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Implant Orientation Measurement After THA Using the EOS X-Ray Image Acquisition System
Kunihiko Tokunaga1, Masashi Okamoto2, Kenji Watanabe3
1Niigata Hip Joint Center, Kameda Daiichi Hospital, Niigata City, Japan. ktokunagajp@yahoo.co.jp.
Advances in Experimental Medicine and Biology
|October 12, 2018
Summary
The EOS system shows potential for measuring total hip arthroplasty (THA) implant orientation, but accuracy issues with cup inclination, anteversion, and stem antetorsion require improvement before clinical use.
Area of Science:
- Orthopedic Surgery
- Medical Imaging
- Biomedical Engineering
Background:
- Accurate measurement of implant orientation is crucial for successful total hip arthroplasty (THA).
- The EOS system offers a low-dose imaging solution for evaluating implant positioning in a standing position.
- Current limitations exist in applying 3D bone models for precise reference point definition.
Purpose of the Study:
- To investigate the accuracy of the EOS system for measuring implant orientation (cup inclination, anteversion, and femoral stem antetorsion) after THA.
- To compare EOS measurements with computed tomography (CT) scans, considered a gold standard.
- To identify potential sources of error and limitations of the EOS system in this application.
Main Methods:
- Ninety patients undergoing THA were analyzed.
- Implant orientation was measured using the EOS system and compared to CT scans with 3D analysis software (ZedHip).
- Measurements included cup inclination and anteversion relative to the anterior pelvic plane (APP), and stem antetorsion relative to the femoral functional axis.
Main Results:
- Mean differences between EOS and CT were -2.3° ± 2.7° for cup inclination, -0.1° ± 5.0° for cup anteversion, and -1.3° ± 6.5° for stem antetorsion.
- Outlier measurements (differences > 5°) were observed in 14 hips for cup inclination, 28 for cup anteversion, and 27 for stem antetorsion.
- Difficulties in defining APP reference points and discrepancies in the APP coordinate system contributed to measurement outliers.
Conclusions:
- The EOS system demonstrated variability in measuring implant orientation after THA, particularly for cup anteversion and stem antetorsion.
- Challenges with reference point definition on 3D models and inconsistencies in the APP coordinate system limit the current accuracy of the EOS system for THA implant positioning.
- Further improvements are needed to enhance the reliability and clinical applicability of the EOS system for post-THA implant assessment.
Keywords:
EOS systemImplant orientationPostoperative evaluationTotal hip arthroplasty (THA)ValidationMore Related Videos
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