Mobility and anthropometry of the sacroiliac joint: range of motion and morphological characteristics.

Purpose: The sacroiliac joint (SIJ), a synovial joint with irregular surfaces, is crucial for stabilizing the body and facilitating daily activities. However, recent studies have reported that 15-30% of lower back pain can be attributed to instability in the SIJ, a condition collectively referred to as sacroiliac joint dysfunction (SIJD). The aim of this study is to investigate how the morphological characteristics of the auricular surface may influence the SIJ range of motion (ROM) and to examine differences in SIJ ROM between females and males, thereby contributing to the enhancement of SIJD diagnosis and treatment.

Methods: We measured SIJ ROM using motion-analysis cameras in 24 fresh cadavers of Korean adults (13 males and 11 females). Using three-dimensional renderings of the measured auricular surface, we investigated the correlations between the morphological characteristics of the auricular surface and the ROM of the SIJ.

Results: The SIJ ROM was between 0.2° and 6.7° and was significantly greater in females (3.58° ± 1.49) compared with males (1.38° ± 1.00). Dividing the participants into high-motion (3.87° ± 1.19) and low-motion (1.13° ± 0.62) groups based on the mean ROM (2.39°) showed no significant differences in any measurements. Additionally, bone defects around the SIJ were identified using computed tomography of the high-motion group. In the low-motion group, calcification between auricular surfaces and bone bridges was observed.

Conclusion: This suggests that the SIJ ROM is influenced more by the anatomical structures around the SIJ than by the morphological characteristics of the auricular surface.