50 Scaphoid Nonunion: ORIF and Bone Graft for Humpback Deformity
Scaphoid nonunion with humpback deformity can be treated with open reduction and internal fixation (ORIF) using a nonvascularized, structural autogenous bone graft. If surgery gains union and improves wrist kinematics, it may be able to delay or lessen wrist arthritis.
50.1 Key Principles
Correction of both nonunion and deformity with a nonvascularized graft is considered to potentially delay or lessen wrist arthritis. If arthritic changes are already present, a salvage procedure should be considered. 1
The goal of surgery is a healed and aligned scaphoid with improved wrist kinematics. The hope is that this will slow or arrest the development of scaphoid nonunion advanced collapse (SNAC) type arthritis. It may also limit daily symptoms. The surgery and immobilization are expected to reduce wrist motion. In addition, patients are exposed to risks such as infection, problems at the site the graft is obtained, errant internal fixation, and persistent nonunion.
Nondisplaced scaphoid fractures can heal with adequate protection. However, about half of displaced fractures do not unite. Some scaphoid nonunions are fibrous, and there is no increase in deformity because they are not mobile. 1 There is not a reliable and valid method to distinguish stable fibrous unions from unstable nonunions at risk of progressive bone loss and deformity. Mobile nonunions tend to lead to humpback (apex dorsal) deformity of the scaphoid and dorsal intercalated segment instability (dorsal tilt of the lunate seen on a lateral radiograph of the wrist. 2 There is a gradual bone loss of the volar aspects of the fracture surfaces. Scaphoid nonunions with deformity are associated with abnormal wrist kinematics that may be associated with symptoms, as well as progressive radiocarpal and midcarpal arthrosis (often referred to as scaphoid nonunion advanced collapse; SNAC). 3 Surgery intends to achieve more normal wrist kinematics and to slow or arrest the development of SNAC.
Other than active infection, there are no absolute contraindications to corticocancellous bone grafting for scaphoid nonunion with advanced collapse.
Osteonecrosis of the proximal pole may be a relative contraindication, but there is no reliable method of diagnosing osteonecrosis. Additionally, patients with magnetic resonance imaging (MRI) changes consistent with osteonecrosis do not have a higher risk of nonunion with avascular cortico-cancellous grafting compared to patients without avascular changes. 4
It has been proposed that prior failed surgery for nonunion merits a different type of surgery such as a vascularized graft. However, if there are clear technical deficiencies in the prior surgeries, another corticocancellous graft is recommended. Prior failed screw fixation may cause loss of bone from loose implants, but Kirschner wires can often gain fixation of the scaphoid and the bone graft. 5
Some surgeons state that a delay of more than 5 years between the initial fracture and treatment of the nonunion has a poor prognosis. However, the exact time of the initial injury is often unknown, and operative repair should still be considered in such cases. 6
In the presence of any radioscaphoid arthritis, it is better to treat the SNAC nonoperatively or with a salvage procedure, because restoring kinematics will probably not slow and cannot reverse the arthritis.
50.5 Special Considerations
The role of attempts to diagnose osteonecrosis of the proximal pole using MRI before operative treatment is debatable (see discussion above). Computed tomography (CT) of the planes defined by the long axis of the scaphoid can help quantify scaphoid malalignment, fragment positioning, bone loss, as well as incipient arthritis, which usually starts in the distal radioscaphoid joint.
Prior surgery can lead to holes in the bone from prior screws, particularly if they are loose. These may make it difficult to use a screw again, and one might need to use Kirschner wires, which were successfully used in the original technique.
50.6 Special Instructions, Positioning, and Anesthesia
Supine, with the involved arm on a hand table
Tourniquet on the upper arm
General anesthesia if the bone graft will be taken from the iliac crease
Regional anesthesia with a brachial plexus block if the graft is taken from the radius