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Copyright of Operative Orthopädie und Traumatologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Obere Extremitat is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The hypothesis of this study was that length, torsion, and axis of a leg phantom can be measured accurately and reproducibly by magnetic resonance imaging (MRI) and that this can be applied to patients with leg deformities. Two phantoms and 30 patients (genu varum, n = 15; genu valgum, n = 15) were investigated using an optimized MRI technique. Reference measurements were performed with a micrometer screw and a goniometer. Patient leg length and axis were compared with long radiographs in bipedal stance. Intra- and interobserver reproducibility and accuracy were calculated using the mean absolute difference (MAD) and the 95% confidence interval. In patients, comparisons were done using a paired Student's t-test. MAD, intraobserver MAD, and interobserver MAD were 0.03, 0.03, 0.04 mm (length); 0.98, 1.2, 0.98 degrees (torsion); and 0.18, 0.23, 0.22 degrees (axis), respectively. In patients, leg length was underestimated by MRI (-2.4 +/- 0.7%; 1.9 +/- 0.7 cm; P < 0.001). The hip-knee-ankle angle (HKA) did not show significant differences in varus knees (-0.5 +/- 1.0 degrees ; P > 0.05), while it was significantly underestimated in valgus knees (-3.6 +/- 2.8 degrees ; P < 0.05). The phantom study revealed that leg length, torsion, and axis can be measured accurately and reproducibly by MRI. Although underestimation of leg length and HKA in valgus knees occurred, this optimized MRI technique can be applied to patients with leg deformities. [ABSTRACT FROM AUTHOR]

Objective: To analyze menisco-tibial and femoro-tibial translation patterns in healthy and ACL-deficient knees in different knee flexion angles under muscle activity.Methods: The ACL-deficient and contralateral healthy knees of 10 patients were examined with an open MR system at 30° and 90° of knee flexion, under isometric contraction of the extensors or flexor muscle groups. Translations between the tibia, the femoral condyles and the menisci were analyzed by three-dimensional image postprocessing.Results: Posterior translation of the femur and menisci relative to the tibia occurred during knee flexion (30–90°) in all knees. In ACL-deficient knees, posterior translation of the medial femoral condyle (+1.3 ± 3.8 mm) was significantly larger than in healthy knee (−0.9 ± 2.9 mm; p<0.05), while the translation pattern of the menisci was similar (med. meniscus 0.6 ± 2.3 mm vs. 0.6 ± 2.7 mm). Under isometric contraction of the extensors (relative to the flexor muscle group), an increased posterior position of the femur and menisci was observed at 30° knee flexion, but not at 90°. This applied to ACL-deficient and healthy knees.Conclusions: This study shows a significant increase of translation of the medial femoral condyle in ACL-deficient knees, whereas menisco-tibial translation remains almost unchanged. This difference in translation patterns indicates that the posterior horn of the medial meniscus might encounter shear, potentially explaining the high rate of secondary medial meniscal tears in patients with ACL-deficiency. [Copyright &y& Elsevier]