Biomechanical Analysis and Computer Simulation of Dynamic Head Movement Which Produces Trunk Movements in Quadriplegia

Abstract

Quadriplegic patients use their head to produce a counter-movement against the trunk in their daily living activities such as turning in bed or sitting up bed. It is important to know whether head movement actually affects trunk movement. The purpose of this study is to reveal the influence of dynamic forward head movement of quadriplegic patients.
Fifteen quadriplegic patients underwent motion analyses. They were requested to sit up from a reclining position by only using dynamic head movements. The backrest and the seat were separately mounted on force plates.
Data from the force plates and 3D timehistory data of eight markers attached to the head and the trunk were recorded by “ELETE” gait analysis system.
We confirmed the importance of forward dynamic head movement from the fact that the patients could not sit up by just moving their heads slowly forward from the angle that they could sit up with using dynamic movement.
Data analyses show that the first forward acceleration of the head was supported by the reaction force on the backrest. When the head momentum decreased, the trunk momentum increased. In this way, the head momentum was transferred to the trunk.
We also found a correlation between the maximum backrest angle, from which patients could sit up with using dynamic head movement, and the trunk mobility. The computer link model simulation also shows the importance of dynamic head movement and trunk mobility.