Data for the publication entitled - "Mobility of the sacroiliac joint in healthy young population"

Objectives
Pelvic incidence (PI) is acknowledged as the most significant geometric parameter of the pelvis. It has traditionally been considered a constant parameter, predicated on the assumption that the sacroiliac joint (SIJ) permits only minimal movement. However, we hypothesized that the SIJ is not a fixed joint in all cases even in healthy symptom-free population.

Methods
The study included 50 healthy young volunteers aged 19 to 25 years. EOS stereo-radiographs were obtained in weight-bearing standing positions, both normal, leaning forward and reclined. Three-dimensional reconstruction of the pelvic parameters was conducted using SterEOS software.

Results
We observed clinically significant differences in pelvic incidence when comparing leaned forward and reclined positions. The average pelvic incidence in a leaned-forward position was 48.58 ± 10.28°, and in a reclined position, it was 48.09 ± 10.74°. In the overall population, the mean absolute difference between the forward and reclined positions was 2.28 ± 2.35°. For men, this difference averaged 2.26 ± 2.78°, while for women, it was 2.30 ± 1.66° between the leaned forward and reclined positions. Absolute difference between forward and reclined positions exceeded 3° in 22% of the healthy population. Notably, in 4% of cases, the deviation surpassed 10°.

Conclusions
We identified a clinically significant difference in pelvic incidence between forward-leaning and reclined positions. This finding indicates that the sacroiliac joint exhibits not only micromovements in all individuals but also a potentially greater range of motion than previously acknowledged, even among a subset of the healthy young population.