Accuracy analysis of artificial intelligence-assisted three-dimensional preoperative planning in total hip replacement

Abstract

Objectives: This study aims to assess the outcome of total hip arthroplasty (THA) using artificial intelligence (AI)-assisted three-dimensional (3D) preoperative planning technology in terms of predicting prosthesis size, acetabular cup positioning, and lowerlimb length restoration.

Patients and methods: Between January 2020 and July 2022, a total of 161 patients (101 males, 60 females; mean age: 57.6±10.5 years; range, 31 to 80 years) who underwent primary unilateral THA were retrospectively analyzed. The patients were divided into two groups as those who were treated with AI-assisted 3D preoperative planning technology (the observation group, n=95) and patients who were treated with traditional two-dimensional (2D) X-ray template planning technology (the control group, n=66).

Results: The accuracy of the planning was based on the consistency of the preoperative planning and intraoperative models. The difference between the observation group and the control group was statistically significant in terms of the accuracy of the preoperative planning of acetabular prostheses (54% vs. 38%, p=0.048) and femoral prostheses (64% vs. 44%, p=0.011), with both values significantly higher in the observation group. The mean inclination angle, anteversion angle, and limb length discrepancy (LLD) in the observation group were 36.85°±4.82°, 12.10°±5.33°, and 2.18±2.70 mm, respectively, while those in the control group were 35.06°±6.07°, 10.95°±5.09°, and 4.42±3.85 mm, respectively. There was a statistically significant difference between the two groups in terms of inclination angle and LLD (p<0.05 for both), but there was no significant difference in terms of anteversion angle (p>0.05). In the observation group, 86.3% (82/95) of acetabular cups were implanted within the Lewinnek safe zone (72.7% [48/66] in the control group), while 83.2% (79/95) were within the Callanan safe zone (69.7% [46/66] in the control group), with both values higher in the observation group (p<0.05).

Conclusion: Overall, AI-assisted 3D preoperative planning is superior to traditional 2D X-ray template planning for predicting prosthesis size, and it also has the advantage in terms of acetabular cup positioning and lower-limb length restoration.

Figure 1. Preoperative 3D reconstruction, and parameter measurement. (a) Shows the automatic generation of the 3D pelvic reconstruction model by the AIHIP software; (b) shows the preoperative parameters, the red line represents the axis of the femoral bone marrow cavity, the green line represents the horizontal axis of the tip of the femoral lesser trochanter, preoperative lower-limb length discrepancy and offset are shown; (c) shows a 3D view of the acetabulum. AIHIP: Artificial intelligence hip.

Figure 2. The design of prosthesis position. (a) Shows the position and angle of the designed acetabular cup; (b) shows a 3D view of the acetabular cup; (c) shows a 3D view of the femoral components; (d) shows the location of femoral neck resection, D1 is the distance from the tip of the greater trochanter to the shoulder of the femoral component, D2 is the distance from the superior edge of the lesser trochanter to the osteotomy plane.

Figure 3. Postoperative simulation. (a) Is the postoperative 3D simulation, the red line represents the axis of the femoral bone marrow cavity, the green line represents the horizontal axis of the tip of the femoral lesser trochanter, simulated postoperative lower-limb length discrepancy and offset are shown; (b) is the postoperative X-ray simulation.

Figure 4. Postoperative measurement of acetabular angle and both lower-limb length. (a) Shows the measurement of the acetabular abduction angle. A is the line connecting the tear drops on both sides. B is the long-axis connection of the acetabular cup. The lateral angle (a) between A and B is the abduction angle. (b) shows the acetabular anteversion angle measurement. D1 is the short axis of acetabular cup oval shadow. D2 is the long axis of the acetabular cup oval shadow. Anteversion angle = arcsin (D1/D2). (c) shows the LLD measurements. A is the line connecting lower edge of the tear drops on both sides. B and C are the vertical distance from the tip of the femoral lesser trochanter to A of the operative and contralateral side, respectively. The difference between B and C is the difference in lower-limb length. LLD: Limb length discrepancy.

Figure 5. Scatter plot of postoperative acetabular prosthesis position. (a) Shows the situation of postoperative acetabulum located in the safety area of the AI planning group; (b) shows the situation of postoperative acetabulum located in the safety area of the traditional planning group.