The study, by researchers from Charité-Universitätsmedizin Berlin, found that the new technique's ability to assess ligaments under stress and differentiate between instability of the talocrural and subtalar joints made it more advantageous than common stress tests.
X-ray stress radiographs commonly are taken of the talocrural joint, leaving the subtalar joint unexamined. Separate angulated x-ray images are necessary when instability of the subtalar joint is suspected to differentiate between upper and lower ankle joints radiographically, explained study co-author Christian Seebauer, MD.
"MRI is superior to any other imaging method for visualizing ligaments of the foot and precisely differentiating ligament tears and other causes of ankle pain, such as fracture, osteochondral injury, or tendon injury," Seebauer added. "MRI may be superior in imaging the upper and the lower ankle simultaneously; thus, MRI may differentiate instability in both joints."
Researchers used an MR-compatible stress device developed in cooperation with Telos of Marburg, Germany, to image 64 ankle joints of 32 healthy volunteers (16 males, 16 females). The images were compared with 20 ankles of 10 volunteers (eight males, two females) who suffer from chronic ankle joint instability.
Measurements were performed on a 1.5-tesla MRI scanner (Philips Healthcare, Andover, MA). The talar tilt, subtalar tilt, anterior talus translation, anterior calcaneus translation, lateral translation of talus and calcaneus, and the ligaments of the lateral ankle were assessed with a stress challenge.
The analyses found that the talocrural and subtalar joints could be assessed simultaneously in coronal images, and that MRI allowed direct differentiation of tilt differences between talocrural and subtalar joints.
There also was a significant gender difference found in the lateral ankle in ligament thickness and thickness decrease among healthy volunteers and significant differences between the healthy group and volunteers with chronic ankle joint instability for the talar tilt, anterior talus translation, and anterior calcaneus translation.
Based on the results, Seebauer and colleagues wrote that MR-stress imaging "may objectively distinguish instability between talocrural and subtalar joints, and differentiate other reasons for ankle pathology at the same time."
The clinical benefit is that stress evaluation of ankle disorders "can be imaged more sufficiently without radiation exposure and provides the basis for more specific precise therapy," Seebauer said. "Attention had to be paid to the subtalar joint, especially in female athletes with a history of chronic instability of the ankle joint."
The researchers are currently increasing of the number of patients, especially in the instability group, for additional study. Moreover, Seebauer and colleagues plan to extend the field of application in a separate study of insufficiencies to the cruciate ligaments of the knee using the MRI-stress device.