The U-shaped sacral fracture is a fracture pattern poorly recognized, that is not included in the standard classification of sacral fractures. These fractures are significant as they represent spino-pelvic dissociation, have a high incidence of neurological complications and information regarding modern treatment options is sparse. A number of authors have reported isolated cases or small series of patients with this type of fracture, although none explicitly note the bilateral vertical element that makes them U-shaped and represents spino-pelvic dissociation. We present four patients with U-shaped sacral fractures. All patients were polytraumatised patients of whom three had jumped from a height in suicide attempts illustrating the high energy required to produce this fracture. Three patients had ilio-sacral screw fixation, supplemented in one with instrumentation from the lumbar spine to the iliac crest. The other had sacral laminectomy with bony stabilization by instrumentation from the lumbar spine to the iliac crest without ilio-sacral screw fixation. No complications were encountered as a result of fixation. The fixation devices used essentially represent the local expertise that is available. The ilio-sacral screw technique is minimally invasive and appears to provide satisfactory fixation in our limited experience. However as fracture deformity often involves rotation of the upper sacrum, the use of a single screw may not provide adequate support against the deforming forces or allow reduction of the fracture. Additional ilio-sacral screws will provide some rotational control of the sacral fragment if their safe insertion is possible, if not then the forces should probably be neutralized by an additional device from L5 to the pelvis. The role of sacral decompression is unclear but may be appropriate in the presence of neurological deficit and a severely compromised sacral canal. These are complex, rare injuries. We recommend their referral to a specialized pelvis/spinal unit for definitive management.
