The Interconnecting Slip: A Cadaveric Case Report on Accessory Extensor Carpi Radialis Tendon and Its Clinical Significance

Abstract

Background: Cadaveric examinations help identify rare anatomical variations of radial wrist extensors, particularly Extensor Carpi Radialis Longus and Extensor Carpi Radialis Brevis. Such variants are clinically relevant due to the restricted space of the second dorsal compartment. This accessory slip may enhance wrist extension strength but increases local friction within the already crowded compartment, potentially producing radial wrist pain resembling De Quervain’s tenosynovitis. MRI can assist in preoperative identification. The slip’s structure also makes it a viable autologous graft option for procedures such as adductor plasty or Extensor Pollicis Longus repair.

Methods: During routine dissection of a 74-yearold male cadaver, an accessory tendon slip was found originating from the Extensor Carpi Radialis Longus muscle belly, in the posterior compartment of the forearm.

Results: An accessory tendon slip was observed arising from the ECRL muscle belly. It coursed through the second dorsal compartment and inserted at the base of the third metacarpal, positioned between the normal insertions of ECR Land ECRB. The primary ECRL tendon retained its standard insertion at the second metacarpal.

Conclusion: Awareness of this anatomical variation is essential for accurate diagnosis, avoidance of intraoperative complications, and effective planning of tendon transfer or reconstructive procedures.