p>0.05). On multivariate analysis, initial symphysis diastasis was the only variable associated with loss of reduction >= 10 mm (p=0.03). A symphysis diastasis of >= 35.0 mm was found to maximize the sensitivity (88.9%) and specificity (75.7%) for identifying patients who had a loss of reduction. Conclusions: The severity of initial symphysis diastasis was associated with loss of reduction. A threshold of 35.0 mm of symphysis diastasis maximized the sensitivity and specificity for identifying patients who experienced a loss of reduction.