[Imaging diagnose and clinical meaning for easy neglect occult posterior pelvic ring injury].

OBJECTIVE: To study the value of imaging diagnose and clinical meaning for easy neglect occult posterior pelvic ring injury.

METHODS: From Jan. 2003 to Jan. 2008, 178 patients with trauma of pelvic ring were reviewed. Routine AP view of pelvic computed radiographs (CR), axial, sagittal, coronal and curve multiplanar reconstruction CT (MPR) were performed. Spiral CT, slice thickness 3 mm,was carried out in all patients. There were 17 patients (11 males, 6 females, aged 19 to 71 years, mean 34.5 years) with obturator foramen aera fracture obviously but suspecting fracture or normal in posterior pelvic ring in AP view, which had imperceptible fracture changes in MPR. Routine radiographs and CT images studies and clinical physical examination correlation were evaluated retrospectively by anatomical region and classified using the Young-Burgess classification, Tile and AO classification.

RESULTS: In the remaining 17 patients with suspected fracture or normal in posterior pelvic ring, 5 cases of Denis I type of sacral fracture, 5 cases of Denis II type, 2 cases of Denis III type, 1 case of sacroilliac joint dislocation, 4 cases of sacral combined with posterior illiac fracture were diagnosed by MPR. Pelvic fracture categories were derived by adapting the Young-Burgess pelvic fracture classification scheme: lateral compression (LC) I and II, anteroposterior compression (APC) I. By adapting the Tile and AO classification schemes, the fracture were B1 and B2 type seperately. From the mechanism of trauma and assessment of pelvic stability point view, 15 cases were internal rotational unstability by lateral compression force, 2 cases were external rotation unstability by anteroposterior force. The omitted rate of posterior pelvic ring was 11% (17 of 128) by routine AP view of CR. 4D imaging reconstruction technique of spiral CT could detect all type of pelvic ring fractures (100%).

CONCLUSION: MPR CT could detect imperceptible fractures not been seen on AP view of CR of posterior pelvic ring and visualized sacral fractures better than the axial source images. MPR CT is accurate and reliable in occult posterior pelvic ring fracture for correct fracture detection and classification and guide therapeutic decision-making in patients with pelvic ring trauma.