Comparison of G-guide and Image-free Navigation System in Accuracy of Stem Anteversion Assessment During Total Hip Arthroplasty

Yuki Fujihara*, Shigeo Fukunishi, Tomokazu Fukui, Shoji Nishio, Yu Takeda, Shohei Okahisa, Shinichi Yoshiya
Department of Orthopaedic Surgery, Hyogo College of Medicine, Hyogo, Japan

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© 2019 Fujihara et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at Department of Orthopaedic Surgery, Hyogo College of Medicine 1-1, Mukogawacho, Nishinomiya, Hyogo, 663-8501, Japan; Tel: +82-798-45-6452; Fax: +81-798-45-6453;



We have developed and utilized the Gravity-guide (G-guide) as a simple manual instrument for intraoperative assessment and adjustment of stem anteversion (AV). Since 2013, we simultaneously measured stem AV using the G-guide and image-free navigation during THA procedure. The purpose of this study was to compare the measurement accuracy of the G-guide and navigation system using the postoperative CT results as a reference.


In total, 59 hips in 56 patients who underwent primary THA using both the G-guide and image-free navigation system were included in the study. All patients underwent postoperative CT examination, and the femoral stem AV was assessed using a 3D image analysis system (Zed hip, LEXI, Japan). The AV angle derived from the postoperative CT image analysis was used as the reference value to assess the accuracy of the two intraoperative measurement systems.


The discrepancy between the G-guide and the postoperative CT-measured values averaged 5.0° ± 3.9°, while the corresponding value for the navigation system was 5.2° ± 4.1°. Acceptable accuracy with a measurement error of less than 10° was achieved in 86% and 90% of the cases for the G-guide and navigation measurements respectively.


Consequently, it was shown that both navigation and G-guide measurements can achieve comparative accuracy and are clinically useful.

Keywords: Combined anteversion, Dislocation, G-guide, Navigation, Stem anteversion, Total hip arthroplasty.