Part 43

§ I.

1. The rotula, a sort of bony production of the sesamoid kind, attached to the tendon common to the extensors of the leg, represents a moveable pulley, intended to slide on that formed by the separation of the condyls of the os femoris. It protects the joint which it covers, and, in point of structure, use, and situation, greatly resembles the olecranon, from which it differs only in this, that, instead of being a continuation or process of the tibia as the olecranon is of the ulna, it is only attached to that bone by a strong and thick ligament which is inserted into its tuberosity. Hence it follows, that between the injuries of the one and the other, there must be a great analogy: and indeed most of the signs characteristic of fractures of the olecranon, are characteristic also of those of the rotula, and the treatment which, in such cases, is suitable for the former, differs but little from that required by the latter.

§ II.

OF THE VARIETIES AND CAUSES.

2. Fractures of the rotula may, in general, assume any direction, transverse, longitudinal, or oblique: but the first kind occurs in practice much more frequently than the others; and so great indeed is the disproportion, that it has almost exclusively attracted the attention of authors, in the numerous forms of apparatus invented to retain the fragments.

3. A shattering of the bone, the effect of a violent blow; a contusion; an echymosis; an effusion of blood into the adjacent soft parts; one or more wounds of the soft parts, with or without an opening into the joint; a swelling, the degree of which varies greatly, according to the state of the fracture, and the disposition of the subject, but which is constantly present; a double division of the bone, one of which, being longitudinal, forms an angle with the other, which is transverse; and a concomitant fracture of the condyls of the os femoris, or of the tibia: such are the varieties and complications, of which the fracture under consideration is susceptible.

4. But this fracture may be produced in two modes. 1st, by the action of external bodies: 2dly, by that of the extensor muscles. The first mode of division takes place in falls on the knee, or when a body in motion strikes against it, and, in this case, there is no counter-stroke, the rotula being too small for such an occurrence, and always sustaining the fracture where it receives the blow. In the second, the fall is only subsequent to the fracture, and, as Camper has well observed, is most frequently the effect of it. For instance, the line of gravity of the body is, by some cause, removed behind it; the anterior muscles contract themselves to bring it forward again; the extensors act on the rotula; it is broken, and a fall ensues. Again, the leg is suddenly thrown into a state of violent extension; the extensors act with great force; a fracture is the consequence, and the patient falls. A soldier once fractured his rotula in kicking at his serjeant; thus the olecranon, in like manner, has been broken by throwing a stone. A man, in the Hotel-Dieu, fractured the rotula of each knee, in the operating room, by means of convulsive motions, produced by the operation of lithotomy.

5. The action of external bodies, can alone produce a longitudinal fracture, as when a person falls on a sharp projecting piece of timber: but this may also produce a transverse fracture. On the other hand, muscular action can never give rise to any but the latter kind, since the direction of this fracture is at a right angle with that of the extensors. A fracture resulting from the action of external bodies, is oftentimes accompanied by a wound, a contusion, or a shattering of the part (2); a fracture, arising from muscular action, is always simple, except as to a swelling around the joint. The latter cause may, instead of fracturing the rotula, rupture the common tendon of the muscles, or, what is more common, the inferior ligament. Desault has seen many examples of this: Petit has also observed several, and Sabatier has sometimes met with them. External violence seldom produces this double accident.

§ III.

OF THE SIGNS AND THE DISPLACEMENT.

6. In longitudinal fractures the diagnosis is always accompanied with more or less difficulty, because the extensor muscles, drawing by their contractions the two fragments equally upwards, and the inferior ligament holding them equally down, tend to keep them in apposition, and to prevent them from separating. Sometimes also the ligamentous production which covers the rotula, remains entire and serves to keep the fragments together. It will be necessary, therefore, should the existence of such a fracture be suspected, to move the two sides of the rotula in opposite directions, by pressing them to the right and to the left, in order to arrive at certainty on the subject. Should a wound exist, as is oftentimes the case (5) the diagnosis is less difficult.

7. If the division be transverse, the diagnosis becomes then as plain and easy, as it is difficult and obscure in cases where it is longitudinal. In such a case, a considerable separation or space exists between the two fragments, sensible to the touch, when the hand is placed on the knee. In this separation, the fragments are not displaced by the same means. The superior fragment being attached to the extensors, is drawn upwards with great force by these muscles, the action of which the rotula no longer resists. The lower fragment, on the other hand, being attached only to the inferior ligament, is not moved by any muscle, and cannot be displaced in any other way than by the motions of the leg with which it is still connected.

8. Hence it follows, 1st, that, in a state of extension, the separation is the least possible, because it is then produced on the part of the superior fragment only; 2dly, that in a state of flexion it is greatest, because then both fragments concur alike in producing it; 3dly, that it may be increased or diminished by varying the degrees of flexion.

9. This fracture is further characterized by the following circumstances, namely, a practicability of moving the fragments transversely in opposite directions, and of producing, by that means, some degree of crepitation, provided they be first brought close together; by the pain which accompanies these motions; by the swelling common to every kind of fracture of the rotula, and which, if very great, may involve the other signs in more or less uncertainty; by a difficulty of standing; and an almost entire loss of the power of walking, in consequence of the extensors being no longer able to communicate motion to the leg, unless when the fracture exists very low down, near to the inferior ligament.

