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2022, Vol. 26 ›› Issue (3): 350-353Coverage of the acetabular cup under different perspective angles: assessing the position of the total hip arthroplasty prosthesis for complex types of hip dysplasiaWang Jinzi, Ding Hai, Zhang Heng, Chang Wenju, Liu Fendou
Abstract: BACKGROUND: The coverage of acetabular cup is used to evaluate the inclusiveness and stability of the acetabular cup after total hip arthroplasty. Plain radiograph examination of the hip is a common method to detect acetabular cup coverage during or after total hip arthroplasty. Different perspective angles may affect the measurement and evaluation of acetabular cup coverage. OBJECTIVE: To explore the relationship between the coverage of the acetabular cup under different perspectives after total hip arthroplasty. METHODS: Five three-dimensional printed synthetic pelvic specimens were taken, and 52 mm diameter acetabular cup prosthesis was placed by polishing the right acetabulum to prepare different acetabular cup coverage models. The prepared pelvis model was fixed with the right acetabulum as the center under the C-arm machine for fluoroscopy. By rotating the C-arm machine, the right hip joint was seen through the front view, 15°, 30°, and 45° axial position films and left 15°, 30°, and 45° oblique films. The coverage of the acetabular cup under different perspective angles was calculated by Photoshop2019 software to compare the difference between the acetabular cup coverage under the different angles of the axial and oblique films and the orthographic film. RESULTS AND CONCLUSION: (1) In the test of the acetabular cup coverage of the axial film, as the axial perspective angle was tilted upward; the coverage of the acetabular cup gradually increased, and was significantly higher in the upper 45° axial film group than that in the hip orthographic film group [increased (6.72±1.57)%, P=0.009]. (2) In the oblique film acetabular cup coverage test, as the perspective angle tilted to the left, the coverage rate showed a downward trend. The coverage was significantly lower in the left 45° oblique film group than that in the hip joint orthographic film group [decreased (5.56±1.91)%, P=0.021]. (3) Results confirm that there are differences in the coverage of the acetabular cup under different oblique perspective angles. The greater the upward axial tilt angle, the greater the cup coverage, and the greater the contralateral tilt angle, the less cup coverage. It is indicated that for patients undergoing total hip arthroplasty, attention should be paid to the intraoperative fluoroscopy angle. For complicated types of total hip arthroplasty patients, 45° oblique films can be shown during or after the operation to further evaluate the position and coverage of the cup. Key words:arthroplasty, hip, replacement, coverage, pelvis, acetabular cup, fluoroscopy, axial |