External Fixators     

- General Fixator Considerations:
  
- fracture healing:
           - references:
                  - Comparison of osteotomy healing under external fixation devices with different stiffness characteristics.
                  - External skeletal fixation of canine tibial osteotomies. Compression compared with no compression.
                  - Comparison of the effects of compression plates and external fixators on early bone-healing.
                  - General theory and principles of external fixation.    
   - indications:
           - damage control orthopaedics: - timing of orthopaedic surgery in the head injured patient
           - definitive-treatment frame:
           - limb-lengthening and reconstruction:
   - methods to enhance fixator stability 
   - specific fracture:    
           - external fixators for distal radius fractures:
           - external fixators for femoral fractures:
           - external fixators for humeral fractures:
           - external fixators for tibial fractures: (circular wire fixators)

- Pin Care and Prevention of Complications:
   - pin care protocol:
           - soft-tissue compartment should be placed on stretch and the skin should be released if needed so that there is no skin tension;
           - pin sites are covered and pins are dressed with a pressure type dressing (spacers, bolsters, sponges);
           - pin sites are left covered (avoid frequent examinations)
   - pin infections:
           - pin drainage: expect that at least one pin (out of the entire group) will have drainage in 80% of cases;
           - w/ worsening signs of inflammation and drainage can be managed with oral antibiotics;
           - persistent drainage is not an indication for pin removal if there is no radiolucency around the pins;
           - pin loosening: (5-7%)
           - deep infection in 4%
                    - minor pin tract infection requiring removal of pins and curettage: 9%
                    - major pin tract infections requiring pin removal, curettage, and implantation of gentamicin impregnated PMMA beads: 3%
           - references:
                    - External circular fixation: infection rates between wires and conical half-pins with threads outside or inside the skin.
                    - Prevention and management of external fixator pin track sepsis
                    - Chronic osteomyelitis in pin tracks.
                    - Pin-site care: can we reduce the incidence of infections?
                    - Life- and limb-threatening infections following the use of an external fixator
    - pin loosening:
           - pins used w/ external fixators often loosen at pin bone interface;
           - this is due to local mechanical overload (surface resorption induced by micromotion), which tends to be more common in cortical bone
                  rather than in metaphseal bone; 
    - methods to reduce pin loosening:
           - radial preload can significantly reduce surface resorption;
                  - using core pin diameters which are mismatched 0.1 to 0.2 mm larger than the drill diameter (don't confuse pin diameter w/ core diameter);
           - hydroxyapatite coated pins: (see hydroxyapatite)
                  - provides better fixation and decreases frequency of loosening and infection;
           - references:
                  - A comparison of hydroxyapatite-coated, titanium-coated, and uncoated tapered external-fixation pins. An in vivo study in sheep
                  - Hydroxyapatite coating of threaded pins enhances fixation
                  - The thermal effects of skeletal fixation-pin insertion in bone.



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

Last updated by Data Trace Staff on Friday, May 13, 2016 5:03 am