In these very acute attacks of inflamma tion, its ravages are seldom confined to the structure which seemed to be the point du depart' of the disease ; the cartilages are in some cases removed from the tibia, fibula, and upper surface of the astragalus with astonishing rapidity; the porous surface of the bones has also been found exposed, and their substance to afford evidence of its having been in a state of inflammation. Surgeons should ever bear in mind, that the synovial membrane of the ankle-joint passes very far forwards on the upper surface of the astragalus, even as far as within a few lines of the junction of this bone with the os naviculare, so that an accidental wound high upon the instep might very readily give rise to a fatal synovitis of the ankle-joint. Moreover, by an experiment on the dead sub ject, it may be shown that a very slight direc tion too much upwards of the edge of the knife when the operation of partial amputation, ac cording to Chopart, is performed, may wound the most anterior part of the synovial sac of the ankle-joint, and the consequences of such a mishap might prove fatal, or at all events greatly aggravate the ills which even without such cause too frequently follow Chopart's operation.
Again, the synovial membrane extends very low down, even to the lowest point of the inner side of the peroneal malleolus, along the outer or fibular surface of the astragalus (fig. 61, a).
It has very frequently happened to the wri ter's knowledge, that inflammation commencing in the body of the os calcis, or in the fibrous or synovial tissue of the articulation between the os calcis and under surface of the astragalus, has crept up to the ankle-joint by this route between the fibula and astragalus; when, therefore, opera tions and cauterizations are performed by surgeons to cure the carious state of the os calcis, the close contiguity of such an important articulation as that of the ankle should be recollected. The great proximity of the ankle-joint to that be tween the under surface of the astragalus and os calcis can only be estimated by making a vertical section of the tibia, fibula, astragalus, and os calcis, passing transversely across these bones and through the malleoli, as may be seen in fig. 61 ; and if a subject be selected in which the epiphysis has not been consolidated with the rest of the bone, a useful view may be had Illustrating many of the preceding practical observations, and explaining clearly how in flammation, traumatic or idiopathic, once esta blished in the ankle-joint, can pass through the epiphysis to the periosteum of the tibia; and ori ginating either in the body of the os calcis, or in some of the structures composing the articulation between this bone and the under surface of the astragalus, can be propagated to the ankle joint : such a viewas this will spew the necessity of con sidering, in connexion, the normal and abnor mal state of these important artieulations.
b. Chronic disease.—The effects of chronic diseases on the tissues composing the ankle joint are next to be considered ; these are vari ous, and may be referred to the influence of specific diseases, such as gout, syphilis, struma, rheumatism, &c.; but the effects of most of these on this particular articulation need not here be discussed, as they will be sufficiently dwelt on elsewhere in this work (see JOINT): we deem it, however, right to enter somewhat into detail in the description of those morbid appearances of the ankle-joint which are supposed to be of a scrophulous origin, and which are denominated white swelling of the ankle-joint. The external characters of the affection are pretty much those in common with the same melancholy disease, in whatever articulation of the extremity it is situated ; the swelling, at first soft, and appear ing in front of each malleolus, seems divided into two by the extensor tendons ; after a time it becomes more solid, and assumes somewhat of a globular form ; here as elsewhere, however, it does not completely surround the joint. The
limb above is wasted and the heel is retracted ; the foot is oedematous, and the toes are pointed downwards, no motion of flexion or extension can be communicated to the foot ; but when the bones are moved laterally, an unnatural motion is communicated to the foot, and a grating of rough and carious surfaces in advanced cases can be felt : the sides of the swelling are studded over with numerous fistulous orifices, from which even now a thin sanious matter can be pressed ; a probe introduced passes either directly through one or other of the malleoli, or by a circuitous route into the interior of the joint through the sinuses, which are, as it were, the excretory ducts leading from the interior, and conducting out the sanious and sabulous matter which proceed from the dege nerated cartilages, synovial membranes, and bones of the diseased joint. The skin is thin, soft, and shining, and moveable on the sur face, except where the fistulous orifices exist.
The anatomical characters of this disease in its advanced stage affecting this articulation we have many opportunities of observing. When the superficial coverings of the swelling are removed, the fat is remarked to be consistent and yellow, the cellular tissue interposed be tween the ligaments, tendons, and muscles is infiltrated with a viscid, semi-fluid, spongy, homogeneous mass ; sometimes this tissue be comes so thick, and is so connected with the lateral ligaments of the ankle-joint, and so in terposed among their softened fibres, as to render a clean dissection of these last impracticable ; so that the ligamentous and cellular structures around the joint appear to have undergone a species of fibro-cartilaginous degeneration ; the viscid glairy matter infiltrated around 'the joint with the tumefied ligaments are the parts which cause the principal swelling, and give to the fingers examining it that deceptive feeling of fluctuation which characterises the white swelling wherever situated.
The few muscular fibres to be found near this joint are pale and of a gelatinous appearance, being infiltrated with the same matter as that which pervades the more superficial structures. The tendons, nevertheless, preserve their natural colour and consistence. The periosteum will be found much thickened and easily detached from the bone.
The bones of the joint, and those in its vici nity, are very usually more or less atrophied, and have undergone a process of degeneration ; notwithstanding, however, what has been said on high authority to the contrary, these bones are occasionally enlarged and expanded ; they have lost much of their specific gravity, their spongy tissue is softened, yellowish, and easily penetrated by a knife, and filled with a matter resembling adipocere, or a yellow semi-fluid fat.
The heel it has been noticed is elongated, and the foot measured from the tibia to the toes on the dorsum is shortened very generally, and pointed downwards. Dissection discovers the cause of this frequent phenomenon in a par tial dislocation of the tibia forwards on the astragalus, the softened ligaments allowing the action of the gastrocnemii and soli to drag the whole foot backwards. In the interior of the articulation, a more or less considerable quantity 'of a sanious matter is found ; while the cartilages covering the end of the tibia and fibula, and surfaces of the astragalus, are softened, adhere but slightly to the bones, and have been partially removed, leaving exposed the porous structure of the latter.
The arteries, veins, and capillaries present no peculiarity, except that the naturally white ligamentous tissue is more freely supplied than usual with red vessels. The neurilema of the posterior tibial nerve is evidently much thick erred, so as to give it an appearance of enlarge ment; the small nerves around the joint seem also hypertrophied.
(R. Adams.)