Abstract: Objective    To digitally measure the relevant anatomical parameters of safe screw placement for posterior column wall of the acetabulum, so as to provide data reference for the clinical treatment of screw placement for posterior wall and/or posterior column fractures.   Methods   3D hip-bone models of 100 normal adults were reconstructed by Mimics 20.0. The acetabular posterior wall was divided into high posterior wall area involving the acetabular roof and the low posterior wall area without involving the acetabular roof. Sections M, D, E and N were obtained by cutting the high posterior wall area of the acetabulum, and sections F, G, H, I and J were obtained by cutting the low posterior wall area of the acetabulum. The following parameters were measured on each section: the angle and the length of the screw. Results    In the entry points 5.0 mm away from the acetabular edge on sections M, D, E and N, the maximum safe entry angles of screws for men and women should not exceed 80°, 70°, 60° and 50°, respectively, and the entry lengths for men and women should not exceed 40.0mm and 35.0mm, respectively. On sections F, G, H, I and J, the screw angles of 5.0 mm, 10.0 mm, 20.0 mm and 30.0 mm away from the acetabular edge should be less than 50°, 60°, 80° and 90°, respectively. On sections F to J, the screw lengths of male should be less than 40.0 mm, 35.0 mm, 30.0 mm, 30.0 mm and 40.0 mm, respectively, the screw lengths of female should be under 35.0 mm, 30.0 mm, 25.0 mm, 25.0 mm and 35.0 mm respectively.    Conclusions   Different insertion angles and lengths should be adopted at different insertion points in the posterior column wall of the acetabulum to avoid the screw entering into the hip cavity.

Key words: Acetabulum,  ,  , Posterior column,  ,  , Posterior wall,  ,  , Digitization,  ,  , Anatomical measurement