Precision grip with congenital hypoplasty or hypofunction of the thumb

We tested the grip in four patients with congenital defects of the hand and either a hypoplastic thumb or a thumb with impaired inervation. Small objects were taken by a scissors grip between the fingers. In a hand with radial duction in the manus vara congenita, during strengthening of the wrist, the grip from the ulnar side between the fourth and fifth fingers was changed to the radial side between the second and third fingers. Large objects were gripped by all the three-phalanx fingers into the palm in a horizontal position. In case 4 with hypoplasia of the thumb grade IIIC by the classification of Blauth and Buck-Gramcko, we describe a transposition of the index finger to the site of the thumb and the hypoplastic thumb to the site of the index finger. It is obvious that the precision grip is affected by the thumb length and strengthening of the ulnar side of the wrist. We assume that the scissors grip is the earliest precision grip in the evolution of the primate hand.