Wrist, Scaphoid Fractures and Complications

Background: The scaphoid is the most frequently fractured carpal bone, accounting for 71% of all carpal bone fractures. Scaphoid fractures often occur in young and middle-aged adults, typically those aged 15-60 years. About 5-12% of scaphoid fractures are associated with other fractures, and approximately 1% of scaphoid fractures are bilateral. The importance of scaphoid fracture diagnosis is clear when one realizes that 90% of all acute scaphoid fractures heal if treated early.

Pathophysiology: The primary mechanism of injury to the scaphoid bone is a fall on an outstretched hand. A scaphoid fracture is part of a spectrum of injuries based on 4 factors: (1) the direction of 3-dimensional loading, (2) the magnitude and duration of the force, (3) the position of the hand and wrist at the time of injury, and (4) the biomechanical properties of ligaments and bones. These factors affect the end result of the fall: distal radius fracture, ligamentous injury, scaphoid fracture, or a combination of these.

Frequency:

In the US: Approximately 345,000 new scaphoid fractures occur each year in the United States.

Mortality/Morbidity: Concurrent fractures about the wrist occur in 5-12% of scaphoid fractures. The most frequently encountered are radial styloid fractures, triquetrum fractures, capitate fractures, or transcarpal perilunate fracture-dislocations (see Image 1). Concurrent fractures of the distal radius are infrequent. When they do occur, the distal radius fracture determines the outcome and dictates treatment (see Image 2). Additional fractures are more common in young individuals and in those with associated high-impact injuries than in others. In one study, associated radial head fractures were found in 6% of all scaphoid fractures.

Complications of scaphoid fractures may include malunion, delayed union and nonunion, and avascular necrosis (AVN). Osteonecrosis is more common in scaphoid fractures than most another bones because of the blood supply to this bone. Please refer to the discussion in Anatomy.

Malunion

o Subsequent radiographic evaluation of scaphoid fractures should be used to assess complications.

o Malunion may lead to limited motion about the wrist, decreased grip strength, and pain.

o The most frequent pattern of malunion is persistent angular deformity, or the humpback deformity.

o Angular deformity can be quantified by using the intrascaphoid angle. In the sagittal plane, the proximal and distal articular surfaces of the scaphoid are identified and a line drawn perpendicular to this (similar to determining the line for the lunate in evaluating capitolunate and scapholunate angles). Because these do not usually intersect, perpendicular lines can be drawn to measure this angle. An abnormal intrascaphoid angle is greater than 35°. An intrascaphoid angle greater than 45° is associated with a poor clinical outcome. Often, this angulation is associated with a dorsal intercalated segmental instability (DISI) pattern of instability.

o Although case reports of spontaneous correction of scaphoid malunion in children exist, the scaphoid has little potential for remodeling when compared with the rest of the pediatric skeleton.

o Malunion usually is treated with osteotomy and bone grafting to correct angular deformity and length. Ligamentous instability is treated at the same time.

Delayed union and nonuniono Delayed union is incomplete union after 4 months of cast

immobilization. Nonunion is an unhealed fracture with smooth fibrocartilage covering the fracture site. Synovial fluid is present in the interval.

o About 10-15% of all scaphoid fractures do not unite. Some degree of delayed union or nonunion occurs in nearly all proximal pole fractures and in 30% of scaphoid waist fractures.

o Delayed union is anticipated if fracture treatment is delayed for several weeks. The risk of nonunion increases after a delay of 4 weeks. These delays may be related to the patient's failure to seek treatment for a presumed sprain, but they more frequently are related to improper or incomplete immobilization or a failure to diagnose and treat the acute fracture (see Image 3).

o Fracture instability, often unrecognized, is a common cause of delayed union and nonunion. Other factors that influence healing are fracture location, degree of displacement, instability, and osteonecrosis.

o As many as 30% of scaphoid fractures develop increased density of the proximal pole. This frequently is reversible, and it no longer is considered a sign of impending nonunion or osteonecrosis. Often, it

is seen with delayed union, and it is thought to be related to relative ischemia in the proximal pole (see Image 4).

o Sakuma et al evaluated MRI findings in scaphoid nonunion. They found no difference in the MRI appearances in 7 patients with a plain radiographic finding of increased opacity of the proximal pole and in 25 patients with normal opacity in the proximal pole.

