Gait analysis

Gait analysis is the process of quantification and interpretation of human locomotion. Pathological gait may reflect compensations for underlying pathologies, or be responsible for causation of symptoms in itself. The study of gait analysis allows these diagnoses to be made, as well as permitting future developments in rehabilitation engineering. Aside from clinical applications, gait analysis is widely used in professional sports training to optimise and improve atheletic performance.

History

With the development of photography, it became possible to capture image sequences which reveal details of human and animal locomotion that are not noticeable by watching the movement with the naked eye. Edward Muybridge was a pioneer of this in the early 1900s. It was photography which first revealed the detailed sequence of the horse "gallop" gait, which is usually mis-represented in paintings made prior to this discovery, for example.

Although much early research was done using film cameras, the widespread application of gait analysis to humans with pathological conditions such as cerebral palsy, Parkinson's disease, and neuromuscular disorders, began in the 1970s with the availability of video camerasystems which could produce detailed studies of individual patients within realistic cost and time constraints. The development of treatment regimes, often involving orthopaedic surgery, based on gait analysis results, advanced significantly in the 1980s. Many leading orthopaedic hospitals worldwide now have gait labs which are routinely used in large numbers of cases, both to design treatment plans, and for follow-up monitoring.

The forefathers of this research are Murali Kadaba, HK Ramakrishnan, and Mary Wootten. Their main papers, dealing with Euler Angles, led to the development of a marker system. This marker system is the predecessor of modern marker systems, such as the ones used in movies.

Equipment and techniques

A modern gait lab has several (five or more) video cameras placed around the walkway, which are linked to a computer. The patient has markers applied to anatomical landmark points, which are mostly palpable bony landmarks such as the iliac spines of the pelvis, the malleoli of the ankle, and the condyles of the knee. The patient walks down the walkway and the computer calculates the trajectory of each marker in three dimensions. A model is applied to compute the underlying motion of the bones. This gives a full breakdown of the motion at each joint.

In addition, most labs have floor transducers (strain gauges) which measure the force between the foot and the floor, including both magnitude and direction. Adding this to the known dynamics of each body segment, enables the solution of equations based on Newton's laws of motion and enables the computer to calculate the forces exerted by each muscle group, and the net moment about each joint at every stage of the gait cycle. Some labs also use skin electrodes to detect the activity of each leg muscle. In this way, a complete mechanical description of locomotion is obtained. Deviations from normal patterns are used to diagnose specific conditions and predict the outcome of treatment. Orthopaedic surgery remains an art as much as a science and the outcome of each case still depends on the interpretation of results and the experience of the surgeon. Options for treatment of cerebral palsy include the paralysis of spastic muscles using Botox® or the lengthening, re-attachment or detachment of particular tendons. Corrections of distorted bony anatomy are also undertaken.

External link

• An introduction to Gait Analysis (http://rehabilitation.medicalengineer.co.uk/Introduction+to+Gait+Analysis.php)