| Summary: | 碩士 === 國立臺灣大學 === 醫學工程學研究所 === 90 === Gait is the most common activity during human daily living and stepping over obstacles is an inevitable part of daily locomotion. Failure to negotiate successfully the obstacle will result in falls and injuries. A safe and successful obstacle-crossing requires stability of the body provided mainly by the stance limb and sufficient foot clearance of the leading limb. The anterior cruciate ligament (ACL) plays an important role in this activity, providing both the structural stability and sensory feedback of the knee joint. The purposes of the present study were to investigate the control strategies of normal subjects while crossing obstacles and to clarify the roles that the ACL plays in obstacle-crossing by studying ACL-deficient (ACL-D) and ACL-Reconstructed (ACL-R) subjects.
Twelve normal, 6 ACL-D and 6 ACL-R subjects participated in the study. They were asked to cross obstacles with 10%, 20% and 30% of their leg lengths while the kinematic data were collected with a three-dimensional motion analysis system (Vicon 370, Oxford Metrics, U.K.). A planar seven-link model combined with multiobjective optimal control theory was developed and used to simulate the motion of obstacle-crossing.
The model simulation results suggest that minimum energy was not the single objective the three subject groups used during obstacle-crossing. Instead, their control strategies were the best compromise between minimum energy and maximum foot clearance, with a unique fixed weighting ratio between the two objectives for each group. The weighting ratios were not influenced by the height of the obstacle (p>0.05), suggesting that the control strategy for negotiating with obstacles is preprogrammed in the CNS. However, the control strategies for the ACL groups were significantly different from that of the normal group (p<0.05) and there was no significant difference between the strategies for the ACL-D and ACL-R groups (p>0.05). This suggests that ACL reconstruction does not help change the control strategy in ACL-injured patients back to normal, possibly due to the incomplete sensory function of the ACL.
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