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Scaphoid Fracture Imaging

Practice Essentials

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, after a fall on an outstretched arm that results in acute dorsal flexion of the wrist. About 5-12% of scaphoid fractures are associated with other fractures, and approximately 1% of scaphoid fractures are bilateral. Scaphoid fracture diagnosis is important because 90% of all acute scaphoid fractures heal if treated early.

Preferred examination

Radiographic evaluation of a scaphoid fracture begins with conventional radiography.
 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.
 

CT scanning 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 scanning can demonstrate healing, which is sometimes misleading on radiographs, particularly with hardware in place.

Instead of CT scanning, MRI can be used as a screening tool for patients with negative radiographic results. Also, magnetic 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. Typically, MRI is not useful in the evaluation of healing.

Ultrasonography can detect dislocated fractures of the scaphoid waist based on cortical disruption and/or parossal hematoma. However, this modality is limited by the difficulties in scanning the proximal and distal thirds of the scaphoid. Non-dislocated fractures are also difficult to detect. Ultrasonography can be used for position monitoring of previously identified childhood fractures, but it requires high operator expertise.

(See the images below.)

A transscaphoid, perilunate dislocation is present

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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Images show delayed union of a scaphoid waist frac

Images show delayed union of a scaphoid waist fracture. The radiograph (left) demonstrates the fracture as well as resorption around this 5-month-old fracture. T1-weighted (middle) and fat-suppressed T2-weighted (right) MRI scans demonstrate the fracture without clear evidence of synovial fluid tracking between the fragments. Eventually, this fracture healed.

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Scaphoid waist fracture with some resorption, as s

Scaphoid waist fracture with some resorption, as seen on a posteroanterior image.

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Stress fractures of the scaphoid are rare and have been attributed to repeated or excessive dorsal flexion of the wrist. Carpal scaphoid stress fractures have been reported in athletes engaging in gymnastics, shot put, diving, badminton, tennis, soccer, and cricket.

According to Evenski et al, scaphoid fractures are often missed in children because of their rarity and because of the difficulty in making a radiographic diagnosis. Of 104 cases with high clinical suspicion but no radiographic evidence of scaphoid fracture, 31 (30%) were found to have scaphoid fractures at radiographic follow-up. Volar tenderness over the scaphoid, pain with radial deviation, and pain with active wrist range of motion were identified as significant predictors. As a result of their findings, the investigators recommended that clinically suspected pediatric scaphoid fractures be immobilized, with repeat radiographs and a clinical examination at 2 weeks.

Pierre-Jerome et al studied 125 cases of acute trauma with negative radiographs, but with clinical examination findings suggesting wrist or distal forearm fracture, and they found occult bone injuries in 78 (62.4%) of the 125 wrists. The occult bone injuries included 53 (68%) of the 78 wrists having more than one injured bone and 25 (32%) having one injured bone. The distal radius was the most frequent location for an occult fracture line. The injuries without a fracture line (contusion) were present in 49 (63%) of 78 wrists and were found most frequently in the scaphoid (35 cases).

Ramos-Escalona et al in a retrospective review of radiographs of 66 scaphoid fractures, to evaluate ulnar variance, found that 21 patients (31.8%) had an ulna-neutral wrist; 6 patients (9.1%) had an ulna-plus wrist; and 39 patients (59.1%) had an ulna-minus wrist. The mean ulnar variance was -1.3 mm (range -5.5, 2.5).

Classification

Scaphoid fractures have been classified according to various criteria. For example, they can be grouped according to the anatomic location, as follows (see the image below):

Tubercle fractures – These are usually uncomplicated, and if nonunion occurs, they are frequently asymptomatic.

Distal-pole fractures – Such fractures are usually uneventful. This group can be subdivided into the following: fractures that involve the articulation with the trapezium and trapezoid; and fractures that do not involve this articulation

Proximal-pole fractures – The more proximally located the fracture plane is, the greater the risk of delayed union, nonunion, and avascular necrosis (AVN).

Pictures show the locations of fracture within the

Pictures show the locations of fracture within the scaphoid bone: (A) tubercle; (B) distal pole, or extra-articular (vs intra-articular to scaphotrapezium or trapezoid joint); (C) waist; and (D) proximal pole.

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

Classification of scaphoid fracture by fracture or

Classification of scaphoid fracture by fracture orientation: (A) transverse, (B) oblique, and (C) vertical.

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Another classification system categorizes scaphoid fractures according to the time of injury and subsequent healing, as follows:

Acute

Delayed union – An incomplete union after 4 months of cast immobilization.

Nonunion – An unhealed fracture with smooth, polished surfaces of fibrocartilage.

This classification system is used in treatment planning, because a delayed union may be successfully treated with prolonged casting, whereas a nonunion requires internal fixation. About 90% of all acute scaphoid fractures heal if treated early.

The most important classification scheme distinguishes stable scaphoid fractures from unstable ones (see the image below).

Images illustrate fracture stability. Nondisplaced

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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Stable fractures are incomplete or, if they appear complete, are likely to have an incompletely disrupted articular surface (that is, intact overlying cartilage). Neither displacement nor motion about the fracture occurs with wrist motion. Stable fractures are not associated with ligamentous injury. They are treated with immobilization alone, although stable fractures usually heal regardless of the type of treatment and can even do so 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. Unstable fractures require fixation; it is impossible to maintain reduction of an unstable fracture with cast immobilization alone.

Diagnostic considerations

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, although the scapholunate ligament may be disrupted, 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 to be 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.

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