Multiple tendons for abductor pollicis longus in the first dorsal compartment and variation in their insertion pattern: Anatomical and clinical relevance

Precession in the action of the thumb is an evolutionary modification for various skilled movements of the human hand. The fine and specialized movements of the thumb is depends on the co-ordination of the intrinsic and extrinsic muscles such as flexor, extensor, adductor and abductor group of muscles. Here in this study we made an attempt to evaluate the possible variations in the number of tendons of the abductor pollicis longus muscle that are passing through the first dorsal compartment and variability in their distal attachments. For this purpose we studied seventy three (32 males and 12 females) formalin fixed cadaveric upper limbs (35 right and 38 left) in the Department of Anatomy, Kasturba Medical College, Manipal. Our result show that, the presence of two tendons for APL was found in 47.95% and presence of five and 6 tendons were found in about 1.36% of the cases. In majority of the cases, the tendons were found to attach to the base of 1st metacarpal bone. In only one case, tendon was found to attached to the base of the proximal phalanx of the thumb via small extension. Knowledge of these multiple tendons and variation in their distal attachments of the APL are essential in the treatment of de Qurvain's stenosing tenosinovitis, in interposition arthroplasty, tendon transfer, tendon translocation and ligament reconstruction in arthrosis.