OBJECTIVE: Compare the biomechanical stiffness between the intact spine, the spine with burst fracture and the short-segment pedicle fixation on porcine thoracolumbar burst fracture. METHODS: 30 samples of thoracolumbar spine (T11-L3) of porcine were divided into three groups with 10 samples each. Group 1 represented the intact spine, Group 2 the spine with burst fracture and Group 3 the burst fracture associated with short-segment pedicle fixation. The burst fracture injury was created with a "V" shape cut of the third middle of the vertebral body compromising the L1 anterior and medial columns simulating the burst fracture. Group 3 was stabilized with Schanz pedicle screws. The groups were subjected to biomechanical testing in a controlled axial compression. The parameters of load (N) and displacement (mm) were generated in a graphic snapshot and stiffness (N/mm) was determined. The test was stopped when there was a sudden drop in the curve on the chart indicating failure of the sample. RESULTS: The stiffness of the fractured spines was 53% lower than the stiffness of the intact spine and this difference was statistically significant (p < 0.05). The stiffness of the short-segment pedicle fixation was 50% higher than the fractured spine. This difference was statistically significant (p < 0.05). The stiffness of the short-segment pedicle fixation was 30% lower than the intact spine. These differences were statistically significant (p < 0.05). CONCLUSION: The short-segment pedicle fixation does not provide sufficient stability to restore the stiffness of the intact spine during pure axial load compression biomechanical testing.
Spinal fractures; Biomechanics; Porcine
