#Colles' Fracture.#--This injury, which was described by Colles of Dublin in 1814, is one of the commonest fractures in the body, and is especially frequent in women beyond middle age. It is almost invariably the result of a fall on the palm of the hand, in the three-quarters pronated position, the force being received on the ball of the thumb, and transmitted through the carpus to the lower end of the radius which is broken off, the lower fragment being driven backwards.
The fracture takes place through the cancellated extremity of the bone, within a half to three-quarters of an inch of its articular surface (Fig. 45). It is usually transverse, but may be slightly oblique from above downwards and from the radial to the ulnar side. In a considerable proportion of cases it is impacted, and not infrequently the lower fragment is comminuted, the fracture extending into the radio-carpal joint.
[Illustration: FIG. 43.--Colles' Fracture showing radial deviation of hand.]
[Illustration: FIG. 44.--Colles' Fracture showing undue prominence of ulnar styloid.]
When impaction takes place, it is usually reciprocal, the dorsal edge of the proximal fragment piercing the distal fragment, and the palmar edge of the distal fragment piercing the proximal. The periosteum is usually torn and stripped from the palmar aspect of the fragments, while it remains intact on the dorsum.
In the majority of cases the styloid process of the ulna is torn off by traction exerted through the medial ulno-carpal (internal lateral) ligament, and in a considerable proportion there is also a fracture of one of the carpal bones.
The resulting _displacement_ is of a threefold character: (1) the distal fragment is displaced backwards; (2) its carpal surface is rotated backwards on a transverse diameter of the forearm; while (3) the whole fragment is rotated so that the radial styloid comes to lie at a higher level than normal.
[Illustration: FIG. 45.--Radiogram showing the line of fracture and upward displacement of the radial styloid in Colles' Fracture.]
_Clinical Features._--In a typical case there is a prominence on the dorsum of the wrist, caused by the displaced distal fragment, with a depression just above it (Fig. 43); and the wrist is broadened from side to side. The natural hollow on the palmar aspect of the radius is filled up by the projection of the proximal fragment. The carpus is carried to the radial side by the upward rotation of the distal fragment, and the radial styloid is as high, or even higher, than that of the ulna. The lower end of the ulna is rendered unduly prominent by the flexion of the hand to the radial side. The fingers are partly flexed and slightly deviated towards the ulnar side; and the patient supports the injured wrist in the palm of the opposite hand, and avoids movement of the part. Occasionally the median nerve is bruised or torn, causing motor and sensory disturbances in its area of distribution.