ABSTRACT
BACKGROUND:Improper angle of prosthesis placement often induces acetabular cup impact, and limits the scope of activity of artificial hip joint, and cannot meet the requirement of daily life. At present, the angle of acetabular cup instal ation remains controversial during total hip arthroplasty. Moreover, there is lack of targeted guide for the acetabular cup instal ation during hip arthroplasty with different head-neck ratios. OBJECTIVE:To explore the safe range of the artificial acetabular cup instal ation angle for different head-neck ratios. METHODS:In accordance with the calculation formula of range of internal rotation and external rotation, abduction and adduction, flexion and extension after total hip replacement, interpretation of dynamical variety law of acetabular abduction and anteversion, and deriving inequalities depending on Widmer’s standard of artificial hip joint normal activities range:(1) external rotation range was at least 40°, and internal rotation range was at least 80°. (2) Abduction range was at least 50°, and adduction range was at least 50°. (3) Anteflexion range was at least 130°, and extension range was at least 40°. The safety scope of artificial hip joint instal ation angle at different head-neck ratios was determined by solving the above three groups of inequality. RESULTS AND CONCLUSION:The safe range of the artificial acetabular cup instal ation angle for different head-neck ratios was different. To meet the normal hip joint activities, the head-neck ratios of artificial hip should be greater than 22/12. Artificial hip joint activities gradual y increase with the enlargement of head neck ratios. With enlarging the head-neck ratios, the acetabular cup instal ation safety angle scope of abduction and anteversin gradual y increases and the extreme of abduction increases gradual y, then with anteversion increasing gradual y, the abduction upper extreme of the security scope gradual y decrease and lower extreme of the security scope gradual y increase, tending to 45° symmetrical y. When anteversion is the biggest, the abduction should be 45°.