Background: Intraoperative fluoroscopy is beneficial when performing total hip arthroplasty (THA) via the direct anterior approach; however, image distortion may influence component placement. A manual gridding system (MGS) and a digital gridding system (DGS) are commercially available, aimed at visually representing or correcting image distortion. Therefore, the purpose of this study is to compare component placement accuracy following direct anterior approach THA when intraoperative fluoroscopy was supplemented with MGS or DGS.
Methods: A retrospective evaluation of acetabular cup abduction (ABD), leg length discrepancy (LLD) and global hip offset difference (GHO) was completed for consecutive patients from 6 week post-THA weight-bearing radiographs. The predefined target LLD and GHO was <10 mm and ABD target was 45° ± 10°. Differences between MGS and DGS were determined by independent t-tests.
Results: The MGS (250 patients, 315 hips) and DGS (183 patients, 218 hips) achieved targeted ABD in 98.7% and 96.8% of cases, respectively, and ABD was significantly lower in the MGS group (45.14 ± 4.03° and 47.01 ± 4.39°, respectively) (P < .001). Compared to MGS, the DGS group averaged significantly higher GHO (3.64 ± 2.44 and 4.45 ± 2.73 mm, respectively, P = .002) but was not significantly different regarding LLD (2.92 ± 2.55 and 3.19 ± 2.46 mm, respectively, P = .275). No significant group difference was noted for percentage within the targeted LLD and GHO; however, 93.5% of DGS and 97.6% of MGS achieved all three (P = .031).
Conclusion: The use of both the MGS and DGS resulted in consistent component placement within the predefined target zone. Although the MGS appeared to be slightly more consistent, these differences are unlikely to be clinically significant.
Keywords: global hip offset; grid; intraoperative fluoroscopy; leg length discrepancy; total hip arthroplasty.
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