The Hip: Preservation, Replacement and Revision

EBI External Fixators

PreOp Prepartion

- Drill and Screw Sizes: 
   - 6.0/5.0 mm cortical screws require 4.8 mm drill (110 mm long and 30-50 mm thread); 
   - 6.0/5.0 mm cancellous screws require 3.2 mm drill (100-130 length, 40-60 mm thread); 
   - 4.5/3.5 mm cortical screws require 3.2 mm drill; (80-100 length, 30-40 mm thread); 
   - 3.5/3.2 mm cortical screws require 2.9 mm drill; 

- Considerations for Screw Insertion:
   - in near cortex, threads should protrude 5 mm; 
   - in far cortex, threads should protrude 2 mm; 
   - the shank of the screw should clear the skin by at least 1-2 cm; 
   - self tapping screws are available in the kit; 
   - due to the tappered shape of the EBI screws, stability of the screw will be lost if it is partially back out; 
   - in cortical bone, once resistance to insertion is felt at the far cortex, 5 to 6 half turns will cause the tip to protrude 2 mm; 
   - in cancellous bone, contact w/ the far cortex will not be felt and therefore, flouroscopy is require for proper insertion depth; 

- Ex Fix Template:
   - need to select appropriate length to allow for shortening; 
   - sizes are short, standard, and large; 
   - the template is placed over the screw guides during half pin insertion; 
   - following half pin insertion, the screw guides and template is removed, and the definative fixator is applied;

Surgical Technique

- Screw Guides: (not to be confused w/ drill guide); 
   - select proper length; 
   - short guides: (32 mm) used in distal humerus, forearm, and hand; 
   - medium guides: (60 mm) used in tibia; 
   - long screw guide (100 mm) for femur; 
   - insert trocar into screw guide to facilitate seating of guide into bone; 
   - screw guides have relatively sharp edges which can be impacted into the bony surfaces prior to drilling; 
   - proper sized drill guide is inserted into the screw guide; 
   - three lengths: 20, 40, 80 mm; 
   - two inside diameters 3.2 mm and 4.8 mm; 
   - after a half pin, has been inserted, the screw guide is left in position, and the template fixator is then applied over the screw guide; 
   - this allows the remaining screw guides to be placed in the correct position; 

- Drilling:
   - select proper sized bits: 3.2 mm and 4.8 mm; 
   - drill through both near and far cortices; 
   - once, finished, do not remove the screw guide; 

- Screw Insertion:
   - insert proper sized screw; 
   - once resistance of second cortex is met, apply 4-5 half turns and check screw position w/ flouro; 
   - due to the conical shape of the screw, it cannot be backed out once inserted; 

- Apply Ex Fix Template:
   - this helps determine screw placement in both frx segments; 
   - the template is positioned to allow for postoperative dynamization (shortening), and therefore the fixator is not placed in an overly shortened position; 

- Apply External Fixator:
   - if compression / distraction unit is going to be applied, then ensure that end of the cam w/o the hexagonal nuts faces outward; 
   - if compression distraction unit is not goint to be applied, then the end of the cam w/ hexagonal nuts will face outward; 
   - tighten screws to the fixator w/ allen wrench; 
   - manipulate frx w/ the fixator manipulation forceps; 
   - tighten cam nuts w/ the allen wrench; 
   - final locking w/ cam nuts w/ the torque wrench

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

Last updated by Data Trace Staff on Thursday, August 2, 2012 11:55 am