Risk factors for pubic ramus fracture nonunion after conservative treatment of pelvic ring injuries: a retrospective cohort multicenter study

Purpose: To determine the incidence of nonunion, clinical and radiological outcomes, and risk factors for nonunion in conservatively treated pubic ramus fractures among patients diagnosed with pelvic ring injury.

Methods: A total of 546 patients (192 men, 354 women) diagnosed with pubic ramus fracture, treated conservatively, and who had completed > 1 year follow-up at three level 1 trauma centers between January 2014 and December 2020, were enrolled. Clinical and radiological evaluations were compared between union and nonunion groups. Logistic regression and Kaplan-Meier analyses were used.

Result: At the final follow-up, 527 (96.5%) and 19 (3.5%) patients had union and nonunion of fractures, respectively. The union and nonunion groups exhibited statistically significant differences in posterior injury (p = 0.040), bilateral ramus fracture (p < 0.001), initial displacement (p < 0.001), and clinical result (p < 0.001). In the multivariate logistic regression analysis, initial displacement (odds ratio, 4.727; p = 0.005) was analyzed as a risk factor for nonunion. According to the Kaplan-Meier analysis, the median initial displacement of nonunion occurrence was 17.9 mm (standard error, 1.211; 95% confidence interval 15.526-20.274), and nonunion patients were included if the displacement was > 15.9 mm (standard error, 1.305) on the 75th percentile.

Conclusion: Conservative treatment is ineffective in some ramus fracture cases with pelvic ring injury. As ramus nonunion causes functional deterioration, active treatment is required if the displacement is ≥ 16 mm.