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The anterior tarsus and forefoot
3 The anterior tarsus and forefoot ALLAN
S T . J. D I X O N
This chapter is concerned with arthritis of the anterior tarsal and toe joints and its consequences. Rheumatoid arthritis is the most frequent form of arthritis and is taken as the type disease. Other forms of joint disease (diabetic, seronegative and neuropathic arthropathies) often show much in common with rheumatoid arthritis in their effects on the feet and will be considered briefly in the differential diagnosis and in the appropriate chapters elsewhere in this book. HISTORICAL AND E P I D E M I O L O G I C A L In modern times and amongst Western E u r o p e a n populations, classical seropositive rheumatoid arthritis almost always involves the feet and the feet are often the first joints to be affected. There is some evidence that this was not always so, nor is it currently true of other ethnic groups. In the United Kingdom rheumatoid arthritis is now the largest single identifiable cause of foot deformities requiring provision of National Health Service shoes (23% in Bainbridge's 1975-6 survey) at an annual cost of many millions of pounds. Nevertheless, the community response to the burden of foot ill health in general, and of foot problems caused by arthritis in particular, still leaves much to be desired. The number of chiropodists is inadequate because although well trained their conditions of pay and service are not sufficiently rewarding. Professional specialist medical response is small as judged by comparison of the numbers of scientific papers published on the hand compared with those published on the foot (Dixon, 1981). A recent survey of joint disorders in the elderly made no mention of disorders of the foot joints (Bergstr6m et al, 1986), possibly the most prevalent cause of crippling joint disease in the elderly and one which is rising in frequency. Yet in a population survey, only 25 % of men aged 75 or more and 16% of women aged 75 or more were not seeking treatment for their feet and about a half these complained of severe pain (Brodie, 1984). Many of these complaints concerned arthritis of the feet of one sort or another. BACKGROUND
The mean age of onset of rheumatoid arthritis has been rising over the last Bailli~re's Clinical Rheumatology--Vol. 1, No. 2, August 1987
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five decades and is now about 50, with women affected about three times as often as men. As women survive to a greater age than men, the sex ratio in the elderly is around 5 or 6 w o m e n : 1 man. Moreover, at all ages women have more foot problems than do men. Surveys of the population (e.g. Clarke, 1969; Dunnell and Cartwright, 1972) found that evidence of troubles with feet increased with age and as one would expect, were more frequent in older women. It is important to accept that rheumatoid arthritis does not take root in virgin soil--it is associated with, modifies and is modified by pre-existing shoe deformities in most instances. Hollman (1960) has followed the development of children's feet and the changes in the foot. in response to shoe and sock pressures. By the age of fifteen most children have fifth toes which are incurved and 15% of girls have significant established hallux valgus attributable to shoe pressures. It is about this age that the foot 'sets' and deformities become irreversible but remain progressive. Once the powerful flexor tendons of the hallux are displaced towards the mid-line of the foot, carrying with them the two sesamoid bones, every contraction of the tendon will have a vector which increases the deformity. In contrast bare foot populations remain free of significant hallux valgus until they take to shoe wearing (Shine, 1965). With age, hallux valgus leads to secondary degenerative arthritis of the first metatarsophalangeal (MTP) joint and frequently to dorsal dislocation of the second MTP joint as the big toe continually presses it in walking, a combination of toe changes superficially similar to that seen in rheumatoid arthritis. When both conditions co-exist it is impossible to assign a fractional cause to rheumatoid arthritis or to the previous deformity. A n o t h e r major determinant of outcome of rheumatoid arthritis in t h e f e e t is the natural flexibility of the foot structure. A short period of experience in a foot clinic soon shows that some people have a very loose, soft, deformable foot structure, whilst in others the foot structure is rigid. When rheumatoid is grafted on top of these extremes the result will be different. Either the foot will tend to collapse at the normal arches or there will be a rapid localized build-up of pressures on skin covering unyielding bony prominences. Attempts to count the population frequency of rheumatoid arthritis of the foot suggests that 2% of adults in the U K are so affected (Dixon, 1981) but the combination of age-related change and increasingly late onset of rheumatoid arthritis suggests that in the elderly the frequency of foot troubles due to arthritis must be considerably higher. There is some hope for the future as other surveys seem to show that rheumatoid arthritis is getting less frequent and less severe (Silman, 1986). Perhaps we are currently seeing the peak of suffering caused by rheumatoid arthritis of the feet.
EARLY R H E U M A T O I D ARTHRITIS
The feet are involved in many systemic diseases. Persistent pain in the feet whether or not this proves to be due to rheumatoid arthritis, requires a full history, clinical and X-ray examinations and laboratory screening tests.
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Other conditions seen in a foot clinic have included: 9 Other forms of arthritis 9 Endocrine conditions
9 Ischaemic conditions
Gout, pseudo gout, Reiter's syndrome septic arthritis, psoriatic arthropathy. Diabetes with peripheral neuropathy and/or ischaemia. Hypothyroidism with myxoedema affecting the feet. Cushing's syndrome with osteoporosis causing stress fractures of the metatarsals. Arteriosclerosis, Raynaud's disease, systemic sclerosis.
