Figure 5:

Final equilibrium positions of the 9 forward simulations with shortened flexor muscles. Claw finger deformity was defined to be present when the final position included both hyperextension (extension beyond 0 degrees) of the MCP joint and concurrent flexion of the PIP joint greater than 20 degrees. In this figure, a red “+” indicates when either of these two conditions was present in a single simulation. The simulation results indicate that the deformity is sensitive to both impairment level and muscle excitation. Specifically, mild changes (98% L_mt,r) yielded the claw finger deformity at low excitation levels, but finger extension was achieved with higher excitations (top row). In contrast, coordinated finger extension was not achievable at any excitation level following moderate (95% L_mt,r) and severe (95% L_mt,r) changes (middle and bottom rows).