Forensic epidemiologic and biomechanical analysis of a pelvic cavity blowout injury associated with ejection from a personal watercraft (jet-ski).

Jet-propelled personal watercraft (PWC) or jet-skis have become increasingly popular. The means of propulsion of PWC, which is a jet of water forced out of small nozzle at the rear of the craft, combined with a high risk of falling off of the seat and into close proximity with the water jet stream, raise the potential for a unique type of injury mechanism. The most serious injuries associated with PWC falls are those that occur when the perineum passes in close proximity to the jet nozzle and the high-pressure water stream enters the vaginal or rectal orifice. We describe the forensic investigation into a case of an anovaginal "blowout" injury in a passenger who was ejected from the rear seat position of a PWC and subsequently suffered life-threatening injuries to the pelvic organs. The investigation included a biomechanical analysis of the injury mechanism, a summary of prior published reports of internal pelvic injuries resulting from PWC falls as well as other water sports and activities, and a comparison of the severity of the injuries resulting from differing mechanisms using the New Injury Severity Score (NISS). The mean (± standard deviation [SD]) NISS values for reported PWC injuries [not including the NISS of 38 in this case study] were 11.2 (± 9.5), while the mean value for reported water-skiing falls was half that of the PWC group at 5.6 (± 5.2). It was concluded that the analyzed injuries were unique to a PWC ejection versus other previously described non-PWC-associated water sport injuries. It is recommended that PWC manufacturers help consumers understand the potential risks to passengers with highly visible warnings and reduce injury risk with revised seat design, and/or passenger seat "deadman" switches.