9 Peripheral neuropathies other than diabetic 9 Malignancies affecting the feet There have also been localized conditions which may be mistaken for arthritis, e.g. Morton's metatarsalgia, march fracture, hallux valgus, hallux rigidus, calcaneal spurs, Sudeck's atrophy, to name but a few. Modes of onset of rheumatoid arthritis in the feet
Rheumatoid arthritis commonly starts in the joints of the feet, especially the metatarsophalangeal joints. This is detected by palpating the individual metatarsal heads or by the transverse metatarsal compression test (Katz, 1977). In the latter test, the fingers and thumb gently squeeze the metatarsal heads together, something which is painless in normal feet but tenderness is elicited in early rheumatoid arthritis. This test is sufficiently sensitive to serve as a good screening test for rheumatoid arthritis. Less commonly, rheumatoid arthritis may start with isolated involvement of tendon sheaths at the ankle. Mr KD, 69, a retired driver was referred with a swollen ankle. Examination showed a fluctuant swelling in the anatomical site of the posterior tibialis tendon sheath. Cloudy fluid, sterile on culture, was aspirated. Swelling was controlled for two years by small injections of a long-acting local corticosteroid. However, evidence of generalized rheumatoid arthritis affecting fingers and knees subsequently appeared and the rheumatoid factor tests became positive. Most rarely still early rheumatoid arthritis may present as a general oedema of the feet only later appearing to localize in joints. Mis-diagnoses in this early stage are common. Some patients are referred to chiropodists with 'metatarsalgia' or 'dropped arch'. Others give a history of recent operation for painful 'bunion', an often painless condition, suggesting that rheumatoid arthritis rather than the deformity was the immediate cause of the complaint of pain. Because of the foot swelling, patients complain that their shoes are too tight and they have cupboards full
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Figure 1. Early rheumatoid arthritis--swelling of metatarsophalangeal joints causes toes to separate.
of shoes bought in hope but no longer wearable. This swelling of the foot across the metatarsal heads may have the effect of separating the toes from each other. Instead of the toes being packed close together in the resting state it becomes possible to 'see daylight' between them and this is increased on standing (Figure 1).
Differential diagnosis of early rheumatoid arthritis The following indicate causes of arthritis other than early rheumatoid: 9 Heel pain ~in seronegati~e spondylarthropathies 9 Painful plantar spurs J 9 Generalized swelling of toes with coppery pigmentation in Reiter's syndrome 9 Predominant cellulitic inflammation around the big toe (gout and pseudo gout) 9 Skin over the painful area hot and dry, as in gout or sepsis and as opposed to the moist sweating skin of rheumatoid arthritis and the spondylarthropathies
X-ray and laboratory tests Tests for IgM RA factor are often positive in early rheumatoid arthritis of the feet but not in other forms of arthritis while about 80% of Reiter's syndrome will be positive for the white cell blood group HLA B27. The serum uric acid will always be raised in true gout (in the absence of treatment) but may be misleadingly raised in patients taking diuretics for foot swelling. X-rays of the feet are seldom helpful in early rheumatoid arthritis except to rule out other painful conditions such as march fracture. Thermograms may, however, show disordered patterns of heat regulation especially on rewarming after cooling.
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LATE RHEUMATOID ARTHRITIS
The metatarsal area of the foot suffers badly in late rheumatoid arthritis. Inflammatory joint disease leads to weakening of joint capsules and their associated ligaments. Resistance to the deforming effects of sock and shoe pressures diminishes as does resistance to the altered lines of flexor tendon pull in hallux valgus and quintus varus. In the lateral metatarsal area, the proximal phalanges sublux upwards and eventually dislocate. They carry with them the phalanges which become clawed and cease to take pressure on walking. Meanwhile the important fibro-fatty cushions which relieve ground pressures in normal feet are displaced (Dixon, 1981). Those under the metatarsal heads move forward and upwards and (if the toes are clawed) the toe tip cushions cease to take weight. Callosities form under the metatarsal heads and under the toe nails if the toe tips take pressure in walking (Figure 2). Pedographs at this stage confirm the re-distribution of pressures. Total impact pressures are reduced because the patient walks gingerly and the period of both hind and forefoot contact is increased. However under prominent and unprotected metatarsal heads there are pressure concentrations which may be twenty times normal in dynes per square mm.
Figure 2. Deep cleft in skin betweenprolapsed metatarsalheads.
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Figure 3a. Retraction of toes m e a n s that they cease to take weight in the kick-off phase of walking. Note also the 'centre-forward' callosity under the second metatarsal head.
Figure 3b. Callosity under the second metatarsal head has broken down and a sinus has formed.
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Because of the toe deformity, pressure lesions develop on the dorsum of the toes from rubbing on shoes and may ulcerate. On the plantar aspect of the foot the prolapse of the metatarsal heads leads to two sets of lesion. One is the formation of clefts in the skin between the metatarsal heads which may become involved by fungus infections (Figure 2). More serious is a sequence of changes which takes place under the metatarsal heads. The increased pressure in the skin and subcutaneous tissue under a metatarsal head leads first to callosity formation. Characteristically, one of the first to form is under the second metatarsal head, the so-called 'centreforward' callosity (Figure 3a). Callosities under the third and fourth lateral metatarsal heads may follow. If the patient continues to walk despite pain, bruising occurs and may eventually break down to form a sinus which is fistulous down to and sometimes into the metatarsal joint (Figure 3b). Secondary infection is common. Medical treatment (rest, antibiotics) is seldom more than temporarily successful. Surgery after a suitable cleaning up of the operative field will be needed. Sometimes (Figure 4) nature attempts to correct the increased pressures on the metatarsal heads. Instead
Figure 4. Miss I.H. Rheumatoid arthritis since childhood. Development of fluid filled adventitious bursae under the metatarsal heads.
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of atrophy and ulceration, adventitious bursae appear becoming distended with fluid, sometimes strikingly so. A hydraulic cushion has thus been substituted for the natural cellular fibro fatty-sponge cushions and should not be aspirated or removed. The great toe
Hallux valgus is the characteristic deformity of the great toe occurring as frequently as other changes in the forefoot (Vidigal et al, 1975). It is an exaggeration of the hallux valgus so commonly seen in many women, and some men. It is accompanied by increased metatarsus primus varus caused by the progressive bow-stringing effect of the flexors. Similar changes of quintus varus and metatarsus quintus valgus cause a total widening of the transverse diameter of the metatarsal region, increasing shoe pressures over the bunion and bunionette areas. At first the hallux valgus closes the natural gap between the first and second toes. Later the second toe has to move to accommodate the big toe. It does so usually by overriding it, although occasionally this displaced big toe lies on top of the others. Later still the hallux subluxes downwards at the MTP joint (Figure 5) and often this is accompanied by rotation (hallux valgus et tortus) so that the pad of the big toe points laterally. As with the metatarsal heads, skin pressure lesions lead to subcutaneous atrophy, ulceration and occasional fistula formation or more rarely to the formation of protective adventitious bursae. It scarcely needs elegant imaging methods to discern the altered patterns of pedal pressures--they are written on the patient's feet with a corresponding moulding of the interior of the shoe. Nevertheless a thermogram (Figure 6) picking up the areas of reactive hyperaemia after walking, can be very revealing.
