ASD with High Pelvic Retroversion Develop Changes in Their Acetabular Orientation During Walking

Introduction: It was hypothesized that pelvic retroversion in Adult Spinal Deformity (ASD) can be related to an increased hip loading explaining the occurrence of hip-spine syndrome. Research question: How pelvic retroversion can modify acetabular orientation in ASD during walking? Methods: 89 primary ASD and 37 controls underwent 3D gait analysis and full-body biplanar X-rays. Classic spinopelvic parameters were calculated from 3D skeletal reconstructions in addition to acetabular anteversion, abduction, tilt, and coverage. Then, 3D bones were registered on each gait frame to compute the dynamic value of the radiographic parameters during walking. ASD patients having a high PT were grouped as ASD-highPT, otherwise as ASD-normPT. Control group was divided in: C-aged and C-young, age matched to ASD-hightPT and ASD-normPT respectively. Results: 25/89 patients were classified as ASD-highPT having a radiographic PT of 31 degrees (vs 12 degrees in other groups, p < 0.001). On static radiograph, ASD-highPT showed more severe postural malalignment than the other groups: ODHA = 5 degrees, L1L5 = 17 degrees, SVA = 57.4 mm (vs 2 degrees, 48 degrees and 5 mm resp. in other groups,all p < 0.001). During gait, ASD-highPT presented a higher dynamic pelvic retroversion of 30 degrees (vs 15 degrees in C-aged), along with a higher acetabular anteversion of 24 degrees (vs 20 degrees), external coverage of 38 degrees (vs 29 degrees) and a lower anterior coverage of 52 degrees (vs 58 degrees,all p < 0.05). Conclusion: ASD patients with severe pelvic retroversion showed an increased acetabular anteversion, external coverage and lower anterior coverage during gait. These changes in acetabular orientation, computed during walking, were shown to be related to hip osteoarthritis.