Investigation of the in-vitro loading on an artificial spinal disk prosthesis

Spinal diseases imposes considerable burden to both patients and society. In recent years, much surgical efforts have been made in advancing the treatment of neck and back pain. Of particular prominence is the increasing clinical acceptance and use of intervertebral artificial disk prosthesis for the treatment of discogenic back pain. Despite this increased use of such disks, their in-vivo monitoring remains rudimentary. In an effort to develop an intelligent artificial spinal disk where the in-vivo loading of the spine can by studied for the first time an experimental set up has been created in order to initially study the in-vitro loading on an artificial disc prosthesis. Eight strain gauges and two piezoresistive sensors were used and placed suitably in the artificial disk prosthesis. The results from the in-vitro loading showed linear relationship between loading and the outputs from the sensors with good repeatability and less hysteresis

On the experimental intradiscal pressure measurement techniques : a review

Series : Mechanisms and machine science, ISSN 2211-0984, vol. 24The intradiscal pressure has been essential for prevent the spinal complaints by forming a basis for clinical advice to promote the correct sitting postures. As a consequence, it is evident the need of an accurate method for measure the intradiscal pressure, to better understand the disc response to hydorstatic pressure fluctuations. Numerous reviews regarding disc mechanics are available, including intradiscal pressure benchmarks; however, an analysis on the techniques of intradiscal pressure measurement is needed. Therefore, this review will remain focused on the methodologies adopted for measure the intradiscal pressure in several conditions: for different daily activities, under external loads and for values where occurs annulus fibrosus disruption. The importance of the intradiscal pressure on disc function will be discussed as well as the some guidelines for design new measurement techniques will be defined

Biomechanical analysis of the lumbar spine on facet joint force and intradiscal pressure - a finite element study

<p>Abstract</p> <p>Background</p> <p>Finite element analysis results will show significant differences if the model used is performed under various material properties, geometries, loading modes or other conditions. This study adopted an FE model, taking into account the possible asymmetry inherently existing in the spine with respect to the sagittal plane, with a more geometrically realistic outline to analyze and compare the biomechanical behaviour of the lumbar spine with regard to the facet force and intradiscal pressure, which are associated with low back pain symptoms and other spinal disorders. Dealing carefully with the contact surfaces of the facet joints at various levels of the lumbar spine can potentially help us further ascertain physiological behaviour concerning the frictional effects of facet joints under separate loadings or the responses to the compressive loads in the discs.</p> <p>Methods</p> <p>A lumbar spine model was constructed from processes including smoothing the bony outline of each scan image, stacking the boundary lines into a smooth surface model, and subsequent further processing in order to conform with the purpose of effective finite element analysis performance. For simplicity, most spinal components were modelled as isotropic and linear materials with the exception of spinal ligaments (bilinear). The contact behaviour of the facet joints and changes of the intradiscal pressure with different postures were analyzed.</p> <p>Results</p> <p>The results revealed that asymmetric responses of the facet joint forces exist in various postures and that such effect is amplified with larger loadings. In axial rotation, the facet joint forces were relatively larger in the contralateral facet joints than in the ipsilateral ones at the same level. Although the effect of the preloads on facet joint forces was not apparent, intradiscal pressure did increase with preload, and its magnitude increased more markedly in flexion than in extension and axial rotation.</p> <p>Conclusions</p> <p>Disc pressures showed a significant increase with preload and changed more noticeably in flexion than in extension or in axial rotation. Compared with the applied preloads, the postures played a more important role, especially in axial rotation; the facet joint forces were increased in the contralateral facet joints as compared to the ipsilateral ones at the same level of the lumbar spine.</p

Delineating inflammatory and mechanical sub-types of low back pain: a pilot survey of fifty low back pain patients in a chiropractic setting

Background An instrument known as the Mechanical and Inflammatory Low Back Pain (MAIL) Scale was drafted using the results of a previous expert opinion study. A pilot survey was conducted to test the feasibility of a larger study designed to determine the MAIL Scale's ability to distinguish two potential subgroups of low back pain: inflammatory and mechanical. Methods Patients with a primary complaint of low back pain (LBP) presenting to chiropractic clinics in Perth, Western Australia were asked to fill out the MAIL Scale questionnaire. The instrument's ability to separate patients into inflammatory and mechanical subgroups of LBP was examined using the mean score of each notional subgroup as an arbitrary cut-off point. Results Data were collected from 50 patients. The MAIL Scale did not appear to separate cases of LBP into the two notionally distinct groups of inflammatory (n = 6) or mechanical (n = 5). A larger "mixed symptom" group (n = 39) was revealed. Conclusions In this pilot study the MAIL Scale was unable to clearly discriminate between what is thought to be mechanical and inflammatory LBP in 50 cases seen in a chiropractic setting. However, the small sample size means any conclusions must be viewed with caution. Further research within a larger study population may be warranted and feasible

