Osteoporosis: Clinical sciences

Osteoporosis is a metabolic bone disease characterized by low bone density, decreased bone mass, and increased risk of fracture.

Osteoporosis can be either primary or secondary. Primary osteoporosis is more common in postmenopausal patients, and it refers to bone loss that occurs with aging due to low levels of sex hormones, namely estrogen. Low estrogen levels cause increased osteoclastic activity, and since osteoclasts break down bone, this means increased bone resorption and, as a consequence, low bone density.

Secondary osteoporosis, on the other hand, occurs because of an underlying cause, typically a medical condition, like rheumatoid arthritis, or a side effect of medications like glucocorticoids, especially when used for long periods of time. Osteoporosis is typically diagnosed using a dual-energy X-ray absorptiometry or DXA scan, and sometimes a FRAX score.

Now, most patients with osteoporosis are asymptomatic, so perform a focused history and physical exam. When obtaining history, important risk factors include being postmenopausal, fracture history without major trauma, low BMI less than 20 kg/m2, osteopenia on imaging, a family history of osteoporosis or parental hip fracture, a history of smoking or excessive alcohol use, as well as medical conditions like rheumatoid arthritis, or the use of medications like long-term glucocorticoids.

Finally, regardless of risk factors, you should screen all biological females over 65, biological males over 70, and individuals who are 5 years postmenopause for osteoporosis. Additionally, physical exam findings might reveal skeletal deformities, such as kyphosis or loss of height.

Ok, now, if you suspect osteoporosis based on the patient’s risk factors and physical exam, the next step is ordering a DXA scan, which tests a patient’s bone mineral density. A DXA scan is typically performed at the hip and lumbar spine level. In patients with either known or suspected hyperparathyroidism a DXA scan of the distal third of the radius can be considered, as in these patients, bone loss tends to occur faster in the radius.

Alright, now lets look at the possible results of our DXA scan. DXA scan results are typically reported as a T-score, which is a standard deviation measure of a patient’s bone density compared to a reference population. Ok, now, a T-score greater than or equal to -1.0 is normal. In other words, there’s no osteoporosis and you can consider alternate diagnosis.

On the other hand, if the T-score is between -1.0 and -2.5, then the patient may have either osteopenia or osteoporosis, so you should use the Fracture Risk Assessment Tool to calculate a FRAX score.

The FRAX score estimates a person's 10-year risk of either a hip fracture, or a major osteoporotic fracture based on their age, sex, weight, height, and history of personal or parental fracture. It also takes into account smoking status, alcohol use, glucocorticoid use, history of rheumatoid arthritis, and bone mineral density at the femoral neck.

If the FRAX score shows that the patient’s 10-year risk is less than 3% for hip fracture, and less than 20% for major fracture, then your patient has osteopenia. If this is the case, you should encourage lifestyle modifications, such as increased dietary calcium intake, alongside vitamin D supplementation. Next, counsel your patient on smoking cessation, limiting alcohol intake, as well as weight-bearing, balance, and resistance exercises. If the patient is at increased risk of falling, you should refer them to a physical therapist.

However, if the FRAX score reveals a 10-year risk equal to or greater than 3% for hip fracture, and equal to or greater than 20% for major fracture, you can diagnose osteoporosis. Now, let’s go one step back and check the DXA scan one more time. If the T-score is -2.5 or lower, you can directly make the diagnosis of osteoporosis.