o Delayed union or persistent motion about the fracture may lead to the development of cyst formation about the fracture. Healing leads to the ingrowth of granulation tissue and eventual bone formation.

o Radiographic hallmarks of nonunion are the following: sclerosis at the fracture site, a persistent lucent line that usually is wider than 2 mm, cystic cavitation, displacement of more than 1 mm, and local tenderness. The sclerotic margins, though characteristic, may become evident only after several months or years as the pseudoarthrosis matures. Osteonecrosis of the proximal pole may or may not be present. Fibrosis and adhesions may decrease mobility about the nonunion, but all nonunions are considered unstable (see Image 5).

o Arthrography has been used to evaluate pseudoarthrosis versus fibrous union. Contrast material flows between the fracture fragments when a true pseudoarthrosis is present.

o Polytomography and CT have been used to evaluate osseous bridging.

o MRI is not an adequate evaluation for nonunion. T1-weighted MRIs have been reported to show low signal intensity in the distal and/or proximal fragments when they are not united with a variable T2-weighted appearance. The investigators reported normal marrow signal intensity in 8 of 10 cases with radiographic union; however, radiographs and CT scans showed union in 2 cases in which MRIs demonstrated decreased signal intensity in the proximal pole.

o A nonunion of the scaphoid tubercle is typically asymptomatic and often not treated. If symptomatic, these fractures may be fixed with K wires, or the fragment may be removed. Also, removal of an adjacent inflamed bursa may successfully treat symptomatic nonunion.

o Treatments of delayed and nonunion vary. If the delayed union is stable and less than 6 months old relative to the time of injury, prolonged cast immobilization with or without electrical stimulation may be used. Several methods of internal fixation and surgical techniques exist; none have universally good results. The treatment of choice for a symptomatic nonunion is placement of a bone graft and fixation. Occasionally, intercarpal fusion and excision of the proximal pole or entire scaphoid are used as treatment methods. Rarely, proximal row carpectomy is performed. Many surgeons treat all nonunions rather than only the symptomatic ones because chronic nonunions are associated with secondary osteoarthritis.

o Results of the studies by Mack et al and Ruby et al have suggested that the natural history of scaphoid nonunion is early arthritis. Their studies have been criticized for their selection bias, with the suggestion that neither the incidence of truly asymptomatic nonunion without early degenerative change nor the time interval to the development of arthritis is known.

o Some patients with a scaphoid nonunion continue to work without symptoms for as long as 20 years. Most believe that arthritis eventually becomes symptomatic and that it should be prevented if possible.

o Radiographically, healing across a nonunion may be difficult to evaluate. Cystic lucencies often become less obvious over time, but they may persist. These lucencies are more likely on the radial side of the scaphoid. If lucencies on one side of the fracture are resolving, healing is likely.

o Success rates for the treatment of nonunion are as high as 82%. Initial failure typically is treated with reattempted bone grafting.

Avascular necrosis o Osteonecrosis occurs in 15-30% of all scaphoid fractures, and most

of these involve the proximal pole. Its incidence increases as the fracture line becomes more proximal; this decreases the probability that the blood supply to the proximal pole is preserved.

o A bone graft often is placed in an attempt to promote healing, although some consider AVN a contraindication to bone grafting The radiographic hallmark of osteonecrosis is collapse and fragmentation (see Image 6).

o MRI evaluation of scaphoid osteonecrosis may be useful, but is not 100% sensitive or specific. Cerezal et al described the complex patterns of signal intensity changes in the proximal pole. Their results suggest that the entire fragment may not be uniformly vascularized or avascularized. Nonenhanced MRI had a sensitivity of 36%, a specificity of 78%, and an accuracy of 68% in the preoperative evaluation of the vascular status of the proximal fragment. Contrast-enhanced imaging had a sensitivity of 66%, a specificity of 88%, and an accuracy of 83%. Qualitative assessment of enhancement on fat-suppressed T1-weighted images was used. The degree of vascularity (rather than complete absence or presence) may prove to be useful in determining the likelihood of successful bone grafting in the presence of AVN.

