Neuropathic Ulceration (Mal perforant)

- See:
      - Charcot Changes in the Diabetic Patient 
      - Diabetic Foot Menu

- Pathophysiology:
    - effects of neuropathy are simply those of the insensate foot;
    - in the last century the commonest cause of the insensate foot was syphilis, whereas it is now diabetes;
    - caused by insensitivity and pressure, typically includes stocking distribution of sensory loss, beginning with pain and temperature, is characteristic;
           - these neuropathic changes can occur even the diabetes is even if glucose is under good control and even if there is no arterial ischemia; 
    - as neuropathy becomes more severe there is paralysis of the intrinsic muscles of the foot, leading to the development of claw toes and malperforans ulcers beneath metatarsal heads (see claw toes and metatarsalgia); 
    - hyperglycemia not only directly damages peripheral nerves but also indirectly damages nerves thru microvascular damage;
    - within microvascular system, excess superoxide molecules causes loss of normal nitric oxide function, resulting in vasoconstriction and nerve ischemia;
    - numerous studies have demonstrated impaired sympathetic control of vasoconstriction in neuropathic diabetes;
           - hyperglycemia is associatted with increased skin blood flow;
           - conversely, improved glucose control promotes normalization of flow;
           - autonomic neuropathy results in same increase in skin temperatures seen after surgical sympathectomy but there may be underlying critical ischemia
    - once protective sensation is lost, the risk of foot ulcerations increases by a factor of 7 because of the increased vulnerability to unrecognized trauma;
    - pt w/ neuropathy who has no pain in his foot may continue to walk on small traumatic lesion, such as blister, making it much worse;
    - it is often the case that the patient with a neuropathic foot will show at least some Charcot changes or will have a bony prominence and the combination of insensate foot and bony prominence leads to soft tissue ulceration;
    - differential diagnosis: (peripheral neuropathy
    - references:
           - Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings

- Examination of the Diabetic Foot:
    - 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;

- Radiographs:
    - neuropathic changes may be present;
            - in early stages, may be inpossible to distinguish from osteomyelitis;
            - have high index of suspicion when a pt presents w/ signs of acute infection, & x-ray changes c/w OM but has no penetrating ulcer;
            - bone scan will be positive w/ both infection and Charcot;

- Non Operative Treatment:
    - management of infection (see antibiotic menu and osteomyelitis in the diabetic patient);
          - even if osteomyelitis is not present, soft tissue infection will prevent ulcer healing;
    - management of neuropathic joints
          - acute Charcot patient requires 2-3 months of total non-wt bearing until the X-rays of the foot show good healing;
    - management of ischemia: restoration of arterial perfusion
          - correction of edema will increase perfusion;
    - management of blood glucose: ulcers will not heal with poorly controled blood glucose;
    - management of ulcerations:
          - prevention of plantar ulceration:
                  - once ulcerated, areas heal with scar tissue that is less vascular and less elastic than native tissue, and therefore prevention of ulcerations is essential;
          - treatment includes protection from wt bearing, casts, splints, and later shoewear with a double upright PTB brace; 
          - healing agents:
                  - regranex (becaplermin): recombinant human derived growth factor;
                  - dermagraft (Advanced Tissue Sciences, Inc., La Jolla, Calif.)
                  - apligraf (Organogenesis, Inc., Canton, Mass.; Novartis Pharmaceuticals, Hanover, N.J.)
    - references:
             - The Use of Running Shoes to Reduce Plantar Pressures in Patients Who Have Diabetes.  
             - The effect of callus removal on dynamic plantar foot pressures in diabetic patients

