Anatomy of the extensor tendons of the fingers: variations and multiplicity

The extensor tendons to the fingers were dissected in 43 adult hands. The most common distribution pattern of the extensor tendons of the fingers was: (1) a single extensor indicis proprius (EIP) tendon that inserted ulnar to the extensor digitorum communis (EDC) of the index; (2) a single EDC-index; (3) a single EDC-long; (4) a double EDC-ring; (5) an absent EDC-small; and (5) a double extensor digiti quinti (EDQ) with a double insertion. Frequent variations included, a double EIP tendon; a double or triple EDC-long tendon; a single or triple EDC-ring tendon; and a single or double EDC-small tendon. The extensor medii proprius was noted in 5 specimens. Increased multiplicity of any tendon was not associated with multiplicity of any other tendon, but was associated with a thinner (type 1) junctura tendinum between EDC-index and EDC-long. An absent EDC-small was related to an increased incidence of a double EDC-ring and the presence of a thick type 3 junctura tendinum between the EDC-ring and the EDQ or dorsal aponeurosis of the small finger. Knowledge of potential tendon multiplicity and variations may help in the identification and repair of these structures.