o Sakuma et al evaluated the signal intensities of the nonunion on T1- and T2-weighted MRIs and correlated the findings with the success of bone grafting. Signal intensity was divided into 3 levels: normal (equal to that of the rest of bone marrow), slightly decreased (less than that of bone marrow but greater than that of cortex), and decreased (less than that of cortex). Both sequences

were important. In cases with decreased signal intensity on T1- and T2-weighted sequences, no healing occurred. The healing rate was 75% with hypointensity on T1-weighted images and slight hypointensity on T2-weighted sequences, 92% with slight hypointensity on T1-weighted images and isointensity on T2-weighted images, and 100% with slight hypointensity on T1- and T2-weighted images or hypointensity on T1-weighted images and isointensity on T2-weighted images.

o Further outcome studies are needed because the prognosis depends on the amount of devascularized bone, the size of the proximal fragment, and bone integrity. In the femoral head, changes in AVN have been shown to be reversible. Successful surgery leads to the reestablishment of the viability of the proximal pole as it heals.

Arthritis

o Follow-up studies in patients with previous scaphoid fractures, especially those with nonunion and malunion, should be used to evaluate for the presence of arthritis.

o Arthritis may involve the radioscaphoid joint, especially with AVN, but it may involve the other adjacent joints as well. Long-standing scaphoid nonunion may result in carpal collapse. This is called a scaphoid nonunion advanced collapse (SNAC) wrist, which is similar to scapholunate advanced collapse (SLAC) wrist found with chronic scapholunate ligament tears (see Images 5-6). This pattern may present 4-5 years or more than 20 years after the initial injury. Degenerative changes are usually first found in the radioscaphoid joint, followed by the scaphocapitate and then lunocapitate joints. Most patients with SNAC wrist with nonunion of the middle or distal third also have DISI.

Age: Scaphoid fractures often occur in young and middle-aged adults, typically those aged 15-60 years. In adults, 70% of scaphoid fractures involve the waist; 10-20%, the distal pole; 5-10%, the proximal pole; and 5%, the tubercle. Historically, the distribution in children is different: About 52% involve the tubercle; 33%, the distal third; and 15%, the waist. Proximal pole fractures are rare, and most heal without complication. However, as more children are participating in organized sports, the distribution of fractures in children has become similar to that of adults.

Anatomy: The scaphoid lies at the radial border of the proximal carpal row, but its elongated shape and position allow bridging between the 2 carpal rows because it acts as a stabilizing rod. The scaphoid articulates with the radius,

lunate, capitate, trapezoid, and trapezium. As a result, nearly the entire surface is covered by hyaline cartilage. Vessels may enter only at the sites of ligamentous attachment: the flexor retinaculum at the tubercle, the volar ligaments along the palmar surface, and the dorsal radiocarpal and radial collateral ligaments along the dorsal ridge.

The dorsal and volar branches of the radial artery provide the blood supply to the scaphoid. The primary blood supply comes from the dorsal branch of the radial artery, which divides into 2-4 branches before entering the waist of the scaphoid along the dorsal ridge. The branches course volar and proximal within the bone, supplying 70-85% of the scaphoid. The volar scaphoid branch also enters the bone as several perforators in the region of the tubercle; these supply the distal 20%-30% of the bone (see Image 7).

Clinical Details: With a fall on an outstretched hand, the wrist is extended, and the forearm is pronated at the time of impact. With impact on the thenar side of the wrist, the result is dorsiflexion and radial deviation. In contrast to distal radius fractures, scaphoid fractures may be the result of more distal impact of forces focused at the intercarpal joint, with subsequent increased force across the scaphoid waist (see Image 8). This same mechanism may lead to ligamentous injury, notably scapholunate dissociation, rather than fracture.

Fractures of the distal pole and tubercle often are due to a direct impact or blow. Typically, no ligamentous injury occurs. Avulsion fractures may be seen along the radial surface at the attachment sites of the radial collateral ligament, the result of forced ulnar deviation. Stress fractures of the scaphoid waist may occur with repeated stress on the scaphoid. These fatigue fractures usually are incomplete and typically occur in gymnasts and shot-putters.

Scaphoid fractures have been classified according to various criteria. Fractures can be grouped according to the anatomic location: tubercle, distal pole, waist, or proximal pole (see Image 9). Tubercle fractures are usually uncomplicated, and if nonunion occurs, they are frequently asymptomatic. Distal pole fractures usually are uneventful, but it should be further subdivided into those that involve the articulation with the trapezium and trapezoid and those that do not. As the fracture plane is more proximally located, the risk of delayed union, nonunion, and AVN increases.

