Electromyographically evident changes in skeletal muscles during tibial lengthening in dogs using the Ilizarov method

Twenty-four beagle dogs underwent a lower leg lengthening on the right side of 2.5 cm at a distraction rate of 2 times 0.5 mm per day using a circular fixator system. After a latency phase of 5 days and a distraction phase of 25 days, 12 dogs (30-day dogs) underwent electromyography (EMG) of the gas trocnemius muscle on the lengthened and on the control side. The remaining half of the dogs underwent EMG after a consolidation phase of 25 days follo wing the end of distraction (55-day dogs). During every EMG, at least 20 di fferent muscle potentials were analyzed, and the duration, amplitude, and n umber of phases were determined of each individual potential. The 30-day do gs had significantly longer potential phases on the lengthened side and ins ignificantly smaller amplitudes compared with the control side. Furthermore , we observed a slightly larger number of polyphasic potentials on the dist raction side. In the 55-day dogs, no significant differences were observed in the various parameters between the lengthened and the control side. Comp aring 30-and 55-day dogs, the duration of the potentials on the distraction side was not significantly shorter in the 55-day dogs, and the amplitude s ignificantly higher. These findings could indicate combined neurogenous and myopathic alterations of the muscles during the early distraction phase wh ich will be compensated during the later distraction period and the consoli dation phase by reparative and reinnervation damage. processes, leaving no lasting functional damage.