10 Scaphoid Nonunion: Open Reduction and Dorsal Bone Grafting
▪ Rationale for the Procedure
Although the natural history of a scaphoid nonunion has not been clearly delineated, there is considerable literature suggesting that the untreated symptomatic scaphoid nonunion can progress to carpal collapse with a predictable pattern of wrist arthritis and a poor functional outcome.1 To achieve union and prevent such a devastating outcome, Matti recommended nonunion repair via a dorsal approach with the removal of all necrotic bone, cartilage, and fibrous tissue and filling of the cavity with an autogenous cancellous bone graft.2 In 1960, Russe modified the procedure by utilizing a volar approach because he believed that it was less likely to damage the scaphoid blood supply.3 In 1980, Russe further modified the technique by inserting two corticocancellous inlay grafts. Numerous authors have reported high union rates with the Russe technique, which has been particularly advocated for nonunion of the scaphoid waist region without a “humpback” deformity and carpal instability. The technique has been considered the “gold standard” of scaphoid nonunion management. However, prolonged immobilization is usually required postoperatively, and stiffness, muscle atrophy, and chronic pain can occur.4 , 5 In addition, fixation of the scaphoid, if required, was limited to the use of Kirschner wires. This lack of rigidity and the subsequent need for prolonged immobilization led Dr. Timothy Herbert to design a headless compression screw that revolutionized the management of scaphoid fractures and nonunions.6 In 1989, DeMaagd and Engber reported their favorable experience with a dorsal (“retrograde”) approach and Herbert screw fixation for proximal pole nonunion.7 In 1993, Watson et al described their experience with bone grafting and K-wire fixation in a large series of patients with a nonunion of the proximal pole, waist region, or distal pole of the scaphoid.8 They reported an overall union rate of 89% with a 78% union rate noted in those patients with a nonunion of the waist region. Despite Matte’s original work, advances in implant design, and the clinical experiences of DeMaagd and Engber and Watson et al, the volar approach continues to be advocated for nonunion of the waist region because of concerns for the dorsal blood supply. Indeed, recent literature has confirmed that the use of autogenous bone graft and headless screw fixation is associated with high union rates and a shorter time to union, particularly when the screw is inserted in the central third of the scaphoid.9 Screw fixation also reduces the duration of immobilization and, if inserted in the central axis, is biomechanically advantageous with greater stiffness and load to failure.10 However, there are some technical concerns with volar to dorsal screw insertion. The fracture line is frequently oriented from a distal volar to a proximal dorsal direction; thus a screw placed from volar to dorsal may not cross the nonunion site, or it may cross with a minimal number of threads, which is not desirable because motion at the nonunion site is significantly lessened with a longer screw.11 Also, the volar approach does not permit reliable insertion of the screw in the central axis of the scaphoid.12 The dorsal approach is technically easier, and it affords more accurate and reliable screw insertion in the central axis of the scaphoid.12 – 14
When all of the aforementioned anatomical, clinical, and biomechanical information was contemplated by the senior author (PJ) and combined with our clinical success with internal fixation of acute scaphoid fractures via the dorsal approach, it became clear that performing operative treatment of a scaphoid waist nonunion with nonvascularized autogenous cancellous bone graft and headless compression screw fixation via a dorsal approach was feasible and could result in satisfactory outcomes. Since 1999, the senior author (PJ) has been using the technique in carefully selected nonunions of the scaphoid waist and proximal pole.
We routinely obtain plain radiographs ( Fig. 10.1 ), a multiplanar computed tomographic (CT) scan ( Fig. 10.2 ), and magnetic resonance imaging (MRI) with gadolinium ( Fig. 10.3 ) for preoperative planning. The indications for using the technique include an established nonunion of the scaphoid waist region or proximal pole with some remaining vascularity of the proximal scaphoid as confirmed on the MRI with gadolinium. The scaphoid itself should have a relatively well preserved architecture (height, width, and length) with cystic changes at the nonunion site and the absence of sclerotic margins ( Fig. 10.1 ). The ideal candidate is a young, healthy, nonsmoking adult with a short duration (less than 2 years) of nonunion and good preservation of the scaphoid architecture.