Scaphoid fractures can also be classified according to the plane of fracture with respect to the long axis of the scaphoid into horizontal oblique, transverse, and vertical oblique fractures (see Image 10). Increased shear forces in vertical oblique fractures may prolong the time for fracture healing.

Scaphoid fractures can also be classified with regard to the time of injury and subsequent healing, as follows: acute, delayed union, and nonunion. Delayed union is defined as incomplete union after 4 months of cast immobilization.

Nonunion is an unhealed fracture with smooth, polished surfaces of fibrocartilage. This classification is used in treatment planning, because delayed union may be successfully treated with prolonged casting, whereas nonunion requires internal fixation. About 90% of all acute scaphoid fractures heal if treated early.

The most important classification scheme distinguishes stable scaphoid fractures and those unstable fractures (see Image 11). Stable fractures can be treated with immobilization alone, but unstable fractures require fixation. Stable fractures are those that are incomplete, or, if they appear complete, they likely have an incompletely disrupted articular surface (the overlying cartilage is intact). Neither displacement nor motion about the fracture occurs with wrist motion. These fractures are not associated with ligamentous injury. Stable fractures usually heal, regardless of the type of treatment and even without treatment.

Unstable fractures are complete fractures with motion about the fracture site. Findings that indicate instability include cortical offset greater than 1 mm, fracture angulation, associated ligamentous injury, and motion with ulnar or radial deviation. Ligamentous injury most frequently involves the scapholunate ligament; the scapholunate interval may widen, or a DISI pattern may be seen on a lateral view. It is impossible to maintain reduction of an unstable fracture with cast immobilization alone.

Preferred Examination: Radiographic evaluation of a scaphoid fracture begins with conventional radiography. Bone scintigraphy has had a role in the initial evaluation of wrist trauma. More recently, CT and MRI have been used with increasing frequency in both initial and follow-up evaluations of the fracture and its complications. Early diagnosis of a scaphoid fracture is important because nonunion is more likely if treatment is delayed. The initial assessment of stability influences management; a careful evaluation is required.

Limitations of Techniques: CT is excellent in the initial evaluation of a scaphoid fracture, particularly in a high-performance athlete in whom initial radiographic findings are normal. Also, CT can demonstrate healing, which is sometimes misleading on radiographs, particularly with hardware in place.

Instead of CT, MRI can be used as a screening tool for those with negative radiographic results. Also, MRIs may define bone contusions rather than fracture as the source of pain. It has been used in the evaluation of complications, particularly osteonecrosis, but care should be emphasized in the diagnosis of avascularity because some ischemia is expected in the proximal pole after waist and proximal pole fractures. MRI typically is not useful in the evaluation of healing.

DIFFERENTIALS

Other Problems to be Considered:

When displacement occurs about the scaphoid fracture, ligamentous injury and instability should be suspected. Posttraumatic instability typically involves the proximal carpal row, which acts as a link between the distal radius and distal carpal row. This instability may be static or dynamic. With static instability, the patient is unable to position the carpal bones normally, and the abnormal alignment is readily visible on routine radiographs. With dynamic instability, the carpal alignment appears normal on radiographs, but it becomes abnormal in certain positions or with motions of the wrist.

The most common carpal instability pattern is scapholunate dissociation. It is frequently the first radiographic sign to suggest instability. However, the scapholunate ligament may be disrupted, and yet the scapholunate interval may be normal. A scapholunate distance of 2-3 mm or more on a routine posteroanterior (PA) view suggests elongation and possible disruption of the scapholunate ligament. A distance greater than 4 mm is considered diagnostic of a scapholunate ligament disruption, although this distance should be viewed in the context of the other intercarpal distances.

Recognition of carpal instability is important and helpful in treatment planning, because such instability reflects a more serious injury. Instability patterns may not be recognized on the initial radiographs and should be evaluated with every follow-up study. Intercarpal collapse may predispose the patient to nonunion and degenerative arthritis.

X-RAY

Findings: The initial radiographic assessment of scaphoid fractures is performed with plain radiography. Standard views vary among institutions, but most use a minimum of 3 views: PA; semipronated oblique, often with ulnar deviation; and true lateral. The patient with a scaphoid fracture often holds the wrist in radial deviation, thereby shortening the scaphoid and limiting its evaluation. To elongate the scaphoid, a scaphoid view is often obtained by positioning the wrist in ulnar deviation and angling the tube cranially by 20-40°. A myriad of additional views have been described for better evaluation of different areas of the scaphoid.

