Use of Motek Medical CAREN Extended to compare the effects of a stance control KAFO in locked and stance modes on walking and tripping.

Stance control knee-ankle-foot orthoses (SCO) are prescribed for people with quadriceps insufficiency to provide stability of the limb during stance phase but to enable knee flexion during swing phase thereby facilitating a more normal gait pattern. ‘Standard’ locked knee-ankle-foot orthoses (KAFO) have been shown to cause unsightly gait compensations (ipsilateral hip hiking and circumduction, and contralateral vaulting) to reduce the likelihood of tripping as well as having a negative impact on physiological aspects.
There is still limited evidence to support the use of SCOs and as the demand for evidence based practice increases, it is of vital importance that all aspects of this technology is monitored and evaluated. The majority of existing research on SCO systems is confined to case studies or case series’. However, there is a trend in the literature which indicates a positive benefit associated with the use of SCOs. This is with respect to:
• increased knee flexion during swing phase
• decreased compensatory movements (gait deviations) to facilitate swing phase clearance
• improved temporal and spatial gait parameters.

Many of these studies were conducted in a gait laboratory which provides an ideal but unrealistic walking environment. In particular, the outside environment presents distractions and a variety of terrains which present trip hazards to people wearing locked knee-ankle-foot orthoses.
The Motek CAREN (Computer Assisted Rehabilitation ENvironment) system is a unique laboratory configuration which permits biomechanical assessment of human movement to be conducted in a manner not previously available to researchers and academics. The system hardware comprises a 6 degrees-of-freedom motion platform, a dual belt force instrumented treadmill, a motion capture system, and a large diameter 180° projection screen for displaying virtual reality environments to participants and the provision of biofeedback. The system also permits fully instrumented 3D biomechanical motion analysis of the walking participant.
Specifically, the study aimed to investigate in normal subjects the differences in gait and the incidence of tripping while wearing a SCO in locked and stance modes. This pilot study also aimed to develop a test protocol which could then be used for patient testing.

Methodology
A virtual reality environment was developed to simulate normal pedestrian environments, thus allowing investigation of the SCO performance during negotiation of complex terrain that more closely mimics “normal” conditions that participants would find in the real-world, as well as simulation of slipping and tripping hazards in a safe and controlled environment. which introduced kerbs to the environment to evaluate the effect of SCOs in gait patterns and the incidence of tripping.
Twenty able bodied subjects, age 18+ were recruited following the application of inclusion and exclusion criteria which related to their general health and to comply with the manufacturers guidelines for the SCO.
Five test scenarios took place during a single test session. Each test scenario took place at an individualised walking speed.
• Test 1: No device worn; participants walked in the Motek system wearing own footwear.
• Test 2: No device worn; participants walked in the Motek system wearing test footwear. Test footwear was required to accommodate the bulk of the foot section of the SCO and its impact on outcome measures required to be ascertained.
• Test 3: Participants walked in the Motek system wearing SCO set in locked mode for stance and swing phase, with test footwear and leg lengths equalised.
• Test 4: Participants walked in the Motek system wearing SCO set in locked mode for stance and swing phase, with test footwear and a 1cm shoe raise on the opposite leg if the participants legs were the same length.
• Test 4: Participants walked in the Motek system wearing SCO set in stance control mode with test footwear.

During tests 1-5 participants were required to walk on a level treadmill at their pre-determined individualised normal walking speed. The software application designed for this project involved the appearance of virtual obstacles (modelled on the size and shape of a typical kerb found on any high street) which participants had to negotiate/step over as they were encountered. The virtual kerbs appeared at a distance of between 3-7 metres in front of participants at a randomly controlled frequency of 6-10 obstacles per minute. Each walking trial lasted for up to 2 minutes. During walking trials lower limb and pelvic kinematics and kinetics were collected as was a “tripping metric” to indicate the frequency with which the participant successfully negotiated the virtual kerbs. In addition to a simple frequency metric, the “severity” of any trips was distilled. That is to say, if the participant clipped the kerb with their toe the distance by which the kerb was not cleared was recorded.