Biomechanical Study For Stability Of Pelvic And It's Sacroiliac Joint Screws Internal Fixation

Objective:1. The aim of this study was to determine the stabilizing effect of different pelvic ligaments for the pelvic ring.2. Through a biomechanical comparison of six techniques of sacroiliac screw fixation for unstable pelvic sacroiliac dislocation ,the purpose of this study was to offer the most reliable fixed methods in clinic。Methods:We used 12 embalmed cadaveric pelves . The average age of the specimens was 42 years (range 34–65). The pelves, including the lower lumbar vertebrae of L5, were harvested and stripped of all muscle, leaving the pubic symphySIs and pelvic ligaments (sacrospinous, sacrotuberous, anterior and posterior sacroiliac) intact. None of the pelves had any gross structural or radiological abnormalities. The pelves were loaded vertically in a test machine in a standing posture. The cyclic loads were applied through vertebral body of L5. Using the biomethanics experiment ,stress analytical method, test the stability of them.1. Under the maximum of approximately 500N , adopt 6 adult pelvis samples randomly, using the biomethanics experiment ,stress analytical method, systematically test the stability of every pelvic in quence as follow : N-A₁-B₁-C₁-D₁. Test was initially performed with the intact pelvic. After the intact patten(Group N: intact pelvis)was recorded, A progressively more severe injury(Tile C) was simulated by disrupting the following structures in sequence and sequential tests were performed. A₁: Sectioning the symphsis pubis ligament; B₁ Sectioning the sacrospinous and sacrotuberous ligaments on the base of A₁; C₁: Sectioning the anterior sacroiliac joint ligaments and capsule on the base of group B₁; D₁: Sectioning the posterior sacroiliac ligaments complex on the base of group C₁.2. Twelve pelves were divided into six groups randomly. In each pelvis, we created a Tile C pelvic ring injury with a symphysiolysis and sacroiliac dislocations on both sides. the pubic symphysis was fixated with plate and screws. Each SIJ was fixated with one of the following methods: A 1 sacroiliac screw(6.5×70mm) in the vertebral body of S₁; B 2 screws(6.5×70mm) convergingly in S₁; C 2 screws (6.5×70mm), 1 in S₁ and 1 in S2; D 2 screws (6.5×40mm),1 in S₁ and 1 in S₂; E 1 screw(6.5×70mm) and 1 screws(6.5×40mm) convergingly in S₁; F 1 screw(6.5×70mm) in S1 and 1 screw (6.5×40mm)in S2; Six internal fixation methods were performed. the same screw techniques were used on both sides.Results:â‘ The symphysis pubis ligaments and anterior ligaments contribute to the pelvic stabilityâ‘¡The sacrospinous and sacrotuberous ligaments have little effect on the pelvic stability ,the posterior sacroiliac ligaments complex contribute most to the sacroiliac joint stability.â‘¢.The mechanics performance of Group C and F were better than other groups ,Their emergency ,intensity,rigidity were superior to the others.Significent different have been found(P<0.05). and Group F(P>0.05);Group A was the weakest method.â‘£There were no significant difference in Group C and Group F.From the view of biomechanics and safety, the method of Group F was the best in six methods.ConcluSIons:â‘ The posterior sacroiliac ligaments complex contribute most to the sacroiliac joint stability.â‘¡The fixation method of Group F was the best in the six methods.