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Limb Lengthening: Distraction Histiogenesis

- See:
       - Discussion of Limb Lengthening
       - Limb Lengthening Fixators
       - Post Op Care in the Ilizarov Method: (by Dr. Mangal Parihar)
       - management of tibial bone defects

- Osteotomy Considerations:
    - first described by DM Bosworth (SGO 1938), which has since been refined;
    - metaphyseal osteotomy:
         - many authors do not feel that preservation of the medullary circulation is a critical step, and therefore the classic Ilizarov corticotomy (sparing medullary canal) need not be performed;
         - osteotomy is performed at the metaphyseal diaphyseal junction which allows enough room for secure fixation of the cancellous fragment and yet still has good regenerate potential (good blood supply and large surface area);
         - "afgan type" of osteotomy involves percutaneous placement of a Gigli saw beneath the periosteum, which allows percutaneous osteotomy;
         - disadvantages:
                 - complete osteotomy disrupts medullary bone and its blood supply;
                 - as pointed out by Brutscher, et al (1993), osteotomy caused delayed onset of bone growth on the ventral and medial sides of the tibia, which corresponds to areas of diminished vascularity;
         - The Role of Corticotomy and Osteotomy in the Treatment of Bone Defects Using the Ilizarov Technique
    - corticotomy:
         - only cortical surface of bone is cut, leaving the medullary surface intact;
         - allows reliable tubular bone growth at 1 mm per day;
         - as compared to osteotomy, corticotomy allows faster progression of new bone growth;
         - the main difficulty with corticotomy is not knowing whether the corticotomy is complete; 
         - ref: Distraction osteogenesis. A comparison of corticotomy techniques.
    - pitfalls:
         - lengthening should never be attempted through a previous fracture site;
         - in general, the half pins can be inserted before the corticotomy site, but the half pin nearest to the corticotomy should not be inserted until
               after the corticotomy is completed;
               - this will reduce the chance that the corticotomy will cause a frx through the half pin site;

- Delayed Distraction:
    - angulation (or distraction) of the osteotomy is delayed for a period of about 7-14 days during which time the bone progenitor cells are mobilized;
           - delay 7-10 days for patients younger than 10 years, and delay approx 14 days for patients older than 10 years;
           - distraction can be delayed even longer when the osteotomy has been performed thru cortical bone;
    - delay in distraction allows bone healing to progress thru the acute inflammatory phase and enter into the reparative of bone healing;

- Distraction Phase:
    - see distraction phase discussion by Dr. Mangal Parihar;
    - following latency period, distraction of 1 mm per day (0.25 mm q6 hour) yields most optimal results;
         - distraction less than 0.5 mm / day may result in premature consolidation, whereas more than 2 mm per day over-extends the bone regeneration process;
         - on average distraction procedes at 1 mm per day, but this is influenced by factors such as age, bone vascularity, etc.;
    - if the radiographic appearance of the regenerate contains central radiolucency greater than 8 mm then the distraction may be too fast and conversely, if the central radiolucency is less than 2 mm then the distraction may be proceding too slowly;  
    - radiographs taken at the 4th postoperative week should reveal some callus formation;
           - if callus is not seen, then distraction should be temporarily slowed or reversed;
           - if premature consolidation is present, then consider increasing distraction to 1.25 mm per day;
    - external fixation is then maintained until callus becomes mature;
    - references:
           - The Tension-Stress Effect on the Genesis and Growth of Tissues: II. The Influence of the Rate and Frequency of Distraction
           - Technique: Metaphyseal distraction for lower limb lengthening and correction of axial deformities.  
           - Factors affecting callus distraction in limb lengthening

- Docking Considerations:
     - ref: Autologous Bone Marrow Grafting Combined with Demineralized Bone Matrix Improves Consolidation of Docking Site After Distraction Osteogenesis

- Healing Index: (number of months of treatment per cm of new bone)
    - adults: 1.8 months/cm
    - tibia:
         - children: 0.87 months per cm;
         - adults: 1.5 months per cm;

- Consolidation Phase:
    - see consolidation phase discussion by  Dr. Mangal Parihar;
    - begins at the end of the distraction phase and ends when there is sufficient regenerate bone to permit removal of the fixator;
    - consolidation phase often lasts twice as long as the distraction phase in children and three to four times as long as the distraction phase in adults.

Complications of limb lengthening. A learning curve.

Factors affecting callus distraction in limb lengthening.

Current Techniques of Limb Lengthening.  

Limb Lengthening and Correction of Angulation Deformity: Immediate Correction by Using a Unilateral Fixator

Technique: Metaphyseal distraction for lower limb lengthening and correction of axial deformities.

Femoral lengthening over an intramedullary nail. A matched-case comparison with Ilizarov femoral lengthening.

Limb salvage using distraction osteogenesis. A classification of the technique.

Distraction osteogenesis in the treatment of stiff hypertrophic nonunions using the Ilizarov apparatus.

Year Book: The Tension-Stress Effect on the Genesis and Growth of Tissues: Part I. The Influence of Stability of Fixation and Soft-Tissue Preservation.

Effects of pulsed electromagnetic field stimulation on distraction osteogenesis in the rabbit tibial leg lengthening model. 

Distraction osteogenesis for bone repair in the 21st century: Lessons learned.

Enhancing bone healing during distraction osteogenesis with platelet-rich plasma.