Asheesh Bedi and Peter J. L. Jebson
DEFINITION
The scaphoid is the most commonly fractured carpal bone, accounting for 1 in every 100,000 emergency department visits.12
Scaphoid fractures typically result from a fall on an outstretched hand.
Scaphoid nonunion or proximal pole avascular necrosis (AVN) after a fracture has been associated with considerable morbidity and a predictable pattern of wrist arthritis.15,17,18
The complex anatomy and tenuous blood supply to the scaphoid make operative management of these fractures technically challenging.18
The Herbert classification system organizes scaphoid fractures into four groups: acute stable, acute unstable, delayed union, and established nonunion.
ANATOMY
The scaphoid has a complex three-dimensional geometry that has been likened to a “twisted peanut.” It can be divided into three regions: proximal pole, waist, and distal pole.
The scaphoid functions as the primary link between the forearm and the distal carpal row and therefore plays a critical role in maintaining normal carpal kinematics.
Articulating with the scaphoid fossa of the radius, the lunate, capitate, trapezium, and trapezoid, more than 70% of the scaphoid is covered with articular cartilage.
Gelberman and Menon8 have described the vascular supply of the scaphoid. The main arterial supply is from the radial artery; it enters the scaphoid via two main branches:
A dorsal branch, entering through the dorsal ridge, is the primary supply and provides 70% to 80% of the vascularity, including the entire proximal pole via retrograde endosteal branches.
A volar branch, entering through the tubercle, supplies the remaining 20% to 30%, predominantly the distal pole and tuberosity.
The proximal pole is at increased risk for avascular necrosis (AVN) secondary to disruption of its tenuous retrograde blood supply after a fracture of the scaphoid waist or proximal pole.
Due to its tenuous vascular supply, the scaphoid heals almost entirely by primary bone healing, resulting in minimal callus formation.
The size and shape of the scaphoid, in combination with its precarious blood supply, demands attention to detail and accurate implantation of fixation devices during fracture fixation.
PATHOGENESIS
Scaphoid fractures are most commonly seen in young, active males who fall on an outstretched upper extremity.12
With the wrist dorsiflexed greater than 95 degrees, in combination with 10 degrees or more of radial deviation, the distal radius abuts the scaphoid and precipitates a fracture.12
Most of these fractures occur at the waist region, although 10% to 20% occur in the proximal pole.
Proximal pole fractures are associated with an increased risk of nonunion, delayed union, and AVN.
In children, scaphoid fractures are less common and are most frequently seen in the distal pole.
NATURAL HISTORY
An untreated or inadequately treated scaphoid fracture has a higher likelihood of nonunion. The overall incidence of nonunion is estimated at 5% to 10%, but the risk is significantly increased with nonoperative treatment of a displaced waist or proximal pole fracture.
The natural history of scaphoid nonunions is controversial, but they are believed to result in a predictable pattern of progressive radiocarpal and midcarpal arthritis.8,9,11,14,15,17,18
In an established scaphoid nonunion, the distal portion of the scaphoid may flex, producing a “humpback” deformity of the scaphoid. The loss of scaphoid integrity can result in carpal instability and abnormal carpal kinematics, most frequently manifesting as a dorsal intercalated segment instability (DISI) pattern.
The pattern of carpal instability and secondary arthrosis due to an unstable scaphoid nonunion has been termed a SNAC wrist (scaphoid nonunion advanced collapse pattern of wrist arthritis).11,17
In the SNAC wrist, there is a loss of carpal height with proximal capitate migration, flexion and pronation of the scaphoid, and secondary midcarpal arthritis.17
Factors associated with the development of a scaphoid fracture nonunion include14 :
Delayed diagnosis or treatment
Inadequate immobilization
Proximal fracture
Initial and progressive fracture displacement
Fracture comminution
Presence of associated carpal injuries (ie, perilunate injury)
PATIENT HISTORY AND PHYSICAL FINDINGS
Scaphoid fractures classically occur in the active, young adult population after a fall onto an outstretched hand. Patients present with radial-sided wrist pain.
Classic physical examination findings include: Swelling over the dorsoradial aspect of the wrist
Erythema over the volar radial aspect of the wrist
Tenderness to palpation in the “anatomic snuffbox”
Tenderness with palpation volarly over the distal tubercle
Pain with axial compression of the wrist (scaphoid compression test)
Scaphoid fractures can be part of a greater arc injury. The physician should examine the entire wrist carefully for areas of tenderness and swelling
Plain radiographs are scrutinized for an associated ligamentous injury or disruption of the midcarpal joint as seen in the transscaphoid perilunate fracture-dislocation.
