The Foot

The static and dynamic forces operating in the foot relate to the weight of the body and the reactions from muscular contraction necessary for balance, movement and adaptation to the nature of the ground surface. Classically, forces are described as operating through two arch systems: the internal, which centres around the first metatarsal, and the outer, which operates through the fifth metatarsal. According to Pietrogrande (1965), the talus is the receiver, transmitter and distributor of these forces along two systems, posteriorly distributed towards the calcaneum, anteriorly through both internal and external pillars of the forefoot and above to the tibia. The magnitude of forces is increased when the foot is dorsiflexed or plantarflexed at the ankle joint. However, there is reason to believe that the distribution is not as simple as this description indicates. Tensile and compressive forces balance across different transmission systems of the foot, which may be likened to an aeroplane in flight rather than a car on the road; there is pitch, roll and yaw.

The predominant symptom causing the patient to consult a specialist is pain arising from disorders of loading of the foot during standing or walking. Congenital and acquired deformities are aggravated by fatigue, age, subsequent injury of the weightbearing tissues, trauma, shoe pressure or even the complications of unsuccessful attempts at treatment. The symptom may relate directly to some obvious area of abnormality involving the integument, the skeleton, a joint or a vascular or neurological condition. Alternatively, the symptom can be diffuse without relation to any particular sign. A disciplined approach to diagnosis is essential.

It will be seen that a number of systemic diseases may present local pathology in the foot. In addition, there is an undoubted relationship between postural abnormalities in the lower limbs and in the vertebral column. The uncertainty as to which is the primary abnormality may remain, but it is useful to give some indication of the possible relationships of lumbago, sacralgia and pain in the knee with transverse and longitudinal postural abnormalities in the foot.

The following mechanisms, which may occur singly or in combination, appear to contribute to pain in the forefoot:

It was Locke who identified the flat triangular forefoot as a separate entity, describing a triangular appearance of the forefoot with transverse splaying of the metatarsals in the same horizontal plane associated with atrophy of the loading area. It becomes accompanied by irreducible complex joint displacements maintained by contractures of the soft tissues and consequent development of metatarsalgia. The convergence of the toes is striking (see Figs.5.9C, E, I, K, L; 18.2D; 18.7B, G, H, J, L).

The second commonest of the painful forefoot syndromes, the flat convex forefoot, supervenes on a metatarsal formula of the Greek type (1 < 2 ≥ 3 ≥ 4 > 5). Protrusion, equinus or both may affect the middle metatarsal heads (see Fig. 11.8).

The convex triangular forefoot arises in a cavovalgus foot and is characterised by a triangular convex appearance of the ball of the foot due to an equinus posture of the central three metatarsals associated with frontal protrusion of the same metatarsal heads. The first and fifth metatarsals are short and diverge. The toes are compressed together; the first and fifth converge, while the central three develop claw deformities. Joint displacements and contractures involving tendons, capsules and skin render the condition irreversible.

The metatarsal formula is usually of square, occasionally of Greek or Egyptian configuration. There is longitudinal balanced or varus pes cavus and the condition is characterised by the appearance of a transverse concavity under the ball of the foot associated with typical callus formation under the first and fifth metatarsal heads, displacements at the tarsometatarsal joint line and displacements of the metatarsophalangeal joints with contractures of the integument and capsulotendinous structures. Initially the foot may be supple with a precavus shape, but the longitudinal cavus progressively increases and deviates into valgus or varus. Rarely, the condition may be associated with a flat contracted foot. As well as the transverse concavity at the metatarsal heads, there may be increased cavus at the level of the talonavicular joint line or at the midtarsus corresponding to the cuneiforms and the cuboid. Increased cavus at the midtarsal level results in a reduction in frontal convexity at the Lisfranc joint line; there follows an associated increase in equinus of the antetarsus generally and an absence of divergence of the metatarsals, so that the antetarsus is maintained compressed as well as in equinus. The metatarsals are parallel, and in the majority of cases, they are of equal length; the central three exhibit a relatively reduced equinus. In these circumstances the cavus of the foot is balanced. In some instances, there is congenital shortening of the first metatarsal, increasing the degree of equinus necessary for the head to reach the ground and achieve collateral stability, in which case the cavus becomes accompanied by a varus posture.

