Evaluation of pelvic morphology in female patients with developmental dysplasia of the hip using three-dimensional computed tomography: A cross-sectional study.

BACKGROUND: The purpose of this study is to measure pelvic morphology with respect to the pelvic incidence, pelvic tilt, and sacral slope using 3-dimensional measurement and to compare the pelvic morphology between the normal population and women with developmental dysplasia of the hip (center-edge angle, <25°). We hypothesized that the relationship between pelvic incidence, anatomical pelvic tilt, and anatomical sacral slope would be different between normal subjects and patients with developmental dysplasia of the hip.

METHODS: We evaluated 61 healthy women without low back or knee pain and 71 patients with developmental dysplasia of the hip. We used the 3-dimensional pelvis model adjusted to the anterior pelvic plane and measured the pelvic parameters. To determine correlation, we used Pearson's coefficients. To evaluate variation, we used intraclass correlation coefficients.

RESULTS: Pelvic incidence and anatomical pelvic tilt were significantly greater by 4° in the group with developmental dysplasia of the hip than in the normal group (p = 0.026 and < 0.001, respectively). The vertical distance from hip axis to the center of the S1 endplate was significantly greater in the group with developmental dysplasia of the hip than in normal group, that is, by 8 mm (p < 0.001). There was a strong correlation between pelvic incidence and anatomical sacral slope in both groups (R = 0.707 and 0.897, respectively). The intraobserver and interobserver mean absolute differences were about 2 mm and 2°, respectively, and the intraclass correlation coefficient was >0.88.

CONCLUSION: Pelvic incidence and anatomical-pelvic tilt were significantly greater in patients with developmental dysplasia of the hip. We found a strong correlation between the pelvic incidence and anatomical sacral slope in both groups. Therefore, anatomical-sacral slope may be useful for estimating pelvic incidence because it is not easily measured, especially in patients with osteoarthritis of the hip joint.