Assessing the positioning of prostheses after surgery is essential for evaluating therapeutic efficacy and optimizing surgical methods in 3D-printed patient-specific acetabular revision implants. However, the lack of a dedicated three-dimensional accuracy assessment framework for these customized implants has impeded the development of standardized benchmarks for verifying spatial alignment between intraoperative placement and preoperative digital planning. To bridge this gap, we introduce a novel evaluation system that integrates point localization, vector-based angular assessment, and volumetric overlap analysis to comprehensively quantify alignment between implanted prostheses and preoperative templates. Patients were classified into cohorts according to postoperative Harris Hip Scores and complication profiles, differentiating a "better outcome" group (Harris≥80, no major complications) from a "regular outcome" group. A CT-based pelvic 3D coordinate system, established through anatomical landmarks, facilitated comparative analyses of intergroup variations in positional deviation, angular deviation, and volumetric overlap accuracy. The system’s reliability was confirmed via inter- and intra-observer consistency tests. Findings revealed outstanding measurement consistency (κ>0.8). Compared to the regular outcome group, patients with better outcomes demonstrated significantly lower positional deviations (p<0.001) and angular deviations (p=0.003), along with superior volumetric overlap accuracy (p<0.001). This CT-guided stereotactic assessment system offers a clinically relevant, high-fidelity approach for evaluating postoperative implant placement in 3D-printed acetabular prostheses. Notably, it represents the first validated methodology leveraging a pelvic 3D coordinate framework for a comprehensive analysis of preoperative planning versus postoperative implant positioning.