The deformities of the fingers and toes

by William Anderson

The deformity is bilateral and symmetrical in nearly a third of the cases, in the rest having a slight preference for the right side, in the proportion of five to four. It is usually localised in the first inter-phalangeal articulation, but occasionally implicates both inter-phalangeal joints, or the distal joint only.

Symptoms.—The stages of the deformity in a typical case may be described as follows: In the first period, which is rarely seen by the surgeon, the toe is slightly extended at the metatarso-phalangeal articulation, and flexed at the proximal inter-phalangeal joint. By passive movement the flexed joint may often, but not always, be extended; but the range of motion, even in the early stage, is found to be less than that of the neighbouring or opposite toe. The distal joint is usually unaffected, and may be held straight or slightly flexed, but occasionally it undergoes contraction, either alone or in association with the proximal articulation. There is no evidence at this or any subsequent time of inflammation in or around the joint structures, except in association with corns or bursæ. How long this period may last it is difficult to say, as it may altogether escape the notice of the patient. In the second stage the flexion of the inter-phalangeal joint becomes more pronounced, and the secondary extension at the metatarso-phalangeal joint increases pari passu. At this period the affected articulation is fixed for all movement of extension, but the power of flexion within the limits left to it remains unimpaired; in other words, the angle may be diminished, but not widened, and the toe, although contracted, is neither ankylosed nor paralysed. In exceptional instances the flexion may be overcome by strong passive force, and a distinct trigger-like action established, the middle phalanx becoming extended and flexed again with a movement very comparable to that which takes place during the opening and shutting of the blade of a pocket-knife. As secondary results of the contraction of the proximal inter-phalangeal joint the patient is subject to certain inconveniences which may give rise to much suffering, and are usually the immediate cause of his appeal to the surgeon. The chief of these are a bursal formation, which is very liable to inflammation, over the angle of flexion, and two associated callosities, one above the head of the retracted phalanx, the other beneath the head of the metatarsal bone, both consequent upon the pressure exercised by the boot. (See [Fig. 10.]) A third callosity may develop over the tip of the toe, and the soft parts over the terminal joint may become somewhat swollen, so that the digit presents a clubbed appearance. The degree of interference with functions and comfort varies greatly in different cases, partly in relation to the degree of the contraction and partly to the sensibility of the patient. In some persons a hammer toe of a marked kind will cause so little trouble that no medical advice is sought—this is especially the case when the contraction is limited to the little toe; in others the suffering is so great that the patient begs the surgeon to remove the offending member with the knife, and remains absolutely crippled until an operation is practised for his relief. When the deformity affects more than a single digit, an interval varying from a few months to five or six years may elapse before the second attack appears. As a rule, it is the corresponding toe on the opposite foot that suffers, but occasionally a neighbour is selected; or even the distal joint of the same or another toe.

Fig. 10.

A. Diagram showing position of bones in hammer toe, involving the proximal joint; 1. Metatarsal bone; 2. Head of first phalanx; slight groove corresponding to position of dorsal border of base of second phalanx; 3,4, and 5. Callosities due to boot pressure; 6. Bursa over contracted joint; 7, 8. Shoe. The arrow indicates the direction in which the pressure of the upper leather tends to force downwards the head of the metatarsal bone towards the sole. B. Dissection of first inter-phalangeal joint in hammer toe; C. The same preparation after section of plantar fibres of lateral ligaments.

Morbid anatomy and pathology.—The earlier opinions upon the pathology of hammer toe were very conflicting. Gosselin, who dissected a specimen, was unable to find any lesion. Fano, in 1855, mentions as the chief defect a cartilaginous nucleus in the extensor tendon. Blum described a luxation of the first phalangeal joint, with a thickening of the whole capsule, and maintained that the contraction of the toe was due to a peri-arthritis set up by the inflammation resulting from corns—a curious example of “hysteron proteron.” Blandin attributed the affection to a shortening of the plantar fascia; Boyer to a retraction of the extensor tendons; Roche and Sanson to a contraction of the flexor tendons, and other surgeons to a paralysis of the interossei, but no attempt was made to separate true hammer toe from the arthritic and traumatic deformities which simulate it. It is now beyond doubt that the essential seat of the contraction is in the joint itself. The specimen represented in [B, C, Fig. 10], is one prepared by myself in 1882 from a toe which had been amputated by a colleague. It showed that the deformity was not affected by section of the tendons, but that it yielded immediately upon division of the plantar fibres of the lateral ligaments where they blended with the glenoid plate. This observation, which has been confirmed by a dissection of Mr. Walsham’s, was not published until 1887, and it was by Mr. Shattock, who, working independently, had found the same lesion, that the condition was first made known at the Clinical Society in the same year. The preparation illustrating his paper is now in the museum of St. Thomas’s Hospital, as well as a second dissection demonstrating the absence of disease in the interossei. The results of these and later investigations may now be stated.

