The accuracy of an accelerometer-based portable navigation system for total hip arthroplasty using 3D CT measurement in the supine position: a prospective multicenter study

•This multicenter prospective study evaluated the accuracy of the navigation system.•324 THAs using supine position in 9 hospitals were prospectively enrolled.•Cup alignment was measured on postoperative 3D-CT images.•The accuracy was 3 ​± ​3°for cup inclination and 3 ​± ​3° for cup anteversion.•The patients' factor, surgical factor, or pelvic movement did not affect the accuracy.