Fig. 4: Cadaver testing results.

a Cadaver hand with biological thumb (left), biosynthetic thumb (middle), and biosynthetic thumb with flap coverage (right). b Radiographic images showing the biosynthetic thumb with flap coverage in the rest position (left) and at full flexion (right). c MCP-IP angle relationship for the cadaver hand with biological thumb and with biosynthetic thumb, when actuated only by pulling on the FPL tendon. Solid blue and green lines represent the mean of 10 trials, and shaded regions show +/−1 standard deviation. Predictions from the as-implanted linkage model are also shown for comparison (red). d IP (top) and MCP (bottom) flexion angle as a function of FPL tendon excursion. Zero excursion represents resting tension in the FPL tendon. Solid lines represent the mean of 10 trials, and shaded regions show +/−1 standard deviation.