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

Table 1

Example of the computed allowance angles for each one mm of medialization of screw site in the posterior acetabular wall for a patient with a retroacetabular angle of 42 degrees and a retroacetabular tangent of 32 mm as it appears in our computer program.

Retoacetabular tangent length; (𝑡) = 32 mm	Retroacetabular angle; (𝜃) = 42 degrees
Medialization distance (mm)	Allowance angles (degrees)
0.01	0.012
1.0	1.24
2.0	2.52
3.0	3.87
4.0	5.28
5.0	6.76
6.0	8.31
7.0	9.93
8.0	11.63
9.0	13.40
10.0	15.25
11.0	17.19
12.0	19.20
13.0	21.30
14.0	23.47
15.0	25.73
16.0	28.05
17.0	30.45
18.0	32.92
19.0	35.44
20.0	38.01
21.0	40.63
22.0	43.27
23.0	45.94
24.0	48.61