Rare Bilateral Variation of the Extensor Indicis Tendon in two Female Cadavers

Abstract

In this case study, we discuss the observed anatomical variant of bilateral extensor indicis medii communis (EIMC) muscle. During a routine anatomical dissection of 48 upper limbs from 24 cadavers, two female cadavers (75 and 79 years of age) demonstrated bilateral EIMC (8.3%), while one male cadaver (86 years of age) demonstrated unilateral EIMC (4.2%). The noted EIMC shared a muscle belly with the extensor indicis, but had a distal attachment in the extensor hood of the third digit. This is a rare instance of a bilateral presentation of the extensor indicis medii communis muscle. There has been a limited number of cases in which a bilateral EIMC was discovered; however, such findings have been limited to one cadaver and at a lower frequency. This finding may demonstrate that bilateral EIMC may not be as rare as previously thought. Ultimately due to its infrequency, awareness of this variation may help physicians avoid improper muscle recognition when visualizing the area during procedures regarding the dorsum of the hand, as well as providing a possible site of tendon harvesting.