Pilot Investigation of the Functional Benefits of Stance
Control Orthotic Knee Joints (SCOKJ)

Steven Gard, PhD, Principal Investigator

Student Investigator:
Angelika Zissimopoulos, MS

Co-Investigators:
Stefania Fatone, PhD and Dudley Childress, PhD, Northwestern University
Martin Kacen, CO, Rehabilitation Institute of Chicago

Funded by: National Institute on Disability and Rehabilitation Research (NIDRR)

Purpose

Traditional orthotic knee joints utilized in knee-ankle-foot orthoses (KAFOs) are either locked or unlocked, depending upon the level of support required. Recently, new orthotic knee joints that allow stance phase control have become available. In the stance-control mode, these joints provide stance phase knee stability while allowing knee flexion during swing. Since there is minimal research examining these devices, the purpose of this study was to investigate the biomechanical and energetic effects of using a stance-control orthotic knee joint.

Method

To eliminate additional effects from pathologies, able-bodied subjects were fitted with a KAFO utilizing Horton’s stance-control orthotic knee joint (SCOKJ®). Gait and energy expenditure data were collected with the SCOKJ® used in three operational modes: locked, unlocked, and auto (which blocks stance phase knee flexion but allows swing phase knee flexion). It was hypothesized that the auto mode gait data would more closely resemble the unlocked mode gait data than locked mode gait data, and that operating the KAFO with the SCOKJ® in the auto mode would yield lower oxygen cost compared to locked knee gait.

Results

Analyses of speed-matched kinematic and kinetic data from nine subjects revealed that orthotic side peak to peak stance phase knee flexion was significantly smaller for the locked mode compared to the unlocked and auto modes and was significantly smaller for the auto mode compared to the unlocked mode. Orthotic side peak to peak swing phase knee flexion was not significantly different between the auto and unlocked modes, but was significantly smaller for the locked mode than for both the unlocked and auto modes. These results were expected since the locked mode prevented knee flexion and the auto mode blocked stance phase knee flexion while allowing swing phase knee flexion. For the locked mode on the orthotic side, all subjects exhibited hip hiking and three subjects utilized circumduction as a means to provide toe clearance during swing phase. These compensatory mechanisms were eliminated in the auto mode for all subjects. Orthotic side knee flexion moments in early stance were smaller for the locked mode compared to the unlocked and auto modes, probably due to the reduced moment arm in the locked mode resulting from the loss of stance phase knee flexion. Additionally, the non-orthotic side hip moments in early stance were significantly larger than the orthotic side moments.

Finally, energy expenditure data indicated that the unlocked mode yielded the lowest oxygen cost while the oxygen costs for the auto and locked modes were not significantly different. It is possible that the auto mode does not reduce energy expenditure as hypothesized or that that the training period was not adequate enough (both in length and style of training) to allow subjects to become completely comfortable with the operation of the device.  However, the benefits from improved kinematic and kinetic patterns may be more beneficial than a reduction in energy expenditure.

Through the use of an able-bodied model, this study illustrated the potential functional effects of using a stance-control orthotic knee joint compared to a traditional locked knee orthosis. Further research is required to verify if a patient population will produce similar results to those from this able-bodied model.

Related Publications

Zissimopoulos, A., Fatone, S., and Gard, S. (2007). The Biomechanical and Energetic Effects of a Stance-Control Orthotic Knee Joint.  Journal of Rehabilitation Research & Development, 44(4):503-514.

Zissimopoulos, A., Fatone, S., and Gard, S. (2007). Stance-Control Knee Ankle Foot Orthoses.  Capabilities, 15(2):1-2.  Northwestern University, Chicago, Illinois.

Zissimopoulos, A., Fatone, S., and Gard, S. (2007). The Biomechanical and Energetic Effects of a Stance-Control Orthotic Knee Joint.  Annual Meeting and Scientific Symposium of the American Academy of Orthotists and Prosthetists, March 21-24, San Francisco, California.

Zissimopoulos, Angelika Nikole (2006). "The Biomechanical and Energetic Effects of a Stance-Control Orthotic Knee Joint," MS Thesis, Biomedical Engineering, Northwestern University.

Zissimopoulos, A., Fatone, S., Gard, S. (2005). Functional Benefits of Stance-Control Orthotic Knee Joints: Preliminary Data.  Children's Memorial Hospital Visiting Professor Symposium, November 4, 2005, Chicago, IL.

Boynton, A. (2002). Reflections of the 2002 NIDRR Scholar: Applying Research in Clinical Practice. Capabilities, Autumn, 11(3):3-4. Northwestern University, Chicago, Illinois.