In the limbs this cause may lead to flexion and almost complete deprivation of mobility, but it is in the hands and fingers that such effects are best seen and studied.
The muscular deformities are much more conspicuous than those due to bony enlargements, and are usually most extreme in cases in which the latter are least marked. In the hands they lead to distor tions similar to those which result from chronic muscular spasm apart from any affection of the joints, as in old cases of infantile paralysis, and in cases in which there has been an antecedent hemiplegia fol lowed by rigidity. In one respect, however, they differ from these, viz., in the almost constant presence of a marked deflexion of the fin gers toward the uluar side.
This ulnar deflexion is only met with after affections of the meta carpo-phalangeal joints, and I believe that the involvement of these joints at some period is a necessary factor in its causation. One sometimes sees this deformity in its most extreme form in patients who have suffered on one or more occasions from rheumatic fever affecting the hands, but in whom the knuckle-joints show no sign of disease other than the relaxation of their ligaments which dates from the antecedent inflammation.
In its earlier stages the production of the deflexion cannot cer tainly be due to the action of the extensor muscles, for the tendons will be found lying in their grooves and sharing in the bend at the knuckles. In extreme cases, on the other hand, the tendons may lie upon the ulnar side of the joints when the knuckles are flexed, but return to their proper positions when the fingers are extended. In health a certain degree of deflexion of the fingers to the ulnar side is readily produced, but any attempt to bring about a similar deflexion to the radial side fails, and it seems probable that in disease the greater amount of ulnar deflexion of which the relaxed ligaments allow is taken advantage of by the force of gravity, aided perhaps by wast ing and consequent weakening of the abductor indicis.
Whether or no this be the correct explanation of the phenomenon, the fact remains that ulnar deflexion of the fingers is not a simple effect of muscular spasm, but implies present or antecedent disease of the metacarpo-phalangeal joints.
The deformities of the hands which are strictly due to muscular spasm have been elaborately classified by Charcot under two main classes, each with several subdivisions. The basis of the classification
is the condition of the middle joints of the fingers, which are some times held flexed, while in other cases they are hyperexteuded. Permanent flexion of any of the finger-joints is apt to be compensated for by hyperextension of others, and in this way a variety of gro tesque deformities are produced.
In Charcot's type of extension the terminal phalanges are flexed upon the second row at an obtuse or even at a right angle. The second phalanges are hyperextended upon the first. The first phalanges are flexed upon the metacarpal bones. Subvarieties of this type are met with.
In the cases belonging to the type of flexion the terminals are ex tended upon the second phalanges, which are in turn flexed upon those of the first row. The first phalanges are extended upon the metacar pals ; and the carpus is flexed upon the forearm. This type also admits of subvarieties. The interossei doubtless play an important part in the causation of these deformities, for they are specially apt to he affected, and if they preponderate over the other muscles they wilf produce flexion of the first phalanges upon the metacarpals, and the type of extension will result, whereas if they are weak there will he hyperextensiou at the same joints and the type of flexion will be produced.
Very rarely dropping of the wrist is met with, as distinguished from active flexion at that joint, and this, when present, is probably due to the affection of the peripheral nerves which has been found post inortem in cases of arthritis deformans by Pitres and Vaillard.
Ctuaoeous PigmentathmDystrophy.—Kent Spender," of Bath, was the first to call attention to the frequent development of pigment spots upon the skin in the neighborhood of joints affected with ar thritis deformans, and even goes so far as to say : " Concerning the disseminated form of pigmentation, commonly called freckles, I must express an opinion that there is no single point so diagnostic, so absolutely connotative of early osteo-arthritis. My observations lead to the belief that it exists in about two-thirds of the undoubted cases." More recently the same point has been independently insisted upon by R. Wichmann," of Brunswick, who was obviously unac quainted with Spender's observations.