MEMOIR IX.
ON THE LUXATION OF THE FORE-ARM.
§ I.
1. The solidity and security of joints are increased in proportion as the extent of their motions is diminished. This inverse proportion of these two properties to each other, is in a particular manner remarkable in the upper extremities, where the connexion of the humerus with the scapula, of the fore-arm with the humerus, and of the bones of the wrist among themselves, appear, in regular gradation, to acquire the one as they lose the other: hence, their predisposition to luxations is extremely different. We will examine those to which the fore-arm is subject.
2. An angular ginglymus unites to the humerus the bones of the fore-arm, which are again connected with each other by a double lateral ginglymus. Eminences and depressions, reciprocally receiving and received, constitute the first kind of articulation, where, proceeding from without inwardly, we find, 1st, the small head of the humerus, entering or rather joining the upper articular cavity of the radius, which moves on it: 2dly, the external groove of the humerus, receiving the rim of the same cavity of the radius: 3dly, a projection which, rising from the external edge of the coronoide[19] cavity, extends to the corresponding edge of that of the olecranon, and is received into the external depression of the sigmoid cavity:[20] 4thly, the large groove of the humerus, receiving the middle eminence of this same cavity: 5thly, a considerable projection, obliquely applied to the internal depression which receives it.
3. These numerous connexions secure the solidity of the joint, which is still farther strengthened before by the coronoid apophysis, together with the fleshy and tendinous extremities of the biceps, and brachialis muscles, and by the olecranon behind; at the inferior part, by the anconeus; on the sides by two ligaments which descend from the two tuberosities, and strong muscular fasciæ running from the same parts. The whole articulation is also surrounded by a thick capsule, strengthened by numerous accessory fibres. With such powers of resistance, how can this joint suffer a luxation? Yet next to that of the os humeri, it is perhaps most frequently subject to this accident.
§ II.
OF THE KINDS AND CAUSES OF DISPLACEMENT.
4. Writers have admitted in general four kinds of displacement; backward, forward, outward, and inward. But all these are not alike frequent, as is proved by experience, and demonstrated by the relative situation of the parts.
5. In a backward direction the olecranon and the radius may pass up behind the humerus, as the coronoid apophysis offers but little resistance in consequence of its slight curvature. On the other hand, the kind of hook formed by the olecranon, prevents it and the radius from passing before the lower articulating extremity of the humerus, and therefore, without a fracture of the olecranon, a luxation in that direction is impracticable: at the sides, the two lateral ligaments, but more particularly the reciprocal joining or interlocking of the uneven articulating surfaces, present almost insurmountable obstacles to luxations laterally. Whence it follows, that luxation backward is much more frequent than the others; compared to lateral luxations, it is, at least, in the proportion of ten to one: with luxations forward, no comparison can be made; neither Petit nor Desault having ever met with such.
6. An external force produces the whole of these luxations, but according to each, this force must vary. In a fall sideways, suppose the hand be applied to the ground, with the arm extended, to save the body. It is evident that the resistance of the ground will tend to make the bones of the fore-arm pass upwards over the humerus, while the weight of the body pushing that bone downward and forward, will make it glide over the coronoid apophysis. Thus, the capsule, being distended before by the humerus, and behind by the bones of the fore-arm, will give way in one or the other place, or in both, as Desault observed in a man, who fell on his side, as he was carrying a heavy load: the weight of the body increased by the load, had such an effect, that the bones overlapped each other nearly two inches.
7. It appears from this, that a state of extension is the position most favourable to a displacement backwards; a doctrine by no means conformable to that of most practitioners, who consider a state of flexion as necessary to the accident. But, then, in what direction should the fall take place, in order that the olecranon may pass upwards? Applied as it is against the side of the cavity that receives it when the arm is extended, would not this apophysis prevent such passage? Whatever may be the mode of displacement, the olecranon, in passing upward and backward, may incline a little to the one or the other side.
8. I have already said, that without a fracture of the olecranon, no luxation forward can occur (5). But what cause can act with sufficient power on the parts to produce both accidents at the same time? It would be necessary that a fall which had produced a fracture should be succeeded by another fall; but in such a case, the fore-arm would be half-bent, and it is in a state of extension alone (7) that the luxation can take place.
9. Lateral luxations, that is, luxations at the sides have been divided into complete, when the two articular ranges of the arm and fore-arm, have lost their connexion entirely, and incomplete, when only one bone or one part of a bone has been separated from its natural connexion with the humerus. But what cause can act with sufficient force to produce the first kind of luxation, namely, that which is complete? In such an accident so great would be the extent of the wreck and ruin of the part, that without doubt amputation would be the only resource.
