Professor Smith, who has investigated labo riously the anatomy of the bones in this injury, says he has discovered nothing to invalidate the truth of the general proposition first main tained by Voillemier, namely, that when the radius is broken within an inch of its lower extremity, the direction of the fracture is usually transverse; but we find that he differs entirely from this last-named author upon the doctrine of the fracture of the radius in ques tion, being one by impaction. It is very true, he says, that in every instance of the ordinary fracture of the carpal extremity of the radius, which he had an opportunity of examining anatomically long after the occurrence of the injury, he found upon making a section of the bone, from before backwards, a line of com pact tissue continuous with the posterior wall of the shaft, extending to a greater or less dis tance into the reticular texture of the lower fragment ; but he cannot agree with Voillemier, that this appearance affords evidence of im paction of the upper fragment into the lower. In the only recent specimen Mr. Smith had an opportunity of examining, the lower fragment was displaced backwards, the superior pro jecting one-eighth of an inch in front of it. There was no impaction whatever in this re cent specimen, of either fragment into the other, nor any line of compact structure pene trating the reticular tissue of the lower frag ment.
If the doctrine of impaction were true, the shortening of the radius in cases of fracture of its lower extremity, should be much greater than it ever is, for there is a second cause of shortening in operation, i.e. the alteration in the direction of the articulating surface, in consequence of which the posterior surface of the radius (naturally longer than the anterior) becomes the shorter of the two. Now, if to the degree of shortening produced by this cause we add that arising from impaction, we should have an amount of shortening much greater than ever occurs in the case of Colles' fracture ; indeed, after adducing other argu ments against the theory of Voillemier, as to this being a case of fracture by "penetration," Mr. Smith further remarks, that as long as the ulna remains unbroken and the ligamentous connexion between the two bones uninjured, it is scarcely possible for either fragment to penetrate the other, even to the extent of half an inch.
We agree with Velpeau, Smith, &c., in thinking that in this injury, Colles' fracture, there is scarcely any diminution of the trans verse diameter of the forearm. The cylin droidal form which the arm acquires being owing partly to an effusion among the flexor tendons, but principally to the increase of the antero-posterior diameter of the forearm at the seat of the fracture, consequent on the back ward displacement of the lower fragment.
I have never seen the case, spoken of by many, of transverse fracture of the radius, with displacement forwards of the hand and lower fragment, which accident is said to be pro duced by a fall on the back of the hand.
Fracture of the lower extremity of the Ulna. — A fracture of the lower extremity of the ulna is rather a rare accident, because, per haps, of the great elasticity of this long and slender bone, and the mobility of its lower end, by which it, as it were, eludes the force which might otherwise cause its fracture. In deed the ulna, it will be recollected, is not directly connected with the hand as the radius, the " manubrium manus," is : and hence, when a patient falls on the palm of the hand, the whole force of the weight and im pulse are sustained by the radius; but if this last bone gives way, and a transverse fracture occurs, with displacement backwards of the hand and lower fragment, then, as a secondary consequence, a fracture of the ulna, near the wrist-joint, may follow. In the vast majority of cases, however, of fracture of the radius close to the wrist, which occur, for example, in Colles' fracture, the ulna remains unbroken.
Fracture of the lower extremity of the ulna may also be the effect of direct violence.
When the ulna is broken alone, without being accompanied by any simultaneous frac ture of the radius, it may be recognised by the pain felt by the patient when direct pressure is made on the broken part of the ulna, and by the difficulty he experiences whenever he attempts to pronate or supinate the forearm. When the surgeon takes hold of the lower fragment of the ulna, and moves it backwards and forwards, crepitation can be felt.
Fracture of the lower extremity of the ulna is an accident which requires much attention from the surgeon, as sometimes, if the sepa rated fragment be small, as, for example, con sisting merely of the styloid process of the ulna, no union may occur, and permanent weakness of the wrist-joint may follow.
Disjunction of the lower Epiphysis of the Radius. — This must be considered rather a rare accident ; it is, however, occasionally to be met with ; and the history of the art of surgery furnishes us with well-marked ex amples of it, as the three following cases sufficiently prove :—