In 2018, during our first clinical study on the kineticomyographic (KMG)-controlled bionic hand, we implanted three magnetic tags inside the musculotendinous junction of three paired extensor-flexor transferred tendons. However, the post-operative tissue adhesions affected the independent movements of the implanted tags and consequently the distinct patterns of the obtained signals. To overcome this issue, we modified our surgical procedure from a one-stage tendon transfer to a two-stage. During the first surgery, we created three tunnels using silicon rods for the smooth tendon gliding. In the second stage, we transferred the same three pairs of the forearm agonist–antagonist tendons through the tunnels and implanted the magnetic tags inside the musculotendinous junction. Compared to our prior clinical investigation, fluoroscopy and ultrasound evaluations revealed that the surgical modification in the current study yielded more pronounced independent movements in two specific magnetic tags associated with fingers (maximum 5.7 mm in the first trial vs. 28 mm in the recent trial with grasp and release) and thumb (maximum 3.2 mm in the first trial vs. 9 mm in the current trial with thumb flexion–extension). Furthermore, we observed that utilizing the flexor digitorum superficialis (FDS) tendons for the flexor component in finger and thumb tendon transfer resulted in more independent movements of the implanted tags, compared with the flexor digitorum profundus (FDP) in the prior research. This study can help us plan for our future five-channel bionic limb design by identifying the gestures with the most significant independent tag displacement.

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