Bone Mineral Density For Bone Fracture Calculator

How does this bone mineral density for bone fracture calculator work?

This health tool evaluates 5 year different type of fracture risk based on the age of the patient, their score in the bone mineral density test (BMD T) and some other risk factors. The form is easy to administer by both specialists and patients and provides an immediate prognostic result.

The items used in the bone mineral density for bone fracture calculator are described below:

■ The age of the patient – age is factored in as risky after 65 and posing significant risk after 85;

■ The BMD T score – the lower the score, the higher the fracture risk;

■ Arm assistance to stand from chair – indication of poor stability and a two-fold increased risk of fracture of people with a BMI of 20 compared to those with a BMI of 25;

■ Body weight less than 125 lbs (1 point) – indicating frailness;

■ Fractures after age 50 (1 point) – increase of risk with already existing fractures after the threshold age;

■ Maternal hip fracture over 50 years old (1 point) – history of hip fracture in family;

■ Smoker (1 point) – smoking is identified as osteoporosis risk factor and contributes to bone thinning.

Fracture risk interpretation

The components of the calculator are weighted differently according to their involvement in weakening bone density and in the increase of fracture outcome.

The following table provides the five year risk percentages in three different types of fractures, according to the overall score obtained after completing the form above:

Bone mineral density test (BMD T)

This test is designed to compare the subject’s bone density with normal ranges of healthy adults in the same age range. The T-score consists of the number of units, standard deviations that the subject’s score is above or below the average:

■ Normal levels are between -1 and +1;

■ Levels between -1 and -2.5 are indicative of a low bone mass;

■ Levels below -2.5 are indicative of osteoporosis.

The Z-score result is more complex and takes account of age, gender, weight and ethnical origin.

The BMD tests are usually performed by radiation (which is less than that of a chest x-ray) on bones that are more likely to undergo a fracture:

■ Lumbar vertebrae;

■ Femural neck;

■ Forearm bones.

Low bone mass is not in all cases consistent with osteoporosis as there are other factors to corroborate such as heredity, development of less optimal bone mass during youth year, bone affecting comorbidities or accelerated bone loss.

The following populations are recommended to pursue regular testing:

■ Females over 65 and males over 70;

■ People over 50 with personal history of bone fracture from minor trauma, rheumatoid arthritis or parental hip fracture;

■ People with vertebral abnormalities;

■ People suffering from hyperparathyroidism.

Risk factors for fractures

As a result of either trauma or decreased bone strength, fractures can occur more or less easier depending on underlying factors:

■ Bone strength depends on the shape, the quality and the volume of the bone while density is given by porosity and mineralization;

■ Age, gender and ethnic background are the following risk factors and although similar bone densities might mean a similar prognosis of fracture, females tend to undergo more fractures;

■ Treatment with glucocorticoids and coexistence of rheumatoid arthritis increase risk of bone trauma;

■ Smoking and high alcohol intake (above 2 units daily) lower bone quality by affecting the functioning of bone forming cells;

■ Vitamin D and calcium deficit nutrition;

■ Gait speed in the elderly also affects risk;

■ Type of trauma and force of impact affect relative risk, for example: compared to other directions of fall, falling to the side increases hip fracture risk by 6 times;

■ Sedentary lifestyle;

■ Frequent falls due to loss of balance, visual impairment, long time immobilization or dementia.

References

1) Black DM, Steinbuch M, Palermo L, Dargent-Molina P, Lindsay R, Hoseyni MS, Johnell O. (2001) An assessment tool for predicting fracture risk in postmenopausal women. Osteoporos Int; 12(7):519-28.

2) Krall EA, Dawson-Hughes B. (1994) Walking is related to bone density and rates of bone loss. Am J Med; 96(1):20-6.

3) Blake GM, Fogelman I. (2007) The role of DXA bone density scans in the diagnosis and treatment of osteoporosis. Postgrad Med J; 83(982): 509–517.

4) Unnanuntana A, Gladnick BP, Donnelly E, Lane JM. (2010) The Assessment of Fracture Risk. J Bone Joint Surg Am; 92(3): 743–753.

5) Lewiecki EM. (2013) Bone density measurement and assessment of fracture risk. Clin Obstet Gynecol. 2013 Dec; 56(4):667-76.