10. The second kind of lateral displacement is the result of a stroke which forces violently the extremity of the fore-arm outward or inward. A footman, says Petit, in falling from a carriage, had his arm entangled between the spokes of the wheel, and suffered in consequence a luxation outwards. Another produced one inwardly, by being thrown from his horse, and falling with his arm under him, on rough ground. Strokes of this kind may, as that author remarks, vary in a singular manner. But, in general, in all of them, the fore-arm must represent a lever of the first kind, where the power acts on the end next the hand; the resistance being in the joint, and the fulcrum in the middle.
§ III.
OF THE SIGNS.
11. To form an idea of the signs or appearances of a luxation backwards, let us examine, for a moment, the natural situation of the olecranon, and the condyls of the humerus. As these eminences are easily felt under the skin, a knowledge and recollection of their situation will serve as a standard of comparison, to judge of the changes they experience in a luxation. When the fore-arm is extended, the olecranon is on a level with the internal condyl, and a little above the external one. In a state of flexion, it descends below this level, and is then farther below the internal than the external condyl. In either situation, it is nearer to the first than to the second, the radius separating it from the latter.
12. But, when a luxation has taken place, this apophysis, still remaining on a level with the two condyls, even although the fore-arm be half-bent, is oftentimes separated from the internal one, and driven towards the other: a preternatural protuberance announces this change of position of the olecranon. The coronoid apophysis, whose posterior surface glides in the large groove of the humerus, corresponds to this groove now only with its anterior surface: sometimes the olecranon cavity[21] receives its extremity. The radius passes backward over the small head of the humerus. At the fold of the arm, a transverse protuberance, more perceptible on the internal side, announces the presence of the displaced articular extremity of the os humeri. Over this extremity are reflected the biceps and the brachialis muscles in a state of violent distension. These muscles, greatly irritated by such distension, continue in a state of habitual contraction, in consequence of which, they keep the fore-arm half-bent. Nor can the anconeus muscle, which is necessarily relaxed, act so as to prevent this semiflection. Severe pains would be the consequence of attempts to extend the fore-arm; the limb is in a state of pronation; yet I find among the cases collected by Desault, several examples where supination existed; this state is explained by the relaxed condition of the pronator muscles. At the level of or opposite to the coronoid cavity is a depression or hollow manifesting the absence of the apophysis of that name.
13. Should chance give rise to a luxation forward, an anterior projection of the two bones of the forearm, and above all, of the coronoid eminence, a depression corresponding to the olecranon cavity, the extremity of the humerus carried backward and downward, the rigid extension of the fore-arm, a protuberance behind formed by the fractured olecranon (5), and severe pains, necessarily resulting from attempts to bend the limb, &c. would constitute the principal characteristic signs of the displacement.
14. In lateral luxations, a protuberance at the internal or external side of the articulation, always shows of what kind it is. If the displacement be to the internal side, the olecranon is then situated behind the small tuberosity: the middle protuberance of the os humeri bears on the radius, which is sometimes placed even behind the internal articular eminence of that bone, which then rests on the external depression of the great sigmoid cavity. Hence, as Petit judiciously observes, arises the direction of the fore-arm outward, the above eminence presenting a manifest obliquity in that direction. In this luxation, the ulna has been known to lose entirely its connexion with the humerus, and the radius to be brought into contact with the internal condyl of that bone. This is what some authors call a complete luxation. Others reserve that name for cases where, the two articular ranges have lost their correspondence or apposition entirely.
15. In a luxation outwards, the olecranon corresponds to the external condyl; the middle projection of the humerus, to the internal depression of the great sigmoid cavity; the small head of this bone, to the external depression; the radius projects outwards; and the humerus makes a protuberance inwardly.
16. After all, these changes of situation vary remarkably, and it belongs to theory rather than practice, to trace their history, with precision. In general, luxations outwardly happen more frequently than those inwardly, a circumstance which is fully explained by the structure of the joint. In both, the lateral ligaments are almost always lacerated.
A swelling more or less considerable accompanies all the different kinds of luxation, and is sometimes carried so far as to involve the diagnosis in great uncertainty, particularly when the displacement is not very great. This phenomenon (the swelling), seems, in general, to correspond, in a direct ratio, to the force with which the articulation resists. Indeed the violence, and consequently the irritation, are always in proportion to the resistance of the parts.
§ IV.
OF THE REDUCTION.
