3D GAIT ANALYSIS

The Gait and Movement Laboratory has a 3D Gait Analysis system. Seven infra red cameras are used to record the position of small reflective balls which are attached to a patients legs. The accompanying software then reconstructs the markers and, following processing, the result is a 3D image of the patient moving. At the same time as the 3D image is produced a series of graphs showing movement of the pelvis, hips, knees and ankles in three planes is produced. This information is called kinematic data.

There is also a force plate in the Gait Analysis Laboratory which is used to collect information about the moments and powers acting at the hips, knees and ankles. This information is collected at the same time as the kinematic data and is called kinetic data.

We can also collect information about muscle activity. This is called electromyography and in order to collect this data we apply electrodes to the surface of the skin over specific muscles and connect these to a pack which transfers the information to the computer. We apply these electrodes at the same time as the reflective markers and the data collected is synchronised with the kinematic and kinetic data.

Benefits:

Movement is very complex and what we see with our eyes may not always be exactly what is going on. The benefit of 3D Gait Analysis is it is an extra tool in analysing this complex movement. The data gives information about the pelvis, hips, knees and ankles in three planes along with the moments and powers which gives a large amount of data compared with that we can get with our eyes or video.

Appointment:

During a 3D gait analysis appointment the patient is asked to wear shorts and t-shirt (the appointment letter will ask them to bring these). We may need to roll the shorts up in order to apply markers to the top of the legs.

The first stage of the analysis is a video with no markers on (similar to video analysis). The patient will be asked to walk up and down the laboratory a few times whilst video data is being collected. If possible we collect data with the patient in barefoot. If a patient has splints or different walking aids we may also record them using these.

The next stage is that small reflective markers are stuck onto bony landmarks on the legs and pelvis. It is important that the markers are applied to the correct points and are aligned correctly and so application of the markers can take up to 20 minutes. With all the markers in position a picture is taken with the infra red cameras with the patient standing in the centre of the room. If all the markers can be seen appropriately then, if EMG data is being collected, the patient has the EMG electrodes and wires attached to them, or, if no EMG is being collected, the walking trials can start.

For the walking trials the patient is asked to walk approximately 10 metres in the laboratory. Whilst the patient is walking data is collected about the position of the markers. Each 10 metre walk is classed as a trial. Multiple trials are collected to ensure that the gait we are analysing is typical of the patient. The patient needs to walk as they would normally. Usually between six and eight trials are collected but the number depends on whether sufficient data has been collected. Less trials will be collected if a patient fatigues very quickly.

For certain referrals we may collect extra trials with the patient using some kind of aid e.g. orthoses

Once sufficient data has been collected the markers are removed and a clinical examination is performed by the physiotherapist. .