[Closed extensor tendon injuries of the finger]

The extensor apparatus of the fingers is a complex structure. The diagram of the extensor apparatus as seen in figure 1 is in reality not so clearly structured. Closed lesions are the mallet finger, where either an avulsion of the bony insertion of the tendon occurs or where a fracture of the base of the distal phalanx with dislocation of a bone-fragment together with the tendon insertion has happened. Other closed lesions are the closed Boutonnière deformity and the avulsion of a lumbrical muscle. The mallet finger is mostly treated conservatively with a prefabricated splint holding the DIP-joint in extension or with a temporary arthrodesis with a Kirschner-wire blocking the DIP-joint in extended position. If bigger pieces of bone are extruded from the base of the terminal phalanx this fragment must be fixed operatively. Today, very fine screws are often used. Also in these cases, a temporary arthrodesis may be helpful. This treatment lasts for 7 weeks. Afterwards for another two weeks the DIP-joint should be immobilised with a Stack-splint during the night. In the Boutonnière deformity the PIP-joint is in flexion and the DIP-joint in hyperextension. The reason is a lesion of the central extensor tendon over the PIP-joint with anterior dislocation of the lateral bands of the interosseus tendon. In early cases by stretching the finger passively the lateral band will be repositioned. In these cases, a conservative treatment with a splint holding the PIP-joint in extension may be successful. This can be combined with revision and suturing of the ruptured part.(ABSTRACT TRUNCATED AT 250 WORDS)