R. Allen

Hand and arm injuries associated with repetitive manual work in industry: a review of disorders, risk factors and preventive measures

Musculoskeletal disorders are the most common self-reported, work-related illness in the UK, with upper limb disorders ranking second only to back complaints. The rapid increase in disablement cases, the reduced productivity resulting from the disorders, and, perhaps, the threat of litigation which is on the increase, has led to an increased awareness of the problems and an increasing desire to reduce the incidence of such disorders. This paper reviews the problem of upper limb disorders and focuses on those disorders that could be associated with repetitive manual work in industry. The disorders are described and categorized, and potential occupational risk factors are discussed and related to the injuries. In addition, a number of preventive measures, in the form of ergonomics design changes and changes in workplace practice are reviewed. There are frequent calls for well-designed epidemiological studies, so that meaningful dose-response relationships can be drawn up. A significant part of good study design is associated with measurement and analysis of the user-tool interface and the working environment. With this in mind, a variety of measurement techniques are described. Furthermore, this paper highlights the need for study designs to be founded on a better understanding of the potential damage mechanisms, and points the way towards which areas should be investigated.

Automated segmentation of lumbar vertebrae in digital videofluoroscopic images

Low back pain is a significant problem in the industrialized world. Diagnosis of the underlying causes can be extremely difficult. Since mechanical factors often play an important role, it can be helpful to study the motion of the spine. Digital videofluoroscopy has been developed for this study and it can provide image sequences with many frames, but which often suffer due to noise, exacerbated by the very low radiation dosage. Thus, determining vertebra position within the image sequence presents a considerable challenge. There have been many studies on vertebral image extraction, but problems of repeatability, occlusion and out-of-plane motion persist. In this paper, we show how the Hough transform (HT) can be used to solve these problems. Here, Fourier descriptors were used to describe the vertebral body shape. This description was incorporated within our HT algorithm from which we can obtain affine transform parameters, i.e., scale, rotation and center position. The method has been applied to images of a calibration model and to images from two sequences of moving human lumbar spines. The results show promise and potential for object extraction from poor quality images and that models of spinal movement can indeed be derived for clinical application.

Automatic location of vertebrae in digitized videofluoroscopic images of the lumbar spine

Back pain is a widespread problem, and the disability it engenders continues to grow, despite efforts to contain it. A major problem in the diagnosis and management of back pain is the assessment of the degree to which mechanical factors play a part. Of considerable importance in understanding these mechanical factors is being able to quantify how the human spine actually moves in vivo. Digitized videofluoroscopy is currently the only practical method available for studying spinal motion in vivo at the segmental level. Low-dose, planar motion X-rays of the spine are captured on videotape and subsequently digitized for analysis. Until now, vertebrae in the digitized images were identified and marked manually as a basis for calculating intervertebral kinematics. This paper describes a procedure for automatically identifying the vertebrae in the motion sequences. The process increases objectivity and repeatability, and significantly reduces the manual effort required in locating the vertebrae prior to calculating the kinematics. The technique has been applied to images of a calibrated model and the results are promising. In-plane rotations may be calculated to an accuracy of at least 1 degree. Repeated analysis reveals standard deviations of less than 0.5 degree for intervertebral rotations and less than 0.25 mm for translations.

A digital videofluoroscopic technique for spine kinematics

The kinematic behaviour of the vertebral segments under the influence of spinal injury and other mechanical problems is difficult to quantify in patients. This paper describes the use of a calibration model and human subjects to investigate the accuracy of a method for determining lumbar intervertebral rotations using images digitized from an image intensifier. The main influences were found to be observer error in marking co-ordinates, scaling of the image presented by the computers monitor, distortion caused by out-of-plane images and loss of image quality as a result of scattered radiation from the soft tissues. The technique may be valuable in the light of its efficiency and low X-ray exposure to patients.

Automatic recognition of vertebral landmarks in fluoroscopic sequences for analysis of intervertebral kinematics

Intervertebral kinematics closely relates to the functionality of the spinal segments. Direct measurement of the intervertebral kinematics in vivo is very problematic. The use of a fluoroscopic device can provide continuous screening of the lumbar tract during patient spontaneous motion, with an acceptable, low X-ray dose. The kinematic analysis is intended to be limited to planar motion. Kinematic parameters are computed from vertebral landmarks on each frame of the image sequence. Landmarks are normally selected manually in spite of the fact that this is subjective, tedious to perform and regarded as one of the major contributors to errors in the computed kinematic parameters. The aim of this work is to present an innovative method for the automatic recognition of vertebral landmarks throughout a fluoroscopic image sequence to provide an objective and more precise quantification of intervertebral kinematics. The recognition procedure is based upon comparing vertebral features in two adjacent frames by means of a cross-correlation index, which is also robust despite the low signal-to-noise ratio of the lumbar fluoroscopic images. To provide a quantitative assessment of this method a calibration model was used which consisted of two lumbar vertebrae linked by a universal joint. The reliability and accuracy of the kinematic measurements have been investigated. The errors are of the order of a millimetre for the localisation of the intervertebral centre of rotation and tenths of a degree for the intervertebral angle. Error analysis suggests that this method improves the accuracy of the intervertebral kinematic calculations and has the potential to automate the selection of anatomical landmarks.

Effect of gait cycle selection on EMG analysis during walking in adults and children with gait pathology.