- Sugical Treatment:
    - if foot cannot be kepted out of trouble with an appropriate shoe, then bony prominences can be debrided, or shape of foot can often be changed surgically; 
    - local debridement: 
            - marginal hypertrophic skin surrounding ulcers are regularly debrided; 
            - unroof all encrusted areas; 
            - inspect the extent of deep tissue destruction 
            - establish depth of ulcer (does it go to bone) 
    - ankle:
          - references:
               - External fixation for treatment of Charcot arthropathy of ankle: a case report.  
    - hindfoot:  
          - note that a hindfoot equinus will worsen midfoot break down (consider achilles tenotomoy and lengthening if contracture is present);
    - midfoot:
          - rocker bottom of a healed Charcot foot flattened to prevent ulceration;
          - mid foot arthrodesis may be required in some instances, but often fails;
          - references:
                  - Deformity following fracture in diabetic neuropathic osteoarthropathy. Operative management of adults who have type-I diabetes
                  - Arthrodesis of the diabetic neuropathic ankle joint.
                  - Salvage, with arthrodesis, in intractable diabetic neuropathic arthropathy of the foot and ankle.
                  - Talonavicular Dislocations and Midfoot Arthropathy in Neuropathic Diabetic Feet: Natural Course and Principles of Treatment
                  - Midfoot Ulcers Treated with Gastrocnemius-Soleus Recession 
                  - Midfoot Charcot Arthropathy with Improvement of Arch After Achilles Tendon Lengthening: A Case Report 

    - forefoot: (see metatarsalgia)
          - neuropathy leads to atrophy of intrinsic muscles of the feet leading to claw and hammer toes;
          - clawing of the toes draws the plantar metatarsal fat pad distally, reducing the cushioning effect underneath the metatarsal heads; 
          - achilles tenotomy / gastroc recession:
               - metatarsal ulcerations may be due to relative equinus contracture
               - achilles tenotomy may allow heel to bear more wt, and thus relieve the forefoot ulceration; 
                       - distal incision: - vertical percutaneous stab is made along the midline over the Achilles tendon 4 cm above its insertion; 
                              - blade is turned medially, and the medial one half of the tendon is sectioned;
                       - middle incision: - vertical midline stab incision is made 2 to 3 cm more proximal to the first incision; 
                              - blade is turned laterally, and the lateral one half of the Achilles tendon is incised;
                       - distal incision: - midline stab incision is made 2 to 3 cm proximal to the previous incision, medial one half of the Achilles is incised;
                       - w/ the knee straight, the ankle is dorsiflexed gently until the Achilles tendon begins to slide;
               - references:
                       - Plantar forefoot ulceration with equinus deformity of ankle in diabetic patients: effect of tendo-Achilles lengthening and total contact casting.
                       - Effect of Achilles Tendon Lengthening on Neuropathic Plantar Ulcers
                       - Achilles tendon lengthening, the panacea for plantar forefoot ulceration?
                       - Effect of Achilles tendon lengthening on neuropathic plantar ulcers. A randomized clinical trial
                       - Tendon Lengthening for Neuropathic Foot Problems
                       - Lengthening of the Achilles tendon in diabetic patients who are at high risk for ulceration of the foot.
                       - Percutaneous tenotomy for the treatment of diabetic toe ulcers
          - MTP infectionprominent metatarsal head can be redued with an osteotomy; (see metatarsalgia
               - surgery includes proximal osteotomy thru the metatarsal metaphysis for plantar ulcers; 
               - ref: One stage resection and pin stabilization of first metatarsophalangeal joint for chronic plantar ulcer with osteomyelitis.
          - toe deformities:
               - hammer toes straightened with a tenotomy;
               - claw toes: PIP fusion with shortened extensor lengthening and dorsal MTP joint capsulotomy; 
               - references:
                       - Neuropathic Toe Ulcers Treated with Toe Flexor Tenotomies 
                       - Outpatient percutaneous flexor tenotomies for management of diabetic claw toe deformities with ulcers: a preliminary report.

The diabetic foot: evolving technologies.

The total-contact cast for management of neuropathic plantar ulceration of the foot.

Charcot foot--a technique for treatment of chronic plantar ulcer by saucerization and primary closure. 

The Forefoot-to-Rearfoot Plantar Pressure Ratio Is Increased in Severe Diabetic Neuropathy and Can Predict Foot Ulceration.

The effect of triceps surae contracture force on plantar foot pressure distribution.

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Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Tuesday, February 18, 2014 10:58 am