Pelvic incidence measurement using a computed tomography data-based three-dimensional pelvic model

OBJECTIVES: To introduce a new method of pelvic incidence (PI) measurement based on three-dimensional (3D) pelvic models reconstructed from CT images and to report the normal distribution of PI in normal pelvic anatomy. METHODS: CT images of 320 subjects with normal pelvic anatomy who visited the Radiology Department between 2006 and 2017 were retrospectively selected and saved in Digital Imaging and Communications in Medicine (DICOM) format. A computerized method was employed to determine the bony landmarks required for the measurement of PI. To quantify the method’s accuracy and reliability, the intraclass correlation coefficient (ICC) was calculated. A subgroup of 30 DICOM files was randomly selected to perform a validation study. Three independent testers performed all procedures. All measurements were performed twice independently by the three testers on all 10 subjects with an interval of 2 weeks. Independent samples t tests were used to identify statistically significant differences in the PI value between sexes. Pearson correlation coefficient was employed to determine the relationship between PI and age. RESULTS: PI measurement using the new method resulted in an excellent intraobserver reliability (0.9612, range 0.8917–0.9893; p < 0.001) and interobserver reliability (0.9867, range 0.9611–0.9964; p < 0.001). PI was significantly different between sexes, with larger PI in women (p = 0.019). PI was significantly larger in the 40–80-year age group (45.94 ± 9.08°) than the < 40-year age group (43.50 ± 7.39°). We did not find any linear correlation between PI and age in the male (r = 0.140, p = 0.105) or female subgroup (r = 0.119, p = 0.107). A weak correlation between PI and age overall was observed (r = 0.142, p = 0.011). CONCLUSION: Accurate PI measurement could be achieved by a CT data-based 3D pelvic model.