Kinematic MRI of the normal ankle ligaments using a specially designed passive positioning device.

Background: Knowledge of the normal MRI appearances of the ankle ligaments and tendons is particularly important in the diagnosis of ankle sprains. In most clinical practices, the ankle is imaged in a neutral position with standard imaging planes and sequences. The purpose of our study was to investigate whether passive positioning influences the MRI appearances of the ligaments of the ankle.

Methods: The axial and coronal T1-weighted MR images obtained from 10 subjects were reviewed by two musculoskeletal radiologists. The following imaging planes were used: dorsiflexion with inversion, dorsiflexion with neutral, dorsiflexion with eversion, neutral with inversion, neutral, neutral with eversion, plantarflexion with inversion, plantarflexion with neutral, and plantarflexion with eversion. A subjective rating system was used to determine the optimal imaging plane and position for individual ligaments in each volunteer. Each ligament was rated on a scale (of 1 to 6).

Results: There were significant differences in the appearances of the anterior talofibular (p = 0.0002), calcaneofibular (p < 0.0001), and posterior talofibular (p < 0.0001) ligaments between the optimal and least optimal ankle positions in the axial plane, and in those of the (plantar calcaneonavicular) spring (p < 0.0001), tibiocalcaneal (p < 0.0001), posterior tibiotalar (p = 0.0087) and posterior talofibular (p = 0.0213) ligaments in the coronal plane.

Conclusions: Kinematic MRI of the ankle is feasible and appears to improve visualization of ankle ligaments compared to MRI.