During a routine anatomical dissection of 48 upper limbs from 24 fixed cadavers, variants of extrinsic extensor hand muscles, including extensor medii proprius (EMP) and extensor indicis medii communis (EIMC), were observed. EMP was found bilaterally in 1 cadaver (4.2%; 95 year old female) and unilaterally in 2 cadavers (8.3%; 74 year old male, 78 year old female), while EIMC was only seen unilaterally in 3 cadavers (12.5%). Both EMP and EIMC demonstrated a tendinous insertion deep to extensor digitorum muscle into the extensor hood of the 3rd digit. All EIMC variants shared a muscle belly with extensor indicis (EI), while EMP variants maintained individual muscle bellies. The muscle belly for all EMP variants showed proximal attachments at the middle‐ or distal‐third of the ulna. All EMP and EIMC variants received innervation from the posterior interosseous nerve. In addition to contributing to prevalence reports on anatomical variations within the dorsum of the hand, our findings of a bilateral EMP in a female cadaver represent a rare variation not previously published. These EI variants may aid in clinical settings, such as identification, surgical planning, and muscle or tendon repair.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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