Pseudo-tendinopathy on MRI of the navicular and tarsometatarsal parts of the tibialis posterior tendon: A study in normal individuals.

PURPOSE: To determine the normal thickness and MRI appearance of the Tibialis Posterior Tendon near the navicular insertion in normal volunteers.

MATERIALS AND

METHODS

By using a 3T MRI system 41 ankles were imaged, and PD weighted images with fat saturation were acquired in the three orthogonal planes. Symptoms of tendon pathology and history of trauma or surgery of the tendon were used as volunteer exclusion criteria. Two different measurement points were determined to evaluate hyperintensity and thickness. Two radiologists assessed the internal signal of the Tibialis Posterior Tendon independently by using axial and coronal images. Tendon hyperintensity was classified from homogenously dark to different degrees of hyperintense signal, where 0 means no internal hyperintensity, 1 - minimal hyperintensity, 2 - moderate and 3 - marked. Correlations between the two observers were obtained by Cohen's kappa. Descriptive statistics were also obtained.

RESULTS

Eight men and 13 women (total 21) volunteers, age range 19-43(average 24.7)years were included in the study. At measurement point-1 on the coronal images, observer-1 and observer-2 evaluated hyperintensity (mostly minimal) respectively in 90.5% and 95.3% of tendons with a Cohen's kappa coefficient of 0.701 (moderate agreement) for the right foot and in 60% and 70% of tendons with a Cohen's kappa coefficient of 0.624 (moderate agreement) for the left foot. On axial images both observers assessed hyperintensity (mostly marked) in 100% of the tendons with a coefficient of 0.763 (moderate agreement) for the right foot, and in 95% of tendons with a coefficient of 0.839 (strong agreement) for the left foot. At measurement point-2 on coronal images, both observers rated any degree of hyperintensity in 33.3% of tendons with a coefficient of 1.00 (perfect agreement) for the right foot, in 38.9% of tendons with a coefficient of 0.766 (moderate agreement) for the left foot. On axial images both observers evaluated hyperintensity (mostly minimal) in 100% of tendons with a kappa coefficient of 0.702 (moderate agreement) for the right foot, in 95% of tendons with a coefficient of 0.790 (moderate- to strong agreement) for the left foot.

CONCLUSION

The Tibialis Posterior Tendon, near the navicular insertion (navicular tendon and tarsometatarsal tendon), exhibits an apparent thickening and most importantly hyperintensity which should be regarded as a normal finding, and not lead to an erroneous diagnosis of tendinopathy. This observation was almost always the case for the navicular insertion and less so for the tarsometatarsal tendon.