Biomechanical factors in the progression of idiopathic scoliosis

Idiopathic scoliosis is present when, in upright positions of the trunk, the spine curves to the side for unknown reasons. This paper reviews evidence concerning some biomechanical factors that might underlie the progression of such curves. The review concentrates on studies conducted in our laboratories. Arguments are made, based on biomechanical analyses and experiments, that progression occurs because of defects in the postural control system of the spine.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43994/1/10439_2006_Article_BF02371453.pd

Inter-rater reliability of three standardized functional tests in patients with low back pain

<p>Abstract</p> <p>Background</p> <p>Of all patients with low back pain, 85% are diagnosed as "non-specific lumbar pain". Lumbar instability has been described as one specific diagnosis which several authors have described as delayed muscular responses, impaired postural control as well as impaired muscular coordination among these patients. This has mostly been measured and evaluated in a laboratory setting. There are few standardized and evaluated functional tests, examining functional muscular coordination which are also applicable in the non-laboratory setting. In ordinary clinical work, tests of functional muscular coordination should be easy to apply. The aim of this present study was to therefore standardize and examine the inter-rater reliability of three functional tests of muscular functional coordination of the lumbar spine in patients with low back pain.</p> <p>Methods</p> <p>Nineteen consecutive individuals, ten men and nine women were included. (Mean age 42 years, SD ± 12 yrs). Two independent examiners assessed three tests: "single limb stance", "sitting on a Bobath ball with one leg lifted" and "unilateral pelvic lift" on the same occasion. The standardization procedure took altered positions of the spine or pelvis and compensatory movements of the free extremities into account. The inter-rater reliability was analyzed by Cohen's kappa coefficient (κ) and by percentage agreement.</p> <p>Results</p> <p>The inter-rater reliability for the right and the left leg respectively was: for the single limb stance very good (κ: 0.88–1.0), for sitting on a Bobath ball good (κ: 0.79) and very good (κ: 0.88) and for the unilateral pelvic lift: good (κ: 0.61) and moderate (κ: 0.47).</p> <p>Conclusion</p> <p>The present study showed good to very good inter-rater reliability for two standardized tests, that is, the single-limb stance and sitting on a Bobath-ball with one leg lifted. Inter-rater reliability for the unilateral pelvic lift test was moderate to good. Validation of the tests in their ability to evaluate lumbar stability is required.</p

The course of pain drawings during a 10-week treatment period in patients with acute and sub-acute low back pain

BACKGROUND: Pain drawings are widely used as an assessment of patients' subjective pain in low back pain patients being considered for surgery. Less work has been done on primary health care patients. Moreover, the possible correlation between pain drawing modalities and other pain assessment methods, such as pain score and functional variables needs to be described. Thus, the objectives were to describe the course of pain drawings during treatment in primary health care for low back pain patients. METHODS: 160 primary health care outpatients with acute or sub-acute low back pain were studied during 10 weeks of a stay active concept versus manual therapy in addition to the stay active concept. The patients filled out 3 pain drawings each, at baseline and after 5 and 10 weeks of treatment. In addition the patients also reported pain and functional variables during the 3 measurement periods. RESULTS: The proportion of areas marked, the mean number of areas marked (pain drawing score), mean number of modalities used (area score), and the proportion of patients with pain radiation all decreased during the 10-week treatment period. Most of the improvement occurred during the first half of the period. The seven different pain modalities in the pain drawing were correlated to pain and functional variables. In case of no radiation some modalities were associated with more pain and disability than others, a finding that grew stronger over time. For patients with pain radiation, the modality differences were smaller and inconsistent. CONCLUSION: Pain modalities are significantly correlated with pain and functional variables. There is a shift from painful modalities to less painful ones over time

The Virtual-Spine Platform—Acquiring, visualizing, and analyzing individual sitting behavior

Back pain is a serious medical problem especially for those people sitting over long periods during their daily work. Here we present a system to help users monitoring and examining their sitting behavior. The Virtual-Spine Platform (VSP) is an integrated system consisting of a real-time body position monitoring module and a data visualization module to provide individualized, immediate, and accurate sitting behavior support. It provides a comprehensive spine movement analysis as well as accumulated data visualization to demonstrate behavior patterns within a certain period. The two modules are discussed in detail focusing on the design of the VSP system with adequate capacity for continuous monitoring and a web-based interactive data analysis method to visualize and compare the sitting behavior of different persons. The data was collected in an experiment with a small group of subjects. Using this method, the behavior of five subjects was evaluated over a working day, enabling inferences and suggestions for sitting improvements. The results from the accumulated data module were used to elucidate the basic function of body position recognition of the VSP. Finally, an expert user study was conducted to evaluate VSP and support future developments