Pelvic incidence: an anatomic investigation of 880 cadaveric specimens

Purpose: Pelvic incidence is a position- and posture-independent parameter used to quantify sagittal balance of the spine, sacrum, pelvis and hips. Its functional consequences have been associated with a number of different pathologies of the spine. However, there exists considerable controversy over which demographic features contribute to the development of pelvic incidence. Methods: 880 cadaveric skeletons from the Hamann-Todd Osteological Collection were obtained. The innominate bones and sacrum were reconstructed, and pelvic incidence was measured using a previously validated technique. Specimens with obvious fracture, infection, or rheumatologic conditions were excluded from study. Descriptive data of age at the time of death, gender, race and height were collected. Results: The average pelvic incidence was 46.0° ± 11.0°. Pelvic incidence did not change with age (r = 0.026, p = 0.288). There was no difference in pelvic incidence measurements between females and males (47.2° ± 13.8° vs. 45.8° ± 10.4°, respectively; p = 0.257), although this analysis was under-powered. Pelvic incidence was higher in African-Americans compared to Caucasians (48.9° ± 11.0° vs. 44.9° ± 10.8°; p = 0.001). There was no association between height and pelvic incidence (r = −0.042, p = 0.164). Conclusions: This study represents the largest single cohort of pelvic incidence measurements reported in the literature. Our data suggest that pelvic incidence does not change with age or height, although racial differences do exist. As spine care providers increasingly rely on pelvic incidence as an important means to quantify sagittal balance, the normative data provided herein will provide an essential reference.