Diabetes mellitus has increased in prevalence over the years and now affects 400 million globally.
Diabetic patients are at risk of chronic limb-threatening ischaemia (CLTI) as 25% of them develop a foot ulcer, and 80% of major amputations begin as one.
Many may not experience classic rest pain or prior claudication, and have a falsely raised ankle-brachial index. Poor perfusion, peripheral neuropathy and immunocompromised states lead to delayed presentation, extensive wounds and infections which render limbs unsalvageable.While people are increasingly familiar with the diabetic foot from the media, relatives and friends, delayed presentation is common due to the initial ignorance or unnoticed tissue trauma. Others lack proper foot care, education and surveillance.
CLTI is part of a broad disease spectrum where treating ischaemia, while crucial, is only one determinant of success. Through a case study, this article hopes to show that customised treatment taken on by a multidisciplinary team is the best approach to the disease.
Mr A was 55 years old and a smoker of 30 pack-years, with a body mass index (BMI) of 32. He had been diabetic for five years (HbA1c 10.2%) and underwent coronary bypass at 54 years of age. He has stage 3 kidney disease and an incidental asymptomatic left carotid stenosis for which he declined intervention
Presentation He presented with wet gangrene of his right second to fourth toes, associated with fever and hypotension three weeks after he knocked his toes during a brief syncopal episode.
Amputation Mr. A underwent emergent second-to-fifth-toe ray amputation with a plantar slit to allow drainage of purulent infection. His fifth toe was involved and had osteomyelitis on radiograph.
ImagingBeing a smoker with poorly-controlled diabetes, Mr. A’s lower limb arterial duplex showed multi- level calcified steno-occlusive disease of the common femoral artery (CFA), superficial femoral artery (SFA) and below-the-knee (BTK) tibial disease. He had a toe pressure measurement of 15 mmHg.
Ultrasound arterial duplex of Mr A’s right lower limb
In stable patients, it is preferable to do same-setting revascularisation and amputation. However, when in septic shock, time is of the essence and the removal of the septic source must not be delayed. CLTI may also present as ulcers or abscesses in web spaces and pressure areas from ill- fitted footwear.
Long segment and small BTK tibial vessel disease with poor-to-no below-ankle perfusion is typical of CLTI patients.
Angioplasty rather than bypass is the mainstay of treatment, but without established target outflow, primary amputation to an infection-free, well-perfused level may be the only option.
Use of imaging to guide treatmentIn patients without a palpable femoral pulse and when the proximal inflow cannot be assessed on ultrasound, a computed tomography scan or magnetic resonance aortoiliac is required. Concomitant aortic or proximal disease can be visualised and determines whether a contralateral retrograde or upper limb access is necessary for angioplasty.
In severely stenotic or occluded CFA disease, an open endarterectomy is preferred for a hybrid open- endovascular procedure. It is thus useful to identify a non-calcified proximal ‘clamp-able’ segment and its relation to the inguinal ligament pre-operatively for open surgery.
Imaging can also show acute or subacute features where thrombolysis or thrombectomy with aspiration devices may be required.
Contrast use for imaging and angioplasty may worsen renal function. This can be minimised with the use of carbon dioxide for angiograms, pre-surgery hydration and avoidance of nephrotoxic agents.
Endovascular therapy is well-established for lower limb revascularisation.
A sheath is placed in an access vessel under ultrasound guidance (usually CFA) and a digital subtraction angiogram (DSA) is performed. Intra-arterial heparin is administered and wires are used to transverse vessel lesions so as to deploy balloon(s) across.
Balloon insufflation establishes lumen, treating the stenosis or occlusion.
In long segment disease, it is sometimes necessary to employ a subintimal antegrade flossing with antegrade-retrograde intervention (SAFARI) technique where ‘true lumen’ percutaneous access from two directions is used to ‘cross a lesion’ to obtain a through and through passage.
Increasingly, atherectomy devices are used to achieve luminal gain before balloon angioplasty to reduce vessel dissection.
Stenting is necessary when there is significant or persistent vessel recoil, dissection, high clot burden and perforation. They are costly and surveillance is required as they can re-stenose or occlude over time.
Data for and against drug elution technology (paclitaxel or sirolimus- based) exist.4 These are generally used for short- interval recurrent disease and may add duration to vessel patency.
Angioplasty aims to provide straight-line flow to the wound that is ideally angiosome based, or to re-establish a plantar arch when possible.
When flow cannot be achieved in an intervening segment (eg. SFA) or in stent failure, a bypass option with native vein or graft is possible.
Bypass procedures have higher perioperative risks, longer operative times and hospital stay. They are at risk of wound and graft infection and are subjected to the availability of conduits such as native veins. Native-vein, above-tibial bypasses have the best long-term results.
