Research Information System
ORTHOPAEDIC SURGERY, vol.6, no.1, pp.15-22, 2014 (SCI-Expanded, Scopus)
Objective: Although hip alignment and spinal alignment have been studied individually, there is little information concerning the relationship between them. The questions addressed in this study are: (i) Is there a reproducible measure of sagittal plane acetabular orientation; (ii) Is sagittal plane acetabular orientation determined more by pelvic incidence (PI) or acetabular wall coverage? Methods: Data on patients who had undergone screening by CT scan of the pelvis for non-orthopedic indications from 2005-2010 were retrospectively studied. There were 164 patients of mean age 59 years (range, 27-87). Patients with pelvic trauma, hip arthroplasty or other hip pathology were excluded. Measurements of relevant acetabular and spinopelvic variables were made in the sagittal plane. The sacro-acetabular angle (SA) was defined as the angle between a tangent line to the anterior and posterior walls of the acetabulum and the S-1 endplate. Multiple regression analysis was used to determine which factors contribute to SA angle. Results: The mean sacro-acetabular angle was 72 degrees (SD = 14.8 degrees). Center edge angles (CEAs) were measured at the anterior and posterior walls of the acetabulum. Mean anterior CEA was 69 degrees (SD = 8.3 degrees) and posterior CEA 107 degrees (SD = 16.4 degrees). Regression analysis revealed the largest significant predictors of SA angle were PI and A-CEA. Conclusions: Sagittal acetabular orientation is related to spino-pelvic balance and morphological characteristics. Increased PI or posterior wall coverage corresponds to a more vertical acetabular orientation. Sagittal plane acetabular alignment may be an important variable in achieving favorable results after reconstruction.