Biomechanical And Radiograph Study Of Acetabular Anteversion And Acetabular Retroversion

Background:There has a great concealment of the FAI caused by acetabular anteversion and acetabular retroversion. The present study shows that a large number of young patients with hip pain,it is difficult for us to make early correct diagnosis simply by detailed history and physical examination, and the traditional X-ray examination is essential. The acetabular and femoral head loss of the normal anatomical relationship,and biomechanical environment changed, osteoarthritis will appear by long-term abnormal stress at last. So early diagnosis and early treatment is especially important.The first part: Radiograph study of acetabular anteversion and acetabular retroversionObjective: To early diagnosis the acetabular anteversion and acetabular retroversion by its feature radiograph and detailed history and physical examination.Documents and Methods: Take four anti-corrosion specimens of adult pelvic, cut off the body since the L3 level and the 1 / 3 at the junction of legs.get four pelvic specimens(including bilateral femoral shaft upper), strip the muscles and periosteum which attached to the pelvic, cut off the round ligament,and get 8 normal acetabular. First measured bone mineral density of these specimens,then numbered the 8 normal acetabular: 1L,1R,2L,2R,3L,3R,4L,4R.The normal anterior and posterior walls of the acetabulum were identified. A deficient posterior wall was simulated by fixing a wire in the acetabulum to where the posterior wall of the acetabulum would be if there were a posterior acetabular wall deficiency measuring 1 cm at its apex. An augmented anterior wall was created on the model pelvis with clay such that at its apex, the augmentation measured 1 cm. A wire was placed on the rim of this augmented anterior wall so it was visible on a radiograph.. The normal morphologic features of the anterior and posterior wall also were radiographically defined by placing wires along the normal anterior and posterior rims of the acetabulum. L for the retroversion group, R for the anteversion group.Results: Schematic drawing of an anteroposterior radiograph of the hip,showing an anteverted acetabulum.The superior aspect of the posterior wall is lateral to the center of the head, and there is no cross-over sign,and there is a"人"sign. A retroverted acetabulum .the superior aspect of the posterior wall is medital to the anterior wall ,the posterior wall is medital to the center of the femoral head, a cross-over sign is present,and the ischial spine is prominent, The line of the edge of the posterior wall is located at or even lateral to the centre of the femoral head,a"posterior wall"sign is present, Kalberer et al found that the sensitivity was 91% of the the diagnosis of acetabular retroversion if the ischial spine projected in the pelvic cavity on an anteroposterior radiograph,and there was a high degree of correlation with the cross-over sign. Peelle et al found that 49% of the FAI patients had at least one of the above-mentioned image changes by the retrospective analysis.Conclusion: On standard anteroposterior pelvis,if there is a"人"sign and typical detailed history and typical physical examination,we can early diagnosis the acetabular anteversion,if the superior aspect of the posterior wall is medital to the anterior wall ,the posterior wall is medital to the center of the femoral head, a cross-over sign is present, we can early diagnosis the acetabular retroversion.It will improved the diagnosis of the acetabular anteversion and the acetabular retroversion and the FAI.The second part: Biomechanical Study of the acetabular anteversion and the acetabularObjective: respectively measuring stress and strain distribution of acetabular under simulated physiological conditions and when there was acetabular anteversion or acetabular retroversion on the position of the stand with one foot.Preliminary study the biomechanical changes brought about by acetabular anteversion and the acetabularMaterials and Methods: Take four anti-corrosion specimens of adult pelvic, cut off the body since the L3 level and the 1 / 3 at the junction of legs.get four pelvic specimens(including bilateral femoral shaft upper), strip the muscles and periosteum which attached to the pelvic, cut off the round ligament,and get 8 normal acetabular. First measured bone mineral density of these specimens,then numbered the 8 normal acetabular: 1L,1R,2L,2R,3L,3R,4L,4R.There are three kinds of common pelvic location in acetabular biomechanics experiments, we use the neutral position of the stand with one foot proposed by Olson et al in 1995, the load side of the hip bear the 5/6 weight, respectively measuring stress and strain distribution of acetabular under simulated physiological conditions and when there was acetabular anteversion or acetabular retroversion on the position of the stand with one foot.There existed center of gravity offset and pelvic tilt under the position of the stand with one foot,so it needed abductor play the role of antagonism. In this study,we used an wire whose length could be adjusted instead of the abductor and playing the role of antagonism. We use rectangular rosette in this study,it had been proved that the stress on the weak areas within the board of the hip was higher according to the experiments of the stress distribution in the pelvic model done by Lu Zhiyuan, etc.,this areas was 3-4cm far from the acetabular rim, therefore, the strain gauges of the experiment were mainly distributed in the areas, 30°around the acetabular roof was the main force area described by Thomas, We drew a vertical line pass through the tangent of the acetabular roof, positioned 0°,and drew a line respectively forward15°andbackward 15°,positioned a rectangular rosette respectively on these three lines where were 3.5cm away from the acetabular rim. It is marked as C, B, A sheet from outside to inside of the anterior edge of acetabulum,it is marked as D, E, F sheet from outside to inside of the posterior edge of acetabulum. First placing and pasting the strain gauge, measuring the data of the normal acetabulum,then along the wires which used to simulat the deficient posterior wall and anterior wall to remove the acetabulum, Calculated weight according to the steps 2.2.2,and made sure the load force was 500N according to the load side of the hip bear the 5/6 weight when was the neutral position of the stand with one foot. Done the calibration of the resistance strain gauge and base zero in advance.After placing the specimen on the loading platform of the mechanical testing machine,loaded it under 500N, then unload, load force zero.The speed of load was 2mm/min.And then loading on four class force such as 200,300,400,500N. Through the data recorded by the computer,we can calculate all the loads are carried out within the elastic deformation. Recorded the data of the strain gauge, loaded 2 times on each experimental condition and get the averaged. Each rosette strain, through which would get three groups datas, we calculated the size and direction of major strain of the point according to the formula and procedures.Each loading we would pick up a wire to connect to another strain gauge which was not loaded from the strain gauge which was loaded for the temperature compensation.Results: There was a significant statistical difference of the strain of the points of the retroversion group compared with normal condition group( S=107,P=0.0009). Datas show that there was a significant change of the force of the acetabulum rim when the acetabulum retroversion had been occurred. There was a significant statistical difference of the strain of the points of the anteversion group compared with normal condition group(S=123,P=0.001). Datas show that there was a significant change of the force of the acetabulum rim when the acetabulum anteversion had been occurred.Conclusion: Through this study, we concluded that the per unit area stress of the acetabular margin increased significantly when there is an acetabular anteversion or acetabular retroversion.After we diagnosed the acetabular anteversion and the acetabular retroversion,we should make an appropriate treatment according to its biomechanical feature.