Table of Contents
ISRN Orthopedics
Volume 2013, Article ID 432675, 6 pages
Research Article

The Retroacetabular Angle Determines the Safe Angle for Screw Placement in Posterior Acetabular Fracture Fixation

1Trauma Division, Orthopaedic Department, University of BC, British Columbia, Canada
2Orthopaedic Department, Mafraq Hospital, Abu Dhabi, UAE
3Division of Orthopaedic Engineering Research, Departments of Orthopaedics and Mechanical Engineering, University of British Columbia, BC, Canada

Received 16 April 2013; Accepted 12 May 2013

Academic Editors: G. Babis and C.-H. Tsai

Copyright © 2013 Ayman M. A. Tadros et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Introduction. A method for the determination of safe angles for screws placed in the posterior acetabular wall based on preoperative computed tomography (CT) is described. It defines a retroacetabular angle and determines its variation in the population. Methods. The retroacetabular angle is the angle between the retroacetabular surface and the tangent to the posterior acetabular articular surface. Screws placed through the marginal posterior wall at an angle equal to the retroacetabular angle are extraarticular. Medial screws can be placed at larger angles whose difference from the retroacetabular angle is defined as the allowance angles. CT scans of all patients with acetabular fractures treated in our institute between September 2002 to July 2007 were used to measure the retroacetabular angle and tangent. Results. Two hundred thirty one patients were included. The average (range) age was 42 (15–74) years. The average (range) retroacetabular angle was 39 (30–47) degrees. The average (range) retroacetabular tangent was 36 (30–45) mm. Conclusions. Placing the screws at an average (range) angle of 39 (33–47) degrees of anterior inclination with the retroacetabular surface makes them extraarticular. Angles for medial screws are larger. Safe angles can be calculated preoperatively with a computer program.