Significance of Bone Mineral Density

What is BMD

BMD stands for Bone Mineral Density and this figure gives a snapshot of the structural integrity of your bones at that given point in time. This test is essential for individuals with Paralysis or SCI’s as it can give a greater idea of predictability of bone mineral density. These types of disorders can lead to a multitude of downstream effects if they are not treated quickly and effectively after the injury is sustained. Preventing the onset of Low BMD can have a drastic impact on quality of life and help discourage the likelihood of bone breaks and fractures.

What is the progression of Low BMD

The progression of the problem disorders associated with low bone mineral density follow a gradient scale. As the degradation of the bone tissue continues, the risk of potential bone break or fractures continues to increase as well. (Insert color picture of scale) A normal individual has a BMD of anywhere between 1.099 g/cm^2 through 1.301 g/cm^2, which in layman’s terms, is described as being +1 to -1 standard deviations (SD) away from the average. The first notice of low bone mineral density occurs when the individual’s BMD dips down between -1 and -2.5 SD. This is classified as Osteopenia and is referred to as the middle ground between normal BMD and Osteoporosis. Lastly, is full blown Osteoporosis and is distinguished when the SD slides below -2.5 SD. The internal integrity of the bony structures becomes greatly more porous and compromises the stability and density of the bone (insert picture of bones). Researchers have begun using the phrase “Osteoporosis has moved from a disease of fractures to a disease of fracture risks” (Osteo after SCI, pg.184). Additionally “it has been shown that BMD is a significant predictor of an increased frequency of fractures in patients with SCI when age, the duration after SCI and level of SCI were simultaneously considered” (Osteo after SCI, pg.184). Research conducted by the International Spinal Cord Society has shown that “fracture frequency increased when BMD was lower than 1.0 g/cm^2 and fracture risk increased 2.2 times when BMD reduced by 0.1 g/cm^2.” (Spinal Cord 2008, pg. 731.). These findings present a reality that is imperative for individuals with spinal cord injuries to be aware of. Being conscious of this type of information can greatly help improve one’s likelihood of prevention of bone breaks and fractures which can leave an individual bedridden for days, weeks and even months if low BMD is left untreated.

Normal: +1 – -1 Standard deviations

Low Bone Mass (Osteopenia): -1 – -2.5 SD

Osteoporosis: -2.5 and greater SD

How to treat BMD?

When looking at the best practices to help combat low BMD, research has shown a few specific routes in which we can help reverse or halt the development and onset of Osteoporosis. The first and foremost method of treating low BMD is by returning to physical activity and weight-bearing/ standing positions. A 2008 study by the International Spinal Cord Society demonstrated a marked difference in BMD between a group of individuals with SCI who were standing daily verses those who were not. The standing group was asked to be in their standing frame from 1+ hour for 5 days/week. The results speak for themselves: within the first year of injury the standing group had a reduction of BMD of 19.62% while the non-standing group had a reduction of 24%. Additionally, the actual density of the bones had a substantially marked increase from the non-standing to the standing group from 0.91 g/cm^2 to 1.018 g/cm^2, respectfully. These findings suggest, when using the research already presented above, show the non-standing group is at a significantly greater risk of bone fracture or break.

What are the significance of the results?

Research: Spinal Cord (2008) – int. Spinal cord society

Well marked difference in BMD for LE post injury

Standing group – BMD reduction of 19.62% in the first year

Non-standing group – BMD reduction of 24% in first year

Two years post SCI

Standing BMD – 1.018 g/cm^2 (0.971-1.055 g/cm^2)

Non-Standing BMD – 0.91 g/cm^2 ( 0.872-0.958 g/cm^2)

“Researchers have shown that fracture frequency increased when BMD was lower than 1.0 g/cm2 and fracture risk increased 2.2 times when BMD reduced by 0.1 g/cm^2.” pg. 731

Conclusion: 

SCI patients w/ > 1 hr standing 5+ days/week had significantly increased BMD in Lower Extremities after 2 years post injury

Research : Osteoporosis after SCI

“Functional Stimulated exercise may contribute to the prevention of bone loss to some extent”

“Osteoporosis has moved from a disease of fractures to a disease of fracture risks [43, 44, 45]… It has been shown that BMD is a significant predictor of an increased frequency of fractures in patients with SCI when age, the duration after SCI and level of SCI were simultaneously considered” pg 184

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