| Objective:Sacroiliac joint is located on the posterior ring of pelvis and it is the important structure to support the weight of the upper part of human body and complete the mechanics conducting. Its integrity of anatomy and function is most important to the pelvic ring. SI joint usually suffer the injury in the pelvic fracture, but it still did not cause enough recognition in surgical operation under medical treatment of the pelvic fracture to recover stability of SI joint .So its prognosis of long-term function is poor in clinic. So we carry out this biomechanical experiment to study the effect on pelvic stability with the disruption of SI ligaments and Separation of pubic symphysis, trying to gain the further understanding to the anatomy and function and providing the basis for the clinical treatment of the pelvic disruption.Methods: 20 short-term (in one year) embalmed pelves along with their spines intact from L4 to the sacrum, and hip joints with the 2/3 proximal of both femora were harvested for this study. All of these specimens were visually examined and then X-rayed to exclude the presence of pelvic bone or soft tissue disease. Care was taken to preserve the hip capsules, symphysis pubis, sacroiliac joint, sacrotuberous and sacrospinons ligaments. 20 specimens were divided into two groups randomly, 10 specimens per group. The group A was divided into two sides again, left and right, to start experiment respectively. In preparation for mechanical testing, one denuded femur were secured in the fixturn designed for test. Biomechanical testing was performed in model. Each specimen was loaded by vertical compression through the lumbar spine in a single-leg-stance model. The loads were applied at the speed of 5mm/min. It was increased in a continuous fashion until it reached 500N. In every step, the following data were recorded: the sacral rotation around the transversal axis(sacroiliac joint angulation) and its vertical displacement. For each pelvis, the micromotion of each SI joint was study separately in various states one after the other. Left side of group A: (1) intact pelvis; (2) section of the pubic symphysis ligament; (3) section of the sacrotuberous ligament; (4) section of the sacrospinous ligament; (5) section of the anterior SI ligament; (6) section of the interosseous SI ligament; Right side of group A: A gradual section in a order as follows: (1) long posterior SI ligament; (2) short posterior SI ligament; (3) iliolumbar ligament; (4) interosseous SI ligament. In every step, datum were recorded. Group B: (1) intact pelvis; (2) section of the pubic symphysis ligament; (3) To performant experiment with the pubic diastasis in sequence following : 0.5cm,1.0 cm,1.5 cm,2.0 cm,2.5 cm,and datum were recorded. (4) After the section of unilateral sacrospinous and sacrotuberous ligaments, pubic symphysis was separated to 3 .0cm,3.5 cm,4.0 cm,step by step. The experimental datum were analyzed by the one-way ANOVA in SPSS10.0 statistic software. The statistical significance for the test was set at P<0.05.Results: Left side of group A: In the successive loading test, the average vertical displacement increased from 4.144±0.538mm which measured in intact pelves to 5.853±0.368mm, the sacroiliac joint angulation varied from 0.226±0.061 to 0.616±0.086 degrees.Each index showed the significant increase. We found no further increase in the pubic symphysis joint motion; Further section of sacrotuberous ligament showed no evident change in vertical diaplacement while the average of angulation increasing, but had no statistical significance; When cutting off the sacrospinous ligament, sacroiliac joint angulation showed significant aggrandizement; When continuously cutting off the anterior SI ligament, two indexes showed no variety; When sectioned the interosseous SI ligament, the above indexes showed the significant increase (P<0.05). Right side of group A: In the successive loading test, the average vertical displacement increased from 3.610±0.696mm which measured in intact pelves to... |
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