Dorsal Radius

The distal dorsal radius has a robust and consistent blood supply provided by a series of longitudinal extraosseous vessels originating from the anterior interosseous and radial arteries. The anterior interosseous artery divides into anterior and posterior divisions proximal to the distal radioulnar (DRU) joint. The primary source of orthograde blood flow to the distal dorsal radius is provided by the posterior division, together with the radial artery. They also supply nutrition to soft tissues, creating the possibility of raising a composite pedicled flap that includes the posterior interosseous nerve, skin, and muscle. ⁴

Branches from the major longitudinal forearm vessels ultimately supply nutrient arteries to the distal dorsal radius. The dorsal vessels are best described by their location in relationship to the extensor compartments of the wrist and the extensor retinaculum. They provide a consistent group of nutrient arteries to the distal radius. Of importance, all have distal anastomotic connections. Two of the vessels are superficial in location, lying on the dorsal surface of the extensor retinaculum between the 1st and 2nd and the 2nd and 3rd dorsal compartments. At these locations, the retinaculum is adherent to an underlying bony tubercle separating their respective compartments, allowing nutrient vessels to penetrate bone. Because of their location, they have been named the 1,2 and 2,3 intercompartmental supraretinacular arteries (1,2 and 2,3 ICSRA) ⁵ (▶Fig. 21.1).

Two deep vessels also provide nutrient vessels to the dorsal distal radius. They lie on the surface of the radius in the floor or against the wall of the 4th and 5th dorsal compartments. They are consequently named the 4th and 5th extensor compartment arteries (4th and 5th ECA) ⁵ (▶Fig. 21.1).

The 1,2 ICSRA originates from the radial artery approximately 5 cm proximal to the radiocarpal joint, passing beneath the brachioradialis muscle and tendon to lie on the dorsal surface of the extensor retinaculum. Distally, it passes beneath the tendons of the first extensor compartment to enter the anatomic snuffbox and anastomose to the radial artery in most cases or occasionally to a radial branch supplying the scaphoid. ⁶ This distal anastomotic connection is the “ascending irrigating branch” described previously. ⁴ It is the smallest the four vessels (mean internal diameter of 0.30 mm). Like all the vessels, it is accompanied by venae comitantes ⁷ (▶Fig. 21.1, ▶Fig. 21.2, and ▶Fig. 21.3; ▶Table 21.1 and ▶Table 21.2).

Its position superficial to the retinaculum and directly on the bony tubercle between the first and second extensor compartments makes its dissection and use as a vascularized pedicled graft to the scaphoid fairly straight forward. However, its arc of rotation is short, its nutrient artery branches are small in number and caliber, and the vessel itself is occasionally absent. These factors may significantly limit its usefulness in carpal bones other than the scaphoid and, of course, in any patient if absent. In some individuals, a more proximal branch of the 1,2 ICSRA enters the floor of the 2nd compartment, ending as a large nutrient vessel (2nd EC branch of the 1,2 ICSRA). A graft centered on this branch results in a pedicle long enough to reach the lunate. ⁵

The 2,3 ICSRA originates proximally from the anterior interosseous artery or the posterior division of the anterior interosseous artery (▶Fig. 21.1 and ▶Fig. 21.4; ▶Table 21.1 and ▶Table 21.2). It runs superficial to the extensor retinaculum directly on the dorsal radial tubercle (Lister’s tubercle) to anastomose with the dorsal intercarpal arch (dICa) and, in some cases, the dorsal radiocarpal arch (dRCa) and/or the 4th ECA. It has a mean internal diameter of 0.35 mm. The number, location, and size of its nutrient branches are shown in ▶Table 21.2. These nutrient branches often penetrate deep into cancellous bone. One large proximal branch enters the radius in the floor of the 2nd extensor compartment (2nd EC branch of the 2,3 ICSRA). Like the 1,2 ICSRA, the 2,3 ICSRA may be based as a retrograde pedicle for a vascularized bone graft. ⁵ that its mid axial dorsal position provides an arc of rotation that may reach the entire proximal carpal row, the pedicle overlies the wrist joint capsule at the site of most capsulotomy incisions. Its dissection and mobilization, which must be done prior to inspection of the carpus, is more difficult than for the more marginally located 1,2 ICSRA and 5th ECA. Therefore, the use of this pedicle has been largely abandoned in most clinical practice.

