The effect of flexor digitorum profundus quadriga on grip strength.

This study evaluated the flexor digitorum profundus quadriga effect by mimicking stiffness of one finger and observing its effect on the strengths of the other three fingers of the same hand. Thermoplastic wedges were used to simulate mild, moderate and severe stiffness of each finger and the individual strengths of each finger during power grip were measured using a digit-grip(TM) dynamometer in ten healthy adult volunteers. Middle, ring, and little fingers strength diminished significantly (P<0.05) when each of the other fingers, including the index, was stiffened. Index finger strength was largely unaffected by simulated stiffness of the other fingers. The degree of simulated stiffness influenced the strength of the other fingers, but there was considerable intersubject variability, suggesting that the significance of the quadriga effect varies between individuals. An anatomical basis for our findings is suggested.