Biomechanical Comparison Of The Stability Of Dislocations Of Sacroiliac Joint Fixed With Four Kinds Of Internal Fixator

Objective: To compare the stability of dislocation of sacroiliac joint fixed with single sacroiliac screw, posterior tension band plate(TBP), anterior tension band plate(TBP) and π-shaped rod(πF).Methods: Five adult cadaveric pelvis specimens were selected. The sacroiliac complex was retained and other tissue was removed. The right dislocations of sacroiliac joint- pubic symphysis separations were made. Four models were selected randomly to undergo the biomechanical test in different internal fixation orders. The dislocations of sacroiliac joint were treated respectively and randomly with the single sacroiliac screw, the posterior tension band plate(TBP), the anterior tension band plate(TBP) and the π-shaped rod(πF). The symphysis separations were reconstructed with band plate. The vertical load, ranging from 0 to 650 N, was applied on specimens at a speed of 20 N/s. The displacement was recorded. The specimens were exposed to torsional load at a speed of 0.2 degree/s from 0 to 6°.The rotation degree and the corresponding torque were recorded. The above tests were repeated three times. Then, the fixed methods were changed in proper order. Analysis of variance was employed to analyze data.Results:The vertical stress induced elastic deformations with all four Internal fixators. The stability was inversely proportional to pressure. In closed circuit, the fixation with the posterior tension band plate was good at level stability. And the fixation with the π-shaped rod(πF) was good at vertical stability. In open circuit, the conclusion of posterior ring was same as the above results. To anterior ring, the fixation with the single sacroiliac screw was best at level stability. The anterior tension band plate(TBP) was best at the vertical stability. To resistant of rotation, the treatment with the posterior tension band plate was better than three other ways in closed ring. And the treatment with the π-shaped rod(πF) was better than three others in open circuit.Conclusion:Whether the anterior ring is fixed or not, the fixation withπ-shaped rod(πF) is better at stability of pelvic. And the fixation with the anterior tension band plate(TBP) may be better for minimally invasive surgery.