A fracture typically is identified as a lucent line with at least 1 disrupted cortex. Occasionally, an opaque line is seen as a result of overriding fragments, a stress fracture, or fracture healing. Angulation of the scaphoid or separate fracture fragments may be seen. Fractures may be difficult to see; only 25% are visible on all views. The PA view allows visualization of 75% of visible fractures; semipronated view, 77%; lateral view, 22%; and semisupinated view, 22%. About

2-5% of scaphoid fractures, particularly incomplete fractures along the capitate-side surface, cannot be seen on the initial image.

Evaluation of the soft tissues may aid in the radiologist's evaluation. The scaphoid, or navicular, fat stripe is fat interposed between the radial collateral ligament and the tendons of the abductor pollicis longus and extensor pollicis brevis. It is visible in 90% of healthy individuals when the soft tissues are visualized. It may be obscured if the wrist is held in radial deviation. Obliteration or displacement of the fat stripe usually occurs within 1 hour after the scaphoid fracture occurs. Frequently, dorsal soft-tissue swelling is present (see Image 12). These findings are nonspecific and can be seen with other fractures and soft-tissue injuries about the wrist. Because a normal fat stripe with a scaphoid fracture is exceedingly uncommon, a scaphoid fracture is virtually excluded when the scaphoid fat stripe is normal (see Image 13).

The type and location of the scaphoid fracture may influence its conspicuity. Small avulsions and incomplete, horizontal oblique, or distal pole fractures all are more difficult to detect than are transverse-oblique complete fractures. Fractures of the distal pole and tubercle may require special views. Technical factors also influence the detectability of scaphoid fractures. Underexposure or overexposure and patient motion limit bone detail. The film-screen combination used can greatly affect bone detail and, therefore, the visibility of subtle fractures. These factors are typically not addressed when comparative image studies are performed.

The stability of the fracture should be addressed at the initial examination, as well as all follow-up examinations. A stable fracture is nondisplaced and does not have evidence of ligamentous instability. An unstable fracture is displaced by more than 1 mm, is angulated, or has a pattern of associated ligamentous instability. The 2 most common patterns of ligamentous instability are scapholunate dissociation and DISI.

Although scaphoid fracture displacement and angulation can be assessed on conventional radiographs, difficulty can arise because of superimposed bone or an inability to position the patient properly. Often, displacement in the coronal plane is readily seen on the conventional radiographs; however, CT allows evaluation of displacement in all planes of orientation. Three-dimensional reformatted images also may demonstrate rotational patterns of displacement.

Angulation of the scaphoid at the fracture is often called the humpback deformity. This angulation is associated with greater likelihood of nonunion, worse clinical outcome, and arthritis. Determination of the intrascaphoid angle can be difficult on conventional radiographs and usually is easier on a tomographic image.

Amadio et al used trispiral tomography to determine the normal and abnormal intrascaphoid angle. The tomographic image that best displayed the scaphoid

was chosen. The articular surfaces were identified, and a line was drawn to connect the extremes of the proximal and distal convex articular surfaces. A perpendicular to each line was drawn, and the resultant angle was noted. The intrascaphoid angle was evaluated in both the coronal and sagittal planes.

Ten normal wrists were studied to determine the normal range. A total of 46 scaphoids with fractures also were evaluated, and the patients were followed up for a mean of 63 months. The normal sagittal intrascaphoid angle was 15-34° (mean, 24° ± 5). An angle of 45° was chosen as abnormal to include most patients with poor clinical outcomes and a minimum of those with good clinical results. The coronal intrascaphoid angle was 32-46° (mean, 40° ± 4). The lateral intrascaphoid angle was a better clinical discriminator, however (see Image 14).

These same authors also developed a second method to assess the intrascaphoid angle. This method, the cortical technique, may be somewhat more reproducible because it is less dependent on the observer to define the convex articular surface. On a sagittal image, a line is drawn over the flattened volar cortex between the proximal convexity and the curve distal to the waist of the scaphoid. A second line is drawn over the dorsal flattening between the waist and the distal convexity. The lateral intrascaphoid angle with this technique is 31.9° ± 8.5. The authors suggested that an abnormal intrascaphoid angle is greater than 42°. This study did not address clinical outcome.