There is a group of forefoot syndromes characterised by convexity of the plantar weight-bearing surface associated with insufficiency of action of the first ray. They may be subdivided as follows:

Selective overloading may be due to any one or a combination of a multitude of factors affecting each metatarsal head and it is important that the etiology should be understood in each individual case so that treatment can be planned accordingly. Arbitrary management without reference to the cause is likely to prove unsuccessful. Some overlap with conditions described in other chapters is inevitable but it is useful to consider this group of conditions together in the interests of complete understanding.

Insufficiency of loading of one or more rays results in overloading of the adjacent heads. The condition can be congenital (aplasia of a metatarsal) or acquired (trauma, infection, or following operation, such as amputation of a metatarsal head).

These little bones shaped like sesame seeds were described by Sommering in his treatise on posteology. Gillette (1874), Retterer (1884), Pfitzner (1890), Tedeschi (1891) (all cited by Testut 1904) and Inge and Ferguson (1933) all contributed to an understanding of their significance. Inge and Ferguson regarded the sesamoids as skeletal structures rather than true bones. They appear early, at about the 12th week of intra-uterine life, and appear to arise by ossification in cartilage. Later, they become surrounded by flexor hallucis brevis. Ossification is completed between the ages of 8 and 11 years.

Pain in the forefoot accounts for about half the patients presenting with disorders of the foot. Of these cases, three-quarters present in women and are due to an alteration of the biomechanics of the forefoot, sometimes with primary pathology, sometimes secondary to disorders of the hindfoot. There is variation in the site of the pain, its degree of localisation, its severity and its mode of appearance. Common features are aggravation on standing and walking, progressiveness and irreversibility. The foot becomes increasingly disturbed during static weight bearing and loses its normal rolling action during gait. Secondary effects are produced more proximally. Without effective treatment, the irreversibility of changes will ruin this organ of static loading and propulsion. Etiology, diagnosis and consequent therapy are intricately related.

The term cavus refers to an increased concavity or hollowness of the plantar longitudinal arch and the transverse arch located in the tarsometatarsal region, as well as under the metatarsal heads. In this chapter, transverse cavus relates to the tarsometatarsal region, longitudinal cavus can refer to the whole arch or its medial or lateral margins, while the term forefoot cavus describes a particular configuration of the metatarsal heads (cf. Chap. 9). Cavus may be accompanied by a coronal (transverse) imbalance of the foot into valgus or varus. Many structural combinations occur, and the etiology is diverse. The following broad classification is convenient for descriptive purposes both from the point of view of origin and treatment:

Abnormal lowering of the plantar longitudinal arch may be associated with obvious neuromuscular deficiency or congenital abnormalities, but must otherwise be labelled idiopathic. The subject is complex and it is difficult to reconcile varying opinions on the chain of events which lead to the abnormality. This applies especially in the idiopathic variety.

Painful conditions of the toes are significant because of their frequency and the common failure of practitioners to recognise their part in the overall context of a foot disorder. It is easy to miss the fact that more serious problems underlie an apparently simple toe disorder. Inconvenience, pain and troublesome infection bring the patient to the doctor, but treatment is likely to be ineffectual if directed only at the site of the symptom rather than the basic source of the disease.

The term hallux valgus is incomplete, for the condition is overall a clinodactyly of the first ray. Nevertheless, the more usual name will be used in this account.

Clinodactyly of the fifth ray is usually of congenital origin, sometimes becoming progressive during adolescence. It is less common than comparable deformities of the other toes. When it occurs in infancy the concerned parent notices supraductus (dorsal overlapping) of the little toe. The condition is easily correctable, and the fifth metatarsal is not in a valgus posture; there is no cutaneous contracture, but the extensor tendon is tight.

