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.