The 4th ECA (▶Fig. 21.1 and ▶Fig. 21.3) lies directly adjacent to the posterior interosseous nerve on the radial aspect of the 4th extensor compartment. In a minority of cases, the vessel may be found within the 3,4 septum for most of its course. Proximally, this artery originates from the posterior division of the anterior interosseous artery or its 5th extensor compartment branch. It anastomoses distal to the radius with the dICa and, in most cases, to the dRCa. Connections to the neighboring 2,3 ICSRA and/or the 5th ECA are common. It has a mean internal diameter of 0.38 mm. The 4th ECA is the source of numerous nutrient vessels to the floor of the 4th compartment that frequently penetrate cancellous bone (▶Table 21.1). The vessels entering more distally tend to supply primarily cortical bone, whereas those more proximal are more likely to penetrate cancellous bone. ⁵

The 5th ECA is generally the largest of all the dorsal vessels (mean 0.49 mm internal diameter) (▶Fig. 21.1 and ▶Fig. 21.4; ▶Table 21.1). It is located in the radial floor of the 5th extensor compartment, passing mostly through the 4,5 septum in one-third of specimens. ⁵ This vessel is supplied proximally by the posterior division of the anterior interosseous artery and anastomoses distally with the dICa. It may also make distal connections with the 4th ECA, the dRCa, the 2,3 ICSRA, and/or the oblique dorsal artery of the distal ulna. Only 39% of the 5th ECAs in the study of Sheetz et al had a branch that supplied 1 or 2 nutrient vessels to the floor of the 4th compartment (4th EC branch of 5th ECA). ⁵ It is therefore most useful as a large conduit of retrograde flow from the intercarpal arch to other vessels with more consistent nutrient branches. Its large diameter and multiple anastomoses allow creation of a vascular pedicle that can reach almost anywhere in the hand, for example, when retrograde flow through the 5th ECA supplies orthograde (proximal to distal) blood supply to a radial bone graft centered over the 4th ECA (5 + 4 ECA pedicle). Experimental studies in the canine distal radius have demonstrated that similar reverse-flow pedicle bone grafts have measurable flow immediately after elevation and have marked hyperemia when reevaluated after 2 weeks. ^{8 , 9}

A series of arches across the dorsum of the hand and wrist provide distal anastomoses with these intercompartmental and compartmental arteries. These include the dICa, dRCa, and dorsal supraretinacular arch (dSRa). The dICa contributes blood supply to the distal ulna and radius only indirectly, through connecting arteries. It is an important part of several potential grafts because of its anastomotic connections. The arch can be used as a source of retrograde arterial flow allowing proximal vessel ligation and graft mobilization. The dRCa contributes significantly to the dorsal distal radius via small nutrient arteries. These nutrient branches enter bone just proximal to the radiocarpal joint and proceed perpendicularly to supply cancellous bone in the extreme distal end of the metaphysis. Its close proximity to the radius and its location on or deep to the superficial joint capsule limits its potential use as a source of retrograde arterial flow due to a short arc of rotation and difficult dissection. The dSRa provides anastomoses between the arteries running parallel to the radial and ulnar diaphyses. It is not a single artery but rather is an anastomotic network of small vessels connecting the dorsal arteries. Because of its small caliber vessels, it is not of use in providing retrograde bone graft pedicle blood flow ⁵ (▶Fig. 21.1, ▶Fig. 21.2, ▶Fig. 21.3, ▶Fig. 21.4, and ▶Fig. 21.5; ▶Table 21.1 and ▶Table 21.2).

In the passage on carpal extraosseous vascularity, the dICa and dRCa is described in further detail.