Is there a correlation between fragility fractures of the pelvis (FFP) and the morphology of the true pelvis in geriatric patients?

PURPOSE: There has been no prior study to demonstrate the relationship between the occurrence of fragility fractures of the pelvis and its morphology. The aim of this study was to investigate the effect of pelvic morphology on fragility fractures of the pelvis caused by low-energy trauma in elderly female patients. MATERIALS AND METHODS: As a normal pelvis group, 643 female patients over 65 years of age who underwent pelvic CT were collected. Using three-dimensional multiplanar reconstruction (3D-MPR) function of RadiAnt software, the DT (diameter of transverse true pelvis)/DS (diameter of sagittal true pelvis) values of normal pelvis were measured. Sorted in ascending order, the mean DT/DS value of normal pelvis was 1.13 ± 0.09. The values corresponding to the 25th percentile and the 75th percentile were 1.06 and 1.18, respectively. We arbitrarily named DT/DS values of 1.06 or less corresponding to lower than 25th percentile as 'Circle types', and DT/DS values of 1.18 or higher corresponding to higher than 75th percentile as 'Ellipse types'. Total of 76 female patients over 65 years of age who underwent 3D reconstructions of pelvic CT scans with fragility fractures of the pelvis, who fell into the criteria corresponding to FFP classification type II, were studied separately. Of the 76 female FFPs, two were FFP type IIa, 32 were FFP type IIb, and 42 were FFP type IIc. Their DT/DS was measured. RESULTS: Based on the above mentioned criteria, we classified the pelvis shape of 76 patients with fragility fracture of the pelvis type II. 33 patients (43.4%) were classified as circle types and eight patients (10.5%) were classified as ellipse types. The odds ratio of "circle type" for fragility fractures of pelvis type II was 4.1. CONCLUSION: With digital reconstruction and 3D measurement of normal adult pelvic CT scans, this study obtained a series of DT/DS values describing the shape of true pelvises. Circle-type true pelvis was found to be more common in patients with fragility fracture of the pelvis type II.