Relationship between spinal sagittal alignment and acetabular coverage: a patient-matched control study

Introduction The significance of the relationship between the spine and hip joints has been frequently discussed. However, the relationship between acetabular coverage and spinal sagittal alignment has not been fully elucidated as previous studies did not adequately control for factors that might affect the spinopelvic alignment. The aim of this study was to elucidate the impact of acetabular coverage on spinal sagittal alignment by comparing patient groups matched on sex, age, and the presence of hip and anterior impingement pain. Materials and methods We prospectively enrolled 30 women undergoing periacetabular osteotomy (PAO) for developmental dysplasia of the hip (DDH) and 30 women undergoing hip arthroscopic surgery (HAS) for labral tears. The lateral centre edge angle was measured on hip radiographs. In addition, the sagittal vertical axis, pelvic tilt, pelvic incidence, sacral slope (SS), and lumbar lordosis (LL) were measured on preoperative plain radiographs of the whole spine to assess the sagittal spinal alignment. Clinical and radiologic data were compared between the two groups (PAO vs. HAS). Results The patient groups did not differ in age and body mass index. The mean SS was significantly greater in the PAO group (41.6 degrees 1.6 degrees) than in the HAS group (35.3 degrees +/- 1.5 degrees; P=0.0039). Additionally, the mean LL was significantly greater in the PAO group (54.5 degrees +/- 2.0 degrees) than in the HAS group (45.1 degrees +/- 1.9 degrees; P=0.0015). Conclusions The SS and LL were greater in patients with DDH than in patients with hip pain, but without DDH. Patients with DDH might show lumbar hyperlordosis to rotate the pelvis anteriorly, increasing the anterosuperior acetabular coverage.