| "Low back pain is the price for standing up of human being". The statistical data shows that up to 80% of the population will experience a significant episode of low back pain in their lifetimes. Although the mechanism of low back pain is not clear, degenerative disc disease and disc space narrow are important factors for contributing to low back pain. Because the intervertebral disc is responsible for providing the flexibility and bearing the load beyond the joints complex and is a relatively weak link, it is more vulnerable to degeneration, which can result in disc space narrow. Studies showed that the stress distribution would be variation after disc narrowed, and it would contribute to the degeneration of facet joints. So it is necessary to rebuild the anterior column by rigid implants with great compressive strength during degenerative disc disease surgery. However, because of high stiffness of those rigid implants, there is concern of implants subsidence with time, which can result in the disc height losing again. On the other hand, it is impossible to distract the disc space to an ideal height in certain conditions and the surgeons have to choice smaller size implants. There are many biomechanic studies about stress distribution of disc or facet joints, but no study discovered thecritical height of intervertebral space subsidence that could cause stressvariation significantly between anterior column and posterior column at lumbar spine. The stress distribution in disc space and facet joint followed disc space height alteration at L4/5 was discussed in the current study. The author hope the current reseach can discover the critical height of disc space that would result in stress distribution altering significantly.Since it first was introduced more than 90 years ago, disc arthrodesis remains the main surgical method for the treatment of degenerative disc disease. Although this procedure does relatively well in stabilizing the anterior column and relieving low back pain by eliminating motion, it is not physiologic and it alters the stress distribution on the adjacent segment, which would cause degeneration on adjacent segment and recurrent low back pain. The ultimate solution for reestablishing anterior column stability is to restore not only the anatomy but also the normal mechanical function by using a more functional device, artificial disc prosthesis. During the past 40 years, many different designs have been attempted for artificial disc prosthesis. Today, the most clinical used artificial disc is SB Charite prosthetic disc, and the early clinical studies have shown promising results. However, no clinical study has revealed the efficiency of this treatment on restoring and maintaining the disc space height at the operated and adjacent segments. To answer the question mentioned above, the clinical data from 20 patients who operated with artificial disc replacements was retrospected and analyzed in the current study.PART ONE: In vitro Biomechanic Study between Disc Space Height and Stress DistributionObjective: To explore the relationship between the stress distribution of lumbar spine and the intervertebral space height, to reveal the importance of restoring and maintaining disc space height during intervertebral surgery.Methods: Seven lumbar spine segments (L3-L5) from young people who died from accidents were used to test in vitro. The intervertebral space height of L4/5 was measured before loading. The L4/5 disc tissues were cleared but the subchondral bone and posterior longitudinal ligament were reserved. In order to get the pressures in intervertebral space and facet joint of L4/5, one transducer was placed in the intervertebral space and the other was in the left facet joint of the same segment. Five rigid washers (the height of each washer was 1.4mm) were placed on the transducer in intervertebral space to control and regulate the intervertebral space height. And when all the five washers were at intervetebral space, then the intervetebral space height was defin...
|
PDF Full Text Request