The distal dorsal intermetacarpal ligament: characterization of an overlooked structure-an anatomical study of 25 hands.

PURPOSE: Exhaustive literature is available on the metacarpophalangeal joints of the long fingers, but the dorsal ligamentous structure overlaying the interosseous muscles and joining the metacarpal heads of the long fingers remains to be fully characterized. Previously, our surgical hand team observed a non-classically reported structure connecting the metacarpal heads of the long fingers, in the dorsal part of the intermetacarpal spaces. Therefore, the aim of this anatomical study was to characterize this ligamentous structure in terms of size, insertions, and anatomical position.

METHODS: Twenty-five hands were dissected for a total of 75 long finger intermetacarpal spaces. A ligamentous structure was exposed after cellular tissue excision and dorsal superficial fascia opening. The length and thickness were measured and anatomical position and insertions were studied. Histological analysis was performed on five specimens and ultrasound analysis in one healthy subject.

RESULTS: All 25 dissections revealed a dorsal ligamentous structure, hereafter named distal dorsal intermetacarpal ligament, which was inserted in the lateral tubercle of each adjacent long finger metacarpal head. This distal dorsal intermetacarpal ligament surrounded interosseous tendons. It was more proximal compared to oblique and transversal interosseous muscle fibers. Histological analysis confirmed the ligamentous nature of the structure. Ultrasound analysis showed that this structure was well identified under the dorsal aspect of the hand.

CONCLUSION: All dissections revealed a tense ligamentous structure between each metacarpal head of the long fingers. This was a constant structure meeting the definition of a ligament. The distal dorsal intermetacarpal ligament seems to stabilize the metacarpal heads at the second and fourth spaces by limiting hyperabduction.