The effects of radial/ulnar deviation and pronation/supination on the displacement of index finger flexor tendons at the level of the radial styloid

MR images of the distal upper limb of four participants were obtained. Participants were braced in 3 different wrist postures (radial deviation, neutral, ulnar deviation), in combination with 3 forearm postures (pronation, mid, supination). The flexor digitorum superficialis (FDS2) and profundus (FDP2) tendons to the index finger from each image were segmented proximal and distal to the level of the radial styloid and displacement calculated in frontal plane. a significant shift of the FDS2 occurred with both wrist deviation and forearm rotation. Both supination and ulnar deviation displace the tendon ulnarly. This displacement of tendon can cause frictional work to occur on the tendons, which can lead to tissue damage and injury.