This study aimed to compare surgical antibiotic prophylaxis (SAP) practices among patients undergoing total joint arthroplasty (TJA) under two different mo

Objectives To evaluate the impact of the DRG payment reform on the hospitalization expenses, service efficiency, and expense structure of patients undergoing orthopedic internal fixation surgery. Methods A retrospective interrupted time-series analysis was conducted by including 720 patients who underwent orthopedic internal fixation surgery at a tertiary first-class hospital in Jiangsu Province (360 cases before the reform and 360 cases after the reform). Data from 2019 (before the reform) and 2022 (after the reform) were analyzed, using segmented regression models, new grey relational analysis, and structural variation analysis. The primary outcome indicators included total hospitalization expenses, the length of hospital stay, and changes in expense structure. Results After the DRG payment reform, medical efficiency improved significantly, with the average length of hospital stay declining from 12.44 days to 10.68 days (-14.15%, P = 0.010). However, there was no significant change in the average total hospitalization expense (decreasing from 27,071.09 yuan to 26,286.35 yuan, i.e., 2.90%, P = 0.688), while the medical insurance reimbursement expense increased slightly by almost 2.95%, indicating a significant reshaping of the structure of inpatient expenses. The most prominent change was a 61.88% increase in examination and test fees (P < 0.001). Medical service, drug, and consumable fees all showed a downward trend (decreasing by 10.88%, 13.21%, and 9.30%, respectively). However, none of these reached statistical significance (all P-values > 0.05). When stratified by age, the average cost per case decreased significantly in the 50‒59 and ≥ 60 years age groups, with 23.25% (P = 0.018) and 19.52% (P = 0.015), respectively. In terms of surgical complexity, the cost and length of hospital stay for grade IV complex surgeries showed the greatest improvement: cost decreased by 36.11% (P < 0.001) and length of hospital stay decreased by 27.24% (P = 0.003). Conclusion The DRG payment reform successfully improved medical efficiency and shifted the expense structure from a consumable- and drug-dependent to a diagnosis-driven model. The differential impacts of the reform on different age groups and surgical complexity levels suggest that the risk adjustment mechanism must be further refined.