Cadaveric anatomy of pelvic fracture urethral distraction injury: most injuries are distal to the external urinary sphincter.

PURPOSE: The anatomy of posterior urethral distraction injuries is controversial. We present a cadaver study of posterior urethral distraction injuries. To our knowledge this is the first study that establishes that the most common location is distal to the external urinary sphincter.

MATERIALS AND METHODS: We performed an autopsy review of 10 male patients with posterior urethral distraction injuries.

RESULTS: Urethral disruption occurred distal to the external urinary sphincter in 7 of 10 patients. It appeared to occur when the anterior pelvic ring and urogenital diaphragm complex were displaced caudal and rostrally, tearing the urogenital diaphragm off of the urethra. The average inner mucosal defect +/- SD was 3.5 +/- 0.5 cm, while the defect between the outer urethral layer (tunica of the spongiosum) was 2.0 +/- 0.2 cm due to mucosal retraction. Simple and complex injuries could be observed, according to the clinical classification proposed by Turner-Warwick in 1989. Simple injuries had less significant dislocation of the symphysis, general maintenance of urethral continuity and slightly shorter mucosal distraction (3.3 cm). Complex disruptions had significant symphyseal dislocation, complete disassociation of the urethral ends (often with interposition of other tissues) and a slightly longer mucosal distraction (3.8 cm).

CONCLUSIONS: Posterior urethral distraction injuries appear to most commonly occur distal to the urogenital diaphragm, contrary to classic teaching. These injuries are on average between 3 and 4 cm, and they are more significant dorsal than ventral. They appear to occur as simple or complex injuries, mirroring the clinical findings seen in clinically simple and complex urethral strictures.