Abstract: Objective　To provide anatomical basis for mini plate internal fixation of bony mallet finger by anatomical study of the zoneⅠ terminal extensor tendon and adjacent tissues.　Methods　Ten adult hand cadavers’ upper limb specimens were dissected and the anatomical relationships between nail matrix, nail root and zoneⅠ terminal extensor tendon were observed. Microscopically, the distance from the terminal extensor tendon to nail root, nail matrix, articular surface were measured. The width of zoneⅠ terminal extensor tendon and the transverse and vertical diameters of phalangette joints were measured.　Results　The proximal margin of the nail root did not completely cover the germinal matrix, and the distance between the zoneⅠ terminal extensor tendon and the germinal matrix was（1.21±0.21）mm.There was a loose connective tissue between them. The width of terminal extensor tendon was（6.27±1.23）mm,  horizontal thickness was (1.02±0.21) mm. The distance between the zoneⅠ terminal extensor tendon and the articular of the distal interphalanx was （1.22±0.21）mm. The transverse diameter of the distal phalanx articular surface was (8.00±2.21)  mm, the longitudinal diameter was （6.22±1.21）mm. ZoneⅠ terminal extensor tendon was closely connected to the dorsal articular capsule of distal interphalangeal joint.　Conclusions　The longitudinal dorsal median skin incision on the distal phalangeal bone can fully reveal the tissue structure around zoneⅠ terminal extensor tendon. In fixing the avulsed fracture fragment of the distal phalanx, the plate is partially overlapped with the nail matrix, and the nail root and nail matrix need to be partially incised. The terminal extensor tendon is closely linked to the dorsal capsule of distal interphalangeal joint, where the zoneⅠterminal extensor tendon has a dorsal fibrous cartilage tissue plate, just like the volar plate.

Key words: Terminal extensor tendon, 　Germinal matrix, 　Bony mallet finger, 　Applied anatomy, 　Distal interphalangeal joint