Upper extremity fractures are among the most common of the extremity injuries with carpal fractures accounting for 18 percent of hand fractures and 6 percent of all fractures [1,2]. Of these, fractures to bones of the distal row are less frequent than fractures of the bones of the proximal row (ie, scaphoid, lunate, triquetrum, and pisiform). Trapezoid fractures are the least common carpal fracture of the wrist, involving less than 1 percent of all carpal fractures. Its shape and location afford protection, and dislocation is probably more common than fracture [3,4].
This topic reviews fractures of the trapezoid in adults. An overview of carpal fractures in adults is presented separately. (See "Overview of carpal fractures".)
The trapezoid is in the distal carpal row and articulates distally with the index metacarpal base, radially with the trapezium, ulnar with the capitate and proximally with the scaphoid (image 1 and figure 1 and figure 2). A detailed discussion of wrist anatomy is provided separately. (See "Anatomy and basic biomechanics of the wrist".)
MECHANISM OF INJURY
Fractures of the trapezoid generally occur with axial loading of the 2nd (index) metacarpal, or may rarely occur secondary to direct dorsal trauma . Wrist hyperflexion with dorsal loading of the index metacarpal and index finger hyperextension with wrist hyperextension have been suggested as mechanisms and likened to the effect of a nutcracker . More typically, with a dorsally applied force to the distal aspect of the index metacarpal a dislocation will occur with the proximal aspect of the metacarpal slipping volar (palmar) to the trapezoid.
SYMPTOMS AND EXAMINATION FINDINGS
Patients usually have some degree of swelling on the dorsum of the hand, and point tenderness dorsally just proximal to the 2nd metacarpal base. Resisted wrist dorsiflexion may cause pain as the extensor carpi radialis inserts on the proximal aspect of the index metacarpal, which is closely fixed to the trapezoid by firm intercarpal ligamentous attachments.