Lumbosacral junction injury associated with unstable pelvic fracture: Classification and diagnosis

PURPOSE: To determine the types and prevalence of lumbosacral junction injuries associated with an unstable pelvic fracture and to assess the diagnostic value of conventional radiographic and computed tomographic (CT) findings. MATERIALS AND METHODS: Anteroposterior, inlet, and outlet radiographs and CT scans in 97 patients with pelvic disruption were retrospectively reviewed. RESULTS: Unstable pelvic fractures were seen on radiographs in 73 patients, 42 of whom had a sacral fracture. Fourteen of these 42 patients had an associated L5-S1 facet joint injury (three extraarticular, nine articular, and two complex). In three of these 14 patients, the L-5 body was laterally bent by more than 10 degrees, with asymmetric L5-S1 intervertebral space. The diagnosis in nine of the 14 patients with an associated lumbosacral junction injury was rendered on the basis of CT findings only. CONCLUSION: Lumbosacral junction injury must be considered in patients with an unstable pelvic fracture, especially in those with an associated sacral fracture. CT is necessary because these conditions may be overlooked on radiographs, although outlet radiographs are better than CT scans for depicting the possibly associated L5-S1 intervertebral disk lesion.