Accuracy of cup placement using computed tomography-based navigation system in total hip arthroplasty through the direct anterior approach.

BACKGROUND

This study aimed to elucidate the accuracy of cup placement with the computed tomography (CT)-based navigation system (CTN) in the direct anterior approach (DAA)-total hip arthroplasty (THA) in the supine position compared with the mechanical cup alignment guide (MG) or the fluoroscopy (FS).

METHODS

A total of 171 hips of 156 patients undergone primary THA were classified into the following three groups (the MG group: 63 hips, the FS group: 58 hips, the CTN group: 50 hips). Comparing the preoperative planning with postoperative CT measurement by three-dimensional templating software, the accuracy of cup placement was investigated in the three groups.

RESULTS

There were significant differences in the mean absolute error of radiographic inclination (RI) between the MG group (4.4° ± 3.2°) and the CTN group (2.8° ± 2.5°) (p = 0.01). The mean absolute error of radiographic anteversion (RA) also showed significant differences between the CTN group (2.8° ± 1.9°) and the MG group (5.8° ± 4.7°) (p = 0.0001) or the FS group (4.8° ± 4.1°) (p = 0.02). Regarding the cup center position, the mean absolute error of vertical position from preoperative planning was the smallest in the CTN group (1.8 ± 1.4 mm) compared with those in other groups (MG: 3.3 ± 3.2 mm, p = 0.007, FS: 3.2 ± 3.0 mm, p = 0.017).

CONCLUSION

The CTN guarantees accurate cup placement in the DAA-THA in the supine position compared with the MG and FS groups.