17. The means of reduction vary according to the different kinds of displacement. They are all, however, founded on nearly the same principles, and it will be easy to form proper ideas of them, when we shall have given an account of the means necessary to be employed in luxations backward, of which the others are only modifications.
Here genius seems to have been as prodigal of resources, as nature has been of obstacles. Indeed, to accomplish the reduction, we sometimes see the surgeon placing his elbow in the fold of the affected arm, interlocking his fingers with those of the same limb, and, then, bending with his whole force, both his own fore-arm, and that of the patient, to effect at the same time extension, counter-extension, and reduction or conformation: at another time we see him fixing the fold of the injured arm against some resisting body, such as a bed-post; and while an assistant, then, pushes the displaced olecranon against this body, he himself, pressing on the shoulder with one hand, and grasping the fore-arm with the other, bends it forcibly, in order, by that means, to produce a replacement: again, a body of some size, being placed in the fold of the arm, serves as a fulcrum, on which the fore-arm, being suddenly flexed, moves and acts like a lever of the first kind, of which the power, being applied at the extremity next the hand, draws it backward and upward, and by that means pushes in a contrary direction its luxated end, where the resistance is made. On some occasions, the fore-arm of the diseased side, bent at a right angle, is placed on a horizontal table, and, while the lower extremity of the humerus is thus resting on the table, the surgeon pushes it backward with one hand, and with the other, taking hold of the extremity of the fore-arm, draws it in a contrary direction.
18. The ancients employed the three first modes. Pare has had engravings of them made: Scultel has also given figures of them as practised by Hippocrates. The Arabians knew of no other modes, nor did their descendants, who were only compilers from them. The practitioners of our own day still continue their use. But, in general, they are chargeable with the numerous inconveniences and faults of producing intense pain, of not being completely under the direction of the surgeon, of bringing the point of luxation too near to the place on which counter-extension is made, and of bruising and doing violence to the parts: nor do they disengage, by means of previous extension, the luxated ends of the bones, to facilitate their replacement in their natural situations.
This last charge is not applicable to the last of the processes proposed by Petit. But, here, the extending forces are most commonly insufficient; the surgeon, having both his hands engaged, is not able to act on the joint to assist in the replacement: and the counter-extension made is too near to the point of luxation.
19. In common cases, Desault employed a method as simple and more efficacious, which few writers have recommended, and none have described with accuracy.
The patient is, indifferently, either seated or standing. The fore-arm being half-bent, an assistant takes hold of the extremity next the hand, to make extension; another, to make counter-extension, takes hold of the humerus a little below its middle, with both hands, the fingers crossing before, and the thumbs behind. The extension is made gradually, and when it begins to move the olecranon, and draw it from the place it accidentally occupies, the surgeon, to aid in the reduction, grasps the lower end of the humerus with both hands, crosses his fingers in the fold of the arm, applies his thumbs to the olecranon, and drawing the first backward, pushes at the same time the latter forward; thus, he favours, on the one hand extension, and on the other counter-extension, and in that way finishes the reduction.
20. This method is most commonly practised with success, in recent luxations, where we have oftentimes seen the reduction effected at the Hotel-Dieu, by the simple process of pushing, as just mentioned, the olecranon forward, the humerus being held backward, without any previous extension, while the fore-arm was merely supported by the assistants.
21. But the luxation being oftentimes of long standing, presents very great difficulties. What means must then be employed? It is an established principle, that the force with which a power acts, is in direct proportion to its distance from the point of resistance. Augment this distance, and the extending forces, being doubled and even trebled, will more easily dislodge the luxated extremity. But this indication is fulfilled, by two long straps, formed each of a towel folded several times, one of which is fixed above the wrist, and the other round the humerus a little below its middle. Extension is then made at their extremities, and is almost always sufficient, when aided by skilful efforts of the surgeon (19), to accomplish the reduction. The application of a strap round the humerus is never necessary, unless when the resistance is very great; because, in counter-extension, it is requisite only to withstand or bear against the efforts of extension, but not to act in a contrary direction.
22. But in cases of this kind, the strap, placed, as we have directed, round the lower part of the humerus, has sometimes the disadvantage of compressing too much the brachialis and the biceps muscles, and thus preventing them from acting; this inconvenience is particularly felt in old luxations, where great force is employed; for, the more active then the contraction of these muscles is, the more it will aid the surgeon in his efforts to draw the bones into their natural situation, when once disengaged by extension, from that which they had accidentally occupied. If, in such a case, we impede the contraction of these muscles, how can they fulfil this office?
