# A Unique Bilateral Variation of the Extensor Carpi Radialis Longus: A Case Report

## TL;DR

A rare anatomical variation involving the extensor carpi radialis muscles was found in a cadaver, which could impact surgical procedures.

## Contribution

The paper reports a novel bilateral anatomical variation involving the extensor carpi radialis longus and agenesis of the extensor carpi radialis brevis.

## Key findings

- An accessory tendon from the ECRL inserted on the third metacarpal, typical of the ECRB.
- Bilateral absence of the ECRB was observed in the cadaver.
- No similar variations were found in 32 additional forearms examined.

## Abstract

A novel combination of variations involving the extensor carpi radialis (ECR) muscle group was observed bilaterally in a 75-year-old female cadaver during routine dissection. An accessory tendon was observed arising from the extensor carpi radialis longus (ECRL) and traveling with the primary tendon through the second compartment of the extensor retinaculum. While the primary tendon inserted on the base of the second metacarpal, as is typical of ECRL, the accessory tendon inserted on the base of the third metacarpal. This insertion is typical of the extensor carpi radialis brevis (ECRB) muscle. Additionally, bilateral agenesis of the ECRB was reported. Thirty-two additional forearms were assessed for similar variations, with none being observed. This combination of variations adds to the literature regarding the ECR muscle group, while also being of interest to clinicians, specifically regarding tendon reconstructive procedures as well as accessing the distal radial artery via the anatomical snuffbox.