Treatment of Scaphoid Proximal Pole Nonunions: Dorsal Capsular Vascularized Grafting with Temporary Scaphocapitate Fixation

Background: Scaphoid fractures are the most common carpal bone fractures.¹ Approximately 10% of these fractures progress to nonunion. Nonunion predisposes patients to scaphoid nonunion advanced collapse (SNAC) and osteoarthritis of the wrist, both of which are debilitating diseases, especially when they affect the dominant hand. There has been a trend toward operatively treating scaphoid nonunions with vascularized bone graft and internal fixation.² Despite improved union rates with vascularized bone grafts, there is still a 10% nonunion rate among patients with proximal pole necrosis.³ In this presentation, we highlight a case series of eight scaphoid proximal pole fracture nonunions that were treated with a vascularized dorsal capsular graft,⁴ scaphoid screw fixation, and temporary scaphocapitate fixation.

Methods: We retrospectively reviewed 10 patients who were treated between 2009 and 2015 with dorsal capsular vascularized bone grafts for scaphoid proximal pole nonunions diagnosed on plain radiographs or computed tomography (CT) scan. Two patients were excluded from our review because they were lost to follow-up. Reverse-pedicled, dorsal capsular grafts were raised. Scaphoid proximal pole nonunions were débrided and bone-grafted with cancellous autograft. A dorsal trough was created in the scaphoid for the capsular vascularized bone graft. The scaphoid nonunion was then secured with a scaphoid screw placed down the central axis of the scaphoid. Next, percutaneous fixation of the midcarpal joint between the scaphoid and the capitate was performed to reduce flexion forces at the fracture site. We immobilized the wrist postoperatively for 2 weeks in a dorsal, volar splint, followed by a thumb spica cast for 6 weeks and a removable wrist splint for 4 weeks. All patients were also treated with an ultrasound bone stimulator for at least 8 weeks or until there was radiographic evidence of scaphoid healing. Union was defined as >50% bone bridging on CT scan.

Results: Our case series included seven male and one female patient with an average age of 21. The predominant mechanism of injury was fall on an outstretched hand during a sporting event. Seven patients had a fracture through the proximal pole and one patient had a very proximal waist fracture. Five patients had proximal pole avascular necrosis as diagnosed on CT scan. All patients, regardless of proximal pole necrosis, had union of their scaphoid nonunions. The average time to radiographic union for patients with proximal pole necrosis was 11.5 months and 3.9 months in the absence of necrosis. The average flexion and extension for patients with proximal pole necrosis was 44 and 50, respectively, versus 30 and 40 in the absence of necrosis.

Conclusions: While no treatment option is ideal for such a difficult fracture nonunion, the dorsal capsular graft is straightforward to elevate and mobilize as it has a robust pedicle. While we did achieve healing in all of our patients, we recognize that the time to union was lengthy in this group. In fact, one patient, who took over a year to heal, had a CT scan at six months showing no more than 25% bridging bone. Dorsal capsular grafts and adjuvant low-intensity pulsed ultrasound treatment with temporary scaphocapitate fixation is a powerful combination of surgical treatments for a very challenging subset of nonunions involving the proximal pole of the scaphoid with avascular necrosis.

References

References

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