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. 2012 Nov 28;4(4):e33.
doi: 10.4081/or.2012.e33. Print 2012 Nov 2.

Combined anteversion of the total hip arthroplasty implanted with image-free cup navigation and without stem navigation

Shigeo Fukunishi  1 , Tomokazu Fukui, Shoji Nishio, Yuki Fujihara, Shohei Okahisa, Shinichi Yoshiya
Affiliations

Combined anteversion of the total hip arthroplasty implanted with image-free cup navigation and without stem navigation

Shigeo Fukunishi et al. Orthop Rev (Pavia). .

Abstract

In total hip arthroplasty (THA), combined anteversion (CA), the sum of cup anteversion (AV) and stem antetorsion (AT) are used as parameters to assess the appropriateness of overall prosthetic alignment. In this study, we evaluated the CA value based on the post-operative computed tomography (CT) measurements in our patient population who underwent THA using the OrthoPilot™ image-free navigation system (B/BRAUN-Aesculap, Tuttlingen, Germany). During surgery, cup alignment was adjusted with the use of the navigation system while the positioning of the femoral stem was arbitrarily adjusted by the surgeon. Seventy-nine THAs were included in the study. Post-operative CT assessment for the prosthetic alignment showed the average cup inclination and AV values to be 40.5°±4.1° and 20.6°±4.6°, respectively, demonstrating the effectiveness of the navigation system by small values of standard deviation. By contrast, the AT value measured for the stem showed wide variability (mean 23.6°±11.2°). Consequently, the resulting CA was also inconsistent (mean 44.4°±11.2°) and only 61 of the 79 THAs (77.2%) were defined as satisfactory.

Keywords: THA; combined anteversion; image free navigation..

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Conflict of interest statement

Conflict of interests: the authors report no conflict of interests.

Figures

Figure 1
Figure 1
Scatter plots showing anteversion and X-ray inclination of the cup. Post-operative cup anteversion and inclination in each patient are presented by a dot. Range of Lewineck's safe zone is shown by the solid square. Cup alignment in 72 cases (91.1%) fell within Lewinnek's safe zone.
Figure 2
Figure 2
Scatter plots showing stem antetorsion. Distribution of antetorsion values were scattered as shown by large standard deviation values (range 2–45°).
Figure 3
Figure 3
Scatter plots showing combined anteversion. Distribution of combined anteversion values were scattered as shown by large standard deviation values (range 23.0–65°).
Figure 4
Figure 4
Scatter plots showing Widmer's combined anteversion. The two solid lines indicate the satisfactory range: 37°±10° (27° and 37°). The combined anteversion values in 61 cases (77.2%) were within this satisfactory range, while the corresponding values in the remaining 18 total hip arthroplasties (23.8%) fell into the less optimal category.
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