A rabbit model for studying degeneration and regeneration properties of young striated muscle at different distraction rates.

The present study evaluated the histological changes in the muscle tissue after limb lengthening in skeletally immature rabbits and assessed the effect of different lengthening rates on the regeneration and degeneration properties of striated muscle. Thirteen different lengthening protocols were applied on a total of 16 male domestic white rabbits divided into four groups. The histopathological changes were analysed by a semiquantitative method according to the scoring system of Lee et al. (1993). After evaluation of the five main degenerative parameters (muscle atrophy, internalisation of muscle nuclei, degeneration of the muscle fibre, perimysial and endomysial fibrosis, haematomas), it is evident that rabbits subjected to limb lengthening at a rate of 3.2 mm/day showed more degenerative changes than those limb-lengthened at 0.8 or 1.6 mm/day. Our study showed that the regenerative mechanisms were not endless. If the daily lengthening rate reached the 3.2 mm/day limit, the regenerating ability of the muscle decreased, and signs of degeneration increased significantly.