INVESTIGATION OF FEMORAL ANTEVERSION, ACETABULAR ORIENTATION AND COMBINED ANTEVERSION WITH THREE-DIMENSIONAL ANATOMICAL MODELLING

Purpose: The aim of our thesis study is; to compare the measurement results of femoral anteversion, acetabular anteversion, acetabular inclination, combined anteversion on standard 2D CT sections and 3D CT modeling; To determine anatomical 3D femoral anteversion, acetabular anteversion, acetabular inclination and combined anteversion values in the individuals in our study group; To investigate whether there are differences in measured parameters between genders and to compare two different methods used in femoral anteversion measurement (posterior condylar axis-transepicondylar axis) with measurements made through 3D CT modeling. Materials and Methods: Our study included 100 adults (50 men and 50 women) between the ages of 18-60, from computed tomography images of the pelvis and the entire lower extremity in our hospital radiology database. Those with fractures involving the pelvis, femur or hip and who had previous hip surgeries, a history of lower extremity corrective osteotomy and with pathologies that may disrupt lower extremity alignment such as tumor or infection and with hip or knee prosthesis applied to the examined side, patients under 18 years of age and over 60 years of age and with knee or hip osteoarthritis in their existing images were excluded from the study. In the entire sample, only the right femur and right acetabulum were examined. Pelvis and lower extremity tomography images in DICOM format of the adults in the study were transferred to the Materialize MIMICS Research (Materialise, Leuven, Belgium) program. With the help of the Materialize MIMICS program, 3D models of the pelvis and right femur of all adults were segmented in the range of 200 – 2150 Hounsfield units. 2D and 3D angle measurements were performed in the Materalise 3-Matic Research program (Materialise, Leuven, Belgium). The data obtained in our study were evaluated with the IBM SPSS Statistics 25 (IBM, New York, United States) program. Results: In our study group, the mean acetabular anteversion was 20.61° ± 6.06° in 2- dimensional measurements and 27.40° ± 7.39° in 3-dimensional measurements; mean acetabular inclination was 38.59° ± 4.07° in 2-dimensional measurements, 51.41° ± 5.65° in 3- dimensional measurements; femoral anteversion 10.71° ± 7.75° in 2-dimensional measurements, 15.38° ± 8.29° in 3D measurements; combined anteversion 31.33° ± 10.86° in 2D measurements, 42.78° ± 12.48° in 3D measurements; Femoral anteversion relative to the transepicondylar axis was 9.11° ± 8.32° in 3D measurements. Acetabular anteversion, femoral anteversion and combined anteversion were higher in women than in men. Acetabular inclination was higher in men than women in 3-dimensional measurements, but there was no gender difference in 2-dimensional measurements. A low level of correlation was found between the 2D measurement results and the 3D measurement results of the acetabular anteversion and acetabular inclination angles (r = 0.426 and r = 0.410, respectively). The correlation between 2D and 3D measurements of combined anteversion was moderate (r = 0.678). In femoral anteversion, a high level of correlation was detected between 2-dimensional and 3-dimensional measurements (r = 0.840). The correlation between the two methods of measuring femoral anteversion using the posterior epicondylar axis and the transepicondylar axis as reference was also high (r = 0.946). Conclusion: We think that measurements made using classical 2D CT slices for acetabular anteversion, acetabular inclination and combined anteversion measurements do not fully reflect the natural hip anatomy, so we recommend making measurements using 3D anatomical models. Although we found a high correlation between 2-dimensional and 3- dimensional measurement methods in femoral anteversion measurement, consistent with the literature, we do not know whether the 4.66° ± 4.57° difference between the two methods will affect the clinical results and we think that this issue should be evaluated in new clinical studies. Therefore, we think that the 3-dimensional method would be more appropriate for femoral anteversion measurement. Keywords: Femoral anteversion, Asetabular anteversion, Aseetabular inclination, Combined anteversion, , Computer generated three-dimensional imaging