Finite-element simulation of flexor digitorum longus or flexor digitorum brevis tendon transfer for the treatment of claw toe deformity

Claw toe deformity sometimes leads to dorsiflexion of the metatarsophalangeal joint (MPJ) and plantar flexion of the proximal (PIPJ) and distal interphalangeal (DIPJ) joints. Flexor digitorum longus tendon transfer (FDL) is currently the gold standard for the correction of this problem. Transfer of the flexor digitorum brevis (FDB) has been recently proposed as an alternative method to treat such deformity. The aim of this work is to compare the biomechanical outcome of these two methods by means of finite-element simulation. The results show that the reduction in the dorsal displacement of the proximal phalanx (PP) for the second and third toes were very similar (about 4.3 mm for each intervention), both achieving a significant reduction in MPJ dorsiflexion when compared to no intervention (displacements are reduced by approximately 51%). In the fourth and fifth toes, only a small correction in the deformity was achieved with both the techniques (10% and 7%, respectively). FDB and FDL tendon transfer reduced the stress level when compared with the non-operated pathologic foot (the reduction of stresses for the second and third PP ranged between 20% and 40%). FDB transfer resulted in a more uniform distribution of stress along the entire toe, although differences were small in all cases. These results confirm that both the tendon-transfer techniques are effective in the treatment of claw toe deformity. Therefore, the choice of technique is at the discretion of the surgeon.