Figure 5. Plantar subluxationof the hallux.
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Figure 6. Black and white direct and computer contoured thermograms of reactive hyperaemia in rheumatoid feet. Note the abnormally high temperatures under the left midtarsal area, both metatarsophalangeal areas and the cold spot under the left heel caused by redistribution of foot pressures.
The net effect of these changes is that the toes cease to become operative and often make no imprint at all on walking on a foot-print mat. In some patients, either spontaneously or as a result of surgery, the 1st metatarsal joint becomes stiffened and then the whole force on the first ray at the kick-off phase of walking falls on the 1st interphalangeal joint. Abnormal dorsiflexion of this joint later leads to an atrophy of the cushion tissue of the pad of the big toe and is followed by a pressure callosity. The fifth toe
The packing together of the toes causes, first, quintus varus, then an overor under-riding of the fifth toe with respect to the fourth. If the toe is very protuberant, successful shoe fitting is impossible and amputation may be needed.
COMPLICATIONS A F F E C T I N G THE FEET The most common is oedema, making shoe fitting difficult. There are a number of causes--these include high protein inflammatory oedema associated with the active synovitis and low-protein o e d e m a from dependency or compression of venous and possibly lymphatic return by synovial cysts at knee or hip. Fluid retaining non-steroidal anti-inflammatory drugs may increase oedema and there may be on occasions a contribution from acute synovial rupture at the knee or ankle releasing inflammatory joint fluid into the tissues. The tendency to oedema is increased by the sedentary life forced on the unfortunate sufferer. Additionally, abnormalities of capillary permeability, identified by Jayson and Barks (1971) occur. Foot o e d e m a in rheumatoid arthritis responds to diuretics to some extent and up to a kilogram of fluid can be removed from legs (Kalos et al, 1974).
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Figure 7.
Rheumatoid arthritis and vasculitis--nail edge lesions in toes.
Rheumatoid vasculitis is not uncommon presenting usually as small vessel occlusion with patchy necrosis over pressure areas. Nail edge lesions, common in the fingers in rheumatoid arthritis, are only occasionally seen in the toes (Figure 7). Rarely, major vessel blockage occurs, with widespread ulceration and gangrene. Rheumatoid vasculitis affecting the feet was at one time commonly associated with a mixed sensory-motor peripheral neuropathy--adding to the patient's miseries. But in the last ten years this has become rare. Corticosteroid can cause dermal collagen atrophy in the feet as elsewhere with thin transparent and easily bruising skin and dilated unsupported capillaries.
Midtarsal joint Although less common than talo-calcaneal or MTP joint involvement, the midtarsal joint can be a source of great discomfort, responding only to surgery. All rotational movements of the forefoot become painful and no shoe or orthosis or local steroid injection gives more than partial and temporary relief, once necrosis of the talonavicular joint has occurred (Figure 8).
OTHER FORMS OF ARTHRITISIN THE FEET Deformities, resembling those of rheumatoid arthritis are occasionally seen in chronic Reiter's syndrome whether sexually acquired or post-dysenteric, although less often eroding bone. In the earlier stages, inflammatory oedema around tendon sheaths in the foot may cause considerable periosteal reaction
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Figure 8. X-ray of mid-tarsal joint-destruction of talo-navicular articulation.
around the metatarsal shafts seen on X-ray, but this is non-specific and is seen sometimes in m o r e severe and active rheumatoid arthritis of the feet. There are four commonly observed heel lesions in arthritis. Large rheumatoid nodules, under the heel or on the achilles tendon are confined to rheumatoid arthritis (Figure 9a and b) are confined to rheumatoid arthritis. Erosive bursitis of the achilles tendon bursa can be seen in all these conditions. A diffuse Achilles insertional tendinitis is, however, confined to seronegative spondylarthropathies and is H L A B27 related. Tenderness under the heel, in the calcaneal spur area, is either idiopathic or related to seronegative arthritis although the underlying bony change namely the development of a forward pointing bony spur seen on X-ray is often to be noted in late rheumatoid arthritis as it is in those who have never had arthritis.
Scleroderma and Raynaud's disease Raynaud's disease causes spasm or occlusion of the digital vessels and to a lesser degree can lead to poor nutrition of the tissues with shrinkage of the soft tissues. Some degree of contracture of the joint may occur but the biggest changes are associated with progressive systemic sclerosis (scleroderma). The whole foot may develop a shrunken rigid structure with a tendency to ulcerate and with little effective cushioning over bony prominences even if the joints are not contracted. The requirement is for a fully cushioned and well insulated shoe. Similar changes may occur in Werner's syndrome.
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(a)
(b) Figure 9. Rheumatoid nodules under thc heel (9a) and on the achilles tendon (9b).
The tangential foot X-ray In the assessment of metatarsophalangeal joint changes the tangential foot X-ray can be very helpful. In this, the beam of X-rays is directed to the metatarsal area of the sole of the foot as tangentially as possible, the radiographer arranging his plate so that the toes are dorsiflexed. Tangential X-rays show the position of the anterior metatarsal arch, the position and structure of the sesamoids and the degree of inferior erosion and spike formation on the metatarsal heads in relation to the covering skin and subcutaneous tissue (Gheith and Dixon, 1973).
