Measurement of human posture and movement is an important area of research in the bioengineering and rehabilitation fields. Various attempts have been initiated for different clinical application goals, such as diagnosis of pathological posture and movements, assessment of pre- and post-treatment efficacy and comparison of different treatment protocols. Image-based methods for measurements of human posture and movements have been developed, such as the photogrammetry, optoelectric technique and video analysis. However, it is found that these methods are complicated to set up, time-consuming to operate and could only be applied in laboratory environments. Electronic sensors and systems with advanced technology, namely accelerometer, gyroscope, flexible angular sensor, electromagnetic tracking system and sensing fabrics, have been developed and applied to solve the relevant application problems of the image-based methods. Nonetheless, other problems for using these electronic sensors emerged, including the environment influence and signal extraction difficulties. Further development of these electronic sensors and measurement methods could enhance their clinical applications in institutional as well as community levels. This article reviews the possible applications of these electronic sensors and systems, and precautions of their applications in analysis of human posture and movement. Such information would help researchers and clinicians in selecting and developing the most appropriate measurement techniques of using the electronic sensors for clinical applications of human posture and movement analysis.

http://poi.sagepub.com/content/31/1/62.full.pdf+html

Clinical applications of sensors for human posture and movement analysis: a review.

Study design A 10-year follow-up evaluation of the effectiveness of school screening for scoliosis performed in a closed island population Objectives To evaluate the diagnostic accuracy of methods used for screening scoliosis and to re-examine the long-term effectiveness of the school scoliosis screening program Summary of background data The diagnostic accuracy of the forward-bending test and the long-term efficacy of the screening programs have not been clearly established Methods In 1987, 2700 pupils aged 8 to 16 years from the island of Samos were screened for scoliosis The Adams forward-bending test, Moire topography, the scoliometer, and the humpometer were used Radiologic evaluation of the spine was available for each pupil and the number of false-negative and false-positive results of the screening methods was calculated Subsequently, sensitivity, specificity, and positive and negative predictive values were estimated for each screening technique Pupils found positive for spinal deformity were then followed up regularly at yearly intervals In 1997, all positive subjects attended a 10-year clinical and radiologic follow-up, and the remaining subjects were re-evaluated by a postal questionnaire and were clinically examined if necessary Results Spinal deformity was found in 153 (566%) pupils Scoliosis (defined as a spinal curvature > or = 10 degrees) was found in 32 pupils, for a prevalence of 118% For scoliosis, the Adams forward-bending test showed a number of false-negative results (in five cases), for a sensitivity of 8437% and specificity of 9344% The sensitivities of Moire topography, the humpometer, and the scoliometer were 100%, 9375%, and 9062%, respectively, and specificity was 8538%, 7811%, and 7976% respectively The negative predictive value of the forward-bending test was inferior to those of the other methods During this scoliosis screening program, if cutoff limits for referral had been used, such as the asymmetry of two Moire fringes, a humpogram deformity of (D + H) = 10 mm, and 8 degrees of scoliometer angle, it would have been possible to reduce radiologic examination by 894% Three (011%) pupils aged between 12 and 14 years with scoliotic deformities greater than 20 degrees underwent satisfactory nonoperative treatment with Boston braces One pupil with a 40 degrees thoracic curvature, underwent satisfactory surgical treatment because of progression 1 year later Of the 121 spinal deformities with an initial Cobb angle less than 10 degrees, 44 (358%), and of the 29 scoliotic deformities with an initial Cobb angle between 10 degrees and 20 degrees, 14 (483%) progressed (a Cobb angle difference of at least 5 degrees in more than one examination) Observation and physiotherapy were the only treatments applied to all except one of the pupils in these groups Conclusions The Adams forward-bending test cannot be considered a safe diagnostic criterion for the early detection of scoliosis (especially when it is used as the only screening tool) because it results in an unacceptable number of false-negative findings For the early detection of scoliosis, a combination of back-shape analysis methods can be safely used with the introduction of cutoff limits for referral being a useful procedure The incidence of significant scoliosis is low, and its natural history seems to be independent of early detection The wide-spread use of school scoliosis screening with the use of the forward-bending test must be questioned

Ten-year follow-up evaluation of a school screening program for scoliosis. Is the forward-bending test an accurate diagnostic criterion for the screening of scoliosis?

