Optimal time for distraction osteogenesis in limbs with nerve repairs: Experimental study in the rat

The optimal period of time between peripheral-nerve repair and initiation o f limb lengthening procedures has never been precisely determined. In the c linical setting, the surgeon must decide how long the repaired nerves shoul d be allowed to heal before subjecting them to the forces created by the li mb-lengthening process. The authors designed a study to quantify and qualif y the effects of different recovery periods between initial nerve repair an d subsequent limb-lengthening via distraction osteogenesis. Forty-two Sprag ue-Dawley male rats were randomized in two different categories of nerve re pair: end-to-end and nerve grafts. At 4, 8 and 12 weeks after nerve reconst ruction, the femur was submitted to limb-lengthening at a rate of 1 mm/day (0.25 mm every 6 hr). Sciatic Function index (SFI) evaluation indicated that the impact of distra ction was detrimental in the grafted nerves, although they maintained their electrical and morphologic properties at comparable levels to the non-dist racted nerves. Nerves with direct coaptation presented an overall superior regeneration pattern. The findings in end-to-end repairs distracted at 8 we eks and those of grafted nerves at 12 weeks were comparable to those in dis tracted normal nerves. The morphology of the distracted nerves appeared to be more organized than that observed in the non-distracted nerves.