Biomechanical comparison of the stability of posterior pelvic ring disruptions fixed with three kinds of internal fixator

Abstract

Objective To compare the stability of vertical fractures of posterior pelvic ring fixed with tension band plate (TBP),two sacroiliac(SI) screws and minimally invasive adjustable plate (MIAP) for posterior pelvic ring.Methods Eight adult male pelvic specimens without osteoporosis were selected.The sacroiliac complex was retained and other soft tissue was removed.The right sacral vertical fractures were made.The fractures were reduced anatomically and fixed in turn with TBP,two SI screws and MIAP.The pelvic specimens were fastened to the biomechanical testing machine in sitting position.Vertical load,ranging from 0 to 620 N,was applied on specimens at a speed of 20 N/s and the displacement was recorded.Then the specimens were exposed to torsional load at a speed of 0.1 degree/s.The rotation degree and corresponding torque were recorded.Analysis of variance was employed to analyze the data.Results Under vertical load,the displacement of the pelvis fixed with MIAP was similar to that fixed with two SI screws.The displacement of the pelvic fractures fixed with either MIAP or two SI screws was smaller than that fixed with TBP.Under torsional load,the torque measured on the pelvis fixed with MIAP was similar to that fixed with two SI screws.The torque measured on the pelvic fractures fixed with either MIAP or two SI screws was greater than that fixed with TBP.Conclusion The posterior pelvic ring disruptions fixed with MIAP is as stable as that fixed with two SI screws,both with better stability than that fixed with TBP,under both vertical load and torsional. Key words: Pelvis; Fractures, bone; Biomechanics; Internal fixators