The deformities of the fingers and toes

by William Anderson

TRIGGER FINGER.

The description of this curious affection has been left until the last because its true nature is still an unsolved problem, and it is hence difficult to place it in any of the groups already described. It is indeed rather a pathological curiosity than an important item in surgical disease, and many surgeons of long experience have never met with a single example. Of the mechanism of its causation we know almost nothing, of its ultimate tendencies we know little more, and its morbid anatomy is almost entirely speculative. Nevertheless, it has a literature extending over forty years, and comprising nearly a hundred separate contributions, the last of which, a model in its way, is a monograph of 250 closely printed large octavo pages, the work of Dr. Carlier.

Trigger finger, the doigt à ressort of French authors, may be defined as a peculiar defect in the motions of the digit, consisting, first, of an impediment which obstructs the movement of flexion or of extension, or of both, followed, if the motive force be continued, by a sudden cessation of the resistance, and a brusque, spring-like action that often bears a remarkable resemblance to that which accompanies the opening and closure of the blade of a penknife. The first observation was that of Notta in 1850. A finger attacked by this affection generally lies when at rest in a position of flexion, and by a voluntary effort or by passive force may be straightened, with the peculiar result described in the definition, the resistance to extension suddenly yielding with a trigger- or spring-like action; and the same phenomenon is usually but not necessarily repeated when the digit is again bent. In exceptional cases a reverse condition obtains: the passive finger is kept in a state of extension, and it is during flexion that the trigger phenomenon is elicited. The movement may be merely inconvenient, or it may be more or less painful. The sign may be constant, accompanying every movement, or it may be intermittent, disappearing and recurring without any obvious reason. It is usually confined to a single finger, but it may be multiple. The digits most frequently involved are the middle finger, the ring finger, and the thumb, while the index and little fingers are relatively free, and the right side is more often affected than the left. It is rather more common in women than in men (in the proportion of three to two); and much more frequent in adults than in children, but may appear at all ages. The etiology is ill understood. In many cases an important influence, direct or remote, has been assigned to rheumatism; in others the condition has been attributed to injuries of various kinds; in others to occupations necessitating over-use of the digital articulations (as in sempstresses); but no cause has yet been recognised which can account for any large proportion of the examples.

