Healthcare professionals have long been concerned with the assessment of human gait, but only recently were they able to utilize instrumental gait analysis in routine clinical practice for diagnosis, and to guide the selection of treatment methods for complex musculoskeletal and neurological disorders. The development of motion analysis systems has progressed through several stages from simple to more sophisticated, versatile, multimodal, and accurate equipment. Several computerized motion analysis systems are now commercially available for the measurement of human gait. These vary in their design and performance.
The beginning of dynamic calculations of human movement began with Giovanni Borelli in the seventeenth century. Borelli (1608-1679) was a pioneer in the science of locomotion and ‘the first to apply Newtonian principles of mechanics to the movement of the human body’ (Cavanagh and Henley 1993). His work was published in the De Motu Animalium (1682) after his death and can be regarded as one of the most important advances in the development of the understanding of locomotion and muscle action, to which modern analysis is indebted. He wrote about biomechanics and gave detailed descriptions of walking events. Borelli was the first to measure the body’s center of gravity and described how the balance of the body is maintained in walking through the ‘forward displacement of the center of gravity beyond the supporting area’ (Steindler 1953). During the first half of the nineteenth century, most researchers were influenced by Borelli’s ideas.
Historically, the analysis of human gait did not advance very far between classical times and the mid-nineteenth century. This was due to a lack of effective scientific methods of measurement (Murray et al 1964). Consequently, the application of instrumental gait analysis in clinical practice was slow to develop.
Further advances were made with the use of computing technology, video cameras, and improved electromyographic equipment. Instrumental gait analysis has contributed to significant advances in understanding the impact of orthopedic and neurological conditions on human gait (Masdue et al 1997, Polak 1998).
A new era of technology began in the study of the mechanisms of walking with the contribution of the Weber brothers, whose work was based on a sound concept of the mechanical principles of the human body. In 1836, Wilhelm and Eduard Weber in Germany developed the first methods of quantitative measurement of locomotion using observations of the stance and swing phases of gait. They also postulated the pendulum theory of locomotion, which considered the swing phase of the gait as a purely passive movement. Although their research was conducted using primitive methods, it has been argued that it produced reasonably accurate results (Paul 1998). As a result of their measurements, they were able to draw up images of the body structure of a man in the process of walking.
Most of the credit for the early descriptions of the kinematics of gait using photographic methods belongs to Marey in Paris, and to Muybridge in California.
Marey (1885) was the first to use photographic methods to analyze patterns of body movements during gait. He introduced a system called chronophotography to analyze human gait. This yielded figures which are known today as stick-diagrams (Kleissen et al 1998).
Edward Muybridge (1902) was a famous photographer of the late 19th century and should probably be considered the father of human motion analysis. He used a number of stationary cameras in an innovative method to study the motion of a horse running at normal speed. Photography was an effective method of studying human gait for that time. Its main disadvantage was the length of time required to collect and analyze the data (Banta 1999).
During the 1890s in Germany, Braune and Fischer (an anatomist and mathematician respectively) introduced a method of three-dimensional analysis of human movement. Light-emitting markers were used in conjunction with trigonometric measurements to produce pictures with a frequency of 26 images per second. They were able to study the angular displacements of the lower limb joints using this technique. Their work, published in Der Gang Des Menschen (1895), was a major contribution to the understanding of human locomotion (Steindler 1953).
Motion analysis developed further in the following two decades after the advent of photography and the study of the mechanics of gait (i.e. kinetics) began. Kinetics is the study of the forces which act on the joints or body segments and the changes in motion which they produce. Kinetic analysis allows the measurement of the hip, knee, and ankle joint moments and powers (Nordin and Frankel 1989, Harris et al 1994).
Elftman (1939 a&b) studied the energy and resultant forces acting at the hip, knee, and ankle joints provided by the muscles during walking, but he did not calculate the actual muscle and ligament loads. Elftman’s work was limited due to the small sample of subjects that he studied, and also the fact that he used a system of two-dimensional analysis of the human gait.
Research into human gait improved significantly during the 1940s and 1950s. Pioneering work by Verne Inman and his team at the College of Engineering and the Medical School of the University of California made a major contribution to human gait kinematics and mechanics (Whittle 1996b). Inman drew upon an extensive background in engineering, orthopaedics and anatomy to bring together a team specializing in gait analysis. This work covered the displacements and rotations of limbs in space, velocities, and accelerations, external forces on the limbs, energy expenditure, and dynamic electromyography (EMG - the process of recording the myoelectrical activity of muscles during movement). Inman’s work was published by members of the University of California in Human Walking (1981) shortly after his death. This work greatly advanced our understanding of gait kinematics and kinetics, thereby contributing to the improved design of artificial limbs. The second edition was published by Roae & Gamble in 1994.