10. The touch will always discover in what part of the bone the fracture is situated, which, if it be oblique, will partake more or less of the characters of the longitudinal or the transverse, accordingly as it approaches to the one or the other.

§ IV.

OF THE PROGNOSIS.

11. Many authors have pretended that fractures of the rotula cannot be cured, and it even appears that the Academy of Surgery adopted this opinion, on receiving a memoir from a Flemish physician, which contained several facts tending to establish that principle. But what do these facts prove? That in some particular cases, reunion did not take place, but they do not show that this was owing to the nature of the fracture.

12. But, what, in such cases, could prevent a cure from taking place? The structure of the rotula differs, say they, from that of the other bones. Now, admitting this difference of structure to be real, it certainly approaches to the structure of tendons to which indeed it bears a strong affinity. But, who does not know, that, when tendons are divided, they unite as readily as bones? Besides, is not the power of reunion common to every part endowed with life? I have already shown, when treating of other fractures that communicate with joints, what credit is due to those hypotheses so often revived but never confirmed, nay even clearly proved to be unfounded, such as, an effusion of callus into the joint, a failure of reunion from a want of periosteum on the posterior part of the bone, the synovia diluting the matter of callus, and thus preventing it from being duly prepared, &c.

13. The inflammation of the articulating surfaces and of the ligaments around the joint, ought to have more influence in constituting an unfavourable prognosis, than any circumstance that authors have mentioned. But experience proves, that, when judiciously treated, these fractures are not accompanied by that accident, and even that the swelling, which for the most part attends them, always yields more or less speedily, when a bandage, uniformly applied, presses equally on all parts around the joint, and thus forms a kind of discutient, while at the same time it retains the fragments.

14. Pare, Fabricius of Hilden, and a number of other writers, have pretended, that some degree of lameness must always be the consequence of this fracture. But, from what causes must this lameness so certainly arise? Is it from a want of reunion in the part? I have already shown (11 and 12) that this apprehension is wholly unfounded. Is it from an anchylosis? This accident cannot take place, except either in consequence of inflammation occurring in the articulating surfaces, (and I have already shown how that may be avoided, 13) or of a stiffness in the ligaments, and I shall hereafter make it appear that that may be readily prevented by motion. Is it from the fragments being drawn asunder, and in that state united by an intermediate substance of too great an extent? I shall prove, that a bandage properly constructed, is always sufficient to keep these fragments in contact.

From these considerations it appears, that writers have, in general, without sufficient cause, given an unfavourable prognosis, in relation to fractures of the rotula, which have, indeed, a great affinity to other affections of the same kind.

§ V.

OF THE REDUCTION AND THE MEANS OF MAINTAINING IT.

15. I have already observed (7), that the causes of the separation of the fragments are, as far as respects the upper one, the contraction of the extensor muscles; and, in relation to the lower one, the flexion of the leg; whence it follows, that the means of preserving contact between these fragments are 1st, all those that are calculated for the prevention of muscular action; 2dly, such as may keep the limb in a state of permanent extension. Hence two leading curative indications must be fulfilled by the bandage constructed for fractures of the rotula: the last of these indications presents in general but little difficulty; but, with regard to the other, the case is different. To fulfil the latter, it is necessary first, to weaken the contractile force of the muscles, and by that means diminish the effort which they make to draw the superior fragment upwards; and then, to oppose to them a proper mechanical resistance, which, by acting in a direction the very reverse of that in which they act, may countervail their efforts.

16. But the force of contraction is diminished, 1st, by throwing the muscular fibres into a state of relaxation; this end is best attained by bending the thigh on the pelvis: 2dly, by making compression over the whole limb, by means of a circular bandage, which, by confining the muscles, tends to restrain and weaken their action. Thus it is known that the advantage of the bandage employed to unite transverse wounds, consists chiefly in that compression which, by diminishing muscular action, prevents the retraction of their edges. Another advantage resulting from the bandage in this case is, that it prevents the swelling of the limb.

17. As to the mechanical resistance, which must act in a direction opposite to that of the contraction of the muscles, and, by that means, prevent the displacement of the superior fragment, it cannot, in the present case, be of the same nature as in fractures of the thigh, the clavicle, &c. where permanent extension is practised. The superior fragment offers too small a purchase for any extending forces to act on. This resistance must be made, then, by placing some body above this fragment, and retaining it in that situation with a force sufficient to hinder the fragment from rising upwards: such as a few turns of a roller drawn tight, a bit of leather, some hollow compresses, &c.

18. It is evident from the foregoing principles, that every bandage intended to retain a transverse fracture of the rotula, ought to be calculated to maintain the following state of things: 1st, the extension of the leg on the thigh; 2dly, the flexion of the thigh on the pelvis; 3dly, a uniform compression over the whole limb; and, 4thly, some mechanical resistance properly secured above the superior fragment: the three last expedients relate to the displacement of that fragment alone; while the first has a relation to that of the lower one. Let us examine whether or not the bandages, hitherto employed by different authors, be calculated for these purposes.