Effect of Unweighting the Hind Limbs of Rats on Joint Contractures

Abstract

[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.

Study on change of rat soleus extensibility caused by reduction in joint movement with unweighting of the hind limbs

“…On the last day of this study, the ankle dorsiflexion angles in the FS group were significantly less than that in the F group. The results of the ankle dorsiflexion angle in this study were the same as in previous studies 15 , 16 ) . Therefore, also in this study, it was clarified that unweighting the lower limbs caused severe joint contractures induced by joint fixation.…”

“…When ankles were immobilized in full plantar flexion for one week, the ankle dorsiflexion angles were severely decreased by unweighting the lower limbs 15 , 16 ) . In the joint contractures caused by joint fixation for one week, the skeletal muscle composed approximately 80.5% of the proportion 17 ) .…”

“…All treatments for hind limb suspension were performed for the FS group. The pain in the rat’s tail during hind limb suspension may have affected the joint contracture 15 ) . Therefore, insertion of a Kirschner wire to the rats’ tails were also performed on the C and F groups.…”

“…Unweighting the lower limbs from the microgravity environment of the universe may cause joint contractures in the human body 8 ) . Furthermore, joint movement decreases with hind limb suspension 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ) during an animal experiment model that reproduces the unweighting of the lower limbs 9 ) . From this, it is considered that unweighting the lower limbs might cause joint contracture in humans as well.…”

“…From this, it is considered that unweighting the lower limbs might cause joint contracture in humans as well. Therefore, in a previous study 15 , 16 ) , we performed a combination of hind limb suspension and joint fixation 3 , 4 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ) , an animal experiment model that reproduces the reduction of joint movement. As a result, it was shown that the occurrence of joint contracture when performing joint fixation and hind limb suspension was more pronounced than when compared with only joint fixation.…”