bution, patterns of spread, and frequency of associated ulceration and septic arthritis.
Radiology 2002;22:747, 755. 31.
Sella EJ, Grosser DM.
Imaging modalities of the diabetic foot.
Clin Podiatr Med Surg 2003;20:729, 740. 32.
Ledermann HP, Morrison WB, Schweitzer ME, Raikin SM.
Tendon involvement in pedal infection: MR analysis of frequency, distribution, and spread of infection.
Am J Roentgenol 2002;179:939, 947. 33.
Ledermann HP, Schweitzer ME, Morrison WB.
Nonenhancing tissue on MR imaging of pedal infection: characterization of necrotic tissue and associated limitations for diagnosis of osteomyelitis and abscess.
Am J Roentgenol 2002;178:215, 222. 34.
Bus SA, Yang OX, Wang JH, Smith MB, Wunderlich R, Cavanagh PR.
Intrinsic muscle atrophy and toe deformity in the diabetic neuropathic foot: a magnetic resonance imaging study.
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20 Interventional Radiology in the Diabetic Foot Amman Bolia
INTRODUCTION Over 1 million people in the United Kingdom have diabetes mellitus,1 of whom around 7, 10% will, at some point, develop a foot ulcer.2 This becomes even more significant with the increasing age of the population and as the prevalence of diabetes increases.
Diabetic patients are particularly prone to peripheral neuropathy and peripheral atheroscle- rotic disease, which results in some patients getting foot ulceration and gangrene.
Other con- tributing factors are poor glycaemic control, foot deformities associated with high mechanical pressures on overlying skin, decreased visual acuity resulting in foot trauma, limited joint mobility and also poor-fitting footwear.3 Foot ulceration and gangrene are important causes of morbidity in diabetic patients, and therefore it is important that measures are taken that would eventually lead to healing of the ulcers or gangrene.
Healing of such lesions requires surgical debridement of infected or necrotic tissues and restoration of pulsatile blood flow to the foot.
As occlusive atherosclerotic disease of the tibial arteries is particularly common in diabetic patients, infra-popliteal revascularisation is often required.
This has traditionally been accomplished by percutaneous transluminal angioplasty (PTA) or a surgical bypass, with moderately good results.
More recently, subintimal angioplasty has been practised as an alternative, minimally invasive treatment to recanalise long arterial occlusions, with promising patency rates even in small vessels of the lower leg.
Advanced reconstructive techniques including local or free tissue flap transfers can be used to accelerate healing of large foot wounds after successful revascularisation.
Treatment of diabetic vascular disease is challenging and requires an aggressive multidisciplinary approach with cooperation between diabetologists, interventional radiologists, vascular surgeons and plastic surgeons.
BACKGROUND AND VASCULAR INVESTIGATION There is growing evidence that the vascular contribution to diabetic foot disease is greater than was previously realised.4 Unlike diabetic peripheral neuropathy, peripheral vascular disease
The Foot in Diabetes, 4th Edition. Edited by Andrew J.M. Boulton, Peter R. Cavanagh and Gerry Rayman. C 2006 John Wiley & Sons, Ltd. ISBN: 0-470-01504-7
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BACKGROUND AND VASCULAR INVESTIGATION 239
(PVD) is more amenable to therapeutic intervention.
Patients with PVD will have a low tran- scutaneous oxygen tension (TcpO2 ) on the dorsum of the foot, and PVD has been demonstrated to be a greater risk factor than neuropathy in both foot ulceration and lower limb amputation in diabetic patients.5, 6 The basic pathophysiology of atherosclerosis in patients with diabetes is probably no dif- ferent from that in non-diabetic patients.
However, some of the risk factors are more prevalent in the diabetic population.
It has been shown that compared to non-diabetic patients with PVD, diabetic patients are twice as likely to have disease of the distal popliteal or tibial vessels.7 However, there is no evidence that diabetic patients suffer from more macrovascular disease of the pedal vessels.
Indeed, Conrad8 demonstrated that the pedal vessels of diabetic patients were less frequently affected with atheroma than those of non-diabetic patients.
Nor is there any evidence to support the widely held concept of obliterative microvascular or ‘small vessel’ disease of the diabetic foot.
It is therefore fortuitous that the distal tibial vessels are available and enable recanalisation of long occlusions to be achieved by subintimal angioplasty.
Non-invasive vascular imaging is normally the first-line investigation in patients with PVD.
Whilst in non-diabetic patients the ankle, brachial pressure index (ABPI) is reduced in the presence of PVD, in diabetic patients it can be falsely high due to calcified and non-compliant peripheral vasculature and is therefore unreliable.
Because of limitations of ABPI in diabetic patients with incompressible vessels and medial calcification, toe pressure measurements are of value.
Toe pressure in patients with non-arterial symptoms are between 90 and 100 mm Hg, whereas in the presence of critical limb ischaemia, the pressure drops to below 30 mm Hg.9 Duplex scanning is a fast, cost-effective and non-invasive way of imaging diseased arteries in the periphery, but it is operator dependent.10, 14 The tibial arteries can sometimes be difficult to image, especially in the presence of calcification, oedema, ulceration and bandaging of the legs.
Despite these limitations, it proves an extremely useful investigation and is usually sufficient to base a decision on the mode of intervention for revascularisation, either by surgery or angioplasty.
Magnetic resonance imaging has boosted the non-invasive imaging potential of patients with PVD.
Excellent magnetic resonance angiographic (MRA) pictures can be produced in the majority of patients, with proximal arteries particularly well demonstrated (Figure 20.1).
Accurate demonstration of tibial vessel requires a cooperative patient and a radiologist geared up to providing a good study.
Patients who are incapable of keeping still and are suffering from claustrophobia may not be suitable.15, 16 CT angiography has an application in the intra-thoracic and intra-abdominal vasculature.
As multi-slice and fast scanners become more available, CT angiography may assume greater importance.
Unlike duplex scanning, and like MRA, the study is non-operator dependent, and provides excellent images.
Femoral angiography or, more specifically, intra-arterial digital subtraction angiography (DSA) has been regarded as the gold standard for demonstrating the arterial tree and is par- ticularly good at showing the foot vessels.
However, nowadays, the standard practice in most departments is to use some sort of non-invasive imaging, which is then followed by a diagnostic angiogram that proceeds to an intervention at the same time.
Iodinated contrast media used in angiography are potentially nephrotoxic.
The nephrotox- icity is transient, reaching a maximum at approximately 48 h, and is usually of no clinical significance in patients with normal renal function.9 All patients should have their serum cre- atinine measured prior to angiography.
If the creatinine is raised, but below 300 μmol/l, then
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240 INTERVENTIONAL RADIOLOGY IN THE DIABETIC FOOT
Figure 20.1 This is a composite image of an MR angiogram. It shows an occlusion of the right popliteal artery, extending up to the trifurcation
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ENDOVASCULAR REVASCULARISATION 241
adequate hydration with intravenous fluids is recommended, commencing at least 6 h prior to the intervention. If the creatinine is more than 300 μmol/l, then serious consideration should be given as to whether an alternative modality or contrast agent should be used.