To Evaluate The Clinic Significance Of Dynamic Measurement Of Acetabular Anteversion And Abduction Angle Under Non-physiological Statement

Objective: To provide guidance for placing the acetabular prosthesis at right angles during total hip arthroplasty(THA). The acetabular abduction angle and acetabular anteversion were obtained by using the three-dimensional reconstruction of multi-slice spiral CT.The mean and standard deviation of acetabular abduction angle and acetabular anteversion were calculated to draw out the curve with different pelvic inclination.Methods: 50 patients(25 men and 25 women) which contained 100 pelvis were scanned by MSCT. To determine anteversion and abduction angle,vary degrees of pelvic anteversion, and reconstruct the horizontal position and coronal level in simulated pathological conditions. Choosing anterior plane of pelvis as a reference plane while measure anteversion angle. To measure the upper level, middle, and lower level between the leading and trailing edge of the acetabular point levels. The middle level was the maximum level while the upper and lower level were next to the middle level. The thickness was 5mm.According to the definition of anteversion angle, take the complementary angle of angle from the leading and trailing edge of the acetabular point levels as anteversion angle. Then measure and calculate the anteversion angle on three levels. When measuring abduction angle by MSCT, the coronal plane of pelvis was chosen as a reference plane to reduce errors and ensure the accuracy of the measurement. Thus the section which paralleled to anterior pelvic plane was investigated. According to the definition of abduction angle,calculete the angle formed by connecting the acetabular rim connection and bilateral inferior margin of acetabulum. The average abduction angle of notch front and trail point level of acetabular were obtained through calculation.According to the definition of abduction angle, calculete the angle formed byconnecting the acetabular rim connection and bilateral inferior margin of acetabulum. The average abduction angle of notch front and trail point level of acetabular were obtained through calculation. The degree of pelvic was changed to simulate pathological conditions, and measured the abduction and anteversion angle when the inclination of the pelvis was varied from 10 ° to90 ° with 10° as its interval. After analysing the results of mean and standard deviation by statistical software, the variaties of acetabular anteversion and abduction angle with pelvic inclination were profiled and investigated. All data could provide theoretical basis for THA when implanting acetabular prosthesis.Results:The mean and standard deviation of abduction and anteversion angle were calculated. There exist significant difference when P < 0.05.Drawn relevant curves of change about abduction and anteversion angle under different pelvic inclination which was treated as its abscissa. The results of acetabular anteversion angle were as followed: When the pelvis inclination gradually increased from 10 ° to 90 °, the anteversion decreased correspondingly. And the the regression was y =-0.4582 x + 40.714,( r =0.994), which showed a good linearity. When the pelvic inclination is 83 °, the anteversion angle is zero. The results of acetabular abduction angle were as followed: When the pelvis inclination was varied from 10 ° to 90 °, abduction angle change showed a parabola curve. When the pelvis inclination was between 60 °- 70 °, the abduction angle achieved maximum level of is 42 °-48 °. It illustrated that not only the coverage of acetabular to femoral head was best, but also the joint was most stable under this condition. In addition, the study also analyzed the impact of gender on the acetabular anteversion and abduction angle, the results showed there was no significant differences between different sexes(P> 0.05) under the same conditions.Conclusions: 1.Both the acetabular anteversion and abduction angle were changed according to the variety of pelvic inclination. And the anteversion angle showed a linear correlation with pelvic inclination.abduction angle change showed a parabola curve.The change in the acetabularabduction angles is very obvious when the pelvic rotates along the sagittal axial.Therefore, the results in this research about acetabular anteversion and abduction angle changed with dynamic pelvis inclination could provide useful reference for THA.2.By comparing the acetabular anteversion and abduction angle between men and women, it founded that there was no significant difference.This showed that the influence of gender factors can be not obvious when the heacetabular anteversion and abduction angle were changed approach.