23. It was this which, in certain cases, induced Desault to place his counter-extension under the armpit, by means of a strap passing, as in the luxation of the humerus, over a ball previously fixed in this hollow, and crossing, not on the top of the opposite shoulder, but behind that of the diseased side. By this contrivance the humerus was drawn or rather held back, by a force acting perfectly in the line of its direction. But is not this force situated too near to the centre of motion? The strap for making extension, fastened at the wrist, answers very well, as has been already mentioned (21).
24. Should the luxation be forward, the extension must be directed according to the state and position in which the fore-arm is found, which is always extended. The hands of assistants alone (19), or straps (21), may then serve to make the extension, which the surgeon must aid, by grasping, in a direction the reverse of that in the preceding case, the lower extremity of the humerus, that is, by crossing his fingers behind, and placing his thumbs on the coronoid apophysis, to push it downward and backward.
25. The strap for counter-extension, would in such a case, always afford the greatest advantage, by being placed exactly as in luxations of the humerus, that is, by running to, and crossing on, the opposite shoulder; the direction or course of the fore-arm, which is necessarily in a state of extension, sufficiently explains this; finally, the reduction of the luxation must be succeeded by the reduction of the olecranon (5), and by the application of a proper apparatus to retain the whole.
26. The reduction of lateral luxations, differs but little from that of luxations backwards. The displaced extremities must be first dislodged by previous extension (19). The surgeon, then, taking hold of the lower part of the arm, places his fingers before, and with his thumbs, crossed on the olecranon, pushes that apophysis forward and inward, if the displacement be outwardly, but forward and outward if it be inwardly. Does the case prove very difficult, recourse must be had to the other means (21 and 23). The hands of the surgeon must still, according to the direction of the displacement, assist the extension made by the straps.
§ V.
OF THE MEANS OF MAINTAINING THE REDUCTION.
27. Luxations of the fore-arm have, oftentimes, a great disposition to occur anew, after having been reduced, whether they be recent, or of long standing. Extension readily dislodges the olecranon and the radius, and replaces them perfectly in their natural situation; but if any thing interrupt them, the displacement is sometimes immediately renewed: suppose the parts even remaining in contact, the slightest motion may derange this contact, and give rise to a necessity for a new reduction, more difficult, oftentimes, than the first. Hence it is always prudent to employ a retentive apparatus for some time.
28. But, on what principle and for what purpose ought it to be applied? The motions communicated to the fore-arm by external bodies, but, more particularly, the action of the muscles inserted in the bones that have been reduced, are here the causes of their displacement. Hence, 1st, to render the limb immoveable; 2dly, to push the articular ends of the bones in a direction opposite to that in which they are drawn by the muscles, and have a tendency to be displaced: such is the twofold indication of the bandage; an indication not fulfilled by the kind of bandage and the sling which Petit proposed, and which leave the arm free to move, and the muscles free to act.
29. Desault employed the following apparatus: 1st, The arm and fore-arm are first covered by oblique turns of a roller, intended both to protect them from the impression of splints, and to diminish the power and action of the muscles, by the pressure made on them: 2dly, Behind the olecranon is to be placed a thick compress, designed to retain it downwards, and which must be secured by a strong splint, situated behind, and curved at the elbow, to accommodate it to the flexion of the fore-arm: 3dly, On the sides are placed two other splints, chiefly necessary in lateral luxations: 4thly, The whole is to be secured by the remaining part of the roller, by which the arm and fore-arm are already covered.
In this bandage, the immobility of the arm is secured by the splints, while the olecranon is pushed by the compress, in a direction the reverse of that of its displacement. But these circumstances constitute the double indication that was to be fulfilled (28).
30. The period at which these means may be dispensed with, is undetermined. It belongs to the surgeon to examine and ascertain, when the natural connexions of the joint are sufficiently confirmed. Then motions, at first gentle, are to be impressed on the limb; being afterwards gradually increased, they remove by degrees that stiffness, which usually follows a dislocation, particularly an old one. But if it has existed too long, to give the limb motion, is then the only resource: the new attachments or adhesions, contracted by the articulating surfaces in their displaced state, render reduction impracticable. We must then confine ourselves merely to increasing the extent of the motions, which the displaced fore-arm is yet capable of performing.
31. There is, in general, all other things being favourable, a hope of accomplishing the reduction, till the end of the second month after the accident. Desault succeeded in it, at even a later period. What trouble or hardship is it, at last, to try extension? Should no other end be gained, but merely to bring the bones nearer to their natural cavities or situations, even without actually replacing them, this will aid their movements, the extent of which is inversely proportioned to their distance from these cavities.