IMAGING AND OTHER DIAGNOSTIC STUDIES
The following plain radiographs should routinely be ordered in the patient with a suspected scaphoid fracture: posteroanterior (PA), oblique, lateral, and dedicated scaphoid views.
The PA view allows visualization of the proximal pole of the scaphoid.
The semipronated oblique view provides the best visualization of the waist and distal pole regions.
The semisupinated oblique view provides the best visualization of the dorsal ridge.
The lateral view permits an assessment of fracture angulation, carpal alignment, and carpal instability.
The dedicated scaphoid view is a PA view with the wrist in ulnar deviation. This results in scaphoid extension, allowing visualization of the scaphoid in profile (FIG 1A).
The following criteria define a displaced or unstable fracture as noted on plain radiographs2,9,14 :
At least 1 mm of displacement
More than 10 degrees of angular displacement
Fracture comminution
Radiolunate angle of more than 15 degrees
Scapholunate angle of more than 60 degrees
Intrascaphoid angle of more than 35 degrees
CT with reconstruction images in multiple planes is used to identify an acute fracture not detected on plain radiographs (FIG 1B,C).
CT is most useful in evaluating an established scaphoid nonunion or malunion.6
Since plain radiographs are often unreliable, CT is preferred for confirming union after a scaphoid fracture.
MRI may be indicated in the evaluation of a suspected scaphoid fracture not detected on plain radiographs (FIG 1D,E). MRI is highly sensitive, with a specificity approaching 100% when performed within 48 hours of injury.13
MRI with gadolinium contrast is helpful in assessing the vascularity of the proximal pole, particularly in the patient with an established nonunion.
A technetium bone scan has been shown to be up to 100% sensitive in identifying an occult fracture.20 Unfortunately, it is also associated with a low specificity and often will not be positive immediately after the fracture.
DIFFERENTIAL DIAGNOSIS
Scapholunate injury
Wrist sprain
Wrist contusion
Fracture of other carpal bone
Greater arc injury
Distal radius fracture
NONOPERATIVE MANAGEMENT
Nonoperative management is indicated for a nondisplaced, stable scaphoid waist or distal pole fracture. Unstable fractures and nondisplaced fractures of the proximal pole are indications for internal fixation based on studies that have demonstrated a poor outcome with nonoperative treatment.2,4,14
The appropriate type and duration of cast immobilization remain controversial. We recommend a long-arm thumb spica cast for the first 6 weeks, followed by a short-arm thumb spica cast until the clinical examination and radiologic studies (usually a CT scan) confirm fracture union.
FIG 1 • A. Radiograph (scaphoid view) of an acute, displaced, comminuted scaphoid waist fracture. B,C. Axial and sagittal CT scan images demonstrating a fracture of the proximal pole of the scaphoid. D,E.T1and T2-weighted MRI images demonstrating a nondisplaced scaphoid waist fracture. (Property of Peter J.L. Jebson, MD.)
Clinical studies have failed to demonstrate any benefit from including the thumb or fingers in the cast.2,4
Similarly, wrist position has not been proven to improve scaphoid fracture healing.
Numerous studies have revealed no difference in union rates for a long-arm versus short-arm cast; however, a randomized prospective study by Gellman et al10 documented a shorter time to union and fewer nonunions and delayed unions with initial use of a long-arm cast.
The morbidity of a nonoperative approach, specifically cast immobilization, has become of increasing concern. A prolonged duration of immobilization is often required for waist fractures, and this can be accompanied by muscle atrophy, stiffness, reduced grip strength, and residual pain. In addition, cast immobilization can cause significant inconvenience for the patient and interference with activities of daily living. The prolonged duration of immobilization is of particular concern in the young laborer, athlete, or military personnel, who typically desire expedient functional recovery.5,16,21
If the clinical history and physical examination are suggestive of a scaphoid fracture but initial radiographs are negative, the wrist should be immobilized for 2 weeks. Repeat radiographs are then obtained. If a fracture is present, resorption at the fracture may be noted. If wrist pain and “snuffbox” tenderness persist but radiographs are negative, a bone scan may be obtained. A negative scan excludes the presence of a scaphoid fracture. A positive scan may indicate an occult fracture or ligamentous injury. CT or MRI is usually indicated for further evaluation.13,20
Alternatively, if there is a high index of suspicion at initial presentation and there is a need to know the status of the scaphoid, MRI or CT of the wrist is obtained.