Absolute contraindications include a nonunion of the scaphoid waist with carpal collapse, significant bone loss, and/or a humpback deformity; radioscaphoid and/or midcarpal arthrosis [scaphoid nonunion advanced collapse (SNAC) wrist]; and avascular necrosis (AVN) of the entire proximal scaphoid. Relative contraindications include smoking and advanced patient age. Because of concerns regarding surgical failure, the senior author (PJ) does not perform surgery in those patients who smoke unless they agree to stop using all nicotine products for a minimum of 6 weeks prior to surgery and 6 months postoperatively. The patients are informed that smoking is associated with a higher risk of nonunion with the potential need for a salvage procedure.15
▪ Surgical Technique
A general or regional anesthetic may be used. The patient is positioned supine on the operating table with a radiolucent hand table. A pneumatic tourniquet is applied on the proximal arm. Following prepping and draping of the limb, exsanguination is performed with an Esmarch bandage with inflation of the tourniquet to a pressure of 250 mm Hg. The forearm is pronated and a longitudinal incision ∼6 cm in length is placed beginning at the midcarpal joint along the axis of the third metacarpal to just proximal to the Lister tubercle ( Fig. 10.4 ). Full-thickness skin flaps are raised, and the extensor retinaculum and dorsal hand fascia are identified. The dorsal hand fascia is incised longitudinally to expose the finger and wrist extensor tendons ( Fig. 10.5 ). The retinaculum of the third compartment is incised and the extensor pollicis longus (EPL) tendon is carefully released, permitting transposition radially. The second and fourth dorsal compartments are sharply elevated from the distal radius and joint capsule. The extensor digitorum communis (EDC) tendons are gently retracted ulnarly while the extensor carpi radialis brevis (ECRB) and longus (ECRL) tendons are retracted radially with the EPL to expose the underlying joint capsule ( Fig. 10.6 ). The terminal branch of the posterior interosseous nerve can be transected and excised to perform a partial denervation if desired. An inverted T-shaped capsulotomy is made with the transverse limb placed just distal to the dorsal rim of the radius and the longitudinal limb directly over the scapholunate (SL) articulation. The radial capsular flap is carefully elevated from the SL ligament and the proximal scaphoid until the nonunion site is identified. The wrist is then passively deviated radially and ulnarly and the nonunion site is carefully assessed to see if the entire scaphoid moves as a unit or if there is motion between the fragments. We prefer to perform internal fixation of the scaphoid before taking down and further destabilizing the nonunion site, which typically appears as a fibrous union. If there is no motion between the fragments, the guide wire for the Acutrak or mini-Acutrak screw headless cannulated screw system (Acumed, Beaverton, OR) is inserted as described following here. The mini-Acutrak system is recommended in those patients with a small scaphoid or if the nonunion extends proximally such that insertion of the larger standard Acutrak screw may result in fracture of the proximal scaphoid. If motion is noted between the proximal and distal scaphoid fragments, 0.045 K-wires are inserted perpendicularly into the proximal and distal scaphoid fragments and used as “joysticks.” The fragments are then anatomically reduced and a 0.045 K-wire is inserted dorsal to the anticipated guide wire insertion site to prevent rotation or displacement of the proximal pole during screw insertion. The wire is inserted into the trapezium for enhanced stability. The wrist is then flexed over a bolster of rolled towels and the proximal pole and SL ligament are identified. The guide wire is inserted at the membranous portion of the SL ligament and is aimed down the central axis of the scaphoid toward the thumb, as perpendicular to the fracture as possible ( Fig. 10.7 ). The exact insertion point is dictated by the fracture location and orientation. Fluoroscopy is used to confirm correct wire placement ( Fig. 10.8 ). A lateral view of the wrist is obtained but can be difficult to interpret with respect to screw insertion in the central axis. We have found the 30 degree pronated lateral view and dynamic imaging during forearm prosupination to be more helpful. A posteroanterior (PA) view with the wrist held in slight palmar flexion and ulnar deviation is also obtained, with care taken to avoid bending the guide wire. The wire is advanced up to but not into the scaphotrapezial joint. Screw length is then determined. We prefer to subtract 4 mm from the measured length to allow burial of the proximal screw beneath the articular surface and avoidance of the scaphotrapezial articulation. Once the screw length has been determined, the wire is driven into the trapezium to avoid a loss of position during reaming. The cannulated reamer is then used with power followed by manual insertion of the screw ( Fig. 10.9 ). Insertion of the screw in the central axis of the scaphoid is preferred ( Fig. 10.10 ). All wires are then removed and screw position is assessed via fluoroscopy ( Fig. 10.11 ). The nonunion site is identified with a small needle or K-wire. The dorsal aspect of the nonunion site is then debrided with a high-speed burr and continuous saline irrigation. A small curette is used to meticulously excavate the proximal and distal scaphoid down to the screw threads ( Fig. 10.12 ). An ellipsoid-shaped cavity is created as all sclerotic bone, cartilage, and fibrous tissue is carefully removed, with care taken to avoid perforation of the radioscaphoid and scaphocapitate articular cartilage. It is imperative that the cortical shell and articular cartilage of the proximal pole not be violated. An osteotomy of the Lister tubercle is then performed and cancellous bone graft is harvested ( Fig. 10.13 ) and packed tightly into both concavities. Russe described the process as being “like a dentist filling a cavity in a tooth” (Russe) ( Fig. 10.14 ). The capsule and retinaculum are repaired with 3–0 nonabsorbable suture, and the EPL is transposed into the subcutaneous tissue. The skin is closed with 4–0 nylon suture in horizontal mattress fashion. The patient is immobilized in a short-arm plaster splint and discharged to home with instructions on strict elevation of the limb and frequent digital range of motion exercises.
At 2 weeks, the patient returns for suture removal and application of a short-arm cast. The cast is typically discontinued at 6 weeks postoperatively. If the fracture involves the proximal pole or if significant comminution was noted at surgery, or if there is concern regarding stability of the fixation, immobilization in a short-arm cast for up to 12 weeks may be indicated. Following cast removal, a formal supervised therapy program is initiated to achieve satisfactory range of motion, strength, and function. Healing is assessed at 2, 6, and 12 weeks postoperatively with plain radiography. Union is defined as progressive obliteration of the fracture line and clear trabeculation across the fracture site. If there is any question regarding union, a CT scan is obtained at 3 months postoperatively or prior to a return to unrestricted sporting activities.