CT-based morphological study of the pelvis in patients with gluteal muscle contracture

BACKGROUND: In the clinic, gluteal muscle contracture (GMC) causes pelvic structural changes, including acetabular retroversion. However, its causes and forms are not well understood. This study aimed to investigate and analyse the clinical significance of pelvic structural differences between GMC patients and healthy individuals. METHODS: As the GMC group, we identified 100 GMC patients who received treatment and met the inclusion criteria between January 2019 and January 2020. Control subjects were drawn from the hospital’s emergency trauma patients who had no history of pelvic or hip joint disease. All subjects underwent CT scans to measure their pelvic rotation, including the superior iliac angle (SIA), inferior iliac angle (IIA), and ischiopubic angle (IPA), and acetabular coverage, which includes anterior acetabular sector angle (AASA), posterior acetabular sector angle (PASA), horizontal acetabular sector angle (HASA), and superior acetabular sector angle (SASA). RESULTS: The SIA, IIA, IPA, and PASA of the GMC group were considerably smaller than those of the control group, while the AASA of the GMC group was higher, indicating a statistically significant difference (P < 0.05). The HASA and SASA of the GMC group, on the other hand, were not considerably different from those of the control group. The angles in the GMC group were relativized as follows: The HASA had a positive correlation with the AASA and PASA (r = 0.750, P < 0.01; r = 0.749, P < 0.01); the SASA had a positive correlation with the AASA, PASA, and HASA (r = 0.555, P < 0.01; r = 0.273, P < 0.01; r = 0.552, P < 0.01); the AASA had a negative correlation with the SIA, IIA and IPA (r = − 0.355, P < 0.01; r = − 0.551, P < 0.01; r = − 0.30, P < 0.01); the PASA had a positive correlation with the IIA (r = 0.315, P < 0.01) and had no correlation with the SIA and IPA (P > 0.05); and the IIA had a positive correlation with both the SIA and IPA (r = 0.664, P < 0.01; r = 0.465, P < 0.01). CONCLUSION: Individuals with GMC have an abnormal pelvic morphology, with acetabular retroversion caused by ilial rotation rather than dysplasia of the acetabular wall.