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Study Design: Prospective fluoroscopic and electromyographic study of coronal plane lumbar spine motion in healthy male volunteers. Objectives: Assess the intervertebral motion profiles in healthy volunteers for symmetry, regularity, and neutral zone laxity during passive recumbent lateral bending motion. Summary Of Background Data: Previous continuous in vivo motion studies of the lumbar spine have mainly been limited to active, weight-bearing, flexion-extension (sagittal plane) motion. No data are available for passive lateral bending or to indicate the motion profiles when muscle activity is minimized. Methods: Thirty asymptomatic male volunteers underwent video-fluoroscopy of their lumbar spines during passive, recumbent lumbar lateral bending through 80 degrees using a motor-driven motion table. Approximately 120 consecutive images of segments L2-L5 were captured, and the position of each vertebra was tracked throughout the sequence using automated frame-to-frame registration. Reference intervals for intervertebral motion parameters were calculated. Surface electromyography recordings of erector spinae were obtained in a similar group of volunteers using the same protocol without fluoroscopy to determine to what extent the motion was completely passive. Results: Correlations between intervertebral and lumbar motion were always positive in controls and asymmetry was less than 55% of intervertebral range. The upper reference interval for the slope of intervertebral rotation in the first 10 degrees of trunk motion did not exceed 0.46 for any level. Muscle electrical activity during the motion was very low. Examples from patient studies showed markedly different results. Conclusion: These results suggest that reference limits from asymptomatic data for coronal plane passive recumbent intervertebral motion may be a useful resource for investigating the relationship between symptoms of chronic (nonspecific) low back pain and biomechanics and in the clinical assessment of patients and interventions that target the passive holding elements of the spine. Data pooling from multiple studies would be necessary to establish a complete database. [ABSTRACT FROM AUTHOR]

This paper is concerned with imaging techniques for mapping and locating underground pipeline leakage. Ground surface vibrations induced by the propagating axisymmetric wave can be measured by an array of acoustic/vibration sensors, with the extraction of magnitude information used to determine the position of leak source. A method of connected graph traversal is incorporated into the vibroacoustic technique to obtain the spatial image with better accuracy compared to the conventional magnitude contour plot. Measurements are made on a dedicated cast iron water pipe by an array of seven triaxial geophones. The spectral characteristics of the propagation of leak noise signals from underground water pipes to the ground surface are reported. Furthermore, it is demonstrated that suspicious leakage areas can be readily identified by extracting and fusing the feature patterns at low frequencies where leak noise dominates. The results agree well with the real leakage position in the underground pipeline.

Background: Minimally-invasive measurement of continuous inter-vertebral motion in clinical settings is difficult to achieve. This paper describes the reliability, validity and radiation exposure levels in a new Objective Spinal Motion Imaging Assessment system (OSMIA) based on low-dose fluoroscopy and image processing., Methods: Fluoroscopic sequences in coronal and sagittal planes were obtained from 2 calibration models using dry lumbar vertebrae, plus the lumbar spines of 30 asymptomatic volunteers. Calibration model 1 (mobile) was screened upright, in 7 inter-vertebral positions. The volunteers and calibration model 2 (fixed) were screened on a motorized table comprising 2 horizontal sections, one of which moved through 80 degrees. Model 2 was screened during motion 5 times and the L2-S1 levels of the volunteers twice. Images were digitised at 5fps. Inter-vertebral motion from model 1 was compared to its pre-settings to investigate accuracy. For volunteers and model 2, the first digitised image in each sequence was marked with templates. Vertebrae were tracked throughout the motion using automated frame-to-frame registration. For each frame, vertebral angles were subtracted giving inter-vertebral motion graphs. Volunteer data were acquired twice on the same day and analysed by two blinded observers. The root-mean-square (RMS) differences between paired data were used as the measure of reliability., Results: RMS difference between reference and computed inter-vertebral angles in model 1 was 0.32 degrees for side-bending and 0.52 degrees for flexion-extension. For model 2, X-ray positioning contributed more to the variance of range measurement than did automated registration. For volunteer image sequences, RMS inter-observer variation in intervertebral motion range in the coronal plane was 1.86 degrees and intra-subject biological variation was between 2.75 degrees and 2.91 degrees. RMS inter-observer variation in the sagittal plane was 1.94 degrees. Radiation dosages in each view were below the levels recommended for a plain film., Conclusion: OSMIA can measure inter-vertebral angular motion patterns in routine clinical settings if modern image intensifier systems are used. It requires skillful radiography to achieve optimal positioning and dose limitation. Reliability in individual subjects can be judged from the variance of their averaged inter-vertebral angles and by observing automated image registration.

The validity of spinal fusion for lumbar instability is considered. Some difficulty lies in the interpretation of the term instability. The differing interpretations in the clinical, radiologic, and biomechanical contexts are discussed. These interpretations may only be reconciled if the confusion between hypermobility and instability is removed and some recourse is made to soft tissue integrity. Fusion is considered in the context of the functioning spine as a whole. Although the aim of the surgery is usually to produce a solid arthrodesis, some studies show that this can compromise the functioning of the rest of the spine. Furthermore, there is some evidence that pseudarthrosis itself may not be detrimental. Dynamic imaging offers the potential for improved diagnosis and assessment, but further work is needed to pave the way for better selection criteria and treatment strategies.

In this discussion paper, vertebral translation in the sagittal plane is considered. A number of different measurement protocols are investigated and it is shown that, in general, the protocols lack a clear notion of the ideal. This can lead to difficulties when interpreting clinical data. One possible ideal is encapsulated in the concept of George's line, the posterior vertebral body alignment line. It is shown that translation can be measured such that deviations from George's line are quantified. Furthermore, an intrinsic centre of rotation is implied, and by considering translation in conjunction with intervertebral angle, inferences can be made regarding the position of the instantaneous centre of rotation of the joint. The relationship between static values of translation viewed on a single radiograph and changes in translation viewed across a number of images is also investigated. Results from some previous clinical studies are discussed in the light of the findings.

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.