Abstract: BACKGROUND: Clinical treatment of the increased anteversion angle of the femoral neck in developmental dysplasia of the hip is often achieved by rotating osteotomy at the upper end of the femur, and how to accurately control the rotation angle and displacement during the operation is the key to the success of the operation.
OBJECTIVE: To compare the value of two femoral osteotomy rotation angle measurement methods in the correction of the anteversion angle of the femoral neck by three-dimensional reconstruction simulation before operation and intraoperative line drawing.
METHODS: Normal adult femur specimens were taken for external rotation osteotomy. In the line drawing group, formulas were used to calculate the anterior inclination angle of the upper end of the femur by 2, 4, 6, and 8 mm (total 8 groups). The rotation osteotomy operation was completed. CT scan was used to measure the actual postoperative anteversion angle. In the preoperative simulation group, three-dimensional reconstruction of the intact femoral specimen was performed, and the calculated anteversion angle was performed by Solidworks to simulate the femoral osteotomy rotation to a specific angle before surgery. The surface displacement (arc length) of the femoral osteotomy end was measured, and then a rotary osteotomy was performed on the femoral specimen according to the arc length. The actual anteversion angle obtained after the CT scan was measured. The actual postoperative femoral neck anteversion angle and the calculated femoral neck anteversion angle were compared and analyzed in both groups.
RESULTS AND CONCLUSION: (1) The actual measured anteversion angle after the line drawing group was (8.4±26.2)°, and the calculated preoperative anteversion angle was (10.3±26.5)°; there was a significant difference between the two (P < 0.05). (2) The actual measured anteversion angle in the preoperative simulation group was (10.4±26.6)°, which was not significantly different from the calculated preoperative anteversion angle (10.3±26.5)° (P > 0.05). (3) The results showed that three-dimensional reconstruction pre-simulation and intraoperative line-drawing method to guide femoral rotation osteotomy can effectively correct the excessive femoral anteversion angle. The preoperative simulation of three-dimensional reconstruction has smaller errors than the intraoperative line-drawing method. The preoperative simulation of three-dimensional reconstruction can make the femoral rotation osteotomy more precise, personalized and intelligent.   

Key words: bone, line drawing method, developmental hip dysplasia, femoral osteotomy, anteversion, dislocation, three-dimensional CT, preoperative simulation