best practice guidelines: wound management in diabetic foot ulcers

ASSESSING DFUsBOX 1: Signs of spreadinginfection (adapted from 49 ) Spreading, intenseerythema Increasing induration Lymphangitis Regional lymphadenitis Hypotension, tachypnoea,tachycardia RigorsFIGURE 6: Necrotic toe whichhas been allowed to autoamputateRISK OF AMPUTATIONArmstrong et al 52 found thatpatients were 11 times morelikely to receive a midfootor higher level amputationif their wound had apositive probe-to-bone test.Furthermore, patients withinfection and ischaemiawere nearly 90 times morelikely to receive a midfootor higher amputation thanpatients with less advancedDFUs. There may also be apossible correlation betweenlocation of osteomyelitisand major amputation, witha higher rate of transtibialamputation reported whenosteomyelitis involved theheel instead of the midfootor forefoot in diabeticpatients 53 .Cultures should not be taken from clinicallynon-infected wounds as all ulcers will be contaminated;microbiological sampling cannotdiscriminate colonisation from infection.Extensive inflammation, crepitus, bullae, necrosisor gangrene are signs suggestive of severefoot infections 50 . Refer patients immediatelyto an MDFT if you suspect a deep or limbthreateninginfection. Where there is no MDFT,the referral should be to the most appropriatepractitioner, notably the person(s) championingthe cause of the diabetic foot, for example anexperienced foot surgeon.Refer patients urgently to a member of thespecialist foot care team for urgent surgicaltreatment and prompt revascularisation if thereis acute spreading infection (Box 1), critical limbischaemia, wet gangrene or an unexplained hot,red, swollen foot with or without the presenceof pain 37,51 . These clinical signs and symptomsare potentially limb- and even life-threatening.Where necrosis occurs on the distal part of thelimb due to ischaemia and in the absence ofinfection (dry gangrene), mummification of thetoes and auto-amputation may occur. In most ofthese situations, surgery is not recommended.However, if the necrosis is more superficial thenthe toe can be removed with a scalpel (Figure 6).Assessing bone involvementOsteomyelitis may frequently be present inpatients with moderate to severe diabetic footinfection. If any underlying osteomyelitis is notidentified and treated appropriately, the woundis unlikely to heal 17 .Osteomyelitis can be difficult to diagnose inthe early stages. Wounds that are chronic,large, deep or overlie a bony prominence areat high risk for underlying bone infection, whilethe presence of a 'sausage toe' or visible boneis suggestive of osteomyelitis. A simple clinicaltest for bone infection is detecting bone by itshard, gritty feel when gently inserting a sterileblunt metal probe into the ulcer 54,55 . This canhelp to diagnose bone infection (when thelikelihood is high) or exclude (when the likelihoodis low) 46 .Plain x-rays can help to confirm the diagnosis,but they have a relatively low sensitivity (early inthe infection) and specificity (late in the courseof infection) for osteomyelitis 46,56 .The National Institute for Health and CareExcellence (NICE) in the UK and IDSArecommend that if initial x-rays do not confirmthe presence of osteomyelitis and suspicionremains high, the next advanced imaging testto consider is magnetic resonance imaging(MRI) 1,46 . If MRI is contraindicated or unavailable,white blood cell scanning combined witha radionuclide bone scan may be performedinstead 46 . The most definitive way to diagnoseosteomyelitis is by the combined findings ofculture and histology from a bone specimen.Bone may be obtained during deep debridementor by biopsy 46 .INSPECTING FEET FORDEFORMITIESExcessive or abnormal plantar pressure, resultingfrom limited joint mobility, often combinedwith foot deformities, is a common underlyingcause of DFUs in individuals with neuropathy 6 .These patients may also develop atypicalwalking patterns (Figure 7). The resultingaltered biomechanical loading of the foot canresult in callus, which increases the abnormalpressure and can cause subcutaneous haemorrhage7 . Because there is commonly loss ofsensation, the patient continues to walk on thefoot, increasing the risk of further problems.Typical presentations resulting in high plantarpressure areas in patients with motor neuropathyare 7 : A high-arch foot Clawed lesser toes Visible muscle wasting in the plantar archand on the dorsum between the metatarsalshafts (a ‘hollowed-out’ appearance) Gait changes, such as the foot ‘slapping’ onthe ground Hallux valgus, hallux rigidus and fatty paddepletion.In people with diabetes, even minor traumacan precipitate a chronic ulcer 7 . This mightbe caused by wearing poorly fitting footwearor walking barefoot, or from an acute injury.In some cultures the frequent adoption of theprayer position and/or sitting cross-legged willcause ulcerations on the lateral malleoli, andto a lesser extent the dorsum of the foot, inthe mid-tarsal area. The dorsal, plantar andposterior surfaces of both feet and betweenthe toes should be checked thoroughly forbreaks in the skin or newly established DFUs.BEST PRACTICE GUIDELINES: WOUND MANAGEMENT IN DIABETIC FOOT ULCERS 7