The myth of 2.5 cm symphyseal diastasis.

Detection of disruption of the pubic symphysis and resulting anterior pelvic ring instability primarily depends on the symphyseal widening on standard anterior-posterior X-rays. Based on biomechanical and clinical analyses from the 80 to 90's, a cut-off value of 2.5 cm widening distinguished between stable and unstable lesions. A relevant debate developed concerning minor (< 2.5 cm displacement), moderate (> 2.5 cm displacement) and severe disruptions (> 2.5 cm displacement + posterior complete pelvic ring instability) of the pubic symphysis. Analysis of anatomic, biomechanical, physiological and clinical literature showed, that an exact value does not allow this differentiation. Thus, symphyseal posttraumatic disruptions with displacements > 10 mm should be treated surgically, while in minor displacements (5-10 mm) stress examination can guide adequate treatment.