Proposed mechanisms of lower urinary tract injury in fractures of the pelvic ring.

OBJECTIVE: To investigate whether the observation of particular pelvic fracture patterns enables the clinician to predict the presence and type of injuries to the lower urinary tract, as the mechanisms of injury to the lower urinary tract in association with fractures of the pelvic ring are unclear.

PATIENTS AND METHODS: The case-notes and radiographs of 168 patients with either pelvic ring or acetabular fractures were reviewed; 108 pelvic ring fractures (81 men, 27 women) and 60 acetabular fractures (46 men, 14 women). The pelvic fractures were classified according to the system described by Tile and were correlated with the incidence and type of lower urinary tract injury (LUTI).

RESULTS: Overall, of the 108 men and women with pelvic ring fractures, 27 (25%) had a LUTI documented either radiologically or as an intraoperative finding. Of the 81 men with pelvic ring fractures, 24 (30%) had a LUTI, of whom six (7%) had an isolated bladder laceration, 14 (17%) a partial urethral injury (PUI) and four (5%) a complete urethral disruption (CUD). Five of the 18 men with urethral injuries also had bladder injuries and in three of these, the bladder neck was also injured. Three of 27 women (11%) had a LUTI, all of whom had isolated bladder lacerations. Of the 46 men with an acetabular fracture, one (2%) had a CUD, and three (7%) had a PUI. One of 14 of women with an acetabular fracture sustained a bladder laceration. None of the three men with a Tile Type-A pelvic ring fracture sustained a LUTI. Of the 28 men with 'open-book' (Tile Type-B1) fractures, 21 (75%) had no associated LUTI and seven (25%) had a LUTI (five partial urethral injuries and two bladder lacerations). Of the 10 men with 'lateral compression' (Tile Type-B2) fractures, six had no LUTI and four had a LUTI (two partial urethral injuries and two bladder lacerations). Of the 40 men with 'vertical shear' (Tile Type-C) fractures, 27 (68%) had no LUTI and 13 (32%) a LUTI (four complete urethral disruptions, seven partial urethral injuries, and two bladder lacerations) including all of the combined bladder and urethral injuries and all of the bladder neck injuries.

CONCLUSION: The pelvic fracture pattern alone does not predict the presence of a LUTI. When it occurs, the type of LUTI appears to be related to the fracture mechanism. The pattern of injury to the soft tissue envelope and specifically to the ligaments supporting the lower urinary tract offers the best correlation with the observed LUTI. We propose a mechanism for this.