The effects of fracture fixation on joint contracture and disuse atrophy in immobilized rat soleus muscle

In the present study, we investigated the effects of fracture fixation on joint contracture and disuse muscle atrophy. We surgically fractured the right hind limbs of male Wistar rats, and then fixed the right ankle joints at maximal plantar flexion for two weeks using dorsal splints. Compared with immobilized healthy and sham operated joints, the fractured joints concomitantly showed highly restricted range of motion and significantly higher degrees of disuse atrophy in soleus muscle; decrease of muscle fiber cross sectional area, development of central core lesion and a change in myosin heavy chain isoforms from slow type myosin to fast type myosin. Therefore, it is suggested that orthopedic fracture fixation induces intense disuse muscle atrophy to aggravate joint contracture.