SURGICAL MANAGEMENT
Indications for open reduction and internal fixation (ORIF) of scaphoid fractures include2,14 :
Any proximal pole fracture
A displaced, unstable fracture of the scaphoid waist
Associated carpal instability or perilunar instability
Associated distal radius fracture
Delayed presentation (more than 3 to 4 weeks) with no prior treatment
A nondisplaced, stable scaphoid waist fracture (Herbert A2 type) in a patient who wishes to avoid the morbidity of cast immobilization. In this clinical scenario, operative treatment should occur only after an explanation of the rationale for, and the risks and benefits of, operative treatment versus cast immobilization.
Preoperative Planning
All imaging studies should be reviewed to accurately define the fracture pattern.
Required equipment: Portable mini-fluoroscopy unit
Kirschner wires
Cannulated headless compression screw system. We prefer to use the Acutrak or mini-Acutrak screw system (Accumed, Beaverton, OR), but any cannulated screw system that permits screw insertion beneath the articular surface may be used.
Positioning
General or regional anesthesia may be used.
The patient is positioned supine on the operating table with a radiolucent hand table at the shoulder level.
The fluoroscopy unit is draped and positioned at the end of the hand table.
A pneumatic tourniquet is carefully applied to the proximal arm.
An intravenous antibiotic is provided before inflation of the tourniquet as prophylaxis for infection.
The limb is prepared and draped, followed by exsanguination of the limb with an Esmarch bandage and tourniquet inflation, usually to a pressure of 250 mm Hg.
Approach
ORIF of scaphoid fractures can be performed through either a dorsal or volar approach.
The specific approaches that will be described include:
Open dorsal approach16
Open volar approach
TECHNIQUES
OPEN DORSAL APPROACH (AUTHORS’ PREFERRED APPROACH)
Exposure
If the fragments are displaced, requiring reduction, pronate the forearm and make a longitudinal skin incision, about 3 to 4 cm long, beginning at the proximal aspect of the tubercle of Lister and extending distally along the axis of the third metacarpal (TECH FIG 1A).
If the fracture is nondisplaced, a smaller skin incision and capsulotomy may be used.
Raise skin flaps at the level of the extensor retinaculum.
Incise the extensor retinaculum overlying the third compartment immediately distal to the tubercle of Lister and carefully release the fascia overlying the extensor pollicis longus (EPL) tendon, permitting gentle retraction of the EPL radially. Similarly incise the dorsal hand fascia longitudinally.
Gently retract the extensor digitorum communis (EDC) tendons ulnarly while retracting the extensor carpi radialis brevis (ECRB) and longus (ECRL) tendons radially with the EPL, thus exposing the underlying radiocarpal joint capsule (TECH FIG 1B).
Make a limited inverted T-shaped capsulotomy with the transverse limb placed just distal to the dorsal rim of the radius and the longitudinal limb directly over the scapholunate articulation (TECH FIG 1C).
The tubercle of Lister is helpful in locating the articulation.
TECH FIG 1 • A. Skin incision used for ORIF of scaphoid fractures via the dorsal approach. B. Retracting the thumb and wrist extensor tendons radially and the finger extensor tendons ulnarly facilitates exposure of the underlying capsule. C. A limited capsulotomy should be performed to expose the proximal scaphoid and scapholunate ligament. (Property of Peter J.L. Jebson, MD.)
Carefully elevate the capsular flaps from the dorsal lunate, the dorsal component of the scapholunate ligament, and the proximal pole of the scaphoid.
Evacuate fracture hematoma.
It is often helpful to extend the longitudinal limb of the capsulotomy to expose the scaphocapitate articulation and the radial aspect of the midcarpal joint.
Especially when elevating the radial flap, take care to avoid stripping the dorsal ridge vessels entering at the scaphoid waist region.
When a satisfactory reduction has been achieved, obtain provisional fixation with derotational 0.045-inch Kirschner wires.
The first wire is inserted dorsal and ulnar to the central axis of the scaphoid, into the trapezium for enhanced stability.
The second derotational wire may be inserted volar and radial to the anticipated central axis insertion site if more fixation is needed.
The derotational wires must be placed such that they will not interfere with central axis guidewire placement, reaming, and screw insertion (TECH FIG 2B).
Fracture Reduction and Provisional Fixation
Distract the carpus manually via longitudinal traction on the index and long fingers.
If the fracture is displaced, insert 0.045-inch Kirschner wire joysticks perpendicularly into the proximal and distal scaphoid fragments to assist in the reduction (TECH FIG 2A).
