Influence of Index Finger Proximal Interphalangeal Joint Arthrodesis on Precision Pinch Kinematics

Purpose To evaluate the impact of proximal interphalangeal (PIP) joint arthrodesis on the kinematics of precision pinch. Methods Eleven healthy subjects performed index finger-thumb pinch motions under 4 conditions: unrestricted thumb and index finger (CONTROL) and fusion of the PIP joint of the index finger in flexion of 30 degrees (PIP30), 40 degrees (PIP40), and 50 degrees (PIP50). Fusion was simulated with metallic splints. Kinematics of the thumb and index finger were recorded with a motion capture system. Results Proximal interphalangeal joint fusion at 30 degrees, 40 degrees, and 50 degrees restricted maximal pinch span between the thumb tip and index finger tip by 6%, 10%, and 14%, respectively. At the time of pulp contact, PIP fusion led to an increase in index metacarpophalangeal joint flexion angle for the PIP30 condition and an increase in variability of thumb tip location for the PIP50 condition. Furthermore, the dynamic coordination between joint angles throughout the movement was affected by PIP fusion. Conclusions This study reports impairment in the kinematics of precision pinch associated with index finger PIP joint fusion. A PIP joint fusion at 40 to 50 leads to a more natural precision pinch posture, but it restricts the aperture and reduces pinch precision. (J Hand Surg 2011;36A:1944-1949. Copyright (C) 2011 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Prognostic I.