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- Discussion:
    - along w/ EDC forms tunnel IV;

- Anatomy:
    - origin: dorsal surface of distal half of ulna;
    - insertion:  index finger and EDC tendon at MCP level;
    - action: extension of all phalanges of index finger;
    - nerve: deep radial, C6, C7, C8;
    - synergists: extensor digitorum;

- Exam: evaluated by having the patient make a fist, then extend index finger;

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- Tendon Transfer:
    - extensor indicis sometimes transferred surgically to replace torn EPL tendon;
    - when performing tendon transfers  the following are important:
          - by sectioning EIP  proximal to sagittal hood, one can perform tendon transfer,  & also maintain independent extension of index finger;
    - hazards:
          - be aware that in some situations (RA) the EDC to the index finger may have ruptured, and in this case, extensor indicis transfer is contra-indicated;
          - there are usually very few problems w/ extensor tendon lag if one does not tether or tighten the saggital fibers of the index finger

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Independent index extension after extensor indicis proprius transfer. 

Prevention of extensor lag after indicis proprius tendon transfer. 

Extensor indicis proprius opponensplasty. 

Independent index extension after indicis proprius transfer: excision of juncturae tendinum.