While sagittal alignment is known to significantly influence hip prosthesis positioning after total hip arthroplasty [1Kanawade. 2014.

Cliccare qui per andare alla sezione Riferimenti], the effect of sagittal alignment on acetabular orientation has not been previously studied in asymptomatic adult subjects. The aim was to elucidate the relationships between sagittal alignment and acetabular orientation using three-dimensional (3D) reconstruction of the hip in standing position. One hundred and seventy four hips of 87 asymptomatic adult subjects with no prior orthopedic treatment (age=21.5±2.2 years; 47 males and 40 females) that had undergone full body biplanar X rays, in standing position, with 3D reconstruction of the spine, pelvis and femurs were reviewed. Classic sagittal spino-pelvic alignment parameters were obtained as well as the following hip-specific ones: Lewinek vertical angle, acetabular anteversion (orientation of the acetabulum in the axial plane), abduction (orientation of the acetabulum in the frontal plane) and tilt (orientation of the acetabulum in the sagittal plane), percentage of femoral head coverage by the acetabulum. Pearson correlations were computed between acetabular parameters and sagittal spino-pelvic parameters. Stepwise multiple linear regressions were then used in order to elucidate the most determining sagittal alignment parameters for acetabular orientation. While the percentage of femoral head coverage was independent of all the sagittal alignment parameters, significant correlations (p<0.01) were found between pelvic tilt and acetabular anteversion (r=0.58), abduction (r=0.30) and tilt (r=0.51). Stepwise multiple linear regressions revealed that while pelvic tilt was the only determining factor among sagittal alignment parameters for acetabular abduction and tilt; acetabular anteversion (R²=0.35, p<0.01) was determined by both PT (β=0.59, p<0.01) and T1/T12 kyphosis (β=−0.14, p=0.02). Pelvic incidence was not a determinant factor for acetabular orientation and coverage. This is the first study that has shown a significant influence of sagittal alignment on acetabular parameters in asymptomatic adult subjects. Pelvic retroversion (increased pelvic tilt) led to an acetabular pattern of increased acetabular anteversion, abduction and tilt. This pattern could lead to increased posterior femoro-acetabular impingement and consequently osteoarthritis [2Tannast. 2015.

Cliccare qui per andare alla sezione Riferimenti].