TREATMENT There is no single treatment for 'the' rheumatoid foot but much can be done
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to help, but only after correct analYsis of the causes of pain, and depending on the availability of various medical, orthotic and surgical treatments. There is a demonstrated need for multidisciplinary foot clinics, and not just concentrating on arthritis, for once such a clinic is opened an enormous variety of foot problems will be referred, varying from congenital and acquired deformities to patients with central and peripheral neuropathies as well as arthritis. A physician and an orthopaedic surgeon, a chiropodist and an orthotist should be available. Such clinics are expensive to run and must be carefully organized. They should be secondary referral clinics, i.e. patients referred to them must have had a full medical or surgical examination elsewhere and be provided with up-to-date X-rays of the feet. Preferably, these should be taken with the feet in weight bearing position. This is particularly important for mid-tarsal and hindfoot problems. The tangential X-ray can also be ordered with benefit. General medical conditions, or problems with joints elsewhere which might interfere with surgery of the foot, must be detected. Then a combined decision is made as to the correct line of treatment. Often this will be conservative. The development of lightweight shoes using modern microcellular rubber soles and heels and foam insoles which can cushion the foot has been perhaps the greatest advance. Women with relatively early arthritis of the feet can often manage with sandals in the summer and fur-lined boots in winter. For moderately severe problems, modular 'depth' shoes are available in several widths, lasted more deeply than normal to accommodate a foam or custom-made insock. (Insocks to be worn inside a patient's own shoes are often and uselessly prescribed--they merely take up more room inside a shoe already too tight because of foot swelling.) More severe deformities need individually fitted shoes either made by traditional bespoke shoe making techniques or, more cheaply, to plaster of Paris models of the patient's foot. Some of the worst deformities will require shoe making skills not often available (Munzenberg, 1985) and see Chapter 10). Active arthritis in foot joints can often be treated by local injection therapy, using a long-acting corticosteroid local anaesthetic mix (Dixon and Graber, 1981). Chiropodists can help with pressure- and chafing-relieving pads and protectors. Rheumatoid arthritis surgery has been remarkably successful for severe deformities of the feet particularly where one or more metatarsal heads are prominent in a rigid foot. Forefoot arthroplasties are time-consuming and require quite prolonged hospitalization, but balancing osteotomies are simple and in suitable patients can give signal relief. A similar experience in connection with diabetic foot problems has shown that a multi-disciplinary approach can cut down morbidity and amputation rates with positive costbenefit implications (Edmonds et al, 1986). PREVENTION A N D SOCIAL POLICY
There is no evidence yet that rheumatoid arthritis can be prevented but there is evidence that the morbidity associated with rheumatoid arthritis
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foot i n v o l v e m e n t could be r e d u c e d . I n M i d d l e E a s t e r n c o u n t r i e s , seropositive r h e u m a t o i d arthritis is not u n c o m m o n and X-rays a n d clinical e x a m i n a t i o n s reveal foot i n v o l v e m e n t . B u t the degree of crippling is far less, almost certainly b e c a u s e w o m e n have b e e n less exposed to the c o m p u l s i v e s a l e s m a n s h i p of female foot fashion, high heels which force b o d y weight o n t o the toes, court styles which can only be kept on by c o m p r e s s i n g the toes, to say n o t h i n g of bizarre ' w i n k l e picker' p o i n t e d toe styles. Social policy changes a n d public e d u c a t i o n are n e e d e d to rid w o m e n of such f o o t w e a r just as they have b e e n liberated f r o m the E d w a r d i a n constrictions of tight lacing.
REFERENCES
Bainbridge S (1975-76) National Health surgicalfootware. Office of population censuses and surveys. London: HMSO. Bergstr6m G, Bjelle A, Sundh V & Svanborg A (1986) Joint disorders at ages 70, 75 and 79 years---a cross-sectional comparison. British Journal of" Rheumatology 25: 333-341. Brodie BS (ed.) (1984) Wessex Feet--A Regional Foot Health Survey, vol. 1. Published by Dept of Chiropody Southampton and South West Hampshire Health District, Southampton General Hospital, Southampton. Clarke M (1969) Trouble with Feet. London: Bell. Dixon AS (1981) The physician's foot. Journal of the Royal Society of Medicine 74: 101-110. Dixon AS & Graber J (1981) Local Injection Therapy. Basel: EULAR Publishers. Dunnell K & Cartwright A (1972) Medicine Takers, Prescribers and Hoarders. London and Boston: Routledge and Kegan Paul. Edmonds ME, Blundell MP, Morris ME et al (1986) Improved survival of the diabetic foot: the role of a specialist foot clinic. Quarterly Journal of Medicine 60: 763-772. Gheith SL & Dixon AS (1973) Tangential X-ray of the forefoot in rheumatoid arthritis. Annals" of Rheumatic Diseases 32" 92-93. Hollman C (1960) Shoes for children--A survey of retail shoe shops in the borough of Ealing. British Medical Journal 1: 719. Jayson MIV & Barks JS (1971) Oedema in rheumatoid arthritis: changes in the coefficient of capillary filtration. British Medical Journal 2" 555-557. Kalos A, Dixon AS & Weber JCP (1974) Xipamid in the treatment of oedema in rheumatoid arthritis. Rheumatology and Rehabilitation 13: 81-87. Katz WA (1977) Rheumatic Diseases, pp 182, 183. Philadelphia: JB Lippincott. Munzenberg KJ (1985) The Orthopedic Shoe.Weinheim: VCH Verlagsgesellschaft. Shine IB (1965) Incidence of hallux valgus in a partially shoe-wearing community. British Medical Journal i: 1648-1649. Silman A (1986) Recent trends in rheumatoid arthritis (editorial). British Journal of Rheumatology 25: 328-329. Vidigal E, Jacoby RJ, Dixon AS, Ratliff AH & Kirkup J (1975) The foot in chronic rheumatoid arthritis. Annals of Rheumatic Diseases 34: 292-297.
