This protocol is used to evaluate spatial and temporal gait variables of neurological/orthopedic patients and older persons by means of a recently-introduced floor-based photocell system.
Spatial and temporal characteristics of human walking are frequently evaluated to identify possible gait impairments, mainly in orthopedic and neurological patients1-4, but also in healthy older adults5,6. The quantitative gait analysis described in this protocol is performed with a recently-introduced photoelectric system (see Materials table) which has the potential to be used in the clinic because it is portable, easy to set up (no subject preparation is required before a test), and does not require maintenance and sensor calibration. The photoelectric system consists of series of high-density floor-based photoelectric cells with light-emitting and light-receiving diodes that are placed parallel to each other to create a corridor, and are oriented perpendicular to the line of progression7. The system simply detects interruptions in light signal, for instance due to the presence of feet within the recording area. Temporal gait parameters and 1D spatial coordinates of consecutive steps are subsequently calculated to provide common gait parameters such as step length, single limb support and walking velocity8, whose validity against a criterion instrument has recently been demonstrated7,9. The measurement procedures are very straightforward; a single patient can be tested in less than 5 min and a comprehensive report can be generated in less than 1 min.
Walking is one of the most important physical activities in everyday life, and is a main determinant of the quality of life for elderly and patient populations who may present with gait deteriorations. Clinical evaluation of gait function is therefore important to reveal potential alterations induced by aging and/or neurological/orthopedic pathologies, but also to prove the functional benefits of a treatment. Different instruments have been developed for the quantitative assessment of gait parameters, e.g., force plates, video-based 3D motion analysis, body-mounted accelerometers10,11, and instrumented walkway mats or treadmills12. However, these systems are mainly used for research studies rather than for clinical purposes because they are complex to operate, have low accessibility, and fragile sensors.
A floor-based photoelectric system has recently been introduced, which is able to provide a valid calculation of temporal features and 1D spatial coordinates of walking steps. This measuring instrument has several advantages compared to pre-existing systems: it is easy to handle, data are collected very quickly, it is simple to create a detailed report and it is a modular system which means that the length of the system can be changed. Thus, it can be used with confidence to measure within-group changes in longitudinal assessments and between-group differences in cross-sectional comparisons. The goals of the described protocol are to focus on the equipment and its installation, and to objectively and straightforwardly describe the assessment procedures for evaluating spatiotemporal gait parameters in elderly and patient populations.
The protocol follows the guidelines of the local human Ethics Committee in Zurich (KEK Zurich).
1. Hardware Installation (Figure 1)
Figure 1. The photoelectric system consists of light-transmitting (T) and light-receiving (R) units that are placed parallel to each other with a distance of approximately 1 m. The camera is installed close to the start area for control purposes. The laptop is connected with USB cables to the first R bar and to the camera. Please click here to view a larger version of this figure.
2. Software Installation and Preparation of a Test
Figure 2. Standard settings for a gait test with 10 bars, as described in the present protocol. These settings have to be defined when the photoelectric system is used for the first time. In this protocol the starting foot is not defined. The system starts measuring when the patient enters the recording area and stops measuring when the patient leaves the measuring units. Please click here to view a larger version of this figure.
3. Testing Procedures
4. Data Analysis
Figure 3. Screenshot of all test data. The command buttons appear on the left side of the window (e.g., by clicking on Print a report is generated, which can be eventually modified). The other part of the window presents the following information regarding the current test, from top to bottom: video, charts displaying the results, table with numerical data, and photoelectric bars. These details can be shown/hidden using the Configure button on the right side. The actual view of the data can be changed by clicking on Gait data or Gait report, respectively. Please click here to view a larger version of this figure.
A recent study demonstrated the validity of the photoelectric system against a criterion instrument (a validated electronic walkway) for the assessment of spatiotemporal gait parameters in orthopedic patients and healthy elderly controls7. The same between-group differences in gait variables were detected by the two systems. Although concurrent validity was excellent, with intraclass correlation coefficients ranging between 0.933 and 0.999 (p < 0.001), a systematic bias (p < 0.001) was observed between the two measuring instruments. Stance time and cycle time were significantly longer while swing time and step length were shorter for the photoelectric system than for the electronic walkway. In the same way, walking speed and cadence were slightly (1-2%) but significantly lower for the photoelectric system.
