Comparison of the biomechanical effects of lumbar disc degeneration on normal patients and osteoporotic patients: A finite element analysis

Osteoporosis is a common disease characterised by a systemic impairment of bone mass and microarchitecture that results in fragility fractures. With an ageing population, the medical and socioeconomic effect of osteoporosis, particularly postmenopausal osteoporosis, will increase further. A detailed knowledge of bone biology with molecular insights into the communication between bone-forming osteoblasts and bone-resorbing osteoclasts and the orchestrating signalling network has led to the identification of novel therapeutic targets. Novel treatment strategies have been developed that aim to inhibit excessive bone resorption and increase bone formation. The most promising novel treatments include: denosumab, a monoclonal antibody for receptor activator of NF-κB ligand, a key osteoclast cytokine; odanacatib, a specific inhibitor of the osteoclast protease cathepsin K; and antibodies against the proteins sclerostin and dickkopf-1, two endogenous inhibitors of bone formation. This overview discusses these novel therapies and explains their underlying physiology. Copyright © 2011 Elsevier Ltd. All rights reserved.

Review and reinterpretation of existing literature. To suggest how intervertebral disc degeneration might be distinguished from the physiologic processes of growth, aging, healing, and adaptive remodeling. The research literature concerning disc degeneration is particularly diverse, and there are no accepted definitions to guide biomedical research, or medicolegal practice. The process of disc degeneration is an aberrant, cell-mediated response to progressive structural failure. A degenerate disc is one with structural failure combined with accelerated or advanced signs of aging. Early degenerative changes should refer to accelerated age-related changes in a structurally intact disc. Degenerative disc disease should be applied to a degenerate disc that is also painful. Structural defects such as endplate fracture, radial fissures, and herniation are easily detected, unambiguous markers of impaired disc function. They are not inevitable with age and are more closely related to pain than any other feature of aging discs. Structural failure is irreversible because adult discs have limited healing potential. It also progresses by physical and biologic mechanisms, and, therefore, is a suitable marker for a degenerative process. Biologic progression occurs because structural failure uncouples the local mechanical environment of disc cells from the overall loading of the disc, so that disc cell responses can be inappropriate or "aberrant." Animal models confirm that cell-mediated changes always follow structural failure caused by trauma. This definition of disc degeneration simplifies the issue of causality: excessive mechanical loading disrupts a disc's structure and precipitates a cascade of cell-mediated responses, leading to further disruption. Underlying causes of disc degeneration include genetic inheritance, age, inadequate metabolite transport, and loading history, all of which can weaken discs to such an extent that structural failure occurs during the activities of daily living. The other closely related definitions help to distinguish between degenerate and injured discs, and between discs that are and are not painful.

Cross-sectional magnetic resonance imaging (MRI) study. To study the relation of low back pain (LBP) to disc degeneration in the lumbar spine. Controversy still prevails about the relationship between disc degeneration and LBP. Classification of disc degeneration and symptoms varies, hampering comparison of study results. Subjects comprised 164 men aged 40-45 years-53 machine drivers, 51 construction carpenters, and 60 office workers. The data of different types of LBP, individual characteristics, and lifestyle factors were obtained from a questionnaire and a structured interview. Degeneration of discs L2/L3-L5/S1 (dark nucleus pulposus and posterior and anterior bulge) was assessed with MRI. An increased risk of LBP (including all types) was found in relation to all signs of disc degeneration. An increased risk of sciatic pain was found in relation to posterior bulges, but local LBP was not related to disc degeneration. The risks of LBP and sciatic pain were strongly affected by occupation. Low back pain is associated with signs of disc degeneration and sciatic pain with posterior disc bulges. Low back pain is strongly associated with occupation.