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Acute Osseous Injury to the Wrist
Prevalence, Epidemiology, and Definitions
Acute osseous injury to the wrist may be encountered in a subject who has received direct trauma to the wrist or who has fallen on the outstretched hand (popularly referred to as FOOSH). Radiographic evaluation remains the primary modality for initial assessment. The multiplanar capability of CT and MRI contributes osseous and soft tissue detail useful for complex injuries and occult fracture evaluation. The force vector and the position of the hand during trauma cause characteristic patterns of injury. Factors such as patient age and cortical bone thickness also contribute to common injury patterns.
Anatomy (Including Gross Anatomy and Normal Variants)
The wrist is a complex unit of multiple bones, joints, and ligaments ( eFig. 14-1 ). The anatomic region of the wrist, from proximal to distal, includes the distal radius and ulna, the eight carpal bones, and the proximal portions of the five metacarpals. The eight carpal bones are configured into proximal and distal rows. The proximal carpal row articulates with the distal radius, forming the radiocarpal joint space. The midcarpal joint space is located between the proximal and distal carpal rows. The articulation of the distal carpal row with the bases of the metacarpals forms the carpometacarpal joints. The radial aspect of the distal ulna articulates with the distal radius, referred to as the distal radioulnar joint (DRUJ). The orientation of the rows and arcs of the carpal bones is maintained by a complex arrangement of ligaments. These ligaments function to stabilize the wrist and to preserve a normal relationship with the distal radius, ulna, and proximal metacarpals.
Biomechanics
Special Anatomic Considerations
Located on the dorsal surface of the radial aspect of the wrist is the anatomic snuffbox, whose boundaries include the tendons of the extensor pollicis longus and the abductor pollicis longus. Of clinical importance is the scaphoid, which forms the floor of the snuffbox. Localized pain in this region after trauma is suggestive of fracture.
The scaphoid is the most singular bone of the wrist in that it spans both the proximal and distal carpal rows and therefore makes it more prone to injury than the other carpal bones.
A relative bare area of ligaments called the “space of Poirier,” located at the volar aspect of the midcarpal region, represents an area prone to instability.
A thick band of fibrous tissue is present between the distal ulna and the proximal carpal row that assists in stabilizing both the DRUJ and the ulnotriquetral space; this is named the triangular fibrocartilage complex (TFCC). This complex consists of the triangular fibrocartilage (TFC) and the meniscal homologue.
Lister tubercle is a small bony projection at the dorsal surface of the distal radius and is a useful anatomic landmark. A longitudinal line drawn from the third metacarpal to Lister tubercle will course through the capitate and the lunate.
Radial volar tilt and radial inclination of the distal radius are measurements that influence orthopedic management and treatment to improve outcome.
The angle created by tangential lines running from the dorsal to volar aspect of the distal radial articular surface ranges between 10 and 25 degrees in normal subjects and is known as the radial volar tilt ( eFig. 14-2 ). The radial inclination, formerly referred to as ulnar slant, is the angle created by tangential lines from the radial styloid process to the ulnar aspect of the radius and ranges normally from 15 to 25 degrees. Fracture deformity and displacement may alter these angles. Depending on the severity of the injury, both closed reduction and open reduction with internal fixation (ORIF) attempt to restore normal anatomic alignment and reduce complications such as radial shortening and angulation deformity.
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