This study aimed to estimate the reliability of 3-D trunk surface measurements for the characterization of external asymmetry associated with scoliosis. Repeated trunk surface acquisitions using the Inspeck system (Inspeck Inc., Montreal, Canada), with two different postures A (anatomical position) and B (‘‘clavicle’’ position), were obtained from patients attending a scoliosis clinic. For each acquisition, a 3-D model of the patient’s trunk was built and a series of measurements was computed. For each measure and posture, intraclass correlation coefficients (ICC) were obtained using a bivariate analysis of variance, and the smallest detectable difference was calculated. For posture A, reliability was fair to excellent with ICC from 0.91 to 0.99 (0.85 to 0.99 for the lower bound of the 95% confidence interval). For posture B, the ICC was 0.85 to 0.98 (0.74 to 0.99 for the lower bound of the 95% confidence interval). The smallest statistically significant differences for the maximal back surface rotation was 2.5 and 1.5° for the maximal trunk rotation. Apparent global asymmetry and axial trunk rotation indices were relatively robust to changes in arm posture, both in terms of mean values and within-subject variations, and also showed a good reliability. Computing measurements from cross-sectional analysis enabled a reduction in errors compared to the measurements based on markers’ position. Although not yet sensitive enough to detect small changes for monitoring of curve natural progression, trunk surface analysis can help to document the external asymmetry associated with different types of spinal curves as well as the cosmetic improvement obtained after surgical interventions. The anatomical posture is slightly more reliable as it allows a better coverage of the trunk surface by the digitizing system.

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Reliability of trunk shape measurements based on 3-D surface reconstructions

The lack of reliable techniques to follow up scoliotic deformity from the external asymmetry of the trunk leads to a general use of X-rays and indices of spinal deformity. Young adolescents with idiopathic scoliosis need intensive follow-ups for many years and, consequently, they are repeatedly exposed to ionising radiation, which is hazardous to their long-term health. Furthermore, treatments attempt to improve both spinal and surface deformities, but internal indices do not describe the external asymmetry. The purpose of this study was to assess a commercial, optical 3D digitising system for the 3D reconstruction of the entire trunk for clinical assessment of external asymmetry. The resulting surface is a textured, high-density polygonal mesh. The accuracy assessment was based on repeated reconstructions of a manikin with markers fixed on it. The average normal distance between the reconstructed surfaces and the reference data (markers measured with CMM) was 1.1±0.9 mm.

Accuracy assessment of human trunk surface 3D reconstructions from an optical digitising system

Background: Numerous studies have attempted to quantify the correlation between the surface deformity and the Cobb angle without considering growth as an important factor that may influence this correlation. In our series, we noticed that in some younger referred children from the school-screening program there is a discrepancy between the thoracic scoliometer readings and the morphology of their spine. Namely there is a rib hump but no spinal curve and consequently no Cobb angle reading in radiographs, discrepancy which fades away in older children. Based on this observation, we hypothesized that in scoliotics the correlation between the rib cage deformity and this of the spine is weak in younger children and vice versa. Methods: Eighty three girls referred on the basis of their hump reading on the scoliometer, with a mean age of 13.4 years old (range 7–18), were included in the study. The spinal deformity was assessed by measuring the thoracic Cobb angle from the postero-anterior spinal radiographs. The rib cage deformity was quantified by measuring the rib-index at the apex of the thoracic curve from the lateral spinal radiographs. The rib-index is defined as the ratio between the distance of the posterior margin of the vertebral body and the most extended point of the most projecting rib contour, divided by the distance between the posterior margin of the same vertebral body and the most protruding point of the least projecting rib contour. Statistical analysis included linear regression models with and without the effect of the variable age. We divided our sample in two subgroups, namely the younger (7–13 years old) and the older (14–18 years old) than the mean age participants. A univariate linear regression analysis was performed for each age group in order to assess the effect of age on Cobb angle and rib index correlation. Results: Twenty five per cent of patients with an ATI more than or equal 7 degrees had a spinal curve under 10 degrees or had a straight spine. Linear regressions between the dependent variable "Thoracic Cobb angle" with the independent variable "rib-index" without the effect of the variable "age" is not statistical significant. After sample split, the linear relationship is statistically significant in the age group 14–18 years old (p < 0.03). Conclusion: Growth has a significant effect in the correlation between the thoracic and the spinal deformity in girls with idiopathic scoliosis. Therefore it should be taken into consideration when trying to assess the spinal deformity from surface measurements. The findings of the present study implicate the role of the thorax, as it shows that the rib cage deformity precedes the spinal deformity in the pathogenesis of idiopathic scoliosis.

/pdf/the-effect-of-growth-on-the-correlation-between-the-spinal-3g5aruhp2r.pdf

The effect of growth on the correlation between the spinal and rib cage deformity: implications on idiopathic scoliosis pathogenesis

In this study, truncal deformity in patients with scoliosis was evaluated by circumferential scanning using an optoelectronic device (Optronic Torsograph, Anima Corp., Tokyo, Japan). This device generates cross-sectional skin surface topography at 10 axial levels to provide a three-dimensional representation of truncal shape. Ninety-three patients with suspected idiopathic scoliosis were evaluated with conventional Cobb measurements, and their parameters were computed using the device's measurements. The geometric cross-sectional indexes correlated poorly with the Cobb angle and were highly variable during repeated measurements. The optoelectronic device's angle, a measure of centroid curvature, correlated highly with the Cobb angle for primary spinal curves. The highest correlation was observed in thoracolumbar curves. This optoelectronic device has clinical relevance as a method for further scoliosis screening and monitoring the progression of spinal curvature in a patient.

C. Burt

Papers

Optoelectronic evaluation of trunk deformity in scoliosis.