Two computer programmes (MSC.visualNastran Desktop 2002™ and Solid Edge® V19) were used to generate a human ankle joint model. Different attachment points of FHL tendon transfer to the calcaneus were investigated.
The lowest muscle force to produce plantarflexion (single stance heel rise) was 1355 N. Plantarflexion increased for a more anterior attachment point. The maximum range of plantarflexion was 33.4° for anterior attachment and 24.4° for posterior attachment. There was no significant difference in range of movement when the attachment point was moved to either a medial or lateral position.
A more posterior attachment point is advantageous in terms of power and the arc of motion (24.4°) is physiological. We recommend that FHL is transferred to the calcaneus in a posterior position.