Functional evaluation of optimal index finger proximal interphalangeal joint fusion angle using a simulated joint arthrodesis

This study aims at qualitatively and quantitatively evaluating the effects of simulated index finger proximal interphalangeal (PIP) joint fusion angles on hand kinematic function and performance. Although arthrodesis of the index finger PIP joint is an effective medical procedure that produces a durable, pain-free, and stable joint, it permanently immobilizes the joint. Twenty healthy subjects performed basic functional hand activities with the index finger PIP joint unconstrained (UC) and constrained to selected angles under surveillance of a motion capture system. Our results indicate differences in perceived difficulty, time performance, and the functional ROM of the hand joints when the index finger PIP joint is UC and constrained to 0, 20, and 40 degrees of flexion. The mean total perceived difficulty scores for all 6 tasks were higher for the PIP at 0 degrees than for the UC condition (p < 0.001) and for the PIP at 40 degrees (p = 0.048). The functional ROM presented a smaller total number of hand joints affected by the PIP at 20 degrees (25 in total) than the PIP at 0 (31 in total) and 40 (27 in total) degrees during execution of all 6 tasks tested. Therefore, the decision on the appropriate index finger PIP angle for arthrodesis may be between 20 and 40 degrees, as globally for all 6 tasks tested, 0 degrees exhibited the worst results regarding perceived difficulty, performance time, and number of joints with affected ROM. Selecting the appropriate angle for arthrodesis should consider a more complete set of functional activities.