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[Kinetic changes of canine's hindlimbs after fixation of one forelimb].

OBJECTIVE
To establish a three-foot weight-bearing canine model to imitate the biomechanical loading environment of the human's hip joint. To observe and compare the kinetic changes of hind limbs between normal and three-foot weight bearing canines.


METHODS
Using 10 beagles, three-foot weight-bearing canine models were made by fixing unilateral wrist joints at 90 epsilon flexionally. The changes of ground reaction forces and the time of standing phases (Ts) of the hind limbs were compared by 3-D gait analysis pre- and postoperatively.


RESULTS
Canines could walk well with three limbs after the fixation of one fore limb. However, the gait pattern changed tremendously. The canine walked jumpily by raising its head and neck, and the bilateral hind limbs kept contacting ground alternately. Ts of ipsilateral hind limb was (0.48+/-0.04)s, and Ts of contralateral hind limb was (0.46+/-0.06)s. Although, the time durations were increased a little, but there were no significant differences when compared with that of normal canines (0.43+/-0.05)s (P > 0.05). The vertical ground reaction force (Fz) of ipsilateral hind limb was (4.63+/-0.85) body weight, and the Fz of contralateral hind limb was (4.78+/-0.49) body weight. There were significant increases when compared with the Fz of normal canines (3.26+/-0.48) body weight (P < 0.05). The peak acceleration force of the ipsilateral hind limb was (0.80+/-0.30) body weight. There was significant increase compared with that of normal canines (0.72+/-0.13) body weight (P < 0.05). The peak acceleration force of the contralateral hind limbs was (0.68+/-0.22) body weight, there was no difference compared with that of normal canines (P > 0.05). The peak deceleration forces of the ipsilateral and contralateral hind limbs were--(0.26+/-0.14) body weight and--(0.13+/-0.05) body weight separately. They decreased significantly when compared with that of normal canines--(0.43+/-0.13) body weight (P < 0.05). In normal canines, the upper limbs were main load bearing limbs, they could bear 62.8%+/-2.4% of body weight. However, the hind limbs could bear only 37.2%+/-1.8% of body weight. On the contrary, in three-foot weight-bearing canines, the hind limbs became the main load bearing limbs, they could bear 59.1%+/-6.7% of body weight.


CONCLUSION
Three-foot weight-bearing canine model can be used as a candidate animal model to research the effects of biomechanical loading on the progression of hip joint diseases.