Validating a Modified Circle Theorem Method for the Measurement of Acetabular Cup Anteversion on Plain Radiography with Intra-Operative Data from Robotic Assisted Total Hip Arthroplasty
Authors: Amirouche F, Solitro GF, Chandrasekaran S, Domb BG, Gonzalez MH
DOI: 10.1016/j.arth.2015.07.042
Purpose
To validate a modified circle theorem method for measuring acetabular cup anteversion on standard X-rays compared to intraoperative robotic data.
Methods
- 80 total hip arthroplasties with robotic intraoperative anteversion measurements.
- Compared robotic data to anteversion calculated on AP radiographs using the modified circle theorem.
Key Findings
- Mean robotic anteversion: 21.2° ± 2.0°, radiographic anteversion: 19.9° ± 3.4°.
- 97.5% of radiographic measurements were within 30% relative error of robotic data.
- Strong correlation between radiographic and robotic measurements (Pearson r = 0.9422).
What Does This Mean for Providers?
- The modified circle theorem provides a reliable, reproducible method for estimating acetabular cup anteversion on plain radiographs.
- This technique can enhance postoperative assessment without need for advanced imaging or CT scans.
- Facilitates accurate implant positioning verification in routine clinical follow-up.