Variations of the abductor pollicis longus tendon: an anatomic study

This study was performed to investigate the variations, dimensions and attachment of the abductor pollicis longus (APL) tendon. Fifty upper limbs of adult cadavers were dissected in the Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia. Variations of APL tendon and its way of insertion were observed;its length, width and thickness were also measured and statistically analysed. No single-tendon-APL was found in all the examined upper limbs. The APL exhibited 2-6 tendons in all the cases. Tendons of APL were classified into medial and lateral. The lateral was considered as the main APL tendon, which was inserted into the base of the first metacarpal bone. The medial tendons were regarded as accessory slips and were inserted most commonly into the base of the first metacarpalbone; 80% on its anterolateral surface vs. 20% on the lateral one. The rest of the medial slips extended to trapezium, abductor pollicis brevis, thenar fascia, capsule of first carpometacarpal joint and opponens pollicis, with a frequency of 80%,60%, 40%, 30% and 20%, respectively. Transverse tendinous fibres were noted connecting the various slips of the APL tendons. No significant difference was recorded between the length of the main APL tendon and its accessory tendons, however, a highly significant difference was found between their thicknesses as well as their widths. Thus it is verified that the lateral tendon of APL is the main,whereas the medial tendons are accessory. The observations regarding dimensions and variations of the APL and their accessory tendons may prove useful to surgeons as a source of grafting material.