The accuracy of the reduction can be determined by assessing congruency of the radioscaphoid and scaphocapitate articulations.
Guidewire Placement
The starting position for guidewire is at the membranous portion of the scapholunate ligament origin (TECH FIG 3A,B).
In very proximal fractures, the starting point for the guidewire is as far proximally in the scaphoid as possible, at the mid-aspect of the membranous portion of the scapholunate ligament complex. This point is critical to avoid propagation of the fracture into the proximal scaphoid during insertion of the screw.
TECH FIG 2 • A. Percutaneous insertion of Kirschner wires into the proximal and distal scaphoid (S) fragments is helpful to facilitate manual reduction of a displaced fracture. C, capitate; L, lunate. B. A displaced scaphoid waist fracture has been stabilized with a derotational Kirschner wire placed dorsal and ulnar to the guidewire. The derotational Kirschner wire does not interfere with insertion of the screw in the central axis. (Radiograph is the property of Peter J.L. Jebson, MD.)
TECH FIG 3 • A,B. Note the starting point at the membranous portion of the scapholunate ligament (arrow). C. The 30-degree pronated oblique view demonstrating guidewire placement down the central axis of the scaphoid. (Property of Peter J.L. Jebson, MD.)
With the wrist flexed over a bolster, insert the guidewire down the central axis of the scaphoid in line with the thumb metacarpal.
Be very patient with this important step; proceed with reaming and screw insertion only after central placement has been confirmed on the PA, lateral, and 30-degree pronated lateral views (TECH FIG 3C).
It is critical to insert the wire in the optimal position in all three views to avoid violating the midcarpal joint or the volar surface of the scaphoid.
Take care to avoid bending the guidewire.
Advance the wire up to but not into the scaphotrapezial joint.
Screw Insertion
Determine screw length by measuring the guidewire (TECH FIG 4A).
In the case of minimal fragment separation, subtract 4 mm from the measured length of the wire to allow recession of the proximal screw beneath the articular surface.
If fragments are more displaced, consider compression and choose an even shorter screw.
Advance the wire into the trapezium to avoid loss of position during drilling.
TECH FIG 4 • A. Determining the appropriate screw length. B. Reaming with the cannulated reamer. C,D. Insertion of the screw. (Property of Peter J.L. Jebson, MD.)
Use the cannulated drill (TECH FIG 4B), tap the bone if necessary, and manually insert the screw (TECH FIG 4C,D).
We use the larger Acutrak screw when feasible, but the mini-Acutrak system may be necessary in patients with a small scaphoid or if the fracture is located proximally such that insertion of an Acutrak screw may result in inadvertent propagation of the fracture to the insertion site with fragmentation of the proximal scaphoid.
Remove the guidewire and assess screw position via fluoroscopy using the same views.
OPEN VOLAR APPROACH
Exposure
Radially deviate the wrist and palpate the scaphoid tubercle.
Make a 3to 4-cm incision centered over the scaphoid tubercle, directed distally toward the base of the thumb and proximally over the flexor carpi radialis (FCR) tendon sheath. If the superficial volar branch of the radial artery is encountered, cauterize it at the level of the wrist flexion crease.
Open the FCR sheath and retract the tendon ulnarly. Open the floor of the sheath distally to expose the underlying volar wrist capsule.
Distally, develop the interval by splitting the origin of the thenar muscles in line with their fibers over the distal scaphoid and trapezium.
Incise the capsule longitudinally, taking care to avoid damage to the underlying articular cartilage.
Proximally, divide the thickened radiolunate and radioscaphocapitate ligaments to allow exposure of the proximal scaphoid pole.
Identify the scaphotrapezial joint with a Freer elevator and bluntly expose it.
Dissection over the radial aspect of the scaphoid is limited to avoid injury to the dorsal ridge vessel.
Define and clear the fracture site by irrigation, sharp excision of periosteal flaps, and curetting of debris and hematoma.
Assess the instability of the fracture by wrist manipulation.
It is critical to identify any bone loss, as compression during screw placement can result in an iatrogenic malunion.
Fracture Reduction and Fixation
Obtain correct fracture alignment through longitudinal traction followed by wrist manipulation.
An anatomic reduction may also be achieved by direct manipulation of the fragments with a dental pick, pointed reduction forceps, or joystick Kirschner wires.
Place a provisional 0.045-inch Kirschner wire to secure the reduction. Insert the wire in a retrograde manner from volar distal to dorsal proximal, gaining fixation in the proximal pole.
