The effect of immobilization on the recovery of rabbit soleus muscle from tenotomy: modulation by chronic electrical stimulation

Abstract

SUMMARYThe effect of unilateral Achilles' tendon section on the soleus muscle of rabbits was examined after 2 and 4 weeks of unsutured recovery. Immobilization of the limb during recovery was also investigated. Following tendon section the limb was immobilized with an ankle angle of 90 deg, and final experiments were performed either after 2 weeks, or after the splints were removed and a further 2 weeks recovery allowed. Remobilized recovery was either allowed to occur naturally or with chronic low-frequency electrical stimulation of the soleus nerve. Achilles' tendon section resulted in very little change in the morphological profile of the soleus, but a marked decrease in tension production. Two weeks following tenotomy, tetanic tension was reduced to 50 % of normal; this reduction persisted for the following 2 weeks of recovery. Imposition of immobilization after tendon section produced gross degeneration of the soleus. The fibres that remained had a mean fibre area of 20 % of control values and displayed an immature staining pattern. This was accompanied by a reduction in tension production to less than 5 % of normal and a marked speeding of contraction. Two weeks of passive recovery following splint removal slowed contraction and improved both the morphological profile and tension production of the soleus. Application of stimulation during this time restored contraction times to normal, reflecting the return to normal fibre-type proportions of this group, and improved the morphological profile and tension production beyond that of the unstimulated group. Thus immobilization worsened considerably the alterations occurring in the morphological and physiological properties of the soleus following Achilles' tendon section. Upon remobilization, chronic stimulation accelerated recovery of both parameters.

Skeletal muscle response to tenotomy

“…Thus, they compared the effect of natural recovery from immobilization, followed by natural recovery augmented by electrical stimulation using implanted electrodes attached to a mini-stimulator. 10 In their immobilization groups, they confirmed similar myopathic changes seen with tenotomy, demonstrating decreased fiber area, decreased fiber occupancy per field, increased numbers of transitional and fast fibers, decreased tetanic tension, and increased rate of contraction and relaxation. The time of total immobilization was directly correlated with the degree of the above changes.…”

“…8 In contrast to the relatively rapid response of the rat soleus muscle, atropy of the rabbit soleus muscle does not reach a significant level until 4 weeks posttenotomy. 10 In the rabbit model, reformation of a distal attachment of the muscle to either the tendon stump or surrounding connective tissue with subsequent application of tension decreases atrophy and improves maximum tension production, a measure of muscle strength. 65,66 Tenotomy, with intact innervation, leads to several changes in muscle contractile function.…”

Continuum of reflex excitability in hemiplegia: influence of muscle length and muscular transformation after heel-cord lengthening and immobilization on the pathophysiology of spasticity and clonus

“…During this period, the soleus is presumably under tension and this stimulates the slowtwitch phenotype as well as sarcomere addition. After 2 weeks, the muscle has lengthened by sarcomere addition and further immobilization at neutral induces muscle atrophy (see Cotter et al 1986Cotter et al , 1988Cotter et al , 1991Barry et al 1994).…”

“…Vrbová (1980) has described the time course for changes in muscle phenotype to be in the order of 3 to 6 weeks, beginning with an alteration in muscle vascularization and ending with a transformation of the myosin ATPase properties of the muscle fibres. Changes in the sarcoplasmic reticulum calcium-uptake mechanism are thought to mediate the rapid relaxation phase of tenotomized and immobilized muscles over a 2-to 4-week period (Barry et al 1994).…”

Caracterização histoquímica das fibras do músculo gastrocnêmio de ratos Wistar submetidos à tenotomia e tenorrafia

“…Com relação à plasticidade muscular esquelética, esta tem sido investigada em diferentes situações, tais como: tenotomia do calcâneo (HNÍK et al, 1963;HNÍK, 1964;KARPATI;EISEN, 1972;BAKER;HALL-CRAGGS, 1980;BAKER;MARGOLIS 1987;JÓZSA et al, 1988;JÓZSA et al, 1990;JAKUBIEC-PUKA et al, 1992;HENRIKSEN;JACOBSEN, 1994, TROOP et al, 1995JAMALI et al, 2000 (JÓZSA et al, 1988;JÓZSA et al, 1990;BARRY et al, 1994;MAYER, 2008), estimulação elétrica (SIMONEAU; PETTE, Entretanto, ainda que a inervação e outras influências extrínsecas, como hormônios, possam modular o tipo de fibra muscular, os efeitos parecem ser limitados por diferentes fatores intrínsecos próprios das fibras musculares (HUGHES; BLAU, 1992).…”