Mechanical efficacy of different internal fixation devices in the treatment of thoracolumbar fractures

: To know the efficacy of different internal fixation devices used in the treatment of thoracolumbar fractures, specimens of 15 adult cadaveric (T-8 to L-4) were prepared and were divided into 5 groups for comparative study. Except the control group, the vertebra of T-12 of every specimen in other 4 groups was artificially fractured, imitating flexion fracture dislocation, with standard technic. Then, they were fixed in each group, with Luque's rod, Dick's screw, pedicle screw plate or Dunn's device respectively. The stress distribution and yielding stress under load and dimensional motions in each group were recorded and compared among the groups and with the control. In the experimental groups, Dunn's device gave the strongest support, against load on the anterior and middle columns. Dick's screw and pedicle screw plate could theoretically fix the anterior, middle and posterior columns rigidly; however, because of the weakness persisted in the connection of their components, their fixation effectiveness was reduced. Luque's rod acted though effectively against bending on every direction, it could not stand much axial load. It is obvious that each of these 4 devices has its own advantages and could be used to prevent horizontal displacement of the fixed fracture, but fail to control torsional stress.