This paper presents the results of a project to evaluate different methods of gait cycle selection on the analysis of electromyography recorded during gait. Electromyography (EMG) describes the electrical activity associated with the muscle and is often interpreted in gait analysis using a simultaneously obtained signal to identify phases of the gait cycle. Phase transitions are often selected manually from reference signals derived from additional instrumentation, such as pressure platforms, footswitches and video cameras. We propose two methods (automatic and semi-automatic) as an alternative to the more traditional manual selection, and analyse how the gait cycle selection affects the EMG analysis. To quantify the differences between the gait cycles obtained using each method and to classify each cycle, three indices have been introduced. The effect of the gait cycle selection has been evaluated with respect to the EMG step profiles and temporal gait descriptors. An asymptomatic adult, an asymptomatic child and two children with cerebral palsy were examined using telemetric EMG devices and pressure footswitches. The results obtained showed that the method of gait cycle selection did not have a major influence for the adult, but it altered considerably the analysis in the case of the children with cerebral palsy.

Estimation of out-of-plane vertebra rotations on radiographic projections using CT data: A simulation study

This study extends previous research concerning in vivo intervertebral motion by means of single-plane fluoroscopy in an attempt to overcome 2D analysis limitations. Knowledge of out-of-plane vertebra rotations will extend the results provided by planar kinematic studies, which is particularly important for lateral bending investigation where axial rotation accompanies side bending, but is also valuable in sagittal analysis (e.g. indicating an absence of coupled axial rotation). Combining a fluoroscopic projection of a vertebra with volumetric information provided by CT data, vertebra 3D position can be estimated. Out-of-plane vertebral rotations are estimated by comparing Digitally Reconstructed Radiographs (DRRs) in different orientations with a reference fluoroscopic projection, maximising the image cross-correlation index. DRRs have been computed from CT-data using a ray-casting algorithm. In this work a feasibility study of the method was performed by means of a computer simulation. To this end the CT volume (vertebra L4, segmented) provided by the Visible Human Project was utilised and reference fluoroscopic projections were simulated in different orientations adding various levels of noise. Accuracy and precision of the proposed method was determined. Error analysis reveals that an accuracy of less than 1 degree can be achieved in computation of out-of-plane vertebral angles.

Dynamic cerebral autoregulation assessment using an ARX model: comparative study using step response and phase shift analysis

Middle cerebral arterial blood velocity (MCAv) response to spontaneous and manipulated changes of arterial blood pressure (ABP) was studied in eight subjects using a linear autoregressive with exogenous input (ARX) model. ABP and MCAv were measured non-invasively by photoplethysmograph and transcranial Doppler ultrasound, respectively. Data were recorded at rest (spontaneous changes in ABP) and during thigh cuff (step-wise changes) and lower body negative pressure (sinusoidal changes of 1/12 Hz) tests in both normocapnia and hypercapnia (5% CO2). Since autoregulation is modulated by CO2, respiratory CO2 was simultaneously monitored to allow comparison of cerebral autoregulation status with different CO2 levels. ABP and MCAv were fitted by ARX models and dynamic cerebral autoregulation was estimated by analysing both the step responses and phase shift at the 1/12 Hz of the corresponding ARX models. The ARX model consistently modelled the phase lead of MCAv to ABP and it showed that the phase shift at 1/12 Hz of ARX model is consistent with the real phase shift of the data (p=0.59). Strong linear relationships between pCO2 and gradient of the step response (r=-0.58, p<0.0001) and between pCO2 and phase shift (r=-0.76, p<0.0001) were observed, which suggests that cerebral autoregulation can be assessed by step response or phase shift analysis of the ARX model fitted to ABP and MCAv data with spontaneous changes.

Lumbar spine visualisation based on kinematic analysis from videofluoroscopic imaging

Low back pain is a significant problem and its cost is enormous to society. However, diagnosis of the underlying causes remains problematic despite extensive study. Reasons for this arise from the deep-rooted situation of the spine and also from its structural complexity. Clinicians have to mentally convert 2-D image information into a 3-D form to gain a better understanding of structural integrity. Therefore, visualisation and animation may be helpful for understanding, diagnosis and for guiding therapy. Some low back pain originates from mechanical disorders, and study of the spine kinematics may provide an insight into the source of the problem. Digital videofluoroscopy was used in this study to provide 2-D image sequences of the spine in motion, but the images often suffer due to noise, exacerbated by the very low radiation dosage. Thus determining vertebrae position within the image sequence presents a considerable challenge. This paper describes a combination of spine kinematic measurements with a solid model of the human lumbar spine for visualisation of spine motion. Since determination of the spine kinematics provides the foundation and vertebral extraction is at the core, this is discussed in detail. Edge detection is a key feature of segmentation and it is shown that phase congruency performs better than most established methods with the rather low-grade image sequences from fluoroscopy. The Hough transform is then applied to determine the positions of vertebrae in each frame of a motion sequence. In the Hough transform, Fourier descriptors are used to represent the vertebral shapes. The results show that the Hough transform is a very promising technique for vertebral extraction from videofluoroscopic images. A dynamic visualisation package has been developed in order to view the moving lumbar spine from any angle and viewpoint. Wire frame models of the vertebrae were built by using CT images from the Visible Human Project and these models are scaled to match the fluoroscopic image data. For animation, the spinal kinematic data from the motion study is incorporated.

An image processing method for spine kinematics—preliminary studies

The measurement of spinal segmental movement is essential to the understanding of the pathomechanics of spinal injuries and other mechanical disorders both in research and clinical medicine. Unfortunately, this is difficult to do accurately without the use of invasive and laborious procedures. The image processing method described in this paper provides a possible avenue for overcoming these limitations by using rapid computerized analysis of low-dose motion radiographs. X-ray images of lumbar vertebrae from an image intensifier were digitized using an image processing system. These images were derived both from a calibration model and human subjects and were used to estimate the accuracy and reproducibility of segmental angular position and rotation measurements obtained by image processing. The results of both inter- and intraobserver studies were encouraging. Further research is necessary to develop the system for measuring these and other kinematic parameters in vivo and to assess the possibility of adding a measure of automation to the system.