Three-dimensional morphological analysis of anterior and posterior acetabular notches in developmental dysplasia of the hip

Abstract:

Objective：Inappropriate acetabular cup placement significantly affects implant survival following total hip arthroplasty （THA）. However，there is a current lack of reliable intraoperative landmarks for guiding the anteversion placement of the acetabular cup during THA for developmental dysplasia of the hip（DDH）. In this study，we analyzed the morphological characteristics of the anterior and posterior acetabular notches（APANs） using three-dimensional（3D） computed tomography（CT） and assessed its potential as a safe reference landmark for anteversion cup placement in THA for DDH. Methods：The 3D-CT data of 22 healthy controls（44 hips） and 66 DDH patients（117 hips） between 2013 to 2018 were reviewed. Three anteversion angles defined by surgery，anatomy，and radiology were measured based on the line connecting the APANs. The relationships between each angle and the corresponding safe cup zone and between the angle and plain radiographic parameters in different hip types were analyzed. Results：The APANs could be clearly identified by CT，and the surgical anteversion of acetabular notch（SAAN） was within the safe zone（6°-36°） for both controls（22.4°±5.5°） and Hartofilakidis A DDH patients（25.5°±7.4°）. Compared with DDH patients with safe SAAN，those with unsafe SAAN had smaller lateral center-edge angle（5.6°±12.3° vs. -2.3°±13.0°，P=0.013），greater lateral subluxation（15.9 mm vs. 20.9 mm，P=0.006），and greater Tonnis angle（30.8° vs. 35.4°，P=0.005）. Conclusion：APANs can be easily identified by CT in healthy controls and Hartofilakidis A DDH patients，and may thereby serve as a good anatomical reference landmark for anteversion cup placement in sagittal view of the pelvis. SAAN-guided antever－sion cup placement should be avoided in DDH patients with reduced LCE angle，increased lateral subluxation，and increased Tonnis angle indicated by plain radiograph.