Effects of lighting illuminance levels on stair negotiation performance in individuals with visual impairment.

BACKGROUND: Stair-related falls of older people cause a substantial financial and social burden. Deterioration of the visual system amongst other factors put older people at a high risk of falling. Improved lighting is often recommended. The aim of this study was to investigate the effect of lighting illuminance on stair negotiation performance in older individuals with visual impairment. METHODS: Eleven participants aged 60 or over with a vision of 6/18 or worse ascended and descended a staircase under: 50 lx, 100 lx, 200 lx, 300 lx and distributed 200 lx lighting. A motion capture system was used to measure movements of the lower limb. Clearance, clearance variability, temporal and spatial parameters and joint/segment kinematics were computed. FINDINGS: There was no effect on clearance or clearance variability. Participants had lower speed, cadence, increased cycle time and stance time in the 50 lx compared to 300 lx and distributed 200 lx lighting in descent. The minimum hip angle in ascent was increased in the 200 lx lighting. Clearance was found to be moderately correlated with balance scores. INTERPRETATION: Individuals with visual impairment adopt precautionary gait in dim lighting conditions. This does not always result in improvements in the parameters associated with risk of falling (e.g. clearance).

Gait event detection during stair walking using a rate gyroscope.

Gyroscopes have been proposed as sensors for ambulatory gait analysis and functional electrical stimulation systems. These applications often require detection of the initial contact (IC) of the foot with the floor and/or final contact or foot off (FO) from the floor during outdoor walking. Previous investigations have reported the use of a single gyroscope placed on the shank for detection of IC and FO on level ground and incline walking. This paper describes the evaluation of a gyroscope placed on the shank for determination of IC and FO in subjects ascending and descending a set of stairs. Performance was compared with a reference pressure measurement system. The absolute mean difference between the gyroscope and the reference was less than 45 ms for IC and better than 135 ms for FO for both activities. Detection success was over 93%. These results provide preliminary evidence supporting the use of a gyroscope for gait event detection when walking up and down stairs.

Kinematic analysis in oculoplastic reconstructive surgery: measuring manual control and fluidity of movement.

OBJECTIVE: To evaluate higher-order kinematic analysis, a technique not previously applied to surgical skills assessment, as a tool for elucidating patterns of movement. METHODS: An observational cohort study of 27 subjects, divided into 3 equal groups based on surgical experience consisting of novice (performed <5 prior procedures), intermediate (performed 5-100 prior procedures), and expert (performed >100 prior procedures) subjects. The subjects placed a deep 3-1-1 suture onto a shielded hook on a standardized surgical skills practice board. Detailed 3-dimensional motion data were obtained using a motion capture system. Two novel parameters were used to analyze movement patterns: the frequency distribution (cumulative histogram), describing the distribution of movement sizes used, and the probability density function (normalization of frequency distribution data), evaluating the distribution of motion against the magnitude of movement. The α risk for statistical significance was set at .05. RESULTS: We found significant differences among the 3 groups for frequency distribution (P = .02; Kruskal-Wallis test) and probability density function (P = .03). CONCLUSIONS: These 2 indices, derived from kinematic analysis, appear to distinguish between groups of test subjects with known differences in surgical experience. The evaluation of higher-order motion patterns appears to be of value in the objective evaluation of surgical skills. This method for assessment of manual skills is likely to provide a better guide as to which patterns of movement have the greatest efficiency for specific tasks.

Gait event detection on level ground and incline walking using a rate gyroscope.

Gyroscopes have been proposed as sensors for ambulatory gait analysis and functional electrical stimulation systems. Accurate determination of the Initial Contact of the foot with the floor (IC) and the final contact or Foot Off (FO) on different terrains is important. This paper describes the evaluation of a gyroscope placed on the shank for determination of IC and FO in subjects walking outdoors on level ground, and up and down an incline. Performance was compared with a reference pressure measurement system. The mean difference between the gyroscope and the reference was less than -25 ms for IC and less than 75 ms for FO for all terrains. Detection success was over 98%. These results provide preliminary evidence supporting the use of the gyroscope for gait event detection on inclines as well as level walking.

Kinematic analysis of surgical dexterity in intraocular surgery.

OBJECTIVE: To evaluate the potential of motion analysis as a discriminator of surgical skill during intraocular surgery. METHODS: Twenty-four subjects were divided into 3 groups (n = 8 each) based on the number of completed phacoemulsification procedures: novice (n < 10), intermediate (n = 10-150), and expert (n > 150). The Qualisys motion-capture system obtained data from the surgeons performing (1) corneal wound construction (incision), (2) continuous curvilinear capsulorrhexis (CCC), and (3) phacoemulsification lens extraction on artificial eyes. The main outcome measures were time, overall path length, and total number of movements. Statistical significance was set at P < .05. RESULTS: For the incision task, significant differences between the levels of experience were found for time (P = .001), number of movements (P = .001), and path length (P = .05). For the CCC task, significant differences were found between groups for time (P = .03) and number of movements (P = .03), but not for path length (P = .08). For the phacoemulsification task, significant differences were found between the 3 groups for time (P = .04), path length (P = .02), and number of movements (P = .04). CONCLUSIONS: Motion analysis differentiated between surgeons with varying levels of experience performing phacoemulsification tasks, thus demonstrating construct validity. This technique may be useful in the objective quantitative measurement of microsurgical skill with potential applications for training and research.

