The effect of immobilization on the recovery of rabbit soleus muscle from tenotomy: modulation by chronic electrical stimulation.
The 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.
Barry
J A
JA
Department of Biomedical Sciences, Marischal College, University of Aberdeen.
Cotter
M A
MA
Cameron
N E
NE
Pattullo
M C
MC
D000125:Achilles Tendon / Q000601:surgery*; D000818:Animals; D004558:Electric Stimulation; D005260:Female; D007103:Immobilization; D008838:Microcomputers; D008854:Microscopy, Electron; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology* / Q000648:ultrastructure; D009929:Organ Size; D011817:Rabbits