The Effects of Antifracture Therapies on the Components of Bone Strength: Assessment of Fracture Risk Today and in the Future

doi:10.1016/j.semarthrit.2006.04.001

Seminars in Arthritis and Rheumatism

Volume 36, Issue 1, August 2006, Pages 10-21

https://doi.org/10.1016/j.semarthrit.2006.04.001 Get rights and content

Objective

To summarize the current knowledge regarding the impact of the most common antifracture medications on the various determinants of bone strength.

Methods

Relevant English-language articles acquired from Medline from 1966 to January 2005 were reviewed. Searches included the keywords bone AND 1 of the following: strength, remodeling, microcrack, structure, mineralization, collagen, organic, crystallinity, osteocyte, porosity, diameter, anisotropy, stress risers, or connectivity AND alendronate, estrogen, etidronate, hormone replacement therapy, parathyroid hormone, risedronate, OR teriparatide. Abstracts from relevant conference proceedings were also reviewed for pertinent information.

Results

Antiresorptive therapies increase bone strength through decreasing bone turnover. This lower bone turnover results in a higher mean mineralization and decreases the number of active resorption pits within bone at any given time. These resorption pits are speculated to be areas of focal weakness and a higher number of them would, if all other things were equal, result in greater fragility. Parathyroid hormone therapy increases the rate of bone remodeling, which introduces many resorption pits, but this source of strength loss is thought to be compensated by rapid increases in bone mass.

Conclusions

Both the antiresorptives, particularly bisphosphonates, and the parathyroid hormone therapy increase bone strength; however, the changes that are elicited to achieve this differ significantly.

Section snippets

Methods

Relevant English-language articles acquired from Medline from 1966 to January 2005 were reviewed. Searches included the keywords “bone” AND 1 of the following: “strength,” “remodeling,” “microcrack,” “structure,” “mineralization,” “collagen,” “organic,” “crystallinity,” “osteocyte,” “porosity,” “diameter,” “anisotropy,” “stress risers,” or “connectivity” AND “alendronate,” “estrogen,” “etidronate,” “hormone replacement therapy,” “parathyroid hormone,” “risedronate,” OR “teriparatide.” All

The Effects of Antifracture Therapies on the Material Properties of Bone

There is limited information regarding the effects of antifracture therapies on the material components of bone as this necessitates the collection of repeated bone biopsies for histomorphometric analyses, which are infrequently acquired due to their invasive nature. However, biopsy data acquired from phase III clinical trials and animal data have provided clues as to how antifracture therapies impact the material properties of bone.

Discussion

Antiresorptive therapy, particularly with the bisphosphonates, generally increases mean mineralization and homogeneity of mineralization. It is suggested that almost the entire change in the aBMD induced by the antiresorptive therapies are a consequence of the increases in the MDMB. PTH therapy decreases mean mineralization and increases the mineralization heterogeneity; however, bone mass is significantly increased. The impact of therapies on the crystallinity of bone and on the organic

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