Introduction to Movement Analysis
What is movement analysis?
Movement analysis is facilitated by the acquisition of objective data that describes a subject’s movement and a physical examination and relevant medical history. Any movement can be studied but the most common clinical analysis is of walking.
Walking involves complex neurological control of limb movements. People with walking difficulties often have different ways of coordinating their movements and adapting to their walking limitations. Clinical gait analysis is used to help understand pathology that affects gait.
Pathologies studied by clinical gait analysis include cerebral palsy, spina bifida, talipes, stroke and amputees. The resulting information can assist clinicians in making decisions about the patient’s management.
Research into human movement is greatly enhanced by the use of an objective tool such as movement analysis, allowing repeated assessment under different conditions. It encompasses many areas including fundamental studies of muscle activity and function, as well as more applied areas such as rehabilitation, development of prostheses and ergonomics. Sports and exercise science is another major area with studies of human movement in athletics, golf and other activities.
A variety of equipment is available for analysis of human movement:
2D video analysis: high quality video footage of coronal (frontal) and sagittal (side) views is included in clinical gait analysis. Video provides a record of the overall gait style and functional ability.
3D computerised analysis: markers are placed on the legs and pelvis and their positions as the subject walks along a walkway are recorded by cameras. By computing the 3D position of the markers the movement of the subject can be regenerated. From this the position of the limb segments and the angles at the joints (kinematics) can be calculated. The kinematics for normal walking are distinctive. The results from subjects with gait disorders can be compared to these to help diagnose the problem and decide a treatment.
Force measurement: The force applied to the floor during walking is measured using one or more forceplates embedded in the floor of the walkway. By combining this with the 3D information, a biomechanical model can be used to find the moments and powers (kinetics) acting at the joints.
Muscle activity and energy cost: electromyography (EMG) equipment can be used to record muscle activity during walking using surface electrodes. Measurements of oxygen consumption or heart rate may be used as a measure of energy consumption.
Attending for movement analysis
The physician (e.g. hospital consultant or G.P.) with responsibility for the patient’s management would normally be the person to make a referral. A full 3D clinical gait analysis would normally require prior authorisation from the local health authority or authorisation from insurers if the patient belongs to a healthcare scheme or has other private insurance arrangements.
A referral letter to the lab will state the reason for the referral e.g. a specific clinical question, request for a baseline measure, pre- or post- operative assessment, etc. From this the lab can ensure they acquire the most relevant data.
On arrival at the lab, staff would explain the process in detail, answer any questions and obtain consent.
Assessment would be tailored to the patient’s functional abilities and any specific clinical questions from the referrer. As a guide, clinical gait analysis would typically comprise a number of elements: (1) a clinical examination to assess joint movement range, muscle strength and tone and bone alignment; (2) video recording of the patient’s walking style; (3) motion capture using a 3D system of the patient walking with markers attached to the lower body to provide an accurate measure of the movement pattern.
During the assessment, emphasis is placed on obtaining good quality representative data, which is later collated in a report to the referring physician.
Labs conduct review sessions in which a multidisciplinary team, usually including a consultant orthopaedic surgeon, physiotherapists and clinical scientists, review the patient’s data before the report is finalised. A report containing the gait data, interpretation and recommendations would be compiled and forwarded to the referrer.
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