Skiagraphy
As an aid to the differentiation of gouty from non-gouty forms of arthritis skiagraphy has scarcely fulfilled the somewhat optimistic claims at one time made on its behalf. As to acute gout, radiography reveals nothing abnormal in the bones, though Tousey holds that this of itself at once enables us to exclude osteomyelitis, which, he says, “these cases sometimes resemble.”
Turning now to chronic articular gout, Huber in 1896 drew attention to certain focal areas of rarefaction, or diminished density, in the distal extremities of the phalanges. These localised transparent areas in the bone-ends are discrete, circular, or oval in shape. When located near the edges of the bones, they are of segmental contour, and, viewed in profile, give the appearance of small punched-out holes, simulating syphilitic dactylitis. Despite their proximity to the diseased joints, they apparently do not communicate with the articular cavities.
These bony changes Huber held distinctive of gout, and Koehler, Drinberg, and Jacobsohn and other subsequent writers confirmed Huber’s findings, and, like him, held these areas of rarefaction to be the result of uratic deposits at their sites. Strangeways has dissected bones in which these transparent areas were demonstrated by X-rays. The examination revealed that the bone was definitely excavated, filled with a gelatinous-looking substance, and in advanced cases of gout, moreover, a characteristic deposit of urates clung, as it were, to the margins of the cavities.
Similar focal areas of decreased density were noted by Strangeways in certain cases of rheumatoid arthritis, and both he and Burt found it impossible on the X-ray findings to differentiate between these and gout, i.e., without invoking the aid of clinical data.
Radiographs of the Foot and Hand, showing extensive bony and other changes in long-standing Gout.
Apart from these transparent areas, Wynne many years ago pointed out that small nodes or bony deposits are sometimes met with flanking the sides of the phalanges. More recently Ironside Bruce by radiography has again drawn attention to these bony outgrowths near the extremities of the phalanges (Bruce’s nodes). At first these were thought by Bruce to be composed of urates, but Strangeways from a study of macerated specimens has demonstrated their true bony nature, and also that uratic deposits are not opaque to X-rays, as was formerly thought.
In skiagrams of chronic gout all stages of ankylosis may be seen in the interphalangeal joints. In some it is merely fibrous, in others merging therefrom into bony, and not infrequently true synostosis is observed. Deflections or subluxations are frequent features, due either to the thrust of tophi or small bony outgrowths or to peri-articular contractures.
So much for the skiagraphic findings in chronic gout, and now to discuss their valency as aids to diagnosis of this arthritic disorder. The chief controversy centres around the significance of the focal areas of rarefaction which have been found in the bones of the wrists, hands, ankles, and feet of gouty subjects. Here we may comment on one grave handicap, viz., the lack of certainty as to whether the cases radiographed by different observers were true instances of gouty arthritis.
To justify our expression of doubt we may take, for example, the series reported by Drinberg and Jacobsohn. The said “transparent areas” were present in all the eighteen cases, but the presence of tophi was only established in three. Now, as McClure and McCarty rightly contend, “since the tophus is the only universally accepted pathognomonic sign of gout, for studies of that disease only those patients should be chosen in whom tophi are found, and sodium urate crystals from them microscopically demonstrated.” No one can, I think, gainsay the legitimacy of this stipulation.
In accordance with their contention, McClure and McCarty record their radiographic findings in a series of cases all of which exhibited tophi, and from which sodium urate crystals were isolated. Now, in all these cases the focal areas of diminished density, generally held to be peculiar to gout, were present; but they add that “similar changes were present in two other cases which were clinically gout, but in which no tophi were demonstrated.” Also “in another case without tophi, but which was clinically gout, the focal areas of decreased bony density were not found.”
In addition, they examined the skiagrams of 100 cases of chronic arthritis which “had not been diagnosed clinically as gout.” In thirteen of the examples “the focal areas of decreased density, the so-called gouty bony changes, were found, and were fully as well defined as in the cases of true gout.”
Judging from the skiagraphic appearances, there seemed no reason to suppose that the factors responsible for the production of these rarefied areas were in any way different from those at work in true gout. Now, most authorities have claimed that the bony changes were due to uratic deposits in the bones; but it is at least possible that their origin may be otherwise explained.
Thus Nichols and Richardson have shown that, given focal absorption of lime salts, changes apparently identical with those currently attributed to the presence of tophi may result. These same, though they may not be demonstrable either macroscopically or microscopically, are detectable by X-rays.
Such foci of absorption, viz., areas of decreased density, frequently are located in regions subjected to pressure. Thus they may occur at the inner surfaces of the heads of the first metatarsal bones, or they may form underneath large tophaceous deposits in the soft tissues.
Now, Strangeways has shown that it is impossible by radiography to detect tophi in bones. Accordingly we have at present no means of deciding in any given case whether the localised transparent areas in the bones are due to tophi or to focal absorption of lime salts. If we are to cling to the conception that they are due to tophi, then it is clear that tophi in the bones are more common than is currently suspected, and that, ergo, the frequency of gouty arthritis is underestimated. For these transparent foci in bones, according to McClure and McCarty, occur in from 10 to 12 per cent. of cases of chronic arthritis “which clinically are not gout.”
