# Evaluation of the Accuracy of Intraoperative Femoral Stem Anteversion Using a Mechanical Alignment Guide and a CT-Based Navigation System

## TL;DR

This study compares two methods for measuring femoral stem placement during hip surgery, finding that a CT-based system is more accurate than a mechanical guide.

## Contribution

The study provides a direct comparison of intraoperative femoral stem anteversion accuracy between a CT-based navigation system and a mechanical alignment guide.

## Key findings

- CT-based navigation had a 2.9° ± 3.1° discrepancy compared to postoperative measurements.
- Mechanical alignment guides had a 7.6° ± 5.2° discrepancy compared to postoperative measurements.
- CT-based navigation was significantly more accurate (p = 0.001).

## Abstract

Background

In total hip arthroplasty (THA), implant position is one of the critical factors affecting implant longevity, clinical outcomes, and postoperative complications. Although a number of studies have reported the accuracy of acetabular component positioning using a computed tomography (CT)-based navigation system, the significance of femoral stem anteversion has not been well addressed in the literature.

Methods

Stem anteversion in 83 patients who underwent primary THA and bipolar hemiarthroplasty was simultaneously measured with both a CT-based navigation system and a mechanical alignment guide during surgery. Both intraoperative measurement values were compared with the postoperative measurement values using the same three-dimensional coordinate system.

Results

The absolute discrepancy between the mechanical alignment guide value and the postoperative stem anteversion was 7.6° ± 5.2° (range: 0° to 17°). On the other hand, the absolute discrepancy between the intraoperative stem anteversion value measured with CT-based navigation and the postoperative stem anteversion was 2.9° ± 3.1° (range: 0° to 14°). The absolute discrepancy was significantly lower in intraoperative CT-based navigation (p = 0.001).

Conclusion

Intraoperative stem anteversion measurements using CT-based navigation were more accurate than those using the mechanical alignment guide.