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. Author manuscript; available in PMC: 2020 Sep 1.
Published in final edited form as: J Hand Surg Am. 2019 Jun 24;44(9):751–761. doi: 10.1016/j.jhsa.2019.05.007

Figure 8:

Figure 8:

Final equilibrium positions for the 9 forward simulations of the models combining the mild, moderate, and severe changes and a flexed wrist. Red “+” indicates either the MCP is hyperextended or the PIP is flexed more than 20 degrees, positive for both indicates the claw finger deformity. As the wrist is flexed the muscle-tendon lengths of the extrinsic finger flexors shorten to lengths closer to Lmt,r. Thus, the passive resistive forces produced by the flexor muscles about the PIP joint are smaller at 30° wrist flexion than at 30° wrist extension, allowing the forces produced by the extensor muscles to be more effective.