[Purpose] It has been shown that an eight-hour joint fixation daily (i.e. for the remaining 16 hours, rats were set free in the cage without joint fixation) for one week induces a joint contracture. The purpose of this study was to investigate the difference between an 8 hours continuous joint fixation and an 8 hours intermittent joint fixation per day (two 4 hours joint fixations) in the development of joint contractures in rats. [Subjects and Methods] The subjects of this study were 34 Wistar rats. On the first day, all of the rats’ right ankle dorsiflexion angles were measured. The right hind limbs of all the rats were fixed in plantar flexion, and then the rats were divided into three groups as follows: Group 1 was in continuous fixation for 24 hours a day; Group 2 was in continuous fixation for 8 hours a day; Group 3 was in intermittent fixation for 8 hours a day. The fixation was performed daily for seven consecutive days. On the last day, ankle dorsiflexion angles of all the rats were measured after the casts had been removed. [Results] The development of joint contractures was statistically significant for Groups 1 and 2. [Conclusion] Our results indicate that 8 hours a day of continuous fixation induces a joint contracture, but 8 hours a day of intermittent fixation does not.

[Purpose] The purpose of this study was to clarify the effects of unweighting the lower limbs on joint contractures.[Subjects] The subjects of this study were ten Wistar rats.[Methods] The rats were divided into one control (C) and three experimental groups. The right ankle joints of the first experimental group were fixed in full plantar flexion (F). The second experimental group's hind limbs were unweighted by suspension (S). The third experimental group's hind limbs were suspended and the right ankle joints were fixed in full plantar flexion (FS). The period of this study was one week. On the first and last days of this study, all of the rats' angles of ankle dorsiflexion were measured.[Results] On the last day, the angles of dorsiflexion of the F and FS groups were significantly smaller than those of the C and S groups. The decreased angles of dorsiflexion of the FS group were significantly smaller than those of the F group. [Conclusion] Our results indicate that unweighting the hind limbs causes severe joint contractures in rats.

[Purpose] The purpose of this study was to investigate how a stretching torque affects muscular contractures. [Subjects] The subjects of this study were 48 male Wistar rats. [Methods] Subjects were divided into 4 groups as follows: Group 1 was the control; Group 2 had muscles in continuous fixation; Group 3 had muscles stretched in the direction of dorsiflexion by a spring balancer set at a torque of 0.3N for a period of 30 minutes after continuous fixation; and Group 4 had muscles stretched in the direction of dorsiflexion by a spring balancer set at a torque of 3.0N for a period of 30 minutes after continuous fixation. Joint fixation periods were for 2 and 4-weeks. Ankle joint range of motion and soleus flexibility were analyzed. [Results] For the 2-week joint fixation, soleus flexibility in Group 4 showed an increase compared with that of Group 3. For both fixation periods, range of motion in Group 4 showed an increase compared with that of Group 3. [Conclusion] For both fixation periods, stretching improved joint range of motion. In the 2-week joint fixation, soleus flexibility improved. However, soleus flexibility did not improve in the 4-week joint fixation.

Purpose] The purpose of this study was to clarify the effects of unweighting the lower limbs on the extensibilities of the skin and soleus muscle around a contracted joint. [Subjects and Methods] Twelve wistar rats were divided into two experimental groups. The right ankle joints of the first experimental group were fixed in full plantar flexion (F). The hind limbs of the second experimental group were suspended, and their right ankle joints were fixed in full plantar flexion (FS). The period of fixation was one week. On the last day, the extensibilities of the soleus muscles and skin of the right ankle joint were measured.[Results] The extensibility of the soleus muscle of the FS group decreased more than that of the F group. [Conclusion] Our results indicate that unweighting the hind limbs of rats may cause severe joint contractures by decreasing muscle extensibility.

[Purpose] The purpose of this study was to determine the relationships of changes in pain and gait after ischemia reperfusion was induced by tourniquet in rats. [Subjects and Methods] The subjects were six ten-week-old male Wistar rats. Ischemia was induced in the left lower limbs of the experimental rats at a pressure of 300 mmHg for 90 minutes. Pain behavior evaluations were measured using the von Frey test in all the rats’ hind limbs. A consistently increasing plantar stimulus was applied until the rats exhibited an escape behavior. For the evaluation of gait, a two-dimensional motion analysis system was used to measure the distance from the calcaneus to the floor (DCF) and toe extension angle (TEA) during gait. The evaluations were performed in the normal state, 3 hours after ischemia-reperfusion, and daily until 7 days after ischemia-reperfusion. [Results] Compared with the normal state, the means of the pain threshold showed a significant decrease until 4 days after ischemia. In addition, both TEA and DCF continued to show a significant decrease at 7 days after ischemia as compared with the normal state. [Conclusion] This study revealed that hyperalgesia occurs after ischemia-reperfusion, and recovery of hyperalgesia occurred earlier than gait dysfunction recovery.