Article
The EOS 3D imaging system reliably determines posterior tibial slope
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Authors
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Andreas Hecker
- Inselspital, Universitätsklinik Bern, Bern, Switzerland
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Till D. Lerch
- University Institute for Radiology, Inselspital, Bern, Switzerland
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Rainer J. Egli
- University Institute for Radiology, Inselspital, Bern, Switzerland
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Emanuel F. Liechti
- Inselspital, Universitätsklinik Bern, Bern, Switzerland
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Frank M. Klenke
- Inselspital, Universitätsklinik Bern, Bern, Switzerland
| Published: | October 26, 2021 |
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Outline
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Objectives: Planning total knee arthroplasty (TKA) prior to surgery is a mandatory step for success. In many centers routinely anterior-posterior (AP) and lateral standard radiographs of the knee and AP long leg radiographs (LLR) are available for this task. One of the preoperatively determined values is the posterior tibial slope (PTS), which is a proven factor for the success of TKA. It is best measured on CT or at least lateral full tibia radiographs which are routinely not available. Another option that is available in many centers is the EOS 3D imaging system, which provides an AP and lateral LLR with less radiation than a conventional LLR. Therefore, we aimed to investigate its reliability regarding PTS measurements.
Methods: We retrospectively reviewed our radiologic data base between 01/2019 and 12/2019 for patients with an EOS scan and additional rotational CT scan of the lower extremity. 56 knees were included for analysis. Medial and lateral PTS were determined on both EOS radiographs and CT scans. All Measurements were done independently by a radiologist and an orthopedic surgeon at two time points and intra-class correlation (ICC) was calculated to assess inter- and intra-reader reliability. Student's t test and the Pearson correlation were used to compare the results of both imaging modalities.
Results and Conclusion: The mean medial PTS was 8.5° (95% CI, 8.1-8.9°) on EOS and 7.7° (95% CI, 7.3-8.1°) on CT while the lateral PTS was 7.4° (95% CI, 6.9-7.9°) on EOS and 7.0° (95% CI, 6.5-7.4°) on CT. The inter-reader reliability (ICC) was excellent regarding medial and lateral tibial slope on EOS (0.880, 0.765) and CT (0.884, 0.887). The intra-reader reliability of reader 1 (ICC-range, 0.889 to 0.986) and reader 2 (ICC-range, 0.868 to 0.980) were excellent regarding the same measurements.
The EOS 3D imaging system provides reliable and reproducible tibial slope measurements compared to CT measurements as today's gold-standard. We recommend using this technique in preoperative TKA planning if available, because more information is gathered, compared to conventional LLR, with less radiation.
