Unusual pattern of the first dorsal metacarpal artery
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This report describes an unusual pattern of the first dorsal metacarpal artery (FDMA) regarding its course and termination. This FDMA had an abnormal course, passing deep to various anatomical elements related to the index finger, with unusual termination in the radial and ulnar proper palmar digital arteries feeding the second and third fingers, respectively. There is no mention of this anatomical variation in the literature. We report the possible embryological origin of this case and other variations related to the FDMA. This unusual pattern represents a new reason to consider anatomical knowledge important for surgeons whose procedures are in this area and to ensure an accurate diagnosis and safe treatment of pathologies that might engage this anatomical variation.
KeywordsFirst dorsal metacarpal artery Hand Anatomical variation Radial artery
The first dorsal metacarpal artery (FDMA) is located in the first dorsal interosseous space superficial to the first dorsal interosseous muscle (FDIM) along the axis of the second metacarpal. It arises from the radial origin before the radial artery leaves the dorsal aspect of the hand by running between both heads of the FDIM. According to several authors, this artery has many variations, including one that supplies digital collaterals for the thumb and index finger, supplying, in its path, bone, muscle, and tendon branches to surrounding structures [1, 2, 5]. The constant presence of FDMA and its branches allows construction of bone flaps and osteocutaneous pedicles, whether proximally or distally. Our aim was to present the unusual path and distribution of this FDMA, which has not been described previously in the literature.
During a routine dissection of an adult right upper limb, variations in the usual vascular contribution (regardless of sex or age) to the index finger and middle finger with their origin in the FDMA were observed in the hand. The specimen had been injected with colored elastomeric material, immersed in 10% formalin, and dissected using standard technique and 2× magnification lenses.
The FDMA had originated from the radial artery at the first interosseous space prior to passing through the fascicles of the FDIM. From its origin, it proceeded along the first commissure, resting on the FDIM, parallel to the second metacarpal near its radial edge. Once it arrived on the lateral side of the base of the index finger, it was directed inwardly in a horizontal path following the digitopalmar fold of the index finger deeply and passing deep to the flexor tendons of the index finger, the first lumbrical muscle, the radial proper palmar digital artery (PPDA) of the index finger, and the radial and ulnar proper palmar digital nerves. It then followed the distal edge of the adductor pollicis muscle until it reached the commissure between the index finger and the middle finger. At this point, it divided into the radial and ulnar PPDAs, respectively, for these two fingers (Fig. 1a, b).
The superficial palmar arch (SPA) was incomplete. The ulnar artery branched into the ulnar PPDA of the fifth finger and the common palmar digital artery (CPDA) to supply the fourth interosseous space, which then became the radial PPDA (supplying the fifth finger) and the ulnar PPDA (supplying the fourth finger). The ulnar artery then continued its course and split into two other branches: an incomplete CPDA that became the palmar metacarpal artery (PMA) of the third interosseous space and another branch that ended up joining the FDMA before its entrance into the interdigital space between the second and third fingers. This anastomotic branch gave rise to an artery that joined with the radial PPDA of the index finger. The ulnar and radial PPDAs of the third and fourth fingers depended on the third palmar metacarpal artery (PMA). There was not a second PMA (Fig. 1c, d).
The literature concerning FDMA does not mention a variation such as the one that appeared in this case [1, 2, 3, 5, 6, 7, 8, 10, 12]. In the specimen studied, the artery followed an unusual path, passing deep to various anatomical elements related to the index finger and giving off two unusual final branches.
Regarding the presence and origin of the FDMA, there was no difference from the reports of Dauphin and Casoli  and Earley , who found that the FDMA originated from the radial artery in 100% of cases. Earley  and Bianchi  described three and two types of FDMA, respectively: (1) superficial, parallel to the second metacarpal bone (but distant from it) and superficial to the FDIM (75%); (2) deep relative to the muscle, becoming superficial distally at the level of the second metacarpal neck (15%); (3) combined superficial and deep dispositions, where these vessels could be a duplication of the FDMA or the same vessel providing two branches (10%) . In the current case, the course of the artery was superficial throughout.
Adachi reported variations in the FDMA, but mostly in regard to the distribution of the collateral branches supplying the thumb and index finger. Its origin varied, but it could have originated from the anterior interosseous artery because of the persistence of a rudimentary radial artery . There was no description about variations regarding the final course of the FDMA, as in our case.
This case shows that there is a real challenge in determining the embryological origin. This strange disposition could be because of modified embryological organization in stage IV, described by Singer (Fig. 2), which occurs in embryos of 21 mm. Here, the superficial brachial artery is developed in the axillary region and crosses the medial surface of the arm to reach the forearm. It then goes to the posterior aspect to reach the wrist, where it splits into the carpal branches that supply the back of the thumb and the index finger . This interpretation is supported by the superficial disposition of the FDMA. It has been established that the absence of proper palmar SPA collaterals typically indicates that the deep palmar arch compensates by establishing an anastomosis between the PMA and PPDA, which do not originate from the SPA [3, 5].
In the present case, the FDMA is the vessel that appears to compensate for the SPA-derived deficit. Because of its termination, however, it could be stated that it makes up for the absence of the second PMA, which is also not present. Based on our own experience and that of others, the FDMA compensates for the missing contribution of the SPA, ending as the second PMA and even anastomosing with the PPDA, as is usually seen when this artery makes up for a lack of supply from the SPA. As classically described, in those cases, the radial PPDA of the index finger and the radial and ulnar PPDA of the thumb originate from the first palmar metacarpal artery (the “princeps pollicis” artery) [3, 5, 8].
We believe that this abnormality should be taken into account because, in addition to its anomalous course, which is unexpected compared with the usual anatomical relations in that area of the hand, the arteries that supplied the FDMA could be considered terminal branches for the index and middle fingers because of the absence of the metacarpal interosseous artery of the second space.
Thus, the vascular territory could be affected in the following situations:
when releasing a Dupuytren’s contracture that is affecting the radial side of the hand, the first dorsal space, and the index finger (although rare, it could occur) ;
when there are wounds of the palm of the hand with injured tendons of flexor muscles and the presence of scar retractions in the area, requiring the release of the carpus for repairing deferred or untreated injuries ;
when index pollicization is needed, especially in cases of hypoplastic thumb, with the possibility of damage to the vessel by opening the second interosseous space to separate the index and middle fingers [4, 16].
In these situations, the blood supply to the index and middle fingers would depend on the development of radial and ulnar PPDAs, respectively.
Based on the case presented, it is thought that the disposition of the FDMA is comparable to that of the PMA because of its distribution. There was an absence of the proper digital palmar branches from the SPA and the second PMA, acting the FDMA of the case that we reported as a compensation of this absence. Fortunately, the presence of this arterial pattern is exceptional. Perhaps surgeons should take this anatomical variation into account in the cases described because the vascular disorders that may accompany it have an effect on the development of the hand.
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Conflict of interest
There is no conflict of interest.
- 1.Adachi B (1928) Das arteriensystem der Japaner. Marusen Co., KyotoGoogle Scholar
- 7.Dhar P, Lall K (2008) An atypical anatomical variation of palmar vascular pattern. Singap Med J 49:e245–e249Google Scholar
- 15.Strickland JW, Graham TJ (2006) Orthopedic Surgery Techniques. Hand. Marban Libros, MadridGoogle Scholar
- 16.Vergara Amador EM (2008) Hipoplasia of the thumb. Clinical presentation and reconstruction. Rev Fac Med (Bogotá) 56:33–42Google Scholar