Diagnosis

61-B1 Open book injury (AP compression)

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61-B1 Injuries are unilateral, rotationally unstable in an external direction, which widens the anterior pelvis (“open book” injury).

The posterior pelvic arch injuries involve either the anterior part of the S-I joint, or fracture of the sacral ala which is wider anteriorly and in contact posteriorly. Rotational instability is present on physical exam and x-rays.

Options
1. 61-B1.1 Unilateral disruption of the anterior ligaments of the S-I joint
2. 61-B1.2 Unilateral partial injury of the sacrum with external rotation

1. 61-B1.1 Unilateral disruption of the anterior ligaments of the S-I joint

Posterior injury

Anterior injury

Posterior injury
The B1.1 posterior ring injury is a disruption of the anterior part of the sacroiliac joint. Its posterior S-I ligaments remain intact.

Anterior injury
The typical anterior arch injury produced by B1 injuries is disruption of the pubic symphysis. Less frequently, fractures of the pubis or rami may occur.
Anterior widening of the pelvis is evident as increased space between the two pubic bones, or fracture surfaces. Fractures are vertically oriented.

2. 61-B1.2 Unilateral partial injury of the sacrum with external rotation

Posterior injury
The posterior ring injury is a vertical fracture of the sacrum. It gapes anteriorly, but the posterior sacral cortical disruption remains in contact – as either an incomplete fracture, or an overlying soft-tissue hinge.

Anterior injury
The typical anterior arch injury produced by B1 injuries is disruption of the pubic symphysis. Less frequently, fractures of the pubis or rami may occur.
Anterior widening of the pelvis is evident as increased space between the two pubic bones, or fracture surfaces. Fractures are vertically oriented.