An in vivo study of the intervertebral movements produced by posteroanterior mobilization

Objective. To measure the intervertebral movements of the lumbosacral spine when it was subjected to posteroanterior mobilization. Design. An in vivo radiographic study. Background. Posteroanterior mobilization is frequently employed in the examination and treatment of low back pain, but its mechanical and therapeutic effects are uncertain. Methods. Lateral radiographs were taken of 12 healthy male subjects who were in prone lying. This was repeated while a static mobilization force of 150 N was applied vertically to their L4 spinous processes. The radiographic images of the vertebrae were traced and digitized. The sagittal rotation and translations of the motion segments, and the displacements of the spinous processes were then computed. Results. Under the application of the mobilization loads, the lumbar motion segments were found to extend, whereas the L5/S1 segment tended to flex. It was also shown that the upper lumbar segments (L1/2–L3/4) translated posteriorly and the L5/S1 segment anteriorly. The L4/5 segment did not exhibit translation in a consistent direction. In addition, all the spinous processes were found to be displaced anteriorly. Conclusions. The movement pattern observed in this study strongly suggests that the spine is subjected to three-point bending under the application of mobilization loads.