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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A study was carried out to analyze the pattern of the age related bone loss in the mandibular cortex and to establish normal values and the observed range of morphometric variables on microradiograms of bone sections taken from a well defined site anterior to and below the mental foramen. Specimens were obtained from 100 Danish subjects with no known systemic bone disease or severe mandibular atrophy. Microradiograms of 100-micron-thin undemineralized vertical ground cross-sections were produced. An electric point-counting system was used for the determination of 1) percentage bone mass, 2) mean cortical width (MCW), and 3) the percentage of Haversian canals with resorption surfaces. The analysis showed that cortical porosity and the percentage of Haversian canals showing resorption are unrelated to sex and increased after the age of 50. MCW and absolute bone mass (MCW x % bone mass) are greater in males than in females and show a parallel age related decrease after the age of 50. Furthermore, the age related increase in cortical thinning and porosity is dependent on the individual as well as on age. Marked individual variation confined the use of these parameters to group analysis.
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PMID:Pattern of age related bone loss in mandibles. 692 61

In normal individuals, peak bone mass is reached at 25-35 years of age and thereafter a decrease with age occurs in both sexes. An acceleration in the bone loss is observed in normal women at menopause. Because of either a low peak bone mass or a more pronounced bone loss with age or during menopause, some individuals reach the fracture threshold for bone mass and suffer spontaneous fractures. To understand the mechanism behind age related bone loss, one must recognize that bone in adults is continually renewed through internal reorganization by which bone is turned over by localized osteoclastic resorption followed by osteoblastic formation (remodelling). A total reconstruction of the resorptive and formative phase can be performed by histomorphometric methods applied on iliac crest bone biopsies and thereby give a detailed description of resorptive and formative events. By the remodelling process bone may be gained or lost by 3 mechanisms: 1. Reversible bone loss depending on the magnitude of the remodelling space, which is the amount of bone resorbed and not yet reformed during the remodelling sequence. 2. Irreversible thinning of the trabeculae due to a negative balance at the remodelling site. 3. Irreversible loss of whole trabecular elements caused by deep resorption lacunae perforating the trabecular plates. Although the bone mass is significantly reduced by 20-30% in postmenopausal osteoporotic patients with vertebral fractures compared with normal controls a substantial overlap exists. Our study and several other studies have shown that beside the slight reduction in trabecular bone volume significant differences in microstructure exist between osteoporotic patients and normal controls. These changes in structure are probably a consequence of trabecular plate perforations. Although osteoporotic patients in term of remodelling (bone turnover) are a very heterogeneous group, with patients having a low, normal and even increased bone turnover, no signs in the ongoing remodelling process was found in our study that could explain why these patients had developed osteopenia and changes in the trabecular structure. The bone balance was in the patients slightly negative but no different from the balance found in normal controls. The cause of osteoporosis may therefore be factors occurring earlier in life, maybe long before the manifestation of the disease. Bone mass at any age is the result of two variables--the amount of bone achieved during growth and the subsequent rate of bone loss. Peak bone mass at maturity may be of great importance in determining the risk of developing symptomatic osteoporosis.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Bone histomorphometry in the pathophysiological evaluation of primary and secondary osteoporosis and various treatment modalities. 766 70

Although it is known that long cortical bone structurally alter their area moment of inertia with age related bone loss maintaining their bending strength, the incidence of fragility fractures associated with cortical thinning still prevails. We hypothesize that cortical thinning with aging increases the local buckling susceptibility under abnormal or eccentric loads, and initiates fracture. The paper presents a series of 3D geometrical model derived from CT scans of a human femoral neck used to simulate age-related bone loss. The purpose of the model is to predict the susceptibility of local buckling at the femoral neck in falls by elderly folks. Geometric three-dimensional models of femoral neck cortices were developed from 7 human cadaver femurs (4 female, 3 male, 52-68 years). Three age related femoral neck models were simulated by either reducing (young age-related model) or increasing (old age-related model) the outer cortical surfaces in the radial-direction, by 1-mm. The control model was the middle-age related model. The inner cortex diameter was also adjusted to equilibrate the compressive stresses, based on the load-profile of a single-legged stance. Based on the old age related model, two additional "fragile" models were simulated by reducing the compressive load profile by 10 and 20% changing the inner cortex diameter, respectively. Using these models for each specimen, the consequence of a fall on the greater trochanter was evaluated. The Finite Strip Method (FSM) was used to investigate the association between local buckling at the femoral neck and the load to failure. Under constant loading, buckling progressively reduced the load to failure with aging, as seen in 2/7 of the middle age (by 9-15%) and 5/7 of the old age (by 7-32%) related models. In the fragile models, a 51% reduction in the load to failure was noted. Structural adaptation to age-related bone loss might preserves the bending strength under physiologic loads, but cortical thinning effects the buckling ratio reaching a critical threshold that would make the bone susceptible to local buckling at the femoral neck increasing the risk of fracture in a fall.
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PMID:Assessing the susceptibility to local buckling at the femoral neck cortex to age-related bone loss. 1958 40