A Technique for Accurately Identifying and Harvesting the Extensor Indicis Proprius for Tendon Transfer

The extensor indicis proprius (EIP) is commonly used as a donor for tendon transfers. It normally inserts on the ulnar aspect of the extensor hood with the extensor digitorum communis (EDC) to the index finger inserting on the radial aspect. Anatomical studies have reported variations in EIP anatomy with a 1%-1.5% incidence of EIP insertion onto the radial aspect of the extensor hood. In our experience with 60 EIP transfers over 18 years, we found the EIP to insert onto the radial aspect of the extensor hood in three patients (5%). This is higher than what has been reported in the literature. We confirm the EDC by identifying the juncturae tendinae connecting the index and long finger EDC. We review relevant literature and suggest technical tips to avoid accidentally harvesting the wrong tendon. Level of Evidence: Level V (Therapeutic).