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Excessive limb alignment during plain radiographs causes errors in femoral tunnel position estimates
Van Eck, C. Knee Surg, Sports Traumatol Arthros. 2011; DOI: 10.1007/s00167-011-1683-x
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Limb malalignment during lateral radiographs can introduce errors in femoral tunnel position estimates following anatomic double-bundle and nonanatomic single-bundle knee reconstruction, according to researchers from Pittsburgh.
The study also notes, however, that lateral radiographs can adequately determine tunnel position after both types of knee reconstruction when valgus and internal rotation remain under 10°.
Researchers digitally reconstructed lateral radiographs from 3D CT scans of 10 patients, 5 of which had each type of reconstruction. The femur was then rotated to simulate internal/external and varus/valgus rotations from 0° to 15° in increments of 5°. Tunnel position relative to Blumensaat’s line was then calculated and compared to results of lateral radiographs.
The team found that valgus and internal rotation of more than 10° can introduce “significant errors” in tunnel position estimates.