Variation in the Index Finger Vascular Pedicle in a Case of Congenital Hypoplasia of the Thumb

Sir,

An 11-month-old male child with bilateral congenital thumb hypoplasia (left: type IV; right: type II as per Blauth's classification[1]) was scheduled for index finger pollicization procedure on the left hand. The child also had a preaxial polydactylous thumb in addition to the pouce flottant ([Fig. 1A–C]). Right hand thumb opposition was augmented with Huber's abductor digiti minimi transfer,[1] at 8 months of age. On the left side the polydactylous preaxial digit was amputated first preserving the skin flaps for later use. Buck–Gramcko's technique was used to mark the skin incisions for pollicization, and the thin dermal flaps were raised preserving the lipovenous plane as described by Thatte et al in 2013.[1] Thereafter, the two vascular pedicles to the index finger were dissected on the palmar side, namely the radial and ulnar pedicles. On dissecting the pedicles, the index finger radial pedicle was found to be in the usual plane but arising from the radial artery contributing to the superficial palmar arch. The ulnar pedicle was not immediately seen in the plane under the superficial palmar aponeurosis. It required division of the deep fascia posterior to the flexors to come in view in a more dorsal plane, the origin of the pedicle was found to be arising from the deep palmar arch. The pedicle was dissected free along its length by ligation of its tiny side branches and the radial pedicle to the middle finger ([Fig. 2A, B]). Remaining part of the surgery went as per the technique described[1] and the neo-thumb remained pink and warm, postoperatively ([Fig. 2C]).

Fig. 1 Preoperative clinical picture of the left hand thumb anomaly (A, B) and X-ray (C) of both hands with congenital thumb anomalies.

Fig. 2 Intraoperative pictures. (A) Anomalous radial pedicle and ulnar pedicle with its origin going deep in to the palm. (B) Index finger ulnar pedicle going posterior to the deep fascia. (C) The postoperative picture of the pollicized index finger showing good vascularity.

Commonly, the ulnar artery courses through the Guyon's canal, gives off a deep palmar branch, which contributes to the deep palmar arch (formed predominantly by the radial artery), and then continues as the superficial palmar arch; that lies superficial to the flexor tendons. At its termination on the radial side of the hand, it anastomoses with the superficial palmar branch of the radial artery to form the superficial palmar arch which crosses the palm 1 to 2 cm distal to the distal edge of the transverse carpal ligament.[2] From this arch, arises the three common digital arteries. Each is joined by a corresponding palmar metacarpal artery from the deep palmar arch and divides into two proper palmar digital arteries that supply the medial four fingers. The superficial palmar arch is subject to several variations, with a complete arch seen in 42% cases only.[2] In an incomplete arch (seen in 58% cases), the common digital arteries may arise from ulnar, median, or radial components.[2] The deep palmar arch is the continuation of the dorsal branch of the radial artery.[2] The radial artery enters the palm through the first interosseous space and crosses the palm to form the deep palmar arch, lying deep to the flexor tendons. It gives rise to the princeps pollicis artery that supplies the thumb, radial indicis artery for the radial side of the index finger, and a superficial palmar branch that completes the superficial arch[2] ([Fig. 3A]–[C]).

Fig. 3 Schematic illustrations. (A) Normal human hand vasculature. (B) Anomalous vessels described in our case (Key: 1, 2, 3, 4: common digital branches; 5: princeps pollicis branch, 6: radial indicis branch; 7, 8, 9: deep metacarpal branches; 10: radial artery, 11: radial contribution to superficial palmar arch; 12: ulnar artery; 13: ulnar contribution to deep palmar arch). (C) Anomaly illustration—a cross-sectional view at metacarpophalangeal joint level (M: metacarpal head).

In our case of thumb hypoplasia, contrary to common anatomy, the index finger ulnar pedicle arose from the deep palmar arch and the radial pedicle was from the superficial arch ([Fig. 3B, C]). Buck–Gramcko in 1991 had reported a case of complete necrosis of the pollicized index finger owing to the vascular anomaly, wherein a short metacarpal artery was the only source of blood supply to the index finger.[3] Kaneshiro and Hidaka in 2010 had reported a case of variation in origin of the first common digital artery from the deep arch, which led to difficulty in transposition of the index finger for a hypoplastic thumb.[4] Madhyastha et al in 2011 cadaveric study, had observed the variation wherein the superficial palmar arch gave rise to the radial pedicle of the index finger, similar to our observation.[5] Hashem et al in their cadaveric study on human hands in 2018, had reported the findings of an atypical vessel, from the deep palmar arch, replacing the 2nd web space common digital artery in 4 out of 33 specimens. This atypical vessel also gave off the arteria radialis indices branch. Thereby, the authors stressed upon the need for careful systematic approach to the pedicles and to dissect from known to unknown, which is distal to proximal direction.[6]

The variation in our case emphasizes the importance and need to retrogradely dissect the pedicles, toward their origin. The importance and simplicity of this approach was introduced by Wei et al,[7] in cases of second toe transfer to hand. The retrograde pedicle dissection allows the surgeon to determine the dominance of dorsal versus plantar system and also facilitates the harvest of pedicle of adequate length as per the recipient site requirement.

Familiarity with the variations in the vascular patterns resulting from many developmental variations remains a vital issue for personnel engaged in reconstructive hand surgery. The knowledge of the variations can facilitate surgeons to execute the reconstruction procedure safely. We present such a variation to add to the body of work in the literature.

Publication History

Article published online:
06 June 2022

• References

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