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Objective : To determine the computed tomography (CT) appearance of minimally displaced type II odontoid fractures and the optimal protocols to evaluate these fractures by CT. Materials and Methods : The CT scans of five patients with minimally displaced type II odontoid fractures and 71 patients without odontoid pathology were reviewed for signs of fracture. A phantom consisting of a cadaver specimen with a type II odontoid fracture was evaluated with several protocols on four CT scanners. The protocols differed in slice thickness and reconstruction algorithm. Helical scanning was also performed, and parasagittal and coronal reformations were created from each image set. Main Results : Multiple cortical disruptions longer than 1 mm were demonstrated on the scans of all five patients with type II odontoid fractures. Only three of the 71 patients without odontoid fractures had multiple cortical disruptions, and none were longer than 1 mm. In the phantom study, thinner sections demonstrated cortical disruptions better than thicker sections. Similarly, images reconstructed with a bone reconstruction algorithm demonstrated the cortical disruptions better than images reconstructed with a soft-tissue reconstruction algorithm. Helical scans (1 mm thick) adequately demonstrated the reduced Type II odontoid fracture. Parasagittal and coronal reformations failed to demonstrate a fracture line through the base of the odontoid process on all image sets. Conclusions : Cortical disruptions greater than 1 mm and multiple cortical disruptions may be the only findings of odontoid fractures and should suggest the diagnosis. Evaluation of potential type II odontoid fractures is improved as CT section thickness is reduced (down to 1 mm) and is also improved by use of a bone reconstruction algorithm. The apparent absence of a fracture line through the base of the odontoid process on parasagittal or coronal reformations does not rule out the diagnosis.

The minimum volume of intraperitoneal fluid that is detectable in Morison's pouch with ultrasound in the trauma setting is not well defined. To evaluate this question, we used diagnostic peritoneal lavage (DPL) as a model for intraperitoneal hemorrhage and undertook a blinded prospective study of the sensitivity of ultrasound in detecting intraperitoneal fluid. Participants included attending physicians and residents in emergency medicine, radiology, and surgery. During the infusion of the DPL fluid, participants continuously scanned Morison's pouch until they detected fluid. All participants were blinded to the rate of infusion and the volume infused. One hundred patients were entered into the study. The mean volume of fluid detected was 619 mL. Only 10% of participants detected fluid volumes less than 400 mL and the overall sensitivity at one liter was 97%. We conclude that reliable detection of intraperitoneal fluid in Morison's pouch requires a greater volume than has been previously described.