S T . J. D I X O N
This chapter is concerned with arthritis of the anterior tarsal and toe joints and its consequences. Rheumatoid arthritis is the most frequent form of arthritis and is taken as the type disease. Other forms of joint disease (diabetic, seronegative and neuropathic arthropathies) often show much in common with rheumatoid arthritis in their effects on the feet and will be considered briefly in the differential diagnosis and in the appropriate chapters elsewhere in this book. HISTORICAL AND E P I D E M I O L O G I C A L In modern times and amongst Western E u r o p e a n populations, classical seropositive rheumatoid arthritis almost always involves the feet and the feet are often the first joints to be affected. There is some evidence that this was not always so, nor is it currently true of other ethnic groups. In the United Kingdom rheumatoid arthritis is now the largest single identifiable cause of foot deformities requiring provision of National Health Service shoes (23% in Bainbridge's 1975-6 survey) at an annual cost of many millions of pounds. Nevertheless, the community response to the burden of foot ill health in general, and of foot problems caused by arthritis in particular, still leaves much to be desired. The number of chiropodists is inadequate because although well trained their conditions of pay and service are not sufficiently rewarding. Professional specialist medical response is small as judged by comparison of the numbers of scientific papers published on the hand compared with those published on the foot (Dixon, 1981). A recent survey of joint disorders in the elderly made no mention of disorders of the foot joints (Bergstr6m et al, 1986), possibly the most prevalent cause of crippling joint disease in the elderly and one which is rising in frequency. Yet in a population survey, only 25 % of men aged 75 or more and 16% of women aged 75 or more were not seeking treatment for their feet and about a half these complained of severe pain (Brodie, 1984). Many of these complaints concerned arthritis of the feet of one sort or another. BACKGROUND
The mean age of onset of rheumatoid arthritis has been rising over the last Bailli~re's Clinical Rheumatology--Vol. 1, No. 2, August 1987
261
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five decades and is now about 50, with women affected about three times as often as men. As women survive to a greater age than men, the sex ratio in the elderly is around 5 or 6 w o m e n : 1 man. Moreover, at all ages women have more foot problems than do men. Surveys of the population (e.g. Clarke, 1969; Dunnell and Cartwright, 1972) found that evidence of troubles with feet increased with age and as one would expect, were more frequent in older women. It is important to accept that rheumatoid arthritis does not take root in virgin soil--it is associated with, modifies and is modified by pre-existing shoe deformities in most instances. Hollman (1960) has followed the development of children's feet and the changes in the foot. in response to shoe and sock pressures. By the age of fifteen most children have fifth toes which are incurved and 15% of girls have significant established hallux valgus attributable to shoe pressures. It is about this age that the foot 'sets' and deformities become irreversible but remain progressive. Once the powerful flexor tendons of the hallux are displaced towards the mid-line of the foot, carrying with them the two sesamoid bones, every contraction of the tendon will have a vector which increases the deformity. In contrast bare foot populations remain free of significant hallux valgus until they take to shoe wearing (Shine, 1965). With age, hallux valgus leads to secondary degenerative arthritis of the first metatarsophalangeal (MTP) joint and frequently to dorsal dislocation of the second MTP joint as the big toe continually presses it in walking, a combination of toe changes superficially similar to that seen in rheumatoid arthritis. When both conditions co-exist it is impossible to assign a fractional cause to rheumatoid arthritis or to the previous deformity. A n o t h e r major determinant of outcome of rheumatoid arthritis in t h e f e e t is the natural flexibility of the foot structure. A short period of experience in a foot clinic soon shows that some people have a very loose, soft, deformable foot structure, whilst in others the foot structure is rigid. When rheumatoid is grafted on top of these extremes the result will be different. Either the foot will tend to collapse at the normal arches or there will be a rapid localized build-up of pressures on skin covering unyielding bony prominences. Attempts to count the population frequency of rheumatoid arthritis of the foot suggests that 2% of adults in the U K are so affected (Dixon, 1981) but the combination of age-related change and increasingly late onset of rheumatoid arthritis suggests that in the elderly the frequency of foot troubles due to arthritis must be considerably higher. There is some hope for the future as other surveys seem to show that rheumatoid arthritis is getting less frequent and less severe (Silman, 1986). Perhaps we are currently seeing the peak of suffering caused by rheumatoid arthritis of the feet.
EARLY R H E U M A T O I D ARTHRITIS
The feet are involved in many systemic diseases. Persistent pain in the feet whether or not this proves to be due to rheumatoid arthritis, requires a full history, clinical and X-ray examinations and laboratory screening tests.
THE ANTERIOR TARSUS AND FOREFOOT
263
Other conditions seen in a foot clinic have included: 9 Other forms of arthritis 9 Endocrine conditions
9 Ischaemic conditions
Gout, pseudo gout, Reiter's syndrome septic arthritis, psoriatic arthropathy. Diabetes with peripheral neuropathy and/or ischaemia. Hypothyroidism with myxoedema affecting the feet. Cushing's syndrome with osteoporosis causing stress fractures of the metatarsals. Arteriosclerosis, Raynaud's disease, systemic sclerosis.