Pain relating to the tarsal region generally can be conveniently called tarsalgia. It may be classified according to origin or, for practical purposes, according to site. In this account, the causes of tarsalgia will be described first, and then summarised for diagnostic purposes.

Stability of the ankle and hindfoot is assured by muscles and ligaments, which must be considered together. Normal synergic control is through the proprioceptive Golgi organs in the tendons, which control the associated reflex muscle contraction. The mechanism is complex. It seems clear, however, that when the mechanical force is too sudden for reflex protective stimulation of the muscles, ligaments are likely to be stretched or torn.

It is often difficult to define the boundary between idiopathic arthrosis and trauma. Thus, hallux rigidus and Freiberg-Köhler osteochondritis may be related to microtrauma, and considering the strenuous use to which the foot is put, it is perhaps surprising that osteoarthrosis is not more common. The wearing of poorly adapted shoes and the performing of unsuitable surgical procedures are examples of the abuse to which the evidently robust structures can be subjected. Arthroses are frequent in occurrence, and the failure of one particular component reverberates throughout the organ. Every plan for surgical management of arthrosis must embody a clear appreciation of any overall disturbance.

Hallux rigidus should be regarded as comprising two arthrosic components, one affecting the metatarsophalangeal joint of the great toe, the other the associated metatarsosesamoidal joints. Osteophyte formation and progressive ankylosis involve both sites. The whole foot becomes affected, including integument, muscles and ligaments. The skin loses its normal suppleness and thickness, and there is a reduced amount of local subcutaneous fat. The atrophic capsule becomes greyish in colour and rigid, and is closely moulded to the underlying distorted bone configuration. The capsule rarely hypertrophies, but occasionally some thickened fibres with yellowish concretions are formed within it. Marked atrophy of abductor hallucis and flexor hallucis longus is seen.

This condition was described successively by Freiberg (1914), Köhler (1920) and Pannier (1921). Anatomopathological studies were published by Axhausen (1923), Welflng (1951) and Buchet et al. (1961).

The surgeon is frequently faced with the results of failure of previous operative treatment. Sometimes the procedures have been performed well, in other cases they have been poorly conceived or executed or rehabilitation has not been good. It is now realised that certain operative procedures should be avoided because they lead predictably to development of an iatrogenic condition. In this chapter, some guidance is offered on the solution of such problems in the antetarsus (Fig. 25.1).

In pes talus (sometimes called pes calcaneus), there is persistent hyperdorsiflexion of the foot usually neutral with respect to the leg (simple talus) but sometimes associated with some valgus of the subtalar joint (talovalgus).

Congenital malformations are dependent upon ill-understood genetic factors. Their presentations are polymorphic, and treatment is often difficult or impossible. No attempt will be made here to identify underlying causes, but some indication of appropriate conservative or operative measures will be given for each of the various types encountered.

The os intermetatarseum is, according to Faber (1934), a supernumerary ossicle or an osteophyte developing in the commissure between the first and second metatarsals and articulating with both metatarsals and with the medial cuneiform bone. It is a rudimentary vestigial structure, not an accessory apophysis of the cuneiform. Its reported frequency of occurrence varies between anatomists: thus Pfitzner (1892; quoted by Faber) states an incidence of 12%, while Faber records only 1.2%. I estimate the frequency as being 2%–3%.

Chronic venous insufficiency occurs in obesity and during the menopause and is associated with varicose veins, varicose ulcers and inflammatory phlebitis. It becomes associated with perimalleolar oedema and is aggravated especially in the heavy individual, by prolonged standing on the thickly engorged soles of the feet.

Neurodystrophic metatarsalgia is related to the algodystrophic reflex syndrome. It is also known as Sudeck’s atrophy, and has been given numerous other names, including angioneurodystrophic decalcification, Sudeck-Leriche syndrome, neurotrophic rheumatism or arthropathy, painful foot with oedema and decalcification, sympathetic dystrophic reflex, painful idiopathic decalcification of the foot (Ravault et al. 1959; Ravault and Bouvier 1966), Destot (1911), bony atrophy, post-traumatic algic osteoporosis (Leriche and Fontaine 1930) and algodystrophic sympathetic syndrome (de Seze and Ryckewaert 1954). The painful condition may affect the extremities of the upper or lower limb. Authors agree that it is due to disturbance of the neurovegetative innervative reflexes, usually of the peripheral nociceptive type but sometimes central in origin.

