A histological study of the effect of static traction on degenerated intervertebral disc using an in-vivo rat-tail model

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A histological study of the effect of static traction on degenerated intervertebral disc using an in-vivo rat-tail model

 

Author: Lau, Fung-ling
Title: A histological study of the effect of static traction on degenerated intervertebral disc using an in-vivo rat-tail model
Degree: M.Sc.
Year: 2008
Subject: Hong Kong Polytechnic University -- Dissertations.
Intervertebral disk -- Diseases.
Diseases -- Animal models.
Department: School of Nursing
Pages: xiii, 99 leaves : col. ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2166841
URI: http://theses.lib.polyu.edu.hk/handle/200/1628
Abstract: Intervertebral disc degeneration is a cell-mediated response which is closely related to excess mechanical loading that induces progressive structural failure to mechanical dysfunction and pain. Low back pain, which causes a significant disability and incapacity for individuals and society, is considered a common spinal disorder associated with degenerative disc. In the current study, the histological effects of static traction with high and low distraction forces applied on intervertebral disc with simulated degeneration were investigated using a rat-tail model. Totally, 63 mature Sprague-Dawley male rats were randomly divided into eight groups including one normal, three sham, two static compression and two static traction (low and high dose) groups. The simulated degeneration model was made by applying continuous static compression through two pins inserted at the mid-transverse plane of the 8th and 9th caudal vertebral bodies adjacent to the target disc for two weeks. Normal control group rats, without any treatment or pin insertion surgery, provided normal disc morphology; while the sham pin inserted groups, with only two pins inserted, were used to study the effects of pin insertion on the target discs as well as the upper and lower adjacent discs. Static compression groups after loaded were used to study the compression degenerative effects on the intervertebral disc. This was important to evaluate a workable model for disc degeneration therapy studies. Static traction, with both low (1.4N, 15% body weight) and high (4.2N, 45% body weight) magnitude, was applied to the compressed disc using a specially designed loading jig for three weeks with each traction session last for 30 minutes for five times per week. All the rats after the end of each protocol were then sacrificed and discs harvested for histological processing for the semi-quantification of the area, cell density and proteoglycan inside nucleus pulposus and qualitative assessment of the overall disc morphological changes. Results showed that there were no significant traction effects (both low and high dose) on the degenerated intervertebral disc when compared with group of discs absent from treatment for the normalized nuclear area, cell density, total percentage of proteoglycan as well as degeneration grading (p>0.05). Although low dose static traction demonstrated stimulation on nucleus cell production by increasing the cell density from which this might be considered a compensation means for the disc to demonstrate repairing and remodeling ability, qualitative microscopic exanimation observed little recovery morphological changes. Majority of the cell morphology observed was in abnormal spindle-like form. Serious degenerated-like appearance still existed with the mean grading score 6.5 which was the same as the compression group without traction. The disorganized annulus lamella did not reverse but became even more distorted enclosed inside with a fibrotic nucleus pulposus. High dose static traction, however, had noted a suppression and significant decrease in cell production when compared with low dose static traction. Microscopic assessment however observed both highly degenerated and normal disc patterns that further investigations were required. The findings indicated that static traction did stimulate disc internal environment with effects on the composition of the disc. The occurrence of highly abnormal cell morphology might imply the threshold the disc could maintain its normal states were exceeded.

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