9 Peripheral neuropathies other than diabetic 9 Malignancies affecting the feet There have also been localized conditions which may be mistaken for arthritis, e.g. Morton's metatarsalgia, march fracture, hallux valgus, hallux rigidus, calcaneal spurs, Sudeck's atrophy, to name but a few. Modes of onset of rheumatoid arthritis in the feet
Rheumatoid arthritis commonly starts in the joints of the feet, especially the metatarsophalangeal joints. This is detected by palpating the individual metatarsal heads or by the transverse metatarsal compression test (Katz, 1977). In the latter test, the fingers and thumb gently squeeze the metatarsal heads together, something which is painless in normal feet but tenderness is elicited in early rheumatoid arthritis. This test is sufficiently sensitive to serve as a good screening test for rheumatoid arthritis. Less commonly, rheumatoid arthritis may start with isolated involvement of tendon sheaths at the ankle. Mr KD, 69, a retired driver was referred with a swollen ankle. Examination showed a fluctuant swelling in the anatomical site of the posterior tibialis tendon sheath. Cloudy fluid, sterile on culture, was aspirated. Swelling was controlled for two years by small injections of a long-acting local corticosteroid. However, evidence of generalized rheumatoid arthritis affecting fingers and knees subsequently appeared and the rheumatoid factor tests became positive. Most rarely still early rheumatoid arthritis may present as a general oedema of the feet only later appearing to localize in joints. Mis-diagnoses in this early stage are common. Some patients are referred to chiropodists with 'metatarsalgia' or 'dropped arch'. Others give a history of recent operation for painful 'bunion', an often painless condition, suggesting that rheumatoid arthritis rather than the deformity was the immediate cause of the complaint of pain. Because of the foot swelling, patients complain that their shoes are too tight and they have cupboards full
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Figure 1. Early rheumatoid arthritis--swelling of metatarsophalangeal joints causes toes to separate.
of shoes bought in hope but no longer wearable. This swelling of the foot across the metatarsal heads may have the effect of separating the toes from each other. Instead of the toes being packed close together in the resting state it becomes possible to 'see daylight' between them and this is increased on standing (Figure 1).
Differential diagnosis of early rheumatoid arthritis The following indicate causes of arthritis other than early rheumatoid: 9 Heel pain ~in seronegati~e spondylarthropathies 9 Painful plantar spurs J 9 Generalized swelling of toes with coppery pigmentation in Reiter's syndrome 9 Predominant cellulitic inflammation around the big toe (gout and pseudo gout) 9 Skin over the painful area hot and dry, as in gout or sepsis and as opposed to the moist sweating skin of rheumatoid arthritis and the spondylarthropathies
X-ray and laboratory tests Tests for IgM RA factor are often positive in early rheumatoid arthritis of the feet but not in other forms of arthritis while about 80% of Reiter's syndrome will be positive for the white cell blood group HLA B27. The serum uric acid will always be raised in true gout (in the absence of treatment) but may be misleadingly raised in patients taking diuretics for foot swelling. X-rays of the feet are seldom helpful in early rheumatoid arthritis except to rule out other painful conditions such as march fracture. Thermograms may, however, show disordered patterns of heat regulation especially on rewarming after cooling.
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LATE RHEUMATOID ARTHRITIS
The metatarsal area of the foot suffers badly in late rheumatoid arthritis. Inflammatory joint disease leads to weakening of joint capsules and their associated ligaments. Resistance to the deforming effects of sock and shoe pressures diminishes as does resistance to the altered lines of flexor tendon pull in hallux valgus and quintus varus. In the lateral metatarsal area, the proximal phalanges sublux upwards and eventually dislocate. They carry with them the phalanges which become clawed and cease to take pressure on walking. Meanwhile the important fibro-fatty cushions which relieve ground pressures in normal feet are displaced (Dixon, 1981). Those under the metatarsal heads move forward and upwards and (if the toes are clawed) the toe tip cushions cease to take weight. Callosities form under the metatarsal heads and under the toe nails if the toe tips take pressure in walking (Figure 2). Pedographs at this stage confirm the re-distribution of pressures. Total impact pressures are reduced because the patient walks gingerly and the period of both hind and forefoot contact is increased. However under prominent and unprotected metatarsal heads there are pressure concentrations which may be twenty times normal in dynes per square mm.
Figure 2. Deep cleft in skin betweenprolapsed metatarsalheads.
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Figure 3a. Retraction of toes m e a n s that they cease to take weight in the kick-off phase of walking. Note also the 'centre-forward' callosity under the second metatarsal head.
Figure 3b. Callosity under the second metatarsal head has broken down and a sinus has formed.
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Because of the toe deformity, pressure lesions develop on the dorsum of the toes from rubbing on shoes and may ulcerate. On the plantar aspect of the foot the prolapse of the metatarsal heads leads to two sets of lesion. One is the formation of clefts in the skin between the metatarsal heads which may become involved by fungus infections (Figure 2). More serious is a sequence of changes which takes place under the metatarsal heads. The increased pressure in the skin and subcutaneous tissue under a metatarsal head leads first to callosity formation. Characteristically, one of the first to form is under the second metatarsal head, the so-called 'centreforward' callosity (Figure 3a). Callosities under the third and fourth lateral metatarsal heads may follow. If the patient continues to walk despite pain, bruising occurs and may eventually break down to form a sinus which is fistulous down to and sometimes into the metatarsal joint (Figure 3b). Secondary infection is common. Medical treatment (rest, antibiotics) is seldom more than temporarily successful. Surgery after a suitable cleaning up of the operative field will be needed. Sometimes (Figure 4) nature attempts to correct the increased pressures on the metatarsal heads. Instead
Figure 4. Miss I.H. Rheumatoid arthritis since childhood. Development of fluid filled adventitious bursae under the metatarsal heads.
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of atrophy and ulceration, adventitious bursae appear becoming distended with fluid, sometimes strikingly so. A hydraulic cushion has thus been substituted for the natural cellular fibro fatty-sponge cushions and should not be aspirated or removed. The great toe
Hallux valgus is the characteristic deformity of the great toe occurring as frequently as other changes in the forefoot (Vidigal et al, 1975). It is an exaggeration of the hallux valgus so commonly seen in many women, and some men. It is accompanied by increased metatarsus primus varus caused by the progressive bow-stringing effect of the flexors. Similar changes of quintus varus and metatarsus quintus valgus cause a total widening of the transverse diameter of the metatarsal region, increasing shoe pressures over the bunion and bunionette areas. At first the hallux valgus closes the natural gap between the first and second toes. Later the second toe has to move to accommodate the big toe. It does so usually by overriding it, although occasionally this displaced big toe lies on top of the others. Later still the hallux subluxes downwards at the MTP joint (Figure 5) and often this is accompanied by rotation (hallux valgus et tortus) so that the pad of the big toe points laterally. As with the metatarsal heads, skin pressure lesions lead to subcutaneous atrophy, ulceration and occasional fistula formation or more rarely to the formation of protective adventitious bursae. It scarcely needs elegant imaging methods to discern the altered patterns of pedal pressures--they are written on the patient's feet with a corresponding moulding of the interior of the shoe. Nevertheless a thermogram (Figure 6) picking up the areas of reactive hyperaemia after walking, can be very revealing.
