A 72-year-old lady presents to the clinic concerned that she was walking on the outside of her foot. Clinical examination shows that she has a chronically discharging leg sinus (Fig. 32.1). This had been diagnosed as a varicose ulcer. A radiograph showed evidence of bone destruction (Fig. 32.2).

1 What is the likely cause of the radiological appearances?

2 This lady was suffering from minimal pain yet her ankle progressively adopted a varus deformity. What description is applied to painless arthritis?

3 How would you investigate this lady and what treatment is appropriate?

Fig. 32.1

Discharging sinus

Fig. 32.2

Radiograph of left ankle

Septic arthritis

1 The radiograph shows cystic erosion of the tibial plafond, and the presence of peripheral osteophytes suggested that the joint destruction had developed over quite a long period. These appearances might have occurred in a patient with rheumatoid arthritis, but there were no other features of this condition. A copious discharge of purulent fluid made the diagnosis of a deep-seated infection straightforward.

2 Painless joint arthritis was described in patients with neurosyphilis by Charcot in 1858. The term ‘Charcot joint’ is now used as a generic term for joint destruction secondary to impaired sensation. The changes are most commonly seen in patients with diabetes mellitus although syphilis (tabes dorsalis), syringomyelia and congenital indifference to pain should also be considered.

3 A swab was sent for culture and sensitivity, but no organisms were grown. This was perhaps not surprising as the patient had been on several courses of antibiotics but both her erythrocyte sedimentation rate, at 86 mm/h, and C-reactive protein, at 350 mg/l, were greatly elevated.

Drainage, with curettage of any necrotic material, is required to hasten healing. In this instance, however, such a procedure would almost certainly have destroyed any residual weight-bearing capacity that the patient had, and the end result would probably have been an amputation.

It was no surprise when the microbiologist finally reported that the infection was due to tuberculosis. The patient was commenced on triple therapy (rifampicin, isoniazid and pyrazinamide) and the discharge diminished dramatically. Eighteen months after starting therapy the radiographic appearance was as shown in Figure 32.3. The patient had no pain and was walking in a surgical shoe with a heel flare, albeit using a stick outside. Although the degree of joint subluxation will almost certainly mean that she will need to wear a leg caliper in the future, this would clearly be preferable to either a joint fusion or amputation. A fusion would not only be technically difficult to achieve in the presence of such significant bone destruction, but it is unlikely that the lady would tolerate a further 6–8 weeks in a plaster cast.

Fig. 32.3

Distal tibia and ankle after 18 months’ chemotherapy

Key points

• Some form of neuropathy must be present in patients with a Charcot joint.

• All patients should be tested for diabetes mellitus.

• Consider tuberculosis as a cause of chronic sepsis.

Critical limb ischaemia

1 This is Buerger’s limb elevation test. Under normal circumstances sufficient arterial pressure should exist to maintain an adequate blood supply to the feet and toes even with the limb elevated. However, when there is arterial compromise, i.e. atherosclerosis, the arterial pressure is reduced and the foot is deprived of blood. To carry out this test, the patient should be laid flat and the legs elevated well above the level of the heart and subsequent observations recorded. The limbs should be kept elevated for about 3 minutes and the features observed. The legs are then lowered with the patient in a sitting position and observed for a further 3 minutes.

This is a useful test to use in conjunction with measurement of the ankle brachial pressure indices when calcification of the arteries is suspected.

2 In the presence of significant disease a number of features can be observed.

With the limbs elevated:

• a rapid pallor of the right foot in comparison to the normal limb (see Fig. 33.2)

• a rapid emptying of veins (guttering; see Fig. 33.3)

• an absent or reduced capillary filling time.

With the limbs dependent:

• the rate of refilling of veins will be sluggish on the affected side

• the time taken for the pallor to subside is also relevant and this time is increased on the right side

• there is increased rubor (dusky red colouration) of the foot as a result of prolonged deprivation of oxygen, known as reactive hyperaemia (see Fig. 33.4). Compare the colour with that evident in Figure 33.1.

3 Critical limb ischaemia. This condition threatens life and limb. A suggested pathway of care is illustrated in Table 33.1.

**Table 33.1** Pathway of care for critical limb ischaemia
Symptoms	Pathway
Intermittent claudication without ulceration	Encourage exercise to open up collateral vessels. Smoking cessation. Monitor.
Rest pain	Refer to vascular surgeon. Check blood pressure and cholesterol levels, with appropriate drug management if appropriate.
Ulceration/gangrene	Establish extent of atherosclerosis. Consider intervention such as grafting, bypass surgery or amputation.

In this case, the patient was seen urgently by a vascular surgeon. Specialized investigations including Doppler scanning and a femoral angiogram revealed extensive atheroma in the femoral and iliac arteries. A cross-over graft was necessary from the right femoral artery but although, his peripheral arterial circulation improved to 60% of normal, he was unable to return to work.

Evidence

Lumbar sympathectomy is a minimally invasive procedure with a low complication rate. Three randomized controlled trials have failed to identify any objective benefits for lumbar sympathectomy. However, subjective improvements in symptoms for patients with highly symptomatic critical leg ischaemia have been consistently demonstrated in ten cohort studies, with sustained symptom improvements in approximately 60% of patients. Lumbar sympathectomy should be considered for symptomatic patients with critical leg ischaemia as an alternative to amputation in patients with otherwise viable limbs.

Key points

• Claudication and rest pains are an indication of significant peripheral arterial disease.

• Buerger’s limb elevation is a quick, easy test that does not require expensive equipment.

• It is important to address other risk factors such as smoking, hyperlipidaemia and hypertension.

• Abstinence from tobacco products is the only way to prevent disease progression.

Snake bite

1 The adder (Vipera berus –Fig. 34.2) is the only indigenous venomous snake in the UK and snakebite is rare but still, as elsewhere in the world, potentially lethal. In the US the two main families of venomous snakes are the Crotalidae (pit vipers, including the rattlesnake, cottonmouth and copperhead) and the Elapidae (coral snakes).

After a bite on the foot or ankle there is rapid peripheral swelling and a spreading inflammatory process (similar to cellulitis) will be evident. Haemorrhagic blebs develop at the site of the bite within 6–36 hours. Palpation of the groin will reveal regional lymphadenopathy and systemic effects are soon apparent. Generally the patient will become nauseous, and vomiting, diarrhoea, incontinence, vasoconstriction and pronounced tachycardia are common. Angio-oedema with swelling of the face and tongue leading to airway obstruction and hypotension may be fatal.

2 Investigations should include examination of a blood film and measurement of serum creatine kinase (indicative of muscle necrolysis). Bleeding is rare but may be secondary to thrombocytopenia. An electrocardiograph will exclude any myocardial ischaemia.

3 Supportive therapy is required from the moment of presentation. This should include immobilization of the affected leg in a splint and immediate transfer to hospital. If the snake has been killed then it should be identified on site or taken to the hospital. A stick longer than the snake’s length is required to pick it up, to avoid any further envenomation. Pressure immobilization (by firm bandaging but not tourniquet) is particularly important for bites by snakes of the Elapidae family (coral snakes, kraits and mambas). Adequate analgesia should be prescribed and adrenaline (epinephrine) kept close by in case of anaphylaxis. Envenoming may be quite slow and the patient should be admitted to hospital for at least 24 hours.

4 Antivenom is obtained through the major hospital casualty departments sourced generally from a National Poisons Centre. Care should always be taken if antivenom is administered as this may also induce anaphylaxis.