Imaging Studies
Because the thumb lies out of the plane of the hand, suspected fractures and/or dislocations of the thumb may require special radiographic views.
In Robert view, the hand is hyperpronated so that the dorsum of the thumb lies on the radiographic plate; this gives a true anteroposterior view of the thumb. [4]
In Bett view, the hand is pronated approximately 20-30° and the imaging beam is directed obliquely at 15° in a distal to proximal direction, centered over the trapeziometacarpal joint. In this view, the thumb CMC joint is well visualized, as well as the articulations of the trapezium with the trapezoid, scaphoid, and index metacarpal. [4]
Specific injuries have unique radiographic considerations.
MCP joint
Evidence of an irreducible thumb MCP dislocation may be indicated radiographically. The presence of a widened MCP joint suggests soft tissue interposition within the joint, indicating a possible irreducible dislocation. The presence of sesamoids within this joint indicates probable volar plate rupture with interposition of this structure within the joint. [5]
Skier and/or gamekeeper thumb
Occasionally, a bony avulsion fracture from the base of the proximal phalanx is observed. Palmar or radial subluxation of the proximal phalanx may also be present. [6] Valgus stress fluoroscopic views may be a useful adjunct to the clinical stress test. [5] Thirkannad et al have suggested a "two fleck sign" as predictive of a Stener lesion. [22]
CMC joint
To obtain accurate assessment of the CMC joint, Bett view and Robert view are useful. [4] A lateral radiograph shows a V sign that is formed by the radial aspect of the trapeziometacarpal articulation. A broken V sign may indicate undetected CMC joint subluxation. [7] Traction radiographs may be used to assess the degree of comminution in Rolando metacarpal base fractures. [23]
CT and/or tomograms help define the degree of comminution within a fracture as well as suspected impaction of the articular surface.
MRI is the preferred imaging modality to evaluate soft tissues around the thumb. MRI has shown sensitivity and specificity approaching 100% in distinguishing Stener from non-Stener lesions in skier thumb. [23]
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Bennett fracture.
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Pinning of Bennett fracture.
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Rolando fracture - There is intra-articular comminution.
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Pinning of Rolando fracture.
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An intraoperative photograph of a Stener lesion.
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The strong pull of the abductor pollicis longus frequently leads to displacement of the metacarpal shaft in a radial direction and may require operative intervention.
