| 1 Biomechanical Study of Transverse Acetabular Fracture Fixation Methods Objective: Acetabular fractures are common,representing 3% of all fractures. The majority of authors agree that the clinical results of patients treated surgically are superior to those in patients treated nonoperatively. More and more internal fixation methods had been proposed. The purpose of this study was to evaluate the stability of six kinds of internal fixation methods requiring anterior or posterior surgical approach for the transverse acetabular fracture.Methods: Thirty embalmed pelves plus the proximal femora were harvested for this study. Each of these thirty pelves was sectioned sagittally through the midline of the sacrum and the symphysis. This produced sixty hemipelves for testing. All of these specimens were visually examined and then X-rayed to exclude the presence of hip pathology. All muscles and connective tissues, including the hip capsule were dissected. An osteotomy which was perpendicular to the femoral neck was made. The femoral head was preserved.The fracture was made by a saw, with a blade thickness of 0.6mm.The osteotomy was directed from the center of the sulcus for the iliopsoas muscle on the anterior acetabular wall, just posterolateral to the iliopectineal eminence toward the junction of the inferior part of the acetabular roof and the cotyloid fossa, toward the midpoint of the greater sciatic notch and the sciatic spina. The fracture plane was parallel to the transverse plane.The osteotomy provided no interdigitation or inherent stability to the fracture site. The sixty hemipelves were divided into six groups randomly. Each group was repaired with one of the six fixation methods. Internal fixation methods consisted of (A) a single anterior column plate, (B) a single posterior column plate, (C) double posteriorcolumn plates, (D) anterior column plate and posterior column plate; (E) anterior column lag screw and posterior column plate, (F) anterior column lag screw and posterior column lag screw.All of the plates, screws and lag screws were the same in material and shape. Attention The midpoint of the plate was on the fracture line. The plates were contoured carefully to fit the surface of the anterior or posterior column. All of the screws must not penetrate the hip joint or interfere with the fracture line.The position of the plates and screws was confirmed by X-ray photography. This biomechanical study was finished by a biomechanical test machine (Model:css-44020,Changchun,China).Each repaired hemipelvis was put on the jig. The acetabular was on the top. The force was applied through the femoral head which was connected to a transition bar. The jig consisted of two metal slopes. There was a 12.5 degree angle between each of the two slopes and the horizontal plane. There was a 155.0 degree angle between these two metal slopes. Then this transition bar was attached to the load cell. This metal bar was perpendicular to the horizontal plane. When the load was applied, the sacrum section and the symphysis section would slide along the metal slopes in an opposite direction. The femoral head was driven into the acetabulum at the speed of 5.00mm/min.The loads were increased in a continuous manner until the internal fixation failed. The internal fixation failure was defined as the gap displacement of the articular surface was more than 3.00mm.This articular surface gap displacement was measured by a plug gauge. The maximal loads were recorded. Differences tested at the P<0.05 level using a repeated measures analysis of variance and Scheffe-test with the help of statistical software-Stata 4.0.Results: (1)All of the plates were not damaged. All of the screws were not pulled out. The lag screws were not bent. The transition bar was connected to the femoral head tightly. All of the hemipelves did not have fractures. With single column internal fixation, the maximal displacement occurred at the opposite column.(2)To the transverse acetabular fracture, the maximal load for the anterior column plate(Group...
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