Acquired foot problems

Injury

The foot is one of the commonest sites of injury in the body. Because of its relatively rigid structure a great deal of force is necessary to injure the hindfoot. The forefoot including the toes is relatively exposed and therefore susceptible to injury. Also, the high forces going through the foot mean that it is a common site for stress fractures. The principles of fracture management are discussed elsewhere. The foot does present particular difficulties in diagnosis because of the complexity of local bony and joint anatomy. This means that the importance of careful history taking, examination and investigation cannot be emphasised enough. The commonest missed injury is a tarsometatarsal dislocation.

In all foot injuries the full extent of the injury needs to be appreciated, with soft-tissue injuries often being associated with bony injuries. Post injury rehabilitation is important to treat these elements of the injury.

Infection

Infections in the foot can be considered to be minor and com­mon, or major and fortunately rarer. With a significant proportion of the world’s population remaining barefoot, minor skin trauma is a frequent cause of local infection. In the shod population poor shoe fitting has the same effect. The increased incidence of diabetes means that this is now a potent cause of major infections. With the combination of vascular insufficiency, neuropathy and poor cellular function, infection due to diabetes can be extremely difficult to treat. This has considerable implications for the patient. It is also part of why diabetes and its complications represent the greatest single cost drain on many health services in the world.

A careful history and examination must be aimed at elucidating predisposing factors, assessing the extent of the infec­tion, including evidence of more generalised spread. Even with relatively minor bacterial infections lymphatic spread is not uncommon. This leads to lymphangitis and involvement of regional lymph nodes. Investigations must be aimed at establishing the extent of the infection, the nature of the organism involved and any increased risk factors such as poor peripheral blood supply or diabetes. Wound swabs, culture of discharged material and skin scrapings or nail clip­pings can be helpful in identifying the organism. A full blood count, plasma viscosity, blood sugar and blood cultures can be helpful in determining the exact diagnosis and monitoring the benefit of treatment. Plain X-rays remain the baseline investigation of deeper infection, but newer investigation modalities such as magnetic resonance imaging (MRI) can give extremely helpful information on the deeper spread of infection and particularly address the issue of soft-tissue spread.

Basic principles of management involve rest, elevation, antibiotics and, where necessary, surgical débridement. Reg­ular dressings are needed. Desloughing agents and dressings which keep the recovering granulation tissue moist are important.

Minor infections

These include a variety of extremely common conditions including fungal infections, varrucas, infected blisters, infected bursitis and ingrowing toenails. Associated with ingrowing toenails are paronychia, which need formal surgical drainage. Infections created by chronic or repetitive trauma need the underlying cause treating in order to prevent their recurrence. A good example of this is the ingrowing toenail. This will usually need surgical treatment to get it to settle once infection has been established for any length of time. If the infection is severe simple nail removal maybe sufficient to settle the infection but recurrence is relatively common. Wedge resection of the border of the nail and the associated nail bed is the treatment of choice in most cases; this can be aided by phenolisation. It is important to neutralise the phenol on the nail after application. In some cases complete resection of the nail and nail bed (Zadik’s procedure) may be necessary.

Fungal infections are relatively common and can be important as they can cause generalised discomfort that can be mistaken for mechanical causes of pain. In addition they commonly affect the nails leading to nail thickening and distortion (onychogryphosis) which in itself can lead to mechanical symptoms.

Major infections

Diabetes accounts for a substantial number of the major foot infections seen. These may be superficial, often associated with ulceration. Deeper infection may involve soft tissues only with abscess formation or can involve bones (osteitis or osteomyelitis). This type of infection can also involve local joints (pyogenic arthritis). The presence of poor vascularity and neuropathy further complicates both diagnosis and man­agement. Neuropathy can lead to Charcot changes in the foot, disrupting joint stability and foot architecture (Fig. 31.6). This leads to increased pressure under the sole of the foot due to the loss of the normal capacity of the foot to absorb load. In addition the bony disruption produces a high incidence of prominence under the sole. This then leads to ulceration. There is a progression from this superficial form of infection through deep infection and abscess formation to osteomyelitis. If not brought under rapid control this will go on to gangrene.

Treatment

If ulceration is present without the presence of deeper infection the clear aim is to heal the skin. After desloughing the ulcer and removing hyperkeratotic skin the ulcer can be dressed locally. The application of a skin-tight plaster of Paris changed on a weekly basis will allow the vast majority of ulcers to heal. It also allows the patient to be mobile. Deep infection without abscess formation can be treated by strict rest, elevation, soft-tissue support and antibiotics. Any form of abscess needs to be drained urgently and the deeper tissues thoroughly débrided. Ulcers which are deeply penetrating in certain sites are more of a problem than elsewhere. The heel is a particular problem in that ulcers lead to a permanent loss of the heel pad. Once an ulcer is healed the use of appropriate insoles and shoes can prevent further ulceration this is much more difficult to achieve when the ulcer has been in the heel.

When fixed deformity occurs as a consequence of neuro­pathy or Charcot changes due consideration should be given to corrective surgery. The stage of development of the Charcot changes has to be considered. The changes progress through three stages. Stage 1 involves generalised inflam­mation and fragmentation of bone. In stage 2 the inflammation starts to settle and the bone starts to show signs of healing. In stage 3 the bone consolidates. Once the changes become stable, surgery to correct deformity, produce stability and reduce any high pressure points can be undertaken.

Ultimately if tissues are clearly not viable then an appropriate amputation should be planned. This should be undertaken at a level where there is a realistic chance of the wound healing.

Other serious infections

Probably the commonest serious ‘primary’ infection is seen in the madura foot. The causative organism of this is Nocardia madurae; this is a filamentous organism similar to actinomyces. World-wide its incidence is still high, affecting particularly populations in the Asian subcontinent and in Africa who go barefoot. It is also has an increased incidence in other areas of the world including southern USA, the South American states and the West Indies. The organism almost certainly gains access to the foot through minor penetrating injuries or splits in the skin. Subsequently the foot forms multiple painless nodules, which ultimately form vesicular eruptions. These ulcerate and form sinuses. These then become secondarily infected. Treatment involves rest, elevation, and antibiotics for the secondary infection and protracted treatment with dapsone or similar agents. Ultimately if the infection persists and leads to disability then amputation can be considered.

Other types of major infection include tuberculosis, bacterial osteomyelitis and/or arthritis, and finally infections such as guinea worm.