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Ilizarov Half Pin Characteristics



- See: Safe Zone of Pin Insertion

- Discussion:
    - whether a ring or unilateral fixator is used, there is some evidence that a better regenerate is formed with the use of titanium half pins rather than transfixation wires;
           - ref: Limb lengthening by callus distraction (callotasis).
    - pin characteristics:
           - ilizarov half pins are 4.0 mm, 5.0 mm, and 6.0 mm in size;
           - appropriate drill sizes;
                 - 2.7 mm drill bit for 4.0 mm half pin;
                 - 3.8 mm drill bit for 5.0 mm half pin;
                 - 4.8 mm drill bit for 6.0 mm half pin;

- Rancho Cubes:
    - allow attachment of 4.0, 5.0, or 6.0 mm half pins to the ring;
    - require use of centering sleeves between cubes and half pins;
    - hexagonal set screws fit thru threaded extremity holes to lock centering sleeves;
    - rancho drill guide and trocar are used to direct drill bits thru cubes;
    - oblique pin insertion:
         - oblique pin insertion enhances stability, especially when half pins cannot be placed at 90 deg to each other;
         - a one hole cube is attached to a post;
         - washers are inserted between the cube and the post which prevents the bolt from blocking the hole;

- Technical Pearls:
    - consider use of titanium half pins inorder to lower the rate of infection;
    - use a small periosteal elevator to carefully elevate the periosteum off the bone surface, so that it does not get caught up in the drill;
    - always use new (sharp drills);
    - in dense cortical bone, stop the drill every few seconds to allow cooling;
    - consider periodically withdrawling the drill to clean out the flutes;
    - irrigation may allow some cooling;
    - consider insertion of an additional half pin which is left unattached to the ring construct;
           - if one pain becomes infected, the extra pin can then be attached to the frame without the need to return to the OR;
    - skin incision:
           - when the fixator has been placed for limb lengthening, consider incising the skin in front of the path that the pin will take during the lengthening;
                 - make a larger incision for the pins closer to the osteotomy site;
                 - the incision will create a weak spot (even after the incision has healed) which will allow the half pins to cut through the skin without creating excessive skin tension