A total of 192 embalmed cadavers were examined in order to present a detailed study of arterial variations in the upper limb and a meta-analysis of them. The variable terminology previously used was unified into a homogenous and complete classification, with 12 categories covering all the previously reported variant patterns of the arm and forearm.

A total of 112 human embryos (224 upper limbs) between stages 12 and 23 of development were examined. It was observed that formation of the arterial system in the upper limb takes place as a dual process. An initial capillary plexus appears from the dorsal aorta during stage 12 and develops at the same rate as the limb. At stage 13, the capillary plexus begins a maturation process involving the enlargement and differentiation of selected parts. This remodelling process starts in the aorta and continues in a proximal to distal sequence. By stage 15 the differentiation has reached the subclavian and axillary arteries, by stage 17 it has reached the brachial artery as far as the elbow, by stage 18 it has reached the forearm arteries except for the distal part of the radial, and finally by stage 21 the whole arterial pattern is present in its definitive morphology. This differentiation process parallels the development of the skeletal system chronologically. A number of arterial variations were observed, and classified as follows : superficial brachial (7n7 %), accessory brachial (0n6 %), brachioradial (14 %), superficial brachioulnar (4n7 %), superficial brachioulnoradial (0n7%), palmar pattern of the median (18n7 %) and superficial brachiomedian (0n7 %) arteries. They were observed in embryos belonging to stages 17-23 and were not related to a specific stage of development. Statistical comparison with the rates of variations reported in adults did not show significant differences. It is suggested that the variations arise through the persistence, enlargement and differentiation of parts of the initial network which would normally remain as capillaries or even regress.

Variations in connections between the musculocutaneous and median nerves in the arm are not as uncommon as was once thought. This opinion led us to perform a study in 138 cadavers (66 male, 72 female). These variations were seen in 64 cadavers (46.4%), 9 bilaterally and 55 unilaterally (26 right and 29 left); in total, therefore, variations were observed in 73 out of 276 arms (26.4%), 42 male and 31 female. No statistically significant differences by gender and side were observed. We classify the variations in three main patterns: Pattern 1, fusion of both nerves (14 arms, 19.2%); Pattern 2, presence of one supplementary branch between both nerves (53 arms, 72.6%); and Pattern 3, two branches (5 arms, 6.8%). Pattern 2 was further subdivided into a sub-group 2a when a single root from the musculocutaneous nerve contributed to the connection (51 arms, 69.9%), and 2b when there were two roots from the musculocutaneous nerve (2 arms, 2.7%). A combination of Patterns 1 and 2a was observed in one case (1.4%). Further variations are described, published classification systems are reviewed and a meta-analysis of previous results is presented. An overall incidence of 33% of variant arms was observed. Of these variant arms, Pattern 1 represented 13.1%, Pattern 2 represented 75.4%, and Pattern 3, 8.5%, similar to our figures.

Research within the anatomical sciences often relies on human cadaveric tissues. Without the good will of these donors who allow us to use their bodies to push

In 1813 Gantzer described 2 accessory muscles in the human forearm which bear his name (Wood, 1868; Macalister, 1875; Testut, 1884; Le Double, 1897). The more frequent of the 2 accessory muscles or ‘accessorius ad pollicem’ was found to arise from the coronoid process of the ulna, coursing distally to attach into the flexor pollicis longus muscle (flexor pollicis longus accessory head, FPLah). The less frequently observed or ‘accessorius ad flexorem profundum digitorum’ was again found to arise from the coronoid process and course to join into the flexor digitorum profundus (flexor digitorum profundus accessory head, FDPah). Since their initial description, they have been examined in further detail by a number of authors (Wood, 1868; Macalister, 1875; Le Double, 1897; Dykes & Anson, 1944; Mangini, 1960; Malhotra et al. 1982; Dellon & McKinnon, 1987; Kida, 1988). These studies, most of them focusing on the FPLah, all show different results of prevalence, origin, insertion, relations and nerve supply. We undertook this study with the aim of providing a more accurate account of the detailed morphology of both accessory muscles because of the above‐mentioned inconsistent anatomical descriptions and the lack of information as to important aspects such as vascular supply, morphology (shape and length) and the coexistence of both accessory heads.