[The artery of the thumb metacarpophalangeal joint].

As a rule, a small artery passing through the palmar plate runs into the thumb metacarpophalangeal joint. Frequently, the joint vessel arises from the arteria princeps pollicis, and rarely from the arteria metacarpalis dorsalis I or from muscle branches of the arteria princeps pollicis. In 30% of our specimens we could find a third larger palmar thumb artery. To our knowledge, this vessel was not described up to now precisely. Frequently arising from the arteria princeps pollicis, it passes the whole region of the metacarpophalangeal joint of the thumb. Distally, the artery runs within the floor of the flexor pollicis longus tendon sheath. After a mean distance of 19.7 mm, the vessel passes through the wall of the tendon sheath between the A 1-pulley and the oblique pulley. This vessel anastomoses with the arteria radiopalmaris pollicis proximal to the junction of the digitopalmar arch. According to the nomenclature of anatomic variations in the forearm, we suggest to name the additional thumb vessel "Arteria mediana pollicis".