The term “perforating ulcer” was first proposed by Vesignié d’Abbéville. The first description was made by Nelaton in 1852: “a torpid ulceration, painless, without tendency to spontaneous cure, of neurotrophic origin with a protruding epidermal border which is cornified and whitish in colour” (Figs. 31.1, 31.2).

Trophic signs and symptoms characterising the diabetic foot can be the presenting features of the generalised disease, but usually there is an overlap with a known condition, often with unstable ketosis. The presentation can be extremely polymorphic, and while in earlier times involvement of the foot was considered rare, the majority of modern authors recognise its real frequency and gravity, the latter shown by the associated osteo-angioneuropathic disorders. Mirouze (1968) estimated that one diabetic in ten suffers from foot problems.

Tarsal tunnel syndrome is a painful motor and neurotrophic disorder caused by compression of the posterior tibial neurovascular bundle. It was first described by Pollock and Davis in 1932 as a disorder of compression of the posterior tibial nerve consecutive to trauma. Other authors include Fahlung (1946), Roaf (1946), Ward (1948), Keck (1962), Lam (1962), Sidney (1963), Mumenthaler et al. (1964), Ficat (1966) and Serre et al. (1965).

The sinus tarsi syndrome was identified and named by O’Connor (1956) [cited by Brown (1960)]; later writers include Hauser (1962), De-brunner (1960, 1963), Blasnick (1963), Komprda (1966) and Navarre (1966).

Morton neuralgia comprises a painful paroxysmal syndrome emanating from the intercapital metatarsal region and was described in 1876 by Thomas G. Morton (not to be confused with Duddley Morton, who described the convex forefoot; see Chap. 10).

Of the rheumatic inflammatory conditions affecting the foot (rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis and gout), rheumatoid arthritis is the commonest. While the origin remains uncertain, viral and immunological etiologies have been proposed, it is known to affect all peoples commonly living in damp or temperate climates. Women aged 30–40 years are affected most commonly (75% of cases). The inflammatory condition involves the connective tissue, generally leading to extremely incapacitating arthropathies. Most authors agree that the foot is affected in 80%–96% of cases.

Ankylosing spondylitis, otherwise known as rhizomelic spondylosis or rheumatoid spondylitis, is a disease of unknown origin, although recent work has determined a genetic factor: the leucocyte group W27 is found in many patients. According to Bontoux (1967) it can occur simultaneously with or after an attack of psoriasis, Reiter’s syndrome (1916) or Crohn’s disease. It was first described by Connos in the seventeenth century and was more precisely defined by Strumple, von Bechterew and Marie.

Psoriatic arthritis was first described in 1880 by Besnier and Bourdillon; other descriptions were made by Sherman (1952), Loyau (1958), Avila (1960), Wright (1961), Fehr (1967) and Dryll (1973). Bret drew attention for the first time to involvement of the toes.

Gout is a disease of multiple presentation. Joint involvement is common, and signs in the foot often constitute the first manifestation. The cardiovascular system, the alimentary tract, the liver and the kidneys are also affected by the overload of urates and uric acid due to both excessive production and deficient elimination (Sorensen 1969).

Orthotic measures – insoles and special shoes – are essential adjuncts to all other methods of treatment of foot disorders. In order for the measures to be effective, certain requisites must be observed:

Surgery of the foot does not require particularly elaborate instrumentation except for occasional specific procedures. It is convenient to arrange instruments in sets packed in appropriate boxes. The following sets are recommended.

Throughout this book, while certain immediately relevant operative procedures have been described, frequent reference has been made to techniques applicable to realignment of the forefoot. They are summarised in this chapter for convenience.