Bypasses are performed for fitter patients with reasonable premorbid ambulatory status and cardiac ejection fraction.
Mr. A underwent a hybrid procedure consisting of an open common femoral endarterectomy, followed by a bovine patch repair. A sheath was then placed antegrade into the patch to perform the angiogram and angioplasty of the infrainguinal vessels.
Femoral endarterectomy and patch repair along with removed calcified plaque
Angiographic images showing CFA patch puncture, fem-pop disease, balloon dissection, stent deployment and restored flow
BTK-anterior tibial angioplasty, posterior tibial artery SAFARIDistal PTA and common plantar angioplasty
Monitoring and careWound healing requires appropriate culture-directed antibiotics, avoidance of new trauma, maintaining perfusion and optimising care of existing cardiac, renal, glycaemic, ambulatory and nutritional status, while going through on-going rehabilitation.
Prolonged stays with immobility lead to the development of pressure sores and nosocomial infections, and must be avoided.
The antibiotic duration depends on wound progress and the presence of existing infections such as osteomyelitis or bacteraemia. Inflammatory markers are useful adjuncts and an ID physician is often consulted.
Vascular access lines may be needed when prolonged treatment is required but pose a threat when infected and require frequent examination.
Repeat angioplasty may be needed if wound healing is impaired.
Vascular teams, along with dedicated wound nurses and podiatrists perform regular wound inspections, debridement and dressing changes.
A variety of dressing options including antiseptic solutions, cellulose-collagen based, hydro-colloids, vacuum-assisted closure devices and hyperbaric therapy or oxygen delivery devices are available for different types of wounds.
Continued wound careContinued wound care is paramount for success, and step-down facilities such as community hospitals, day care and home-nursing facilitate rehabilitation till patients or caregivers are confident to be independent at home. A wound contracting and granulating well
New heel wounds
Recovery of heel and pressure woundsHeel and pressure wounds are challenging as blood flow is poor and offloading, despite best efforts, may not be possible due to immobility.
Wounds after revascularisation are on a ‘race’ against time as they have a risk of re-infection or deterioration.
Those that granulate well and have infection treated should pursue coverage in the form of skin graft or flap performed by either vascular or plastics surgery.
Wounds that have deterioratedWounds that have healed well with SSG/ flap
Recovery from major limb amputationA timely decision to perform amputation will save lives. However, acceptance can be stressful and requires dedicated physicians, social workers and rehabilitation teams.When the stump heals, many enjoy sepsis- free, excellent quality of life with earlier return to society and eventual prosthesis fitting. Well-healed BKA and AKA stumps – rare complications include flap dehiscence and necrosisExtensive wounds – better off with primary amputation
Mr. A’s wound healed well with split skin graft (SSG) and he regained reasonable ambulation after six months.
Two years on, he required a below-the-knee amputation (BKA) of his other leg when he represented with heel gangrene and calcaneal osteomyelitis. Help was sought late due to depression and worries over job commitments. He eventually required hemodialysis as his kidneys failed.
Fortunately, his forefoot remained well and he eventually learned to walk with a below knee prosthesis.He no longer has open wounds and is able to hold a clerical job. He gets around with a personal mobility device and most importantly, enjoys time with his grandchildren.
The Singapore General Hospital (SGH) Department of Vascular Surgery performs an average of 400 lower limb angioplasties a year and collaborates closely with the Department of Interventional Radiology.
A retrospective review of 3,303 angioplasty procedures performed on 2,402 limbs from 2005 to 2015 showed salvage rates of 75%, 72%, and 62%, and overall survival rates of 79%, 56%, and 34% at 1, 5, and 10 years respectively.
The department performs open and hybrid procedures, manages wounds and treats a variety of renal, carotid and aortic conditions.
A vascular consultation is always advised for CLTI.
The treatment varies depending on comorbidities, ADL function, extent of tissue loss, as well as social background and personal beliefs and attitudes. Limb salvage, while ideal, may not always be possible or permanent.
Many go through great physiological and psychological ordeals, and expenses and caregiver stress put a strain on relationships. Others may seek alternative (harmful) therapy or slide into depression.
GPs have preventive roles and can participate in education, wound and emotional care.
Article contributed by Dr Nick Ng Zhi Peng, Consultant, SingHealth Duke-NUS Vascular Centre & Department of Vascular Surgery, Singapore General HospitalDr Nick Ng Zhi Peng is a Consultant at the Department of Vascular Surgery in Singapore General Hospital. He graduated from the Yong Loo Lin School of Medicine (NUS) in 2011 and completed his surgical training with the SingHealth General Surgery Residency Programme in 2018. He obtained his Masters of Medicine (Surgery) in 2017 and FRCS (Edinburgh) in March 2019. He has an interest in both open and endovascular surgery and hopes to help patients with chronic limb threatening ischaemia have the best possible quality of life.