Variant of the extensor pollicis tertius: a case report on a unique extensor muscle to the thumb.

Variations on muscular and tendinous connections of the hand occur frequently in the human population and are often discovered during routine surgical procedures and cadaveric dissections. A knowledge of such anomalies is important to the physician in order to avoid unintentional damage to healthy tendons during surgical procedures. In addition, accessory tendons have the potential to be used in the repair or replacement of damaged tendons through surgical transfer or transplantation. Here we describe a unique variant of the extensor pollicis tertius muscle that has its origin at the proximal end of the extensor indicis muscle and inserts on the tendon of the extensor pollicis longus at the proximal shaft of the proximal phalanx of the thumb.