The extensor indicis et medii communis.

The aim of this study was to examine the existence of the extensor indicis et medii communis in detail. Thirty-one randomly selected adult cadavers (62 upper extremities) were examined for this project (22 males and 9 females between the ages 38 and 87). The muscle was observed in 3 of 62 hands, an incidence of 4.8%. One was in the right and the other two were in the left hands. Mean length and width of the muscle belly were 4.5 +/- 0.8 and 0.8 +/- 0.3 mm, respectively. Although the muscle did not have a junctura tendinum attachment between its two tendons, in one hand, the tendon to the index finger gave a thin slip to the tendon of the extensor digitorum communis for the same finger. Knowledge of variant muscle may be important when one is assessing the traumatized or diseased hand.