Yet these authorities hold that, despite the fact that they occur in cases of non-gouty arthritides, they have some diagnostic significance. For, taking the work of other observers in conjunction with their own observations, they come to the following conclusions:—
(1) The focal areas of decreased density, heretofore considered as peculiar to gout, are rarely absent in that disease.
(2) Their absence would be some evidence against the existence of gout in a given case.
(3) On the other hand, their presence is no more than suggestive of gout, since they are found in from 10 to 12 per cent. of cases which clinically are not gout.
(4) The focal areas of decreased density, usually held due to tophi, are probably very often merely focal areas of absorption of lime salts.
In continuation these authorities have endeavoured to identify the nature of the arthritis that occurs in gout. Like other workers in this sphere, the study of the radiographs obtained of gouty joints reveals that a variety of changes occur in the bones and joints of the hands and feet in gouty subjects. These, they consider, may be classified conveniently as follows:—
(1) Cases marked by focal areas of rarefaction, without any other perceptible change;
(2) Cases presenting, in addition to these translucent areas, minor degrees of lipping at the articular margins;
(3) Cases in which the changes in (1) and (2) are conjoined with either localised atrophy of the bones entering into an affected joint, or with generalised atrophy of all the bones in the affected limb;
(4) In addition to all the above changes, narrowing of certain joint spaces with marked proliferative and atrophic changes occurs.
In reviewing these findings of McCarty and McClure, it is important to recollect that they were found in a series of cases all of which exhibited tophi. Moreover, it will be seen that the radiographic changes in some are reminiscent of atrophic or rheumatoid arthritis, in others of hypertrophic arthritis or osteoarthritis, while, lastly, the appearances typical of infective arthritis are also represented. In addition, if we recall that focal areas of rarefaction, indistinguishable from those met with in gout, also occur in all types of non-gouty arthritis, we at once see how impossible it is to detect anything in the radiographic findings distinctive of gouty as opposed to non-gouty arthritides.
McClure and McCarty, comparing the radiographic changes in gouty as opposed to non-gouty arthritis, observe that, though rarefactive foci occur in all varieties of non-gouty arthritis, they are conjoined with other bony or joint changes. On the other hand, translucent areas unassociated with any bone or joint alterations have been found only in gout. But whether this can be claimed as distinctive of gouty arthritis is, they think, uncertain, since relatively few opportunities for X-ray examination of non-gouty arthritis in its early stages have been forthcoming.
Continuing, of their four radiographic types of gouty arthritis the second resembles osteoarthritis; but the third and especially the fourth group, they consider, “fall into a peculiar class,” this inasmuch as their characters resemble the infective type of non-gouty arthritis. They claim, however, that a differentiation, radiographically speaking, can be effected, this because of the “sharply localised” extreme degree of bony atrophy which occurs in the infective type of non-gouty arthritis. However, as they admit that radiographs of the latter (infective non-gouty arthritis) have been noted which “closely resemble” the “atrophic and proliferative changes occurring in gout,” their final conclusion is that in the skiagrams even of typical gouty arthritis there is nothing in the bony or arthritic changes that is diagnostic of gout.
For myself, I must admit that I have come to the same conclusion as McClure and McCarty, viz., that the skiagraphic findings in gouty and non-gouty arthritis trench so much the one upon the characters of the other that I should be loth indeed to base a diagnosis of gout simply on the revelations of skiagraphy. The chief interest to my mind, as I have previously observed, centres round those examples in which peri-articular tophi are associated with underlying bony and arthritic changes (as revealed by X-rays) indistinguishable from those typical of infective arthritis of non-gouty type.
We have seen also that local foci of rarefaction may be met with in infective arthritis of non-gouty type. Moreover, the proliferative and marked atrophic bony changes found in some instances of gouty arthritis are quite compatible with their infective origin. Witness how impossible it is to differentiate skiagraphically between atrophic arthritis and gouty arthritis, and at the same time let it not be forgotten, on the other hand, that the dividing line between the infective arthritides and the more acute forms of atrophic or rheumatoid arthritis is by no means sharply defined. Review this also in light of the fact of the close resemblance that obtains between acute articular gout, especially the polyarthritic variety, and types of arthritis of avowedly infective origin, and we see at once how close is the clinical similitude. We turn to radiography, and here again we are met with the same family resemblance, suggestive of a probable community of origin. How clear then the inference that it is on tophi, and tophi alone, that we must base an absolute diagnosis of gouty arthritis. Moreover, since tophi are not detectable by skiagraphy, our mainstay must be physical examination directed to their detection. As for those cases of so-called “clinical gout,” viz., unattested by tophi, it is probable that their absolute identification, as such, will never be attainable on purely clinical, but on bacteriological, data, which, it is to be hoped, will before long be forthcoming.