Osteoporosis and Bone Fracture
May 20, 2010
An important health issue for postmenopausal women is osteoporosis. This disease is characterized by low bone mass and a change in bone structure that can lead to fractures. The medical community is particularly concerned with the risk of fractures of the hip bone and spinal column vertebrae. Osteoporosis is in general defined by bone mineral density (BMD) as measured by X-rays on the spine or hip. Although the idea of bone strength is controversial within the medical community, it is known that both bone density and bone quality is driven by bone turnover. At menopause, bone turnover increases by 300-400%, which drives most of the changes in bone as aging occurs. To get a simplistic view of this we will look at 2 important qualities of bone, including bone mineral density (BMD) and the structure of bone itself.
Bone comes in two forms: a spongy (inner) bone architecture full of fluid filled spaces and cortical (hard) bone covering spongy bone. It is not just the amount of calcium (mineralization) present in bone that makes it strong but also the actual geometry of cortical and spongy bone. Spongy bone is a very holey bone with many fluid filled spaces that allows for stress on bone in many different directions giving bone a flexible nature as well as making the inner bone very lightweight. Cortical (hard) bone is very dense (much more solid) and supportive in gravity, in other words, weight bearing. During osteoporosis, horizontal spongy bone is lost, leaving mostly vertical spongy bone causing bone to be less resilient with forces along the horizontal plane. On the other hand, cortical bone becomes more like spongy bone (filled with holes like Swiss cheese). In other words, changes in structure are a major contributing factor to fractures. Osteoporosis affects cortical bone in that it causes uneven resorption rates between the inside and outside of the bone, so cortical bone becomes thinner and thinner. Bones that fracture have a higher percentage of holes in cortical bone even though their mineral content may be higher than normal. In fact, this creates a brittle bone that is easier to fracture as has been observed in Fosamax femur fractures. For small increases in cortical porosity (holes), you get a large reduction in bone strength. Ideally, you want to block inside resorption while allowing for normal resorption outside bone to maintain balance.
Studies Concerning Bisphosphonates and Fractures
Studies from 10 years ago demonstrated that a 5mg daily dose (results are dose and generic drug dependent) of alendronate reduced inside cortical resorption by 46%; however, the cortex didn’t thicken in the presence of this bisphosponate. Ideally, what you are trying to do is to increase bone density and reduce bone turnover to decrease cortical porosity (stop holes from forming in cortical bone) and increase cortical thickness across bone.
Clearly older women have a higher cortical porosity, but data is too limited to be able to properly evaluate this disease. Again, sample size is small because it is hard to get biopsies given that women have to volunteer to give these samples. Without volunteers, specimens come from cadavers. Some bisphosphonates have been tested for 2 to 3 years whereas Fosamax has now been tested for 10 years, but using a very small sample size. All bisphosphonates have been shown to reduce cortical porosity with proper doses as compared with placebo groups. The Fosamax femur fracture is still unexplained. A femur fracture is normally very rare given that the femur is the strongest bone in the body. This side effect can be debilitating, requiring surgical intervention and long term therapy.
If you have experienced a Fosamax femur fracture, or any other bone related illness while on Fosamax you may be entitled to financial compensation. Fosamax lawsuits are currently being filed across the country.
Susan Ardizzoni, Ph.D. holds a Doctorate in Biology with a major in Neuroscience (medical) and minors in Biochemistry, Physics, and Mathematics with experience in basic and clinical research. Although the author is not an attorney, this article was sponsored by the law firm of Bernstein Liebhard LLP and constitutes Attorney Advertising. To learn more about Fosamax femur fracture or Fosamax lawsuit please visit www.ConsumerInjuryLawyers.com.