Although polytomography was used in both of these studies, the results should be valid for conventional radiography, CT, and MRI if the landmarks are visualized.

Degree of Confidence: If clinical concern persists despite normal radiographic results, the clinician has 2 main options. First, the patient's hand and wrist can be immobilized, and radiographs can be repeated after 2 weeks to detect an initially occult fracture. Second, additional imaging modalities may be used as alternatives. Radionuclide bone scintigraphy, polytomography, CT, and MRI have all been advocated.

False Positives/Negatives: A linear lucency may be suggested by a prominent trabecular pattern across the waist of the scaphoid (see Image 15). This pseudofracture may be particularly suspicious when it is adjacent to a small tubercle on the radial margin of the scaphoid, a normal structure that may be more prominent in some individuals. The distinguishing feature is an intact cortical margin; careful examination reveals trabeculae that traverse the lucency.

Abdel-Salam et al recommend the acquisition of a comparable view of the contralateral wrist if the pseudofracture line persists at the 2-week follow-up examination. If the appearance is the same in both wrists, a fracture is excluded. If the appearance is different, a fracture is likely. Additional imaging with CT or MRI may be used at this point. Rarely, an accessory ossicle, the os carpi

centrale, can create a mach line that overlies the waist of the scaphoid and gives the appearance of a fracture.

About 2-5% of scaphoid fractures, particularly incomplete fractures located along the capitate-side surface, cannot be seen on the initial image

CAT SCAN

Findings: A section thickness of 1-2 mm is typical, whether sequence or spiral acquisition is used. In the author's experience, edge detail is better defined with direct rather than helical imaging. One-millimeter scanning still allows excellent reformatted images. The oblique sagittal plane through the long axis of the scaphoid may be the preferred plane of orientation.

When the mechanism of injury is considered, optimal display of the volar and dorsal cortices is preferred (see Images 16-17). Presumably, incomplete fractures may be missed on oblique coronal images. Axial imaging with reformatted images can be obtained, provided the reformatted images are in the planes of the scaphoid and not in the anatomic planes. Edge detail is lost, and some blurring inherent to spiral techniques, although many find them adequate.

Degree of Confidence: CT permits accurate anatomic assessment of the fracture. Bone contusions are not evaluated with CT, but true fractures can be excluded. CT allows volumetric analysis for determining the size of graft needed to correct angular deformities.

False Positives/Negatives: Pseudofractures are a plain radiographic phenomenon and not depicted on CT scans. Occasionally, an entering vessel may cause the cortex to be incomplete. This usually is distinguished on adjacent images. As the vessel enters the bone, the walls have a thin, dense rim not found about a fracture line.

MRI

Findings: Recently, MRI has been suggested as an easy, quick, and perhaps cost-effective method to evaluate acute scaphoid fractures. T1-weighted images obtained in a single plane (coronal) are typically sufficient to determine the presence of a scaphoid fracture. This limited evaluation can be cost effective, and unlike CT, it does not require special positioning of the patient's hand, which may be an important consideration in the patient with a painful wrist.

The classic pattern of a fracture on an MRI is a linear focus of decreased signal intensity on T1-weighted images. Increased signal intensity in a distribution similar to that of the T1-weighted images is seen with T2-weighted sequences.

The fracture line may be more difficult to see on T2-weighted images. Short-tau inversion recovery (STIR) or fat-suppressed T2-weighted sequences are very sensitive to edema. Although more sensitive for edema than the T1-weighted images, fractures may be overdiagnosed. A localized or diffuse region of decreased signal intensity without a discrete fracture line is consistent with the microtrauma associated with impaction of bone trabeculae of bone bruises and contusions (see Image 18).

Degree of Confidence: MRI results can lead to the overdiagnosis of scaphoid fractures. Lepisto et al evaluated the use of MRI within 4 weeks of injury in 18 consecutive patients. Of the 11 diagnosed fractures, the fracture line was clearly seen in only 2. The authors did not consider bone contusions as a separate entity and believed that hemorrhage and edema obliterated the actual fracture line. They offered no follow-up report for the patients examined.

In a separate study by Imaedo et al, an oblique image obtained through the long axis of the scaphoid allowed visualization of 11 of 11 fracture lines. The fracture line was visible in 10 of 11 fractures in the coronal plane. High signal intensity, seen in the distal fragment on T2-weighted images, was characteristic of recent fractures. T1-weighted coronal images allow identification of the fracture, which often are seen on an initial coronal scout image. This suggests that limited MRIs in only 1 imaging plane may cause some fractures to be missed.