Figure 5. Plantar subluxationof the hallux.
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Figure 6. Black and white direct and computer contoured thermograms of reactive hyperaemia in rheumatoid feet. Note the abnormally high temperatures under the left midtarsal area, both metatarsophalangeal areas and the cold spot under the left heel caused by redistribution of foot pressures.
The net effect of these changes is that the toes cease to become operative and often make no imprint at all on walking on a foot-print mat. In some patients, either spontaneously or as a result of surgery, the 1st metatarsal joint becomes stiffened and then the whole force on the first ray at the kick-off phase of walking falls on the 1st interphalangeal joint. Abnormal dorsiflexion of this joint later leads to an atrophy of the cushion tissue of the pad of the big toe and is followed by a pressure callosity. The fifth toe
The packing together of the toes causes, first, quintus varus, then an overor under-riding of the fifth toe with respect to the fourth. If the toe is very protuberant, successful shoe fitting is impossible and amputation may be needed.
COMPLICATIONS A F F E C T I N G THE FEET The most common is oedema, making shoe fitting difficult. There are a number of causes--these include high protein inflammatory oedema associated with the active synovitis and low-protein o e d e m a from dependency or compression of venous and possibly lymphatic return by synovial cysts at knee or hip. Fluid retaining non-steroidal anti-inflammatory drugs may increase oedema and there may be on occasions a contribution from acute synovial rupture at the knee or ankle releasing inflammatory joint fluid into the tissues. The tendency to oedema is increased by the sedentary life forced on the unfortunate sufferer. Additionally, abnormalities of capillary permeability, identified by Jayson and Barks (1971) occur. Foot o e d e m a in rheumatoid arthritis responds to diuretics to some extent and up to a kilogram of fluid can be removed from legs (Kalos et al, 1974).
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Figure 7.
Rheumatoid arthritis and vasculitis--nail edge lesions in toes.
Rheumatoid vasculitis is not uncommon presenting usually as small vessel occlusion with patchy necrosis over pressure areas. Nail edge lesions, common in the fingers in rheumatoid arthritis, are only occasionally seen in the toes (Figure 7). Rarely, major vessel blockage occurs, with widespread ulceration and gangrene. Rheumatoid vasculitis affecting the feet was at one time commonly associated with a mixed sensory-motor peripheral neuropathy--adding to the patient's miseries. But in the last ten years this has become rare. Corticosteroid can cause dermal collagen atrophy in the feet as elsewhere with thin transparent and easily bruising skin and dilated unsupported capillaries.
Midtarsal joint Although less common than talo-calcaneal or MTP joint involvement, the midtarsal joint can be a source of great discomfort, responding only to surgery. All rotational movements of the forefoot become painful and no shoe or orthosis or local steroid injection gives more than partial and temporary relief, once necrosis of the talonavicular joint has occurred (Figure 8).
OTHER FORMS OF ARTHRITISIN THE FEET Deformities, resembling those of rheumatoid arthritis are occasionally seen in chronic Reiter's syndrome whether sexually acquired or post-dysenteric, although less often eroding bone. In the earlier stages, inflammatory oedema around tendon sheaths in the foot may cause considerable periosteal reaction
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Figure 8. X-ray of mid-tarsal joint-destruction of talo-navicular articulation.
around the metatarsal shafts seen on X-ray, but this is non-specific and is seen sometimes in m o r e severe and active rheumatoid arthritis of the feet. There are four commonly observed heel lesions in arthritis. Large rheumatoid nodules, under the heel or on the achilles tendon are confined to rheumatoid arthritis (Figure 9a and b) are confined to rheumatoid arthritis. Erosive bursitis of the achilles tendon bursa can be seen in all these conditions. A diffuse Achilles insertional tendinitis is, however, confined to seronegative spondylarthropathies and is H L A B27 related. Tenderness under the heel, in the calcaneal spur area, is either idiopathic or related to seronegative arthritis although the underlying bony change namely the development of a forward pointing bony spur seen on X-ray is often to be noted in late rheumatoid arthritis as it is in those who have never had arthritis.
Scleroderma and Raynaud's disease Raynaud's disease causes spasm or occlusion of the digital vessels and to a lesser degree can lead to poor nutrition of the tissues with shrinkage of the soft tissues. Some degree of contracture of the joint may occur but the biggest changes are associated with progressive systemic sclerosis (scleroderma). The whole foot may develop a shrunken rigid structure with a tendency to ulcerate and with little effective cushioning over bony prominences even if the joints are not contracted. The requirement is for a fully cushioned and well insulated shoe. Similar changes may occur in Werner's syndrome.
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(a)
(b) Figure 9. Rheumatoid nodules under thc heel (9a) and on the achilles tendon (9b).
The tangential foot X-ray In the assessment of metatarsophalangeal joint changes the tangential foot X-ray can be very helpful. In this, the beam of X-rays is directed to the metatarsal area of the sole of the foot as tangentially as possible, the radiographer arranging his plate so that the toes are dorsiflexed. Tangential X-rays show the position of the anterior metatarsal arch, the position and structure of the sesamoids and the degree of inferior erosion and spike formation on the metatarsal heads in relation to the covering skin and subcutaneous tissue (Gheith and Dixon, 1973).
