John Hodgson1, David Shin1, Gajanan Nagarsekar1, V Reggie Edgerton2, Shantanu Sinha1
1Radiology, University of California at San Diego, San Diego, CA, USA; 2Physiological Sciences, University of California at Los Angeles, Los Angeles, CA, USA
A retinaculum-like restriction on the Achilles tendon has been postulated to modify the mechanics of ankle rotation, possibly amplifying the tendon displacement to a larger displacement of the calcaneous. We have used spin-tag MRI to image the movement of the tendon/aponeurosis and the calcaneous during computer-controlled plantarflexion movements of the foot under passive and active conditions. The lever arm length was determined to be ~53.1 +/- 3.8 mm. Measurements revealed a non-uniform displacement of tendon and aponeurosis along the S/I direction and a potential amplification factor of 1.1. This could have a significant impact of experimentally observed Achilles tendon strain.