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Examination of the Diabetic Foot

- neurological exam for the neuropathic charcot foot:
      - in exam of the diabetic foot note the neurologic findings are usually distal, symmetrical, and sensory; 
      - absent or diminished tendon reflexes are characteristic findings; 
      - ankle jerk is mainly affected and is absent 4 times > knee jerk; 
      - diminution or loss of vibratory sense in the area of the foot and ankle is also common; 
      - development of claw toes occurs as a result of peripheral neuropathy w/ loss of foot instrinsics
      - clawing of toes may result in anterior displacement of the forefoot fat pad leading to metatarsalgia; 
      - in trying to distinguish between a neuropathic foot and an infection, consider observing the foot after it has been elevated for 5 min;
                   - peristence of erythemia is more consisent with infection (and vice versa, disappearance of erythema is consistent with a Charcot foot); 

- neurological exam for pressure ulceration:
     - mal perforant is typical manifestation of diabetic neuropathy and is characterized by chronic painless ulcer on plantar surface of foot over a pressure point;
     - typically are rimmed by callus, and typically are less necrotic than vascular ulcers;
     - in early stages, ulcer appears over 1st, 3rd, or 5th metatarasal head, but w/ concomitant osseous neuropathic changes, midfoot collapse may occur which may lead to excessive pressure in this region and ulceration;
     - w/ neuropathic ulceration, progression to mixed fiber neuropathy results in loss of light touch & vibration sense & in motor neuropathy;
     - when feet are neglected, necrosis under callus results in ulcer w/ overlying hanging edges, which is painless;
               - infection spreads into underlying joint & proximally into plantar space; 

- sensory testing:
     - EMG nerve conduction testing
       - 10-g (5.07) nylon Semmes-Weinstein monofilament test;
     - vibration testing with a 128-Hz tuning fork (more sensitive predictor of early neuropathy)
      - references:
           - The prediction of diabetic neuropathic foot ulceration using vibration perception thresholds. A prospective study
           - The North-West Diabetes Foot Care Study: incidence of, and risk factors for, new diabetic foot ulceration in a community-based patient cohort. 
           - Clinical examination for the detection of protective sensation in the feet of diabetic patients. International Cooperative Group for Clinical Examination Research.