gms | German Medical Science

Objective: Human fingers and the palmar shape of the hand are important for hand shaping. The palmar shape modulation, which provides the hand's postural base, is one of the critical factors to perform appropriate finger movements. The palmar shape modulation would be associated with finger joint movements in hand shaping; however, little is known about their kinematic correlations. This study aimed to examine the correlation between the palmar shape modulation and finger joint movements during hand shape formation.

Materials and Methods: Twenty right-handed adults performed a reach-to-grasp task, which consists of two object shapes (cylinder and sphere) and two object sizes (50 and 100 mm). During the task, we captured the displacements of the dorsal hand and middle finger joints by using a twelve-camera motion analysis system and calculated the angular ranges and traces of the palmar oblique arch, transverse arch, and DIP, PIP, and MP joint of the middle finger during hand shaping. The angular ranges of two object shapes and two sizes were compared, and the angular traces were analyzed by Pearson correlation and principal component analysis.

Results: The palmar oblique arch, transverse arch, DIP, and PIP joint significantly changed according to object shapes and sizes. There were strong correlations between angular traces of the palmar oblique arch, transverse arch, DIP, and PIP joint in both object shapes and sizes. Principal component analysis showed that the palmar oblique arch, transverse arch, DIP, and PIP joint contributed to hand shaping in both object shapes and sizes.

Conclusions: Our findings may suggest that the palmar shape modulation is associated with the DIP and PIP joint movements during hand shaping. When treating hand disorders, hand therapists may need to provide a therapeutic approach according to the correlation between the palmar shape modulation and the DIP and PIP joint movements during hand shaping.