Double extensor pollicis longus tendon in independent extensor compartments: a case report of an anatomical variation requiring alteration of surgical strategy

Accessory Extensor Pollicis Longus Tendon Classification Modification

Supernumerary extensor pollicis longus (EPL) and extensor indicis proprius tendons are infrequently reported. There are few case reports on more than one accessory tendon in one individual. As a result, they are not represented in previously described classifications for variations in extensors to the thumb. Elective surgery was performed on a 57-year-old right-handed female. Within the fourth compartment, two anomalous accessory tendons were present. These tendons were identified as an accessory EPL tendon and an accessory extensor indicis proprius tendon. The normal EPL tendon occupied the third compartment ulnar to Lister's tubercle, as usual. The previous classification system for anomalous EPL tendons is useful in the organization and description of thumb extensor tendon variations. However, it is not a complete representation of the anomalies identified, including the one in this report. We have proposed an additional category for this classification system to better encompass the variation in anomalous tendon anatomy.

Accessory extensor pollicis longus from the extensor digitorum: a rare case report and review of the literature

PURPOSE

Variations of the extensor pollicis longus are rare. When present, these include a separate extensor pollicis longus muscle, tendon or an intertendinous connection with nearby tendons within the deep extensor compartment of the forearm. Here, we report an extremely rare variation of an accessory extensor pollicis longus originating from the extensor digitorum.

METHODS

An unusual muscle was found during the routine dissection forearm of a 71 year-old at death male cadaver.

RESULTS

This variant muscle originated from part of the extensor digitorum muscle belly that supplies the index finger. It became tendinous and entered the third extensor compartment of the wrist before joining the ulnar side of the extensor pollicis longus tendon. Traction on the muscle belly resulted in simultaneous extension of both the thumb and the index finger.

CONCLUSION

This study documents an extremely rare extensor tendon to the thumb originating from the extensor digitorum, with a unique attachment to the normal extensor pollicis tendon. There have been minimal accounts of this variation, and the present report adds to the limited literature. Furthermore, the report suggests a new subtype, 1f, be included in the existing classification system. Surgeons should be aware of this rare variant for proper evaluation, diagnosis and surgical treatment. Further anatomical studies are needed to study the prevalence of this variant.

Accessory extensor pollicis longus: A rare tendon anomaly

This report provides a complete review of a rare anatomical variation, the accessory extensor pollicis longus (EPL) tendon and its clinical significance. We will describe a case of an asymptomatic accessory EPL that was found incidentally during surgery with a tendon located in the fourth extensor compartment. Pulling on it induced extension of the thumb interphalangeal joint. Very few cases of accessory EPL have been previously reported with various muscle origins and tendon insertions. In the literature, three symptomatic cases of accessory EPL were reported with a tendon running in a compartment other than the fourth. Although this variation is asymptomatic in most cases, knowledge of its existence might be useful in routine procedures to avoid inadvertent tendon damage, or during tendon repair.