Development and Assessment of a Biocybernetic Power Assisted Bionic Knee Joint Mechanism(II)

The conventional above-knee prosthesis (i.e. mechanical knee joint mechanism) design have a well-known feature of passive knee flexion and extension construction, the trajectory of instant center of rotation (ICR) throughout the entire range of knee flexion and extension different from the normal semicircular ICR trajectory for the tibiofemoral joint during spontaneous walking, therefore, the conventional above-knee (AK) prosthesis can not restore the normal gait pattern. In addition, the passive mechanical knee joint constuction of the conventional AK prosthesis design, allow the hip flexor govern the hip flexion movement during walking. It make the amputee to swing his prosthetic leg out of the way which produce a compensatory mechanism cause abnormal gait and excessive energy consumption during walking. Besides, the hinge of conventional AK prosthesis with mechanical, hydraulic or pneumatic locking systems for controling knee joint damping will only ensure knee joint stability under a constant speed rotation. Otherwise, the abnormal kinesiology reponse and fall will occur. In addition, intraskeletal impact forces generated by body movement are directly transmitted from the pelvis through conventional above-knee prosthesis will cause a higher concentration force at the contact surface between the socket and the relatively soft living bone. The higher contact force and continuous impact phenomena may induce pain or tissue necrosis. To overcome the drawbacks of the traditional design of AK prosthesis, this three-years research project will focus on the development and clinical assessment of a biocybernetic power assisted AK bionic prosthesis. The aims of the first year is to use the Zebris three-dimension motion analysis system to construct a gait pattern database for normal subjects and single leg AK amputates. The step length, stride length, cadence, velocity, ground reaction force, electromyography (EMG) of single leg muscles and natural gait pattern correlated electromyograph will be collected. Follow by the design of the biomimics pneumatic socket and power-assisted mechanism for AK prosthesis. The main components of hardware include pneumatic controlled socket (straight and spiral form) and four-bar linkage knee mechanism (rolled cable type, power cylinder type). Once the prototype of the biomimics pneumatic socket and power-assisted above-knee prosthesis are developed, system integration and functional validation tests will be performed. In the second year, stump electromyography detection, biofeedback and control interface for the power-assisted above-knee prosthesis will be developed. The dynamic model and the gait pattern based control strategy for AK prosthesis will also be constructed. The electromyography feature identification scheme and control chips developed in subproject IV will be integrated. On the other hand, human body segment motion-based power generation system will be developed. After that, system integration and validation tests will be followed. In the third year, the power-assisted AK prosthesis will be integrated with below-knee prosthesis (i.e. mechanical ankle joint mechanism) developed in subproject III to construct a total biocybernetic power-assisted lower extremity prosthesis. Follow by the functional tests to verify the flexion /extension range of knee joint, ankle dorsiflexion/plantarflexion/inversion/eversion range of motion and knee joint coordination of the designed power-assisted AK prosthesis. Finally, the protocol for future clinical assessment tests will be developed. By completing this research project, novel design of the biocybernetic power-assisted above-knee prosthesis with features of power-assisted biocybernetics, biomimics pneumatic socket, socket with simulated muscle massage mechanism, biofeedback control strategies will be constructed for AK amputee in enhancing their functional capabilities and quality of life. In addition, the biocybernetic power-assisted below-knee system developed in subproject III will be further integrated to become a totally biomimic artificial lower extremity prosthesis.

Project ID:PB9907-12654
External Project ID:NSC99-2221-E182-050