(1) There are no essential alterations of muscle or tendon except those secondary to the contraction of the joint—namely, an undue tension and prominence of the extensor tendon over the metatarso-phalangeal articulation, and an adaptive deficiency of length in the flexors, which are prevented by the permanently bent state of the articulation from keeping pace in growth with the osseous structures. (2) The skin and fasciæ in like manner are unaffected or only undergo a secondary shortening on the flexor side in severe and long-standing cases. (3) The articular surfaces generally show no change beyond atrophy of that portion of the cartilage of the head of the proximal bone, which is permanently excluded from contact with the distal bone in consequence of the imperfect range of extension of the joint. In some cases, however, a distinct transverse groove is present on the head of the proximal phalanx at the point where it comes in contact with the dorsal border of the base of the distal bone during the attempt at extension, and behind this groove the bone may be heaped up into a little ridge. It is the existence of this irregularity that explains the trigger phenomenon previously alluded to. (4) The ligaments present no structural change, but an important quantitative defect is always found in the plantar fibres of the lateral ligaments, which are so short that they check prematurely the movement of extension of the joint.

The real origin of the articular defect has been the source of much argument. At all times, whatever may have been the opinion as to the exact morbid anatomy of the condition, there has been a strong disposition to blame the shoemaker, or rather the fashion that dictated the arbitrary form the shoe was to assume, as the prime cause of the disease. There is, of course, no question that the mistaken ideal of elegance which finds expression in the demand for tight and pointed boots has been the cause of much misery and deformity, and it appears only natural to assume that the artificial crowding together of the toes might force one of the members to assume a position of retraction, in order to make room for the rest, and the digit so drawn up might after a time become permanently fixed in its abnormal attitude. This view is well expressed by Mr. Ellis,[10] but the study of a number of cases of hammer toe furnishes strong reason for doubting this fatally plausible hypothesis. The deformity may be seen in early infancy, before any rigid foot covering has been adopted; and a precisely analogous condition is known to exist in the fingers, which are not subjected to any artificial restraints. Moreover, in the great majority of the feet affected with hammer toe there is a complete freedom from the deformities which are known to result from overcrowding of the digits, and there is seldom anything in the history of the cases to indicate the past use of improper boots.

It has been said that hammer toe is unknown in countries where boots are not worn; but the subject has yet to be studied in those parts of the world on a scale that sanctions generalisation. Moreover, as hammer toe is painful only in consequence of the friction and pressure induced by the foot-covering, its existence would be unlikely to attract much attention in a bootless race. During my own residence of six years in Japan I never met with an example, and my friend Surgeon-General Takaki writes to me that his observations, covering a period of fifteen years, are equally negative; but it must be noted that it is the rising and boot-wearing generation that has been especially brought under our notice, and the conclusions to be drawn from our experience tend as much to contradict the view that boots are an immediate cause of hammer toe, as to support the belief that the Japanese are exempt from the defect. There is little doubt, however, that the use of shoes is to some extent, and in a remote sense, a predisponent to this and to other analogous deformities, for it is certain that a rigid leather foot-covering, even when shaped according to the most scientific principles, must necessarily impede the free action of the toes, and so interfere with the processes of nutrition and development; but I am equally confident that few, if any, of the examples of hammer toe that have come within my own experience could be traced to any special defect in the form of the shoe. Out of the whole number only six confessed to having worn tight boots. In the rest, neither history nor inspection indicated any fault of the kind, and the feet in the great majority were perfectly well formed in all other respects, and bore no marks of injurious compression. In a case of inherited hammer toe in which the proximal joint of the second digit of the right foot was straightened by operation, the boots worn before and after the operation were made upon sound anatomical principles; but nevertheless the patient came two years later with a contraction of the distal joint of the same toe and of the middle toe of the opposite foot, and a lateral distortion of the fourth toe.

The pathological explanation I believe to be that advanced to account for the occurrence of hammer finder. The examination of a large number of healthy feet will reveal physiological variations in the condition of the inter-phalangeal joints exactly comparable with those noted in the hands. The second phalanx may in some persons be super-extended 30° beyond the axial line of the proximal bone, while in other instances the movement is arrested by tension of the plantar fibres of the lateral ligaments before this line has been attained;[11] and in the distal joint even greater variation may be found. There is, in fact, a physiological tendency to hammer toe in large numbers of people who never actually suffer any inconvenience from it, and it is in the exaggeration of this physiological irregularity that we have to seek the pathology of the surgical hammer toe. The tendency ceases at adult life, because the ligamentous and bony structures of the articulation have then assumed their permanent condition, and any later deformity simulating it can only occur as a result of a totally different set of conditions.