The Rubbing Of The Surfaces Against One Another

The Rubbing Of The Surfaces Against One Another gradually wears down their fibroid covering of callus; it gradually, also, renders them smooth, and produces an ivory-like condensation of their spongy tissue. Hence, when the covering is entirely removed, two bare, smooth surfaces of bone, glistening and polished like ivory, are left to articulate together.

The false joint thus produced varies in its form. Sometimes two tolerably flat and even surfaces are applied to one another; at other times, one of the fractured surfaces is slightly hollowed out into an articular cavity, and the other forms an articular head. Accordingly, at one time the stump of the neck is rounded off, and fits into the fractured surface next the head, which has been a little excavated; while at another time, after absorption of the neck, the head of the bone moves in a large and slightly concave articular surface, hollowed out between the two trochanters. It is worthy of remark, that in the latter case the line of the insertion of the capsule recedes to an extent corresponding with the absorption of the neck, and that the size of the articulation is thereby increased.

In a specimen of fracture of the neck of the femur, in the Museum at Vienna, a fragment of the head of the bone having fallen upon the fractured surface of the neck, and become bound to it by ligamentous tissue, articulates by its external and still cartilaginous surface, with the fractured surface of the rest of the head.

The fragments are in some cases, uneven and serrated, and become wedged into each other at the time of occurrence of the fracture; their surfaces then unite together by fibroid callus.

In a more frequent instance of this kind of accident, the neck of the bone becomes implanted in the spongy tissue of the great trochanter.

While these changes are going on in the fragments of the bone, the capsule of the joint becomes swollen, and its contents more or less turbid: it also frequently forms adhesions, of a cellular or ligamentous nature, with the fibrous investments of the neck of the bone, as well as with the fibroid callus upon the fractured surfaces.

In some extremely rare instances the fragments do unite within the capsule by means of bone; it is a mode of union which is almost always very slowly accomplished, and in which there is considerable shortening of the neck of the bone. That fracture, too, in which the neck of the bone is driven into the spongy tissue of the trochanter has been seen repaired by bony callus.

The rarity of union of intra-capsular fracture of the neck of the femur by bone, when the accident is so frequent, has for a long time elicited much research into the reasons why the customary mode of repair does not take place in this instance. Many reasons have been assigned for it, but it must be acknowledged that none of them is satisfactory. Amongst them are the following: a. In general, the advanced age of the persons in whom the accident occurs; and, in particular, a state of atrophy of the skeleton.

B. Insufficient nutrition of the separated head of the bone, by the few vessels that enter it through the ligamentum teres.

r. The presence of synovia and other effusions between the fractured surfaces.

δ. The difficulty of securing and maintaining proper adaptation of the fragments to each other, and the want of some permanent pressure to effect it: and, lastly, e. Want of rest.

No one of these reasons, as have been stated, sufficiently explains the matter. That no reaction takes place in the fractured neck of the femur in an aged and decrepit person is intelligible, because the same fact is very often observed in such persons in fractures elsewhere: but this does not explain why the formation of callus should be so backward generally, even under less unfavorable circumstances, and why the proper changes in it should be so commonly frustrated. This consideration derives additional importance from the fact, that in the majority of cases, and even as a rule, no bony union takes place in fractures of any bony structures which are enclosed within an articular capsule.

On more closely examining the subject, the principal conditions appear to be two: the first is, that no primary or provisional callus whatever is formed: and the second is, that the secondary or definitive callus is arrested in its development at the stage of fibroid (ligamentous) tissue. It is the want of the first callus that, for the most part at least, arrests the growth of the later callus, and commonly leads to the formation of a false joint. The only object now, therefore, is to determine the reasons why no provisional callus is thrown out.

The following circumstances appear to me to be the chief impediments:

1. The small amount of vascularity possessed by the portion of the fibrous capsule of the joint, which occupies the place of periosteum; to which, as well as to the density of its structure, and, more especially, to its close adhesion to the bone, it must be attributed, that no exudation, preliminary to the formation of the provisional callus, takes place between the bone and its fibrous investment.

2. But the principal cause is the small share which the soft parts take in the reactionary process: they are placed at some distance from the seat of fracture; and the distance is further increased by distension of the capsule with exudation: in addition to this it happens that the exudation, whether in consequence of its being diluted with synovial fluid, or from its original quality, almost never becomes organized to bone.

It is, therefore, the want of the first callus and of that firm fixing of the fragments which should be effected by it, that really prevents any union of the fragments by bone, that interferes with the production of the secondary callus, and leads to the formation of a false joint; and the influence of this deficiency is, in ordinary cases, greater in proportion as the difficulties enumerated under the head δ and t are brought into action.

However constant the failure in the production of callus at the seat of fracture itself, yet now and then the growth in question does occur in other places, when an energetic reactionary process springs up around. Thus, sometimes shallow cup-like masses of callus are developed on the enlarged capsule of the joint; in other cases, especially those in which the neck of the femur is driven into the substance of the trochanter, callus is poured out upon and around that process; and in some other rare cases the head of the bone unites with the acetabulum by a deposit of callus, which produces atrophy of the cartilage covering the bones, and takes its place.

Fracture external to the capsule is generally repaired by bony union, but sometimes a false joint is formed. Even in the former case, the union is attended with some deformity, either displacements of the fragments and shortening of the extremity, or shortening, and a more horizontal position than natural of the neck of the femur. Sometimes, too, the neck is driven into the spongy tissue of the upper end of the femur.

Fractures of the neck of the femur, as I have already mentioned, are of frequent occurrence. The principal predisposing causes are advanced age and senile atrophy of the bones. To these may be added, the depression and more nearly horizontal direction, which is peculiar to the neck of the femur in old age; and as that position of the neck is the normal condition in the female, it is supposed to account for the greater frequency of the accident in the female sex. The external cause is usually a fall upon the trochanter, or a fall vertically upon the feet and knees.

Transverse fracture of the patella requires notice, because of the considerable displacement which attends the repair of the injury. The capsule of the knee joint is enlarged upward on the femur to a corresponding degree.

5. Disease Of Texture

Like hyperostosis, these diseases have been sufficiently described in the Chapter on Diseases of the Bones in general.