Radiological Assessment

Abstract

Conventional radiography is the first step in the radiological work-up of fragility fractures of the pelvis. Three views are obtained: the a.-p. pelvic overview, the pelvic inlet and pelvic outlet views. Fractures of the anterior pelvic ring are recognized easily. The inner curve of the innominate bone and the anterior cortex of the sacral ala are best evaluated on the pelvic inlet view. Shape and symmetry of the sacrum, neuroforamina and sacroiliac joints, and cranial displacements are best assessed on the pelvic outlet view. However, plain radiographs are insensitive for the detection of fractures in the posterior pelvic ring. Multidetector computed tomography is considered as imaging modality of choice, if involvement of the posterior pelvic ring is suspected or confirmed. Multiplanar reconstructions are nowadays available. Coronal reconstructions allow best assessment of the cranio-caudal extent of sacral ala and innominate bone fractures. Horizontal components and displacement of sacral fractures are best appreciated on sagittal reconstructions. Modern scanners with appropriate software tools deliver 3D displays that simulate conventional radiographs in the standard projections. 3D reconstructions provide a complete overview of the fractured pelvic ring, allowing the observer an outside view of the whole pelvis from every perspective. The main disadvantage of conventional CT techniques is their inability to detect microfractures of cancellous bone. Magnetic resonance imaging is a highly sensitive imaging tool in detecting and characterizing occult traumatic osseous lesions. MRI is recommended when detection of an additional fracture in the posterior pelvic ring has an implication on the choice of the therapeutic procedure. Bone scintigraphy with technetium Tc99^m medronate methylene diphosphonate (Tc-99m-labeled MDP) is a very sensitive method for the detection of sacral insufficiency fractures. The most important drawback is its low specificity as e.g. the inability to reliably differentiate between a fracture and a metastasis. In the era of multidetector CT scanners, 3D displays can be generated that very much resemble the pelvic a.p., inlet and outlet views. When a CT scan is quickly available and of optimal quality, conventional radiographs become dispensable. Conventional radiography still plays an important role in the assessment of reduction quality and fracture healing.