ObjectiveTo establish an assessment method for safe acetabular screw placement based on three-dimensional CT reconstruction and the acetabular “clock-face” coordinate system; to quantify the vascular safety length and effective intraosseous length at each screw hole position of the acetabular prosthesis; and to provide a reference basis for individualized acetabular screw placement in total hip arthroplasty (THA). Methods The CT angiographic data of both lower extremities of 64 patients hospitalized for non-orthopedic diseases between January 2022 and December 2024 who met the selection criteria was retrospectively analyzed. There were 32 males and 32 females. Three-dimensional reconstruction was performed using Mimics21.0 software. With the anterior pelvic plane as the reference plane, the acetabular opening was conceptualized as a “clock face”. The intersection of the anterior superior iliac spine-to-acetabular center line (or its projection) with the inferior acetabular rim was defined as the “6 o’clock” reference point. Based on this reference point, the central hole of the prosthesis was aligned toward the 12 o’clock direction to simulate acetabular cup implantation, achieving positional correspondence between the prosthesis screw holes and the clock-face coordinates, with the anterior hole aligned to 1 o’clock and the posterior hole aligned to 11 o’clock. Acetabular prosthesis implantation was simulated at fixed angles (abduction angle 40°, anteversion angle 20°). Cylindrical models matching the diameter of actual screws were used to simulate screw insertion, with axial extension perpendicular to each screw hole. The safe length of the blood vessel or effective intraosseous length at each hole site and the coverage of three commonly used screw lengths (20, 25, 30 mm) at each hole site were measured. Pearson correlation was used to analyze the correlation of each measurement with age and body mass index. Results The safe length from the anterior hole to the external iliac artery and the effective intraosseous length of the middle hole were significantly longer in males than in females (P<0.05). There was no significant difference in the safe length from the posterior hole to the superior gluteal artery between males and females (P>0.05). Pearson correlation analysis showed that only the effective length of the middle hole was negatively correlated with age (P<0.05), while the safe length of the anterior hole to the external iliac artery and the safe length of the posterior hole to the superior gluteal artery were not correlated with age and body mass index (P>0.05). In terms of screw selection, the coverage rate of 20 mm screws in the anterior, middle, and posterior holes of acetabular prosthesis was 100.00% in both males and females, and the safety was good. The coverage rate of 25 mm screws in anterior and posterior holes was 100.00% in both males and females, and the safe length was sufficient; the coverage rate of middle hole was 96.86% in males and 71.86% in females. When the length of screw was further increased to 30 mm, the coverage rate of anterior hole was still 100.00% in males and 68.97% in females, the coverage rate of middle hole was 71.86% in males and 34.36% in females, and the coverage rate of posterior hole was still at a high level, 92.86% in males and 100.00% in females. The decrease in coverage was more pronounced in males when longer screws were used in the anterior and middle hole areas. ConclusionSignificant sex-related differences exist in the safety parameters of acetabular screws in THA. In females, the anterior screw hole is associated with a higher vascular risk, and the effective intraosseous length at the middle hole is shorter; therefore, a middle-hole plus posterior-hole combination is recommended. In males, an anterior-hole plus posterior-hole combination may be considered the preferred reference strategy. In the absence of navigation assistance, a conservative screw placement strategy is recommended to reduce vascular complications and improve the initial stability of the prosthesis.