Abstract
The objective of the present study was to propose an orthosis of light material that would be functional for the animal and that would maintain only the ankle joint immobilized. Male Wistar rats (3 to 4 months old, 250-300 g) were divided into 2 groups (N = 6): control and immobilized for 7 days. Rats were anesthetized with sodium pentobarbital (40 mg/kg weight) and the left hindlimb was immobilized with the orthoses composed of acrylic resin model, abdominal belt and lateral supports. The following analyses were performed: glycogen content of the soleus, extensor digitorum longus, white gastrocnemius, red gastrocnemius, and tibialis anterior muscles by the phenol sulfuric method, and the weight, fiber area and intramuscular connective tissue of the soleus by the planimetric system. Data were analyzed statistically by the Kolmogorov-Smirnov, Student t and Wilcoxon tests. Immobilization decreased glycogen in all muscles (P < 0.05; soleus: 31.6%, white gastrocnemius: 56.6%, red gastrocnemius: 39%, extensor digitorum longus: 41.7%, tibialis anterior: 45.2%) in addition to reducing soleus weight by 34% (P < 0.05). Furthermore, immobilization promoted reduction of the fiber area (43%, P < 0.05) and increased the connective tissue (200%, P < 0.05). The orthosis model was efficient comparing with another alternative immobilization model, like plaster casts, in promoting skeletal muscle alterations, indicating that it could be used as a new model in other studies related to muscle disuse.
Highlights
Muscular hypotrophy induced by disuse is a condition frequently found in the physiotherapeutic clinic which can occur in association with orthopedic disorders such as ligament ruptures, bone fractures, muscular and medulla lesions, inflammatory processes, degenerative joint and muscular pathologies, as well as in situations in which patients are confined to bed for long periods of time for medical or surgical reasons [1]
Immobilization has been extensively studied, more investigation is still required because of the wide variation in responses resulting from joint position, number of joints immobilized, application time, material used, and whether or not there is load on the limb
The aim of the present study was to propose an orthosis of light material that would be functional for the animal and that would maintain only one joint immobilized, in this case the ankle kept in a neutral position, leaving the knee and hip joints free, allowing weight load
Summary
Joint immobilization induces harmful effects such as muscular fiber hypotrophy, increased connective tissue, loss of muscular extensibility, and limitation of joint movement [2]. Besides these alterations, Hirose et al [3] observed the insulin resistance caused by immobilization compromising the insulin signaling responsible for glycogen synthesis. Immobilization has been extensively studied, more investigation is still required because of the wide variation in responses resulting from joint position, number of joints immobilized, application time, material used, and whether or not there is load on the limb. Nemirovskaya and Shenkman [4] associated hindlimb suspension with ankle immobilization in a neutral position and a platform to lean the limb on. In the Tanaka et al [5] study, suspension was associated with fixing the ankle with steel wire
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