Abstract:

BACKGROUND: Stress shielding can influence the healing of fracture in the treatment of fracture healing by plate fixation.
OBJECTIVE: To observe the effect of dynamic stress plate (CO plate) and the normal stress plate (AO plate) on sheep femoral shaft fracture healing.
METHODS: Twenty-four healthy adult sheep were prepared for establishing the femoral shaft fracture model. After modeling, the models were divided into two groups: AO plate group and CO plate group. The fractures in the two groups were fixed with AO and CO plate respectively. The femurs with the internal fixation were picked out at 1, 2 and 3 weeks; conventional X-ray and MRI scanning were performed.
RESULTS AND CONCLUSION: X-ray film showed that there was no significant change at the fracture broken ends in two groups, and the fracture line was clear at 1 week after fixation; at 2 weeks after fixation, there was no significant change at the fracture broken end in AO plate group and the fracture line was clear, while in the CO plate group, the bone mineral density at the fracture broken end was increased and the fracture line began to blur; at 3 weeks after fixation, the bone mineral density at the fracture broken end in the AO plate group was increased, the bone mineral density in the CO plate group was increased continuously with the cloud-shaped external callus. MRI scanning showed that at 1 week after fixation, the T1 weighted imaging of the fracture broken end in two groups presented a high signal and the T2 weighted imaging on the fat saturation sequence presented a low signal, but the PDIR-TSE of the fracture broken end in the AO plate group showed a low signal and showed a high signal in CO plate group; at 2 weeks after fixation, T1 weighted imaging of the fracture broken end in two groups presented an equal or higher signal and the T2 weighted imaging on the fat saturation sequence presented a equal or lower signal, while the PDIR-TSE of the fracture broken end in the AO plate group showed a low signal and showed a high signal in CO plate group; at 3 weeks after fixation in the AO plate group, clearly fracture line could be seen, the T1 weighted imaging of the fracture broken end presented an equal or lower signal and the T2 weighted imaging on the fat saturation sequence presented an equal or lower signal, while the PDIR-TSE of the fracture broken end showed a low signal; at 3 weeks after fixation in the CO plate group, the fracture line at the fracture broken end was blur, the T1 weighted imaging of the fracture broken end presented an equal or higher signal and the T2 weighted imaging on the fat saturation sequence presented an equal or lower signal, while the PDIR-TSE of the fracture broken end showed an equal or higher signal. The blood circulation and the bone callus content at the fracture broken end in the CO plate group were higher than those in the AO plate group.