Bresler and Frankel (1950) calculated the external resultant forces and moments acting at the hip, knee, and ankle during level walking in four subjects. The techniques used in obtaining the data included cine-photographs, a force plate and skin markers to define joint centers.
The use of accelerometers to measure limb accelerations was introduced into biomechanics by several investigators, such as Gage (1964), Eberhart et al (1954), Liberson (1965), and Morris (1973).
Saunders et al (1953) described the excursions of the lower extremities with pelvic movement during gait. They analyzed the main angular displacements of the lower limbs during normal human gait by using high-speed motion-picture photography and also described the six fundamental features of the movement pattern which minimize excursion of the center of gravity. They suggested that these are the most important features which determine whether a movement pattern is normal or pathological. These principles still guide researchers and clinicians in studying human gait.
Close (1959), one of Professor Inman’s students, attempted to increase the clinical value of gait analysis by putting electromyography (single channel) on film. In this way, muscle activation could be studied in the context of observed movements. (Sutherland 1997).
In the subsequent phase of research, involving poliomyelitis patients, three-channel EMG was superimposed on film, in the same way, by Sutherland and his co-workers.
In the 1960s, Murray (1964) and her team in Milwaukee used interrupted-light photography to measure the angular displacement of the hip, knee, ankle, and pelvic tilt. The tests were carried out using white stick diagrams, a mirror positioned overhead to measure locomotion in the sagittal plane, and photographs taken of the subjects walking. Her main interest was in studying the gait patterns of normal men and women, amputees, and Parkinson’s disease patients.
Goniometry was introduced in clinical practice in the 1970s. For example, the sagittal, coronal, and transverse rotations about the hip and knee joints were measured by Johnston and Smidt (1969) in thirty-three healthy men using a three-plane, exoskeletal, electro-goniometric method. Subsequently, Kettelcamp et al (1970) used an electrogoniometer to measure the range of motion in normal and pathological knee joints. They recommended this method for routine clinical practice. However, the limitations of this method, which include errors due to the geometrical offset of the goniometer with respect to the joint center, and due to the mobility of the soft tissues to which the goniometer is strapped, reduced its utility in everyday practice.
Lamoureux (1971) designed a large exoskeletal electro-goniometric device to measure the angular displacement occurring at the hip, knee, and ankle joint. The apparatus was made of two light metal arms that were connected to the two segments of the limb to be measured.
In 1974, Perry used a footswitch and a four-bar linkage goniometer. Perry’s stride analyzer was further developed by Ernest Bontrager, and this and her other achievements in the field, such as work on the specificity of surface and fine wire EMG recordings, are presented in her book Gait Analysis: Normal and Pathological Functions (1992).
Around the same time, Sutherland and Hagy (1972) described the use of a Vanguard Motion analyser to analyse lower limb motion. The cameras operated at 50 frames/sec. in order to freeze the motion of the subject for the analysis portion of the study. The advantages of this method were that no apparatus was attached to the subject, and multiple measurements could be made in the same session. EMG may be superimposed on the motion picture film for simultaneous recording, and the recording of both legs can be made at the same time. The main disadvantage of this system was the time required to collect and analyse the data.
In 1972, Baumann acquired a six-channel EMG with telemetry and a high-speed cine camera that recorded at the same speed as the moving patient, providing more reliable measurements. He collected a vast amount of data on both cerebral palsy and normal children (Sutherland 1997).
At about the same time, Winter et al (1972) at Waterloo University in Canada used a television camera 2-D system to track the movements of markers attached to the limb of a subject and a videotape recorder to record motion data. A computer was used to calculate the values of the joint angles to produce a simple description of the locomotion system during walking. The authors used this system to analyze the gait of 12 subjects at three walking speeds. The main advantage of this system is that the patient is not required either to wear power packs or to be hard-wired, thus allowing the free movement of the subject. However, it is not without disadvantages. It presents only two-dimensional motion data, and in addition, the data collection requires a large computer memory. Winter published influential articles, and a book entitled Biomechanics and Motor Control of Human Movement (Winter 1990).
By 1970 more advanced systems of motion analysis had been developed using computers that document an individual`s upper and lower extremities, pelvis, and trunk motion during movement. These produced a computerized visual image of body movement which could be displayed graphically on the PC screen in less than a minute. The three-dimensional data proved to be useful in research work. This was facilitated by the introduction of a set of small, lightweight markers, either active small infra-red light-emitting diodes (LEDs) or passive infra-red reflective spheres which were placed over selected body landmarks.
Modern computerized systems of movement analysis will be explained in the next part.
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