Biomechanics and Motion Analysis

Logic Controlled Electromechanical Free Knee Orthosis

Principal Investigator: Kenton R. Kaufman, Ph.D.
Project Coordinator: Steven Irby — irby.steven@mayo.edu

Figure 29: Bilateral 3-D motion analysis is conducted at self-selected walking speeds

The goal of this project is to design, develop, and test an electronically controlled knee joint that can be installed on a conventional KAFO. This dynamic knee brace system is comprised of a novel wrap spring clutch and electric motor drive, sensors at the foot and knee, electronic control circuitry, and a rechargeable battery pack (Figure 29). The knee joint unlocks during the swing phase of gait and locks during stance phase. The clinical applicability of this project is expected to be improved efficiency of gait in patients with poliomyelitis, spinal cord injuries, myopathic disorders, congenital spinal defects, and acquired paralysis due to infections or vascular insults. Research participants are tested over a six-month period using laboratory based gait analysis and functional testing. Subjective user data is also being collected utilizing a standardized questionnaire. Also mechanical fatigue testing is being conducted to evaluate the reliability of knee joint components and wear-resistant coatings.

At this time field and laboratory testing are underway. Initial kinematic and kinetic data are promising. Metabolic data collection has demonstrated a reduction in VO2 when the dynamic knee brace system is used.

In addition to clinical tests conducted in 2003, mechanical testing and analysis has continued. Three clutches were tested for a total of two million fatigue cycles in early 2003. These tests provided valuable insight to future design considerations to improve cycle life of the components. The custom fatigue testing machine and control software were then upgraded to allow for finer control of the test cycles. Further fatigue tests were completed on three additional clutches treated with commercial surface coatings with an aim of improving friction and wear patterns.

Discussions are underway with industrial entities that work at both the component and complete system levels. We hope to identify a partner with whom we can collaborate on further developing this dynamic knee brace system into a commercially viable product.