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

Purpose

This multicenter prospective study aimed to evaluate the accuracy of the cup alignment of an accelerometer-based portable navigation system (AP navigation) for a total hip arthroplasty (THA) in spine position.

Methods

This study prospectively enrolled 324 THAs using supine position in 9 hospitals. An AP navigation was used for cup fixation and the intraoperative navigation data (cup alignment, pelvic tilt, and pelvic rotation) were recorded. Computed tomography (CT) of the pelvis was performed 2 weeks post-operatively and cup alignment was measured on 3D-CT images.

Result

The accuracy (absolute difference in cup alignment between the intraoperative navigation record and postoperative 3D-CT measurements) was 3 ​± ​3° (mean ​± ​standard deviation) for cup inclination and 3 ​± ​3° for cup anteversion. The pelvis tilted anteriorly in 148 hips (46%) and posteriorly in 162 hips (50%), and did not tilt in 14 hips (4%). The pelvis rotated toward the operating side in 179 hips (55%), toward the contralateral side in 112 hips (35%), and did not rotate in 33 hips (10%). Multiple regression analysis showed that the patients’ characteristics (sex, body mass index, diagnosis, Crowe classification, laterality, intraoperative pelvic tilt, intraoperative pelvic rotation, and cup size) and the surgical factors (approach, preparation time, number of screws, and institution) did not affect the accuracy of the navigation system.

Conclusions

This is the first prospective multicenter study of this navigation system. The accuracy was not affected by patient characteristics, surgical factors, or substantial pelvic movement during cup fixation.