14. Most of the foregoing signs, taken in the opposite sense, would characterize a luxation of the radius backward, should it occur: such, for example, as a forced supination of the limb, an inability as to pronation, the pains that would result from this movement if performed by force, the tumour formed anteriorly by the extremity of the ulna, the posterior situation of the large head of the radius, and the abduction of the wrist.
15. The dead body, in which Desault observed this kind of displacement (9), being dissected with care, exhibited in the articular parts, the following diseased state. The tendons of the flexor muscles, pushed outwards, adhered to one another and to the skin; a substance of a cellular texture filled up the sigmoid cavity of the radius, and occupied the place of the cartilage which naturally invests it: the inter-articular ligament, which passes between the ulna and the os pyramidalis, scarcely touched the head of the ulna, having followed the radius backwards; and the head of the ulna, situated before the sigmoid cavity of the radius, rested on one of the ossa sesamoidea, to which it was attached by a capsular ligament.
§ V.
OF THE REDUCTION.
16. Extension so important in the reduction of other luxations, renders scarcely any service in this: impulsion alone answers the purpose. If the displacement be forward, it is reduced in the following manner: The patient sits or stands indifferently; the latter position, however, has sometimes this advantage over the former, that by placing the part to be operated on more on a level with the hands of the surgeon, it gives him both more readiness and more force in his motions: one assistant supporting the elbow, separates the arm a little from the body; while another taking hold of the hand and fingers, gives them also an equable support.
17. The surgeon grasps the extremity of the fore-arm, with both hands, one placed on its internal, and the other on its external side, so that his two thumbs may meet before, between the ulna and the radius, and the fingers behind. He then exerts himself to separate the two bones from each other, by pushing the radius backward and outward, and retaining the ulna in its place; in the mean time the assistant who supports the hand, endeavours to move it in the direction of supination, and consequently to draw the radius, with which it is connected, into the same state. Being thus pushed in a direction opposite to that of its displacement, by two forces, the one exerted directly on it, and the other acting indirectly, the radius is forced outwards, and the ulna, returning through the opening in the capsule, is replaced in the sigmoid cavity.
18. Should a luxation of the radius backwards ever occur, the same process executed in an inverse direction, would serve the purposes of reduction. The surgeon with his fingers would have to press the extremity of the radius forward and inward, while a forcible pronatory movement impressed by the assistant on the hand intrusted to him, would favour the effort and finish the reduction.
19. The disappearance of the signs (12...14) of the luxation bespeak its reduction. In general the pain is entirely removed; sometimes a perceptible sound, or report, caused by the passage of the bone through the opening in the capsule, announces the replacement.