Pathology.—The explanations of the peculiar movement which characterises the disease are for the most part of a purely theoretical character, for, as might be anticipated, the opportunities for direct examination of the structures have been extremely rare. It speaks highly indeed for the ingenuity of our investigators that so many plausible hypotheses have been constructed upon so small a basis of observed fact. The views now open for consideration are as follow: (1) The development of a fringe or other growth in the synovial sheath of the flexor tendons. Such a tumour lying in the synovial cul-de-sac, which projects beyond the proximal end of the tendon sheath when the fingers are flexed, would be drawn within the theca during extension of the digit, and might in this way oppose a resistance to the movement which would be overcome as soon as the body had passed the constricted entrance of the theca. (2) A nodose condition of the tendon due to the development of a growth within the tendon or upon its synovial investment. Such a nodosity is said to have been unmistakably palpable in many cases; but in two examples examined by Carlier, where the tactile impression of a node was remarkably strong, the tendons were found perfectly healthy at the point of examination. On the other hand, Leisering of Hamburg actually exposed a nodosity in the profundus tendon at the level of the point at which it entered the canal of the flexor sublimis, excised it, and cured the disease. In another case a fringe-like tumour was discovered springing from the synovial covering of the flexor sublimis. The nodosity accepted as a fact, the “spring” phenomenon accompanying must be explained by the varying resistance of different parts of the theca, the impediment occurring at either of the firm, resistant portions of the canal which lie at the proximal opening of the sheath and opposite the shafts of the first and second phalanges, and the sudden release occurring at the weaker points, just above the metacarpo-phalangeal joint, and in front of the first inter-phalangeal articulation. In the case of the thumb, however, the fibrous sheath is much thinner than in the fingers, and the variations of strength in its different parts are comparatively slight after the inter-sesamoid portion of the canal is passed. An obstruction offered to a nodule in the flexor profundus by the channel in the flexor sublimis has been proposed as a cause; but although this might be accepted for the fingers, it would not apply to the thumb, which has but one tendon within its theca. (3) An alteration in the shape of the articular surface, such as was first pointed out by König in hammer toe. In these cases the movement of the distal bone is intercepted by the presence of a ridge extending transversely across the head of the proximal bone, and when by voluntary or passive force the ligaments are made to yield sufficiently to allow the obstacle to be surmounted, the movement is terminated by a sudden spring-like action of the extensors or flexors, as the case may be. This condition undoubtedly exists in certain cases of hammer toe and hammer finger; but it must be recollected that these two affections are developmental, and always begin during the period of active growth; while the great majority of examples of trigger finger appear in adult life, after the osseous and ligamentous elements of the articulation have assumed their permanent form. Corresponding changes of form, however, might occur in rheumatoid arthritis. (4) The development on the side of the head of the proximal bone of an osseous excrescence, so placed that the narrow (proximal) attachment of the lateral ligament must pass over it during the movements of flexion and extension. The possibility of this condition, suggested on theoretical grounds by Poirier, cannot be denied; it is, in fact, normal in the tibio-tarsal joint of the ostrich; but its existence in the human subject has yet to be demonstrated. It might well appear in connection with rheumatoid arthritis, but indications of this disease are found in only a small proportion of cases of trigger finger. (5) Spastic irregularities of muscular action. According to this view, advanced by Carlier, the muscle at fault is nearly always the flexor sublimis. It must be recollected that the flexion of the first phalanx is effected mainly by the interossei and lumbricalis, that of the second principally by the flexor sublimis, and that of the third entirely by the flexor profundus; the extension of the first phalanx is due to the common extensor aided by the special accessory extensors in the case of the index and little fingers; the corresponding movement of the second and third phalanges is accomplished by the interossei and lumbricales. In the thumb the metacarpo-phalangeal joint is acted upon by the long and short flexors in the one direction, and by the extensores primi et secundi internodii in the other, while the distal phalanx is flexed by the long flexor and extended principally by the abductor and flexor brevis, which send expansions to the long flexor tendon. If, then, we assume the existence of a reflex spasm of the flexor of a joint the resistance must be overcome by vigorous action of the extensors, or by passive force; and if under these circumstances the spasm yield suddenly the spring phenomenon might be closely simulated. The theory is ingenious, but it involves certain difficulties in its application to trigger finger in general: first, that the “spring” ought to be confined to the movement of extension, unless we assume—and this perhaps is too much to ask—that a similar spasm may affect the extensor also, and be overcome in an analogous way; secondly, that the spring movement should be greatly altered when the tendon of the sublimis is relaxed by flexion of the wrist and metacarpo-phalangeal joint, a modification that has not yet been recorded; thirdly, that it should disappear during complete muscular relaxation under chloroform, and in some cases at least this has not happened.

For the present we must confess our inability to decide the question. In the majority of cases the tendon nodule hypothesis would explain the phenomenon; and the articular theory might be tenable in adolescent cases or where there is rheumatoid arthritis; but more direct evidence is required and closer observation should be directed to the effect of relaxation of groups of muscle by position, and of the muscular system generally by anæsthetics.

The treatment must to some extent share in the uncertainty that attaches to the pathology. The safest and most hopeful measures appear to be a persevering use of passive movement, combined with massage. Surgical operation has been successful in two or three cases, but in others it has missed its mark and has probably left the patient in worse condition than before.

SECTION II
CONTRACTIONS OF THE TOES

The whole of the morbid conditions described in connection with the fingers are probably represented in the toes, and the classification adopted in the former case may be applied with but slight modification to the latter.