EFFECTS OF EXTERNAL FIXATION AND LIMB LENGTHENING ON PERIPHERAL-NERVEFUNCTION

To identify factors affecting peripheral nerve function during limb le ngthening, serial somatosensory evoked potentials studies were perform ed in 18 goats and correlated with gross appearance of the soft tissue s at necropsy, In 15 goats, a 20% or 30% tibial lengthening was done u sing the Ilizarov apparatus at a rate of 0.75 mm per day and rhythm of 1, 4, or 720 times per day, Three animals served as frame/corticotomy controls, Seven lengthened and 2 control animals maintained normal so matosensory evoked potentials throughout the study, At necropsy, the p eroneal and tibial nerves appeared grossly normal, In one control anim al with irreversible loss of evoked potentials documented intraoperati vely, peroneal nerve impalement by a transfixion wire was identified a t necropsy, Eight lengthened animals experienced significant changes o f peroneal nerve conduction, In 6 of these 8 animals, transfixion wire s were found to be disrupting the nerve in some way, In the remaining 2 animals, no offending wires were identified, but there was extensive diffuse soft tissue fibrosis within the extremity, The rhythm of dist raction did not have an important influence on evoked potential change s during the course of distraction, Although there was a correlation b etween the amount of lengthening performed and the degree of evoked po tentials deterioration, the anatomic relationship between the wires an d nerves was a more important factor in the development of these abnor malities.