38 Corrective Osteotomy for Scaphoid Malunion
Successful treatment of scaphoid fractures requires the achievement of bony union as well as the restoration of normal carpal alignment. It is well established that scaphoid nonunions lead to functional impairment and progressive carpal collapse. Over time, up to 97% of patients will develop carpal osteoarthritis.1 , 2 Less is known about the incidence and natural history of scaphoid malunions. There is increasing evidence, however, that patients with healed malunited scaphoids can continue to have symptoms including pain with activities, loss of wrist extension, and weak grip strength.3 – 9
The classic deformity of a malunited scaphoid is multiplanar and includes shortening, a “humpback” flexion deformity in the sagittal plane, ulnar deviation of the distal fragment in the coronal plane, and supination of the proximal fragment relative to the distal fragment in the axial plane ( Fig. 38.1 ).10 , 11 Dorsal intercalated segmental instability (DISI) is most commonly seen in fractures distal to the dorsal apex of the scaphoid ridge.11 In a cadaveric model of simulated scaphoid malunions, Burgess demonstrated loss of radiocarpal and midcarpal extension with an increasing flexion deformity of the scaphoid.12
In a long-term retrospective study of 27 patients with Russe bone grafting of scaphoid nonunions, Stark et al observed radiographic evidence of carpal arthrosis in 40% of patients at a mean follow-up of 12 years.13 Amadio et al demonstrated that abnormal scaphoid anatomy and carpal malalignment can lead to an increased risk of carpal osteo-arthritis.7 In a series of 46 united scaphoid fractures analyzed by clinical examination and trispiral tomography, Amadio et al noted that 26 of the healed fractures had a humpback deformity with increased flexion angulation of the scaphoid. Only 27% of patients with a lateral intrascaphoid angle greater than 45 degrees had a satisfactory clinical outcome compared with 82% of patients with normal scaphoid anatomy. Degenerative arthritis was present in 54% of the scaphoid malunions, compared with 22% of the anatomical scaphoids. Similar results were observed by Condamine et al who reported fair or poor functional results in 35 of 40 patients with moderate or severe scaphoid malunions.8
Although Amadio et al demonstrated a high incidence of arthritic changes and poor patient outcome in patients with scaphoid malunions, Jiranek et al reported minimal functional limitations and disability in their series of scaphoid malunions.14 In a prospective study of united scaphoid fractures that were treated nonoperatively, Forward et al demonstrated that the majority of patients do well in the short term (1-year follow-up) despite residual shortening and flexion deformities.15 No correlation was found between the height:length ratio and lateral intrascaphoid angle and any of the clinical outcomes of pain score, grip strength, range of motion, and disability of the arm, shoulder, and hand (DASH) scores.
Because the majority of scaphoid malunions appear to do well, surgical correction should be reserved for symptomatic patients. The indications for corrective osteotomy include pain, weakness, and limited range of motion that are associated with radiographic evidence of a scaphoid deformity. The majority of unstable scaphoid fractures tend to occur in younger patients with higher functional demands. Because there is evidence in the literature supporting the prevention of late degenerative arthritis, corrective scaphoid osteotomy should be considered at an early stage in the symptomatic patient.
Contraindications to surgery would include associated radiocarpal or midcarpal arthritis, active infection, or a poor soft tissue envelope. Vascular disease, poor bone quality, and a history of smoking are relative contraindications.
▪ Preoperative Assessment
Subjectively, the most common symptoms are weakness of hand grip, wrist pain with activities of daily living, and limitations of wrist motion. The clinical examination typically demonstrates tenderness over the anatomical snuffbox and/or the scaphoid tubercle. Measurements of wrist flexion-extension and radioulnar deviation with a goniometer as well as grip strength with a Jamar dynamometer (Jamar® Sammons Preston Inc., Bollingbrook, IL) are recorded and compared with the contralateral side.
Preoperative radiographs of the injured and contralateral wrists are necessary to assess the scaphoid anatomy for correction of the angular and rotational deformities in the anteroposterior (AP) and lateral planes. Careful measurements are performed to determine the precise size and shape of bone graft needed. Comparative radiographs will show a foreshortened scaphoid with ulnar displacement of the distal fragment. The lateral intrascaphoid angle is used to evaluate the humpback deformity. It is measured as the angle between two lines perpendicular to the proximal and distal articular surfaces ( Fig. 38.2A ). On the lateral radiographs, the radiolunate, capitolunate, and scapholunate angles are recorded. A concomitant DISI deformity is usually present with a dorsally rotated lunate and an increased radiolunate angle. Scaphoid lengths are measured using posteroanterior (PA) views of both wrists in maximal ulnar deviation. Good quality enlarged standard scaphoid views are used to evaluate the intrascaphoid angles. The PA intrascaphoid angle is the angle between two lines perpendicular to the proximal and distal articular surfaces ( Fig. 38.2B ). Scaphoid deformity can be further evaluated with computed tomographic (CT) scans with three-dimensional reconstructions.
▪ Surgical Technique
The scaphoid is approached through a radiopalmar zig-zag incision at the level of the wrist flexion crease and continued distally to the base of the thumb. Deep exposure is carried down between the flexor carpi radialis tendon and the radial artery. The wrist capsule is incised in line with the oblique thenar limb of the skin incision with stay sutures placed in the strong radioscaphocapitate ligament to facilitate final closure.
Two parallel 1.2 mm Kirschner wires are inserted on each side of the osteotomy site and used as joysticks to manipulate the scaphoid fragments into the corrected position following completion of the osteotomy ( Fig. 38.3A ). Measurement of the angles subtended by the K-wires allow for confirmation of the accuracy of correction intraoperatively (extension and derotation).
The osteotomy is performed transversely at the old fracture site with a small oscillating saw, with care not to damage the point of entry of the dorsal ridge vessels ( Fig. 38.3B ). Care is taken to leave the dorsal cortex intact. Next the wrist is extended over a rolled towel. This maneuver allows for opening of the scaphoid fracture site palmarly for correction of the humpback flexion deformity. Restoration of full wrist extension is associated with combined extension and supination of the distal fragment ( Fig. 38.3C ). This is verified by observing the new position of the Kirschner wires in both the sagittal and axial planes. Ulnar deviation is corrected by opening the osteotomy on the ulnar side with a small laminar spreader.
A corticocancellous wedge graft shaped to fit the defect is harvested from the iliac crest and inserted snugly into the osteotomy gap, while the assistant maintains the correct position by holding the K-wires in place ( Fig. 38.3D ). Provisional fixation is performed with Kirschner wires under fluoroscopic imaging. Complete restoration of full passive wrist extension is tested again at this time. The scaphotrapezial joint capsule is incised transversely to facilitate screw placement. Definitive fixation of the osteotomy is achieved with a headless Herbert compression screw (Zimmer Inc., Warsaw, IN) ( Fig. 38.3E ). Finally, the redundant edges of the bone graft are smoothed off with a burr and rongeur. The wrist capsule, including the strong volar radioscaphocapitate ligament, is closed with nonabsorbable interrupted sutures.
Postoperatively, a thumb spica splint is applied for 10 days followed by suture removal and immobilization in a thumb spica cast for an additional 3 weeks. Thereafter, a removable wrist brace is worn until the patient feels comfortable. At 8 weeks, radiographs and PA tomograms are obtained to assess union. Radiographic criteria of union include the disappearance of the osteotomy lines in plain radiographs, tomographic evidence of bridging bony trabeculae on both sides of the interposed graft, and no radiographic signs of screw loosening.