TREATMENT There is no single treatment for 'the' rheumatoid foot but much can be done
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to help, but only after correct analYsis of the causes of pain, and depending on the availability of various medical, orthotic and surgical treatments. There is a demonstrated need for multidisciplinary foot clinics, and not just concentrating on arthritis, for once such a clinic is opened an enormous variety of foot problems will be referred, varying from congenital and acquired deformities to patients with central and peripheral neuropathies as well as arthritis. A physician and an orthopaedic surgeon, a chiropodist and an orthotist should be available. Such clinics are expensive to run and must be carefully organized. They should be secondary referral clinics, i.e. patients referred to them must have had a full medical or surgical examination elsewhere and be provided with up-to-date X-rays of the feet. Preferably, these should be taken with the feet in weight bearing position. This is particularly important for mid-tarsal and hindfoot problems. The tangential X-ray can also be ordered with benefit. General medical conditions, or problems with joints elsewhere which might interfere with surgery of the foot, must be detected. Then a combined decision is made as to the correct line of treatment. Often this will be conservative. The development of lightweight shoes using modern microcellular rubber soles and heels and foam insoles which can cushion the foot has been perhaps the greatest advance. Women with relatively early arthritis of the feet can often manage with sandals in the summer and fur-lined boots in winter. For moderately severe problems, modular 'depth' shoes are available in several widths, lasted more deeply than normal to accommodate a foam or custom-made insock. (Insocks to be worn inside a patient's own shoes are often and uselessly prescribed--they merely take up more room inside a shoe already too tight because of foot swelling.) More severe deformities need individually fitted shoes either made by traditional bespoke shoe making techniques or, more cheaply, to plaster of Paris models of the patient's foot. Some of the worst deformities will require shoe making skills not often available (Munzenberg, 1985) and see Chapter 10). Active arthritis in foot joints can often be treated by local injection therapy, using a long-acting corticosteroid local anaesthetic mix (Dixon and Graber, 1981). Chiropodists can help with pressure- and chafing-relieving pads and protectors. Rheumatoid arthritis surgery has been remarkably successful for severe deformities of the feet particularly where one or more metatarsal heads are prominent in a rigid foot. Forefoot arthroplasties are time-consuming and require quite prolonged hospitalization, but balancing osteotomies are simple and in suitable patients can give signal relief. A similar experience in connection with diabetic foot problems has shown that a multi-disciplinary approach can cut down morbidity and amputation rates with positive costbenefit implications (Edmonds et al, 1986). PREVENTION A N D SOCIAL POLICY
There is no evidence yet that rheumatoid arthritis can be prevented but there is evidence that the morbidity associated with rheumatoid arthritis
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foot i n v o l v e m e n t could be r e d u c e d . I n M i d d l e E a s t e r n c o u n t r i e s , seropositive r h e u m a t o i d arthritis is not u n c o m m o n and X-rays a n d clinical e x a m i n a t i o n s reveal foot i n v o l v e m e n t . B u t the degree of crippling is far less, almost certainly b e c a u s e w o m e n have b e e n less exposed to the c o m p u l s i v e s a l e s m a n s h i p of female foot fashion, high heels which force b o d y weight o n t o the toes, court styles which can only be kept on by c o m p r e s s i n g the toes, to say n o t h i n g of bizarre ' w i n k l e picker' p o i n t e d toe styles. Social policy changes a n d public e d u c a t i o n are n e e d e d to rid w o m e n of such f o o t w e a r just as they have b e e n liberated f r o m the E d w a r d i a n constrictions of tight lacing.
REFERENCES
Bainbridge S (1975-76) National Health surgicalfootware. Office of population censuses and surveys. London: HMSO. Bergstr6m G, Bjelle A, Sundh V & Svanborg A (1986) Joint disorders at ages 70, 75 and 79 years---a cross-sectional comparison. British Journal of" Rheumatology 25: 333-341. Brodie BS (ed.) (1984) Wessex Feet--A Regional Foot Health Survey, vol. 1. Published by Dept of Chiropody Southampton and South West Hampshire Health District, Southampton General Hospital, Southampton. Clarke M (1969) Trouble with Feet. London: Bell. Dixon AS (1981) The physician's foot. Journal of the Royal Society of Medicine 74: 101-110. Dixon AS & Graber J (1981) Local Injection Therapy. Basel: EULAR Publishers. Dunnell K & Cartwright A (1972) Medicine Takers, Prescribers and Hoarders. London and Boston: Routledge and Kegan Paul. Edmonds ME, Blundell MP, Morris ME et al (1986) Improved survival of the diabetic foot: the role of a specialist foot clinic. Quarterly Journal of Medicine 60: 763-772. Gheith SL & Dixon AS (1973) Tangential X-ray of the forefoot in rheumatoid arthritis. Annals" of Rheumatic Diseases 32" 92-93. Hollman C (1960) Shoes for children--A survey of retail shoe shops in the borough of Ealing. British Medical Journal 1: 719. Jayson MIV & Barks JS (1971) Oedema in rheumatoid arthritis: changes in the coefficient of capillary filtration. British Medical Journal 2" 555-557. Kalos A, Dixon AS & Weber JCP (1974) Xipamid in the treatment of oedema in rheumatoid arthritis. Rheumatology and Rehabilitation 13: 81-87. Katz WA (1977) Rheumatic Diseases, pp 182, 183. Philadelphia: JB Lippincott. Munzenberg KJ (1985) The Orthopedic Shoe.Weinheim: VCH Verlagsgesellschaft. Shine IB (1965) Incidence of hallux valgus in a partially shoe-wearing community. British Medical Journal i: 1648-1649. Silman A (1986) Recent trends in rheumatoid arthritis (editorial). British Journal of Rheumatology 25: 328-329. Vidigal E, Jacoby RJ, Dixon AS, Ratliff AH & Kirkup J (1975) The foot in chronic rheumatoid arthritis. Annals of Rheumatic Diseases 34: 292-297.