A six degrees-of-freedom marker set for gait analysis: repeatability and comparison with a modified Helen Hayes set.

Kinematic gait analysis is limited by simplified marker sets and related models. The majority of sets in clinical use were developed with low resolution imaging systems so required various assumptions about body behaviour. Further major limitations include soft tissue artefact and ambiguity in landmark identification. An alternative is the use of sets based on six degrees-of-freedom (DOF) principles, primarily using marker clusters for tracking. This study evaluates performance of a 6DOF set, based largely on CAST/ISB recommendations, through comparison with a conventional set and assessment of repeatability. Ten healthy subjects were assessed in treadmill walking, with both sets applied simultaneously on two occasions. Data were analysed using repeatability coefficients, correlation of key features, and comparison of joint angle curves and difference curves with confidence bands. Apart from pelvic tilt all segment and joint angles from both sets showed high within and between session repeatability (CMC>0.80). Hip rotations showed clear differences between the two sets with indications in support of the 6DOF set. Knee coronal angles showed evidence of cross-talk in the conventional set, highlighting difficulties with anatomical identification despite control measures such as a foot alignment template. Knee transverse angles showed inconsistent patterns for both sets. At the ankle the conventional set only allowed true measurement in two planes so with high repeatability the 6DOF set is preferable. The 6DOF set showed comparable performance to the conventional set and overcomes a number of theoretical limitations, however further development is needed prior to clinical implementation.

Detection of gait events using an F-Scan in-shoe pressure measurement system.

A portable system capable of accurate detection of initial contact (IC) and foot off (FO) without adding encumbrance to the subject would be extremely useful in many gait analysis applications. Force platforms represent the gold standard method for determining these events and other methods including foot switches and kinematic data have also been proposed. These approaches, however, present limitations in terms of the number of steps that can be analysed per trial, the portability for outdoor measurements or the information needed beforehand. The purpose of this study was to evaluate the F-Scan((R)) Mobile pressure measurement system when detecting IC and FO. Two methods were used, one was the force detection (FD) in-built algorithm used by F-Scan software and a new area detection (AD) method using the loaded area during the gait cycle. Both methods were tested in ten healthy adults and compared with the detection provided by a kinetic detection (KT) algorithm. The absolute mean differences between KT and FD were (mean+/-standard deviation) 42+/-11 ms for IC and 37+/-11 ms for FO. The absolute mean differences between KT and AD were 22+/-9 ms for IC and 10+/-4 ms for FO. The AD method remained closer to KT detection for all subjects providing sufficiently accurate detection of both events and presenting advantages in terms of portability, number of steps analysed per trial and practicality as to make it a system of choice for gait event detection.

Motion analysis as a tool for the evaluation of oculoplastic surgical skill: evaluation of oculoplastic surgical skill.

OBJECTIVE: To evaluate motion analysis as a discriminator of ophthalmic plastic surgical skill between surgeons of varying experience. METHODS: Thirty subjects were divided into 3 groups based on surgical experience: novice (< 5 performed procedures; n = 10), intermediate (5-100 procedures; n = 10), and expert (> 100 procedures; n = 10). Detailed 3-dimensional motion data from surgeons performing 2 oculoplastic surgical tasks on a wet laboratory skills board were obtained using the Qualisys motion capture system. The first task was a deep 3-1-1 suture. The second was skin closure with a continuous suture. The main outcome measures were time, overall path length, and total number of movements. Kruskal-Wallis analysis was performed to evaluate statistical significance. RESULTS: Highly significant differences were found during the skin closure task between all groups for mean time (P = .002), overall path length (P = .002), and number of movements (P = .001). For the deep stitch, highly significant differences were also found for time (P < .001), path length (P < .001), and number of movements (P < .001). CONCLUSIONS: Motion analysis, using this technology, was able to differentiate between surgeons of varying experience performing oculoplastic tasks, thus demonstrating construct validity. This technique may be useful in the objective quantitative measurement of oculoplastic skill, with potential applications for training and research.

Assessment and validation of a simple automated method for the detection of gait events and intervals.

A simple and rapid automatic method for detection of gait events at the foot could speed up and possibly increase the repeatability of gait analysis and evaluations of treatments for pathological gaits. The aim of this study was to compare and validate a kinematic-based algorithm used in the detection of four gait events, heel contact, heel rise, toe contact and toe off. Force platform data is often used to obtain start and end of contact phases, but not usually heel rise and toe contact events. For this purpose synchronised kinematic, kinetic and video data were captured from 12 healthy adult subjects walking both barefoot and shod at slow and normal self-selected speeds. The data were used to determine the gait events using three methods: force, visual inspection and algorithm methods. Ninety percent of all timings given by the algorithm were within one frame (16.7 ms) when compared to visual inspection. There were no statistically significant differences between the visual and algorithm timings. For both heel and toe contact the differences between the three methods were within 1.5 frames, whereas for heel rise and toe off the differences between the force on one side and the visual and algorithm on the other were higher and more varied (up to 175 ms). In addition, the algorithm method provided the duration of three intervals, heel contact to toe contact, toe contact to heel rise and heel rise to toe off, which are not readily available from force platform data. The ability to automatically and reliably detect the timings of these four gait events and three intervals using kinematic data alone is an asset to clinical gait analysis.