Fracture prevention & healing
Fractures 101 — an overview of the physiology, physics, types, and risks of fractures
by Dr. Susan E. Brown, PhD
Topics covered in this article:
- Fracture risks — What are the risks for bone fracture?
- Physiology — Bone processes and functions and their relationship to fracture
- The physics — What physical conditions in the bones predispose them to fracture?
- Types of fractures — What different kinds of bone fractures can happen?
Fracture risks — what factors predict risk for bone fracture?
Nearly 30 years ago, when bone density testing machines were first being developed, we thought low bone density was what mattered most in determining a person’s risk for osteoporotic fractures. Since that time, bone density testing has become the standard of health care throughout the developed nations, where fracture rates are highest.
Common variables used to determine 10-year risk of osteoporotic fracture
- Weight and height (Body mass index <21)
- History of previous fracture
- Parental history of hip fracture
- Smoking status
- Use of glucocorticoid drugs
- Rheumatoid arthritis
- Secondary disorders linked to osteoporosis, such as type 1 diabetes
- Drinking more than 3 alcoholic beverages per day
Other important factors
- Postural instability
- Poor vision
- pH balance
- Vitamin D status
- Use of proton pump inhibitors (PPI’s)
- Use of antidepressants
Nowadays, we know that rates of fracture tend to be higher in people with low bone density only in certain populations, and only under certain conditions. After following thousands of people over time, bone researchers have found that the majority of those who fracture do not have osteoporotic bone density, but actually have bone density that is osteopenic, or even normal!
What’s more, many people who, on testing, would be given a diagnosis of osteoporosis never go on to experience fracture. Clearly, the expectations we placed on bone densitometry technology as a straightforward means of predicting fracture risk have fallen short.
To illustrate this point, let’s take a closer look at the case of hip fractures in the elderly, since they are some of the most problematic types of fracture in older people.
Up until the mid-1990’s, it was widely held that many risk factors for hip fracture — weight loss, family history, and physical inactivity for instance — acted at least partly through their effects on bone density, whereas others — postural instability and sedative use — acted by influencing a person’s risk of falls. Then, in the 1990’s, a four-year study of nearly 10,000 Caucasian American women over the age of 65 revealed that all the above-listed factors exerted significant effects on the risk of fracture — after adjustment for base-line bone density.
This raised the possibility that the risk of hip fracture involved factors other than bone density and the risk of falling. Just some of the factors the researchers identified were the size, shape, and architecture of bone, as well as the type and severity of falls. Plus, the authors of the study identified independent risk factors, including low body weight, physical inactivity, a maternal history of hip fracture, use of long-acting benzodiazepines, and impaired vision.
We have also realized over the intervening years how greatly risk factors interact with each other, and have learned they can become increasingly or less important as people grow older. That’s in part why certain types of fractures are more common in certain age groups. But while we understand now that there are many variables at play in the fracture prediction equation, the reality remains that the majority of hip fractures — and the most burdensome of all osteoporotic fractures — occur within the elder segment of our population.
As foreboding as that may sound, the truth is that the longer a person lives, the more likely she/he is to experience one or more osteoporotic fractures. If there is one thing we want you to know about statistics, it is that they are only a best guess — not a sentence! Obviously, reduction of geriatric fracture is a worthwhile goal, for it would both provide our elderly with a higher quality of life and substantially reduce the healthcare costs of aging.
The good news is that both these goals lie well within our reach today. Current scientific literature nicely documents the special nutrient and lifestyle needs of elderly people. Meeting these special needs could substantially reduce the incidence of fracture in older folks. For example, the recurrence of vertebral fractures can be more than halved, and the incidence of hip fractures can be decreased by over 40%, by simply administering appropriate nutritional supplementation. Additionally, muscle mass can be increased 90% or more — even among 90-year-olds — with simple strength-building exercises! Balance can be improved and falls reduced with vitamin D therapy. And the gentle movement and breathing exercises embodied in the practices of yoga, t’ai chi, and qi gong reduce fracture risk through many mechanisms. Further, simple lifestyle modifications and attention to the special nutrient needs of the elderly can significantly reduce the incidence of falling, and thus further enhance well-being and reduce fracture risk.
While the above approach offers us a practical and effective means to reduce geriatric risk of fracture, many elements of this approach could be just as readily applied to younger populations. No matter what your age, caring for yourself by getting regular exercise, eating a healthy diet, and supplementing your nutrition appropriately can significantly minimize your fracture risk.
So it’s not just your bone density, your statistical risk of falling, or your numerical age that determine the likelihood that you will fracture. With the realization that risk of osteoporotic fracture changes over time as a result of numerous variables interacting with one another — from what we eat and drink to our genetics — bone researchers have devised various algorithms to more accurately estimate an individual’s overall risk than can be obtained by bone-density tests alone. These fracture risk assessment tools are very useful, yet the science remains a young one. Every day, we develop a broader vision as, little by little, the complex interplay of numerous factors reveals itself to our understanding.
I write more about the history and science behind these tools in my article on how we can tell who will fracture. I encourage you to check out your own risk with the Better Bones Fracture Risk and Bone Health Profile tool. You can also learn more about protecting your bones through our article on fracture prevention and fall prevention.
Please click here for information on bone processes and functions and their relationship to fracture.
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Original Publication Date: 01/01/2009
Last Modified: 07/10/2012
Principal Author: Dr. Susan E. Brown, PhD