Malgaigne asks, by what mechanism are these fractures of the lower extremity of the radius specially produced. In reply he ad duces the following experiment by Nelaton : The_ latter amputated the forearm of a dead body at the elbow, and cut off the olecronon at a level with the head of the radius. He then applied the palm of the hand of the sub ject on a solid plane, the forearm being at the same time directed vertically; he now with a mallet struck a heavy blow directly on the superior extremity of the two bones of the forearm. The wrist broke and became immediately deformed. The dissection re vealed a simple and transverse fracture of the carpal extremity of the radius, with a dis placement backwards of the lower fragment, as with ordinary eases of fracture of the radius in the immediate vicinity of the wrist joint, a species of injury, which in this city is known by the name of " Colles' fracture." It would also appear to Malgaigne, Bouchet, and Voillemier, that this fracture may be the result of a sudden and violent flexion of the hand without the patient having had any fall. This fact was first established by Bouchet, who, in endeavouring to produce dislocation of the wrist on the dead body, only caused in his experiments fractures of the inferior ex tremity of the radius ; sometimes with other disorders, and more particularly with a simul taneous fracture of the styloid process of the ulna.
Symptoms. — If Colles' fracture of the radius be produced by a fall, the patient will, sometimes, be able to say that at the moment of the accident he felt a sensation of some thing having given way near to the wrist-joint. The inferior extremity of the forearm and the hand swell ; the fingers are semi-flexed, and the patient experiences the greatest diffi culty in performing the ordinary movements of the hand, or forearm. He usually pre sents himself to us with the hand of the injured forearm resting on its (attar margin, and supported by the other hand, and in a middle state between proration and supina tion.
The posterior surface of the forearm usually represents a considerable deformity; for a depression is seen to exist about one inch above the line of the wrist-joint, whilst a con siderable swelling occupies the wrist itself and metacarpus ; indeed, the carpus and base of the metacarpus, appear to be thrown back wards so much, as at first view to excite a suspicion that the radius had been dislocated forwards, and the carpus and hand back wards (fig. 930.). On viewing the anterior sur face of the limb we observe a considerable fulness, as if caused by the flexor tendons being thrown forwards ; this fulness extends upwards, to about one-third of the length of the forearm, and terminates below at the upper edge of the annular ligament of the wrist.
The inferior fragment of the radius being salient posteriorly, while the superior is thrown forwards, the injured forearm, viewed side-ways, resembles, in the undulating direc tion of its long axis, the outline, according to Velpeau's idea, of a silver dinner-fork. Besides presenting this very striking de formity, in this fracture we find the hand oc casionally thrown outwards, or towards the radial side, and then the carpal extremity of the ulna presents a strong saliency internally. The degree, however, in which this projec tion towards the inner edge of the wrist takes place, will be found to vary.
The patient is unwilling to attempt to pro nate or supinate his hand, and if we endea vour to communicate such movements, much pain is produced. There is considerable pain felt by the patient when we press firmly with the point of the finger in the exact situation of the fracture.
The internal lateral ligament of the wrist joint is generally put upon the stretch, and the patient usually complains of much distress here ; but this pain, which some patients feel about the lower extremity of the ulna, does not always arise simply from a sprain coin cident with the fracture or from a rupture of the internal lateral ligament of the articula tion of the carpus with the forearm, but we believe sometimes is owing to a fracture of the root of the styloid process of the ulna.
It is in this last case more particularly that the hand "par un mouvement de totalite," is carried outwards, and that the ulna seems very salient, internally (fig. 931.).
A narrowing of the region of the wrist, in the transverse direction, has been much ad verted to by Dupuytren, as a symptom of the fracture we arc now considering, but we believe this narrowing is, in general, more ap parent than real. 'We rather concur with Velpeau, who says, " Many observations have induced me to believe that Dupuytren, and others, have been deceived as to the supposed narrowing of the wrist." He adds, an in terosseous space, in reality, does not exist near to the wrist joint; indeed, there is scarcely any open interval to be seen between the lower extremity of the radius and ulna for the space of one inch above the line of the radio carpal articulation. Now, fractures ordinarily take place at a point which is below the level of this line, and any displacement, the result of fracture, cannot readily affect the breadth of the interosseous space, placed above the line of the fracture.
Cooper, who asserts that in this fracture a very powerful extension is required to bring the broken ends of the radius into apposition.