The Type of Wrist Fracture
A fall on the outstretched hand with the hand and wrist in dorsiflexion results in a variety of injuries depending on the patient”s age .
In the young child ,this force may produce a greenstick(cortical buckling) fracture of the distal radius；（图1）a complete fracture of the distal third of one forearm bone with a cortical buckling fracture of the other, （图2）or one of the Salter-Harris injuries,primarily of the distal radial physis.
In the adult,a fall on the outstretched hand with the hand and wrist dorsiflexed may result in a variety of injuries involving the distal radius . Some examples are the base of the radial styloid process ； the Colles fracture ； comminuted intraarticular distal radial fracture，and the dorsal Barton fracture .
The fracture originally described by Colles before the advent of radiology and based entirely on surgical and autopsy observations, was defined as a transverse fracture at the distal inch of the radius with dorsal and proximal displacement of the distal fragment together with the bones of the wrist and hand. The original description did not include a fracture of the ulnar styloid .Proximal displacement and rotation of the distal radial fragment together with the bones of the wrist and hand ,when seen in lateral projection, give rise to the “silver-fork”deformity characteristic of the Colles fracture. The analogy is to a dinner fork placed upside down and viewed form the side.图3
Although the Colles fracture is the most common injury caused by a fall on the outstretched hand in adults ,it is uncommon in children, in whom physeal injuries are more common.The distal radial fragment together with the carpus and the bones of the hand may be slightly or severely displaced in the characteristic deformity and is usually associated with an avulsion fracture of the ulnar styloid.
The Smith fracture is the reverse of the Colles fracture in that the separate distal radial fragment ,together with the carpus and bones of the hand ,is displaced volarly and rotated proximally .The trasverse fracture line (perpendicular to the long axis of the radius), common to both the Colles and Smith fractures, distinguishes them from the the Barton fracture, which is characterized by an oblique fracture line of the distal radius and which must, perforce, extend intraarticularly. The Smith fracture, （图4）which may also occur in children, is most commonly believed to result from a fall on the flexed wrist.
The Barton fracture differ from the Colles and the Smith fracture in that the distal radial fracture is obliquely, rather than transversely, the distal end of the fracture line is in intraarticular. The oblique Barton fracture line may involve the dorsal aspect of the distal radius(dorsal Barton) （图5）or its volar aspect(volar Barton). The volar Barton fracture is considerably more common than the dorsal. The separate fragment may be large or small, and the radiocarpal separation may be minimal or a complete dislocation. The Barton fracture, as other distal radial fractures, may be associated with a distal ulnar fracture or scapholunate dissociation.
