Acute traumatic intraosseous fluid sign predisposes to dynamic fracture mobility

The intraosseous fluid sign (IFS) in chronic osteoporotic vertebral fractures is attributed to fluid accumulation within non-healing intervertebral clefts. IFS can also be seen in acute traumatic fractures, not previously described. We hypothesize a pathophysiological mechanism for the acute traumatic intraosseous fluid sign (ATIFS) and its predisposition to dynamic fracture mobility with axial loading on upright radiographs. Retrospective analysis was performed of 41 acute thoracic and lumbar compression or stable burst fractures with both supine CT and upright plain films completed within 1 week of each other. The presence of an intravertebral cleft with fluid attenuation and vertebral body height loss was assessed on CT scans. Changes in the fractured vertebral body height and angulation were measured on upright radiographs. The ATIFS was identified in 18 (44%) of the 41 acute fractures. Mean kyphotic angle increase was significantly greater (p = 0.000) for ATIFS fractures (8.2°, SD ±4.2) than fractures without ATIFS (1.6°, SD ±3.4). There was significantly greater mean anterior (p = 0.0009) and central (p = 0.026) height loss in ATIFS fractures (4.3 mm, SD ±3.76 and 1.89 mm, SD ±4.44, respectively) compared to fractures without ATIFS (0.59 mm, SD ±2.24 and -0.52 mm, SD ±2.01, respectively). The IFS can be seen in acute traumatic vertebral fractures and show dynamic mobility. These ATIFS fractures show statistically significant greater mean height loss ratio differences and have significantly greater changes in kyphotic angulation on upright imaging when compared to fractures without ATIFS.