False Positives/Negatives: Contusions may be falsely identified as fractures when edema is present.

ULTRA SOUND

Findings: Ultrasonography has not been proven useful in the diagnosis of acute scaphoid fractures. Christiansen et al found a sensitivity of 47% and a specificity of 61% when pain was elicited during sonography.

Hodgkinson et al used ultrasonography to measure the distance between the radial artery and the scaphoid. This distance (in millimeters) was compared with that in the uninjured wrist, and a scaphoid index was created on the basis of the ratio of the difference between the 2 sides and the mean distance of the 2. Overlap between fractured and nonfractured groups was considerable. However, no fractures were identified if the scaphoid index was less than 30%. This finding can be considered analogous to a normal scaphoid fat stripe on radiographs.

NUCLEAR MEDICINE

Findings: Radionuclide bone scanning typically is performed 3-7 days after the initial injury if the radiographic findings are normal. Bone scan findings are considered positive for a fracture when intense, focal tracer accumulation is identified.

Degree of Confidence: According to some, 25-60% of scaphoid fractures suspected on the basis of bone scan results are never confirmed at radiography. Most of these are likely bone contusions or incomplete cortical fractures. Treatment can be based on the results of bone scintigraphy, although this practice results in substantial overtreatment of patients, because most small, incomplete cortical fractures and bone contusions are likely to heal, even without treatment.

Negative bone scan results virtually exclude scaphoid fracture. Injury to other carpal bones may also be discovered with radionuclide bone scanning.

False Positives/Negatives: Scaphoid activity on a bone scan is not specific for a fracture, because bone contusions, degenerative disease, intraosseous ganglion, or another physiologically active process may have increased activity within the scaphoid.

As with any fracture, scintigraphic results are positive in all phases of a 3-phase bone scan. This finding helps in distinguishing chronic processes from the acute fracture.

PICTURES

Caption: Picture 1. Wrist, scaphoid fractures and complications. A transscaphoid perilunate dislocation is present with a fracture of the ulnar styloid. Note the typical dorsal position of the distal carpal row. The distal pole of the scaphoid maintains its relationship to the distal carpal row, while its proximal pole retains its relationship to the proximal carpal row.

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Picture Type: X-RAYCaption: Picture 2. Wrist, scaphoid fractures and complications. Posteroanterior (PA) view of the wrist demonstrates a healed radius fracture and ulnar styloid. Also, a nonunited fracture of the proximal pole of the scaphoid is present; this was likely missed when the radius fracture was diagnosed. No sclerotic margins are present to indicate an unequivocal diagnosis of nonunion.

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Picture Type: X-RAYCaption: Picture 3. Wrist, scaphoid fractures and complications. Images show delayed union of a scaphoid waist fracture. Radiograph (left) demonstrates the fracture as well as resorption around this 5-month-old fracture. T1-weighted (middle) and fat-suppressed T2-weighted (right) MRIs demonstrate the fracture without clear evidence of synovial fluid tracking between the fragments. Eventually, this fractured healed.

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Picture Type: ImageCaption: Picture 4. Wrist, scaphoid fractures and complications. Radiographs obtained in this patient with a history of scaphoid fracture demonstrated increased opacity in the proximal pole. A CT scan was obtained to evaluate healing and possible osteonecrosis. Increased attenuation is demonstrated, but the previous fracture has completely healed. Without collapse or fragmentation, this should not be considered avascular necrosis.

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Picture Type: CTCaption: Picture 5. Wrist, scaphoid fractures and complications. Nonunion of the proximal pole scaphoid fracture is demonstrated by the smooth, sclerotic margins on both sides of the fracture. Note mild arthritis at the radioscaphoid joint.

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Picture Type: X-RAYCaption: Picture 6. Wrist, scaphoid fractures and complications. Avascular necrosis of the proximal pole is evidenced by the collapse of the proximal pole in this chronic nonunion. This patient does not have fragmentation at this time. Note the arthritis in the midcarpal joint consistent with a scaphoid nonunion advanced collapse (SNAC) wrist.

