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Transmetatarsal Amputation

- Discussion:
    - popularized by McKittrick et al. (1949) and by Pedersen and Day (1954)
    - indicated for trauma, tissue loss, infection, and gangrene (limited to toes and not the web space in diabetics);
    - TMA requires shoe modifications & inserts w/ forefoot space replacement.
    - indicated for gangrene or infection involving multiple digits or involving the great toe;
    - amputation may be done for gangrene extending a short distance on dorsal skin past metatarsal phalangeal crease, provided that plantar skin is not comprimised;
    - contraindications: 
             - include forefoot infection, cellulitis, lymphangitis, or dependent rubor involving the dorsal forefoot proximal to metatarsal phalangeal crease;
             - also contraindicated are any gangranous changes on the plantar skin extending proximal to the MP crease;
    - gait function:
             - this results in a bony anterior section which can be difficult to fit;
             - arch often flattens out over time causing further wt bearing problems;
             - toe filler may be sufficient, but often molded arch support is added;
             - extended steel shank adds protection during a role over;

- Technique:
    - skin incision is designed that utilizes a total plantar flap;
    - slightly curved dorsal forefoot incision is carried from side to side at the level of the mid-metatarsal shafts;
    - begin & end incision at the midpoint of the lateral aspect of foot;
    - incision extends to the base of the toes medially and laterally in midplane axis of the foot;
    - plantar incision begins at or just proximal to the MP crease;
    - because greater cross sectional diameter to be covered with skin medially, incision is slightly longer on medial than lateral side;
    - reflect the plantar flap distally to the level of bone section;
    - line of incision will be slightly distal to anticipated line of bone division;
    - skin incision is carried down thru soft tissues to metatarsal shafts, and each shaft is transsected with an air driven oscillating saw approximately 5 mm to 1 cm
             proximal to the skin incision;
    - plantar tissues of the distal forefoot are separated from metatarsal shafts with a scapel;
    - tissues of the plantar flap are thinned sharply, excising exposed tendons and leaving the underlying musculature attached to posterior plantar flap;
    - posterior plantar flap is then rotated dorsally for closure after tayloring or thinning as required to achieve good skin coaptation;
    - simple closure with a deep layer of absorbable interrrupted sutures and a skin closure using a vertical matress technique;
    - if necessary a closed suction drain may be used;
    - well padded short leg plaster cast is the best postoperative dressing since it will control edema and prevent stump trauma;
    - early ambulation after transmetatarsal amputation is not preferred;
    - if wound healing is satisfactory at the first postoperative cast change, 7 to 10 days after surgery;
    - rigid dressing is used until the transmetatarsal flap is well healed, usually 3 to 4 weeks after surgery;

- Shoe Modifications: 
    - this amputation has enough length and necessary muscle attachments to remain functional with shoe modifications;
    - need to reduce peak plantar pressure on the distal stump;
    - extended foot plate:
            - extended carbon fiber foot plate 
            - includes incorporation of a steel shank into the sole of shoe to allow normal toe off ambulation;
            - spring steel shank reproduces the action of longitudinal arch of foot during ambulation;
    - toe filler: custom molded foam pad or lamb's wool can fill the distal empty toe portion of the shoe;
    - rigid rocker bottom sole
    - reference: Can partial foot prostheses effectively restore foot length? 

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Transmetatarsal amputations.   

Transmetatarsal amputation for infection or gangrene in patients with diabetes mellitus.  

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