Objective To study the differences of the volar and dorsal insertion of flexor digitorum profundus tendon and extensor tendon in the base of the distal phalanx and provide anatomical base for possible mechanism of Seymour fracture. Methods 10 hand specimens were collected from the anatomical laboratory of the hospital, including 3 left hand cases and 7 right hand cases, all of which were male patients，aged 24~58 years old. All 2~5 fingers were 10 fingers respectively, and all fingers had no history of traumatic surgery or deformity. The flexor digitorum profundus tendon and extensor tendon of each finger were cut apart from the level of the volar and dorsal interphalangeal joint and separated at the level of the distal interphalangeal joint. The distances from the insertion of flexor digitorum profundus tendon and extensor tendon to the volar and dorsal articular surfaces of the distal phalanx were recorded, and the insertion levels of the flexor digitorum profundus tendon and the extensor tendon at the volar and dorsal phalanx were compared. Results The distances from the articular surface to the proximal insertion point of the flexor digitorum profundus tendon for each finger were as follows: the index fingers (2.19±0.27) mm, the middle fingers (2.50±0.14) mm, the ring fingers (2.23±0.16) mm, and the little fingers (1.83±0.19) mm. The distances from the proximal extensor tendon insertion point to the articular surface for each finger were as follows: the index fingers (0.12±0.02) mm, the middle fingers (0.18±0.02) mm, the ring fingers (0.12±0.05) mm, and the little fingers (0.06±0.01) mm. The differences of each finger were statistically significant (P<0.05). The distances from the middle point of the insertion of the flexor digitorum profundus tendon to the articular surface for each finger were as follows: the index fingers (3.73±0.45) mm, the middle fingers (4.33±0.45) mm, the ring fingers (3.53±0.46) mm, and the little fingers (3.16±0.41) mm. The distances from the middle point of the insertion of the extensor tendon to the articular surface for each finger were as follows: the index fingers (1.77±0.06) mm, the middle fingers (1.76±0.20) mm, the ring fingers (1.77±0.06) mm, and the little fingers (1.47±0.10) mm. The differences of each finger were statistically significant (P<0.05). Conclusions The insertion point of the extensor tendon at the base of the terminal phalanx is much closer to the articular surface than that of the flexor digitorum profundus tendon, which provides anatomical basis for the mechanism of Seymour fracture.
Key words
Flexor digitorum profundus tendon; /
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Extensor tendon; /
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Seymour fracture; /
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Nail matrix
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