RESUMO
Objective To test the biomechanical properties of symphysis pubis diastasis fixed by cannulated screw or reconstruction plate and provide the theoretical basis for clinical practice. Method In the experiment, fifteen normal adult specimens’ pelvis along with their intact spines from L5 to the proximal 2/3 of both femora were randomly divided into three groups. The symphysis pubis, unilateral anterior sacroiliac joint and ipsilateral sacropinous and sacrotuberous ligaments were cut; the intact major pelvic ligaments and hip joints were used to simulate Tile B1 pelvic fracture model. The fixation of five hole reconstruction plate and 6.5 mm cannulated screw were applied successively to cure symphysis pubis diastasis.The pelves were loaded vertically in the testing machine with a standing posture. The loads were applied through the L5 body to a maximum of approximately 400 N, while the displacements of the symphysis pubis were recorded. Results The study showed that two fixations were able to reduce symphysis pubis gapping and restore the biomechanical stability of pelves. Under the same condition，the displacement of symphysis pubis used 3.5 mm five hole reconstruction plate with 4 cortical screws, and the displacement by using cannulated screw were (0.944±0.983)mm and (-0.03±0.378)mm respectively. There were significant differences (P<0.05) between them. Conclusions The cannulated screw is superior to 3.5 mm five hole screw in biomechanical stability. The cannulated screw has fine biomechanical properties and is able to provide the firm fixation for symphysis pubis diastasis, which fits the principles of biological osteosynthesis.