It is critical to place this wire such that it does not interfere with central axis screw placement.
The central axis guidewire is placed, taking into consideration all the factors detailed above.
To gain the needed dorsal starting position in the distal scaphoid pole, displace the trapezium dorsally with an elevator or resect a small portion of the proximal volar trapezium with a rongeur (TECH FIG 5).
The cannulated compression screw may be inserted using a freehand technique or a commercial device, which may facilitate simultaneous fracture reduction and guidewire positioning.
Fluoroscopy is invaluable during wire and screw insertion and to confirm accurate placement and fracture reduction as described above.
Precisely repair the volar wrist capsule and radiolunate and radioscaphocapitate ligaments with permanent suture.
TECH FIG 5 • Accurate insertion of a screw via the volar approach usually requires partial resection or dorsal displacement of the volar trapezium to expose the distal scaphoid.
POSTOPERATIVE CARE
The patient is immobilized in a below-elbow volar thumb spica splint and discharged to home with instructions on strict limb elevation and frequent digital range-of-motion exercises.
At 2 weeks, the patient returns for suture removal. Rangeof-motion exercises are begun and a removable forearm-based thumb spica splint is worn. The splint is discontinued at 4 to 6 weeks postoperatively.
If the fracture involves the proximal pole or if significant comminution was noted at surgery and there is concern regarding stability of the fixation, immobilization in a shortarm cast for 6 to 10 weeks is indicated. Typically, such fractures take longer to achieve union.
After cast removal, a formal supervised therapy program is initiated to achieve satisfactory range of motion, strength, and function.
Fracture healing is assessed at 2, 6, and 12 weeks postoperatively with plain radiography. Fracture union is defined as progressive obliteration of the fracture and clear trabeculation across the fracture site (FIG 2).
If there is any question regarding fracture union, a CT scan is obtained at 3 months postoperatively or before the patient is allowed to return to unrestricted sporting activities.
OUTCOMES
Surgical fixation of unstable, displaced scaphoid fractures has been increasingly advocated, given the unsatisfactory outcomes that have been reported with nonoperative management.2,4,14 Rigid internal fixation allows for early physiotherapy throughout the healing phase, a more rapid time to union, improved range of motion, and rapid functional recovery.5,10,16,21 Several studies have reported a high rate of union and excellent clinical outcome with minimal morbidity using both limited open and percutaneous techniques.1,3,5,10,19,19,21
Clinical and biomechanical studies have also recently documented the importance of screw position after fixation of scaphoid fractures.7,18 Central placement of the screw is biomechanically advantageous, with greater stiffness and load to failure.7 Trumble et al18 demonstrated more rapid progression to union with central screw position in cases of scaphoid nonunion.
A volar approach has traditionally been used for screw insertion. However, recent studies have raised potential concerns regarding eccentric screw placement and damage to the scaphotrapezial articulation with this approach.21
Our preferred technique for fixation of a scaphoid proximal pole or waist region fracture involves a limited dorsal approach with compression screw fixation.16 The technique is simple and permits visualization of a reliable starting point for screw placement within the central axis of the scaphoid, offering a significant potential advantage over the volar approach. We recently reported our clinical experience in a consecutive series of nondisplaced scaphoid waist fractures.3
COMPLICATIONS
Postoperative wound infections are rare and can be prevented with routine preoperative antibiotic prophylaxis, thorough wound irrigation, and appropriate soft tissue management.
Intraoperative technical problems Inadvertent bending or breakage of the guidewire can occur if the wrist is dorsiflexed with the wire in position or during drilling before screw insertion.
Care should be taken to confirm that the screw is fully seated beneath the articular cartilage to avoid prominence and erosion of the distal radius articular surface. Similarly, failure to carefully judge accurate screw length intraoperatively can result in prominence and erosion of the scaphotrapezial articulation.
Nonunion with or without AVN can occur despite compression screw fixation, particularly with a proximal pole or displaced waist fracture. Stripping of the dorsal ridge vasculature should be avoided. Supplemental cancellous bone graft from the distal radius may be used at the time of fixation if desired.
Other potential but rare complications Hypertrophic scar
Injury to the dorsal branches of the superficial radial nerve
Damage to the scaphotrapezial articulation
Proximal pole fragment comminution
FIG 2 • A healed scaphoid waist fracture after ORIF via the dorsal approach. Although the screw may appear slightly long, both the proximal scaphoid and distal scaphoid are covered with hyaline cartilage not detected on diagnostic imaging. (Property of Peter J.L. Jebson, MD.)
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