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Picture Type: X-RAYCaption: Picture 7. Wrist, scaphoid fractures and complications. Vascular anatomy of the scaphoid. The number of perforators along the scaphoid waist is variable; therefore, among patients with a fracture in this same location, some have a better prognosis. A, Dorsal view of the scaphoid. B, Volar, or palmar, view of the scaphoid.

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Picture Type: ImageCaption: Picture 8. Wrist, scaphoid fractures and complications. Lateral view of the wrist at the time of impact with a fall on an outstretched hand shows the force (arrow) applied to the scaphoid bone (red).

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Picture Type: ImageCaption: Picture 9. Wrist, scaphoid fractures and complications. Pictures show the locations of fracture within the scaphoid bone: tubercle (A); distal pole (B), or extra-articular (vs intraarticular to scaphotrapezium or trapezoid joint); waist (C); or proximal pole (D).

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Picture Type: ImageCaption: Picture 10. Wrist, scaphoid fractures and complications. Classification of scaphoid fracture by fracture orientation as transverse (A), oblique (B), or vertical (C).

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Picture Type: ImageCaption: Picture 11. Wrist, scaphoid fractures and complications. Images illustrate fracture stability. Nondisplaced (A) and incomplete (B) fractures are stable. Displaced fractures (C), angulated fractures (D), and associated ligamentous instability (E) such as dorsal intercalated segmental instability (DISI) are unstable.

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Picture Type: ImageCaption: Picture 12. Wrist, scaphoid fractures and complications. Images obtained in a patient who fell onto the left wrist. Left, Initial radiograph demonstrates bulging fat stripe (arrows). A cast was applied, and the patient returned for follow-up radiography. Right, This study included a scaphoid view, which better demonstrates the tubercle fracture. This injury is more prominent because of resorption about the fracture.

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Picture Type: X-RAYCaption: Picture 13. Wrist, scaphoid fractures and complications. Image shows a normal scaphoid fat stripe. Fat is seen interposed between the radial collateral ligament and the tendons of the abductor pollicis longus (APL) and the extensor pollicis brevis (EPB). An overlying vessel may sometimes obscure a portion of the fat stripe.

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Picture Type: X-RAYCaption: Picture 14. Wrist, scaphoid fractures and complications. Images show a normal intrascaphoid angle. With a lateral radiograph, CT, or MRI, the extent of the articular margin is estimated by using the curved lines. The ends of the curves at each pole are connected and a line is drawn. Perpendicular lines from these lines are used to determine the intrascaphoid angle.

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Picture Type: CTCaption: Picture 15. Wrist, scaphoid fractures and complications. Images show a pseudofracture. Left, Initial radiograph of the wrist demonstrates the normal fat stripe (wide arrow) with a questioned cortical disruption (thin arrow). Middle, Posteroanterior (PA) view obtained 1 week later demonstrates a similar appearance in the questioned lucency across the waist. Note that the line is not straight (arrows) and that trabeculae cross the lucency. Right, Long-axis oblique sagittal CT image obtained after an additional 2 weeks with the wrist in a cast reveals demineralization from disuse, but it does not show a fracture.

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Picture Type: X-RAYCaption: Picture 16. Wrist, scaphoid fractures and complications. Images show positioning for direct sagittal image acquisition. Care must be taken to position the arm obliquely above the patient's head. This patient's arm was positioned horizontally, and although the beam penetrates the long axis of the scaphoid (yellow line), beam-hardening artifact does not allow evaluation of the scaphoid (inset).

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Picture Type: CTCaption: Picture 17. Wrist, scaphoid fractures and complications. Images demonstrate reformation of 1-mm images into a sagittal long-axis image for improved visualization of the scaphoid. Note the nondisplaced fracture through the waist of the scaphoid.

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Picture Type: CTCaption: Picture 18. Wrist, scaphoid fractures and complications. Images obtained in a patient who fell on and outstretched hand, with pain in the anatomic snuff box. The initial radiographs were normal. A, Representative oblique sagittal CT image

does not reveal a fracture. B, T2-weighted MRI demonstrates edema without a fracture line; these findings are consistent with a contusion. T2-weighted images without fat-suppression are no longer commonly used. The edema-pattern with a short-tau inversion recovery (STIR) sequence would likely be more impressive; this finding could potentially lead to the overdiagnosis of a fracture.

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Picture Type: ImageCaption: Picture 19. Wrist, scaphoid fractures and complications.

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