Quantitative evidence of kinematics and functional differences in different graded trigger fingers.

BACKGROUND Clinical diagnosis and classification of trigger fingers is traditionally based on physical examinations and certain obvious symptoms. However, it might lack quantitative evidence to describe the different graded trigger digits. This study provides quantitative evidence of kinematics and functional differences among different graded trigger fingers based on Froimson's classification. METHODS Forty-seven patients with fifty-five trigger fingers and graded twenty-three, eleven, and twenty-one fingers as grades II, III, and IV, respectively. The QuickDASH questionnaire evaluated the subject's self-perception of hand symptoms and functions. The study measured maximal workspace of the fingertip motion and range of motion of the finger joints during an assigned tendon-gliding task using an electromagnetic tracking device. In addition, R(alpha), defined as the ratio range of angular acceleration during finger extension to the range during finger flexion of each joint, quantified the triggering effect. FINDINGS The QuickDASH score results show that functional performances have significant differences among three grades (P<0.05). Workspace, range of motion of proximal interphalangeal joint and R(alpha) of proximal interphalangeal and distal interphalangeal joint of trigger fingers also significantly differ among three grades (P<0.05). These findings quantitatively show that trigger fingers in different impairment levels have different kinematics and functional performances. INTERPRETATION The results serve as evidence-based knowledge for clinics. The more practical and immediate application of this study would be to facilitate the assessment, design and execution of rehabilitation for patients with trigger fingers.