The Comparative Biomechanical Study Of Four Fixation Methods For Symphysis Pubis Diastasis

Objective: The rate of pelvic fracture account for 3-8%, but its death rate is beyond 10%. The rate of pelvic fractures with symphysis pubis diastasises is as high as 24%. Foreign orthopedic surgeons assume the theory that: the disruptions of symphysis pubis with more than 25mm of diastasis should been treaded using both open reduction and internal fixation, or external fixation. But there was not an uniform conclusion on means of fixation. The purpose of this study was to choose suitable clinical method according to experimental data of four fixation methods.Methods: Seven embalmed pelves, along with their spines intact from L5 to the sacrum, the proximal 2/3 of both femora, the intact major pelvic ligaments, and the intact hip joints were obtained. The mean age was 39 years (range, 19-65 years), and there were six males and one female. The pelves were loaded vertically in a test machine in a standing posture. The loads were applied through the L5 body to a maximum of approximately 400N while the displacements of the symphysis pubis were recorded. Testing was first performed on intact pelves and then the symphysis pubis,unilateral anterior sacroiliac joint,and ipsilateral sacropinous and sacrotuberous ligaments were cut. On each pelvis, a Type Bl injury was simulated. The following fixation were then applied: (1) two-hole 4.5mm dynamic compression plate fixed to the superior symphysis pubis with 2 cancellous screws, (2) four-hole 3.5mm curved reconstruction plate fixed to the superior symphysis pubis with 4 cortical screws, (3) four-hole 3.5mm curved reconstruction plate fixed to the anterior symphysis pubis with 4 cortical screws, (4) the Bastiani pelvic external fixator fixed to antersuperior. Results: The study showed that all fixations were able to reduce symphysis pubis gapping compared with the symphysis pubis diastasis. Under the same condiation, the symphysis pubis motion (0.213 ?.131mm )with intact pevic is the smallest, and the symphysis pubis motion (3.423 ?.514mm )with the symphysis pubis, unilateral anterior sacroiliac joint, and ipsilateral sacropinous and sacrotuberous ligaments were cut is the largest. The symphysis pubis motions with a sing two-hole 4.5mm dynamic compression plate and four-hole 3.5mm curved reconstruction plate to the superior symphysis pubis are 0.857 ?0.629rnnK 0.941 ?0.213mm .Their stability were no significant differences (p>0.05), but they were stronger than four-hole 3.5mm curved reconstruction plate to the anterior symphysis pubis and the Bastiani pelvic external fixator to antersuperior (p<0.05).Their motions are 1.301 ?0.873mm, 2.479 ?0.104mm .In which the Bastiani pelvic external fixator was the worst.Conclusion: (1) All of the four kinds of fixation can decrease the displacement of symphysis pubis, and it is the key to recovering the stability of pelvic. (2)The fixations with two-hole 4.5mm dynamic compression plate or four-hole 3.5mm curved reconstruction plate to the superior symphysis pubis can achieve the firm fixation.they are superior in biomechanics and clinical application.They deserves to be put into popularization. (3)The stability of pelvic with the Bastiani pelvic external fixator was the worst, but it can be used in emergent situation.