Supernumerary extensor tendon to the thumb: a report on a rare anatomic variation

Area of Science:

• Anatomy
• Human Anatomy
• Surgical Anatomy

Background:

• Anatomical variations in the hand can impact surgical procedures.
• Understanding rare tendon anomalies is crucial for accurate diagnosis and treatment.
• The extensor tendons of the thumb and index finger are complex structures.

Observation:

• A supernumerary extensor tendon to the left thumb was identified in a cadaver.
• This anomalous tendon originated from a bipinnate extensor indicis proprius muscle.
• The tendon traversed the fourth synovial compartment to join the extensor pollicis longus.

Findings:

• The observed tendon variation is exceptionally rare, with only a few cases documented since 1897.
• Fusion occurred at the midshaft of the first metacarpal bone.
• This represents a significant deviation from typical hand anatomy.

Implications:

• This anatomical rarity may have clinical implications for conditions affecting the thumb and index finger.
• Awareness of such variations is important for hand surgeons and anatomists.
• Further investigation into the functional and clinical impact of this variation is warranted.