Effect of rhythm and level of distraction on muscle structure: an animal study.

To determine the optimal rhythm of distraction and level of osteotomy for maximal muscle preservation during limb lengthening, histologic and ultrastructural analysis of the peroneus tertius muscle was performed in 46 goats. Thirty-nine animals with 20% or 30% tibial lengthening at the rate of 0.75 mm per day at each osteotomy level were divided in two groups. The first group included 15 animals undergoing tibial middiaphyseal lengthening with automated distractor producing one (n = 5), four (n = 5), or 720 (n = 5) increments per day. The second group included 24 animals in which lengthening was performed at the proximal (n = 4), middle (n = 6), distal (n = 6), or double (n = 8) level of the tibia with distraction rhythm of three times per day. The remaining seven animals served as controls. Histomorphologic features of the lengthened muscles were characterized by a polymorphous appearance with foci of necrosis, atrophy, and sclerosis scattered among apparently normal muscle fibers. The intensity and dispersion of degenerative changes were in direct proportion to the amount of lengthening but in reverse proportion to the frequency of distraction. Tibial lengthening at the diaphysis caused intense fibroblast proliferation and remarkable muscle sclerosis, whereas metaphyseal distraction was associated with a predominance of muscle tissue regeneration over atrophy and sclerosis. Bifocal lengthening and a more fractionated rhythm of distraction were associated with enhanced preservation of existing muscle fibers and greater regenerative activity of the muscle.

[Regenerative myogenesis of the leg muscles during experimental lengthening]. / Regeneratsionnyi miogenez myshts goleni pri ee udlinenii v éksperimente.

Regenerative myogenesis of an extremity regenerating by bilocal distraction osteosynthesis according to Ilizarov has been studied by light end electron microscopy. During the osteosynthesis, the action of the factor of mechanical tension is observed. Muscles elongate because myogenic cells incorporate into muscular fibers in the area of their attachment to dense connective tissues. The data obtained confirm the role of mechanical tension in spatial organization of cells, in morphogenetic and formation processes.

[Changes in neural conductors and their end organs in the muscles and skin after major procedures of one-stage lengthening of the extremity by the G.A. Ilizarov method]. / Izmeneniia nervnykh provodnikov i ikh kontsevykh apparatov v myshtsakh i kozhe pri bol'shikh odnoétapnykh udlineniiakh konechnosti po G.A. Ilizarovu.

The state of the tibial nerve, intramuscular nervous fasciculi and terminals in muscles and skin has been studied in the canine extremities at large one-stage elongations after G. A. Ilizarov. By means of neuromorphological methods it has been proved that during the distraction in the tibial nerve microscopical areas of overstrain of the nervous fibers are formed. This results in appearance of degenerative alterations both in the nerve itself and in the tissues, which it innervates. Together with the destructive processes, during all stages of distraction in the extremity, regeneration of nervous apparatuses took place. However, reparative processes were poorly manifested during those stages. Only after distraction is stopped (in 6 months--period of the extremity fixation) the regenerative processes predominate. It is possible to suppose that the manifestation degree of degenerative and reparative changes depends immediately on duration of distraction.

[Characteristics of myohistogenesis during experimental mono- and bilocal distraction osteosynthesis]. / Osobennosti miogistogeneza v usloviiakh mono- i bilokal'nogo distraktsionnogo osteosinteza v éksperimente.

Regularities of the skeletal muscle tissue histogenesis have been studied in the canine shin at its elongation by 50% of its initial length by means of the mono- and bilocal distractive osteosynthesis after Ilizarov. Using light and electron microscopy, it has been stated that under conditions of monolocal distractive osteosynthesis, when the strain effort acts in the area of the muscle belly, together with elongation dystrophic and necrotic changes, proliferation of the intermuscular connective tissue and atrophy of myons increase. In a half of a year, after cessation of distraction there is no complete restoration of the skeletal muscle tissue structure. Under conditions of bilocal distractive osteosynthesis, when the conditions of the muscle distortion are comparable to those existing during the period of the extremity growth, cellular type of regeneration in the skeletal muscle tissue predominates. Therefore growth of the muscle fibers is longitudinal, like that of their growth in the process of ontogenesis and the structure of the muscle tissue of the extremity elongated is preserved. The results of the experiment performed demonstrate certain prospectiveness of application of the bilocal distractive osteosynthesis method in practical orthopedics.