Comprehensive gait analysis is the quantitative laboratory assessment of coordinated muscle function, typically requiring a dedicated facility and staff. At its core is the videotaped observation of a patient walking. Videos can be observed from several visual planes at slow speed, allowing detection of movements not detectable at normal speed. Joint angles can be measured, and various time-distance variables can be measured including step length, stride length, cadence, and cycle time. Electromyography (EMG), assessed during walking, measures timing and intensity of muscle contractions. This calculation allows determination of whether a certain muscle’s activity is normal, out of phase, continuous, or clonic.
Kinematics is the term used to describe movements of joints and limbs such as angular displacement of joints and angular velocities and accelerations of limb segments. The central element of kinematic assessment is some type of marker system that is used to represent anatomic landmarks, which are then visualized and quantitatively assessed during analysis of videotaped observations. Movement data are compiled by computer from cameras oriented in several planes, and the movement data are processed so that the motion of joints and limbs can be assessed in three dimensions. The range and direction of motion of a particular joint can be isolated from all the other simultaneous motions that are occurring during walking. Graphic plots of individual joint and limb motion as a function of gait phase can be generated.
Kinetics is the term used to describe those factors that cause or control movement. Evaluating kinetics involves the use of principles of physics and biomechanics to explain the kinematic patterns observed and generate analyses that describe the forces generated during normal and abnormal gait analysis.
Gait analysis has been proposed as an aid in surgical planning, primarily for cerebral palsy. It is also being investigated as a means to plan rehabilitative strategies for ambulatory problems related to aging, stroke, spinal cord injury, etc.
The Commission for Motion Laboratory Accreditation, a non-profit organization established in 1997, evaluates and accredits motion laboratories within clinical facilities. A multidisciplinary team uses a set of criteria to evaluate laboratories in the areas of administration (e.g., staffing, policies, and procedures), equipment (e.g., accuracy and precision), and data management and reporting (e.g., control and clinical data sets).
The Electrodynogram™ is one of the many proprietary devices used in gait analysis. It is a computerized diagnostic device that quantitatively measures and times the coordination of weight-bearing forces and muscular activity exerted on the feet and legs. In May 2003, the Peak Motus Motion Measurement System (Peak Performance Technologies) was cleared for marketing by the U.S. Food and drug Administration (FDA) through the 510(k) process. This system uses off-the-shelf video cameras and sensors and proprietary software to document human movement in two- or three-dimensional space. The FDA determined that this device was substantially equivalent to existing devices and is indicated for assessment and training of limb or body motion in gait analysis, pre- or post-rehabilitation evaluation, physical therapy, and similar applications.
NOTE: Surface EMG may be used as part of gait analysis, but the two terms are not synonymous.