Fluoroscopic Imaging of Acetabular Cup Position During THA Through a Direct Anterior Approach

To the Editor:

The recent article “Fluoroscopic Imaging of Acetabular Cup Position During THA Through a Direct Anterior Approach,” by Alvarez et al,¹ was well written, and the content should be beneficial to surgeons performing total hip arthroplasty (THA) using this approach. However, the article contains an error that could potentially mislead surgeons using a direct anterior approach toward achieving the desired cup anteversion.

According to Figure 3’s caption, when the fluoroscopic beam is moved in the cephalic direction, the cup position appears more anteverted, and when it is moved in the caudal direction, the cup position appears less anteverted. This should actually be the other way around—when the beam is moved in the cephalic direction, the cup should look less anteverted, and when the beam is moved in the caudal direction, the cup should look more anteverted. This is evident when looking at Figures 3A (showing less anteversion) and 3B (showing more anteversion).

Figure 3: Fluoroscopic images showing the difference in acetabular cup positioning as the mobile image intensifier is moved in a caudal-cephalad direction. When the fluoroscopy beam is moved in the cephalic direction, the cup position appears less anteverted (A). When the fluoroscopy beam is moved in the caudal direction, the cup position appears more anteverted (B).