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Objectives and questions: Accurate acetabular component positioning in total hip arthroplasty (THA) is critical to optimizing joint stability, reducing impingement, and preventing early revision. Malpositioning increases the risk of complications such as dislocation, edge-loading, accelerated wear, and implant failure. Navigation-assisted techniques have been developed to improve component placement accuracy, but their efficacy compared to conventional fluoroscopy in the direct anterior approach (DAA) remains unclear. This study evaluates the accuracy of acetabular component positioning using conventional fluoroscopy, fluoroscopic image-dependent navigation (Velys™), and imageless navigation (Intellijoint Hip^®) in DAA-THA. We hypothesized that navigation-assisted techniques would yield superior alignment compared to conventional fluoroscopy.

Material and methods: A retrospective cohort study was conducted on 150 patients who underwent primary DAA-THA, divided equally into three groups: conventional fluoroscopy, fluoroscopic navigation (Velys™), and imageless navigation (Intellijoint Hip^®). Intraoperative inclination and anteversion angles were recorded and compared with six-week postoperative radiographs. Primary outcomes included deviations in anteversion and inclination from target zones. Secondary outcomes included operative time and 90-day complication rates. Statistical analyses were performed using ANOVA and t-tests, with significance set at p<0.05.

Results: Mean operative time was longest in the imageless navigation group (75.5 ± 10.8 min) compared to fluoroscopy (65.8 ± 8.5 min) and Velys™ (68.9 ± 10.7 min) (p<0.0001). Radiographic accuracy analysis demonstrated that fluoroscopic navigation (Velys™) achieved the highest proportion of cups placed within target zones (83% and 69% across two surgeons), outperforming both conventional fluoroscopy and imageless navigation. While imageless navigation demonstrated improved accuracy over conventional fluoroscopy, it showed greater variability in anteversion precision. No significant differences were observed between groups for final postoperative inclination (p=0.94) or anteversion (p=0.08). Complication rates were similar across groups, with one periprosthetic joint infection in both the conventional and Velys™ groups, and none in the imageless navigation group.

Diskussion und Schlussfolgerung: Fluoroscopic image-dependent navigation (Velys™) demonstrated superior accuracy in acetabular component positioning compared to conventional fluoroscopy in DAA-THA, with the highest percentage of cups placed within the target zone. Imageless navigation showed potential benefits but required refinement for improved anteversion accuracy and reduced operative time. These findings suggest that fluoroscopic navigation is a valuable tool for enhancing precision in DAA-THA and may contribute to reducing implant malposition-related complications. Further research is needed to determine the long-term impact of navigation-assisted techniques on patient outcomes and implant survivorship.