Posterior pelvic ring involvement detected with CT taken within a week of admission in acute fragility fractures of the pelvis (FFP) does not predict failure of conservative treatment: a retrospective cohort study

BACKGROUND: Acute low energy pubic rami fractures in the elderly receive primarily conservative treatment. There is debate to what extent posterior ring involvement, which is detected superiorly by CT compared to X-ray, has an impact on outcome and may require modified treatment. We want to demonstrate if posterior ring involvement has an influence on different types of outcome in primarily conservatively treated acute FFP, questioning the usefulness of early CT. Additionally we analysed the early fracture pattern in cases where conservative treatment failed with need for secondary surgery. METHODS: A retrospective cohort study of 155 consecutive patients, recruited between 2009 and 2016, aged over 65 years diagnosed with an acute LE-PFr on X-ray at the emergency department of a single, level-one trauma centre and receiving an early CT. A set of outcome parameters was compared between patients with an isolated pubic rami fracture (CTia) and patients who had a combined posterior pelvic ring fracture (CTcp). RESULTS: There were 155 patients of whom 85.2% were female with a mean age of 83 years. 76.8% of patients living at home returned home and 15.5% moved to a nursing home. Mortality rate during hospitalisation was 6.4% and 14.8% at one year post-trauma. Secondary fracture displacement occurred in 22.6%. Secondary surgery was performed in 6 cases (3.9%). Median hospitalisation length of stay was 21 days (range 0 to 112 days). There was no significant association between the subgroups and change in residential status (p = 0.65), complications during hospitalisation (p = 0.75), mortality rate during admission (p = 0.75) and at 1 year (p = 0.88), readmission within 30 days (p = 0.46) and need for secondary surgery (p = 0.2). There was a significant increased median length of stay (p = 0.011) and rate of secondary displacement (p = 0.015) in subgroup CTcp. Secondary displacement had no impact on in-hospital complications (p = 0.7) nor mortality rate during admission (p = 0.79) or at 1 year (0.77). Early CT in patients who underwent secondary surgery showed stable B2.1 lesions in 4 of 6 cases. CONCLUSIONS: Our data suggest that early CT in patients with conservatively treated acute LE-PFr in order to detect posterior lesions, has limited value in predicting failure of conservative treatment. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12891-023-06439-1.