Irreducible metacarpal neck fracture caused by interposition of junctura tendinum.

Most metacarpal neck fractures can be reduced using the close reduction technique. However, if acceptable reduction cannot be achieved by closed reduction, open reduction is indicated. A 37-year-old patient had a third metacarpal neck fracture. We tried to reduce the metacarpal neck fracture by using closed reduction methods, but failed to do so. We performed open exploration and observed that the cause of failure was interposition of the junctura tendinum (JT) connecting the third and fourth extensor digitorum tendons. The JT in the third or fourth intermetacarpal space can interpose between the fragments in cases of third, fourth, or fifth metacarpal neck fractures, because the JT in the third or fourth intermetacarpal space is thick and wide (type 2 or 3). The JT in the third or fourth intermetacarpal space should be considered as a potential obstacle to the reduction in cases of irreducible metacarpal neck fractures.