To investigate whether the accuracy of artificial intelligence (AI)-assisted preoperative planning for total knee arthroplasty (TKA) is non-inferior to computer-assisted manual preoperative planning completed collaboratively by 3D engineers and orthopedic surgeons, and to evaluate the impact of age on the accuracy of AI-based planning.

This study adopted a retrospective, cross-sectional comparative design. Data were retrospectively collected from 127 patients who underwent TKA at the First Affiliated Hospital of Army Medical University between December 2022 and September 2023. They were divided into a ≤60 years group (40 to 60 years old, n=22) and an >60 years group (61 to 80 years old, n=105) based on age. All patients underwent both AI-assisted preoperative planning (AI planning) and computer-assisted manual preoperative planning (conventional planning). Hip-knee-shaft angle (HKS), femoral resection difference, tibial resection difference, femoral rotation angle, and prosthesis size data from AI planning, conventional planning, and actual intraoperative measurements, as well as time, manpower, and economic costs of AI planning and conventional planning were compared between the 2 planning methods. The non-inferiority margin was set as resection angle difference ≤1°, resection thickness difference ≤1 mm, and prosthesis size difference ≤1.

Compared with the conventional planning, the AI planning showed a mean increase of 0.8°±1.2° in HKS (Cohen’s d=0.4, 95%CI: 0.2 to 0.7), a mean increase of 1.1±1.8 mm in femoral resection difference (Cohen’s d=0.5, 95%CI: 0.3 to 0.8), and a mean increase of 0.6±1.7 mm in tibial resection difference (Cohen’s d=0.3, 95%CI: 0.0 to 0.5). The lower limits of 95%CI for these above standardized mean differences were all greater than their corresponding negative non-inferiority margins. In comparison with the conventional planning, the AI planning in the ≤60 years group showed no significant differences in HKS, tibial resection difference, and femoral rotation angle (P>0.05), whereas in the >60 years group, only femoral resection difference of AI planning exceeded the non-inferiority margin (with a mean increase of 1.1 mm, P<0.05). For prosthesis size prediction, the AI planning achieved 73.2% femoral prosthesis and 87.4% tibial prosthesis predictions with size differences not exceeding 1, while conventional planning achieved 81.9% femoral prosthesis and 90.6% tibial prosthesis predictions with size differences not exceeding 1, with no significant difference between the 2 planning methods (P>0.05). The time consumed for AI planning was significantly shorter than that for conventional planning (27.4±4.1 vs 45.3±8.5 min, P<0.05). Moreover, AI planning required no additional labor and equipment costs, with no additional manpower or equipment costs (0 vs 3 000 Yuan/case).

AI-assisted preoperative planning for TKA s demonstrates non-inferior accuracy compared with conventional planning, with superior performance particularly in patients under 60 years, and significant advantages in time and economic costs.