Dorsal Capsular-Based Vascularized Distal Radius Graft for Scaphoid Nonunion

Fig. 14.1

Anteroposterior (AP) radiograph of the right wrist showing a nonunion of the proximal pole of the scaphoid. (Published with kind permission from ©Loukia K. Papatheodorou and Dean G. Sotereanos, 2015. All Rights Reserved)

Fig. 14.2

T1 coronal view of the right wrist on MRI scan indicating avascular necrosis of the proximal fragment of the scaphoid. (Published with kind permission from ©Loukia K. Papatheodorou and Dean G. Sotereanos, 2015. All Rights Reserved)

Management Options

Scaphoid proximal pole fractures are more prone to nonunion than the more distal fractures because of the tenuous vascularity of the proximal part of the scaphoid, due to the retrograde interosseous blood supply of the scaphoid [1] . Moreover, the proximal pole of the scaphoid is most susceptible to avascular necrosis, which further impairs healing [2]. Treatment of proximal pole scaphoid nonunions with evidence of avascular necrosis is a challenging problem. The main complication of treatment is persistent nonunion. Preoperative risk factors for nonunion include smoking, history of previous surgical procedures, the presence of humpback deformity, or carpal collapse. If a scaphoid nonunion is left untreated, the wrist often undergoes progressive degenerative changes culminating in scaphoid nonunion advanced collapse .

Several treatment options have been proposed for the management of scaphoid proximal pole nonunions accompanied by avascular necrosis, including excision of the scaphoid proximal pole, open reduction and internal fixation with or without nonvascularized bone graft, and vascularized bone graft . Although the reported union rate with the use of nonvascularized bone grafts ranges from 80 to 94 %, the rate drops to 47 % in the presence of avascular necrosis of the proximal pole [3, 4] . Vascularized bone grafts have demonstrated superior biologic and mechanical properties, improving the viability of the scaphoid proximal pole and leading to a more favorable outcome and a higher union rate (88–91 %) than conventional bone grafts [3, 4]. The choice of vascularized bone graft depends on the location and the deformity of the scaphoid nonunion .

Management Chosen

For this patient with a scaphoid proximal pole nonunion accompanied by avascular necrosis but without humpback deformity and without carpal collapse, we utilized a capsular-based vascularized bone graft from the dorsal distal radius. This graft is nourished by the fourth extensor compartment artery, allowing easy access to the scaphoid proximal pole with a short arc of rotation minimizing the risk of nutrient vessel kinking [5, 6] .

Surgical Technique

The procedure is performed under general anesthesia, tourniquet control, and loupe magnification. Regional anesthesia can also be applied. A 4-cm straight dorsal incision centered just ulnar to the Lister’s tubercle is performed. Dissection is carried through the subcutaneous tissues. The extensor retinaculum of the fourth dorsal compartment is partially released to expose the wrist capsule and the distal radius. The extensor pollicis longus tendon is identified and retracted radially, and the extensor digitorum communis tendons are retracted ulnarly .

Next, the capsular-based vascularized distal radius graft is outlined with a skin marker on the dorsal wrist capsule. The flap is trapezoidal in shape with the length approximately 2 cm and is widened from 1 cm at the radial bone block to 1.5 cm at its metacarpal base (Fig. 14.3). The capsular flap is outlined sharply with a knife. The bone graft is harvested from the distal aspect of the dorsal radius just ulnar and distal to Lister’s tubercle sized approximately 1 × 1 cm including the dorsal ridge of the distal radius (Fig. 14.3). The bone graft is outlined on the distal radius cortex with multiple drill holes by using a 1.0-mm side-cutting drill bit. The graft is elevated with a thin osteotome, with care taken to maintain 2–3 mm of the distal radius cortex intact to minimize the risk of propagation onto the articular cartilage of the radiocarpal joint. The depth of the bone block is approximately 7 mm. The capsular flap is elevated along with the bone graft from the underlying tissues in a proximal-to-distal direction with care to prevent detachment of the dorsal scapholunate ligament .

Fig. 14.3

Schematic a and operative view b of the dorsal capsular-based vascularized distal radius graft. The capsular graft is outlined with red dotted line, and the bone graft is marked with black color. (Published with kind permission from ©Loukia K. Papatheodorou and Dean G. Sotereanos, 2015. All Rights Reserved)

Once the flap was elevated, attention is directed toward the scaphoid. The scaphoid proximal pole nonunion site is identified by flexing the wrist. The cartilage shell in this patient was not grossly disrupted, and the nonunion site was not violated. Fixation of the nonunion was performed under fluoroscopic control. Two 1-mm smooth Kirschner wires were inserted from the proximal pole of the scaphoid oriented toward the base of the thumb with the wrist in extreme flexion. One of these served as a guide wire for a cannulated screw and the other served as a derotational wire. Care was taken to place the guide wire for the screw perpendicular to the fracture site and as volar as possible, while maintaining sufficient purchase of the proximal and distal fragments. The headless compression screw was inserted and buried underneath the articular surface by approximately 2 mm, and the derotational wire was then removed .

Once the fracture nonunion was secured, a dorsal trough was created across the nonunion site with a side-cutting burr in a nonarticular location. All nonvascular nonviable tissue was curetted out and excavated from the nonunion site. A microsuture anchor was placed at the floor of the trough to avoid dislodgement of the graft. Then, the graft with its capsular attachment was gently inserted into the scaphoid trough with minimal rotation (10–30°) due to the close proximity of the graft donor site. The graft was secured with a mattress stitch, from the suture anchor, through the perimeter of the graft periosteum. Care was taken to tie this stitch over the graft without compressing the pedicle. Hemostasis was obtained, the wound was irrigated, and the incision was closed with 3–0 nylon sutures .

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