Knee Ankle Foot Orthoses (KAFOs) are prescribed for patients who have hip and knee weakness, with or without foot pathology, who cannot be adequately managed in a below knee device. Conditions in which this may be common include Polio, Spinal Cord Injury and Stroke. Patients with severe lower limb instability may require their knee to be locked in extension during stance to create a stable limb and enable safe ambulation. Traditional KAFOs keep the knee extended throughout the gait cycle requiring one or more compensatory movements such as hip hiking, circumduction and vaulting to clear the limb during swing phase. These gait deviations substantially increase the mechanical work of walking particularly at hip level. In clinical practice, many patients often reject the use of a KAFO after a short period of time. The literature reports this rejection rate to be as high as 58–78%. Studies have demonstrated that the high rejection rate of KAFOs are primarily due to the increased energy demands of walking with a locked knee.
Darren Pereira and colleagues recently published a paper on the benefits of stance control in this population. The full article can be made available on request or can be found at: Davis, Bach, & Pereira, 2010, The effect of stance control orthoses on gait characteristics and energy expenditure in knee-ankle-foot orthosis users. Prosthetics and Orthotics International: 34(2): 206–215 and the abstract is as follows:
Knee-ankle foot orthoses (SCO) differ from their traditional locked knee counterparts by allowing free knee flexion during swing while providing stability during stance. It is widely accepted that free knee flexion during swing normalizes gait and therefore improves walking speed and reduces the energy requirements of walking. Limited research has been carried out to evaluate the benefits of SCOs when compared to locked knee-ankle foot orthoses (KAFOs). The purpose of this study was to evaluate the effectiveness of SCOs used for patients with lower limb pathology. Energy expenditure and walking velocity were measured in 10 subjects using an orthosis incorporating a Horton Stance Control knee joint. A GAITRite walkway was used to measure temporospatial gait characteristics. A Cosmed K4b2 portable metabolic system was used to measure energy expenditure and heart rate during walking. Two conditions were tested: Walking with stance control active (stance control) and walking with the knee joint locked. Ten subjects completed the GAITRite testing; nine subjects completed the Cosmed testing. Walking velocity was significantly increased in the stance control condition (p50.001). There was no difference in the energy cost of walking (p¼0.515) or physiological cost index (PCI) (p¼0.093) between conditions. This study supports previous evidence that stance control knee-ankle foot orthoses increase walking velocity compared to locked knee devices. Contrary to expectation, the stance control condition did not decrease energy expenditure during walking.
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