Treatment with Reverse Flow Vascularized Pedicle Bone Grafts

Allen Thorpe Bishop

Richard A. Berger

Indications and Contraindications

With prompt appropriate diagnosis and treatment, more than 90% of scaphoid fractures unite. Failure to diagnose acute injury, or to treat displaced scaphoid fractures operatively in a timely manner, increases the risk of nonunion (1,2). The development of scaphoid foreshortening and associated carpal instability with elapsed time contributes to the risk of nonunion (1). In addition, fractures of the proximal third heal less readily, in part secondary to operative avascularity in the proximal fragment (3).

Most scaphoid fractures that fail to heal with inlay or wedge conventional grafts probably have impaired vascularity as a contributing factor, as demonstrated by sclerosis of the proximal pole seen in radiographic study and magnetic resonance imaging (MRI), as well as absence of punctate bleeding at the time of surgery (4,5,6,7,8). The use of conventional grafts, such as the Matti-Russe volar inlay graft, may be contraindicated in the presence of an avascular fragment (9).

Vascularized bone grafts have been proposed as appropriate methods to increase the rate and frequency of healing in fractures with poor prognosis. As early as 1965, Roy-Camille (9) used the palmar tubercle of the scaphoid based on an abductor pollicis brevis muscle pedicle for this problem. In recent years, palmar distal radius grafts (10,11,12,13,14), dorsal radius grafts (14,15), and free iliac grafts (16,17) have demonstrated improved results as compared with conventional grafts in difficult circumstances. These include displaced acute fractures with small proximal fragments or bone deficiency requiring grafting, failed conventional grafts, and nonunion of proximal pole fractures, especially when associated with avascular necrosis. Inlay bone grafting, coupled with vascular bundle implantation, may be considered as an alternative (18,19). A recent experimental study has demonstrated the superiority of vascularized grafts compared with conventional grafts in healing simulated carpal fracture nonunions with an avascular segment (20).

Vascularized bone grafts are contraindicated in proximal pole fractures whose size and geometry do not allow stable placement of the graft. Fractures with associated degenerative change involving the entire scaphoid fossa or midcarpal joint require a salvage procedure rather than an attempt to achieve union. Pedicled dorsal distal radius grafts are contraindicated in skeletally immature wrists because of the risk of physeal damage. In rare cases, absence of the potential donor vessels described below may require use of alternative pedicles or even a free vascularized graft. Relative contraindications would include acute, nondisplaced scaphoid fractures, comminuted distal radius fracture, or prior surgery potentially damaging the donor area. Systemic factors (including advanced age, vascular disease, and tobacco use) may indicate the need for an alternative method.

Preoperative Planning

Physical Examination

Typical physical findings are tenderness at the level of the fracture. This may be found in the anatomic snuffbox or directly distal to Lister’s tubercle, depending on the location of the fracture. Document bilateral wrist range of motion and grip strengths and rule out concurrent pathology that may affect the outcome of planned surgical procedures.

Radiographic Study

The character of the fracture can be assessed adequately with standard x-ray views. These include posteroanterior (PA), lateral and scaphoid views, supplemented by comparison views of the contralateral wrist. Inspection of these images should include an assessment of the location and orientation of the fracture, as well as any comminution. Measure and compare PA and lateral intrascaphoid angles with the published standard and the contralateral wrist. Inspect the bone for density changes and the carpus for evidence of degenerative change and instability, including loss of carpal height and altered intercarpal and radiocarpal angles. Trispiral or computed methods provide valuable supplementary information in many cases, frequently demonstrating the deformity or arthritis to be more severe than anticipated on plain films alone. Appropriate positioning of the wrist in the computed tomography (CT) gantry is necessary to optimize imaging of the scaphoid. The goal of these studies is to quantify the deformity, including angular and translational displacement. This evaluation will provide the best means to achieve an anatomic reconstruction.

Magnet Resonance Imaging

Although controversy regarding its correlation with the presence of punctate bleeding exists, MRI remains the only preoperative or noninvasive means of evaluating bone viability. In cases in which fracture location or other imaging studies suggest an avascular proximal fragment, an MRI study before surgery is desirable.

Vascular Anatomy of the Distal Radius

A thorough understanding of the vascular anatomy of the distal radius is essential before performing this procedure (21). The radial, ulnar, anterior interosseous, and posterior interosseous arteries contribute nutrient vessels supplying the distal radius. The posterior division of the anterior interosseous artery and the radial artery form the primary sources of orthograde blood flow to the distal dorsal radius (Fig. 16-1).

The vessels directly supplying nutrient branches to the dorsal radius and ulna are described best by their relationship to the extensor compartments of the wrist and extensor retinaculum. They are considered compartmental when lying within an extensor compartment and intercompartmental when located between compartments.

Two consistent intercompartmental vessels exist. They lie superficial to the retinaculum and are described further as supraretinacular. These two vessels, the 1,2 and 2,3 intercompartmental supraretinacular arteries (ICSRA) (1,2 and 2,3 ICSRA), are located superficial to the retinaculum between their numbered compartments (Fig. 16-2). The retinaculum under these vessels is adherent to an underlying bony tubercle separating the compartments, allowing nutrient vessels to penetrate bone.

The 1,2 supraretinacular artery (1,2 ICSRA) is the most commonly used vascular pedicle for scaphoid nonunions (Fig. 16-2). It originates from the radial artery approximately 5 cm proximal to the radiocarpal joint and courses beneath the brachioradialis muscle to lie on the dorsal surface of the extensor retinaculum. Distally, it enters the anatomic snuffbox to anastomose to the radial artery, to the radiocarpal arch, or to both. It is accompanied by venae comitantes and is the smallest of the four vessels. The distal anastomosis is the ascending irrigating branch previously described by Zaidemberg et al. (15

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