Coverage Of The Acetabular Cup Under Different Perspective Angles:Assessing The Position Of The Total Hip Arthroplasty Prosthesis For Complex Types Of Hip Dysplasia

[Background]Development dysplasia of the hip（DDH）is a common orthopedic disease in clinic.In terms of surgical treatment of DDH.Total hip arthroplasty（THA）is the most common adult hip joint treatment operation,which improves hip joint function and has achieved satisfactory results in the medium and long term.However,complications such as prosthesis loosening caused by various reasons after surgery are also increasing year by year.Especially for patients with various complex types of hip dysplasia,the lack of sufficient bone coverage will make it difficult for the components of the acetabular cup to obtain high initial stability,thereby affecting osseointegration.The coverage of the acetabular cup is used to evaluate the inclusiveness and stability of the acetabular cup after total hip replacement.Insufficient cup coverage has always been considered a negative factor leading to cup loosening.Because it is difficult to measure the three-dimensional coverage during the operation,the hip joint plain radiograph has become a common method for evaluating the coverage of the acetabular cup during or after total hip arthroplasty.Among them,different perspective angles may affect the measurement and evaluation of the acetabular cup coverage,especially for patients with complex types of total hip replacement or acetabular bone defects,which may bias the clinical evaluation of the acetabular cup coverage,thereby affecting The service life of the prosthesis and the recovery of patient function.[Objective]To explore the relationship between the coverage of the acetabular cup under different perspectives after total hip arthroplasty.[Methods]Take 12 artificial pelvis specimens that are synthesized by 3D printing,and the acetabular cup prosthesis was placed by grinding the right acetabulum to prepare12 different acetabular models after total hip arthroplasty.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]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 4.90±1.09)%,P=0.001].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（4.26±0.90）%,P=0.001].[Conclusion]Results confirm that there are differences in the coverage of the acetabular cup under different oblique perspective angles.The greater the head 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.