Data from a representative report are presented in Figure 4. The report shows the results of a walking trial conducted at normal velocity with 12 steps (6 left and 6 right). Spatiotemporal gait parameters of this trial are presented as mean ± SD and CV for the left and right side. Furthermore the percent difference between the left and right side (Diff.) is presented. Data of the left and right side are presented in purple and turquoise, respectively. The most common gait parameters such as step length, stance phase, swing phase, single support, step time, cadence, and speed are instantaneously (on-line) calculated and presented on the screen during the actual trials (Figure 3). The same values are presented in the off-line gait report (Figure 4). Percent difference between the two sides expresses the so-called side-to-side (or bilateral) asymmetry that is a good indicator of gait recovery, e.g., before and after an intervention. Recovery of symmetrical gait function is one of the primary goals in patients rehabilitation so to regain independence in daily activities. CV is used as an indicator of gait variability, which is generally increased in patients with clinically-relevant syndromes such as falling and neuro-degenerative diseases16,17 and therefore it is a relevant outcome measure for neurological patients and for subjects with mild cognitive impairments and dementia.
Figure 4. Representative gait report of a walking trail conducted at the normal velocity by an orthopedic patient. The figure on the top presents a simplified gait cycle with the different temporal gait parameters (per foot). The table presents averaged test data of consecutive steps for the selected test. For the different spatiotemporal gait parameters the following results are presented: mean ± standard deviation (SD) for left and right side, coefficient of variation (CV) for left and right side, and percent difference (Diff.) between the left and right side. Please click here to view a larger version of this figure.
The protocol presented here can be used to evaluate spatial and temporal gait parameters of patients (orthopedic, neurological, cardiorespiratory, etc.) and healthy older adults with a recently-introduced photoelectric system. The total length and width of the system can be modulated depending on the available space and budget. The estimated cost (in Europe) is approximately 2,800 USD per meter for a 10-meter system and the minimum recommended length is 3 meter for floor-based gait analysis. A new feature of the photoelectric system has also been recently introduced, which consists in closing the corridor with two additional bars that are positioned perpendicularly to T and R bars, thereby creating a sort of grid that allows calculation of 2D footfall patterns. Additionally, only the two first-meter bars can be used for treadmill-based gait analysis, even though this would require a validation.
Before starting the measurements it is important to verify that all the bars are properly connected; this is facilitated by the red/green control LEDs disposed on each photoelectric bar. Another critical step is the definition of the starting foot, which has to be selected at the beginning of each test. In case the wrong side is selected, offline modifications can be made at any time (open the appropriate test and select Gait report, then change the foot), also after having verified the starting foot (and any other eventual doubt) on the video.
The main limitation of this protocol is the use of self-selected gait velocities (normal and faster than normal), because all the spatiotemporal gait parameters are considerable affected by the walking velocity18. An alternative option would be to impose a fixed gait speed to all subjects by means of a metronome (e.g., at 4 km/h). The validity of this approach is nevertheless uncertain as not all the patients can walk at a given velocity and/or maintain a fixed gait speed. An important limitation of the photoelectric system is the height of diodes with respect to the floor (3 mm). This instrument slightly overestimates stance time and underestimates swing time compared to floor-integrated instruments (e.g., electronic walkways or force plates) because the diodes detect rearfoot loading and forefoot unloading 3 mm above floor level (see Figure 3A in reference 7)7. Due to this limitation the system can only provide valid data for subjects who are able to raise sufficiently their feet during walking and who have a step length longer than their foot length7. This could represent a problem for the evaluation of gait variables in some seriously-impaired neurological patients.
Since this photoelectric system is very simple to operate and valid data can be quickly collected and easily organized into a comprehensive report, this is a potentially useful system for clinical assessment of spatiotemporal gait variables in patients and older adults. Clinicians could, in fact, implement these assessments in routine physical examinations with the objectives to detect gait disorders and/or to monitor patient progress following an intervention.
The authors have nothing to disclose.
Name of Equipment | Company | Catalog Number | Comments/Description |
-Optogait system (10 meters) | Microgate, Bolzano, Italy | www.optogait.com | |
-Optogait software | www.optogait.com/Support/Downloads | ||
-Laptop | |||
The Optogait system contains the following equipment: | |||
-10 light-transmitting (T) bars (1 as a first meter) | |||
-10 light-receiving (R) bars (1 as a first meter) | |||
-18 caps to connect the bars within a set (9 for T and 9 for R bars) and 2 special caps for the last T and R bar | |||
-1 camera with its tripod | |||
-1 cable for connecting the Optogait to the laptop | |||
-1 cable for connecting the camera to the laptop | |||
-2 power supplies (one for each set of bars) |